Vertical-axis wind turbines are considered a proper solution for today's energy needs. To make it affordable for domestic usage, this requires a reduction in the turbine cost, blade weight, and an increase in blade life. The challenge in VAWT blade design is fatigue and blade life prediction, besides surviving centrifugal force and repeated load pattern effects. The paper focuses on the blade structure modelling and optimization to assess the design for integrity, fatigue, life, sustainability, and cost. The presented model can examine varied materials, including new biodegradable materials, while reducing computation time and resources. The structure analysis is based on classical lamination theory (CLT) and polynomial failure theory (Tsai-Hill and Tsai-Wu). Fatigue analysis and blade life are based on damage evaluation using Miner’s rule for loading steps, evaluated stresses and strains, and loading cases. The approximation model simplifies the dynamic and fatigue analysis procedures to make the model integrable with the optimization method. The beam element method is used to approximate the fundamental frequencies of blade structure. The genetic algorithm is the optimization method used for single objective function, non-linear constrained, mixed integer problem. Decision variables vary according to the scope of optimization which includes the five main composite structure parameters: lamina thickness, orientation, volume fraction, and material selection for resin and fiber. However, in the case of pre-defined laminae materials, only the thickness, orientation, and selection index are used. The commercial finite element software ANSYS is used to validate results.