A FRACTURE MECHANICS-BASED MICROMECHANICAL MODEL FOR FATIGUE BEHAVIOUR OF FIBRE-REINFORCED COMPOSITES

Composite materials are widely used in engineering applications due to their remarkable mechanical properties, such as significant strength, elastic modulus, fatigue strength and fatigue damage tolerance. They consist of two or more constituents combined at a macroscopic level, and their classification is usually based on the kind of matrix material (polymers, metals, ceramics) and reinforcing phase (fibres, particles, flakes). Among them, fibre-reinforced composites (FRCs) are often used for their fabrication simplicity and affordable costs. Typical damage phenomena leading to a significant loss of the mechanical performance are: matrix cracking, fibre-matrix debonding, fibre breaking, fibre instabilities. In particular, matrix cracking and fibre-matrix debonding are crucial for the proper assessment of in-service safety and the optimal design of such a class of materials. In this work, a micro-mechanical model for FRCs under cyclic loading is presented together with a numerical example which shows the effect of fibre orientations on fatigue behaviour.