National research council resident research associate; currently, material scientist, Analytical Services and Materials, NASA Langley Research Center, Hampton, VA
Senior research engineer, NASA Langley Research Center, Hampton, VA
A systematic experimental evaluation of whisker- and particulate-reinforced aluminum matrix composites was conducted to assess the variation in tensile properties with reinforcement type, volume fraction, and specimen thickness. Each material was evaluated in three thicknesses, 1.8, 3.18, and 6.35 mm, to determine the size, distribution, and orientation of the reinforcements. This information was used to evaluate several micromechanics models that predict composite moduli. The longitudinal and transverse moduli were predicted for 15 volume percent (v/%) SiCp-reinforced aluminum and for 15 and 30 v/% SiCw-reinforced aluminum. The Paul, Cox, and Halpin-Tsai models were evaluated.
The Paul model gave a good upper bound prediction for the particulate-reinforced composites but underpredicted whisker-reinforced composite moduli. The Cox model gave good moduli predictions for the whisker reinforcement but was too low for the particulate. The Halpin-Tsai model gave good results for both whisker- and particulate-reinforced composites. An approach using a trigonometric projection of whisker length to predict the fiber contribution to the modulus in the longitudinal and transverse directions was compared to the more conventional lamination theory approach.
Paper ID: CTR10221J