Low-velocity impact response of high-performance aluminum foam sandwich structures

The impact response of a range of novel sandwich structures based on fiber-reinforced thermoplastic and fiber-metal laminate (FML) skins is studied. Indentation tests on these structures show that the indentation constants in a generalized indentation law exhibit a rate-sensitive response over the range of loading conditions examined here. Low-velocity impact tests show that these systems are capable of absorbing energy through localized plastic deformation and crushing in the metal core. An energy-balance model accounting for energy dissipation in bending, shear, and indentation effects is used to predict the maximum force during the impact event. It is found that the model accurately predicts the low-velocity impact response of the plain sandwich structures up to energies close to 30 J. In contrast, the model is only capable of predicting the low-energy response of the FML sandwich structures (typically up to 2J). At higher energies, a horizontal shear crack initiates in the metal core causing the maximum force to drop below that predicted by the model. Using an energy-partitioning approach, it is shown that indentation effects account for over half of the energy absorbed in the FML-based sandwich structures.