Double-inclusion Model And Its Application In The Study Of Effective Properties Of Graphene/polymer Composites

Graphene/polymer composites have excellent mechanical and thermal properties,which play an important role in manufacturing precision instruments,microelectronic devices,machinery and aerospace devices.The mechanical and thermal properties of graphene/polymer composites are affected by graphene dispersion and the interface.The theoretical quantitative analysis of the effects of graphene dispersion and interface on the effective properties of composites can provide a theoretical basis for the production of highperformance graphene/polymer composites.In this dissertation,the graphene sheets are regarded as flat ellipsoids with a slenderness ratio of zero.The double-inclusion model(DIM)is used to predicting the effective properties.For the classical DIM,when predicting the effective properties of macroscopic isotropic two-phase composite reinforced by ellipsoidal inclusions with a random orientation,the explicit expression of the effective properties cannot be given,because the properties of the reference medium are the effective properties to be solved;In the prediction of the effective properties of macroscopic anisotropic two-phase composite reinforced by ellipsoidal inclusions with a single orientation,there is no certain method to determine the outer layer ellipsoidity of the double-inclusion.We first developed and improved the classical DIM,and then,based on the improved DIM,we studied the effective thermal conductivity of reduced graphene(r GO)/montmorillonite(MMT)/polymer composites considering the effect of r GO agglomeration and MMT dispersion,and the sizedependent effective thermal conductivity of quantum dots(GODs)/polymer.The following results are obtained:(1)For a macroscopic isotropic two-phase composite reinforced by ellipsoidal inclusions with a random orientation,a new DIM reference medium modulus/thermal conductivity is proposed.In addition,the outer layer of the double inclusion is chosen as a sphere.The explicit expressions of strain/temperature gradient concentration factor and effective modulus/thermal conductivity are given.(2)For a macroscopic anisotropic two-phase composite reinforced by ellipsoidal inclusions with a single orientation,a method for determining the outer layer ellipsoidity of the double-inclusion is proposed.In addition,the reference medium property is taken as the volume average of inclusion and matrix property.The explicit analytical expression for the effective modulus/thermal conductivity is given.(3)Furthermore,for a macroscopic isotropic multiphase composite reinforced by ellipsoidal inclusions with a random orientation,using the DIM based on the new reference medium property,by decomposing the representative volume unit(RVE)of N+1-phase composite into the combination of N kinds of two-phase composites RVE,the explicit expressions of strain/temperature gradient concentration factor of N kinds of two-phase composites and the effective modulus/thermal conductivity of multiphase composite are given.(4)The mathematical interface model is introduced into the classical DIM,after that,the analytical expression of the effective thermal conductivity of ellipsoidal inclusion reinforced-composites considering the interface influence is given.(5)The effective thermal conductivity of r GO/MMT/polymer composite is studied.Firstly,using the proposed multiphase composites DIM,the effective thermal conductivity of ideal dispersed r GO and MMT reinforced polymer composite is obtained.Then,a parameter is introduced to describe the effect of r GO agglomeration,and a function to represent the effect of MMT dispersion.Secondly,the model parameter and function are determined by fitting the experimental data.Finally,the analytical expression of the effective thermal conductivity of polymer composites considering the effect of r GO agglomeration and MMT dispersion is given.(6)The size-dependent effective thermal conductivity of GODs/polymer composite is studied.A size-dependent GODs-polymer interfacial model is proposed.Using the DIM based on the mathematical interface,the analytical expression of the sizedependent effective thermal conductivity of GODs/polymer composite is given.