06 Fakultät Luft- und Raumfahrttechnik und Geodäsie
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/7
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Item Open Access Rheology, dispersion, and cure kinetics of epoxy filled with amine‐ and non‐functionalized reduced graphene oxide for composite manufacturing(2021) Ackermann, Annika C.; Carosella, Stefan; Rettenmayr, Markus; Fox, Bronwyn L.; Middendorf, PeterThis study evaluates the effect of plasma surface functionalization of reduced graphene oxide particles on the processing characteristics and homogeneity of dispersion of a bisphenol A‐(epichlorhydrin) epoxy matrix and amine‐based hardener with varying weight fractions from 0.00 to 1.50 wt%. It was observed that amine‐functionalized reduced graphene oxide leads to a more drastic viscosity increase of up to 18‐fold of the uncured suspensions and that its presence influences the conversion rates of the curing reaction. Optical microscopy of thin sections and transmission electron microscopy analysis showed that a more homogeneous dispersion of the particles could be achieved especially at higher weight fractions by using an appropriate surface functionalization. This knowledge can be used to define suitable processing conditions for epoxies with amine‐based hardeners depending on the loading and functionalization of graphene‐related particles.Item Open Access Electrical conductivity of monolithic and powdered carbon aerogels and their composites(2024) Kröner, Jessica; Platzer, Dominik; Milow, Barbara; Schwan, MarinaThe electrical conductivity of powdered carbon aerogels is one of the key factors required for electro-chemical applications. This study investigates the correlation between the structural, physical, mechanical and electrical properties of pure and activated carbon aerogels, as well as aerogel-composites. The thermal activation with carbon dioxide led to higher electrical conductivity and a decrease in density and particle size. Furthermore, the influence of applied force, compressibility of aerogels and aerogel composites on electrical conductivity was studied. A number of different carbonaceous powdered additives with various morphologies, from almost spherical to fiber- and flake-like shaped, were investigated. For two composites, theoretical values for conductivity were calculated showing the great contribution of particle shape to the conductivity. The results show that the conductive behavior of composites during compression is based on both the mechanical particle arrangement mechanism and increasing particle contact area.Item Open Access Technology selection for holistic analysis of hybrid-electric commuter aircraft(2022) Zumegen, Clemens; Strathoff, Philipp; Stumpf, Eike; Wensveen, Jasper van; Rischmüller, Carsten; Hornung, Mirko; Geiß, Ingmar; Strohmayer, AndreasElectric powertrains have different characteristics than conventional powertrains with combustion engines and require unconventional aircraft designs to evolve their full potential. Therefore, this paper describes a method to identify potential aircraft designs with electrified powertrains. Promising technology options in the fields of powertrain architecture, aerodynamic interactions, onboard systems and operating strategies were collected by the project partners of the LuFo project GNOSIS. The effect of the technology options on a commuter aircraft was evaluated in terms of global emissions ( CO2), local emissions ( NOXand noise) and operating costs. The evaluation considers an entry into service in 2025 and 2050 and is based on the reference aircraft Beechcraft 1900D. Literature review and simplified calculations enabled the evaluation of the aerodynamic interactions, systems and operating strategies. A preliminary aircraft design tool assessed the different powertrain architectures by introducing the two parameters ’power hybridization’ and ’power split’. Afterwards, compatible technology options were compiled into technology baskets and ranked using the shortest euclidean distance to the ideal solution and the farthest euclidean distance to the worst solution (Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method). An analysis of the CS 23 regulations leads to a high-wing design and excluded the partial turbo-electric powertrain architecture with the gas turbine in the aircraft tail. For 2025, a partial turbo-electric powertrain with two additional electric driven wingtip propellers was selected. A serial hybrid powertrain, which uses a gas turbine or fuel cell in combination with a battery, powers distributed electric propulsors at the wing leading edge in 2050. In both scenarios, the aircraft design includes an electric environmental control system, an electric driven landing gear and electro-hydraulic actuators for the primary flight control and landing gear.Item Open Access EIPPM : the Executable Integrative Product-Production Model(2021) Schopper, Dominik; Kübler, Karl; Rudolph, Stephan; Riedel, OliverIn this paper, a combination of graph-based design and simulation-based engineering (SBE) into a new concept called Executable Integrative Product-Production Model (EIPPM) is elaborated. Today, the first collaborative process in engineering for all mechatronic disciplines is the virtual commissioning phase. The authors see a hitherto untapped potential for the earlier, integrated and iterative use of SBE for the development of production