Fabrication of Graphene-Reinforced Closed-Cell Aluminum Foam and Characterization at High Strain Rates

Closed-cell aluminum foam is a lightweight cellular material that can sustain considerable deformation under approximately constant stress known as plateau stress. Aluminum foam is commonly used for mitigating the effect of dynamic loadings, such as impact, through its energy absorption capability. However, the plateau stress is relatively low and thus limits energy absorption while precluding its use in structural load-bearing applications. In this investigation, aluminum foam reinforced with graphene platelets was fabricated using the liquid metallurgy route to enhance the plateau stress and energy absorption. The high strain rate response of the reinforced foam has been investigated. Graphene concentrations in the range of 0.20 to 0.62 wt.% were used. The dynamic compressive behavior of Al foam reinforced with graphene was studied under high strain rate loading from 1000 to 2200 s(-1) using the split Hopkinson Pressure Bar apparatus. Among the different graphene concentrations investigated, 0.62 wt.% graphene aluminum foam showed the maximum peak stress, plateau stress and energy absorption, while 0.4 wt.% graphene exhibited the minimum plateau stress and energy absorption under the various dynamic loading conditions studied. However, the graphene-added hybrid foam always exhibited higher plateau stress and energy absorption as compared to those without graphene. Graphene-reinforced aluminum foam is a viable lightweight material for energy absorption under dynamic loading conditions. The reinforced aluminum foam displays a threefold enhancement in plateau stress and energy absorption as compared to unreinforced foam.