Low-energy impact behaviour and damage characterization of carbon fibre reinforced polymer and aluminium hybrid laminates

The purpose of this paper is to investigate the impact behaviour and damage characterization of carbon fibre reinforced aluminium hybrid laminates (Al/CFRP) in comparison to classic carbon fibre reinforced polymer (CFRP) at low-velocity and low-energy impact. Impact damage characteristic with damage initiation and progression, internal failure modes and understanding of the role of the metal layers in the impact behaviour under low-energy were examined and discussed. The damage mechanism of the tested laminates is very complex. There is an internal degradation of the material, with the plastic deformation in case of fibre metal laminates. Characteristic matrix cracks (bending and shearing cracks) running at the fibre–matrix interface in composite layers are the first damage mode. The critical damage mode is delaminations observed between composite layers with different orientation as well as delaminations at the metal–composite interface in fibre metal laminates. For the tested materials, particularly carbon fibre reinforced composites, the absorbed impact energy is mainly connected with elastic response and damage of the laminate. In case of fibre metal laminates the absorbed energy is also connected with plastic deformation of the laminate, occurring especially in the metal layers. High impact resistance of fibre metal laminates indicates that metal (aluminium) layers may prevent delamination propagation and impactor penetration.