High strain rate dynamic compressive properties and deformation behavior of Al matrix composite foams reinforced by in-situ grown carbon nanotubes

In this paper, high strain rate dynamic compressive properties of the CNT/Al composite foams reinforced by in-situ grown carbon nanotubes (CNTs) have been investigated. The results show that the compressive strength and energy absorption capacity of the CNT/Al composite foams not only increase with the increment of CNT content but also increase with the strain rate increasing, revealing a typical strain rate sensitivity. For the 3.0 wt%-CNT/Al composite foams, the peak stress at 2130 s−1 is 52.5 MPa, which is ~ 86% higher than that at 0.001 s−1 (28.2 MPa). Besides, the deformation behavior of the pure Al foam can be significantly affected by the CNT addition and the strain rate. The different deformation behavior of the pure Al foam and composite foams is closely associated with the microstructure of pore walls. For the pure Al foam under the quasi-static condition, it can be recognised as firstly forms localized deformation bands, followed by the collapse of multi-layer deformation bands. While the failure of the CNT/Al composite foams mainly belongs to the shear deformation. In addition, as the strain rate increases from 0.001 to 800 s−1, the deformation way of the pure Al foam transits from the local failure to layers of collapsing. Whereas, the CNT/Al composite foams still manifest as the formation of shear bands. Moreover, the pore fracture, collapsing and friction, as well as the crack propagation during the compressive processes are all beneficial to the energy absorption enhancement of the CNT/Al composite foams.