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

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.