Viscoelastic Multiscale Meso-mechanical Model Of Composite Materials And Its Application

The excellent mechanical properties of composite materials have broad application prospects in civil engineering,bioengineering,aerospace and other fields.In recent years,the study of mechanical properties of fiber reinforced composites has become a hot topic in the field of composite mechanics.Whether this type of composite can maximize mechanical properties such as high specific strength and high specific stiffness depends largely on the structural form of the material itself,the characteristics of the reinforced fiber phase and the dispersion form.In order to consider the viscoelastic effects of composite materials,this paper takes biological composites of cortical bone and dentin as research objects,and considers the multi-scale structure and fiber distribution characteristics of fiber-reinforced composite materials.The locally-exact homogenization theory(LEHT),Mori-Tanaka,homogenization theories of random platelets composite(HTPRC)and polymer-clay nanocomposite(PCN)homogenization method are used to study the multi-scale structure levels of fiber reinforced composites from micro to macro and the influence of multi-scale structure on the effective modulus(elastic modulus,shear modulus,bulk modulus)and dynamic viscoelastic response(storage modulus and loss modulus)of the composites.This paper specifically carried out the following research work:(1)The meso-mechanical model of viscoelastic composites was established,and the mechanical model was combined with the homogenization theory.By simulating the volume fraction and distribution between fiber and matrix in each level,the effective modulus of viscoelastic composites from micro to macro level was predicted layer by layer.In this paper,the meso-mechanical model of cortical bone and dentin was established,and the local stress field in the cell was reconstructed by taking the component volume fraction as a variable,and the effective modulus of the composite was predicted.The predicted results are compared with the experimental data and the classical homogenization theory.The results show a good agreement,which verifies the validity and accuracy of the theory and the model.It means that the proposed model can be applied to other composites with viscoelastic characteristics(2)The effect of different levels of structure on the macroscopic viscoelastic effective modulus and local response of cortical bone and dentin was studied.Based on the homogenization theory and multi-scale meso-mechanics model,the macroscopic dynamic viscoelastic response was predicted,and the influence of each level on the macroscopic level was quantified,so as to analyze the influence of each level structure on the macroscopic viscoelastic effective modulus and local response.On this basis,the effects of aging conditions and hydration conditions on the effective viscoelastic modulus of cortical bone and dentin were predicted and analyzed.The results clearly showed that the viscoelastic response of cortical bone and dentin was closely related to its multi-scale hierarchical structure.