Lightweight and solar powered around the world

As early as 1891, aviation pioneer Otto Lilienthal covered 25 meters in a controlled glide flight. In 1894 his Normalsegelapparat (normal glider), weighing only 20 kilograms, went into mass production. A good 120 years later, the first solar aircraft circumnavigated the earth without any fuel – thanks to the extremely lightweight construction.

Source: Shutterstock/Sunny_Images

Lightweight construction – An all-round talent at saving energy and materials

Otto Lilienthal focused on the anatomy of birds’ wings during the construction of his Segelapparat – and since then nature has remained one of the most important models for lightweight construction. This is because the bionic principles allow the construction of components whose geometry permits a high loading capacity despite a maximum weight reduction. Lightweight construction therefore offers enormous potential for weight and energy savings in a wide range of areas. In this age of climate change and increasing scarcity of resources, lightweight construction materials are therefore an important contribution to sustainable management. Whether it is aircraft or automotive construction, wind power plants or in building construction, lightweight construction is used everywhere where people want to move forward. As providers of technology, mechanical and plant engineering is the driving force for lightweight construction engineering.

• The goal of lightweight construction is to save on raw materials, energy and costs in the production and use of the product.
• Lightweight construction reduces the use of materials to a minimum – nevertheless, the entire system must be able to meet requirements for rigidity, strength and dynamic stability over the product life.
• The development of lightweight construction structures requires a consistent coordination of design principles, materials and production.

Applications in Lightweight-Technology

Aerospace – Taking off is easy

An aircraft can take off as soon as the upthrust is greater than the aircraft’s weight including all transport goods on board. The lighter the aircraft, the less energy needed to overcome its gravitational pull. This is why lightweight construction is an indispensable technology, especially in aerospace in order to reduce fuel consumption and thus decrease costs.

Fly safely for longer with rotor blades made of composite materials. Source: Shutterstock/Helikopter
The savings potential in aviation is huge: Less material and fuel needed thanks to lightweight construction. Source: AIRBUS GROUP 2016

Production of fiber reinforced products

The industrialization of the production processes for manufacturing fiber reinforced plastics (composites) for volume productions has begun. The focus is on resin transfer molding (RTM) and compression molding processes for surface and structural components. In the press processes, the molding is carried out thermally (thermoplastic) or chemically (thermoset).

During resin transfer molding, an already pre-formed dry semi-finished textile product (fabrics, base layers, mesh, knitted fabric, etc.) is hermetically sealed in a two-part tool. Under high pressure, a resin is injected which, after chemical reaction, cures to become the finished component. The injection and curing time of the duromer resin determines the cycle time of the manufacturing process.

Typical applications for RTM processes are components with relatively complex geometry, such as wind turbine rotor blades, aircraft construction, railway vehicle components, automotive components, boat construction. Learn more about this topic in the detailed description on resin injection molding (RTM).

In the case of thermoplastic pressing, fibers or ready-made semi-finished textile articles are impregnated with molten thermoplastics and cooled into plate shapes. For molding, the plates are then heated and pressed in tempered tools into their final component contour. The basic principle of the process is the separation of the impregnation process from the molding process in the press.

Typical applications of thermoplastic molding are components in aircraft construction and automotive engineering, which need to be lightweight and stable. However due to the thermoplastic matrix, the components can generally not be subjected to high temperatures. Learn more about this topic in the detailed description on thermoplastic molding.

In the processing of thermoset semi-finished products, these are already pre-impregnated with a resin. They are heated in hot presses or in autoclaves and cured under pressure. The high temperatures lead to an irreversible chemical connection which, unlike thermoplastics, cannot be re-melted. Similarly, the basic principle here is the separation of the impregnation process from the molding process. More recent developments are designed to combine both process steps and thus reduce the cycle time.

Typical applications are components for the electrical industry, the sanitary sector, rail and commercial vehicles and increasingly the aircraft construction and automotive engineering industry. Due to the thermoset matrix, these components, unlike thermoplastics, are suitable for both higher and lower temperatures. Learn more about this topic in the detailed description on the processing of thermoset semi-finished products.

• In 2010, a 1% weight reduction on the aircraft fleet of Lufthansa AG would have lowered the kerosene costs by around EUR 50 million.
• In aerospace, each kilogram of load capacity produces costs of more than EUR 5,000.