systems (PS). Seamless generation of and exchange between Model-, Software- and Hardware-in-the-Loop simulations is necessary. Feedback from simulation results will go into the design decisions after each iteration. The presented approach combines knowledge of the domain “PSs” together with the knowledge of the corresponding “product” using a so called Graph-based Design Language (GBDL). Its central data model, which represents the entire life cycle of product and PS, results of an automatic translation step in a compiler. Since the execution of the GBDL can be repeated as often as desired with modified boundary conditions (e.g., through feedback), a design of experiment is made possible, whereby unconventional solutions are also considered. The novel concept aims at the following advantages: Consistent linking of all mechatronic disciplines through a data model (graph) from the project start, automatic design cycles exploring multiple variants for optimized product-PS combinations, automatic generation of simulation models starting with the planning phase and feedback from simulation-based optimization back into the data model.Item Open Access Digital function modeling in graph-based design languages(2022) Elwert, Michael; Ramsaier, Manuel; Eisenbart, Boris; Stetter, Ralf; Till, Markus; Rudolph, StephanThe main focus of this paper is the integration of an integrated function modeling (IFM) framework in an engineering framework based on graph-based design languages (GBDLs). Over the last decade, GBDLs have received increasing attention as they offer a promising approach for addressing several important challenges in engineering, such as the frequent and time-consuming transfer of data between different computer aided engineering (CAE) tools. This absorbs significant amounts of manual labor in engineering design projects. GBDLs create digital system models at a meta level, encompassing all relevant information concerning a certain product design and feeding this into the relevant simulation tools needed for evaluating the impact of possible design variations on the performance of the resulting products/parts. It is possible to automate this process using digital compilers. Because of this, it is also possible to realize systematic design variations for a very large number of parameters and topological variants. Therefore, these kinds of graph-based languages are a powerful means for creating a large number of viable design alternatives and for permitting fast evaluation processes against the given specifications. While, thus far, such analyses tend to be based on a more or less fully defined system, this paper proposes an expansion of the applicability of GBDLs into the domain of product functions to cohesively link conceptual with embodiment design stages. This will also help with early systematic, automated generation and the validation of design alternatives through relevant simulation tools during embodiment design. Further, it will permit the automated exploration of function paths and enable extended analysis possibilities, such as the detection of functional bottlenecks, while enhancing the traceability of the design over the development process. For these extended analysis possibilities, a function analysis tool was developed that adopts core ideas of the failure mode and effects analysis (FMEA). In this, the functional distinction between function carriers and function-related processes allows the goal-directed assessment of component reliabilities and the detectability and importance of processes in a technical system. In the paper, the graph-based modeling of functions and the function analysis tools are demonstrated on the example of a multicopter.Item Open Access High-performance properties of an aerospace epoxy resin loaded with carbon nanofibers and glycidyl polyhedral oligomeric silsesquioxane(2022) Guadagno, Liberata; Pantelakis, Spiros; Strohmayer, Andreas; Raimondo, MarialuigiaThis paper proposes a new multifunctional flame retardant carbon nanofiber/glycidyl polyhedral oligomeric silsesquioxane (GPOSS) epoxy formulation specially designed for lightweight composite materials capable of fulfilling the ever-changing demands of the future aerospace industry. The multifunctional resin was designed to satisfy structural and functional requirements. In particular, this paper explores the advantages deriving from the combined use of GPOSS and CNFs (short carbon nanofibers) to obtain multifunctional resins. The multifunctional material was prepared by incorporating in the epoxy matrix heat-treated carbon nanofibers (CNFs) at the percentage of 0.5 wt% and GPOSS compound at 5 wt% in order to increase the mechanical performance, electrical conductivity, thermal stability and flame resistance property of the resulting nanocomposite. Dynamic mechanical analysis (DMA) shows that the values of the Storage Modulus (S.M.) of the resin alone and the resin containing solubilized GPOSS nanocages are almost similar in a wide range of temperatures (from 30 °C to 165 °C). The presence of CNFs, in the percentage of 0.5 wt%, determines an enhancement in the S.M. of 700 MPa from −30 °C to 180 °C with respect to the resin matrix and the resin/GPOSS systems. Hence, a value higher than 2700 MPa is detected from 30 °C to 110 °C. Furthermore, the electrical conductivity of the sample containing both GPOSS and CNFs reaches the value of 1.35 × 10−1 S/m, which is