Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.ndteint.2024.103202

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DOI： 10.69361/agorajams.paper24003

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DOI： 10.69361/agorajams.paper24002

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DOI： 10.69361/agorajams.paper24001

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2024.2325725

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2023.2293603

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.compstruct.2023.117467

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DOI： 10.1016/j.compositesa.2023.107934

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.cjmeam.2023.100074

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jcomc.2022.100260

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2022.2080989

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.compstruct.2022.115458

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2022.2055514

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2022.2035303

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.cjmeam.2022.100016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Scientific Research Publishing, Inc.  

DOI： 10.4236/ojcm.2022.124009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jcomc.2021.100187

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jcomc.2021.100195

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2021.1930497

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.compstruct.2021.113815

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2021.1882163

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.compositesa.2020.106244

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DOI： 10.1016/j.compstruct.2020.112956

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2020.1848314

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jcomc.2020.100056

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.compositesa.2020.105985

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Publishing type：Research paper (scientific journal)  

DOI： 10.1080/09243046.2019.1682794

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.compstruct.2019.111714

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DOI： 10.1016/j.compscitech.2019.107905

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2019.1650323

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Composite Materials  

<p>Owing to the superior mechanical properties and moldability of carbon fiber reinforced thermoplastics (CFRTP), they have been increasingly adopted in various applications. Injection molding is a typical method for fabricating CFRTP, however, this method requires a mold, and hence it is difficult to use this method to fabricate complex geometries. Meanwhile, 3D printing is suitable for fabricating complex geometries and for optimizing the structure. Recent advancements in 3D printing technology have enabled printing of composite materials that have arbitrarily curved continuous reinforcements. Previous studies have revealed that a fiber bundle becomes twisted in a curved section, and this might affect the mechanical properties of 3D printed CFRTP. In the present study, the mechanism of twisting a fiber bundle in a 3D printed CFRTP is investigated. In addition, fiber fracture in a curved section is evaluated by measuring the electrical resistance of a fiber bundle. As a result, it has become clear that the twisting of a fiber bundle is caused by the flattening of the fiber bundle, the adhesive force on the print bed, and tensile load from the print nozzle. Moreover, the electrical resistance measurements verified the fracture of fibers in a curved section.</p>

DOI： 10.6089/jscm.45.149

CiNii Books

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publisher：The Imaging Society of Japan  

<p>Carbon fiber reinforced thermoplastic (CFRTP) is a composite material with mechanical anisotropy when continuous fiber is used as the reinforcement material. In 3D printing of the CFRTP, moving path of a nozzle (print path) is coincides with fiber direction in the 3D printed CFRTP. Optimized print path is obtained based on the stress distribution determined from the 3D printed shape and the loading condition in use. Mechanical property of the 3D printed part is maximized by using the optimized print path. It is, therefore, important to consider 4D printing since manufacturing of shape (3D) with print path optimization (1D) are required. In this paper, some examples of 3D printing of CFRTP reported by the authors are explained.</p>

DOI： 10.11370/isj.58.415

CiNii Books

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Language：Japanese   Publisher：The Japan Society for Composite Materials  

<p>Continuous carbon fiber composites can be printed with 3D printers. Many studies detailing elucidations of the mechanical properties of such 3D printed composites have been published, all of which employed a conventional tensile specimen configuration with surface resin layers. In the present study, 0º, 90º, ±45º, and lay-up direction type specimens were newly designed for 3D printed composites without surface layers. Using the 3D printer, both conventional and newly designed specimens with serpentine folded fiber bundles were fabricated and investigated experimentally. The lay-up direction specimen was fabricated using 800 layers. The specimens without the serpentine folded fiber bundles were experimentally shown to be adequate for tensile tests. The lay-up direction specimen had the lowest strength and stiffness, which seems to be related to its surface roughness.</p>

DOI： 10.6089/jscm.45.141

CiNii Books

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Language：Japanese   Publisher：The Japan Society for Composite Materials  

<p>Continuum damage mechanics (CDM)-based finite element analysis was performed to predict the mechanical behavior of a 3D-printed curvilinear continuous carbon fiber reinforced thermoplastic (c-CFRTP). Elasto-plastic properties of the 3D-printed c-CFRTP, including its damage initiation, evolution, and propagation, were identified by conducting monotonic and cyclic tensile tests on three specimens (i.e., [(±45)₂]_S, [(0/90)₂]_S, and [(±67.5)₂]_S). Then, an S-shaped curvilinear c-CFRTP was 3D-printed and tested under monotonic tensile loading conditions. The non-linear mechanical behavior of the S-shaped curvilinear c-CFRTP due to tensile loading was well predicted by means of finite element analysis using the constructed CDM-based material model.</p>

DOI： 10.6089/jscm.45.155

CiNii Books

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Language：Japanese   Publisher：The Japan Society for Composite Materials  

<p>Three-dimensional (3D) printing is a promising technology that can produce complex structures without the requirements of expensive tools and molds. Additives are usually incorporated into the plastic materials used in 3D printing to increase their strength and rigidity. Particularly, carbon fiber-reinforced plastic (CFRP) has shown great promise as a 3D printing material. However, the strength of CFRP after printing remains unknown, although it is well-known that its strength is affected by plastic melting during printing. Herein, we analyzed the fracture behavior of CFRP specimens before and after bending to different curvature radii. From the experimental results, a fracture criterion describing the material behavior by considering the tensile and compressive loads was developed. The fracture mechanism remained the same for CFRP specimens with different curvature radii. This study deepened our understanding of the mechanical properties of CFRP materials used in 3D printing.</p>

DOI： 10.6089/jscm.45.164

CiNii Books

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2018.1558327

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DOI： 10.1016/j.addma.2018.09.019

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DOI： 10.1016/j.addma.2018.10.033

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DOI： 10.1016/j.compositesa.2018.07.029

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Society of Materials Science Japan  

DOI： 10.2472/jsms.67.888

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

File： Effect of dents in laminated carbon composite beams.pdf

DOI： 10.1016/j.compstruct.2018.05.154

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.compstruct.2018.03.089

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/09243046.2018.1470894

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

DOI： 10.1109/JSEN.2017.2773558

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Publishing type：Research paper (international conference proceedings)  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemp.2018.26.219

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File： Doublet analysis of changes in electric potential.pdf

DOI： 10.1016/j.compstruct.2017.05.019

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DOI： 10.1016/j.compstruct.2017.04.014

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File： Analysis of electric current density.pdf

DOI： 10.1016/j.compstruct.2016.12.055

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ndteint.2016.10.002

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DOI： 10.1016/j.compstruct.2016.10.020

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DOI： 10.1080/09243046.2016.1239354

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/09243046.2015.1126665

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DOI： 10.1016/j.compositesa.2016.07.008

J-GLOBAL

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Scientific Research Publishing  

Scientific Research Publishing

DOI： 10.4236/ojcm.2016.64012

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3144/expresspolymlett.2016.80

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.6089/jscm.42.98

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.compositesa.2015.11.040

J-GLOBAL

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/srep23058

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.compositesb.2015.09.041

J-GLOBAL

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DOI： 10.1016/j.compscitech.2015.11.018

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/09243046.2014.985420

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/09243046.2015.1087176

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>CFRP is known to its high specific strength and stiffness, and widely applied in many fields. However, because of its orthotropic mechanical properties, fiber orientation have to be considered in the design process. In addition, recently a new manufacturing method 3D printing of CFRP have developed. Which enabled to place carbon fiber filament curvilinearly. Thereby degree of freedom for design is outstandingly increased. Consequently, there is possibility of products, which have higher fracture strength than conventional one by controlling orthotropic properties in a ply. Thus in present paper, optimization of in-plane curvilinear fiber placement for the 3D printing and discussion of the manufacturability was conducted. As a result strength was significantly improved in terms of Tsai-Wu failure criteria after the optimization, and placement of the CFRP filament for the 3D printing was obtained</p>

