Experimental and Numerical Modelling of Ballistic Impact on Fiber Metal Laminates Based on Aramid Fiber Reinforced Epoxy

This paper investigates the ballistic impact behavior of fiber metal laminates (FML) composed of aramid fiber-reinforced epoxy with a central layer of aluminum alloy Al5083. The research examines the ballistic performance influenced by factors such as hole shape and depth in the laminate and integrates both macro and microstructural analyses of FMLs. The FML variations studied included a perforated first layer with hole diameters of 3 mm and 5 mm, through which bullets penetrated. Ballistic tests were conducted from a firing distance of 5 meters using 9-mm cartridges loaded with full metal jacket bullets approximately 25 mm wide, fired at an angle perpendicular to the target surface. The experimental and simulation ballistic impact tests closely matched, with a 95.63% agreement and an error margin of about 4.37%. The FML resisted bullet impact by allowing perforation through three layers (the aluminum plate and the first and second aramid/epoxy plies) while forming a bulge due to longitudinal deformation in the final layer (the back plate). The experimental and simulation results showed similar trends, with a 5 mm diameter hole leading to a deeper bulge on the backside. Bullet penetration at the center, following a square pattern, resulted in the smallest bulge formation and a reduction in both initial and final bullet velocities. The fracture morphology indicates a ductile fracture, characterized by dominant dimple formations across the surface. The dimples in the FMLs are coarser than those in monolithic aluminum plates due to the reduced bullet velocity as it penetrates each layer of the target FMLs, significantly decreasing the remaining bullet velocity. In contrast, monolithic aluminum plates exhibit a minimal velocity decrease, resulting in smoother dimple fractures.