Micromechanical Analyses on Three-Dimensional Response of Compressive Failure in Unidirectional CFRP

Significant reductions in the compressive strength of CFRP are attributed to a specific failure process, which is a combination of the compressive failure of fibers and the shear failure of the matrix. To further understand the mechanism of compressive failure, micromechanical numerical models were developed to reproduce the three-dimensional response, consisting of contraction by the compressive load and in-plane and out-of-plane shear deformation due to the rigid rotation of broken fibers. The feasibility of the model was confirmed by comparing the numerical results to theoretical results. The validated models were used to investigate the failure response under not only compressive loading but also in combination with in-plane and out-of-plane shear loadings. The variation in fiber misalignments and the strength of fibers were considered. The numerical model reproduced the trend of results from experiments in previous studies, in which the compressive strength of CFRP decreased with the increase in fiber misalignment. Moreover, the present results reveal that the ratio of in-plane and out-of-plane shear loadings is an important factor for the compressive strength and direction of shear deformation induced by compressive loading.