DOI： 10.1299/jsmemm.2016.OS12-18

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Publishing type：Research paper (international conference proceedings)  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Carbon fiber reinforced polymers (CFRPs) have high specific strength and many other advantages in mechanical properties compared with conventional metal materials. However, a small out-of-plane impact load can easily cause serious damage in a CFRP laminate because of its laminated structure composed of anisotropic layers. Although ultrasonic inspection is generally performed to detect the damage and estimate its location and size, the method usually requires both long inspection time and a large cost. Thus, a low-cost and in-situ system for monitoring collisions of foreign matters is required to identify the area where the ultrasonic inspection must be conducted. When a foreign matter, which is regarded as a charged body because any object is charged to a greater or lesser extent, approaches and hits grounded electric conductive materials such as a CFRP laminate, an electric current caused by electrostatic induction flows into the ground. We analyzed the electric current and conducted a falling-weight impact test to elucidate the mechanism of generation of the electric current. In addition, we proposed a collision monitoring system which utilizes the characteristic waveform of the electric current and the electrical anisotropy of a CFRP laminate, and conducted a falling-weight impact test to verify the validity of the proposed method. As a result, we succeeded in localizing the collision of the charged body in sufficiently high spatial resolution using the proposed system.</p>

DOI： 10.1299/transjsme.16-00237

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Language：Japanese   Publisher：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

Carbon fiber reinforced plastics (CFRPs) are generally used for weight reduction of industrial structures. Highly strong reinforced plastics and highly rigid matrixes in CFRP consist CFRP&prime;s high performance (e.g. specific strength and rigidity), while CFRP can be defected inside (e.g. deferent material interface or interlaminar) by off-plate directional impact load easily to reduce their strength significantly. Therefore, periodical non-destructive testing (NDT) is required for maintenance of their integrity. In addition, CFRP has remarkable mechanical and electrical anisotropy; especially electrical resistances are approximately 1000 times different between longitudinal and orthogonal direction. In this study, we propose new thermography method for CFRP delamination detection with electrical resistance heating of intentionally selected layer by using above-mentioned CFRP&prime;s electrical resistance anisotropy (selective-layer heating). This method can detect the delamination crack induced in an objective more deeply than the other thermography method that excite heat from an objective surface and can determine the delamination depth more precisely by excluding influence of 3-dimensional heat conduction than the other thermography method.

DOI： 10.6089/jscm.42.185

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>The purpose of this study is to manufacture carbon fiber reinforced thermoplastic composites for aerospace and automotive applications. In order to accomplish this purpose, we produced carbon fiber pre-impregnated resin filament for FDM 3D printer. Moreover, we developed an FDM 3D printer that incorporates a mechanism to amputate continuous carbon fibers. We conducted a tensile test and bending test of an acrylonitrile butadiene styrene (ABS) specimen and a carbon fiber reinforced thermoplastic (CFRTP) specimen to evaluate dynamic characteristics of CFRTP shaped by FDM 3D printer. As a result, the tensile strength and modulus of longitudinal elasticity of the CFRTP specimen were found to be 4 and 4.8 times higher than those of the ABS specimen, respectively. The bending strength and bending modulus of longitudinal elasticity of the CFRTP specimen were found to be 2.9 and 5.1 times higher than those of the ABS specimen, respectively. We conducted cross-sectional observation of CFRTP specimen wherein resin-rich and resin non-impregnated spheres were observed. However, these values were lower than the theoretical values calculated from the law of mixtures. By examining the evidence, lower dynamic characteristics were concluded to result from the presence of the aforementioned spheres.</p>

DOI： 10.1299/jsmemp.2016.24.107

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DOI： 10.1016/j.compstruct.2015.07.028

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DOI： 10.11395/jjsem.15.200

J-GLOBAL

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DOI： 10.1016/j.compstruct.2015.04.020

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DOI： 10.1016/j.ndteint.2015.05.009

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DOI： 10.1007/s10921-015-0298-4

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DOI： 10.1016/j.ndteint.2015.04.005

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DOI： 10.1016/j.ijadhadh.2015.03.003

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DOI： 10.1080/09243046.2015.1052132

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DOI： 10.1016/j.compositesa.2015.01.031

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DOI： 10.1016/j.compscitech.2014.12.013

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DOI： 10.1016/j.compositesa.2014.11.014

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1117/12.2083823

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Language：Japanese   Publisher：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

One of the authors has already proposed the method to analyze electric current density of carbon fiber reinforced plastics (CFRP) laminates using the anisotropic electric potential function. The effectiveness of the method was verified by comparisons with FEM analyses. The method is based on the assumption that CFRP laminates are homogeneous orthotropic materials. Actual CFRP laminates are, however, heterogeneous materials: the actual CFRP has resin rich layers and carbon fiber layers. In the present study, an electric conductance is calculated on the assumption that CFRP laminates are homogeneous by using an electric resistance measured by a four-probe method, and the measured values are used for an electric current analysis. To investigate electric current distribution of CFRP laminates experimentally, a newly designed specimen is proposed. The results of an electric current tell us that the analysis method gives us the accurate result of electric current density of actual CFRP laminates. This shows that the assumption that CFRP laminates are homogeneous orthotropic material in case of electric current analysis was verified experimentally.

DOI： 10.6089/jscm.41.55

CiNii Books

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Other Link： https://jlc.jst.go.jp/DN/JLC/20008820042?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.compositesa.2014.08.010

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DOI： 10.1016/j.ndteint.2014.04.007

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DOI： 10.1080/09243046.2013.851357

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/transjsme.2014smm0084

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DOI： 10.1016/j.ijadhadh.2014.01.034

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DOI： 10.1016/j.compositesb.2013.10.047

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DOI： 10.1080/09243046.2013.844900

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DOI： 10.1080/09243046.2013.832829

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DOI： 10.1016/j.compscitech.2013.11.029

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Society of Materials Science Japan  

DOI： 10.2472/jsms.63.331

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Language：Japanese   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

In Super Sonic Transport (SST), thin wing structure is necessary to satisfy the high speed, economic viability and environmental compatibility requirements. Among many structures in thin wing, the lug structure which is between the body and the main wing plays important role. However, it is difficult to design of the lug structure because it is subjected many loads that have uncertainties such as magnitude or direction of loading caused by aeroelastic forces. Robust topology optimization is, therefore, necessary to determine the optimal structural lay out solutions insensitive to loading uncertainties for design of the lug structure. The present paper proposes robust topology optimization using NSGA-IIa algorithm which is one of the most popular in Multi-Objective Evolutionary Algorithms (MOEA) with multiload formulation. In proposed method, Monte Carlo simulations were used to estimate the robustness of topology from Pareto optima obtained with NSGA-IIa. The obtained robust topology solutions are explored by Self-Organizing Map that is an appropriate tool to visualize and explore properties of the high dimension data. Finally, proposed method approach is applied for the lug structure robust topology optimization.

DOI： 10.2322/jjsass.62.1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

High-temperature water stress corrosion cracking has high tensile stress sensitivity, and its growth rate has been evaluated using the stress intensity factor, which is a linear fracture mechanics parameter. Stress corrosion cracking mainly occurs and propagates around welded metals or heat-affected zones. These regions have complex residual stress distributions and yield strength distributions because of input heat effects. The authors previously reported that the stress intensity factor becomes inapplicable when steep residual stress distributions or yield strength distributions occur along the crack propagation path, because small-scale yielding conditions deviate around those distributions. Here, when the stress intensity factor is modified by considering these distributions, the modified stress intensity factor may be used for crack growth evaluation for large-scale yielding. The authors previously proposed a modified stress intensity factor incorporating the stress distribution or yield strength distribution in front of the crack using the rate of change of stress intensity factor and yield strength. However, the applicable range of modified stress intensity factor for large-scale yielding was not clarified. In this study, the range was analytically investigated by comparison with the J-integral solution. A three-point bending specimen with parallel surface crack was adopted as the analytical model and the stress intensity factor, modified stress intensity factor and equivalent stress intensity factor derived from the J-integral were calculated and compared under large-scale yielding conditions. The modified stress intensity was closer to the equivalent stress intensity factor when compared with the stress intensity factor. If deviation from the J-integral solution is acceptable up to 2%, the modified stress intensity factor is applicable up to 30% of the J-integral limit, while the stress intensity factor is applicable up to 10%. These results showed that the modified stress intensity factor can be applied even when the yielding scale exceeds the small-scale yielding criterion.

