On the Mechanics of Microcracking in Fiber Composite Laminates Under Combined Stress

Abstract

The formation of matrix microcracks in fiber composite laminates has been widely observed. The present paper addresses the mechanics of this microcracking by means of a shear lag model in conjunction with a Weibull failure criterion for further cracking. This shear lag model considers both shear loading as well as cross-fiber tension in the cracked ply. The reduction in inplane shear and tensile modulus of the cracked ply is computed directly from the model. The increase in applied load required to produce new cracks is computed and shows general agreement with previous experimental results. A general approximate relationship between the applied strain levels and the modulus reduction is presented.