Manufacture and behaviour of innovative 3D printed auxetic composite panels subjected to low-velocity impact load

This paper investigated the low-velocity impact behaviour of innovative 3D printed auxetic composite panels experimentally. The panel consisted of glass fibre reinforced polymer skins and a 3D printed glass fibre - polyamide 12 (with fibre weight content of 30%) composite core. The core was extended from the 3D re-entrant auxetic unit cell, which consisted of four umbrella shaped elements arranging in a specific manner and the auxetic behaviour was caused by 'folding up' or 'opening' of these elements. A total of 15 composite panels were fabricated and tested under low-velocity impact, the main parameters of which were the diagonal rod radius of the core and the impact energy. Test results revealed that the auxetic behaviour of the composite panel could be observed using high-speed camera. Besides, as the impact energy increased, the panel failed more brittlely or even destroyed completely. In addition, the larger impact energy resulted in larger damage area of the skin and higher peak impact load of the composite panel. Moreover, with the same impact energy, the increased rod radius resulted in a stiffer structure, which had larger impact resistance and thus the damage was minor, leading to larger impact load. The peak impact load to normalized weight ratio was similar for specimens with different rod radius, indicating that increasing rod radius could not improve the material efficiency in resisting impact load.