A model is developed to analyze the effect of fiber fracture on the elastic properties of short fiber composites.

Tensile test specimens were prepared from 26.6 %, 12.9 % fiber Vf samples. The specimens were tested in tension to failure. Fractography and optical metallography performed in the plane of the reinforcement showed fragmentation of fibers which eventually led to overall material failure.

To model the fiber failure in an infinite matrix, the problem of crack and elliptical inclusion interaction is solved. The crack in the inclusion is formulated in terms of a distribution of dislocations. The dislocation solution is used as a Green’s function and resulting singular integral equations are solved numerically. Stress intensity factors are tabulated for both a crack inside and outside the elastic elliptical inclusion. The specific case of a completely cracked inclusion is solved.

The solution of a completely cracked inclusion is then used in a micromechanics model of the damaged composite. The energy dissipated through the opening of the crack in the inclusion is calculated and used in a self consistent method to find the overall effective moduli of the composite. The results are given for the prediction of the effective moduli, E and μ, of the 2-D composite containing cracked fibers which are randomly distributed and oriented.