Determination of the fibre volume content in natural fibre-reinforced composites by ultimate analysis

Natural fibre-reinforced plastics (NFRP) with renewable polymers as matrices are expected to be an increasing market in the future. In this context the quantification of natural fibre volume content in composites is an important parameter for manufacturers to check the laminate quality. This paper reports a new time and cost efficient method for the determination of natural fibre volume content with a good reproducibility. The measurement of the natural fibre volume content is attributed to the quantification of the total carbon content of the composite as sum parameter determined by chemical ultimate analysis never used for fibre-reinforced plastics before. The differentiation of resin matrix and natural fibre is possible by accounting the different carbon fractions of both components. The fibre weight content can be determined from the detected total carbon of the test samples after the measurement of a calibration line from mix standards. Based on the known densities of the natural fibre and of the resin matrix, the fibre weight content is converted into the corresponding volume content. The fibre volume content of porous and also compact composite parts can be calculated by this approach. The fibre volume content can be measured by this method with a standard deviation of ±1%.