Quantitative Optical Microscopy Fiber Volume Methods for Composites

Abstract

Quantitative optical microscopy procedures have been developed to determine fiber, resin and void contents in graphite, aramid, and fiberglass composites. These quantitative optical procedures are based on the quantitative measurement of light from a series of micro areas of the composite using either transmitted or reflected light. For aramid and fiberglass composites transmitted light techniques are used, and for graphite composites reflected light techniques are used. The techniques require analytical curves for each com posite sample due to fiber type diffierences and variations in the polish. Analytical curves for the types of composites reported here were found to be linear when light intensity, I, is plotted against the number of fibers, N. The fiber volume is determined from the average intensity recorded from a fixed microscope field on a series of micro sections. The fiber volume results by quantitative optical microscopy agree to within ±2% with the results obtained from calculation and acid digestion methods.