Polarimetric inspection of flax composite material reinforcements

Abstract

From an environmental point of view, bio-based composite material reinforcements made of flax or hemp fibers prove to be attractive alternatives to glass fibers. Since the mechanical properties of the reinforcements depend on the fiber orientation and since flax is reported to be significantly birefringent, we propose to use polarimetric imaging to study flax reinforcement structure. The characterization is made with a commercial camera equipped with an array of linear micropolarizers, therefore the circular polarization is not considered. Stokes imaging under polarized illumination provides interesting results, as well as 3x3 Mueller imaging. We study fabrics made of flax yarns gimped with thin cotton yarns and fabrics made of flax and polypropylene (PP) commingled yarns gimped with PP yarns.