Investigation of novel multi-layer sandwich panels under quasi-static indentation loading using experimental and numerical analyses

In this study, the effect of multi-layering in sandwich panel composite structures with different configurations of corrugated cores under the effect of quasi-static indentation loading is investigated experimentally and numerically. Composite plates and corrugated cores with equal weight fraction were manually made using ML506 epoxy resin with 15% hardener and the overall volume fraction of 45% for woven glass fibers. Experiments were performed using a cylindrical indenter with a diameter of 20 mm and a semi-spherical nose shape, and the behavior of the composite structure was evaluated in the case of energy absorption, contact force, and fracture mechanisms for different corrugated cores (rectangular, trapezoidal and triangular). Progressive damage analyses of the composite samples were investigated using well-known 3D failure criteria developed in ABAQUS software, and an acceptable agreement between the experimental and numerical results was observed. Experimental results show that multi-layering of composite sandwich panels not only increases the structural strength in quasi-static indentation process but also increases the energy absorption of specimens by increasing the peak load, instantaneous force, and dislocation displacement up to the complete penetration. By comparing different geometries of the corrugated cores in terms of maximum force, energy absorption, and specific energy, it was shown that the functionality of specimens with rectangular cores is the best. Among the most important damage mechanisms of the examined sandwich panel specimens (visual analysis) in the quasi-static indentation process, matrix cracking, fiber breakage, delamination, cell walls buckling and crushing, face sheets and core debonding, and specimens complete penetration are noticeable.