Test methodTowards the development of laser shock test for mechanical characterisation of fibre/matrix interface in eco-composites

This paper deals with the possibility of using the laser shock test for studying the adhesion between fibre and matrix in composite materials. Single hemp yarn in epoxy matrices - a fully synthetic one, Epolam 2020, and a partially bio-based one, Greenpoxy 56 - specimens have been tested. The water sorption effect on interfacial adhesion quality has been studied. Two different types of damage induced by laser shock have been observed: resin cracks appear only for high laser intensity levels, and specific cone-shaped interfacial damage appears for lower intensity values. The reproducibility of the threshold value evaluation has been demonstrated for the two resins. A numerical simulation by finite elements has also been performed to enhance the understanding of laser shock wave propagation in such samples. These preliminary results demonstrate the ability of the laser shock test to study and quantify the mechanical quality of yarn/matrix interface, which is needed to help design of such composites.