An experimental study of damage accumulation in balanced CFRP laminates due to repeated impact

The behaviour of balanced laminates (symmetric, antisymmetric and asymmetric) under repeated low energy hits of a 12.1 mm hemispheric impactor was evaluated. The resistance to the impulsive force was found to be influenced by the stacking sequence and the crack path through the laminate. The symmetric plate with different ply directions proved to have best resistance to impact. The rate of damage progression in the event was characterised by an equation from the energy profile that correlates the propagation energy and time. This was differentiated to give the rate of damage evolution. A comparison of the bending stiffness obtained from the force-displacement plot of the first impact, revealed that the symmetric composite had the highest stiffness. Noted at perforation were fibre breakage and matrix cracking. (C) 2007 Elsevier Ltd. All rights reserved.