PREDICTION OF THE TENSION-SOFTENING RELATION FOR SHORT-FIBER-REINFORCED SMC COMPOSITES BY A PROBABILISTIC MODEL

A new probabilistic model has been proposed to predict the tension-softening relation for short-fiber-reinforced SMC composites by using the measured debond and pull-out lengths of fiber bundles. The relationship between cohesive stress and crack opening displacement, namely the tension-softening relation, is determined statistically by the probabilistic expectation of loads acting on the bridging fiber bundles at a fictitious crack. It is found that the area below the tension-softening curve is nearly equal to the apparent fracture energy of the composite, while the maximum value of the tension-softening curve is somewhat higher than the unnotched tensile strength of the composite. Comparison of the tension-softening relation with that estimated by a technique based on the J-integral is also made. Furthermore, the influences of fiber bundle-matrix interfacial conditions on the tension-softening relation are clarified.