Study On The Thermal Contact Conductance Between Carbon Fiber Reinforced Thermoplastic Composites

In recent years,carbon fiber reinforced thermoplastic composites have been widely used in aerospace,mechanical engineering,and microelectronic packaging with their advantages of light weight,high toughness,and easy processing.However,the surface of parts is relatively rough,so there is thermal contact resistance between contact surfaces,which brings challenges to the heat transfer process of contact interfaces in practical applications.Thermal contact conductance(TCC)is an important parameter in component design and application.It is of great practical significance to measure the TCC between composite materials and explore its influencing factors for solving practical engineering heat transfer problems.Based on the principle of one-dimensional heat conduction,an experimental system was designed and built to measure the TCC parameters of composites by steady-state method.The thermal conductivity,glass state transition temperature,melt crystallization behavior,and microstructure of carbon fiber reinforced polyamide 12composites(CF/PA12),which are widely used in additive manufacturing,were observed experimentally.The effects of interface temperature,contact pressure,surface roughness,CF content and orientation on the TCC were systematically analyzed.It was found that the TCC increased with the increase of the interface temperature.When TCC>1400W/m~2K,the change rate of TCC increases significantly at the glass transition temperature due to a sharp decrease in the elastic modulus.Under pressure,both elastic and plastic deformation exist on the material surface.A larger contact pressure achieves a larger TCC,but its tendency to change gradually decreases with increasing pressure.The number and height distribution of convex peaks in the surface morphology are the key factors affecting the TCC,and in general,a less rough surface corresponds to a higher TCC.Surface roughness is coupled with temperature and pressure in the interfacial heat transfer of the composite,with roughness having the greatest effect on the TCC,contributing up to 75%.There is an interaction between CF content and orientation on TCC between composites,as it affects both surface roughness and internal heat conduction of the material.When the CF direction is parallel to the heat flow direction,the axial thermal conductivity is enhanced but the surface roughness increases,leading to an increase in TCC with increasing CF content.While when the CF direction is perpendicular to the heat flow direction,the surface is flatter but the radial thermal conductivity is enhanced,resulting in a decrease in TCC with increasing carbon fiber content.On the whole,the interfacial heat transfer characteristics of composite materials are complex and there are many influencing factors.This study provides TCC reference data for engineering design,which is conducive to improving the design accuracy of composite components,and has certain guidance and reference significance for its additive manufacturing process and practical engineering application.