Thermo-Chemomechanical Coupled Constitutive Model And Numerical Analysis Of Polymer Matrix Composites

Polymer matrix composites are widely used in biomedicine,chemical industry,intelligent control,energy power and electronic information fields due to their multiple structures and special functional groups.When the composite is in complex external environment(such as heat,electricity,magnetism,force,light,chemical reaction,etc.),the materials will be subject to the coupling effect of multiple physical fields,thus showing complex response states and coupling properties.Polymer matrix composites and structures are more widely used in engineering applications where they are often in service in wet thermal/chemical solution environments,requiring the development of thermo-chemomechanical coupled constitutive models,experimental tools and solution methods to investigate the swelling behavior and thermomechanical properties of polymer matrix composites in chemical environments.Therefore,this paper develops the thermo-mechanical coupled large deformation constitutive model based on the continuum mechanics theory according to the polymer matrix composites in the chemical environment,and establishes the mass transfer field model coupled with chemical reaction and mass diffusion.The entropy elastic properties and chain slip behavior of microscopic molecular chains are considered.The macroscopic continuous finite deformation theoretical model based on microscopic physical mechanism is developed,and the cross-scale viscoelastic constitutive model coupled with multiphysical and chemical processes is formed.Finally,this paper discusses the evolution law of each component of the system and the change process of material state under the chemical reaction and diffusion through finite element simulation and numerical calculation.In-depth thermo-mechanical coupling is analyzed to develop the design and numerical simulation of self-assembly structure driven by thermo-mechanical coupling.The main work of this paper are as follows :The second chapter focuses on thermodynamic coupling behavior of polymer matrix composites and develops a thermodynamic constitutive model for mass diffusion and chemical reactions to meet the requirements of thermodynamic consistency.Firstly,the evolution process of material components of polymer matrix composites under the thermodynamic coupling environment is elaborated in detail.By defining the deformation gradient of composites and constructing the conservation equations of mass,momentum and energy in the diffusion-chemical reaction system,the governing equations of state variables of polymer matrix composites are obtained.The constitutive relation and dissipation inequality of polymer matrix composites are given by means of entropy increase theorem.The third chapter focuses on the thermodynamic coupling constitutive relationship of polymer matrix composites.a cross-scale thermodynamic coupling constitutive model of polymer matrix composites has been established by introducing the deformation mechanism of material micro molecular chain.First free energy function of polymer-based composites is given,including elastic deformation and slip deformation mechanism with molecular chain entropy of crosslinked polymer mixed free energy function,diffusion and chemical reaction system free energy and free energy function,enhance fiber phase and dissipative inequality is deduced based on the second chapter gives integral constitutive equation of polymer-based composites,the evolution of variables in the system has also been studied.In chapter four,based on the cross-scale thermodynamic constitutive model of polymer matrix composites,the corresponding numerical algorithm is developed to simulate the dissolution process of epoxy resin matrix composites.The three-dimensional constitutive relationship of polymer matrix composit es was realized by user subunit program(UEL)of ABAQUS,and the influence of different material parameters on the thermodynamic coupling behavior of epoxy resin matrix composites was discussed.In chapter five,the simplified viscoelastic model considerin g mass diffusion is used to compare with the results of water diffusion experiment and water-triggered self-folding experiment of PVAc fiber composites,which verifies the accuracy and validity of the thermodynamic coupling constitutive model of polymer ma trix composites established in this paper.