Application of Aluminum Foam for Stress-Wave Management in Lightweight Composite Integral Armor

Abstract

Abstract : Closed-cell aluminum foam offers a unique combination of properties such as low density, high stiffness, strength, and energy absorption that can be tailored through design of the microstructure. During ballistic impact, the foam exhibits significant nonlinear deformation and stress-wave attenuation. Composite structural armor panels containing closed-cell aluminum foam are impacted with 20-mm fragment-simulating projectiles (FSP). One-dimensional plane strain finite element analysis (FEA) of stress-wave propagation is performed to understand the dynamic response and deformation mechanisms. The FEA results correlate well with the experimental observation that aluminum foam can delay and attenuate stress waves. It is identified that the aluminum foam transmits an insignificant amount of stress pulse before complete densification. The ballistic performance of aluminum foam-based composite integral armor is compared with the base-line integral armor of equivalent areal density by impacting panels with 20-mm FSP. A comparative damage study reveals that the aluminum-foam armor has better and finer ceramic fracture and less volumetric delamination of the composite backing plate as compared to the base line. The aluminum-foam armors also showed less dynamic deflection of the backing plate than the base line. These attributes of the aluminum foam in integral armor system add a new dimension in the design of lightweight armor for the future armored vehicles.