This master’s thesis was written at the Chair of Vehicle Systems Engineering, Lightweight Construction Technology Division, in cooperation with the Fraunhofer Institute for Chemical Technology (ICT) and the Akademische Fliegergruppe (Aka-Flieg) Karlsruhe. Aka-Flieg has been working on a flying wing glider, the AK-X, since 2011. This aircraft is a new and modern model without a direct prototype version. The winglets of the aircraft have to be designed in such a way that the structure of the winglets has maximum strength and stiffness with minimum use of material, which is a common problem in lightweight construction. In this work, the development of a winglet of the AK-X flying wing project is carried out under a stiffness, strength, space and weight boundary condition. The aim is to develop the structure, dimensions and configuration of this winglet. First, various concepts for the development of these winglets are considered. By means of different dimensioning, boundary conditions and occurring problems, decisions are made as to which of these concepts can best be realized.In addition, the bolts for the connection between the wing and winglet are dimensioned and a concept for locking this connection is considered. A structural model is then constructed and simulated for strength using the finite element method (FEM). An FEM model is built and validated for correctness. The results are used to define the concepts, the manufacturing process and the layer structure (called the lay-up plan) of the various fiber composite layers in order to solve the problem. These winglets are manufactured using the lay-up plan and the manufacturing process.

Akaflieg Karlsruhe develops the man-carrying flying wing glider AK-X. The completely new design also requires a new fuselage development. This paper deals with the structural design of this fuselage. In terms of ergonomics, strength, crash safety and manufacturability, it should correspond to the state of the art of modern glider fuselages. These requirements are compiled and explained in detail. Computer-aided methods are used to fulfill them without extensive prototype and model construction. The design is implemented using computer-aided design (CAD) and the finite element method (FEM) is used in the form of topology optimization, laminate optimization, stability analysis and strength calculation. In addition, supporting analytical calculations are carried out using a computer algebra system (CAS). The result of this work is a structural design in fiber composite construction for the fuselage that meets the various requirements and whose strength has been verified for the German Federal Aviation Authority (LBA) in accordance with the JAR-22 construction regulation.

The primary wing structure of the AK-X flying wing glider requires a material with both high strength and rigidity. The AK-X is the current prototype of the Akademische Fliegergruppe am Karlsruher Institut für Technologie. Carbon fiber-reinforced plastics with HT carbon fibers are usually used in the primary wing structure of gliders. These fibers have too low a modulus of elasticity to be used in the AK-X. For this reason, a carbon reinforcement fiber with a high modulus of elasticity and meeting the strength boundary condition is sought for the wing primary structure. The aim of the work is to determine the material properties of various carbon fiber reinforced plastics (CFRP) in tests and to find a carbon fiber that meets the requirements of the AK-X. The tests were carried out with an HT fiber, an IM fiber, two UM fibers made of PAN and a UHM fiber made of pitch in order to have the widest possible range of fiber stiffness and fiber strength available for selection. To determine the material characteristics, quasi-static tests were carried out with CFRP samples under compressive and tensile load. The data obtained was evaluated and the tensile strength, compressive strength and modulus of elasticity for CFRP with five reinforcing fibers were determined. The influence of temperature on the material was determined in tests at 54°C. The tests were carried out with two different fiber volume contents in order to determine the influence of the fiber volume content. The carbon fibers with a higher modulus of elasticity have a lower strength, so it must be weighed up which loss of strength can be accepted in favor of an increase in stiffness. The compressive strength of the samples was lower than the tensile strength, as CFRP fails under compressive load due to micro-buckling. The moduli of elasticity were also lower under compressive loading. As the wing primary structure is equally loaded in tension and compression, the compressive properties were the limiting variables. The fiber was therefore selected based on the compressive properties. Based on these findings from the material testing, a fiber was found that is suitable for the wing primary structure of the AK-X. The UMS40 fiber from Toho Tenax proved to be a good compromise between stiffness and strength. This fiber did not fully meet the requirements, so that a structural modification of the wing primary structure was necessary.

This thesis develops a method for linking a Failure Mode and Effect Analysis (FMEA) with system modeling in SysML. The two methods are intended to complement each other and reduce duplication of work steps. Elements and diagrams created in the system modeling are used to facilitate and structure the creation of an FMEA. The modeling of user-oriented use cases provides a new structure that is used to create an FMEA. The characterization of a system via usage statistics and load spectra enables an evaluation of usage phases, use cases and actions. This evaluation allows a more targeted analysis and prioritization of errors. The information obtained from these two methods is then used to derive design requirements. This is done using the example of the flight control of the AK-X flying wing glider of the Akademische Fliegergruppe am Karlsruher Institut für Technologie e.V..

An evaluation of the flutter stability is to be carried out for the AK-X flying wing glider, which is being constructed by the Akademische Fliegergruppe Karlsruhe. In flying wing configurations with highly stretched wing geometry, the motion-induced unsteady air forces can cause an aeroelastic coupling between the flight-mechanical rigid body angle of attack oscillation and the elastic basic bending oscillation of the wing, which tends to lead to fanned oscillations. In order to avoid such unconventional designs, the structure of the aerofoil should not be designed according to strength aspects but according to stiffness requirements.
In the run-up to this work, an airworthy test model was produced on a scale of 1:2 in carbon fiber composite construction. The structural mode shapes were determined experimentally in the static vibration test and the flutter stability was calculated. In addition, a finite element model of this test model is available, which was adapted to the measured natural modes of vibration.
Based on this finite element modeling, the flutter stability of the AK-X flying wing glider is to be investigated and improved.