Design And Mechanical Properties Of Multilayer Structure Based On Shape Memory Polymer

In this paper,a multi-layer structure that can realize tunable Poisson's ratio changes is designed based on shape memory polymers.At the same time,the different porosity of the structure and the designability of the sandwich method are used to achieve the overall structural modulus and Poisson's ratio.Secondly,the influence of the introduction of a highly elastic polymer on the shape memory effect of the shape memory polymer was studied.Finally,the influence of temperature and strain rate on the buckling deformation mode of this type of multilayer structure was explored.First of all,this paper designs a two-dimensional cell with different porosities that can cause in-plane elastic instability,which is controlled by the change in compression displacement,and assembles the cells into a periodic grid structure,and introduces the use of 3D printers to print specimens.Process and requirements.In terms of theoretical models,this article uses the generalized Maxwell model to simulate the viscoelastic behavior of these two materials under load.Through theoretical analysis and formula derivation,a viscoelastic theoretical model suitable for the materials in the structure is obtained.Then,this article mainly conducts dynamic thermomechanical performance(DMA)test on the thermoplastic polyurethane(TPU)and polylactic acid(PLA)used in the test,and the shape memory performance test of PLA.Using the experimental data obtained from the finite element simulation software ABAQUS nonlinear fitting test,the parameters in the constitutive equation of the viscoelastic polymer in Chapter 2 are obtained.At the same time,using the derived constitutive equation and time-temperature equivalent model,using finite element software to simulate and analyze the deformation characteristics of cells with different porosity and grid structure,and further using finite element software to simulate and analyze the three-dimensional solid elements in different sandwich ratios.In,the law of the influence of the sandwich ratio on the mechanical properties of the bi-material multilayer structure.Secondly,this article introduces the method of measuring and calculating Poisson's ratio in the experiment,and compares and analyzes the same multi-layer structure with different porosity meshes and the same kind of porosity different sandwich mode meshes in the compression process through uniaxial compression test and simulation comparison.The change of elastic modulus,Poisson's ratio and shape memory effect of the structure,so as to analyze the influence of porosity and interlayer method on the mechanical properties of the grid structure,and further verify that the in-plane modulus and Poisson's ratio can be controlled by the size of the structure.Subsequently,the influence of the introduction of the highly elastic polymer TPU interlayer on the shape memory effect of the pure shape memory polymer PLA was analyzed.At the same time,the grid models with different porosities and different multilayer structures are programmed with different strains to verify the programmability of the modulus and Poisson's ratio of the multilayer grid structure described in Chapter 3.Finally,on the basis of the previous paper,this paper continues to study the mechanical properties of multi-layer structure under the action of displacement compression load in different temperature environment,and the change rule of deformation mode of multi-layer structure after changing the loading strain rate in the same temperature environment.