A Computational Model for the Progressive Damage and Failure of Fiber-Reinforced Brittle-Matrix Composites

A computational model was developed to simulate the progressive damage sustained by unidirectional fiber-reinforced, brittle-matrix composites in tensile loading parallel to the fibers. In addition to the constituent and interface properties, the model used a size-distribution of ‘fiber-free zones’ as potential sites for the development of small penny-shaped cracks. Stable extension of these non-steady-state cracks and the transition from non-steady-state to steady-state were modeled using a stress-intensity formulation for a partially-bridged, penny-shaped crack. Stress-strain relation was simulated by calculating the total engineering strain in the gage section as a function of the applied stress. Strain energies of the non-steady-state cracks and displacements of the fibers in the sliding zones of the steady-state cracks were calculated separately to estimate the total strain. Two unidirectional fiber-reinforced composites were used to test the predictive capability of the model. The stress-strain relation predicted by the model was in good agreement with that measured experimentally for a SiC(fiber)-reinforced calcium aluminosilicate (CAS) composite. A SiC(fiber)-reinforced magnesium aluminosilicate (MAS) composite showed less cumulative strain before fracture due to premature fiber failure.