In order to design composite structures and to improve material characteristics, impact damage on the surface and on the edge are considered. However, knowledge about the impact on the edge is limited when compared to that about the surface. In this study, edge impact tests and compressive strength tests after edge impact (CAEI) were carried out using carbon-fiber-reinforced-plastic laminates. Furthermore, CAEI failure mechanisms were investigated by measuring results using a high-speed camera and the digital image correlation method. Test results showed that the specimen with the edge impact showed about 40% lower failure load than that with no damage. According to the observation results, delamination caused by local buckling in the damage area did not seem to propagate. On the other hand, final failure occurred in the initial damage area as the starting point, and then, the in-plane failure propagated from the initial damage area to the other side in the width direction instantly. The in-plane residual strength after edge impact as well as delamination seemed to affect the final failure.

Tapering in laminated composites is introduced by terminating plies called ply drop-off. Strength reduction in such materials is caused by delamination failures and matrix cracks that occur at terminating plies. Tapering composite is generally designed based on many test results and empirical rules. The failure load and mode at ply drop-off can be changed depending on the type of material and shape, so many tests are needed for adequate design. The failure modes of various ply drop-offs were revealed and a progressive failure analysis was proposed to decrease the number of trial-and-error tests in this study. The proposed method was based on constitute damage mechanics (CDM) for inplane failure and cohesive zone modeling (CZM) for interlaminar failure. The lamina behaviors were incorporated into the versatile finite element software Abaqus with a user subroutine developed by the authors. The analysis corresponding to the tests showed that progressive failure analysis could predict the failure loads and modes.

Monitoring methods used to observe the molding process of carbon fiber-reinforced plastic (CFRP) facilitate the development of high-quality products. However, current monitoring methods provide only localized state information, and estimating the state of the entire material is difficult. This study proposes a method for estimating the overall state of CFRP during molding based on data assimilation, which integrates theoretical and experimental values. In this method, three types of specimens with different thermal conductivities were considered, and the temperatures throughout each specimen during molding were estimated by data assimilation of surface temperatures measured using thermocouples. To validate the accuracy of this method, the temperatures estimated by data assimilation were compared with those obtained using numerical simulations without data assimilation. The experimental results of all the specimens showed that data assimilation can be used to accurately estimate the surface temperature. The proposed method is therefore effective for monitoring composite molding processes.