Abstract: The shear-lag model1 and the geometrical local load-sharing rule2 are applied for analysis of load concentrations of bundles and fibers in the paper. Based on these studies, the statistical microscopic criteria of failure of small-bundle-(the boundary effects of bundles must be taken into account in this case) and large-bundle-reinforced composites are established by using the method of the critical crack core model1,3,4 and used for investigation of failure and fracture of bundle-reinforced composite...