Evaluation method of dynamic interlaminar shear strength of CFRP for higher accuracy.

Ryohei Miyake･Kazuya Miyata･Masateru Yoshizumi･Hiroyuki Ogata (JFE Techno-Research)

The double-notch compression method is preferred for evaluating interlaminar shear strength of CFRP, but the strength might be overestimated due to friction between the fixture and specimen in the case of high-speed deformation. The tensile method is not affected by frictional forces, but it usually have greater out-of-plane deformation than the compression method, resulting in keeping the deformation mechanism away from pure shear. In this work, the digital image correlation method was used to modify the geometry of the tensile specimen to deform as closer to pure shear, thereby improving the accuracy of the dynamic interlaminar shear strength evaluation method.

Crack propagation simulation for lap joints considering adhesion

Hirofumi Sugiyama･Shigenobu Okazawa (University of Yamanashi)

This paper proposes a crack propagation simulation considering adhesion using a material model and numerical techniques. Multi-material structures that combine steel and composites are essential in various engineering fields, offering light weighting, enhanced strength, and tailored material properties. Conventional numerical simulations employ multiple types of material models to account for the complex deformation behavior. A novel approach uses the damage model, eliminating mesh dependency, and employs numerical techniques to handle crack propagation. Finally, the representative numerical example shows that the novel method is verified.

Unified strength evaluation for various adhesive joints and strength improvement by adding notches

Kazuhiro Oda (Oita University)･Rei Takaki (Nippon Bunri University)･Nao-Aki Noda (Kyushu Institute of Technology)

In this study, the adhesive strength of different edge shapes is evaluated using a method that assumes an edge crack at the interface edge. By comparing the average strength of butt joints and lap joints using the proposed method, it was found that the lap joint has about five times the strength of a butt joint. In addition, the adhesive strength can be improved by providing an additional notch near the interface to reduce the singular stress field at the interface edge.

Comparison of adhesive strength of butt joint and lap joint based on the intensity of singular stress field

Rei Takaki (Nippon Bunri University)･Nao-Aki Noda (Kyushu Institute of Technology)･Yasuaki Suzuki (Suzuki Adhesion Institute of Technlogy)･Kazuhiro Oda (Oita University)

This study investigated the adhesive strength of butt joint and lap joint by ISSF analysis and elasto-plastic analysis when the bond layer dimensions are varied. The butt joint strength can always be expressed as ISSF = constant. On the other hands, In the case of lap joint, when the bonding area is large, the bond strength can be expressed as ISSF = constant. The butt joint strength is constant independent of adhesive area. In the case of lap joints, the adhesive strength decreases with increasing adhesive area.

Improvement of fracture toughness of biomass composite materials using injection molding machine with vent system

Akio Ohtani･Senri Hirata (Kyoto Institute of Technology)

In this study, direct fiber injection molding was used to improve the fracture toughness of wood-blended plastics by incorporating natural fibers. To investigate the dispersion behavior of natural fibers in resin, natural fiber spun yarn and base resin were pretreated before molding, and the effects of the pretreatment methods on dispersion and mechanical properties were evaluated.