A non-destructive optical experimental method to predict extinction coefficient of glass fibre-reinforced thermoplastic composites

The aim of this paper is to develop a cost-effective, efficient and fast experimental optical method to predict the optical properties (extinction coefficient) of semi-transparent glass-fibre-reinforced polymer composites. The extinction coefficient takes into account the effects due to the absorption and the scattering phenomena in a semi-transparent component during the laser processes, i.e. TTLW (Through-Transmission Laser Welding). A laser as light source and a reflex camera equipped with a macro lens as a measuring device are used in the present method. It is based on the measuring of the transmission of light through different thicknesses of samples. The interaction between the incident laser beam and the semi-transparent composite is examined. The results are presented for the case of a semi-transparent composite reinforced with unidirectional glass fibre. A numerical method, ray tracing, is used to validate the experimental results. The ray tracing method is suitable for characterizing the light-scattering in semi-transparent materials.