Constitutive Model Of Woven Fabric Reinforced Shape Memory Polymer Composites

Shape memory polymers(SMPs),which can recover their original shape under specific stimulation,have attracted attention in biomedical,aerospace,flexible electronics and other fields.In order to improve the mechanical properties of shape memory polymers,it is usually necessary to add reinforcing phases(particles,fibers,etc.).In order to predict the mechanical behavior of fabric-reinforced shape memory polymer composites and provide guidance for practical application,the constitutive model of fabric-reinforced shape memory polymer composites is studied in this paper.In chapter 2,based on the phase transition model of shape memory polymer,considering the influence of strain state on the formation process of glassy state,the deformation gradient evolution equation of frozen glassy state was modified,and the constitutive model of shape memory polymer was established.The identification method of model parameters was established through tensile experiments at different temperatures and strain rates.The rubber state parameters were obtained by tensile curve fitting of a single strain rate.The glassy state parameters were determined by the tensile curves with two groups of different strain rates.The volume fraction was obtained by fitting the elastic modulus at different temperatures.In chapter 3,ABAQUS software is redeveloped to realize the numerical simulation of constitutive model.By means of analytical and numerical methods,the expression of stress and the derivative of stress to strain under large deformation is obtained and the user-defined material subroutine is written.The finite element model of uniaxial tensile and shape memory cycle of shape memory polymer under different temperatures and strain rates was established and calculated.The simulation results were compared with the experimental results to verify the validity of the constitutive model of shape memory polymer.In chapter 4,the fabric is homogenized into a macroscopic continuous structure and the free energy function is given based on the continuum mechanics framework.Considering the effects of mechanical properties,geometric para meters and weaving mode of the fiber bundle,the analytical expressions of equivalent bulk modulus and tensile coefficient in free energy were obtained.The constitutive model of fabric reinforced shape memory polymer composites was constructed by combinin g the established shape memory polymer model with the fabric constitutive model by the classical mixing law.The uniaxial tensile numerical simulation of the material was carried out by ABAQUS software and compared with the experimental results to verify the validity of the fabric reinforced shape memory polymer constitutive model.