Study On Deformation Behavior Of Self-curling Structurs Of 4D Printing Shape Memory Polymer

4D printing refers to the complex three-dimensional structures that are printed.This paper studies the deformation behavior of 4D printed shape memory polymer self-curling sheet is studied.4D printing is a combination of traditional 3D printing and smart materials.By applying different environmental incentives to the printed complex threedimensional structure,the shape,performance,and function of the printed structure can be adjusted in the time dimension.Since its appearance,4D printing has always been a hot spot in the field of additive manufacturing.According to the structural shape change during the 4D printing process,the thesis deeply studied the deformation behavior of the self-curling structure of 4D printing.In this paper,the mechanism of shape change in the 4D printing process is studied,and the deformation behavior of the self-curling sheet of 4D printing shape memory polymer is studied.First,the mechanical constitutive equation of 4D printing shape memory polymer is studied,and the constitutive equation and temperature-dependent behavior of the material are derived and analyzed based on the viscoelasticity of the existing polymer.The one-dimensional constitutive relationship was established and extended to three-dimensional,the three-dimensional constitutive model was discretized and the finite element program was written.Based on this,the thermo-mechanical behavior in the 4D printing process is described,and qualitative and quantitative analysis is provided.Deduction of the stress-strain relationship for component-level prints.Then,this paper verifies the proposed mechanics model by experiment.The 4D printed shape memory polymer was mechanically characterized.The dynamic mechanical properties and glass transition temperature of the polymer material were obtained by dynamic thermomechanical analysis(DMA)and differential scanning calorimetry(DSC),and the material was measured by the differential method.The linear expansion coefficient of the material is stretched at different temperatures to characterize the viscoelastic properties of 4D printing materials.After characterizing the printing material,a printing model is established for testing,and compared with the previous mechanical model.In the experiment,the printing temperature,speed and other parameters are controlled,data fitting is performed,the influence of printing parameters on the effect of deformation variables is explored,and the rationality of the constructed model is analyzed.Finally,based on the previous theory,the printing parameter control experiment of the 4D printing sheet was carried out,which provided the theory and data that can be referred to for the design of the curling structure.Through a series of experiments,the proposed mechanical model was tested and verified.Through the control of printing temperature,speed and other parameters,the influence of printing parameters on structural deformation is explored.Finally,the topological structure model was designed,and the design method and the aforementioned theories were verified by printing experiments on typical bending or curling structures such as thin plates,island bridge structures and flexible gripping structures.