Compressive splitting failure of composites using modified shear lag theory

The shear lag model has been used in conjunction with the 3D elasticity equations to determine the stress state in a fiber/matrix system containing an interface crack. The use of a shear lag model to capture the stress state at the crack tip and the modelling of the region away from the crack tip by the elasticity equations leads to a simple analytical expression which can be used to determine the compliance changes for both unsteady crack growth as well as steady state crack propagation under compressive loading. Certain modifications to the assumptions used in the classical shear lag model have been made to increase the accuracy of the predictions for the rate of change of compliance with respect to crack length, dc/dl. The present approach leads to closed form expressions for the compressive strength of unidirectional fiber reinforced composites.