An interactive damage progression model for cross-ply laminates subject to fatigue load cycles

Transverse cracking and crack induced delaminations growth are generally considered as the most relevant damage modes developing during the fatigue loading of composite laminates. So far, non-interactive damage progression schemes have been considered, arguing that transverse cracks saturate before the initiation of induced delaminations, despite concurrent damage accumulation has been experimentally acknowledged, also suggesting mutual interaction. In the present paper a simultaneous and interactive damage progression scheme based on fracture mechanics is proposed. A two-dimensional variational mechanics analysis approach is used to obtain the individual energy release rates and the interaction between damage modes is theoretically acknowledged. Also, a unique parameter is proposed accounting for both the damage modes accumulation levels, ruling the growth rates of the individual damage modes, and the characteristic damage state is questioned. Theoretical findings are then verified using multi-scale fatigue damage data from GFRP cross-ply laminate specimens subjected to uniaxial fatigue loading