Non-dried flax fibre reinforced thermoplastic composites in wet environments

Abstract

The long-term performance of natural fibre reinforced thermoplastic (NFRP) composites is critical for developing more sustainable structures. The defects developed in NFRP due to fibre swelling and shrinkage in wet service conditions constitute a significant issue. Here, a method for restricting the in-service swelling and shrinkage of NFRP is proposed. The NFRP composites were processed with swollen fibres stored in moist conditions before thermoplastic resin infusion. The swelling of water-saturated NFRP was decreased up to 56% by non-dry fibres. The similar in-plane shear strength and transverse tensile strength of NFRP composites processed with oven-dried and preconditioned fibres (at 50% RH) showed the in-situ polymerisation of poly (methyl-methacrylate) (PMMA) to be insensitive to moisture. Processing composites with preconditioned fibres (at 90% RH) decreased the water immersion ageing sensitivity for in-plane shear properties of NFRP from 30% to nearly zero.