TRR 277

Integration of Individualized Prefabricated Fibre Reinforcement in Additive Manufacturing with Concrete

19.02.2021
Rothe, Tom; Doctoral researcher, TU Braunschweig, Institute of Mechanics and Adaptronics (IMA)
Hühne, Christian; Project leader, TU Braunschweig, Institute of Mechanics and Adaptronics (IMA)

One of the biggest challenges in 3D printing with cementitious materials is the integration of reinforcement. The project aims to develop textile-based reinforcement strategies for additive manufacturing with concrete and to utilize the advantages of textile reinforcement (e.g. corrosion resistance and material flexibility) for the production of material-efficient, individualized structures. These structures should be produced by a robotic winding process, which provides a high degree of freedom in shaping in combination with a minimal amount of tooling and formwork. To be able to do so, a highly autonomous production process is required. Therefore an in situ fiber preparation is integrated. Within this process, fiber rovings are formed to strands. Furthermore, the fiber preparation includes the resin impregnation and the application of a helix surface structuring by wrapping a secondary yarn around the preformed strands to increase the interlocking between the reinforcement structure and the concrete. 

Besides their structural task, the winded reinforcement meshes serve as a base for additively applied concrete. Different methods for applying the concrete can be used.

First experiments to produce reinforcement structures by the winding of glass fiber strands have successfully been conducted. Fig. 1 shows the used robot while winding fiber strands around pins on a rectangular frame. The preparation of the fibers occurred in situ with an end-effector, which has been developed for this purpose within this project. After the winding, concrete was applied on the winded frame by shotcreting. 

Further investigations on the winding process and the use of different additive manufacturing techniques to apply the concrete are planned for the near future.

Laser Powder-Bed Fusion (PBF-LB/M) of Steel Elements for Construction – Basics of Design and Mechanical Resilience

12.02.2021
Diller, Johannes; Doctoral researcher, TU Munich
Dorina Siebert; Doctoral researcher, TU Munich, Chair of Metal Structures
Wenzler, David; Doctoral researcher, TU Munich
Kolb, Cara; Doctoral researcher, TU Munich, Institute for Machine Tools and Industrial Management

The reproducibility of the mechanical properties of PBF-LB/M parts needs to be increased. This requires a more detailed understanding of the correlation between the process parameters and the mechanical and metallurgical properties of the manufactured parts. In project A06 a first step towards this goal has been taken:

With a thermography camera, the cooling rates during the fabrication of fatigue test specimens were measured. Two process parameter sets with different scanning speed and laser power were used for the manufacturing. Afterwards, strain-controlled fatigue testing was performed to investigate the plastic deformation behaviour resulting from the different processing conditions. The first results show significant correlations between the manufacturing conditions, cooling rates, and mechanical properties.

Currently, the thermography set-up is being optimised by a high-speed camera to increase the spatial and temporal resolution. In the next step, the process parameter space will be extended and comprehensive tensile and fatigue testing will be conducted.

1st aaec network member symposia:

“research insides in Additive Manufacturing Construction”

See the full video recording of the online symposia now for free on TRR277s YouTube Chanel (https://youtu.be/EHaXGHG8e_4)

The CRC/Transregio TRR 277 - Additive Manufacturing in Construction based in Braunschweig and München has organised the 1st research insides on 1st of february 2021 within the Research Network for Advancing Architecture, Engineering and Construction" (AdvanceAEC) (https://www.advanceaec.net). The Video of the Symposia shows different Presentations adressing Additive Manufacturing Construction.

Wire and Arc Additive Manufacturing (WAAM) of Complex Individualized Steel Components

29.01.2021
Unglaub, Julian; Associate Researcher,TU Braunschweig, Institute of Steel Structures
Jahns, Hendrik; PhD Researcher, TU Braunschweig, Institute of Steel Structures
Thiele, Klaus; Project Leader; TU Braunschweig, Institute of Steel Structures

Project A07 investigates structural design, WAAM methods and component testing of complex, large-scale, individualized steel components. The objective is to connect conventionally manufactured steel components and semi-finished products with additively manufactured, complex steel components The Institute of Steel Structures develops a novel test method based on fill field strain data. 

