MODELING OF NONUNIFORM COMPOSITE MICROSTRUCTURES

The microstructural effects of non-uniform composite microstructures are modeled. Relationships are observed between the degree of non-uniformity and fiber spatial information which may be measured via image analysis or derived from Dirichlet cell tessellations. For artifical patterns containing chain-like clustering which simulate composite microstructures: (a) the nearest-neighbor distances of random and clustered patterns are smaller than those normally estimated by square or hexagonal arrays, (b) increased clustering may be associated with increased mean cell volume fraction, cell volume fraction distribution standard deviation, number of cell sides, distribution standard deviation, nearest-neighbor distance distribution skewness, and decreased nearest-neighbor distances and (c) accounting for non-uniform fiber diameters is generally unnecessary, except possibly at low fiber volume fraction or with patterns exhibiting a high degree of chaining. For Nicalon SiC/zirconia titanate composite samples with microstructures which exhibit clustering, the maximum value of skewness, determined from sub-regions of the sample, correlates with the flexure strength of that sample.