Effect of fiber rupture on tensile properties of short fiber composites

A probabilistic-based micromechanical model has been developed for the postcracking behavior of a brittle matrix reinforced with short, randomly distributed fibers. The model that predicts the composite- bridging stress crack-opening displacement (COD) relationship, accounts for fiber pullout, fiber tensile rupture, and a local frictional effect called snubbing. However, it does not account for fiber bending rupture, and the possible effect of matrix spalling at the exit points of inclined fibers from the matrix. The model assumes a fiber/matrix interface that is controlled by a constant frictional bond stress. The model is used to predict the composite tensile strength and fracture energy. Comparisons of model-predicted bridging stress-COD relationship with experimental data, where fiber rupture has occurred, show reasonable agreement supporting the validity of the proposed model. The model is then used to perform a parametric study to evaluate the effect of the micromechanical parameters on the composite tensile strength and fracture energy. The study suggests that this model can be used to design the composite for optimum performance.