Unified micromechanical model for the mechanical properties of two constituent composite materials. Part V: Laminate strength

Abstract

This series of papers reports a new, general, and unified micromechanical model for estimating the three-dimensional mechanical properties of a composite made from two constituent materials, i.e., continuous fibers and matrix. Various mechanical properties, i.e., elastic, elasto-plastic, strength, and robber-elastic properties, of unidirectional laminae made using different constituent materials have been simulated in Parts I-IV. The present paper addresses the problem of failure analysis and strength prediction of laminated composites consisting of different unidirectional laminae. By using the classical laminate theory, the stress shared by each lamina ply in the laminate can be determined, and the lamina analysis theory reported previously can be applied. The progressive failure process in the laminate is treated through stiffness reduction. As soon as one ply fails, it has no further contribution to the overall instantaneous stiffness matrix of the laminate, and the total strength of the laminate corresponds to a load level at which all the plies have failed. A generalized maximum normal stress criterion, which accounts for equibiaxial and equitriaxial tensions, is used to detect the lamina tensile failure, whereas the lamina compressive failure is controlled using a criterion similar to the original maximum normal stress criterion. The present modeling procedure has been applied to four different angle-ply laminates subjected to various biaxial load conditions. Favorable correlation between predictions and available test data has been found.