Experimental and numerical research on foam filled re-entrant cellular structure with negative Poisson's ratio

Mechanical behaviors of a new foam filled 2D re-entrant hexagonal honeycomb with negative Poisson's ratio under planar compression have been investigated in this paper. Re-entrant hexagonal unit cell specimens were fabricated by aluminum alloy and polyurethane foam. The deformation modes and force-displacement curves of the unit cell specimens under compression were carried out experimentally and numerically, and a good agreement was observed between experimental results and numerical simulation results. Subsequently, mechanical behaviors of foam filled and void re-entrant hexagonal honeycomb under planar compression were observed by numerical simulation. Compared to the void honeycomb, the foam filled honeycomb has a higher specific energy absorption capability due to a higher plateau stress. According to the mechanism of auxetic effect, the re-entrant honeycomb would move inward when subjected to compression along the orthogonal direction, which cause a biaxial compression of the foam and an increasing of stiffness/strength/energy absorption capability. The present investigations provide thorough insight into the strengthened re-entrant hexagonal cellular honeycomb, and could be used in the development of novel light weight smart functional structures.