Research Of Thermal Contact Effect On Metal/composite Mechanical Connection

Composite material is widely used in aerospace industry due to its advantages, such as high specific strength, high stiffness, convenience for design and molding. There is a need to connect it to metal materials in the course of its use. Three connection forms of metal/composite structures are respectively mechanical connection(bolt or rivet),glued and hybrid connection. Among them, the bolt connection is the most common form which is suitable for transmitting high loads and applying in the reliable components. Because of thermal properties differences between metal and composite, TCR(thermal contact resistance) between contact surfaces and temperature boundary conditions, the temperature field of metal/composite connection is no uniform. When connection subjected to mechanic loads and temperature loads simultaneously, its stress distribution will be very complicated for the thermal expansion coefficient difference between metal and composite materials. So it is necessary to conduct intensive research for the metal and composite thermal contact resistance.The main research works of this article are as follows:1. Building three dimensional contact peak of random distribution of two solid materials connection model. This model use method of computational micromechanics, obtain steady temperature distribution of representative volume element by finite element analysis, and obtain solutions of the TCR by the heat transfer theory.2. Using this model to study the differences in material properties of the contact, the contact interface characteristic asperity, roughness of material impact on the thermal contact resistance. The results show that the contact area and the roughness of the material has a greater impact on the thermal contact resistance, the higher the asperity, the greater the contact resistance; the greater the actual contact area, the smaller the contact resistance is.The features of rough peak in contact interface could impress TCR.3. Then established finite element model of the aluminum/CFRP(Carbon Fiber Reinforced Polymer) connected by bolts. Study the effects of TCR on the temperature field of connection by considering TCR and don’t considering TCR thermal analysis on the model. Results showed that the temperature of composite material plate which considering the TCR are significantly lower than the temperature of composite plate which not considering TCR, and temperature field in aluminum alloy plate have little influence by TCR. The temperature of bolt which considering TCR change linearly along the bolt axis, the temperature of bolt which not considering TCR shows high temperature values in alloy plate region and change linearly in composite plate region.4. Thermal mechanical coupling analysis are carried out both on the models which considering TCR and which not considering TCR. Thus, an effect of TCR on stress distribution on connections is carried out. Results show that TCR would take great impact to the equivalent stress and contact stress of the connections.Proposed calculation of bi-material and finite element method of thermal contact resistance under non-uniform temperature field finite element simulation of metal-composite connectors as well as to connect the TCR effects of stress field has a guiding role for engineering applications.