Experimental analysis of mechanical characteristics of bio-sourced composites manufactured with Hand lay-up technique

Nowadays, the development of new and better performing materials is becoming essential in certain fields such as aeronautics, the automotive industry but also for medical applications. The use of composite materials is ever growing in these vastly. These combine interesting mechanical and thermal properties with a lower density, making them a good alternative to metals. However, most of the composite materials currently on the market are produced from a petro-sourced matrix and the development of these materials does not fit with the objectives of a more sustainable society. Therefore, new eco-friendly epoxy resins are being developed, as well as natural reinforcing fibres that would reduce the carbon footprint of the final product. The aim of this work was to determine the static mechanical properties of a composite material based on the partially bio-sourced resin InfuGreen 810 reinforced with flax fibres. To do so, several laminates were first manufactured using the hand layup technique and curing cycles previously developed for InfuGreen 810. Different architectures of flax-based fabrics were used to allow a direct comparison between the final materials. In order to quantify the mechanical properties, several quasi-static tests were carried out on samples such as uniaxial tension, compression, three-points bending and in-plane shear. These tests highlighted the bilinear behaviour of flax fibre at the composite scale, but also the impact of the manufacturing process on the material. The results generally show better properties but with lower reliability for the composite based on unidirectional reinforcements compared to bidirectional fabrics. Regarding the InfuGreen 810, a poor adhesion with the reinforcements is highly suspected. Moreover, a first comparative study with carbon-reinforced samples showed that the latter had significantly better mechanical performances than the flax-based composites.