Simulation And Sensitivity Analysis On Shape Memory Behaviors Of Polyurethane And Its Carbon Fiber Composites

Shape memory polymers and their composites will recover to their original shape when exposed to stimuli such as light, electricity, temperature, magnetism, etc. Shape memory polymers and their composites are mainly used in deployable space structures (hinges and trusses), skin of morphing aircraft wings, biology and bionic instruments (such as intravascular stent in drug-controlled system, intelligent surgical suture), polymer textile and self-healing system.According to the 973 project about aircraft, to design simple but low cost intelligent deployable structures with high deployable efficiency are meaningful in real application. Shape memory materials can be used in aircraft with which self-unfolding is realized. Folding ratio of shape memory effect is improved when energy used in the shape memory cycle is reduced, which decrease the energy cost. From the aspect of engineering, shape memory polymers and their composites are much easier to be developed and optimized. They are special with low density, high deformation ratio, fast response and low cost. Therefore, research on related basic theory can provide a reference to the aircraft in our country.Although some linear and nonlinear models have been developed to predict the SME, there is still a huge gap between theoretical models and engineering applications. Moreover, the parameters of previous researches mostly aim at the theoretical analysis depending on tests like dynamic mechanical analysis, which are inconvenient for practical engineering applications. Furthermore, one-dimensional constitutive equations have been developed to effectively predict the properties and characteristics in shape memory cycles while lacking of 3D models required in engineering fields.(1) Numerical analysis of shape memory cycle with PU is carried out and the influence of heating rate on shape memory effect is discussed. The influence factors are analyzed through Morris sensitivity analysis.The relationship of stress-temperature-strain is established based on solid mechanics, thermodynamics, isotropic viscoelastic theory and molecular structure and properties. Thermal expansion is also involved. With the software COMSOL Multiphysics 4.3a, multi-physics fields are combined, followed by analysis of stress and strain changing with temperature in the shape memory process. In addition, the influence factors that have impact on shape memory effect is discussed based on this model.(2)Analysis of shape memory effect of carbon fiber-reinforced composite is carried out, and in the meanwhile the influence of fiber volume fraction is discussed. In addition, the influence factors are analyzed through Morris sensitivity analysis.The analytical model to analyze shape memory effect of carbon fiber-reinforced composite is established based on solid mechanics, thermodynamics, anisotropic viscoelastic theory, molecular structure and properties. Combined COMSOL Mlutiphysics 3.5a, coupling of solid mechanics part, thermodynamics part, anisotropic viscoelastic part is realized to simulate shape memory effect of carbon fiber-reinforced composite. In addition, the influence factors are analyzed through Morris sensitivity analysis.(3)Property test and experiment about shape memory effect are carried outThe material in this work comes from 621 institute, Beijing. DSC, DMA and stress relaxation test are carried out. Shape memory effect test is also designed to analyze the shape memory epoxy resin.