Design of lightweight protective structures: Computational prediction of ballistic perforation resistance in layered aluminum and steel targets
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Instead of using monolithic steel plates in protective structures, modern research has studied the possibility of using lightweight alloys and layered targets as a replacement. Layered lightweight protective structures are therefore the subject of this study. Experimental research was conducted to evaluate the mechanical behavior of the aluminum alloyAA6060, and steel alloy Hardox 450. Another aluminum, AA7075-T651, and another steel alloy, Armox 560T, were also used in this study, although earlier works provided necessary information about these materials. The primary goal was to determine the validity of computer-aided design of layered protective structures using FEM software.A second objective was to determine whether an optimal conjunction of aluminum and steel can be found to create a lighter protection structure. Ballistic experiments were carried out as a reference to verify the material models used in the numerical simulations. Monolithic plate Hardox 450 and AA6060 were tested for ballistic resistance against APM2 projectiles, which are categorized as small arms armorpiercing bullets. Ballistic limit velocity was determined with a Recht-Ipson model by using least square method. The problem was modeled in a 2D axis-symmetric problem in LS-DYNA with only the bullet core as the projectile. Experimental and numerical data showed great agreement for monolithic plates. Thus, numerical simulations with layered targets were initiated to determine if a lighter construction of both aluminium and steel, with a perforation resistance comparable to that of a monolithic steel plate, could be created. Simulations of target congurations with 18 mm aluminum and 6 mm steel were performed to determine the ballistic limit velocity of a target conguration of similar weightto 12 mm single plate steel targets. These numerical analyses needed verification, thus, a third ballistic experiment was carried out using Hardox 450 and AA6060 as layeredplate targets. Because the numerical data was consistent with the experimental results, it was concluded that it would be reasonable to design layered targets using this method. Furthermore, additional configurations using different amounts of aluminum and steel were studied numerically to determine if lightweight protection structures were possible.The results showed that a configuration of aluminum and steel, with a total weight per square meter similar to that of a monolithic steel plate can archieve comparable ballistic perforation resistance. However, high strength alloys are absolutely vital in constructing a lighter protective structure.