DOI： 10.1299/mej.2014smm0009

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DOI： 10.4236/ojcm.2014.41003

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The stress intensity factor can be applied as an evaluation parameter of crack growth under small-scale yielding conditions. Moreover, the stress intensity factor corrected by the plastic zone correction can potentially be used as an evaluation parameter of crack growth for small-scale yielding criteria or beyond these criteria. In the previous study, the plastic zone correction method for that purpose was proposed. The method focuses on the gradient of the stress intensity factor at the crack tip, incorporating the term into the correction formula. To investigate the applicability of the correction experimentally, fatigue crack propagation tests were conducted in this study using three types of specimens with different gradients. The results show that the crack growth rate increased when the gradient was large although the effective stress intensity factor range was the same. This indicates that the gradient of the stress intensity factor at the crack tip affects the stress state in the vicinity of the crack tip and the crack growth rate increases as the gradient increases. When the correction of the stress intensity factor was applied, the crack growth rate could be evaluated independently from the gradient of the stress intensity factor. The correction is applicable around small-scale yielding criteria or beyond these criteria, but is not applicable under sufficiently large-scale yielding conditions.

DOI： 10.1299/transjsme.2014smm0194

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5139/IJASS.2013.14.4.350

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DOI： 10.5139/IJASS.2013.14.324

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DOI： 10.1016/j.engfracmech.2013.07.019

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DOI： 10.1080/09243046.2013.801822

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DOI： 10.1080/09243046.2013.805502

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Language：Japanese   Publisher：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

Although an electrical-resistance-change method is useful for monitoring delamination cracking of Carbon Fiber Reinforced Plastics (CFRP) laminates, the method requires a lot of experiments or FEM analyses to obtain relationship between the electrical resistance changes and delamination cracking. In the previous studies, the author proposed the anisotropic electric potential function to analyze electric current density of CFRP laminates. The function was applied to thick CFRP laminates. In the present study, the method is expanded to thin CFRP laminates using an image method. The number of images is determined using the electric current analysis of thick CFRP laminates here. Electric potential changes caused by delamination cracking can be calculated using anisotropic doublet line. The anisotropic doublet method is applied here to calculate the electric voltage change at the surface of a thin CFRP laminate and the results are compared with FEM analysis. As a result, the method is shown to be very effective.

DOI： 10.6089/jscm.39.106

CiNii Books

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Other Link： https://jlc.jst.go.jp/DN/JALC/10019418154?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijadhadh.2013.01.008

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DOI： 10.3144/expresspolymlett.2013.26

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DOI： 10.1016/j.compositesa.2012.09.014

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Language：Japanese   Publisher：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

When an alternating current is applied to a conductive slab, the induced current impedes the electric current and this causes skin effect for all conductive materials. For laminated Carbon Fiber Reinforced Plastics (CFRP), however, the skin-effect depth is not evaluated. In the present study, therefore, Maxwell's equations are analytically solved, and the skin-effect depth of unidirectional CFRP is derived first. Using the result, skin-effect is analyzed for the laminated CFRP. As a result, the skin-effect depth is derived for the laminated CFRP, and the effect is compared with the newly defined skin-effect of direct current caused by strong anisotropic conductance. For the highly toughened CFRP that has resin rich layers, the skin-effect of the direct current is more important than that of alternating current.

DOI： 10.6089/jscm.39.10

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Other Link： https://jlc.jst.go.jp/DN/JALC/10017951363?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5139/IJASS.2013.14.2.146

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Self-sensing Carbon Fiber Reinforced Plastics (CFRP) is one of the attractive multifunctional composites. That multifunctional composite has structural strength/stiffness and sensing function using electrical resistance changes. For the self-sensing, electrical contact between the lead wire and the carbon fibers is the most important issue. The present study focuses on the effect of the long term cyclic loading of lower applied strain range than the fatigue damage initiation level. Cyclic loading tests of the lower applied strain range are performed in the present study with measuring electrical resistance changes. The temperature change compensation method is proposed here for the long term tests. As a result, the electrical contact resistance at the copper electrode increased with the increase of cycles. That means the electrical change at the electrodes must be considered for the long-term self-sensing monitoring system. Moreover, angle-ply laminates has plastic deformation caused by shear loading, and that causes electrical resistance decrease during the cyclic loading.

DOI： 10.1299/kikaia.79.1009

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Authorship：Lead author   Language：Japanese   Publisher：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

A new electrical potential method is proposed in the present study. Many electrodes to measure electric voltage are mounted on a carbon-fiber-reinforced-polymer beam surface. Direct current is applied and the electric voltage changes are measured at the electrodes. Comparing the measured results with the analytical results obtained from the anisotropic electric potential function, electric conductance ratio is obtained. Using the obtained electric conductance ratio, difference of the electric voltages at the surface is amplified. The difference of the electric potential enables us to know the delamination location and dimension. Uniform doublet analysis enables us to know the relationship between the measured results and the delamination location and dimension. The method is applied to numerical analyses here. The results show that the new method is quite effective for simple delamination monitoring.

DOI： 10.6089/jscm.39.135

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Other Link： https://jlc.jst.go.jp/DN/JALC/10021892188?from=CiNii

Publishing type：Research paper (scientific journal)  

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DOI： 10.1016/j.engfracmech.2012.08.011

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

In recent years, there has been a renewal of interest in the study of supersonic transport (SST). The high speed, economic viability and environmental compatibility are required for the future SST. So, the wing of SST has to be thin as possible in order to minimize the weight and enhance performances. For this reason, the design of lugs between the main wing and body is very important. In structural optimization of lug, topology optimization has been used to determine the optimal structural lay-out. However, topology optimization has the problem that there are several different solutions depending on the analysis data and multiple loads caused by aeroelastic forces on the wing. In this study, in order to search for an optimal solution from topology optimized solutions for several loads, these solutions are classified according to the topological characteristics by using Self-Organizing Map (SOM). In this case, topological characteristics were represented by using model's spatial densities of topology optimized solutions. Through this classification, it is possible to explore to the optimal topology optimized solution within various topology optimized solutions.

DOI： 10.2322/jjsass.60.189

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Other Link： https://jlc.jst.go.jp/DN/JALC/10010181866?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)  

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DOI： 10.1016/j.compositesa.2011.12.024

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DOI： 10.1016/j.compositesa.2011.09.003

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DOI： 10.1080/09243046.2012.743716

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

This study is an analytical investigation of time domain reflectometry (TDR) for carbon fiber reinforced polymer (CFRP) composites using numerical simulation software. This process is called self-sensing TDR because the carbon fibers themselves are used as the sensors. A previous study conducted experimental investigations of this process using parallel aluminum plates. This study uses finite difference time domain analysis for simulations of a transmission line structure for the self-sensing TDR. Details of the effects of the orthotropic electric conductance are investigated analytically. The simulation results show that the electromagnetic waves propagate rapidly in the transverse direction and that the effects of the orthotropic conductance seem to be negligible. An additional simulation using a pair of square CFRP plates reveals that the electromagnetic wave is affected by the orthotropic conductance. The effect is nevertheless very small when compared with the actual ratio of the electric conductance between the fiber direction and the transverse direction.

DOI： 10.1299/jmmp.6.1062

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

Laminated CFRP structures are applied to many aerospace structures. Although CFRP laminates have high specific strength and specific stiffness, an impact load easily creates damage such as delamination cracking, matrix cracking, and fiber breakage. Damage to laminated CFRP is usually difficult to detect by visual inspection. As a result, damage monitoring systems are required for large laminated CFRP structures. Many researchers have already proposed self-sensing monitoring systems which measure electrical resistance changes in the laminated CFRP. This method, however, requires a lot of electrodes. In the present study, a new time domain reflectometry (TDR) method using an electrical pulse signal and reinforcement carbon fiber sensors is adopted as a monitoring method. The method is applied to a 2-m long CFRP strip plate specimen to detect an ideal damage mechanical notch using a reflected pulse signal. In addition, the effect of the orthotropic conductance of the CFRP plate is experimentally investigated using multiple electrodes, and is shown to be negligible.

DOI： 10.1299/jmmp.6.1053

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

Quick and automatic inspection of carbon fiber reinforced polymer (CFRP) aircraft after each flight would reduce the safety factor and allow for more flights. Visualization of impact damage was developed in an earlier study as an automatic self-monitoring method. The damaged area was visualized by selective and intense resistive heating based on its decreased through-thickness resistivity compared to undamaged areas. In the present study, the lightning protection system of a composite aircraft was used to apply a uniform electrical current distribution and electric heat to a large structure. Subsequent coupled thermal-electrical analyses showed that even small indentations (depth <0.15 mm) could be relatively easily detected in structures about 1 m in size.

