Study On Interface Parameters Of Composite Materials With Consideration Of The Effect Of Thermal Stresses

There are many factors which produce an effect on the property of compositematerial, whereas the situation of composite material interface and the distribution ofthermal stress in the composites are the most important. Owing to the difference ofmechanical properties between matrix and reinforcement, there is a stress concentrationphenomenon in the interface, which is one of the main reasons of composite materialfailure. While the thermal stresses due to the difference in coefficient of thermalexpansion between matrix and reinforcing during the manufacturing process, do play animportant role in the properties, sometimes the thermal stresses can even accelerate thefailure of composites. In the condition of imperfect interface, the neutral inclusions donot disturb the prescribed uniform stress field in the surrounding elastic body and caneliminate stress concentration phenomenon. Therefore, to study the interface parameterswhich satisfy the neutral inclusion conditions and design it with consideration of theeffect of an initial thermal stress field is of great important for improving the compositesproperties.In this paper, the distribution of thermal stress and displacement fields in thecomposites are obtained. In plane deformation, in the case of the cross-section ofreinforcing is circle and elliptic, according to the condition of imperfect interface, theconditions on the existence of neutral interface for reinforcing in isotropic andtransversely isotropic material are derived respectively. On these bases, we establishedthe model of structural interface and obtained the structural interface parameters whichsatisfy the neutral conditions, and the main factors that have effect on interfaceparameters have been discussed.Form the study, it indicated that the interface parameters are the functions ofposition along the boundary for cross-section of reinforcing is circle and elliptic andrelated to the mechanical properties of the components, the given stress and the thermalstresses. It also revealed that it has the similar form of expression between reinforcing inisotropic and transversely isotropic. It found that the structural interface parameters aredependent on the number of spars, the thickness of interface and the ratio of elasticconstants between the components. This paper gave the structural interface parametersand the laws effected by the number of spars, the thickness of interface and the ratio ofelastic constants for the reinforcing in isotropic and transversely isotropic withcross-section is circle and elliptic in plane deformation, which providing a basic theoryfor neutral interface design of composite materials.