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A combined analytical/experimental study has been undertaken to in vestigate the effective thermal conductivity of hybrid composite materials. The analysis utilizes the equivalent inclusion approach for steady state heat conduction (Hatta and Taya, 1986), through which the interaction between the various reinforcing phases at finite con centrations is approximated by the Mori-Tanaka (1973) mean field approach. The multiple reinforcing phases of the composite are modeled as ellipsoidal in shape and thus can simulate a wide range of microstructural geometry ranging from thin platelet to con tinuous fiber reinforcement. The case when one phase of the composite is penny-shaped microcracks is studied in detail. Multiphase composites consisting of a Kerimid matrix and Al 2O3 short fibers and Si3N4 whiskers were fabricated and after a careful study of their microstructure, their thermal conductivities were measured. Analytical predictions are shown to be in good agreement with experimental results obtained for the Al2O 3/Si3N4/ Kerimid short fiber composites.

To reinforce the interlaminar of laminated composites, a novel method was proposed by the authors [1]. In this method, whiskers were added in the matrix resin to reinforce the interlaminar, and the orientation of the whiskers were magnetically con trolled to improve the reinforcement efficiency. In this paper, mode I (cleavage) inter laminar fracture toughness was shown to be remarkably improved as a result of the addi tion of oriented whiskers to the direction of the plate thickness. Whereas, mode II (inplane shear) interlaminar fracture toughness and interlaminar shear strength (ILSS) were not raised. Parameters of interlaminar reinforcement such as volume fraction of whiskers and whisker dimension were also discussed for exploring the optimum condition.

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