DOI： 10.1299/jmmp.6.213

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

From a traffic safety point of view, there is an urgent need for intelligent tires which can optimize braking control by estimating the slip ratio and friction coefficient between a road surface and an automobile tire. The present study develops concurrent monitoring of frictional and vertical loads applied to the tires from the inner tire strain data for estimating the road/tire friction coefficient, which enables optimization of vehicle control and implementation of a road condition warning system. The tire strain is obtained using a three-dimensional digital image correlation method with a single wireless CCD camera attached to the wheel rim inside the tire. The procedures of the applied load estimation decompose the measured strain into the frictional and vertical strain components using their symmetrical and anti-symmetrical characteristics. Static tire rotation tests were carried out, and the applied loads were estimated from the inner tire surface strain distribution. Compared with the actual applied loads measured from strain gages attached to the experimental apparatus, it was confirmed that the vertical and frictional loads can be estimated independently with adequate accuracy.

DOI： 10.1299/jmmp.6.935

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1515/SECM.2011.045

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DOI： 10.1007/s11465-011-0231-1

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DOI： 10.1016/j.compositesa.2011.03.004

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DOI： 10.1016/j.compositesa.2011.01.014

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DOI： 10.2322/jjsass.59.132

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Publisher：The Japan Society of Mechanical Engineers  

The previous study employs delamination detection in CFRP laminates using statistical analysis of temperature characteristic of resistance to prevent electrical resistance changes caused by damages of electrical contact at electrodes. A statistical analysis method discriminates the temperature characteristic of resistance of the damaged structure from that of the intact structure. To detect delaminations without learning processes, a new method which compares the electrical resistances at high temperature with those at low temperature is developed here. The new method has applicability to existing structures and can also detect initial defects. The present study employs the new method for detecting delaminations and initial defects in quasi-isotropic-plied CFRP plates. The detection limit of delamination and the effectiveness of detecting initial defects are experimentally investigated, and the effect of electrode damage on the diagnosis is discussed here.

DOI： 10.1299/kikaia.77.181

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

A new method for detecting delamination cracks in carbon fiber reinforced polymer (CFRP) laminates using changes in electrical resistance was developed in a previous study. It was possible to detect delamination cracks without sampling the data from intact structures and to prevent false diagnoses from changes in electrical resistance caused by damage to the electrical contacts at the electrodes. As a result of the study, delamination of at least 5.3 mm in diameter caused by a quasi-static load in a quasi-isotropic-plied CFRP plate was detectable without sampling the data from intact structures. However, the proposed diagnostic method has not yet been experimentally performed for detecting delaminations subjected to impact loads. Although it is unfortunate that there is not much difference between damage of FRP laminates subjected to low-speed impacts and those subjected to quasi-static loads, broken fibers in the surface layer and plastic deformation such as a dent accompanied by delamination might depend on the rate of strain. It is also necessary to ensure that the diagnostic method provides correct diagnoses even if impact damage of electrical contact occurs at the electrodes. The diagnosis was not affected by chipped electrodes except for through chips. The present study employs the diagnostic method for delamination cracks and damage to electrical contacts of an electrode subjected to falling weight impact loads and dents from quasi-static loads.

DOI： 10.1299/jmmp.5.33

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DOI： 10.2322/jjsass.59.252

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.compositesa.2010.06.008

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

Many researchers adopt electrical resistance change (ERC) methods to detect damage in Carbon Fiber Reinforced Plastic (CFRP) laminates. They usually apply the method under tensile or bending loads. For compression tests, a block type specimen is used. The block type specimen, however, is too thick to obtain a uniform electrical current. This study starts with the design of a compression test specimen with uniform electrical current using a sandwich beam specimen. The four-point bending tests revealed that the piezoresistivity of the compression tests was the same as that of the tension tests. Using a three-point bending test, fiber-micro-buckling was obtained, which caused an increase in electrical resistance with residual compression strain. Non-linear behaviors observed during cyclic loading tests were investigated, and it was revealed that the plastic deformation at the loading point had large effect.

DOI： 10.1299/jmmp.4.864

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

The bolted joint is a common assembling method for carbon fiber reinforced plastic (CFRP) members. However, cracks or plastic deformation can occur around bolt holes of CFRP members even when employing low fastening forces. As a result, CFRP failure occurs around bolt holes because of bearing forces, and the strength of a CFRP joint is reduced. To address this problem, we change the configurations of washers and insert a thin sheet having a high friction coefficient between CFRP members. In friction coefficient measurements, the insertion of sandpaper was found to be the most suitable method for increasing friction forces at the interface between CFRP members. Three-dimensional finite element method analyses were conducted to investigate the effect of washer configurations in terms of the maximum allowable fastening force and the joint strength. From these analyses, the cone washer was found to be the most effective design for increasing the joint strength. In the full model analyses, the failure strengths of proposed CFRP bolted joints were higher than those of normal CFRP bolted joints. The verification tests for the proposed joint were conducted according to ASTM D5961. It was observed that the load at failure for the proposed bolted joint was about 45 % greater than that for the conventional joint.

DOI： 10.1299/jmmp.4.711

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DOI： 10.1299/jee.5.15

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaia.76.961

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

This paper deals with the mechanism of electrical resistance change observed after delamination cracking of a thick Carbon Fiber Reinforced Polymer (CFRP) laminate. In a previous paper, the current shut-off caused by the delamination crack increased the electrical resistance for a thin laminate, and the effect of piezoresistance caused by the residual strain relief was small compared with the shut-off effect. For the thick CFRP, a dent is made because of the high indentation compression load at the loading point. The present paper measures the effect of the dent experimentally and estimates the electrical resistance increases caused by the shut-off effect and piezoresistance effect using Finite Element Method (FEM) analyses. The estimates are compared with the experimental results of the thick CFRP laminate. As a result, it is established that the effect of the dent (which causes a decrease of electrical resistance) is larger than the effect of the shut-off (which causes an increase of electrical resistance) for the thick CFRP laminate.

DOI： 10.1299/jmmp.4.658

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

This paper is about improvement of diagnostic accuracy of the damage identification applying the generalized linear mixed model to the inverse problem. Generalized linear mixed model (GLMM) is the extend method of the linear regression analysis include the random effect. By the method, relation between the dependent variable and the independent variables are divided to fixed effect and random effect. The fixed effect means true relation and the random effect means the unknown fluctuation because of the individual specificity. When the damage diagnosis conducted by the inverse problem, this unknown fluctuation is caused by not only the difference of the lot of test piece, but also the unknown parameters of the damage. For example, for the damage size identification problem, location of the damage is the unknown parameter. This unknown parameter is unknown at the time of damage identification but this unknown parameter is known at the time of constructing the model of the inverse problem and the time of deciding the parameter for the inverse problem model. Then in this research, improvement of diagnostic accuracy of the damage identification using inverse problem via the GLMM is conducted. The method is applied to the delamination identification via electric potential method of CFRP laminate. FEM analyses are conducted to obtain electric potential changes due to delamination crack creations with seven-electrode type specimens. By comparisons of the estimations without the random effect and with the effect, a better diagnostic tool is discussed in detail. As a result, GLMM improve the diagnostic accuracy of size and location identification of the delamination crack.

DOI： 10.1299/kikaia.76.1040

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

This paper considers a detailed mechanism of the electrical resistance change observed after delamination cracking of a thin Carbon Fiber Reinforced Polymer (CFRP) laminate. For this laminate, the electrical resistance increases after delamination cracking, although the electrical resistance decreases after delamination cracking of a thick CFRP laminate. One of the proposed reasons for this difference is the residual strain relief caused by the delamination cracking. We report experimental and FEM analyses to investigate the effect of shut-off of the current path caused by delamination cracking, and the effect of piezoresistance caused by residual strain relief after delamination cracking. Residual strain relief was measured experimentally, and the results compared to the FEM results. On the basis of the FEM results the effect of the piezoresistance was estimated. It was found that the effect of the piezoresistance is small compared to the effect of the current shut-off for the thin CFRP laminate.

