![Metal-composite hybrid structures made by resin transfer moulding: insert (left) and shaft connection element (right) [73].](https://www.researchgate.net/profile/Daniel-Tuerk/publication/320908025/figure/fig11/AS:614350385602572@1523483954427/Metal-composite-hybrid-structures-made-by-resin-transfer-moulding-insert-left-and_Q320.jpg)
![Load introduction elements made with SLM [76].](https://www.researchgate.net/profile/Daniel-Tuerk/publication/320908025/figure/fig12/AS:614350385598474@1523483954455/Load-introduction-elements-made-with-SLM-76_Q320.jpg)
![Overview of different application methods for local load introduction elements [67, 68].](https://www.researchgate.net/profile/Daniel-Tuerk/publication/320908025/figure/fig10/AS:614350385586180@1523483954407/Overview-of-different-application-methods-for-local-load-introduction-elements-67-68_Q320.jpg)
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Exploration and validation of integrated lightweight structures with additive manufacturing and fiber-reinforced polymers
Abstract and Figures
This thesis presents and explores a set of novel approaches for the development of hybrid, integrated, lightweight, structures by combining additive manufacturing (AM) with fiber-reinforced polymers (FRP) in layup processes.
The presented methods combine the strengths of both technologies: While AM takes a forming, structural and functional role, FRPs primarily contribute with their outstanding mechanical properties at low weight to the performance of the structure. From these characteristics three major design concepts are derived, including AM tooling for composite fabrication, AM structural sandwich cores with additional functionalities and AM load introduction elements.
The understanding of materials and manufacturing approaches is a precondition for the embodiment of the design concepts. Therefore, various manufacturing routes are investigated including AM technologies such as fused deposition modeling, binder jetting and selective laser sintering. The thermo-mechanical stability of polymeric AM parts is crucial for autoclave curing of hybrid high-performance structures. To successfully design complex AM elements for the curing process of FRP, the thermo-mechanical creep properties of polymeric AM materials are characterized in three-point bending creep and tensile tests. Alternative concepts include sand and salt structures to produce sacrificial tooling.
The embodiment of the three design concepts comprises two directions: designing for the performance of the part during service operation and designing to support the manufacturing of the structure. In this thesis both directions are addressed:
Design for Performance: The specific mechanical performance of AM-CFRP structures is assessed in comparison to state-of-the Art structures by comparing the weight, the first failure load, the breaking load and the bending stiffness. Hat-stiffeners with structural cores made by AM were over-laminated with CFRP prepregs, cured in an autoclave and tested in three-point bending. AM core designs include honeycombs, trusses oriented along principal stresses, hollow structures filled with salt and a machined PMI foam core with a local load introduction element made by AM. AM-CFRP hat-stiffeners exhibit an increase in the specific fracture load ranging from 54% to 107% compared to the reference. Weights vary from an increase by up to 55% to a reduction of 5%, and the specific bending stiffness is increased by up to 41%. Results thereby confirm the mechanical competitiveness of AM-CFRP structures.
Design for Processing: Additive manufacturing can support the production of composite parts along the process chain ranging from tooling, layup, handling, curing and post-processing. Four major design principles are presented and classified into integrated positioning and fixation elements, layup and handling aids, structural curing aids and post processing aids. Case studies show that the consideration of the processing during the design phase can reduce the deformation of the part during curing, the number of parts and the number of work steps and even eliminate drilling operations for the post-processing of inserts.
The AM-CFRP approach is validated by incorporating the material data, the design principles and concepts into three components on system level. First, a novel aircraft instrument panel consisting of a multi-functional sandwich core shows that AM-CFRP can reduce the structural weight by 40%, the part count by 50% and the assembly steps by 50%. The second case study validates the mechanical performance of the AM-CFRP approach on component level by assessing the ultimate and the fatigue strength of a novel AM-CFRP prosthetic knee. The third case study consists of a robot leg structure and yields in weight reductions by 54% compared to state-of-the art references.
The combination of AM with CFRP thus is a suitable approach for the manufacturing of individualized, lightweight, and geometrically-complex structures with integrated functionalities for low-volume applications, e.g. in the field of aerospace, flying vehicles, robotics and biomedical structures.
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... Digital processes for repair through additive manufacturing. The image is modified from(Türk, 2017). ...
The large volume of in-and out-flow of raw materials to construction projects has a huge potential to be optimised for resource efficiency and waste reduction. With the recent awareness of the importance of the circular economy, construction actors are aligning their practices to be more circular and sustainable. The concept of material banks is born out of this awareness in order to document the lifecycle information of materials and facilitate re-using them. The introduction of new cycles before individual materials reach their final lifecycle stages results in reduced negative environmental impacts. This paper presents a workflow by positioning different digital technologies to automate the procedures for reuse assessment: from the deconstructed building to M/C bank to new construction projects. This automation supports a practical material and component reuse, while it provides the necessary infrastructure to digitise and digitalise the post-deconstruction materials to be visualised, selected and used by future designers in Building Information Modelling (BIM)-based design and management environments. To this aim, the coupling of BIM, reality capturing technologies, additive manufacturing techniques, IoT and RFID sensors is also anticipated.
