Dynamic Young modulus of a ceramic-aluminum particle-reinforced composite: measurement and modeling

The authors studied the dynamic Young modulus, E, of a particle-reinforced aluminum alloy. The particles consisted of Al₂ O₃ spheres with average sizes of 30, 45, and 100 μm. The measurement methods consisted of megahertz-frequency pulse-echo superposition and kilohertz-frequency standing-wave resonance. The modeling method consisted of taking the long-wavelength limit of the ensemble average of the sound velocity of plane waves scattered by a well-stirred distribution of spheres. Input to the model consists only of the particle and matrix elastic constants. With one exception, all the measurements agree with theory within 0.7%. The results confirm the model, show that particle size fails to affect E, and demonstrate a 17% negative departure (at c=0.30) from a linear rule-of-mixture