Computational Micromechanics for the Optimization of Compression Strength of Unidirectional Carbon Fiber Composites for Use in Wind Turbine Blades

As wind turbine blades grow longer, new design parameters gain additional importance such as blade weight, tip deflection and material cost. These parameters require designers to relook at carbon fiber as a potential design solution. However, the composite materials in wind turbine blades are subjected to significant compressive loading, and the compressive strength of carbon fiber reinforced polymer (CFRP) composites is much lower than its tensile strength. This reduction in compression strength is due to a change in failure mode from that seen in tensile loading. The aim of this study is to investigate three factors that affect the compressive failure response of CFRP composites. These factors include fiber defect severity, volume fraction, and multiaxial loading.Compressive strength was shown to have decaying sensitivity with increasing fiber misalignment. Decreasing the volume fraction not only decreased the compressive strength but also increased the compressive failure strain. In addition, adding in-plane shear loads proved detrimental to the compressive load-carrying capacity of a composite structure. This research showed minimizing fiber misalignment in manufacturing processes is only beneficial for high tolerance processes. Decreasing volume fraction could be beneficial for highly flexible structures. Finally, the results demonstrated the need to minimize multiaxial loading for optimal composite compressive response.