Damage mechanics has been applied to describe the cyclic behaviour of glass fibre-polyester and carbon fibre-epoxy composites with different lay-ups under various loading conditions. Damage evolution was determined by continually monitoring fatigue modulus degradation and measuring the crack density. These methods complemented each other. They showed that the damage could be separated into two stages. Damage evolved rapidly for the first 10% of life, followed by a more gradual and linear accumulation for the remainder of life. In general, the transition from the first to the second stage indicated a change from transverse matrix cracking to fibre-matrix debonding and coalescence. Damage mechanics was applied to the fatigue modulus changes that occurred in the stress-strain hysteresis loops, monitored throughout life. A two-stage model was applied to express damage evolution using the modulus- and crack-based damage parameters. This model successfully described cyclic damage evolution for different lay ups of the PMCs. The significance of which was that the amount of fatigue damage for any stress level at the end of the initial stage could be used to accurately predict fatigue life and construct a stress-life diagram for the given composite
Cyclic behaviour modelling of GFRP adhesive connections by an imperfect soft interface model with damage evolution
