Analysis of metrological issues for improving quality and reliability in the automated inspection of composite materials

An optical method based on a vision system is presented in this paper, to evaluate the surface void fraction of fibre composite pieces, obtained by a tow filament winding process. Surface void fraction strongly influences the capability of the products to satisfy in service requirements, including reliability. The metrological performances of the method are experimentally evaluated with reference to different influence parameters, like configuration and positioning of the optical system, setting parameters of the image processing software, lighting conditions. The method appears adequate not only for the product quality assessment, but also for the purpose of the process optimization, since it allows to highlight specific distributions of the defect on the surface of the piece, due to characteristics of the process, like mechanical control of winding and vibrations.