Wind turbine blades and aircrafts have grown in size to improve energy efficiency and reduce cost. The weight of these structures has also increased due to their larger sizes. Reducing the weight of these structures can increase efficiency and lower fuel consumption, and decrease the structural load. Fabricating structures using composite materials is currently the most popular way to reduce weight. Several optimization algorithms are employed to achieve optimal composite structure design. A combination of these composite materials and a well-developed optimization algorithm can be effectively applied to improve the design of these larger composite structures. This study investigated the design of a composite spar and its feasibility by analyzing static conditions under extreme loads. Structural properties and stress analyses were calculated using the VABS program. Pre-processing and post-processing were performed by applying in-house MATLAB-based codes. The maximum stress failure theory was applied to check and confirm the composite laminate failure. A particle swarm optimization algorithm was also applied to analyze the design of the composite spar. The analysis results show that the proposed design method in this study is feasible and applicable to the design of composite spars for wind turbine blades and aircraft wings.