High Through-thickness Thermal Conductivity Composites Based on Three-Dimensional Woven Fiber Architectures

Composites based on laminates of uniaxial or biaxial fiber reinforcements exhibit low through-thickness thermal conductivity, due to low matrix thermal conductivity and the number of interfaces in the thermal path. For applications near heat-generating components, the use of laminate composites in the surrounding structure can be limited by this inability to transport heat through the thickness. Three-dimensional orthogonal weaving provides an efficient, cost-effective method of placing high thermal conductivity yarns in the through-thickness Z direction of a preform to yield structural composites with high through-thickness thermal conductivity and with in-plane strength or stiffness comparable to laminates. Three basic research efforts investigated the efficacy of this approach: 1) weaving trials to determine the ability to three-dimensional orthogonal weave pitch carbon fibers and plied copper wires in the Z direction of the preforms, 2) through-thickness thermal conductivity testing of composites based on three-dimensional preforms, and 3) thermal modeling to describe several of the phenomena observed during thermal conductivity tests. During the testing, composites based on the three-dimensional orthogonal preforms with Z fiber volume fractions of only 5.5% measured a 12-fold increase in through-thickness thermal conductivity over a laminate composite, 8.4 versus 0.7 W/m K.