Techniques for the quantification of composite mesostructure

Fiber-reinforced composite materials contain a variety of reinforcement and flaw geometries on a scale ranging from meso to micro which are pertinent to their properties. This paper gives an overview of several techniques that have been developed for quantification of four of these morphologies: fiber spatial distribution, small-angle fiber misalignment, yarn shape and nesting, and microcrack structure. Quantification requires two basic steps: (i) invention of an appropriate metric for the structure of interest; and (ii) development of accurate and efficient measurement procedures. The present work identifies twelve metrics. Specialized computer-aided image analysis techniques are described which make measurements possible with reasonable effort. Example data from several materials are given.