A unified damage model for fibrous composite laminae subject to in-plane stress-state and having multi material-nonlinearity

In the present study, a novel methodology of damage modeling is introduced to predict damage propagation in fibrous composite materials according to the plastic strain energy density induced in the lamina only. The importance of the new damage-model is the ability to assess damage-evolution in fibrous composite laminae irrespective of stress-state and fiber-orientation angle. An energy-based model called as a unified damage model, is proposed to evaluate damage in unidirectional fibrous composite laminae. The aforementioned damage model represents a unique relationship between damage-evolution and the resulting plastic strain energy density induced in the composite lamina, as verified through this study. Damage propagation under a state of in-plane-stress is investigated for three composite laminas; boron/epoxy, graphite/epoxy, and carbon/epoxy. The unified damage model represents a simplified mathematical relation of quantum-damage (or modified-damage) variables in terms of the induced plastic-strain-energy density induced in a composite lamina. The developed unified damage model confirms the results of Ghazi-Ahmad macro-mechanical damage model in which graphite/epoxy has the lowest damage response, whereas boron/epoxy has the highest possible damage response amongst the three composite materials. Also, it is noticed that quantum-damage propagates nonlinearly with the evolved plastic strain energy density in fibrous composite laminae.