This test method considers potentially anisotropic component behaviour, surface topographies, geometric irregularities and residual stresses in addition to the relevant material properties.

Structural Timber by Individual Layer Fabrication (ILF)

22.01.2021
Bunzel, Frauke; Project leader; Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI
Asshoff, Carsten; Doctoral researcher; Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut WKI

In order to produce future-oriented timber structures in the building industry that meet the requirements of ecological and economic sustainability, an additive manufacturing process with wood chips is being developed using the new approach of individual layer fabrication (ILF). In first steps,established wood chip fractions and adhesive systems from the wood-based materials industry are used e. g. for particleboards or oriented strand boards.

For an acceptable adhesive-wood-chips ratio the amount of adhesive must be as low as possible, which is one of the challenges in developing ILF, see Fig. 1. In addition to the distribution of the adhesive over the wood chips surface, the intrusion behavior into the bulk is decisive. On the adhesive side, approaches such as reducing the viscosity by emulsifying with water or reducing the surface tension can lead to better processing results. In first steps, the wood chips should remain untreated. However, it is necessary to determine whether one wood chip fraction can be processed better than others. It is known that higher stiffness and strength can be produced by coarser wood chips fractions, which is also considered. The structural performance of the final component is not only determined by the strength and stiffness of the material but also significantly by the geometry of the part.

For the repeatable and automatable application of the adhesive from above onto the wood chips, a pre-selection of potential valves was made. First, the pressure-time, spray- and jet-valves are investigated. Each of the mentioned valves has advantages and disadvantages in the general application technique of liquids. Experiments will be conducted to determine which of the valves offers the best potential for the ILF process by varying materials and application parameters.

Process Control and Adaptive Path Planning for Additive Manufacturing Processes Based on Industrial Robots with an Extended Degree of Freedom

14.01.2021
Ekanayaka, Virama; Doctoral researcher, TU Braunschweig, Institute of Machine Tools and Production Technology (IWF)

The integration of robot-guided additive manufacturing in the construction industry increases the degree of automation and can thus lead to an increased productivity and increased component quality. In shotcrete 3D printing (SC3DP), reproducible manufacturing results and ensuring component qualities are a major challenge, as the properties of shotcrete depend on many different parameters (e.g. temperature, pressure, water-cement ratio, hardening accelerator).

The goal of this research project is to develop a reproducible, robot-guided shotcrete process based on multi-model adaptive path planning for the production of high-quality large and complex components. The core of this multi-model based path planning is the combination of geometric data and a physical material model into an application process model.

Within the scope of this research, a MATLAB framework is created which enables the coupling of the path planning to a Finite Element model. The STL data of the CAD Model to be printed represents the input used in the MATLAB framework.

Based on the printing path, a novel finite element approach was implemented which builds the mesh independently from the printed component’s ideal CAD geometry.  This has the clear advantage that the actual printed structure is simulated instead of the ideal target geometry. In this way, it is possible to directly simulate the material behavior during application and thus, to determine deviations from the CAD model.

By achieving better results from detailed FEA, the information on the obtained loads and deformations as seen in Figure 1, can be used within an additional feedback loop to adapt the printing path and printing parameters. Using those optimized paths will finally lead to better component quality, reduced test effort, and fewer buildability failures.

Integration of Additive Manufacturing in the Construction Process

08.01.2021
Mawas, Karam; Doctoral researcher, TU Braunschweig, Institute of Geodesy and Photogrammetry (IGP)
Gerke, Markus; Project leader, TU Braunschweig, Institute ofGeodesy and Photogrammetry (IGP)
Maboudi, Mehdi; Associated scientist, TU Braunschweig, Institute of Geodesy and Photogrammetry (IGP)
Riedel, Björn; Associated scientist, TU Braunschweig, Institute of Geodesy and Photogrammetry (IGP)

Additive Manufacturing (AM) allows us to print objects in unprecedented and novel ways, pushing the boundaries of what was previously possible in construction. By seamlessly embedding the process of the design directly into the printing process, ever more complex and free form objects can now be realized.  Nonetheless, AM remains a challenging and involved process that is influenced by a variety of factors. To ensure that a robust process is followed and that the printed object adheres to the model of the original, continuous monitoring and inspection of the process is required. 

