BEM analysis of damage progress in 0/90 laminates

The massive use of composites in primary structures of modern commercial aeroplanes is leading to the need for profound knowledge of the mechanisms of damage and failure of heterogeneous materials of this type. This knowledge requires a very fine evaluation of the stress state, which in turn is needed to calculate the parameters of fracture mechanics used to evaluate the integrity or damage tolerance of a particular component. In this paper, the initiation and growth of the damage in a typical 0/90]_S laminate is investigated. Using a BEM code allowing contact between the lips of interfacial cracks appearing in the damaged configuration and based on a former generalized plane strain formulation of the problem developed by the authors, the energy release rate (ERR) is calculated for different configurations corresponding to the different intermediate states that may occur in the process of damage generation. The numerical results obtained clarify some aspects of the progression of the damage and open up the possibility, using comparison with experimental results, of understanding, and consequently improving, the performance of composite materials.