Strategic design and numerical investigation of constant-mass AL-6XN steel and CFRP-based efficient protective structures under air blast loading

The blast or explosion due to terrorist attacks or accidents significantly harms the expensive properties and people. The designing of efficient protective structures at constant mass against these blast loadings is a crucial task. The various configurations of solid, stiffened, and sandwich panels were mostly used as protective structures. The present dynamic explicit numerical study represents a significant comparison of blast performance of solid, stiffened, and honeycomb sandwich panels of equal areal densities. The effects of honeycomb core design parameters on the constant mass sandwich panel’s blast-mitigating characteristics were also discovered. All the designed protective structures were assigned high-strength AL-6XN steel material properties and were subjected to 1–3 kg of spherical-shaped trinitrotoluene explosive blast loads for a constant stand-off distance of 150 mm. The superior-performing metallic sandwich panel was hybridized with carbon fiber-reinforced polymer composite at constant mass to determine its effect. The obtained results indicate that the honeycomb sandwich panels showed 32–87 % and 31–66 % higher energy-absorbing ability than the same mass of solid panels and stiffened panels, respectively, due to their severe core structure crushing. The sandwich panels reduced the protective layer peak deflection by 34–58 % and 19–53 % compared to the equivalent solid panels and stiffened panels, respectively, due to most of the blast energy being absorbed by their front face sheet and core structure. The constant mass honeycomb core of a higher core height with thinner cell walls significantly enhanced the blast-mitigating characteristics of the sandwich panels. The honeycomb core with bigger cell size and higher cell wall thickness applied an adverse effect on the blast resistance characteristics of the constant mass sandwich panels. The hybridization of metallic sandwich panels with composite laminate drastically enhanced the panels’ deformation resistance by uniformly distributing the blast load over the panel and improved the energy absorption characteristics through globalized core compression with delamination, fiber breakage, and matrix cracking failure in the front face sheet.