Research On Thermal Conductivity Modification And Mechanism Of Carbon Fiber Reinforced Resin Composites

Carbon fiber reinforced resin composites(CFRP)are widely employed in aerospace,naval equipment,high-speed trains,automobile manufacturing and other fields due to their excellent comprehensive properties,such as high specific strength,chemical resistance,low thermal expansion and designability.They are regarded as the ideal candidate for the new generation multi-functional material with high-performance and light-weight.However,the traditional unidirectional CFRP generally exhibits low thermal conductivity in through-thickness direction,which greatly limits their application under thermal conditions.Therefore,it is important to improve the through-thickness thermal conductivity of CFRP without changing the structural integrity.In this paper,two kinds of thermal conductivity modification methods: pinned enhancement and micro-nano filler enhancement,are used to improve the thermal conductivity of CFRP in through-thickness direction.The research suggest that the thermal conductivity of CFRP is improved obviously,but the mechanical properties are weakened to a certain extent.For modified composite with pinned copper bars,an modified prediction model proposed show a better agreement with the experimental data.By the temperature field analysis of composites,the influences of the characteristic length and arrangement of pinned copper bars on thermal conductivity are explored,and the mechanism of thermal conductivity modification is revealed.Moreover,the weakened mechanical property of pinned modified composites is due to the fracture failure between pinned holes.For modified composite with micro-nano fillers,the surface pretreatment process of carbon fiber prepreg is studied.The mechanism of thermal conductivity modification is revealed based on the dispersion distribution of fillers in the composites.Four theoretical prediction models of thermal conductivity are proposed considering the overall distribution of fillers within composite,the local distribution of fillers within prepreg lamella,and the degree of formation of thermal network.It is found that the parallel prediction model of the overall thermal resistance network is most consistent with the experimental results.Delamination failure becomes the dominated reason for the decrease of mechanical property of composites.In conclusion,the two methods of thermal conductivity modification both can better coordinate the load-bearing and thermal conductivity of composites.However,it is expected that the comprehensive performance can be further improved by metal coating treatment or affinity pretreatment of fillers,which can better meet the application requirements of mechanical-thermal integration of composites.