A micromechanics perspective on the intralaminar and interlaminar damage mechanisms of composite laminates considering ply orientation and loading condition

A comprehensive understanding of the complex damage mechanisms in composite laminates is of great importance for establishing material failure models and designing structural damage tolerance. This paper proposed a combined numerical computation and in-situ experimental study to comprehensively investigate the influence of ply orientation and loading conditions on the microscopic damage behaviors of composite laminates. In terms of numerical computation, to overcome the limitations of current monolayer Representative Volume Element (RVE) models, 3-D two-layer RVE models were developed to characterize the intra-ply and inter-ply damage behavior of composite laminates. In-situ tests were conducted on orthotropic laminates under transverse tensile and out-of-plane shear loads, and the physical processes of crack initiation and propagation were analyzed in conjunction with numerical simulation results. The research findings revealed the contributions of the matrix, fibers, and their interfaces to the damage behavior dominated by matrix cracking in composite laminates. The extension processes and final morphologies of matrix cracks were analyzed and a summary of the propagation patterns of matrix cracks was provided. The proposed 3-D two-layer RVE model effectively captured transient failure processes that cannot be observed in in-situ tests, and the numerical computation results were consistent with ex-situ observations after specimen failure.