The present article gives information on 2 years seawater aging effect on injected flax/PLA biocomposite. Biocomposite suffer from relatively high moisture absorption which is controlled by vegetal fibre. Simple rule of mixture allows for flax fibre the determination of a weight gain at saturation around 12% which is close to already published values. Bundles of fibres and especially middle lamellae influence water uptake. Water alters biocomposites, and flax fibres since their mechanical properties are reduced (Young modulus and tensile strength) with aging. Linear relationship is observed between water uptake and loss of mechanical properties. Load-unload cycles highlight damage occuring earlier as biocomposite undergo aging. These damages can be induced by fibre degradation and washing out of soluble components especially the fibre bundles cement, by debonding of fibre bundles linked to their swelling.

Glass fibre reinforced thermoset composites are widely used in marine applications, even though they raise a number of health and environmental questions (e.g. emission of volatile organic compounds VOC), and offer very few solutions at the end of their life. One alternative is natural fibre reinforced biopolymer composites called biocomposites. Indeed these are subject to increasing attention because of their good mechanical properties and total biodegradability. The aim of this study is to investigate the influence of processing on the properties of biocomposites and then to examine their durability in the marine environment. Unreinforced PLLA (Poly(L-Lactic acid)), and injected and film stacked flax composites with the same PLLA matrix have been studied. All the samples were aged in seawater at different temperatures in order to accelerate hygrothermal aging. The evolution of physico-chemical behaviour has been followed by weight measurements, GPC and tensile testing, completed by SEM analysis of fractured specimens.