Transformation technology lightweight construction

Prof. Dr. Otto Huber führt durch die Leichtbau-Labore der Hochschule Landshut. © Hochschule Landshut

Around 130 lightweight construction experts recently met at the 11th Landshut Lightweight Construction Colloquium at Landshut University of Applied Sciences to exchange the latest findings and thus strengthen the transfer of knowledge and technology between industry and science. The great importance of lightweight construction shows that the German government also has its sights set on lightweight construction as a “transformation technology” and intends to adopt an overarching lightweight construction strategy this year that is designed to protect the climate, conserve resources and ensure recyclability.

Refractory high-tech origami was presented by Foldcore GmbH. © Landshut University of Applied Sciences
Refractory high-tech origami was presented by Foldcore GmbH.
© Landshut University of Applied Sciences

In two plenary lectures and 32 technical presentations in two parallel sessions as well as an accompanying trade exhibition, research institutions and companies provided insights into current research projects and developments ranging from materials research and multi-material design approaches to resource-conserving load-path-compliant design and new production technologies in industry to recycling. In addition, the focus was on networking and cross-industry exchange among lightweight construction experts.

University President Prof. Dr. Fritz Pörnbacher thanked all those involved who had contributed to once again creating an excellent platform for exchange between science and practice. The Lightweight Construction Colloquium – this year the title was “Lightweight Construction – Materials, Designs, Manufacturing Technologies” – has been organized by the Lightweight Construction Cluster of Landshut University of Applied Sciences every two years for the past 20 years at the university, with Prof. Dr. Otto Huber as the scientific director.

Lightweight construction strategy initiated by the German government

“More networking events like the Landshut Lightweight Construction Colloquium”, which has become a tradition, are needed to push the transformation technology of lightweight construction, Michael Kellner, Parliamentary State Secretary at the Federal Ministry of Economics and Climate Protection (BMWK), is convinced in his video message. Lightweight construction is of great importance for climate protection, resource efficiency and the resilience of the economy, he said, adding that the ministry had significantly expanded the Technology Transfer Program for Lightweight Construction (TTP LB), with a total budget of almost half a billion available for this purpose until 2026. In addition, the federal government is launching an overarching lightweight construction strategy this year.

An important topic in lightweight construction is the ability to recycle, “here we still have to do our homework,” Kellner is convinced. The turnaround towards a climate-neutral society and a resilient economy can only succeed if economic growth is sustainably decoupled from resource consumption. In this context, lightweight construction is a transformation technology and makes an important contribution to Germany’s development into a green lead market.

Details of the German government's planned lightweight construction strategy were presented by Werner Loscheider, head of department at the BMWK. © Landshut University of Applied Sciences
Details of the German government’s planned lightweight construction strategy were presented by Werner Loscheider, Head of Division at the BMWK.
© Landshut University of Applied Sciences

Werner Loscheider (Head of the Construction Industry, Resource Efficiency and Lightweight Construction Department at the BMWK), presented details of the federal government’s planned lightweight construction strategy: The focus in terms of content is on ecology with climate protection, resource conservation, recyclability, recycling, cascade promotion and knowledge transfer. It focuses on ecological and economic measurability in order to be able to identify along the entire life cycle where lightweight construction can save how much CO2 emissions. In the planned amendment of the TTP LB, industrial material efficiency, materials, design principles, digitalization and automation, as well as circular lightweight solutions and demonstration projects will be funding priorities. In addition, he presented the ministry’s national and international activities aimed at making even more people aware of the importance of lightweight construction – as at the Lightweight Construction Colloquium.

In his introduction, event initiator Prof. Dr. Otto Huber explained how the three basic topics of materials, designs and manufacturing technologies mentioned in the title of the event interact with partners in the activities of Landshut University of Applied Sciences’ research focus on lightweight construction. He demonstrated this with the example of research projects on cast-rolled magnesium sheets: from the analysis of the microstructure and mechanical properties of the material, to the modeling of the mechanical properties for FEM simulation, to the production of a hot-formed structural component and the modeling of fatigue strength.

Current research results on the development of a material model for the simulation of textured wrought magnesium alloys using the finite element method were later presented by Anton Nischler, while Florian Mader (both from Landshut University of Applied Sciences) dealt with the short-term fatigue of hot-formed structural components made of magnesium sheet.

Plenary lecture on limits of lightweight construction

In the first plenary lecture of the 11th Landshut Lightweight Construction Colloquium, Prof. Dr. Markus Zimmermann (TU Munich) dealt with “Design in lightweight construction: pushing the limits of what is possible”. He used detailed examples to show that a topology-optimized variant does not always have to offer the better solution. For example, planar structures can have higher stiffnesses than truss geometries for the same mass. Also, steel could be a better choice for a square tube because of appropriate requirements. In principle, as many degrees of freedom as possible should always be used.

Weight optimization means reducing stiffness to the limit of requirements. Here, the optimal material selection or optimal load paths and automated design procedures are defined by the requirements. For a lightweight robot arm, diagonal braces might or might not be necessary depending on the load requirements.

He recommends doing the goal setting top-down, but developing the degrees of freedom bottom-up. Above a certain level of complexity, the search for detailed solutions no longer makes sense. Then the overarching requirements would have to be considered first, then those in the subsystem, in components, and only then in detail. However, since the details are not known at the beginning, there is a lot of leeway in requirements modeling. One solution is to “phone up” detailed information such as stiffness, mass, and installation space in order to reduce the number of variants; it may also be possible to incorporate estimates via AI.