a very satisfying value to contrast the electrical insulating property of the epoxy systems. For the first time, TUNA tests have been performed on the formulation where the advantages of GPOSS and CNFs are combined. TUNA investigation highlights an electrically conductive network well distributed in the sample. The ignition time of the multifunctional nanocomposite is higher than that of the sample containing GPOSS alone of about 35%.Item Open Access In-flight lift and drag estimation of an unmanned propeller-driven aircraft(2021) Bergmann, Dominique Paul; Denzel, Jan; Pfeifle, Ole; Notter, Stefan; Fichter, Walter; Strohmayer, AndreasThe high-power density and good scaling properties of electric motors enable new propulsion arrangements and aircraft configurations. This results in distributed propulsion systems allowing to make use of aerodynamic interaction effects between individual propellers and the wing of the aircraft, improving flight performance and thus reducing in-flight emissions. In order to systematically analyze these effects, an unmanned research platform was designed and built at the University of Stuttgart. As the aircraft is being used as a testbed for various flight performance studies in the field of distributed electric propulsion, a methodology for precise identification of its performance characteristics is required. One of the main challenges is the determination of the total drag of the aircraft to be able to identify an exact drag and lift polar in flight. For this purpose, an on-board measurement system was developed which allows for precise determination of the thrust of the aircraft which equals the total aerodynamic drag in steady, horizontal flight. The system has been tested and validated in flight using the unmanned free-flight test platform. The article provides an overview of the measuring system installed, discusses its functionality and shows results of the flight tests carried out.Item Open Access Response of the International Energy Agency (IEA) Wind 15 MW WindCrete and Activefloat floating wind turbines to wind and second-order waves(2021) Mahfouz, Mohammad Youssef; Molins, Climent; Trubat, Pau; Hernández, Sergio; Vigara, Fernando; Pegalajar-Jurado, Antonio; Bredmose, Henrik; Salari, MohammadItem Open Access Control co-design optimization of floating offshore wind turbines with tuned liquid multi-column dampers(2024) Yu, Wei; Zhou, Sheng Tao; Lemmer, Frank; Cheng, Po WenThe technical progress in the development and industrialization of floating offshore wind turbines (FOWTs) over the past decade has been significant. Yet, the higher levelized cost of energy (LCOE) of FOWTs compared to onshore wind turbines is still limiting the market share. One of the reasons for this is the larger motions and loads caused by the rough environmental excitations. Many prototype projects tend to employ more conservative substructure designs to meet the requirements for motion dynamics and structural safety. Another challenge lies in the multidisciplinary nature of a FOWT system, which consists of several strongly coupled subsystems. If these subsystems cannot work in synergy, the overall system performance may not be optimized. Previous research has shown that a well-designed blade pitch controller is able to reduce the motions and structural loads of FOWTs. Nevertheless, due to the negative aerodynamic damping effect, improvement in the performance by tuning the controller is limited. One of the solutions is adding tuned liquid multi-column dampers (TLMCDs), meaning that there is a structural solution to mitigate this limiting factor for the controller performance. It has been found that the additional damping, provided by TLMCDs, is able to improve the platform pitch stability, which allows a larger blade pitch controller bandwidth and thus a better dynamic response. However, if a TLMCD is not designed with the whole FOWT system dynamics taken into account, it may even deteriorate the overall performance. Essentially, an integrated optimization of these subsystems is needed. For this paper, we develop a control co-design optimization framework for FOWTs installed with TLMCDs. Using the multi-objective optimizer non-dominated sorting genetic algorithm II (NSGA-II), the objective is to optimize the platform, the blade pitch controller, and the TLMCD simultaneously. Five free variables characterizing these subsystems are selected, and the objective function includes the FOWT's volume of displaced water (displacement) and several motion and load indicators. Instead of searching for a unique optimal design, an optimal Pareto surface of the defined objectives is determined. It has been found that the optimization is able to improve the dynamic performance of the FOWT, which is quantified by motions and loads, when the displacement remains similar. On the other hand, if motions and loads are constant, the displacement of the FOWT can be reduced, which is an important indication of lower manufacturing, transportation, and installation costs. In conclusion, this work demonstrates the potential of advanced technologies such as TLMCDs to advance FOWTs for commercial competitiveness.Item Open Access Quantification of amplitude modulation of wind turbine emissions from acoustic and ground motion recordings(2023) Blumendeller, Esther; Gaßner, Laura; Müller, Florian J. Y.; Pohl, Johannes; Hübner, Gundula; Ritter, Joachim; Cheng, Po Wen