Impact and post-impact vibration response of protective metal foam composite sandwich plates

Composite sandwich structures composed of a metal foam core possess the ability to provide significant energy absorption under impact from flying debris, routine operation, tool drop, flying projectiles, or crash conditions. Sandwich constructions of aluminum foam core and a variety of facesheets are being increasingly used in a number of applications ranging from turbine shrouds, heat exchangers, pneumatic tool mufflers, energy absorbers for blast shock waves, and silencers for jet engine intakes. In the present work, vacuum assisted resin transfer molding (VARTM) was used to produce composite sandwich plates with laminate facesheets and aluminum foam core. Aluminum foam of two different thicknesses and densities were studied in conjunction with facesheets composed of either S2-glass, E-glass, aramid, or carbon fiber reinforced vinyl ester (VE) resin. Low velocity impact (LVI), up to 5 m/s, and intermediate velocity impact (IVI), up to 100 m/s, tests were conducted to simulate impact conditions resulting from tool drop to blunt objects, and flying debris. It was concluded from the impact tests that the sandwich construction with S2-glass/VE facesheets in conjunction with aluminum foam was optimal for resisting low and intermediate velocity impact. The vibration response of composite sandwich plates composed of laminate facesheets and aluminum foam core was also studied under a free–free boundary condition. The vibration response (natural frequency and damping ratio) is reported as a function of impact to the sandwich plate.