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.
Low-temperature thermal expansion of PEEK, HTA and some of their composites reinforced with carbon fibres
Abstract The thermal expansion of poly(ether ether ketone), a modification of poly (ether sulphone) and carbon fibre reinforced composites of these polymers has been measured over the range −153 to 27°C with a push-rod diameter. Where other measurements are available for comparison, agreement is obtained within experimental scatter. Some multidirectional composites are tested and the measured values of thermal expansion are explained qualitatively. It is thought that the specimen size has had a significant effect on these results. The longitudinal and transverse coefficients of thermal expansion of Hercules AS4 fibre have been calculated.
Elastic-plastic analysis of deformation induced by thermal stress in eutectic composites: I. theory
Understanding the deformation of eutectic composites under conditions of changing temperature with or without externally applied loading is important to the utilization of these materials. Here a method of calculating elastic-plastic deformation parameters in such materials is derived and its use demonstrated. The method uses stress equilibrium, strain continuity, and component constitutive relations to derive expressions for matrix stress as a function of temperature during heating and cooling or hold time at constant temperature. From that quantity several deformation parameters of interest can be calculated. Because numerical techniques must be used to determine solutions, great flexibility is available in the selection of cycling conditions and material constants. An illustrative calculation is presented and its results are discussed.