Shear versus dilatational damage mechanisms in the compressive failure of fibre-reinforced composites

Abstract

Abstract Experiments are described that lead to the conclusion that there appears to exist a shear-damage controlled upper limit to the compressive strength of fibre-reinforced ceramics. At low strain rates, hydrostatic confinement increases strength by suppressing dilational microfracture until the failure mechanism transforms to shear via microkink band formation. However, this mechanism saturates at a finite level. At higher strain rates, the unconfined strength is observed to reach this confined state through the rate dependence of the kinking process alone. On the other hand, the application of confinement in the high strain rate range cannot push the strength beyond the shear-controlled ceiling. In related experiments, the pressure-strain rate dependence of the compressive flow strength of the matrices of several polymeric composites were determined. At low rates, strength was found to increase with confinement, as has been noted by previous investigators. However, high strain rate compressive strength was inversely proportional to confining pressure.