Numerical modelling of foam-core sandwich panels with nano-reinforced composite facesheets

Sandwich composites with fibre-reinforced plastic facesheets and foam core have emerged as a major class of lightweight structural materials but low-velocity impact damage severely reduces the structural integrity of the component. Different methods have been proposed to improve the impact damage resistance of sandwich composites including the addition of nanoparticles to the matrix. The objective of this paper is to evaluate the effect of adding nanostrength, a block copolymer that self-assembles in the nanoscale, to the epoxy matrix on the low-velocity impact behaviour of sandwich panels with Kevlar facesheets and Rohacell foam core. Most previous studies on low-velocity impact damage used experimental testing but a combination of improved constitutive modelling of constituents and decreased computational costs make it possible to utilise continuum modelling to numerically simulate impact response of sandwich composites for a much wider range of conditions. A numerical model was developed in explicit FE software LS-Dyna and a constitutive law based on continuum damage mechanics was used for the simulation of the composite facesheets with and without the nano-reinforcements. A crushable foam model was used for the Rohacell foam core. The LS-Dyna model was validated by comparing the force, displacement measurements and damage assessment from the simulation with experimental impact tests conducted using a drop tower. The FE model shows good comparison with the experiment and a macroscopic phenomenological model is capable of capturing the impact damage behaviour of the sandwich plates with nano-reinforcements.