Thermal conductivity of misaligned short-fiber-reinforced polymer composites

A fiber length distribution (FLD) and a fiber orientation distribution (FOD) usually exist in injection-molded short-fiber-reinforced polymer (SFRP) composites. In this article, the thermal conductivity of SFRP composites is studied in detail, taking into account the effects of the FLD and the FOD. The effect of fiber volume fraction on the composite thermal conductivity is also investigated. It is shown that the thermal conductivity of SFRP composites increases almost linearly with fiber volume fraction; it also increases with mean fiber length (or mean aspect ratio) but decreases with mean fiber orientation angle with respect to the measured direction. The latter two effects depend highly on the thermal conductivity of short fibers. The effects of mode fiber length and mode fiber orientation angle on the thermal conductivity of short (carbon) fiber reinforced polymer composites have also been studied. The composite thermal conductivity increases marginally with the increase of mode fiber length but lightly with the increase of mode fiber orientation angle. Moreover, comparison of the present model is made with existing theories in predicting the thermal conductivity of SFRP composites. Finally, the present model is applied to published experimental results and the agreement is found to be satisfactory.