Transverse crack propagation in fibre reinforced composites

Abstract

The energy absorbed in propagating a crack transversely to the direction of alignment of the reinforcing elements in a fibrous composite is dependent on the nature of the fibre/matrix interface. Weak interfaces can debond allowing a matrix crack to propagate through the composite without immediately causing fibre failure. Energy can then be absorbed in various ways by the fibres left bridging the crack until they fail sequentually as the crack propagates. When the shear strength of the interface between the reinforcing elements and the rest of the composite structure is self adjusting, so that it is controlled by the local tensile stress in the reinforcing element, failure of the reinforcing elements can be prevented whatever the magnitude of the tensile strain developed in the composite structure. Reinforcing elements of this type, therefore, remain intact over the entire length of the matrix crack so that the energy absorbed during crack propagation can increase with increasing crack length. Preliminary studies of transverse crack propagation have been made using a model system incorporating self-adjusting interfaces of this type and the results obtained are discussed.