Plasticity-based modelling of fibre/matrix debonding in unidirectional composites

Of interest in this work is the elastoplastic-based modelling of fibre/matrix debonding in unidirectional fibre-reinforced composites. The modelling is embedded into the integrity-basis formulation of transverse isotropy that allows for a neat decomposition of the contributions to the mechanical behaviour into fibre-directional, transverse, and pure shear parts. This offers an appealing framework where plastic yielding is easily formulated. The criterion can be chosen to depend solely on the tension transverse to the fibres, on the in-plane shear stress along them, or on both of the above stresses. The whole formalism is easily implemented in a finite element software to build efficient predictive computational tools. The formulation is developed for fully three-dimensional problems as well as for the particular two-dimensional problems under the plane-stress assumption. The application to some examples reveals the accordance with many experimental observations found in the literature. Among others, it is found that in all cases, the predicted debonding path always propagates along the direction of the reinforcing fibres.