Determination of Fiber Volume Fractions by Optical Numeric Volume Fraction Analysis

A method for determining the fiber volume fraction in continuous fiber composites by automatically counting the fiber ends per unit area in digitized microscope images of representative cross sections has been developed. Since fiber counts are digital variables, the accuracy of the method is essentially independent of small variations in microscope focus and specimen surface preparation. In addition to producing averaged data, the method enables the construction of volume fraction variation profiles ranging from the finest possible scales up to full size components. Results are in agreement with values obtained by acid digestion tests.