Additive Manufactured Structures for the 12U Nanosatellite ERNST

One of the emerging technologies in recent years is additive manufacturing. It promises unprecedented design freedom in both modeling and rapid manufacturing. We are reaping the benefits of additive manufacturing for our 12U nanosatellite ERNST by printing the optical bench that supports the spacecraft payloads. We design the structures by using a finite-element numerical approach for optimizing the topology with respect to 1) available design space, 2) payload interfaces, 3) mechanical launch loads, and 4) thermal loads generated by the cryocooler of the MWIR main payload. We cope with the latter by integrating a pyramidal structured radiator surface in the optical bench as a functional element. Making use of the selective laser melting technique, we manufactured the first version of the optical bench for the engineering model of the ERNST spacecraft from AlSi10Mg alloy. Vibrational testing proved the suitability of our multidisciplinary design approach and the production quality. We are currently implementing the next version of the ERNST optical bench including spacecraft design changes and using Scalmalloy®, a material developed for additive manufacturing that provides high tensile strength and low thermal expansion. This marks a next step on the way to the application of additive manufactured components in space

The macroscopic behavior of pantographic sheets depends mainly on their microstructure: experimental evidence and qualitative analysis of damage in metallic specimens

Recently the exotic properties of pantographic metamaterials have been investigated, and various mathematical models (both discrete and continuous) have been introduced. However, the experimental evidence available up to now concerns only polyamide specimens. In this paper, we use specimens printed using metallic powder. We prove experimentally that the main qualitative and quantitative features of pantographic sheets in planar deformation are independent of the constituting materials, at least when they can be regarded as homogeneous and isotropic at micro-level. Of course, the absolute value of Young’s modulus of constituent material affects the overall reaction force needed to the hard device to impose a given displacement: A first investigation on this effect is also attempted

Developing Tungsten-Filled Metal Matrix Composite Materials Using Laser Powder Bed Fusion

The additive manufacturing technique laser powder bed fusion (L-PBF) opens up potential to process metal matrix composites (MMCs) with new material pairings free from limitations of conventional production techniques. In this work, we present a study on MMC material development using L-PBF. The generated composite material is composed of an X3NiCoMoTi 18-9-5 steel as matrix and spherical tungsten particles as filler material. A Design of Experiment (DoE)-based process parameter adaption leads to an Archimedean density close to the theoretical density in the case of 60 vol% tungsten content. A maximum ultimate tensile strength of 836 MPa is obtained. A failure analysis reveals a stable bonding of the tungsten particles to the steel matrix. This encourages the investigation of further material combinations. An additional heat treatment of the MMC indicates the potential to design specific material properties; it also highlights the complexity of such treatments

Designed Materials by Additive Manufacturing—Impact of Exposure Strategies and Parameters on Material Characteristics of AlSi10Mg Processed by Laser Beam Melting

The Laser Beam Melting (LBM) Additive Manufacturing technology for metal processing is based on the local application of an intense laser beam, causing a characteristic microstructure, which can achieve higher mechanical properties than conventionally manufactured equivalents. The material is created incrementally in sections that are processed with different manufacturing parameters. This paper proposes the creation of Designed Materials by varying the manufacturing parameters and exposure strategy in order to induce a gradient or a local change of properties by designing the microstructure. Such materials could also be created by changing the material topology on a micro-, meso-, or macro-scale, or on multiple scales at once. This enables systematic creation of material types like Functionally Graded Materials (FGMs), Metamaterials, or other Designed Materials, in which characteristics can be varied locally in order to create a customized material. To produce such materials by LBM, it is necessary to gain a detailed understanding about the influence of the manufacturing parameters. Experimental studies have been carried out to investigate the melt pool geometry and microstructure resulting from the exposure parameters. Based on the results, parameter sheets have been derived, which support the process of finding optimized parameter sets for a specific purpose. General methods and their ability to influence the material structure and properties were tested and evaluated. Furthermore, the resulting change of the microstructure was analyzed and a first Graded Material was generated and analyzed to show the potential and possibilities for Designed Materials on multiple scales by Laser Beam Melting

Towards flight qualification of an additively manufactured nanosatellite component: Paper presented at 69th International Astronautical Congress, Bremen, Germany, October 1-5, 2018

