Development of microcellular thermoplastic polyurethane honeycombs with tailored elasticity and energy absorption via CO2 foaming

Abstract

In this study, thermoplastic polyurethane (TPU) honeycombs with ordered macrostructure and microcellular lattice structure was fabricated via the integration of fused deposition modelling (FDM) and solid-state CO2 foaming. The physical foaming induced and introduced the microcellular structure with cell size of about 2.77-12.27 mm into TPU honeycombs. The influences of microcellular structure on the mechanical property, energy absorption and elastic recovery behavior of TPU honeycombs were systematically investigated. Foamed TPU honeycombs had a maximum energy absorption efficiency of 0.40, which was larger than that of the corresponded unfoamed honeycombs (0.32-0.38) owing to having the microcellular structure. The effects of lateral and vertical directions on elastic and energy absorption behaviors were discussed because of the obvious anisotropy of microcellular TPU honeycombs. The advantages of lightweight, soft touching and anisotropic characteristics make microcellular TPU honeycombs have great prospects in small stress and high stress sensitive applications.