The trade exhibition of the 11th LLC provided an opportunity for exchange. © Landshut University of Applied Sciences
The trade exhibition of the 11th LLC provided an opportunity for exchange.
© Landshut University of Applied Sciences

High demands on materials and technology in aviation

In the second plenary lecture, Prof. Dr. Jörg Esslinger, MTU Aero Engines AG, dealt with technologies for environmentally friendly and competitive aircraft engines. Targets such as CO2 savings, zero-emission flying, reducing resource consumption and costs in production and operation mean major challenges – and new propulsion concepts always mean special requirements for materials, processes and design, as Prof. Dr. Esslinger emphasized.

For gas turbine engines, high temperatures mean high efficiency. Drive concepts of the future must deliver high performance and high load-bearing capacity with as little weight as possible; technologies such as the fuel cell mean new challenges for the technology, but also for the material and its qualification, for example in the handling of hydrogen. He cites economical manufacturing processes and materials, a long service life (an aircraft engine lasts around 40 years), robustness and reasonable maintenance as his goals.

In aviation, he said, 80 to 90 percent of the materials are metal, and the heavier the material, the more temperature resistant it is. They are constantly trying to find materials that are a little lighter and still temperature resistant. He sees an opportunity in intermetallics, the mixing of different metals, for example titanium and aluminum, to obtain better weight-specific properties. Fiber-reinforced materials, plastics or even ceramics could also be used, but so far these have been expensive to produce and damage tolerance is an issue. Additive manufacturing also offers potential, he said; it is possible to use the degrees of freedom, to get closer to the final contour and thus save material, and to produce better homogeneous intermetallic materials. The coating, which would bring significantly better properties, could also save material and thus weight.

Raw material and energy efficiency important topic in lightweight construction

In two parallel sessions, the colloquium offered a broad range of topics. The topic of raw material and energy efficiency played an important role. Paul Zwicklhuber (Engel Austria GmbH) presented, among other things, the production of a tape sandwich based on polypropylene, in which a flush connection between tape and injection molding is achieved. The cover layers improve the mechanical properties, and material savings of up to 50 percent can be achieved. The use of natural fibers is also possible, but expensive and complex to process, he said. Wulfram J. Schmucker (AT Avantgarde Technologie, Gilching, Germany) takes a similar view, saying that tailored fiber placement technology (TFP) can also be used in addition to conventional reinforcing fibers. This is achieved above all through the stress-oriented design of layers – not only at 90 degrees to each other – and of laminates and their production in series.

Tim Mayer (Fraunhofer IPA) showed how offcuts from fiber-reinforced organic sheets, which make up 30 to 50 percent of the automotive industry, can be pressed into new sheets. The direct processing of chopped glass fiber in injection molding, which saves process steps and costs and thus improves the ecological footprint, was demonstrated by Lazlo Giesgen (Kraus Maffei Technologies GmbH) and Jan Wiedemann (Wirthwein SE). Lightweight construction and fire protection play together in the folded paper cores of the company Foldcore GmbH and are “high-tech origami,” as Dr. Yves Klett explained in his presentation. The sandwich of a folded paper core with a geopolymer as matrix and two top layers of mica (mica) is said to be fire-resistant and feather-light, making it an excellent choice for sustainable fire protection. Compared to steel structures, the material has a much higher stiffness compared to the mass, and shows hardly any changes in the material and its properties at 850 degrees Celsius. This could save up to 80 percent of the weight. This offers a wide range of applications, from insulation for security doors to mobile applications and shipbuilding.

Wide range of other innovative lightweight construction topics

Other presentations dealt with the properties of fiber-plastic composites, for example the stiffness of ±45° FRP laminates (Felix Bandmayr, University of the German Armed Forces) or the process parameters of pre-impregnated carbon fiber rovings and their effects on the mechanical properties of high-pressure tanks (Youssef Mraidi, TU Munich).

Christoph Stangl reported on investigations of the microstructure and mechanical properties of a titanium-aluminum alloy. The mechanical properties and lightweight suitability of selected cast iron aluminides with regard to corrosion and high temperatures, for example for turbine blades or manifolds, were presented by Eva Kollmannsberger (both from Landshut University of Applied Sciences).

The more than 30 technical presentations offered a wide range of topics relevant to lightweight construction. Resistance spot welding of aluminum die casting and steel was a topic in the area of joining technology, as was the reinforcement of components through the connection of extruded FRP joints and hybrid CFRP-aluminum bonded joints. In addition to fatigue strength studies and innovative ways of design, the lightweight potential of additive manufacturing was also highlighted, and lightweight construction with thermoplastics, with cellular materials and hybrid structures was addressed.
In addition to the lectures, an accompanying trade exhibition offered the best opportunity to find out about new developments and to seek personal contact with exhibitors and speakers. In laboratory tours, the participants were able to get an idea of the technical equipment of the Lightweight Construction Competence Center at Landshut University of Applied Sciences. An accompanying conference volume was published for the two-day colloquium, in which 11 scientifically elaborated contributions by speakers were published and which can be obtained from the Lightweight Construction Cluster at Landshut University of Applied Sciences.