Finite element-based size optimization of composite fuselage frames for aerospace structures

Abstract This research focuses on the size optimization of fuselage frame structures for Medium Altitude Long Endurance Unmanned Aerial Vehicle (MALE UAV), constructed from carbon fiber composites, to reduce mass while maintaining structural integrity. The optimization process utilizes finite element method (FEM) simulations and targets thickness and ply orientation angle variables. Constraints such as failure indices based on the Tsai-Hill criterion, displacement limits, and symmetry composite design requirements are strictly adhered to. The optimization process often results in the elimination of unnecessary layers, particularly middle laminates like layer 5, and adjusts fiber orientations, typically favoring 90° for outer layers and 0° or ±45° for middle layers, to improve stress distribution and load management. FEM simulations comparing the initial and final frame designs show mass reductions ranging from 10 to 11 % in certain frames. However, in some cases, mass remains unchanged, with only fiber orientations being modified to enhance performance. This size optimization not only reduces mass but also ensures that the structural performance meets strength and rigidity requirements under operational loads. The findings contribute to aerospace engineering by offering strategies that balance performance, reliability, and mass efficiency in composite material applications.