Experimental investigation of a hybrid dual-core composite sandwich structure under low-velocity impact loads

The utilisation of composite sandwich structures in high performance applications is gaining growing attention due to its superior stiffness to weight ratio and enhanced energy absorbing characteristics. Pertaining to this, the present study focuses on designing a dual-core hybrid composite sandwich structure comprising aluminium honeycomb (AH) and PVC foam cores, placed between the carbon fiber reinforced polymer (CFRP) face sheets. To investigate the structural performance of the developed sandwich panel (C1/AH + PVC 20 /C2), low velocity impact tests were conducted at energy levels varying from 12 J to 150 J, exhibiting damage from rebound to total perforation. The impact response of the panels was evaluated using force-displacement and energy-time curve. Furthermore, different damage mechanisms involving indentation, inter-layer delamination, core crushing, and fibre fracture were examined through post-impact visual inspection to characterize the energy absorbing behaviour of the sandwich panel. Additionally, three different stacking arrangements of the dual-core sandwich panels (DCSP) were investigated at an impact loading of 150 J, resulting in complete perforation. For the same impact load, the effect of foam core thickness was studied along with a comparative analysis of single and dual core configuration. Among all the sandwich structures, the panel having a symmetric foam arrangement i.e. C1/PVC 10 +AH + PVC 10 /C2 performed better with energy absorption efficiency of 83.9%. It also exhibited highest specific energy absorption of 1.41 J/g at the perforation impact energy. Overall, this work provides a valuable insight in developing a dual-core composite sandwich configuration designs having a strong potential for the application in impact resistant structures such as aircraft fuselage, satellite and UAV protective skin panels, as well as in lightweight high speed automotive crashworthy components, where the combination of progressive energy dissipation through core crushing and improved load distribution can enhance the energy absorption capacity and delayed damage failure.