Estimation of three-dimensional connectivity of internal defects in coatings using fractal analysis

The connectivity of a porous medium is an important topological characteris tic, which indicates the extent to which internal defects (e,g,, porosity o r micro/macrocracking) are connected, Up to now, connectivity has been stud ied by various stereological procedures based on the "net volume tangent co unts" proposed by DeHoff and performed on pairs of consecutive sections of an interconnected structure. However, the drawbacks of these procedures are their use of invasive techniques and manual counting. Connectivity is here studied with fractal geometry instead of conventional Euclidean geometry, The porosity network of a thermal spray sample may be f ractal, and so can be at least partly characterized by fractal dimension. M odifications in connectivity could be reflected in changes in the fractal d imension. if changes in the connectivity, as characterized by changes in fr actal dimension, can be adequately demonstrated by the computerized analysi s of confocal scanning laser microscope (CSLM) images, then the technique m ay provide a useful, noninvasive way of improving the characterization of t hermal spray coatings. The study also seeks to show how connectivity differences affect the mechan ical properties of the coating and whether fractal analysis is able to dete ct these changes in mechanical properties.