Fabrication and characterization of auxetic shape memory composite foams

Shape memory polymers, as a kind of smart materials, play an important role in more and more fields, such as aerospace, biomedicine and intelligent clothing field and so on. Comparing with traditional materials, negative Poisson's ratio foam has excellent mechanical properties, such as double curvature, light weight, high shear resistance, auxetic etc., and it has a great potential application in the field of aerospace. Therefore, in this project, shape memory composite foam was fabricated based on the commercial soft polyurethane foam material as matrix and shape memory epoxy resin as functional phase. Negative Poisson's ratio of foam was fabricated based on its shape memory feature through a process of triaxial compression with heat treatment. Microstructure deformation was characterized after the transformation of auxetic foam. By adjusting the processing parameters, the auxetic shape memory foam with different “re-entrant” structure was obtained. Such fabricated shape memory composite foams display variable stiffness with auxetic behavior. Effective compressive and tensile modulus was obtained by compression and tension tests. The effect of processing parameters on foam Poisson's ratio was analyzed, which provided certain guiding significance for the further shape memory foam preparation.