Experimental and numerical failure analysis of horizontal axis water turbine carbon fiber-reinforced composite blade

High-performance composites are used in many applications due to their design flexibility, corrosion resistance, high strength-to-weight ratio, and many other excellent mechanical properties. In this study, the location and magnitude of failure initiation in horizontal axis water turbine carbon fiber reinforced polymer (CFRP) blades with different lay-up orientations were investigated. Unidirectional [0°]4 and cross-ply [0°/90°]S layups were selected to study the effect of the buildup direction on the failure of the composite water turbine blades. A finite element analysis (FEA) model was generated to examine the stresses along blade span under both flexural and hydrodynamic loads. Flexural destructive tests were conducted to validate the results obtained from the numerical simulations. In addition, a blade element momentum theory model was created to calculate the hydrodynamic forces acting along the span to determine the maximum loading radial location, which was used for the fixture design and FEA simulation input. Both unidirectional and cross-ply composite blades were tested for failure. There was a general agreement between the experiments and simulations, which validated the results. Moreover, FEA simulations were performed to apply the load to the samples with different pitch angles (-10°, -5°, 0°, 5°, and 10°). Even though the unidirectional CFRP composite blades showed higher strength at 0° pitch angle than the cross-ply blades, the strength of the unidirectional blade dropped significantly when the load was applied with different pitch angles other than 0°, while the strength of the cross-ply blades was less responsive to this pitch angle variation.