Nonlinear and First-Ply Failure Analyses of Laminated Composite Cross-Ply Plates

A method is presented to study the nonlinear behaviors and first-ply failure strengths of centrally loaded laminated composite plates with semi-clamped edges. The method which is developed from the von Karman-Mindlin plate theory and the Ritz method is used to construct the nonlinear load-deflection curves of the composite plates with or without considering the reduction in plate stiffness induced by ply failure and predict the first-ply failure loads of the plates based on various commonly used strength-of-material type failure criteria. Experiments on laminated composite plates loaded to failure are performed to construct the experimental load-displacement curves of the plates. During testing, the first-ply failure loads of the plates are identified using the acoustic emission technique. The experimental results are used to investigate the capabilities of the present method in predicting the nonlinear behaviors and first-ply failure loads of the laminated composite plates. It has been found that when compared with the experimental load-deflection curves the present method with the consideration of stiffness reduction can yield reasonable results on load-deflection curve and even for some cases the ultimate strength. As for the determination of first-ply failure load, the inconsistent results predicted by the adopted failure criteria indicate that the strength-of-material approach may be inappropriate for the first-ply failure analysis of laminated composite plates. Hence, more research on failure mechanism and, especially, the development of appropriate failure criteria for composite laminates is needed.