Investigation of the structural parameters aimed to improve low velocity impact performance of sandwich composites

In this study, it is aimed to increase the low velocity impact performance of sandwich composites. Sandwich composites have higher bending stiffness and absorbed energy values in low velocity impact test than laminated composites. However, due to the strength difference between facesheet and core material in the sandwich composite, delamination may occur in this interface. Studies have been carried out to increase the absorbed energy value and to reduce the delamination area by performing various modifications on sandwich composites in the low velocity impact. The modifications were performed in the sandwich composite structures by using two-part core, forming epoxy columns in the core, stitching through the core, stitching the core and the facesheets together. The numerical results of composites were compared with experimental results according to the contact force - time curves, the contact force - deflection curves and absorbed energy values. In the low velocity impact test, the impactor mass was kept constant and the impact energy was obtained by changing the impactor velocity. Due to the out of plane modifications, which will affect the low velocity impact behavior of sandwich composites, increase in the absorbed energy values and the decrease in the delamination areas were achieved. It has been determined that the core stitching process may be an alternative to the facesheet stitching process in terms of absorbed energy value. The finite element analysis results by using LS-DYNA software were compared with experimental results and a good agreement between them was observed.