A progressive damage model for unidirectional fibre-reinforced composites based on fibre fragmentation. Part I: Formulation

Constitutive damage models for fibre-reinforced composite materials should take into account the occurrence of the different damage mechanisms, their interaction and their influence on the resulting mechanical properties. Fibre breakage has usually been considered in damage models by means of deterministic failure criteria which thus leads to non-progressive behaviour or to a complete material collapse which is not realistic. This work presents a progressive damage model for fibre-reinforced composites based on the fragmentation analysis of the fibres. The stiffness loss of a unidirectional composite comes from the parameters of the Weibull distribution of the fibre strength and the mechanical properties of the fibre, matrix and the interface. The model has been developed for the initial stages of damage. The model is formulated in the framework of the mechanics of the continuous media. The constitutive model can be employed to simulate the contribution of fibres in damage models based on the rule of mixtures.