Computational approach to the fatigue behaviour of randomly or unidirectional fibre reinforced materials

The reinforcement of materials by means of fibres has been recognised to be a simple and effective way to enhance the mechanical properties. Usually the tensile strength, the wear resistance, the durability, the fracture and fatigue resistance are the main mechanical characteristics that can be improved by such a reinforcing technique. Therefore, fibre reinforced composite (FRC) materials are widely used in highly stressed structural applications, and suitable mechanical models are being developed. The present paper extends a previous mechanical-based homogenisation approach proposed by the authors for the mesoscopic description of fibre-reinforced materials under cycling loading, by taking into account the fatigue matrix degrading effects and fatigue fibre-matrix debonding. In particular, fatigue loading are responsible for the degradation of the fibre-matrix interface and, consequently, the reduction of the bearing capacity of such materials. By analyzing the debonding phenomenon through fracture mechanics, the detaching process can be quantified by means of classical fatigue laws. By also taking into account the degrading effects on the matrix material, a global damage parameter (d) for the composite being examined can be defined. The developed mechanical model, implemented in a FE code, is used to simulate the static and fatigue behaviour of FRC materials and the results are compared with literature data.