MATERIAL PROPERTY PROJECTIONS FOR 3-D GRAPHITE FIBER REINFORCED ALUMINUM MATRIX COMPOSITES FOR THERMAL MANAGEMENT

摘要

Mathematical models of 3-D graphite fiber reinforced aluminum matrix materials were constructed in order to provide guidance in the design of this class of metal matrix composites (MMCs) for specific thermal management applications. Measured data on materials of this type were first used to verify the math models, in order to provide confidence in property projections for different fiber architectures, different fiber volume fractions, and different aluminum alloys. Projected properties in three orthogonal directions included the thermal conductivities, the elastic Young's moduli, and the coefficients of thermal expansion. In addition, there is great interest in these materials in applications in which they serve as both a heatsink and as a CTE constraint material for electronic components mounted on them. Typically, the temperature range over which the CTE constraint is required is from 233 K to 373 K. By means of finite element analyses of unit cell models, by investigating aluminum matrix stress states during thermal loadings, the required alloy yield stress to obtain a constant CTE over this temperature range was calculated for different candidate alloys and for different preform architectures and fiber volume fractions. Thus guidance in the appropriate selection of the aluminum alloy type in order to achieve desired material properties (thermal conductivities, CTEs constant over a specific temperature range) is a primary function of the mathematical material models.