A numerical micromechanical method is adopted here to investigate the tensile strength of metal matrix composites (MMC) by considering interface and matrix damage evolution. A cohesive zone model is em­ployed to simulate the fiber/matrix interface damage. The damage in the matrix, which characterizes mi­crovoid nucleation, growth and coalescence, is described in term of the Gurson-Tvergaard material model. These damage models are perfom1ed to a boundary value problem that involves a double periodic array of elastic continuous fibers in the elastic-plastic matrix subjected to transverse loads. The main attempt is made to investigate effects of interface strength and toughness on tensile strength of MMC.