Stiffness and failure behaviour of folded sandwich cores under combined transverse shear and compression

For efficiently simulating the failure behaviour of sandwich structures made of stiff face sheets and a light-weight core, macroscopic material stiffness and strength values are essential. The investigated folded cores are made from Nomex paper coated with epoxy resin. Due to their channel-like structure, folded cores are air ventilated, which can help to reduce the danger of deterioration, which is a big advancement for applications in the aerospace industry. Folded core structures were tested under combined transverse compression and shear in order to get the stiffness values and the failure criterion under a multi-axial stress state. For this purpose a new test device was developed, which allows a simultaneous application of shear and compression loads. The test results are presented and discussed using a nonlinear description of the stiffness and failure behaviour of the folded core structure. Additionally, the results are compared to the stiffness and the failure behaviour of honeycomb cores.