Characteristics of fatigue crack growth in GFRP laminates

Multiple fatigue crack growth behaviour has been studied in quasi-isotropic GFRP laminates under constant amplitude fatigue loading conditions. Characteristics of fatigue crack growth in off-axis plies have been described and comparisons have been made between quasi-static and fatigue crack growth behaviour. Careful monitoring of individual fatigue cracks reveals three distinct stages of crack growth including initiation, steady-state crack growth (SSCG) and crack interaction and saturation. Stress redistribution due to matrix cracking and the associated stiffness reduction have been simulated using finite element models. Strain energy release rates associated with the off-axis matrix cracking have also been obtained and correlated with the measured fatigue crack growth rates.