A new procedure for the analysis of fibre breakage after processing of fibre-reinforced thermoplastics

During the processing of fibre-reinforced thermoplastics, such as in extrusion and injection moulding, fibre breakage takes place and the average fibre length is reduced. This reduction in length might result in a loss of reinforcement efficiency because the mechanical properties of the composite strongly depend on residual fibre length. For this reason an accurate measure of the fibre length obtained at different process conditions is necessary to relate it with the process parameters. The most used method for determining a fibre length distribution is performed measuring the fibre length by image analysis from micrographs. In the case of thermoplastics reinforced with long fibres, the inability to measure the longer fibres may lead to an underestimation of the average fibre length and thus the correlation between the process parameters and the fibre damage is impaired. In this paper a new procedure is proposed, based on template matching and image mosaic, allowing the measure of fibres of any size. Furthermore this technique allows a researcher to consider all the fibre contained within the specimen. The results obtained with this new procedure is a more accurate estimation of the average fibre length and its distribution even with fibres longer than the available sizes of the micrographs.