Effect of block copolymer nano-reinforcements on the low velocity impact response of sandwich structures

Sandwich composites with fibre reinforced plastic (FRP) facesheets have emerged as a major class of lightweight structural materials in a wide range of engineering fields including aerospace, automotive and marine structures. This is due to attractive mechanical properties such as high specific stiffness and high strength. However, sandwich structures are susceptible to damage caused by impact. The objective of this paper is to evaluate the dynamic response of sandwich composites based on Kevlar fibre reinforced epoxy and Rohacell® foam. The improvement in impact performance of these sandwich structures that can be achieved by the addition of nanoparticles in the resin matrix is investigated. Nanostrength®, an acrylate triblock copolymer that self-assembles in the nanometer scale is added to the epoxy matrix. The effect of the nano-reinforcements on flat sandwich plates under low velocity impact is investigated at different scales. An instrumented drop tower setup is used for the low velocity impact tests of the sandwich plates with neat or nano-reinforced epoxy matrix, at different energies. The macroscopic response of the sandwich structure and the microscopic phenomena involved in dissipating the impact energy are identified and compared for sandwich plates with and without nanoparticles.