DOI： 10.1299/jmmp.4.1

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1163/092430410X490446

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DOI： 10.4028/www.scientific.net/AMR.123-125.963

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This article presents the analysis of functionally graded hollow circular cylinders with finite length under axisymmetric dynamic loads. It is assumed that the functionally graded cylinder is comprised of metal-phase and ceramic-phase whereas material properties are graded in the thickness direction of the cylinder according to power law distribution. Two-dimensional finite element method in conjunction with the Newmark method is used to solve the system of time-dependent coupled equations that govern the dynamic responses. By introducing especial elements, it is possible to distribute the material properties through the thickness of cylinder exactly according to the power law distribution. Dynamic loads applied on the cylinder are axisymmetric in the hoop direction and can vary in the radial and axial directions. As examples, the transient responses of functionally graded cylinders which are excited in radial direction by increasingly and suddenly internal pressure and line load are calculated, and the characteristics of waves are discussed. The results in the present study are obtained for thick cylinder and cylindrical shell and compared with the results for isotropic cylinders.

DOI： 10.1299/jmmp.4.1223

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

In this paper, an analytical method is presented to investigate dynamic characteristics in a functionally graded thick hollow cylinder under thermal shock loading. Thermo-mechanical properties of functionally graded (FG) thick hollow cylinder are assumed to be temperature independent and vary continuously in the radial direction. Dynamic thermo-elastic equation of the problem is analytically solved by employing the Laplace transform and series solution. The dynamic thermo-elastic stresses in a functionally graded thick hollow cylinder subjected to axisymmetric thermal shock loading are obtained and presented in closed forms at Laplace domain. The results are obtained in time domain using the fast Laplace inverse transform method. The dynamic behaviors of thermo-elastic stresses are illustrated and discussed for various grading patterns of thermo-mechanical properties in several points across the thickness of FG cylinder and cylinder thickness parameter. The presented analytical method furnishes a ground to study the time histories of radial and hoop stresses in FG cylinders with different thickness and various exponents of volume fraction. The presented results show good agreement with published data in previous literatures.

DOI： 10.1299/jmmp.4.1346

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Surface modification by nanoimprint lithography (NIL) is applied to an adherend of the bonded composite joints. We developed a silicon mold with micro scale structures by photolithography and anisotropic etching. By forming CFRP on the mold with microstructures, the microstructures are transferred to the CFRP surface. Since this surface modification can be conducted during the curing of composites, it reduces the time required and costs involved in conventional surface preparation such as sand blasting, chemical etching etc. In this paper, the effect of microstructure size on the mode I fracture toughness was investigated. A size ratio A was defined and DCB tests about some values of A was conducted. As a result, it was confirmed that as A increased, fracture toughness became stronger.

DOI： 10.1299/jsmemecjo.2010.8.0_5

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Resin transfer molding (RTM) is one of the widely used composite manufacturing techniques. During resin impregnation into fiber, entrapped air in a part (void) is undesirable defect. Presence of void depresses composites mechanical properties. In this paper, a model of bundle scale void generation is presented as a function of resin velocity and experiment was carried to validate the model on anisotropic fiber. The result was compared with the expectation of the model and good agreement was obtained between them.

DOI： 10.1299/jsmemecjo.2010.1.0_361

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In the previous study, unsupervised detection of delamination cracks in CFRP plates using statistical analysis of temperature characteristic of resistance were developed to prevent electrical resistance changes caused by damages of electrical contact at electrodes. Delamination cracks change temperature characteristic of resistance of CFRP laminates. To detect delaminations without learning processes, electrical resistances of multiple segments of a CFRP laminate at high temperature are compared with those at low temperature and a statistical analysis method discriminates the change. Electrical resistance changes caused by damages of electrical contact at electrodes do not affect the temperature characteristic of resistance. This method has applicability to existing structures and can also detect initial defects. As a result of the previous study, delamination at least 5.3 mm in diameter subjected to a quasi-static load in a quasi-isotropic-plied CFRP plate was detectable without intact data. The diagnosis was not affected by damages of electrical contact at electrodes except for perforated lack of an electrode. The present study employs the unsupervised detection method of delamination cracks and damages of electrical contact at an electrode subjected to falling weight impact loads, and dents subjected to quasi-static loads.

DOI： 10.1299/jsmemecjo.2010.6.0_299

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

It is important to expand knowledge for low-cycle fatigue properties of pre-strained nuclear component materials and nondestructive inspection (NDI) techniques for fatigue damage detection when considering resumption of nuclear power plant subjected seismic load. As acoustic emission (AE) monitoring can be applied during fatigue test and operation of plants, we conducted AE monitoring during low-cycle fatigue test. The AE monitoring results showed that reduction of fatigue life by applied high pre-strain was caused by shorten of fatigue crack initiation life. The result also showed that the possibility to use AE monitoring for online monitoring of fatigue damage detection.

DOI： 10.1299/jsmemecjo.2010.1.0_151

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In order to improve interfacial properties of adhesively bonded composites, surface modification using Nanoimprint lithography (NIL) is investigated. Since the interfacial properties such as bonded strength or fracture toughness are highly depend on a surface morphology, these properties can be improved by designing and fabricating microstructures appropriately in the interface. Considering this fact, we introduced NIL technique to the curing process of composites and fabricated microstructures on the surface of composites, which gives us stiff interface without any surface preparation such as sand blasting or chemical etching. We simulated the behavior of crack propagation along the interface with Finite element method using cohesive zone model and estimated mode I apparent fracture toughness of adhesive joints.

DOI： 10.1299/jsmemecjo.2010.8.0_3

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DOI： 10.1117/12.815403

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

One of the major fastening methods for the CFRP members used in aircrafts is bolted joint. CFRP bolted joints, although, have the problem that damages are occurred around bolt holes of CFRP, even by the tightening with low fastening force. As a result, the fastening force of conventional CFRP bolted joints is very low, and these strengths become decreased. In order to improve this weakness, configurations of the washers are changed in this study to increase the fastening force without CFRP damage, and thin sheet with high friction coefficient is sandwiched between CFRP members in this study to improve the friction force. In the validation testing, the failure strength of the proposal CFRP bolted joint become higher than normal CFRP bolted joints.

DOI： 10.1299/jsmemecjo.2009.6.0_369

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Intelligent tires are equipped with sensors to monitor strain, rolling radius and pressure of tire, and are expected to improve the reliability of tires and determine the road condition. However, the high stiffness of an attached sensor like a strain gauge causes debonding of sensors from tire rubber. In the present study, an optical method is used for the concurrent monitoring of in-plane strain and out-of-plane displacement (rolling radius) utilizing the non-planar surface of the monitoring object. The optical method enables noncontact measurement of strain. The in-plane strain and out-of-plane displacement are calculated by using image processing with an image of the interior surface of tire that is taken with a single camera fixed in tire. This new monitoring system is applied to commercial tire. As a result, the monitoring system is effective against concurrent monitoring of strain rolling radius. In addition, this monitoring system enables tire pressure monitoring.

DOI： 10.1299/jsmemecjo.2009.6.0_375

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this research, surface modification using Nanoimprint lithography (NIL) is conducted to an adherend of the bonded joint. We developed a mold by photolithography and formed composites on the mold. Since this surface modification can be conducted within the curing time of composites, it reduces the processing cost and time, which was required for conventional surface preparation such as sand blasting or chemical etching. In this paper, experimental results of tensile test for the butt joint are reported. This paper also includes numerical analysis of the butt joint strength. We found out that pyramid-shape microstructures on the CFRP surface could improve the joint strength because peel stress was reduced by the slope of pyramid-shape microstructures.

DOI： 10.1299/jsmemecjo.2009.8.0_189

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This study examined the applicability of acoustic emission testing (AT) for the impact damage evaluation of CFRP pressure vessels. AE signals were detected during pressurization tests of CFRP pressure vessels before and after an impact test. The impact test of 15-J energy was conducted by using a drop-weight impact tester. Before the impact test, a few AE signals were detected during the pressurization test. After the impact test, however, a large number of AE signals were detected during the pressurization test. From these results, it is assumed that AT can be used for the impact damage evaluation of CFRP pressure vessels. In addition, the dominant frequencies of AE signals were changed after the impact test. So there is a possibility that impact damage could be also detected by analyzing the frequency of AE signals.

