Can flax replace E-glass in structural composites? A small wind turbine blade case study

In directly addressing the question, 'can flax replace E-glass as a reinforcement for structural composites?', this manuscript adopts a novel comparative case study approach to investigate the manufacture and mechanical testing of full-scale 3.5-m composite rotor blades (suitable for 11 kW turbines) built from flax/polyester and E-glass/polyester. The resin transfer moulded flax blade is 10% lighter (fibre mass saving of 45%) than the identical construction E-glass blade. Static flap-bending tests, conducted in accordance to certification standards, confirm that like the E-glass blade, the flax blade satisfies the structural integrity requirements under 'normal operation' and 'worst case' loading. It is consequently claimed that flax is a potential structural replacement to E-glass for similar composite small wind turbine blade applications. The failure root bending moment and corresponding tip displacement of the flax blade are 11.6 kN m and 2300 mm, respectively. The blades exhibit distinctly different load deflection curves and failure modes. The mean flexural rigidity of the flax and E-glass blades are estimated to be 24.6 kN m(2) and 43.4 kN m(2), respectively. It is interesting to find that although flax fibres and their composites are generally recognized for their stiffness, a flax blade cannot compete against an E-glass blade in terms of stiffness. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.