Bir jet eğitim uçağı kanadının dayanım ve direngenlik kısıtları altında yapısal eniyilemesi

This thesis presents structural optimization studies for a jet trainer aircraft wing structure. The main purpose is to select the most convenient rib/spar layout for T-38 wing like geometry which consists of metallic and composite components by using a finite element modeling and analysis tool of MSC NASTRAN optimization capabilities. In this study, in order to decrease the number of design variables and as well as to be able to obtain smooth thickness transitions between adjacent zones, design variable linking method is used by applying different shape functions. First of all, after creating the outer geometry in CATIA, the finite element model (FEM) is prepared using MSC PATRAN. Similarly, all design zones where design variables are free to change are designated. To be able to link the thicknesses of the components to each other with regards to their locations on the wing, all coordinates of design zones are transformed to natural coordinate system as their center points are positioned as located between 0 and 1 in span-wise direction and -0.5 and 0.5 in chord-wise direction using scripts coded in Python. Aerodynamic loads are then calculated by using MSC FLDS (FlightLoads) tool and summed in predefined monitor stations to distribute onto the structure using rigid body elements. Obtained shear force and bending moment distributions are also compared with another method called as Schrenk's Approximation. In the optimization studies, thicknesses of the metallic structures and principal composite ply thicknesses are considered as design variables. There are five design constraints which are von Mises stress for the metallic structures, failure index for strength check of composite structures, global buckling, damping and natural frequencies which are used to control the flutter speed. The objective in this research is to obtain a minimum weight in design while providing predefined constraints via investigating various design candidate geometries having different layouts but same outer geometry. Finally, by using the scripts developed within this thesis study, the design variable linking method used according to the locations of the design zones become suitable also for the Nastran Sol 200 users.