DOI： 10.1299/jsmemecjo.2009.6.0_433

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The present study employs the delamination detection in CFRP laminates using electrical resistance changes. Although the method detects the delamination without expensive sensors, the electrical resistance changes only due to electrode's damage make a wrong diagnosis. A delamination detection using statistical analysis of temperature characteristic of resistance changes is developed. CFRP laminates are heated up by applying electric currents through the electrodes mounted on the surface of the structure. When the delamination occurs, the electrical resistance change due to elevated temperature becomes different from that of the other intact parts. A statistical analysis method detects the change. The electrical resistance changes due to electrode's damage don't affect the temperature characteristic of resistance. The present study employs the new method for the delamination detection of cross-plied CFRP beams. In this study, the method is applied for quasi-isotropic CFRP plates. The detection limit of the method is investigated, and the effect of electrode's damage on the diagnosis is discussed.

DOI： 10.1299/jsmemecjo.2009.6.0_361

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In this paper, artificial lightning strike tests for Cup Stucked Carbon Nanofiber (CNF) dispersed CFRP are performed to investigate the applicability for lightning protection systems. The result of visual inspection and NDT shows that the size and thickness of internal damage comprise of delamination and matrix cracks are affected by changing of CNF content, though the surface damage of fiber damaged area and resin deterioration area are hardly affected. Furthermore, in order to investigate the characteristic of residual compression strength, compression test for damaged laminate were performed in conformity with SACMA CAI test standard. As a result, it is confirmed that the residual compression strength are improved with increasing of the CNF content.

DOI： 10.1299/jsmemecjo.2008.1.0_279

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DOI： 10.1117/12.775693

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DOI： 10.1117/12.775936

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Carbon fiber reinforced plastic (CFRP) laminates are very sensitive to an impact which causes delaminations in the laminate. Since delamination reduces the mechanical property of the laminate, nondestructive inspection is required to maintain the structural reliability of the CFRP structure. Eddy current test (ECT) has been studied to be applied to CFRP laminate. Strong electric anisotropy, however, makes application of the method difficult. Since delamination is in-plane damage in the laminate, conventional ECT has a problem for making current-loop which should be impeded by the damage to be detected. In the present paper, rectangular twin probe for electrically anisotropic CFRP laminate is introduced to resolve the problems. The probe is made of two rectangular coils put side-by-side to induce strong uniform electric current. Delamination was made in CFRP cross-ply laminates by means of the indentation test; the applicability of the ECT with rectangular twin probe is examined experimentally.

DOI： 10.1299/jsmemecjo.2008.1.0_345

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From a traffic safety point-of-view, there is an urgent need for intelligent tires equipped with strain sensors as a warning system for road conditions and for optimized braking control on poor road surfaces. However, since a conventional foil strain gage has high stiffness, it causes the analyzed region to behave unnaturally. The present study proposes a novel rubber-based strain sensor fabricated using photolithography. The rubber base has the same mechanical properties as the tire surface; thereby the sensor does not interfere with the tire deformation and can accurately monitor the behavior of the tire. This investigation details the design and manufacture of the rubber-based sensor.

DOI： 10.1299/jsmemecjo.2008.6.0_355

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Swiss Federal Laboratories for Materials Science and Technology (Empa)  

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DOI： 10.2472/jsms.56.426

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1117/12.715572

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Measurement of strain of tires in-service is effective to improve reliability of tires and ABS system. Since conventional strain gages have high stiffness and require lead wires, the conventional strain gages are cumbersome for the strain measurement of the tires. The backgrounds require a new low cost wireless sensor for tires. In the present study, a new flexible patch-type strain sensor utilizing electric capacitance change is proposed and analytically investigated. The sensor is made from flexible polyimide substrates and ultra-flexible epoxy resin, which makes the sensor low in stiffness and high in elongation as a whole structure. The sensor utilizes capacitance changes due to the applied strain. The sensor is applied to an automobile tire, and compression tests are performed.

DOI： 10.1299/jsmemecjo.2007.6.0_229

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.compscitech.2005.11.029

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/0964-1726/15/4/N01

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1117/12.658294

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmezairiki.2006.0_197

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Measurement of strain of tires in-service is effective to improve reliability of tires and ABS system. Since conventional strain gages have high stiffness and require lead wires, the conventional strain gages are cumbersome for the strain measurement of the tires. The backgrounds require a new low cost wireless sensor for tires. In the present study, a new flexible patch-type strain sensor utilizing electric capacitance change is proposed and analytically investigated. The sensor is made from flexible polyimid substrates and flexible epoxy resin whose elogation is 150%. The sensor has quite low stiffness and applicability to large deformation. The capacitance change of the sensor due to applied strain is investigated using FEM analysis. As a result, the sensor is analytically proved to be effective for the strain monitoring of tires.

DOI： 10.1299/jsmemecjo.2006.1.0_875

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Detection of damages for composites is a difficult task for visual inspections. The difficulty of detections causes the importance of development of smart structures for monitoring damages of graphite/epoxy laminated composites. In our previous study, the applicability of the damage identification using an electrical resistance change method for laminates has been confirmed. Making procedure of electrode is important in adopting the electrical resistance change method for practical structures. Silver paste electrode used in the previous study had, however, low adhesion strength and complex making procedure. In the present study, we focused on the electrical copper plating. Twelve electrodes made by electrical copper plating are mounted on the quasi-isotropic CFRP thick plates surface, and the electrical resistance changes are measured using a conventional strain gage amplifier. Furthermore, adhesion strength of electrode was measured. As a result, efficiency of electrical copper plating electrode was confirmed experimentally.

DOI： 10.1299/jsmemecjo.2005.6.0_151

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This research is about a statistical diagnostic method for the structural health monitoring which is applicable to existing structures from the present moment, In this method, structural condition is statistically diagnosed by the change of the response surface. The response surface is a regression model of sensor's outputs. The change of the response surface is statistically tested with the F-test. In the F-test, a threshold of normal or fault condition is simply investigated with a theoretical F-probabihty distribution. Therefore, this diagnostic method only requires data of intact condition and does not require the complicated modeling and information of fault condition. To confirm the effectiveness of the presented method, the health monitoring of jet fans is conducted, In this study, load cells are mounted to a supporting system of the jet fan. The response surface is calculated from time-series load data measured by the load cells. As a result, the structural condition of the jet fan is successfully diagnosed.

DOI： 10.1299/jsmemecjo.2005.6.0_169

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DOI： 10.1177/1475921705049757

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmezairiki.2005.0_349

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本複合材料学会  

日本複合材料学会

DOI： 10.6089/jscm.30.149

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Other Link： https://jlc.jst.go.jp/DN/JALC/00241322602?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)  

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DOI： 10.1163/156855103322986592

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Language：Japanese   Publisher：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

DOI： 10.6089/jscm.29.48

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Other Link： https://jlc.jst.go.jp/DN/JALC/00353770377?from=CiNii

Language：English   Publishing type：Research paper (international conference proceedings)  

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The present research proposes a new damage diagnostic method for the structural health monitoring that does not require data of damaged state. Structural health monitoring are a noticeable technology for civil structures. Multiple damage diagnostic method for structural health monitoring has been proposed, but most of them demand data of structure of damaged state and measurement of these data demands much cost. That causes importance of development of the method, which diagnoses damage just from data of the intact state structure. Therefore we purpose new statistical diagnostic method for structural damage detection. In the present method, system identification using a response surface is performed and damage is diagnosed by testing the change of this identified system by statistical test. The new statistic diagnostic method requires data of damaged state structure. As an example, the present study deals structural health monitoring of a jet-fan which installed to a tunnel on an expressway as a ventilator fan. Damages are detected from a change of a set of data measured on tumbuckles of the jet-fan. As a result, the damage of the jet-fan is successfully diagnosed with the method, automatically.

