Determination of a homogeneity factor for composite materials by a microstructural image analysis method.

The physical properties of particle-reinforced composite materials are highly affected by the distribution of particles within a matrix material. In this study, a microstructural image analysis method with a new distribution index for quantifying the degree of distribution in composite materials was developed. The free-path spacing between particles was measured to calculate the distribution (D) index based on the coefficient of variation. The proposed method was applied to six digitally created reference patterns as representative binary composite microstructures and three actual ceramic-matrix composites, respectively. It is found that the D index increased from 0.00 to 0.67 depending on the degree of distribution or homogeneity level based on the reference patterns. The homogeneity levels for the binary composites are then classified from a perfect (maximum) to very low level (minimum) based on increasing D index values, where a high D index presents a poorer distribution. The results obtained for reference patterns and metal silicide-refractory oxide composite microstructures indicate that the proposed method is a useful tool to quantify the degree of distribution with high accuracy, and can be efficiently used for different types of composite microstructures.