Strength prediction of triaxially loaded composites using a progressive damage model based on micromechanics of failure

Abstract

The research presented in this article is a continuation of the authors' work in Part A of the second world-wide failure exercise (WWFE-II). In Part A, a constituent damage model based on micromechanics of failure was employed in order to predict the failure envelopes and stress-strain curves for unidirectional and laminated composites under multi-axial loadings. In this study, original predictions were compared with experimental data, supplied in Part B of the second world-wide failure exercise. Three modifications were made to the previous model: (a) a quadratic fiber failure criterion was proposed to replace the maximum longitudinal stress failure criterion used for fibers in the original model; (b) a three-dimensional kinking model was introduced so as to take into account the influence of the formation of kinking bands on micro stresses in the matrix, when a ply is under longitudinal compression; and (c) in-plane shear terms in stress amplification factors were averaged to avoid overestimation of local stress concentration for regions within the matrix and in the vicinity of the fiber-matrix interface. Questions regarding the discrepancies between the idealized and actual tests were also raised and are discussed in this study.