Key lightweight construction materials in aircraft construction

Enormous savings potential in aerospace triggered major developments in lightweight construction. In aircraft construction, aluminum, titanium and fiber-reinforced plastics are the dominant lightweight construction materials. An increasing proportion of carbon fiber reinforced plastics (CFRP) is incorporated in wide-bodied aircrafts such as the Airbus A380 and the Boeing 787 Dreamliner. About 25 percent of the overall structure of the A380 consists of CFRP and the proportion in the Airbus A350 XWB is to be increased to more than 50 percent.

Production of fiber reinforced products

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“One kilogram of additional weight on board a long-haul aircraft costs the airline up to 300 dollars in fuel per year.”

John Leahy (Handelsblatt 27/10/2014)COO Airbus

Die casting – Modern production process for large-scale production

In the casting of metals, in addition to gravity processes, processes are also used in which the molten metal, preferably aluminum, magnesium or zinc, is fed into the mold at high speed and high pressure. The work is carried out with permanent molds. The production process is very well suited for large-scale production. Vehicle manufacturers in particular use die casting to manufacture complex structural components or engine blocks.

Aluminum can be alloyed for the casting with different chemical elements to influence the mechanical properties of the workpiece, e.g. castability, corrosion resistance and strength. The material properties can be further improved by an additional heat treatment. More than 75% of all aluminum castings are produced for the transport sector.

Caption: A die cast longitudinal support beam produced on the GDK 4400 VACURAL die casting system from Oskar Frech GmbH + Co. KG at Audi Münchsmünster, being placed in the deburring press. Source: Audi AG

Die casting machines – Heart of the aluminum foundry

Die casting machines are the heart of an aluminum foundry. Further plant modules for the production process are, among others, melting/dosing furnaces, extraction robots, deburring machines and spraying equipment.

Filling of a Vacural holding furnace for aluminum at Audi (part of the die casting process). Source: Audi AG

Die casting for automotive lightweight construction

Die casting processes are used in particular in automotive lightweight construction. For example, structural body parts and components for the power train are manufactured, or gear and axle housings, cross beams, spring supports. Even the entire skeleton of the body of a car can be produced today in lightweight casting construction.

Nature provides the best example for lightweight construction. Bionic principles allow the construction of components with geometries designed for high loading capacity with maximum weight reduction. Thus, resource efficiency and safety go hand in hand in automotive construction. At the same time, foundries reduce their energy and raw material costs.

Die cast strut supports of the Mercedes C class during quality inspection. Source: Daimler AG

Sources: German Foundy Association (BDG), Oskar Frech GmbH + Co. KG, VDMA Foundry Machinery Association

Automotive – Lightweight on four wheels

There are always millions of vehicles on the road across the globe. This is why the biggest market for lightweight construction is the transport sector – estimated to be at EUR 140 billion in 2020. The driving force is the automotive sector where metal lightweight construction prevails due to established production processes and good recyclability.

Steel continues to dominate in automotive construction. That is, until Audi’s designed its revolutionary aluminum car bodies in the 1990s. The spaceframe construction method, used then for the first time, is now widely used. Ford also uses aluminum for their global best-selling pick-up truck. The purely aluminum body saves 300 kilograms compared to the previous model.

 

Die casting – Modern production process for large-scale production

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Source: Audi AG
The efficient technology of lightweight construction: the right material in the right place.

Steel – High strength through rolling

Rolling systems enable highly-developed forming processes for high-strength steels

Hot and cold rolling are forming processes for the production of heavy plates, bands, profiles, steel bars and other semi-finished products for further industrial processing. The starting material is – by means of continuous casting – casted steel in the form of slabs or blocks. During hot rolling, the rolling stock is heated to about 1,250 degrees Celsius and reduced to the desired thickness in the rolling mill using pressure. Subsequently, these intermediates can be rolled even more thinly in the cold rolling mill. In further processing steps, such as annealing and finishing (re-rolling), it is now possible to produce new high-strength steel grades with a high level of fracture and crack resistance, which can be used in constructions where the highest demands are placed on safety.

A typical cold rolling mill consists mainly of a coiling unit, aligning station, roll stand, finishing equipment, possibly also scissors, drives and measuring technology.