Fig. 1 shows a freeform doubly-curved reinforced wall. A laser scanner was used to scan the object as it was constructed, after which it was compared directly to the 3D design model. The resultant model was then colorized based on Cloud to Cloud distance.

As we have stated, while 3D construction printing affords unprecedented freedom, it also poses new challenges for quality control. These challenges include collecting adequate data while ensuring the optimal time for data capturing, the size of the object, and its material properties, all while utilizing the proper type of sensor needed to control the structure's progress as it is being built. It is worth noting that many of these challenges are interrelated and interdependent. For instance, data capture must return reasonably rapid data within a predetermined time window so that the data acquisition of the object is in the range of the predefined time window. However, the type of sensor needed for a project is also dependent upon the size and material properties of the object in question.

One of the defined objectives of the Institute of Geodesy and Photogrammetry of TU is to continuously and effectively monitor the quality of 3d printed construction objects with the use of several different methods of data capturing. This includes the use of quality control during the printing process, as well as data capturing to inspect the object after printing is completed. For this process to be effective, several types of sensors are needed to be investigated, allowing for enhanced data capture, enhanced accuracy, and ongoing comparison with the designed model. Also, the challenges related to each step-in quality inspection process has to be considered.

Wire and Arc Additive Manufacturing (WAAM) of complex individualized steel components

01.01.2021
Christoph Müller, doctoral researcher, TU Braunschweig, Institute for Structural Design (ITE)

This sub-project of the SFB 277 deals with the design process of components for additive manufacturing by Wire and Arc Additive Manufacturing (WAAM). In contrast to large industrial sectors such as mechanical engineering, aeronautical engineering or medical technology, components in the construction industry have to be designed under different general conditions.

If no building system is used to create a structure, the components are usually individual. These components are usually used in the building as a single part or in small quantities. With the implementation of additive manufacturing processes, these components are usually free-form geometries that result from the fulfilment of a wide range of boundary conditions.

This includes improvements in material utilization through topology or shape optimization, geometries suitable for production and architectural design requirements.

Due to the frequently small number of identical components, the effort required to create the geometry must also be kept low, as otherwise the economic advantages of additive manufacturing are outweighed by the effort required in the design process.

The approach in this research project is to automate as many work steps as possible. As a further guideline, the respective effort per work step should be kept as low as possible. Topology optimization serves as an example here. Up to now, this has often been a decisive part of the design process. However, since geometry suitable for production is also required, time and resources can be saved by reducing the precision of topology optimization in favor of design speed.

For this purpose, a basic geometry is created that represents the design space. This geometry is transferred into a spatial framework and calculated by FEM for the corresponding load. Subsequently, the connection points are moved depending on the beam forces of the spatial beam system. In this process step, the points are considered as cellular automata and are all subject to the same set of rules.

AAEC Network Member Symposia

The TRR 277 is pleased to inform, that on Monday, 1st of February 2021, the first AAEC network member symposia will take place:

• Organisation: sfb/trr 277
• Agenda:
  1. Guest Keynotes by Ena Lloret-Fritschi and Fabian Meyer-Brötz
  2. TRR 277 selected project insides
  3. Discussion
• Time: 6:00-8:00 pm
• Further information under : https://www.advanceaec.net/aaec-network-member-symposia/

This event is open to all registered AdvanceAEC members.

If you haven’t registered yet, you are welcome to do so under:  https://www.advanceaec.net/register/

We are looking forward to your participation!

Architektur und Bau: Mehr Dialog zwischen Forschungsverbünden

Fünf Forschungsverbünde, unter anderem der TRR 277,  haben das „Research Network for Advancing Architecture, Engineering and Construction“ ins Leben gerufen. Das Netzwerk bringt internationale Wissenschaftlerinnen und Wissenschaftler zusammen, die danach streben, Architektur, Ingenieur- und Bauwesen durch digitale Technologien und einen interdisziplinären Ansatz voranzubringen. Es zielt darauf ab, die vielfältigen ökologischen, wirtschaftlichen und soziokulturellen Herausforderungen anzugehen, mit denen die Bauwelt konfrontiert ist.

