DETERMINATION OF THERMAL PROPERTIES FOR WOVEN-MAT COMPOSITE LAMINA WITH FINITE ELEMENT METHODS

摘要

Models are presented for determination of thermal conductivity of a composite lamina manufactured with woven fiber mats. In analyzing the cure cycle of a composite part, the common practice has been to use weight-averaged thermal properties. The limitation of this approach is apparent when one finds that thermal conductivity calculated for fiberglass/epoxy composite is very close to thermal conductivity of carbon/epoxy composite. This happens when composite parts with the same fiber volume fraction are considered. The reason for this is that in employing weight-average formulations the effect of fiber thermal conductivity is overshadowed by the density of the constituents. To overcome this problem, one needs to take another approach. In this investigation finite element analysis is performed on a unit cell representing the weave pattern of the lamina to determine thermal conductivities of fiberglass/epoxy and carbon/epoxy composite lamina. The resulting thermal conductivities are very different for the two composite types. These results make more physical sense since thermal conductivity of carbon fibers is many times larger than that of fiberglass fibers.