Experimental and Numerical studies of Fiber Metal Laminates comprising Ballistic fabrics subjected to Shock Impact

Abstract

The scope of fiber metal laminates (FMLs) in the applications for shock and blastwave mitigation has been gaining a lot of focus recently. The response of the FML structures to side-on interaction with shock waves was experimentally investigated using a shock tube. The influence of incorporating ballistic grade fabrics as sandwiched plies between metallic skins in addition to low acoustic impedance materials was explored in the current work. Five sequences of laminates were fabricated employing AA6061-T6 skins, with aramid-epoxy, ultra-high molecular weight polyethylene-epoxy, and paperboard-epoxy as sandwiched layers. The deformation profiles of different sequences were investigated and the stackups with the best shock mitigation response were identified. A numerical model for the laminate transverse deformation was developed. The deformations of the faceplate and the backplate of each sequence were compared to the numerical results. Among the five sequences, BRSP-II and BRSP-IV showed the least backplate deformation of ∼−0.25 mm after single shock impact, while the same configurations showed lowest backplate deformation ∼−0.6 mm after the second shock impact, as compared to the other sequences. The twin shock impacted specimens of various sequences were subjected to Cone beam computed tomography (CBCT) for layerwise investigation of shock impact. The four sequences BRSP-I, BRSP-II, BRSP-III and BRSP-IV showed deformations in all the plies with no delamination. However, delamination was observed at the center in BRSP-V between the backplate and the penultimate ply.