Thermal expansion of boron fiber-aluminum composites

Abstract

The linear thermal expansion of silicon carbide coated boron (BORSIC^®) aluminum composites was measured as a function of volume fraction fiber and angle with respect to the fiber axis. The measurements were made with a standard quartz tube-type dilatometer at a heating rate of 150°C per hr. Measurements were made between 25° and 300°C on 2024 aluminum alloy-BORSIC and 1100 aluminum alloy-BORSIC composites in the 0 and 90 deg fiber orientation as a function of volume fraction fiber. The axial test results are compared with several models found in the literature which predict composite thermal expansion. These predictions yield values which are higher than the measured expansion coefficients of the 0 deg composites. The discrepancy is assumed to be related to yielding in the matrix. The 90 deg composites are found to agree with the transverse thermal expansion coefficient relationship of Schapery (also Levin) which employs the Poisson ratio for each phase and the composite. The expansion coefficients of 2024 aluminum alloy-BORSIC composites containing 54 pct by volume fiber are given for fiber orientations of 0, 15, 30, 45, 60, 75, and 90 deg.