Preparation Of Gradient Cellular Plastics With Energy Absorption By Ice-templating Method

Shock absorbing and energy absorption foam materials have attracted attention from researchers due to their lightweight and strong energy absorption properties.According to different protection objects of foaming materials,energy absorption foam materials can be classified into hard energy absorbing foam materials and soft energy absorbing foam materials.The rigid energy absorbing foam material has high modulus,long plateau strain and large plateau stress.Usually used in scenarios such as car collisions and aerospace equipment landings to provide certain protection for objects with high stiffness.Soft energy absorbing and shock absorbing foam materials usually have low modulus,and the compression process presents a J-shaped stress-strain curve.The main protective objects of soft energy absorbing materials are fragile or low modulus tissues,such as glassware,precision instruments,and knees and elbows.However,at present,the density of metal foam of hard energy absorbing foam material is too high,and the energy absorption value of hard polymer foam material is low,so it is difficult to achieve the effect of both light weight and high energy absorption;The current soft energy absorbing foam materials have low energy dissipation rate,high density and poor repeatability and practicality.Starting from biomimetic research methods,this article investigates the pore structure of natural pomelo peel through electronic scanning electron microscopy and microcomputer tomography observation.A kind of grapefruit skin like soft polyimide foam with gradient structure was prepared by multi-layer freezing using ice template method.The microstructure,compression process,and energy absorption ability of the imitation pomelo peel material were studied separately.The compression curve and energy absorption capability of as prepared pomelo-ppel-mimetic porous material is very similar to pomelo peel,and it has the ability to be used multiple times.In addition,rigid oriented porous polymer materials with density gradient were prepared from commercial epoxy resin emulsion.Through the analysis of quasi-static compression process,we found that gradient oriented porous foam has higher energy absorption value,lower impact stress and longer impact time than non gradient oriented porous foam and disordered porous foam.Under the condition of low density,the energy absorption value of our oriented gradient porous material is nearly twice that of ordinary polymer foam,and the density under the condition of the same energy absorption value is only 1/2 of that of metal foam.