Experimental study on the low velocity impact responses of all-composite pyramidal truss core sandwich panel after high temperature exposure

The effects of high temperature exposure on the low velocity impact behaviors and damage mechanisms of all-composite pyramidal truss core sandwich panels were investigated by experiment in this paper. The composite sandwich panels were manufactured from unidirectional carbon/epoxy prepreg and exposed to different temperatures for 6 h. The impact tests of exposed specimens were performed at three different energy levels, and the effects of exposure temperature and impact energy level on the damage mechanism, absorbed energy and maximum impact force were analyzed. The impact-damaged specimens were subsequently subjected to in-plane compressive tests in order to investigate the effect of exposure temperature and impact energy level on the compressive failure load. The results have shown that the high temperature exposure has a significant effect on impact properties and damage mechanisms of specimens. The fiber fracture, node failure, delamination and buckling were observed during low velocity impact tests and the extent of damage area was significantly affected by exposure temperature. In addition, the absorbed energy increased with increasing exposure temperature, while the maximum impact force and compressive failure load after impact decreased with increasing exposure temperature due to the degradation of the matrix properties and fiber–matrix interface properties at higher temperatures.