Thermal Residual Stress And Thermal Expansion Coefficient Analysis Of Two Kinds Of Micromechanics Models Of Composite Materials

The thermodynamic properties of composite materials have been the research direction,among which the thermal residual stress and thermal expansion coefficient are the most studied.In this paper,the thermal residual stress of fiber reinforced composites and the thermal expansion coefficient of three phase particle reinforced composites were studied by establishing different mesoscopic models,and the influencing factors were analyzed in detailIn order to solve the thermal residual stress of fiber reinforced composites,a classical dual cylindrical meso-mechanical model is established.Under the circumstance of temperature change,the matrix and the fiber will expand and elongate with the change of temperature and they generate corresponding thermal stress.The difference of thermal expansion coefficient between the matrix and the fiber will cause a displacement difference in the expansion process,but there is no such displacement difference in the actual process.This is due to an interaction between matrix and fiber due to bonding during the process of change,and the presence of this interaction enables matrix and fiber to remain bonded during expansion.Based on Hooke's law,the basic equation of stress and strain is obtained.For the elastic matrix,the shear stress in the matrix is inversely proportional to the distance of the fiber,and the axial shear stress equation is obtained.Considering the non-debonding condition between the substrate and the fiber,the deformation coordination condition of the contact surface between the fiber and the outer substrate is obtained.Since the residual stress is an equilibrium of internal stress,the equilibrium formula can be obtained and the thermal residual stress expression is also obtained after then.In this paper,an equivalent mesomechanical method for predicting the thermal expansion coefficient of composites is proposed,and a model with three phases for predicting the effective properties of particle reinforced composites is established.Compared with other models,this paper analyzes the influence of the thickness of the disbonding interface on the thermal expansion coefficient of the material.The influence of the length-diameter ratio and the volume fraction of particle inclusions on the thermal expansion coefficient are also studied,and some conclusions are presented.Based on Eshelby's equivalent inclusion theory,this paper uses Mori-Tanaka method to derive the formula of thermal expansion coefficient.The results show that the thermal expansion coefficient of the composite is sensitive to the thickness of the disbonding interface,the length-diameter ratio of particle inclusions and the volume fraction.By comparing the results obtained with existing data,it is found that the variation trend of thermal expansion coefficients is more consistent with those,and the results from the present investigation are more advantageous in some aspects.