To propose a test method for evaluating the filled hole compressive (FHC) property of laminated carbon fiber reinforced plastics (CFRPs), compression tests were conducted that simultaneously recorded stress-strain and recorded high speed photographic images. The effects of “clearance ratio,” which is defined as the ratio between the diameters of the metal inserting pin and specimen hole, was experimentally investigated. Despite exhibiting similar final fracture appearances, specimens with different clearance ratios demonstrated distinct fracture processes. These differences were captured through synchronized high-speed photography and stress-strain evaluation. The strain distribution and local fracture behavior varied significantly with clearance ratio. Based on these findings, a appropriate strain gage location was proposed for evaluating the FHC fracture behavior.

The in-plane and out-of-plane shear moduli (G₁₂ and G₂₃, respectively) of carbon fiber-reinforced plastics (CFRP) require specialized fixtures and setups for measurement due to their anisotropy. In this study, two approaches were employed to evaluate these shear moduli. A finite element analysis was first conducted to determine the optimal specimen geometries for the pure shear test. Subsequently, pure shear tests were performed to determine G₁₂ of the CFRP. However, this method cannot be used to calculate G₂₃ because of the low stiffness and strength of the specimen, in which the fibers were oriented out-of-plane relative to the specimen surface. Therefore, tensile tests were conducted using 90° laminated plates, and the digital image correlation method was employed to evaluate G₂₃. Finally, the obtained results were validated by comparing with the reference data, and good agreement was observed between them.

Carbon fiber-reinforced plastics (CFRP) possess excellent mechanical properties; however, out-of-plane impacts on CFRP laminates can induce delamination, transverse cracking, and other internal damage that are not detectable through visual inspection. Such damages significantly decrease the residual and fatigue strengths of the CFRP laminates. Consequently, understanding the post-impact fatigue behavior of CFRP is essential for ensuring and improving the long-term reliability of CFRP structural components subjected to repeated loading. In this study, impact tests using an N2-gas gun and subsequent tensile fatigue tests were performed on CFRP cross-ply laminates to evaluate the progression of delamination under cyclic loading. A fatigue damage extension model was developed to simulate delamination propagation, and finite element analysis was conducted on a specimen model incorporating impact-induced damage to examine the post-impact damage evolution. The study clarifies the damage development mechanisms of CFRP laminates under cyclic loading following impact.