Research On Constitutive Model Of Thermally Induced Shape Memory Polymer-based Woven Fabric-reinforced Composites

As a smart material,the thermally induced shape memory polymer(SMP)can change shapes on their own under stimulus of temperature variation from outside environment.The special material property makes the thermally induced SMP have a great application potential in modern engineering area.Adding reinforcements to SMP matrix makes the shape memory polymer composite(SMPC).Among the reforinforcements,woven fabrics can enhance the SMP in multiple derections obviously and the deformation limit is large.So,thermally induced shape memory polymer-based woven fabric-reinforced composites have larger application value in engineering applications.At present,the application of smart structures based on the SMPC is more and more extensive,so it is growingly urgent to carry out fundamental research and construct related constitutive model describing and predicting the thermomechanical and shape memory properties of these materials in actual application environment aiming at providing theoretical support for the design and optimization of smart structures and their application processes.A thermo-induced shape memory polymer-based woven fabric-reinforced composite is prepared and its systematic mechanical and shape memory experiments are conducted.And the influence of carbon fabric reinforcement on the mechanical and shape memory properties of the material is investigated.Overall,the addition of carbon fabric improves the mechanical performance.The enhancement effect of the fabric in uniaxial tension decreases with temperature increasing,but it is complicated in bias-extension.For the shape memory performance,the addition of carbon fabric leads to the obvious residual strain and prevents the complete recovery.The recovery in bias-extension initiates the most late,and the recovery process in uniaxial tension is complex.But the maximum recovery rates of the composite and polymer are almost identical.A finite element lamination model for the thermo-induced shape memory polymer-based woven fabric-reinforced composite is proposed.In this model,SMP matrix and woven fabric reinforcements are represented by continuum element and shell element,respectively,and bonded to each other with co-node connection.So,the entire thermomechanical property of the SMPC can be decomposed into matrix and reinforcement and the two parts can be described separately,which simplies the construction of constitutive model and makes the model easy to be used in finite element simulation.The experiment data of a bending shape memory cycle is used to verify the model.Afterwards,the lamination model is used to simulate shape memory cycle processes of a tube structure with different deformation modes.The simulation results show that the tube structure has good shape memory property in all deformation modes.So,the SMPC reinforced by woven fabrics have a great application potential in deployment structure area.A 3D finite-strain viscoelastic constitutive model for the thermally induced SMP is proposed based on the viscoelasticity theory of polymer and phase transition concept.The model describes the SMP by decomposing the whole material behavior into thermal and mechanical parts.The thermal part represents the thermal expansion or contraction and the mechanical part represents the viscoelastic mechanical property of the material.The expressions of the second Piola-Kirchhoff stress and viscoelastic velocity gradient are derived based on thermal energy decomposition and the second law of thermodynamics in the Clausius-Duhem inequlity form.The introduction of phase transition concept simplifies the mathematical expressions of the structure and stress relaxation mechanisms of polymers and makes the material parameters in the model easy to be determined.Three sets of experimental data in different shape memory cycles are used to validate the proposed model.The simulation results have a good consistency with experiment results,which demonstrates the effectiveness of the model adequately.A 3D finte-strain anisotropic viscoelastic constitutive model for thermoresponsive shape memory polymer-based woven fabric-reinforced composites is constructed based on the developed 3D finite-strain viscoelastic constitutive model for the thermally induced SMP and a previously developed anisotropic hyperelastic model for woven fabrics.The model decomposes the whole thermomechanical property of the composites into isotropic viscoelasticity and anisotropic hyperelasticity coming from matrix and reinforcements,respectively.And the constitutive equations are derived based on the second law of thermodynamics.The carbon fabric-reinforced thermally induced SMPC prepared and its physical experiment results are used to verify the model.The simulation results have an excellent consistency with the experiment data,which demonstrates that the proposed model can predict the anisotropic mechanical and shape memory properties of the composites accurately.