Energy absorption and damage characterization of GFRP laminated and PVC-foam sandwich composites under repeated impacts with reduced energies and quasi-static indentation

During service conditions, composite materials used in naval applications are subjected to repeated impact, the resultant damage can seriously affect their mechanical performance. Therefore, the knowledge of impact energy absorption is important to improve the impact damage tolerance of those materials under the multiple impacts. The main purpose of this original study is to investigate and compare the energy-absorbing capability, and the damage response of GFRP laminated and PVC-foam sandwich composite panels used in real naval and aeronautical structures, under repeated low-velocity impact with reduced energies and quasi-static indentation. To do so, a series of repeated impacts tests were performed until complete absorption of the imposed energy, and quasi-static indentation tests were conducted. Furthermore, the cumulative energy absorbed and inelastic restitution (IRI) indexes were proposed to evaluate energy-absorbing capacity, and the necessary allowable shear stress to initiate damage in the laminated composite was determined. The results of the repeated impact revealed that 80% of the initial energy was absorbed by the sandwich composite which is composed of two 4 mm laminated skin compared to about 60% for 8 mm laminate composite just after the first impact due to the damping power of the core. However, the indentation energy absorbed and the damage configuration for 8 mm laminates are almost the same for sandwiches. This result proves that the core does not have a significant effect on the quasi-static response of the PVC-foam sandwich due to its low perforation resistance.