Optical analysis of composite materials: metrological issues

In this paper, a procedure to improve the winding angle measurement of a filament winded composite component is proposed. The procedure is based on the use of a polarized camera that can acquire information on the direction of the light. This vision system has been proven to be suitable for the analysis of a carbon fibre surface due to the physical property of this material. It reflects light with a polarization angle equal to the orientation of the fibres. A statistical analysis of the angle of linear polarization (AoLP) for each pixel within the examined regions enables the evaluation of the winding angle. For improving this measurement, some geometrical and methodological aspects are examined in detail. A procedure for identifying a region of interest (RoI) in surface acquisition is proposed, and the impact of integrating multiple images of the same area is assessed. The result is a reduction in the variability of the measured distribution of the fiber angles.