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

An Automated Parametric Surface Patch-Based Construction Method for Smooth Lattice Structures with Irregular Topologies

Additive manufacturing enables the realization of complex component designs that cannot be achieved with conventional processes, such as the integration of cellular structures, such as lattice structures, for weight reduction. To include lattice structures in component designs, an automated algorithm compatible with conventional CAD that is able to handle various lattice topologies as well as variable local shape parameters such as strut radii is required. Smooth node transitions are desired due to their advantages in terms of reduced stress concentrations and improved fatigue performance. The surface patch-based algorithm developed in this work is able to solidify given lattice frames to smooth lattice structures without manual construction steps. The algorithm requires only a few seconds of sketching time for each node and favours parallelisation. Automated special-case workarounds as well as fallback mechanisms are considered for non-standard inputs. The algorithm is demonstrated on irregular lattice topologies and applied for the construction of a lattice infill of an aircraft component that was additively manufactured

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

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

Design Concepts and Performance Characterization of Heat Pipe Wick Structures by LPBF Additive Manufacturing

Additive manufacturing offers a wide range of possibilities for the design and optimization of lightweight and application-tailored structures. The great design freedom of the Laser Powder Bed Fusion (LPBF) manufacturing process enables new design and production concepts for heat pipes and their internal wick structures, using various metallic materials. This allows an increase in heat pipe performance and a direct integration into complex load-bearing structures. An important influencing factor on the heat pipe performance is the internal wick structures. The complex and filigree geometry of such structures is challenging in regards to providing high manufacturing quality at a small scale and varying orientations during the printing process. In this work, new wick concepts have been developed, where the design was either determined by the geometrical parameters, the process parameters, or their combination. The wick samples were additively manufactured with LPBF technology using the lightweight aluminum alloy Scalmalloy®. The influence of the process parameters, geometrical design, and printing direction was investigated by optical microscopy, and the characteristic wick performance parameters were determined by porosimetry and rate-of-rise measurements. They showed promising results for various novel wick concepts and indicated that additive manufacturing could be a powerful manufacturing method to further increase the performance and flexibility of heat pipes

A Series of Workshops and presentations provided by the Fraunhofer Additive Manufacturing Alliance: Presentation held at Additive Manufacturing for Aerospace & Space, 21st - 22nd February 2018, München

Facilitated by the Fraunhofer Alliance for Additive Manufacturing, which is the largest consortium for applied research in the field of Additive Manufacturing in Europe – the workshop provides the opportunity to learn about the newest research in this field and the possible implementation of state of the art processes for your products. An overview will be given on how to design complex products for AM with a focus on metals and polymers and with respect to different applications related to Aerospace and Space. It will be discussed how AM can be integrated in the product development with other manufacturing technologies. A significant factor for the quality of AM products is the processing and quality of the raw material, which is metal or polymer powder for most AM processes. You will learn about influencing factors for powder quality and the implementation of an efficient powder process for AM. The information given will enable participants to evaluate potentials for their own AM processes and products and it is hoped to enable them to find approaches for the implementation of new or enhanced methods, tools and processes for their companies and organizations. What you will learn:• Overview of research state in design methods for AM and how to design complex geometries(e.g. bionic design, lattices) with already available design tools• How to implement design guidelines and additional functionality (e.g. electronics) in AM for metals and polymers in CAE product development and AM processes• Understanding of the importance of powder quality and processing and how to implement an efficient powder process for AM• New potentials in using surface-treated polymers for space applications About the Fraunhofer Additive Manufacturing Alliance:Fraunhofer is Europe’s largest application-oriented research organization. Its research activities are conducted by 69 institutes and research units at locations throughout Germany. The Fraunhofer Gesellschaft employs a staff of 24,500, who work with an annual research budget totaling 2.1 billion euros. Of this sum, 1.9 billion euros is generated through contract research. More than 70 percent of the Fraunhofer-Gesellschaft’s contract research revenue is derived from contracts with industry and from publicly financed research projects. International collaborations with excellent research partners and innovative companies around the world ensure direct access to regions of the greatest importance to present and future scientific progress and economic development. The Fraunhofer Additive Manufacturing Alliance integrates seventeen Fraunhofer institutes across Germany, which depending on their main focus, deal with subjects concerning additive manufacturing and represent the entire process chain. This includes the development, application and implementation of additive production processes as well as associated materials