Theoretical Study On The Influencing Factors Of The Thermodynamic Properties Of Nanoparticle Reinforced Composites

The nanoparticle reinforced composite materials have many excellent properties,with which the traditional materials with one component cannot be compared,and these composite materials have more and more applications in various fields.However,due to the properties of nanoparticles themselves,nanoparticles usually agglomerate in the matrix,which will have a significant impact on the thermodynamic properties of composites as a whole.In the same way,the interphase layer formed between the matrix and the inclusion has a significant influence on the thermodynamic properties of the composite.Based on the research method of mesomechanics,the influencing factors of the thermodynamic properties of particle reinforced composites are studied.In this paper,several kinds of nanoparticles were selected as reinforcement materials and epoxy polymer as matrix materials.Based on the size,distribution and interphase of the reinforcing material,the equivalent inclusion theory in microscopic mechanics and the Mori-Tanaka method are used to analyze and study the thermodynamic properties of nano-particle reinforced composites.According to the aggregation mechanism of nanoparticles,a micromechanical model of the agglomeration of nanoparticles is established.All parts of the composite are redivided: the agglomerated nanoparticles are regarded as spherical inclusions,and the uniformly dispersed nanoparticles and some of the original matrix are regarded as new hypothetical matrix.First,two agglomeration parameters are introduced to characterize the degree of agglomeration of nanoparticles.Combined with the Mori-Tanaka method,the expression of thermal expansion coefficient of nano-particle reinforced composites is derived to predict the influence of different agglomeration degree on thermal expansion coefficient of nano-particle reinforced composites.Second,porosity is introduced to predict the effect of porosity on the thermal expansion coefficient of nano-particle reinforced composites.Then,on the basis of previous research ideas,the interphase is introduced between the nano-particles and epoxy resin polymer matrix for considering the effects of interphase thickness,different nano-particle stiffness and particle sizes.Moreover,a mesomechanical model of nanoparticle agglomeration,which includes the interphase is established to further study the effects of nanoparticle agglomeration,nanoparticle stiffness and interphase characteristics on the thermal conductivity of nanoparticle reinforced composites.Finally,the influences of porosity on the thermal conductivity of nanoparticle reinforced composites are studied by using the effective medium theory proposed in the present investigation.