Fraunhofer EMI is currently designing a 12U nanosatellite. The mission is called ERNST (Experimental Spacecraft based on Nanosatellite Technology) and its main goal is to evaluate the utility of a nanosatellite mission for scientific and military purposes. As spacecraft developments demand the adaption of different subsystems for every mission, Fraunhofer EMI decided to use Additive Manufacturing (AM) in the construction of secondary satellite structures in order to achieve a highly adjusted structure which serves the exact required purpose of each individual mission. The significant advantage of using AM lies in the design freedom as it has almost no design restrictions as compared to conventional manufacturing methods. Given this, the design freedom can be used to implement a numerical optimization process, using topology optimization algorithms. During the optimization process, material is only placed at necessary areas. A Multidisciplinary Design Optimization for the optical mounting structure (optical bench) of the satellite was established, considering vibrational boundary conditions during the launch period and thermal boundary conditions during the operational phase. This paper presents the latest updates towards flight qualification of the optical bench in terms of design, optimization model and post-process concepts

Micro- and macrostructural investigations of AlSiMg produced by laser beam melting

In Laser Beam Melting (LBM), alloys like AlSi10Mg are locally melted by an intense laser beam. Specifically Designed Materials can be realized by locally varying the exposure parameters and applying diverse exposure strategies. By this approach, different micro- and macrostructures can be obtained that lead to individual mechanical properties within one part. A well-established understanding of the correlation between manufacturing parameters, generated micro- and macrostructure and resulting material properties enables the creation of complex microstructural material compositions meaning specifically Designed Materials. The interdependency of manufacturing parameters on the micro- and macrostructure was studied for different exposure strategies in LBM processing of AlSi10Mg using a 1 kW laser source and building layers of 90 μm. The investigations focus on the analysis of data obtained by imaging techniques like light and scanning electron microscopy. In particular, melt pool boundaries and crystal grains are examined

Nachhaltigkeit der Additiven Fertigung: Vergleichende ökonomische und ökologische Bewertung von additiven und konventionellen Fertigungstechnologien

Additive Fertigungsverfahren (Additive Manufacturing, AM) bieten aufgrund der schichtweisen Generierung von Strukturen eine einzigartige Designfreiheit. Auch die Flexibilität, die Möglichkeit der Funktionsintegration, die Individualisierungsmöglichkeit sowie beschleunigte Innovationszeiten machen die AM zu einer Schlüsseltechnologie der Industrie 4.0. In der vorgestellten Studie geht es um die künftige Anwendung von AM, insbesondere hinsichtlich der Energie- und Ressourceneffizienz sowie der Wirtschaftlichkeit dieser Technologie

Resource analysis model and validation for selective laser melting, constituting the potential of lightweight design for material efficiency

Selective Laser Melting (SLM) offers significant potential for a sustainable way of production. Raw material in form of metallic powder can directly be reused and the selective nature of the process offers new potential for resource economization. We introduce a mathematical model, which allows conclusions about the influence of parameters like part volume (influenced by lightweight design) and exposure parameters onto the resource consumption in an SLM process. For this purpose, time and energy consumption are classified in process shares as a function of volume and process parameters. The introduced approach is validated by experimental methods under the consideration of part volume, exposure parameters and batch size. While the approach shall be independent of the manufactured material, the experiments are executed for the aluminum alloy AlSi10Mg. The measurements quantify the impact of the part volume and process parameters on the resource consumption and provide recommendations for improvements regarding an increased material efficiency. Additionally, the established model can be used to analyze manufacturing costs for single parts or series productions. The results illustrate the importance of lightweight design methods for an efficient and sustainable production by powder bed fusion methods like SLM

The D-MEN sampling device - extracting and collecting asteroid material for sample return: Paper presented at the 68th International Astronautical Congress, IAC 2017, Adelaide, Australia, 25-29 September 2017

We report about the development and the characteristics of a Device for Material Extraction from Near earth objects (D-MEN). The D-MEN sampling device was developed as part of the NEOShield-2 project and is optimized to collect at least 100 grams of asteroid material including up to 4 cm sized particles. The design drivers are a short static landing scenario and the required capability to not only collect loose particles, but also to extract material from solid surfaces having compressive strengths of up to 50 MPa. This performance is achieved by a combination of fluidizing loose regolith material and extracting solid material by pyrotechnically driven bolt actuators. The D-MEN is a highly integrated system including two bolt actuators, two self-closing material compartments and a pressure pipe system. 3D metal printing technologies have been applied to implement the system in a cylindrical volume of 150 mm diameter by 130 mm high. The performance of the system is demonstrated here by comprehensive tests on different target configurations