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.
Anisotropic Thermal Diffusivity Measurements in High-Thermal-Conductive Carbon-Fiber-Reinforced Plastic Composites
This paper presents the temperature dependence of in-plane thermal diffusivity and anisotropy distribution for pitch-based carbon-fiber-reinforced polymers (CFRPs). The measurement was performed using the laser-spot periodic heating method. The samples were unidirectional (UD) and crossply (CP) CFRPs. All carbon fibers of the UD samples ran in one direction, while those of the CP samples ran in two directions. In both UD and CP CFRPs, from -80°C to +80°C, temperature dependence of thermal diffusivity values increased as temperature decreased. In this temperature range, the anisotropic ratio between the fiber direction and its perpendicular direction of the UD CFRP was 106 - 124. During the anisotropy distribution measurement, it was found that thermal anisotropy can be visualized by scanning the laser in a circle on the sample. The thermal diffusivity of the UD CFRP in the fiber direction was 17 times larger than that in the 15° direction, and the thermal diffusivity in the other directions was lower than that in the 15° direction. The anisotropy distribution for the CP CFRP reflected its inhomogeneous structure.
Development of polyamide curable modified epoxy novolac resins with improved adhesion and chemical resistance
Purpose – To prepare modified epoxy resins from resorcinol, cresol and phenol for improved adhesion and chemical resistance. To evaluate the properties of such modified epoxy resins.Design/methodology/approach – Epoxy novolac resins (ENRs) were synthesised by condensing epichlorohydrin with novolacs based on different types of substituted phenols for improving adhesion and chemical resistance. Various compositions were made by incorporating different proportions of polyamide resin. The chemical and adhesive strengths of the conventional epoxy and the modified epoxy resins were characterised.Findings – The modified ENR using substituted phenols showed significant enhancement of chemical and adhesive strengths over the conventional DGEBA resin. The modified ENR had an increased number of glycidyl groups (thus increased functionality) of resin, which was responsible for improved chemical and adhesive strengths over the conventional DGEBA resin.Research limitations/implications – The EPN resins used in the pr...