Impact resistance and damage characteristics of composite laminates

This paper presents an investigation into the damage characteristics and failure strengths of composite laminates at low velocity impact tests. Three E-glass fabrics, non-crimp fabric, woven fabric, and nonwoven mat, were selected as reinforcements for the composite laminates. Impact tests were conducted using a guided drop-weight test rig in ascending energy to 24 J/layer nominal impact energy. Metallographic microscopy was used to observe the damage characteristics of the perpendicular cross-section of the impacted laminates after a micropowder polishing treatment. When the load–time and the energy–time histories were compared with the fractographics, it was found that fiber breakage had occurred prior to the major damage. When the impact energy increased over the threshold energy of the major damage, matrix cracking, delamination, and fiber breakage were observed at the back surface, below a nearly undamaged zone, which were attributed to the bending stresses.