Flax fibre reinforcements. Property change kinetics due to biodeterioration in seawater and soil

Eco-design of composite structures is essential today and flax fibres from renewable resources are a promising reinforcement. Their natural biodegradability can be seen as an advantage or a handicap when considering service in severe environments. In this study the changes in mechanical properties are measured during aging in two media which favour the development of micro-organisms and biodegradation: Burial in agricultural soil and immersion at sea in coastal waters. Respirometry tests provide the rate of biodegradation. SEM observations and AFM analyses reveal the damage development both on the surfaces and within the fibres during aging. Tensile tests were performed on fibres and fibre bundles, both are used to reinforce composites, and showed that residual performance was retained up to a critical time: After 140 days in seawater the retention of modulus and strength was 25 % and 12 % of initial values. The paper concludes with a discussion of biocomposite LCA and a comparison with another end-of-life option; incineration.