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Carbon fiber reinforced plastic application, as a substitute for more traditionally applied materials like steel and aluminum, allows for combining lower mass with higher stiffness, and thus an increase in performance of highly-dynamic multiaxial testing machines. A novel through-the-thickness insert was developed to allow load transfer in stiffness-driven CFRP sandwich structures. The insert consists of two parts, is machined with an economical turning process, and features a fine thread which allows it to be accurately tuned, compensating for any potential CFRP sandwich thickness variations. The insert's external surfaces can be milled, meeting the tolerances needed for mating with other components.
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More and more companies manufacture reinforced composite products. To meet the market need, researchers and industries are developing manufacturing methods without a reference that thoroughly covers the manufacturing guidelines. Composites Manufacturing: Materials, Product, and Process Engineering fills this void. The author presents a fundamental classification of processes, helping you understand where a process fits within the overall scheme and which process is best suited for a particular component. You will understand: Types of raw materials available for the fabrication of composite products Methods of selecting right material for an application Six important phases of a product development process Design for manufacturing (DFM) approach for integrating benefits and capabilities of the manufacturing process into design of the product so that the best product can be produced in a shortest possible time and with limited resources Detailed description of composites manufacturing processes with some case studies on actual part making such as boat hulls, bathtubs, fishing rods and more Process models and process selection criteria Design and manufacturing guidelines for making cost-competitive composite products Procedures for writing manufacturing instructions and bill of materials Joining and machining techniques for composite materials Cost-estimating techniques and methods of comparing technologies/manufacturing processes based on cost Recycling approach to deal with post-market composite products To stay ahead in this quickly changing field, you need information you can trust. You need Composites Manufacturing: Materials, Product, and Process Engineering.
Das Buch führt gründlich und umfassend in das Gebiet des Konstruierens mit Faserverbundwerkstoffen ein. Er behandelt die Werkstoffkunde, die Elastostatik und die Festigkeitslehre dieser Werkstoffklasse ebenso wie Entwurfsmethoden und Verbindungstechniken. Im Vordergrund stehen die mechanisch-mathematischen Verfahren zur Dimensionierung und Gestaltung hoch belastbarer Laminate. Die Herleitung grundlegender Zusammenhänge sowie eine Vielzahl detaillierter Abbildungen unterstützen die praktische Anwendbarkeit.
Die zweite Auflage wurde um Regeln zur leichtbaugerechten Gestaltung von Faserverbundstrukturen ergänzt. Ein neues Kapitel zeigt besondere konstruktive Möglichkeiten auf, die sich nur mit Faser-Kunststoff-Verbunden realisieren lassen.
Das Buch ist geschrieben für Ingenieure aus den Bereichen Luft- und Raumfahrttechnik, Automobilbau und Kunststofftechnik, ebenso für Studierende an Universitäten und Fachhochschulen, die sich mit dem konstruktiven Leichtbau beschäftigen.
We combine 3D printing technique, numerical analysis, and experiments to design a new class of sandwich composites that exhibit various bending behaviors. These programmed sandwich structures contain 3D printed core materials with truss, conventional honeycomb, and re-entrant honeycomb topologies. Three-point bending tests are performed to investigate the bending behavior of these sandwich composites with two types of carbon fiber reinforced polymer face sheets. Under bending deformation, sandwich composites with truss core materials provide highest flexural stiffness and strength that are desirable in structural components. The sandwich composites with re-entrant honeycomb core exhibit a sequential snap-through instability which significantly enhances the energy absorption abilities. Our experimental and numerical results indicate that architected core structures can be utilized to tailor the bending properties as well as failure mechanisms. These findings offer new insights into the study of nonlinear mechanical response of sandwich structures, which can benefit a wide range of industries and applications.
The influence of voids in the initiation and propagation of static flexural and flexural fatigue failures of unidirectional carbon fibre composite was investigated. Vacuum pressure in the vacuum bag oven cure process was varied to produce void levels in the range 0.5–6%. The voids were characterised using image analysis and used to explain the static flexural strengths and flexural fatigue results. It was observed that mean void content and aspect ratios were less effective in explaining the mechanical property results than void size distributions. A strong correlation between large voids (area > 0.03 mm2) and a detrimental effect on the mechanical properties was found. This was attributed to the effect of these voids on the crack propagation in the resin rich inter-ply regions.