Improvement of the in-plane crushing response of CFRP sandwich panels by through-thickness reinforcements

Fibre reinforced plastic (FRP) composite materials can provide superior specific energy absorption performance over conventional metallic structures if crush stability can be maintained during the impact event. The core in sandwich structures helps to stabilise the crush front by preventing global buckling, but delamination remains a barrier to optimal crushing performance. In this work, the in-plane crushing response of sandwich structures was improved by adding through-thickness reinforcement in the form of aramid fibre tufts. The effect of tufting different sandwich cores and facesheet orientations was investigated in both static and dynamic crushing modes. A drop-tower test rig was used to crush panels in realistic automotive crash conditions and a high-speed camera captured the crushing mechanisms. The through-thickness reinforcement improved the facesheet to core adhesion, resulting in a more localised and stable fracture of the facesheets. Tufting improved the specific energy absorption (SEA) from 11.5 kJ/kg to 20.5 kJ/kg and the crush force efficiency (CFE) from 0.22 to 0.55.