<p>One of the primary challenges in wind turbine blade optimization research is creating a model that is representative of current state-of-the-art blade structures. This task is complex and time-consuming, given the multiple disciplines involved in blade design and the large-scale of such blades, which now exceed 100&#xa0;meters in length. Moreover, the procedures used to establish the models are typically not scientific, implying a significant risk associated with blade research, as substantial resources spent on developing models are wasted if the actual research ideas are ineffective in practice. To reduce the risk and accelerate research efforts in the scientific community, this work introduces an open-source large offshore wind turbine blade model and demonstrates application in structural optimization research. A detailed thickness optimization of the blade’s constituent material layers is performed, with the objective of minimizing cost while accounting for buckling, tip displacement, and static failure constraints, which are many of the key design criteria according to design certification guidelines. A semi-analytical adjoint design sensitivity analysis approach is used to efficiently compute problem sensitivities, allowing inclusion of the constraints for up to twelve extreme load cases each. Application of the presented optimization strategy reduces cost by 17% and mass by 25%, while maintaining all constraints within allowable limits. The change from initial to optimized laminate thickness distribution is shown, and the optimized function response is demonstrated on the blade, showing the material is at its load-carrying limit throughout the entire blade, highlighting the efficiency of the achieved design.</p>