A bridging model prediction of the ultimate strength of composite laminates subjected to biaxial loads

A micromechanical prediction procedure is described in this paper to simulate the progressive failure strength of a composite laminate subjected to multiaxial loading. Casting the loading in an incremental form, the stress increments exerted on each lamina in the laminate can be determined based on the instantaneous stiffness matrix of the lamina. A recently developed micromechanics model, the bridging model, is used to define this instantaneous stiffness matrix and to relate the stress increments in the constituent fiber and rein materials of the lamina with those stress increments exerted on it. The thermal residual stresses generated in the constituents due to mismatch between coefficients of thermal expansion in the fiber and resin materials are clearly addressed and have been incorporated in the analysis. As long as one of the constituents attains its ultimate stress state, the lamina is considered to have failed and its contribution to the overall stiffness matrix of the laminate is reduced. A total reduction strategy is employed in the paper. In this way, the progressive failure process in the laminate can be understood, and the corresponding failure mode can be identified automatically. A generalized maximum normal stress criterion is adopted to detect the constituent failure. The prediction procedure has been applied to 14 different composite laminates where failure envelopes or stress–strain curves up to final failure subjected to biaxial loading are required. The predicted results have been reported in figures and data tables.