Constitutive model for imperfectly bonded fibre-reinforced composites

A constitutive model for fibre-reinforced composites has been developed that takes imperfect fibre/matrix interfacial bonding into account. The model can predict the nonlinear material response of a composite in the large strain regime. Independent constitutive laws can be used for the constituents behaving elastic or elastic-plastic. A constitutive equation is derived for the composite moduli relating stresses to strains. The model is used to predict the development of the compressive failure; fibre kinking that is either formed by bifurcation or due to an initial fibre imperfection. A three-dimensional finite element model for kink band formation is used to validate the results obtained using the constitutive model with varying levels of interfacial bonding.