Tensile strength of discontinuous fibre composites-the effect of fibre/matrix interface strength

The effect of fibre/matrix interface strength on the tensile strength of the discontinuous fibre composites is studied theoretically. The equation for longitudinal stress distribution in a fibre which has perfect adhesion to the matrix is extended to the case of imperfect adhesion. The effect of fibre/matrix debonding was introduced by using an adhesion parameter, K, describing the extent of slip between the fibre and the matrix, which depended on matrix strain. Three fracture modes were assumed: (i) matrix fracture, (ii) fibre fracture, and (iii) fibre/matrix interface debond. The fracture conditions were derived theoretically. The tensile strength of composites in which fibres of various lengths are randomly distributed, are simply formulated.