Thermal conductivity and thermal expansion of graphite fiber/copper matrix composites
The high specific conductivity of graphite fiber/copper matrix (Gr/Cu) composites offers great potential for high heat flux structures operating at elevated temperatures. To determine the feasibility of applying Gr/Cu composites to high heat flux structures, composite plates were fabricated using unidirectional and cross-plied pitch-based P100 graphite fibers in a pure copper matrix. Thermal conductivity of the composites was measured from room temperature to 1073 K, and thermal expansion was measured from room temperature to 1050 K. The longitudinal thermal conductivity, parallel to the fiber direction, was comparable to pure copper. The transverse thermal conductivity, normal to the fiber direction, was less than that of pure copper and decreased with increasing fiber content. The longitudinal thermal expansion decreased with increasing fiber content. The transverse thermal expansion was greater than pure copper and nearly independent of fiber content.
A review of the thermal conductivity of graphite reinforced metal matrix composite materials
The characteristics of graphite reinforced metal matrix composites are increasingly important in a wide range of technologies. This study presents a review of the experimental and analytical investigations of the thermal conductivity of these materials. Most of the published studies deal with the mechanical properties of these materials, however, there have been limited studies characterizing the thermal properties of some of these materials. The effective thermal conductivity is of particular importance for design and applications and experimental data are summarized and compared with accepted models of composite properties. On the basis of this review, it is evident that the thermal properties of graphite fiber reinforced metal matrix composite materials have not been adequately investigated. Modeling techniques based on limited experimental data have identified some of the important parameters, but no single model adequately predicts either the longitudinal or the transverse conductivity of these materials. The study concludes with recommendations for emerging and continuing areas of investigation.
Elastic-plastic analysis of deformation induced by thermal stress in eutectic composites: II. thermal Expansion
In part I a theory was developed to analyze the deformation produced in eutectic composites by temperature changes. Experimental determinations of the coefficient of expansion are used here to test the predictions of that theory. Measurements of length versus temperature in the absence of external stresses were made for Al-Al3Ni, Al-CuAl2, and Sb-Cu2Sb eutectic composites, and for monolithic 6061 Al. Hysteresis loops in the graph of composite coefficient of expansion vs temperature are seen when the expansion coefficients of the phases are different and plastic deformation occurs. The nature of the hysteresis is shown to depend upon heating and cooling rates, prior history and the relative values of the matrix and reinforcement expansion coefficients. The theory correctly predicts these qualitative effects. In Al-Al3Ni the available component data justify a quantitative comparison of calculated and experimentally determined coefficient of expansion-temperature curves. The values compare well, further verifying the analytical approach.