Measurement of fiber density by helium pycnometry

Fiber and void volume fractions of polymeric composite materials are often measured as indicators of part quality. However, accurate fiber and void volume fraction measurements require that the fiber density be known to a high degree of accuracy. Helium pycnometry offers the potential for accurate fiber density measurements. In this study, helium pycnometry was used to measure the density of E-glass, S2-glass, and carbon fibers. Results were compared with those of other fiber density measurement techniques. The density of E-glass was determined to be 2.6173 g/cc. S2-glass was found to have a density of 2.4858 g/cc. Measured carbon fiber densities were 1.7635 g/cc for Toray T300, and 1.7758 g/cc for Hercules IM7.