Study On Properties And Preparation Of Shape Memory Epoxy Composites For Deployment Structure

Aiming at the demand of folding and deployment resistance,strong deformability and high shape recovery ratio of shape memory epoxy resins for application of deployable structure,in the paper the polypropylene glycol diglycidyl ether(PPGDGE)or monoamine curing agents with flexible chain segments were introduced in systems to regulate the network structure of epoxy resin.Three shape memory epoxy systems cured with fatty amine were established.The cure kinetics,glass transition temperature,cross-link density,tensile properties and shape memory performances were evaluated in resin systems.The viscoelastic theoretical model was established,and the shape memory process of deployable structures with epoxy composites was simulated with finite element.The changes and influences of several key parameters were discussed during the deployable process.E51-TETA shape memory epoxy resin systems were synthesized by using triethylenetetramine(TETA)as a curing agent.The degree of cross-linking of stationary phases was changed by regulating the ratio of TETA.And the ET-80% system with the moderate cross-link density and best shape memory performance was confirmed.Further,the flexible PPGDGE was introduced to prepare E51-TETA-PPGDGE shape memory epoxy resin systems,and the reaction mechanism of E51-TETA-PPGDGE was proposed.The curing kinetics equations of resin systems were established by using DSC analysis method.The analysis of equal-transition ratio method indicated that the E51-TETA-PPGDGE resin system showed a decrease in activation energy.By using ?esták-Berggren method and model fitting reaction kinetics analysis method in combination,it was proved that the autocatalytic kinetic equation was suitable to describe the curing reactions of E51-TETA-PPGDGE systems well.The dynamic mechanical analysis results indicated that the glass transition temperature decreased with the increase of PPGDGE contents,while the peak height of loss factor and the value of full width at half maximum increased.The results imply that PPGDGE is useful to improve the toughness of the systems.ETP-15% exhibited the best overall performance,the fold-deploy cycles of which could reach 13.The shape memory E51-TETA-monoamine epoxy systems were synthesized by using octylamine,dodecylamine,hexadecylamine and TETA as common curing agents.The cure kinetics,glass transition temperature,cross-link density,dynamic mechanical performances,tensile performances and shape memory performances were evaluated in each system.The results showed that with the increase of contents of monoamine,cross-link density and stationary phase content decreased,leading to a decrease of shape fixity ratio.In the systems with the same contents of amine,the more the carbon numbers of monoamine,the lower the glass transition temperature value,and the cross-link density did not change remarkably.The exercise capacity of the molecular chain is increased in the release process of internal stress,leading to the increase of shape recovery rate.Considering the tensile and shape memory properties,ETM8-50% was determined as the best system.The shape fixity ratio of this system was greater than 98.0%,the shape recovery ratio was achieved to 100.0%,and the maximum fold-deploy cycling number was 16.The aramid fiber and carbon fiber reinforced shape memory epoxy composites were prepared by using ET-80%,ETP-15% and ETM8-50%,respectively.The results showed that the shape fixity ratio decreased significantly after fiber reinforcement,and the shape fixity ratio of aramid fiber reinforced system was higher than carbon fiber.With the increase of resin contents in composites,the shape fixity ratio was increased.When the resin content of each system is more than 40%,the shape fixity ratios were all above 96.0%.These data could meet the application requirements for deployable space structures.The epoxy composite shape memory deployable arms and antenna support ring were prepared and the good deployable properties were verified,which could meet the demand of deployable structure.The deployable structures of flat tape,curved tape,and circular tube were prepared with shape memory epoxy composite.The shape memory fold-deploy experiments were carried out as well.The viscoelastic theoretical model was established,and the shape memory deployable process of composite structures was simulated with ABAQUS.The results showed that the finite element model based on viscoelastic theory could simulate the full deployable process of each deployable structure.The finite element model could describe the temperature dependence of deployment angle,axial stress and axial strain in the shape memory folding step,cooling step,constraint removal step and reheating step.The results of finite element simulation showed that the long-term shear modulus and instantaneous relaxation modulus of viscoelastic materials had a great influence on shape memory performance.However,the instantaneous relaxation modulus did not show any effect on strain and deploy rate during the deployable process.The relaxation time of the material directly affected the deploy rate of recovery process.The longer the relaxation time,the more the required time for recovery of deployable structure.