Modeling Multilayer Damage in Composite Laminates Under Static and Fatigue Loading

Abstract

The failure process in composite laminates under quasi-static or fatigue tensile or thermal loading involves sequential accumulation of damage in the form of matrix cracking in the off-axis plies of the laminate, matrix crack-induced local and edge delaminations, fiber-matrix debonding and fiber breakage. Accurate prediction of the laminate strength and stiffness response to damage must consider the above-mentioned damage mechanisms. In this paper, a model is developed for the analysis of cross-ply laminates, damaged by transverse and longitudinal matrix cracks and transverse and longitudinal delaminations growing along them. The model is based on the Equivalent Constraint Model (ECM) of the damaged ply and employs an improved 2-D shear lag method to determine the stress field in the damaged ply. The model is then applied to predict stiffness reduction in T300/914 cross-ply laminates using experimentally observed damage patterns under thermal fatigue loading.