A composite damage module and a user interface module will be developed and integrated into a commercial finite element code for 1) predicting the extent of damage and the mode of failure in laminated composite structures resulting from low-velocity impact and 2) for estimating residual stiffness and strength of the composite structures after impact. The development of the composite damage module will be based on the progressive damage model that was developed by the Co-PI and his associates. The proposed module consists of a material simulator and a damage estimator. The material simulator calculates the effective mechanical properties of composites for a given state of damage in terms of fiber failure, matrix cracking, and delamination. The damage estimator predicts the state of damage for a given state of stresses or strains in composites which are calculated from a commercial finite element code. The proposed interface module will provide a linkage between the commercial code and the damage module. Accordingly, by interacting with the damage module, the commercial code would be able to predict impact damage and to characterize the effect of such damage on the residual strength of structures with complex configurations made of laminated composites. The integrated finite element code could be used as a tool for the optimal design of composite structures as well as for the assessment of the integrity of the structures in service. The proposed composite damage module combined with a commercial finite element code would enable users to predict impact damage and to assess the effect of such damage on the residual stiffness and strength of composite structures with complex configuration such as motor cases, launch tubes, pressure vessels, etc. Accordingly, expensive tests could be reduced and more accurate structural integrity evaluation could be performed.
