Characterization of mode I interlaminar properties of novel composites for tidal turbine blades

Tidal turbine blades are exposed to very high loads and are shorter than wind turbine blades requiring thicker composite sections making manufacturing a slow
process. However, powder epoxy, which has a low viscosity and a low exothermic reaction, is suitable for rapid out-of-autoclave manufacturing of large composite structures such as turbine blades. In this paper, we describe a process that has been developed to manufacture powder epoxy based carbon and glass fibre reinforced plastic (CFRP and GFRP respectively) laminates. Through thickness measurements, resin burn-off and microscope observations, the process was shown to be reliable and to produce consistent parts. The in-plane mechanical properties were measured through tensile testing and low scatter was observed in the GFRP coupons as compared to the CFRP coupons. Difficulties experienced in maintaining uniform alignment of the carbon fibre bundles explains the higher scatter obtained on the longitudinal tensile strength. The mode I interlaminar fracture toughness was obtained for the CFRP samples with a GIC of 1.92 kJ/m^2. It was found to be substantially higher than values reported in literature for carbon/epoxy prepreg systems, making it suitable for use in areas of a tidal turbine blades exposed to high stresses such as near ply drops where the risk of delamination is enhanced.