Enhanced Thermal Conductivity of Composite Materials by Filling Sheet and Fiber Under Effect of Filler Contact

Abstract The most common nongranular fillers are sheet and fiber. When they are distributed along the heat flux direction, the thermal conductivity of the composite increases greatly. Meanwhile, the filler contact also has a large effect on the thermal conductivity. However, the effect of filler contacts on the thermal conductivity of the composite with directional fillers has not been investigated. In this paper, combined effects of the filler contact, content, and orientation are investigated. The results show that the effect of filler orientations on the thermal conductivity is greater than filler contacts in the low filler content, and the exact opposite in the high filler content. The effect of filler contacts on fibrous and sheet fillers is far greater than cube and sphere fillers. This rule is affected by the filler contact. The filler content of 8% is the ideal percolation threshold of composites with fibrous and sheet fillers. It is lower than cube filler and previous reports. The space for the thermal conductivity growth of composites with directional fillers is still very large. The effect of the interfacial thermal resistance should be considered in predicting the thermal conductivity of the composite under high interfacial thermal resistances (>10−4).