The tensile behaviour of composites produced by infiltrating ceramic particle beds with high purity (99.99%) Al is studied as a function of reinforcement size and chemistry (Al 2 O 3 and B 4 C). The yield stress is higher in composites containing B 4 C particles, increasing with decreasing interparticle distance in both composite systems. The flow stress of the composites, when corrected for damage, displays the same dependence on interparticle distance as the yield stress. The overall strain hardening exponent, however, is independent of the microstructural scale. These observations are rationalized based on the theory of geometrically necessary dislocations.
Abstract-Particle reinforced composites are produced by infiltrating Al 2 O 3 particle beds with high purity Al (99.99%). These materials feature 40-60 vol. pct reinforcement homogeneously distributed in a pore-free matrix. Their tensile behaviour is studied as a function of reinforcement size and shape. Internal damage, in the form of particle fracture and matrix voiding, occurs from the onset of plastic straining. Its evolution with strain is monitored through changes in (i) stiffness and (ii) peak stress after incremental plastic straining and annealing. The influence of damage on the flow curves of the composites can be accounted for using basic postulates of continuum damage mechanics. Failure strains vary between 2 and 4%, and are a function of the rate of damage accumulation. An expression is derived to predict elongation to failure of damaging materials that fail by tensile instability, which gives good agreement with the experimental observations.
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