DOI： 10.1299/jsmemecjo.2003.6.0_99

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaia.69.231

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The present paper proposes a new diagnostic tool for the structural health monitoring that employs a statistical diagnosis of self-learning method using a system identification and statistical similarity test of the identified systems using F-test. Structural health monitoring is a noticeable technology for advanced composite structures and civil structures. Most of the structural health monitoring systems adopt parametric method based on modeling or non-parametric method such as artificial neural networks. The former method required modeling of each structures and latter method requires data for the training. And these modeling and data for the training demands much costs. The new statistic diagnosis method does not require the complicated modeling and a learning data of damaged structure for the artificial neural networks. The present study deals monitoring of delamination of composite beam using change of strain judged by the statistical tools such as Response Surface and F-Statistic. Response surfaces among the measured strain data of surface of composite beam are produced at intact state and monitoring state, and the difference of the each response surfaces are statistically tested using F-test. As a result, the new method successfully diagnoses the damage without using modeling and a learning data of damaged structure.

DOI： 10.1299/jsmemecjo.2002.6.0_213

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DOI： 10.1299/kikaia.67.1242

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaia.67.1929

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaia.67.1242

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

DOI： 10.1016/S1359-8368(97)00030-9

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A system for designing the stacking sequence of a laminated plate by using an object-oriented programming system was presented in this paper. In this system, not only stiffness of a laminated plate but also its strength was considered simultanuously based on a normalized objective function for optimization. The system uses two optimization methods. One is called the sequential decision process and the other the branch and bound process. These two methods were tested and compared. As a result, the sequential decision process was found to be excellent for an actual design process. However, large variation of the stacking number with small variation of applied load was observed in the sequential decision process. To avoid this, a new approach was proposed and shown to be excellent.

DOI： 10.1299/kikaia.61.1044

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Other Link： https://jlc.jst.go.jp/DN/JALC/00032979817?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JSME  

DOI： 10.1299/jsmea1993.38.4_524

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JSME  

DOI： 10.1299/jsmea1993.38.4_458

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DOI： 10.1299/jsmea1993.38.4_446

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DOI： 10.2472/jsms.43.434

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Measuring elastic properties of thin film on substrates is important in the analysis of residual stresses of advanced 3D LSI. In this study, an approach to for nondestructive measurement of the elastic properties of thin film on the substrate nondestructively with a scanning acoustic microscope is proposed. The approach was analyzed mathematically and was applied to aluminum film on glass substrates. As a result, this approach was proved to be excellent for the objective, and the elastic modulus of aluminum film on the glass substrate was 10% smaller than that of the bulk data.

DOI： 10.1299/kikaia.59.2977

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Other Link： http://sucra.saitama-u.ac.jp/modules/xoonips/detail.php?id=A3000149

Language：English   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Nondestructive measurements of residual stresses were successfully attempted by the acoustoelastic technique on butt-welded joints of a piping carbon steel plate. Based on the measurements and evaluations of the residual stresses, the prediction of the fatigue crack growth was done using the superposition technique, and results 'were compared with the experiments. The measurement of the initial residual stress distribution on the specimen before the fatigue test and the application of a proposed evaluation method of the material anisotropy can give a more correct prediction, The sensitivity of possible errors in the acoustoelastie measurement was analyzed and discussed.

DOI： 10.1299/kikaia.55.902

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Other Link： https://jlc.jst.go.jp/DN/JALC/00224883335?from=CiNii

Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaia.54.30

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaia.54.205

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

An acoustoelastic technique using ultrasonic was applied to nondestructive measurements of welding residual stress. Redistributions of the residual stresses in weld joint CT specimens were measured by the acoustoelastic and strain gauge techniques in fatigue crack growth tests. The redistributions of the residual stresses due to saw-cuts were also measured. The acoustoelastic technique is able to successfully measure the redistributions of the residual stresses. The validity of the principle of superposition is confirmed by the measurements of the redistributions of the residual stresses.

DOI： 10.1299/kikaia.53.1574

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Other Link： https://jlc.jst.go.jp/DN/JALC/00215914871?from=CiNii

Publishing type：Research paper (scientific journal)   Publisher：Society of Materials Science, Japan  

DOI： 10.2472/jsms.35.401

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Total pages：382p   Language：Japanese  

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Language：Japanese   Publisher：強化プラスチック協会  

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Language：Japanese   Publisher：技術情報協会  

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Language：Japanese   Publisher：日刊工業出版プロダクション ; 1955-  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Fiber waviness is a deformation of fibers in carbon fiber reinforced plastics (CFRPs), and is one of the process-induced defects that occur in molding of CFRPs. Because fiber waviness causes significant degradation of compressive strength of CFRP structures, nondestructive technique for waviness detection is in great demand. In this study, eddy current-based nondestructive technique for detection of in-plane fiber waviness in CFRPs is developed. Authors newly propose a test probe specialized for detection of in-plane fiber waviness in cross-ply CFRP. The proposed probe is sensitive to in-plane deformation of eddy current paths, can select inspected layers and the output signal is insensitive to lift-off. We carried out measurement on 20 layer cross-ply laminate with artificially induced in-plane waviness. It was found that the probe can detect waviness up to 18 layers away from the surface of cross-ply CFRP. The minimum size of the detected subsurface waviness has an amplitude of 1.4 mm and a length of 10.5 mm.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Carbon fiber reinforced polymer (CFRP) laminates have been getting adopted as structural components for aircrafts due to their high mechanical performances. For the purpose of the evaluation of damage caused by a lightning strike, electric current analysis for CFRP laminates is indispensable. The authors have already proposed the analysis method using orthotropic electric potential function, which is applicable to the large structure that cannot be dealt with by general numerical methods such as FEM and FDM. In the case of unidirectional and cross-ply CFRP laminates, the effectiveness of this method has already been shown. The actual CFRP structures, however, have 45°, -45° carbon fiber plies in many cases. The present study proposes the improved method which can be applicable to the laminates having 45°, -45° plies. The effectiveness of this method was shown through the comparison with a numerical method.

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Language：English   Publisher：Scientific Research Publishing  

A study was conducted to evaluate the current production capabilities of the Mark One(R) 3D printer in printing carbon fibre reinforced thermoplastic (CFRTP) tensile test specimens according to the JIS K 7073 by making use of fused deposition modelling. Several different types of CFRTP tensile test specimens are printed and are tensile tested in the longitudinal direction to obtain an overview of the mechanical properties of 3D printed CFRTP material. These properties are compared with the literature values known for composite materials to see if these agree. The main goal of this research is to increase the knowledge of the 3D printing process of CFRTP and to later use this knowledge to further improve the 3D printing process to obtain stronger 3D printed CFRTP materials.Physical characteristics: Original contains color illustrations

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Language：English   Publisher：Scientific Research Publishing Inc.  

A study was conducted to evaluate the current production capabilities of the Mark One(R) 3D printer in printing carbon fibre reinforced thermoplastic (CFRTP) tensile test specimens according to the JIS K 7073 by making use of fused deposition modelling. Several different types of CFRTP tensile test specimens are printed and are tensile tested in the longitudinal direction to obtain an overview of the mechanical properties of 3D printed CFRTP material. These properties are compared with the literature values known for composite materials to see if these agree. The main goal of this research is to increase the knowledge of the 3D printing process of CFRTP and to later use this knowledge to further improve the 3D printing process to obtain stronger 3D printed CFRTP materials.

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Language：English  

DOI： 10.1080/09243046.2015.1032502

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

Acoustic Emission Testing (AT) is one of the non-destructive testing methods which are widely used in engineering fields. Final goal of monitoring AE phenomena is to estimate characteristics of AE sources and to provide beneficial information to prevent fatal fracture. It is know that b-value is not changed by propagation length from the AE sources to AE sensors. Although, the effects of the frequency dependence on AE attenuation to b-value is not discussed in details by any researcher. In this research, we conducted the simulation with two conditions. First condition assumes AE source contains single frequency of 45 or 65 kHz, and the other condition assumes the source composed of 25 kHz, 45 kHz and 65 kHz. As a results, b-value is changed by propagation length when assuming AE sources with multiple frequencies. The cause of changing b-value is due to non-linear behavior of AE attenuation.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

