Study on Anisotropic Crushing Behavior of the Functionally Gradient Aluminum Foam

Due to the continuous variation of material density in functionally gradient aluminum foams, a feedback load gradually increases within the compression process. Currently, most of the researches have been focused on the longitudinal compression mechanical response. However, considering the possible transverse impact in practical application, we investigated functionally gradient aluminum foams in terms of the axial and transverse compressive mechanical responses based on low-speed impact experiments, and also studied their macro and mesoscopic crushing mechanism via the digital image correlation and numerical simulation technology. The results were shown that: (1) Compared with that under longitudinal compression, the functional gradient aluminum under transverse compression has higher compressive strength and lower platform stress, densification strain and energy absorption. (2) In the aspect of failure deformation mode, the longitudinal compression deformation mode is progressive compression of deformation band, while the deformation band of transverse compression appears randomly at each position of the sample. (3) Under transverse compression, the densification strain and specific energy absorption of the functionally gradient aluminum foam get decreased by the reduction of cellular utilization in the higher porosity zone. (4) The established elastic-plastic hardening-locking (E-PH-L) constitutive model can well capture the longitude compression response of the functionally gradient aluminum foam. This study therefore can provide a reference for the theoretical design of functionally gradient aluminum foam in the protection engineering of explosive impact structures.