Numerical investigation on the use of wood–plastic composites for the thermoforming of NACA profile for UAVs

Abstract There is a growing interest in unmanned aerial vehicles (UAVs) or drones in the aviation industry, both for military and civil applications. They are deployed for border surveillance, transport of medicines, data collection, and access to places which present a risk to humans to name a few. The materials used so far in the manufacture of UAVs are wood, plastic, aluminum, and carbon fibers. However, the level of performance of wood–plastic composites is expected to allow them to compete with both plastic and wood for the manufacture of UAVs’ small blades. In this regard, a family of biocomposites based on high-density polyethylene reinforced with 0%, 20%, 30%, 40%, and 50% (w/w) sawdust particles were developed and characterized. Their viscoelastic properties were determined by oscillatory shear tests and their viscoelastic behavior characterized by the Lodge integral model. A numerical study, using the nonlinear explicit finite element method, was further carried out to evaluate their suitability for shaping the blades of the drone by the thermoforming process. The forming pressure required by the numerical analysis was derived from the Van der Waals real gas equation of state. The influence of the airflow on the thickness of the thermoformed part, as well as the stress and energy required for the process were analyzed. The results indicate that the constituent equations have a significant impact on the final stress distribution in the thermoformed part; furthermore, the time and energy required for the forming process is related to the degree of reinforcement of the thermoplastic matrix.