Enhanced compressive fatigue model for impact damaged laminates

An enhanced analytical model for prediction of compressive fatigue threshold strains in composite plates with barely visible impact damage (BVID) is presented. The model represents the complex damage morphology as a single circular delamination at a critical level and calculates the strain at which thin-film buckling of the circular delaminated region occurs. The threshold strain is defined as the strain at which the strain energy release rate for the post-buckled delaminated plies is equal to the critical Mode I value (G 1C) for the resin. The model predicts the critical through-thickness level for delamination and also the sensitivity to experimental error in geometric measurements of the damage area. Results obtained using the model show an agreement of fatigue strain to within 4% of experimental values for four sets of data reported in the literature.