Der vollständige Text ist unter folgendem Link zu finden: 

https://www.tu-braunschweig.de/abu/aktuelles-und-termine/news-detailansicht/ite-architektur-und-bau-mehr-dialog-zwischen-forschungsverbuenden

Mehr als ein Betondrucker

Interview mit einem Großgerät: das DBFL

16 Meter lang, neun Meter breit und ein Arbeitsraum von 370 Kubikmetern: Das Digital Building Fabrication Laboratory (DBFL) des Instituts für Tragwerksentwurf (ITE) der Technischen Universität Braunschweig ist ein echtes Großgerät. Es schlicht 3D-Betondrucker zu nennen, greift zu kurz. Für Dr. Jeldrik Mainka vom ITE ist es das „größte Schweizer Taschenmesser“, das er kennt. Warum das so ist, hat das DBFL unserer Redakteurin Bianca Loschinsky selbst erzählt.

Das vollständige Interview ist unter vollgendem Link zu finden:

https://magazin.tu-braunschweig.de/m-post/mehr-als-ein-betondrucker/

Best Presentation Award - Digital Concrete 2020

Der Beitrag "Studying the Bond Properties of Vertical Integrated Short Reinforcement in the Shotcrete 3D Printing Process" von Niklas Freund, Inka Dreßler und Dirk Lowke wurde auf der Digital Concrete 2020 mit dem Best Presentation Award ausgezeichnet. Die Digital Concrete ist eine internationale Konferenz, dessen Fokus auf der digitalen Fertigung zementgebundener Baustoffe liegt. Aufgrund der aktuellen Covid-19-Situation musste die diesjährige Konferenz auf ein vollständiges Onlineformat umgestellt werden.

Niklas Freund präsentierte die Ergebnisse experimenteller Untersuchungen, in denen das Verbundverhalten von Bewehrungsstäben untersucht wurde, die in den Shotcrete-3D-Printing-Prozess integriert wurden. Die Ergebnisse sind im Beitrag „Freund, N.; Dreßler, I.; Lowke, D.: Studying the Bond Properties of Vertical Integrated Short Reinforcement in the Shotcrete 3D Printing Process.“ veröffentlicht (https://www.researchgate.net/publication).

Die Integration von Bewehrungselementen in die bestehenden Beton-3D-Druckprozesse stellt ein sehr aktuelles und wichtiges Forschungsthema dar, welches durch Niklas Freund im Teilprojekt A04 des TRR 277 - „Additive Manufacturing in Construction (AMC)“ untersucht wird. Mehr Informationen erhalten Sie unter www.tu-braunschweig.de/trr277/projects/amc-structure/a-projects/a04

Das Institut für Tragwerksentwurf (ITE) der Technischen Universität Braunschweig ist beim diesjährigen Wettbewerb der Deutschen Gesellschaft für Nachhaltiges Bauen (DGNB) unter den drei Finalisten in der Kategorie „Forschung“. Der Beitrag des ITE befasst sich mit robotischer Fabrikation von Bauteilen aus Stampflehm.

Bis zum 13. September 2020 kann für das Projekt abgestimmt werden.

Abstimmen können Sie unter folgenden Link: https://blog.dgnb.de/sustainability-challenge-2020/kategorie-forschung/voting/

Digital Concrete 2020

Professor Dr.-Ing. Dirk Lowke, head of the institute of building materials, concrete construction and fire protection and head of the projects A01 and A04 within the TRR 277 was Keynote Speaker at this year's Digital Concrete 2020 conference. 

The whole presentation can be heard in full at the following links

https://digitalconcrete2020.com/

https://www.youtube.com/watch?time_continue=2359&v=lOS7cKndnA4&feature=emb_logo  

TRR 277 Youtube Channel