Mechanical properties of crumpled aluminum foils

Crumpled foils are a new type of material with promising characteristics due to their interesting mechanical properties associated with their low weight. They are fabricated by dye compaction, resulting in a structure consisting of randomly arranged ridges and vertices, thus providing a lot of self-contact. Mechanical properties and internal complex mesostructures were investigated using non-destructive techniques in order to link the microstructure to mechanical properties. As regards the mechanical characteristics, the influence of different parameters was studied: volume fraction of solid, loading–unloading cycle, simple or closed die compression, pre-folding of foils, compaction rate and creation of local welding. It appears possible to significantly change the mechanical behavior of crumpled foils, especially by increasing the solid fraction but also by generating the local welding of foils in the microstructure. A study of relaxation was also performed, which showed that these materials are slightly sensitive to deformation rate. Finally, a qualitative and quantitative study of the microstructure by in situ tests using X-ray tomography was conducted. This resulted in a better understanding of the behavior and local organization of foils during compaction.