INSITU DAMAGE EVOLUTION AND MICRO MACRO TRANSITION FOR LAMINATED COMPOSITES

In this paper, a theoretical formulation for the development of matrix cracking damage in composite laminates is presented. To describe the constraint effects on any layer k, an in-situ damage effective function, LAMBDA(ij)(k), is introduced. An equivalent constraint model and a micro/macroscopic damage analysis are then developed to express LAMBDA(ij)(k) explicitly in terms of constraint stiffness and thickness ratio as well as a damage state variable, D(k). The reduction of E, G and nu in the in-situ damage state and a constrained damage evolution law incorporating residual curing strain are then derived through LAMBDA(ij)(k) and dLAMBDA(ij)(k)/dD(k), respectively. A series of experimental results are correlated and some phenomena, such as the effects of the lamina thickness on damage initiation, damage evolution, and energy dissipation, are predicted and explained.