Effect of impact loading on damage and Residual Compressive Strength of CFRP laminated beams

The effect of flexural impact loading on damage characteristics and on Residual Compressive Strength (RCS) of CFRP composite beam specimens was investigated. Detection and follow-up of interlaminar damage initiation and propagation processes were conducted via video inspection of specimens subjected to quasi-static loading. It was found that the shear delamination mechanism is the most effective in the reduction of RCS. The edge delamination process, on the other hand, seems to have only a minor effect on residual failure characteristics. Compressive failure was mainly controlled by sub-laminate buckling, which seems to be dependent on delamination length, damage location and layer sequence. The presence of tough adhesive interlayers was found to delay and even prevent interlaminar damage formation and growth under flexure and compressive loading. The dependence of RCS on initial flexural energy seems to be similar under both quasi-static and impact loading modes. It was concluded that the inter-relationship of flexural energy, damage characteristics and RCS, as derived via beam specimen testing, may provide a sensitive tool for comparative damage tolerance evaluation of different composite material configurations.