Mechanical behavior of residually stressed composites with ductile and brittle constituents

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Abstract
The mechanical behavior of particulate reinforced composites is studied when residual stresses are present. Brittle matrix composites (BMCs) with ductile inclusions are compared with metal matrix composites (MMCs) with elastic inclusions. Cell models are used to perform finite-element calculations for different volume fractions of uniformly distributed particles with spherical or cylindrical shape. The stresses of the BMCs are shown to follow a bilinear curve with a localized transition region separating linear parts with similar slopes. BMCs are much stiffer than MMCs and cylindrical-shaped particles lead to a higher composite stiffness than spherical particles. Thus, only in the presence of a high volume fraction of cylindrical particles can residual stresses be easily monitored in the stress-strain curve of BMCs. Additionally, hardening is found to affect BMCs to a much lesser degree than MMCs. The influence of particle shape on initial yield stress is elaborated. It is demonstrated that for metal-ceramic composites the contiguity of the ductile phase is necessary to obtain an elastic-plastic mechanical response in agreement with experiments.