Fabrication And Characterization Of Auxetic Shape Memory Foams

Shape memory polymers as a kind of smart materials in more and more fields play an important role,such as aerospace,biomedicine and intelligent clothing field and so on.For example,it can be used as a sensor,intelligent device.Comparing with traditional materials,negative Poisson's ratio foam has excellent mechanical properties,such as double curvature,auxetic,etc.,and it has a great potential application in the field of aerospace.Therefore,in this project,shape memory epoxy polyurethane 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 shape memory foam was prepared through thermal-mechanical process.In this paper,the network structure of foam is prepared by one-step mixing of shape memory epoxy resin in polyurethane soft foaming materials.SEM and DSC were employed to characterize the microstructure and transition temperature of shape memory foams.With the increase of epoxy resin content,the glass transition temperature of composite foam rises.By adjust preparation parameters,the auxetic shape memory foam with different re-entrant structure is obtained.Meanwhile,different Poisson's ratios are realized.Shape memory epoxy composite foam compression test,including compression at room temperature and high temperature compression performance test.Foam cell unit and macroscopic effective elastic modulus variation was analyzed based on AshbyGibson crossed cube model during foam compression process.Effective elastic modulus was obtained by compression test.With the increase of shape memory epoxy resin content,the effective elastic modulus firstly decreases and then remains unchanged.The yield strength decreases at first and then increases.The high-speed digital camera and MATLAB image processing technology were employed to carry out the auxetic shape memory foam compression test.The effect of processing parameters on Poisson's ratio of foam was analyzed,which provide certain guiding significance for the further shape memory foam preparation.The fixation ratio and shape recovery ratio were characterized for auxetic shape memory foam.The changes in volume of auxetic foam has been investigated during shape memory cycle.The actuation force was also investigated for auxetic foam.