For the structural integrity assessment of the sandwich structural leaf spring installed on the rolling stock bogie "efWING", Electrical Resistance Change Method using the electrical conductivity of carbon fiber has been studied. In the present study, electrical resistance change of fatigue-loaded test coupons is experimentally measured and an inner damage is captured by ultrasonic testing. The relationship between electrical resistance and an inner damage is analytically investigated using FE analysis. As a result, the study shows the electrode producing a high current density in through-thickness direction is effective to detect an inner damage.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper introduces "Tapping AE method" which is a new NDT method for CFRP. CFRP has a large number of advantages, although, internal damage easily occurs in it when impact load is applied. The typical NDT method to detect internal damages of CFRP are ultrasonic testing and tap testing. Although UT is reliable method for its high detectability, UT is a time and cost consuming method. On the other hand, tapping method is a quick and easy way to conduct, although, the detectability of the method is insufficient for main component materials. The aim of developing tapping AE method is realizing high-detectability tap testing. In Tapping AE method, the specimen is tapped by a hammer and secondary AE emitted from the damages are measured by AE sensor installed in the hammer during the hammer tapping. In order to evaluate feasibility of tapping AE method, we developed tapping AE system. The test was applied to a cross-ply CFRP laminate with and without internal damages. During the test, secondary AE signals were successfully observed.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper introduces a new technique to reconstruct Lamb wave ultrasonic tomography with manual transmitter scanning. By this technique, ultrasonic tomographic image can be obtained using only 4 receivers and 1 transmitter without a scanner or an encoder. The image is reconstructed by determining the transmitter position (x,y) by source location method and estimating an existence of defects between the transmitter and the receivers from amplitude-ratio of Ao mode to So mode of lamb wave. Lamb wave tomographic image was successfully reconstructed for an Aluminum plate with artificial defects by proposed method.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A new meshfree numerical analysis, termed the seamless domain method (SDM), is applied in a multiscale technology. The SDM requires only a small number of points and does not require a stiffness equation, mesh, grid, cell, or element. The SDM consists of two analyses. The first is a microscopic analysis of local simulated domain to obtain shape functions for interpolation of dependent-variable distributions and influence coefficients for calculation of interaction between the points. These allow an SDM solution to represent a heterogeneous material without homogenization. The second step is a macroscopic analysis of a seamless global domain without mesh or grid. Various numerical examples illustrated that the method worked out both steady temperature fields and linear elastic fields. All the SDM solutions using only a few hundreds of points were as accurate as those from traditional finite-element analysis using more than two hundred thousands of nodes.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In 3D printing technology, fused deposition modeling (FDM) is used with continuous carbon fiber reinforced thermoplastic (CFRTP). In this study, polylactic acid (PLA) was used as the matrix material and continuous carbon fiber was used as the reinforcement material. A method was adopted for in-site fiber impregnation of PLA filaments in a continuous carbon fiber bundle that are separately supplied and then mixed in a heater before ejection. A dumbbell-shaped CFRTP specimen was made using the developed 3D printer for a tensile test. The tensile test results showed that the continuous fiber reinforcement improved the tensile stiffness and strength. However, the tensile properties were slightly less than those expected by the rule of mixtures. Observation of the fracture surface showed insufficient impregnation and some gaps between filaments, which reduced the improvement in the tensile properties of the CFRTP.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The present study investigated crack visualization in metallic structures using Kriging model and time-domain reflectometry (TDR) with microstrip line (MSL). Because TDR can scan large-scale structures very quickly, it is suited for an initial inspection of the entire structure. However, because it only detects the damage beneath the transmission line, the reliability of the estimation between sensor lines is low. We used a Kriging model to visualize the uncertainty of the estimated damage location from time domain reflectometry (TDR) measurements. We integrated the estimation and uncertainty contour maps into a single figure for easier understanding and statistical quantification. We used the measured TDR data to investigate three types of visualization models for damage inspection: hue-saturation-intensity color, crack existence probability, and expected improvement. All three methods quantitatively visualize the estimated crack configuration with uncertainty in a single figure.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Carbon Fiber Reinforced Polymers (CFRPs) are becoming widespread for their high specific strength and many other advantages. However, a small out-of-plane impact load can easily cause internal defects in CFRP plates. Although ultrasonic inspection scheme is generally used to find and estimate location and size of defects, the method usually requires both long inspection time and a large cost. Accordingly, a low-cost and in-situ monitoring system for impact load is required to assure safety of CFRP components. When applying an impact load to electric conductive materials such as a CFRP plate, an electric current flows in the plate. We conducted impact tests and finite element analyses to elucidate the mechanism of electric current generation by electrostatic induction when the charged impactor approaches the plate. In addition, we proposed a system made of a CFRP plate to identify the impact location of charged impactor from measured electric current.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper introduces a new real-time image ultrasound technique for thin-wall structure in which the scanning of the ultrasound transmitter is carried out by hand. By this technique, we can get the ultrasound-image without a scanner or an encoder, and test a thin-wall structure faster than by ultrasonic pulse-echo method. Existence or nonexistence of defects is estimated by monitoring the amplitude-ratio of A_0 mode to S_0 mode of lamb wave between the ultrasound transmitter and the receiver. In addition, the image is constructed by determining the transmitter position (x,y) by source location method. The damaged image was successfully constructed for a thinning made on Aluminum plate by proposed method.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The present study investigated crack visualization in metallic structures using time-domain reflectometry (TDR) with differential circuit of microstrip line (MSL). It was problematic that single ended of two-dimensional (2D) MSL was affected by the cross talk voltage because of the interference of adjacent MSL. Differential circuit enables to suppress the cross talk voltage by taking the difference. Crack visualization experiments were conducted using the proposed TDR with differential circuit of 2D MSL for different crack lengths. The experimental results demonstrated that crack propagation could be clearly visualized by determining the appropriate threshold. To observe the time change of the electric field, the electromagnetic fields of the differential circuit was numerically simulated using the finite-difference time-domain method. The simulation results clarified that the cross talk voltage decreased, because the electric field of the differential circuit caused by interference of adjacent MSL was in phase. It agreed with the experimental results.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The present study investigated crack visualization in metallic structures using time-domain reflectometry (TDR) with differential circuit of microstrip line (MSL). It was problematic that single ended of two-dimensional (2D) MSL was affected by the cross talk voltage because of the interference of adjacent MSL. Differential circuit enables to suppress the cross talk voltage by taking the difference. Crack visualization experiments were conducted using the proposed TDR with differential circuit of 2D MSL for different crack lengths. The experimental results demonstrated that crack propagation could be clearly visualized by determining the appropriate threshold. To observe the time change of the electric field, the electromagnetic fields of the differential circuit was numerically simulated using the finite-difference time-domain method. The simulation results clarified that the cross talk voltage decreased, because the electric field of the differential circuit caused by interference of adjacent MSL was in phase and obtained the visualization result like the experiment.

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J-GLOBAL

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

There is a possibility that the crack growth rate of stress corrosion cracking and fatigue crack depend on the value of ∂K/∂a (differential term of stress intensity factor) as well as stress intensity factor K. In this study, the effect of ∂K/∂a on crack growth rate was investigated during the fatigue test. Two types of specimens were prepared. One is CT specimen of which K increases under constant loading. The other is CDCB specimen of which K is constant. The effect of ∂K/∂a was clarified by comparing the CT specimen and CDCB specimen under same stress intensity factor. In addition, ΔK corrections considering ∂K/∂a were conducted for CT specimens. As a result, the crack growth rates in CT specimens were larger than CDCB specimens in the same ΔK. Corrected ΔK considering ∂K/∂a is mostly coincides with the value of the CDCB specimen. From those results, the crack growth rate varied due to the effect of ∂K/∂a in fatigue crack propagation was experimentally clarified. In addition, elimination of the influence of ∂K/∂a is possible by ΔK correction.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In recent years, thermoplastic CFRP attracts considerable attention especially in aviation and automobile industries due to weldability of thermoplastic CFRP. Ultrasonic testing (UT) is commonly adopted as a testing method for inspecting weld parts although time and cost on UT is thought to be problematic. Since eddy current testing (ET) is used for rapid and non-contact inspection on electrically conductive materials, this paper presents an eddy current based approach for detecting defects in thermoplastic CFRP welded zones. However, it is difficult for conventional ET to detect delamination which is parallel to eddy current although delamination is one of the common forms of weld defect. To detect delamination in thermoplastic CFRP welded zones, new eddy current based approach which utilizes temperature characteristic of electrical conductivity is proposed. The proposal consists of two steps. Firstly, temperature difference between intact zones and defective zones is caused by heating the one side of the weld part. Secondly, the temperature difference is detected by ET utilizing temperature dependency of electrical conductivity.

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