Based on interfacial mechanics and finite element method, the paper investigates damage process and multimode failure mechanism of fiber composite. Average stress strain curves and energy release rates of the composite were calculated for different crack paths. The failure behavior of the composites was controlled by two primary microstructural parameters: interfacial fracture energy and mixture of loadings. Numerical relation curves between the overall failure properties and microstructural parameters were given. Methodology of crack path control and property optimization was suggested.