7-stand hot-rolled strip finishing mill for production of steel bands with a width of 800 to 1,890 mm (annual output: 5.3 million tons). Source: SMS group

Strip processing lines

Process steps for further refining of steel strips are carried out on strip processing lines. They can be used to produce, for example, galvanized sheets or bands of the highest quality.

High-strength steels for innovative lightweight construction

Today, modern steel processing plants can be used to manufacture a wide range of steels while saving resources. These steels have tailor-made properties for special applications. They are mainly processed into safety-relevant components for passenger cars, commercial vehicles, ships or wind turbines. In the case of cars, for example, engine hoods, door impact beams, wishbones, spring and trailing links as well as gear shafts are manufactured as lightweight constructions using high-strength steel.

Thus, less steel is required for the same function, which reduces the weight by up to 50 percent and conserves resources.

Final stands of the hot strip rolling mill Çolakoğlu Metalurji in Turkey: The hot strip rolling mill supplied by the SMS group in 2010 rolls steel strips with widths of 800 to 1,650 mm (capacity: 3 million tons per year). Source: SMS group
The 5-stand cold tandem mill with a capacity of 2.1 million tons/year was commissioned by the SMS group at MMK in Russia in 2011. Here, steel strips with a width of 800 to 1,850 mm are cold rolled. Source: SMS group

Sources: Salzgitter AG, SMS group, Steel Information Center/German Steel Federation, VDMA Metallurgical Plants and Rolling Mills Association

Fiber reinforced plastics in automobiles

Fiber reinforced plastic parts also play an important role in automotive construction. In its development of the electric and hybrid vehicles i3 and i8, BMW has used carbon fiber reinforced plastic and developed a passenger compartment in series production for the first time. Mechanical and plant engineering companies played a significant role in the process development and automation of the production steps. The boundaries of what is feasible have been continuously pushed and important lessons have been learned for future use of fiber composites.

 

Steel – High strength through rolling

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To compensate for the heavy weight of the battery, the passenger compartment of the BMW i3 is made of carbon fiber reinforced plastics. Source: BMW AG

What benefits do lightweight construction add to aircraft and automotive construction?

 

100 kg
lighter

means a car used ½ liter less fuel per 100 kilometers.

1.974 l
of kerosene

can be saved per aircraft per year with 20 kilograms less weight on the A320.

500 €
is the additional cost

the aviation industry will gladly spend per kilogram it saves in weight.

8,8 g
CO₂/km

can be saved per 100 kilograms less weight in a car.

5 €
is the additional cost

the auto industry will gladly spend per kilogram it saves in weight.

5000 €
is the additional cost

the aerospace industry will gladly spend per kilogram it saves in weight.

Hybrid lightweight construction – The best of everything with multi-material design

In the future, there will be fewer vehicles which are made entirely of just one material. Through a combination of different materials, the advantages of each material are fully utilized and combined, without losing sight of the cost implications.

The aim is the appropriate material at an acceptable price, in the smallest possible quantity, in the right place. Particular challenges for such a hybrid lightweight construction lie in the joining and bonding technology of different materials. Processes using screws and rivets are increasingly being supplemented by adhesive technologies and laser processes. The VDMA brings together interested parties from the mechanical engineering, user industries and research facilities in its international Hybrid Lightweight Technologies working group.

 

Source: BMW AG
The multi-material design of the BMW 7 Series combines aluminum, carbon fiber reinforced plastics and steel.

Video statements on the founding of the VDMA Hybrid Lightweight Technologies working group

In January 2016, the Composite Technology forum expanded thematically and became part of the Hybrid Lightweight Technologies working group. Board members and the project manager explain the motivation and objectives of the working group.

“The goal of the Hybrid Lightweight Technologies working group is not the success of the individual, but the joint development of fields of technology for user industries and mechanical engineering.”

Peter EggerEngel Austria GmbH and Chair of the Board of the VDMA Hybrid Lightweight Technologies working group

3D printing makes bionic lightweight construction possible

3D printing processes offer a variety of innovative technologies with tremendous potential in lightweight construction. Construction is modeled on nature herself – also known as “bionic lightweight construction” – in many cases, it is only possible through the layering 3D printing process.

For many years, mechanical engineering has been employing the appropriate industrial processes with metallic materials and plastics in the construction of prototypes. Without the use of tools, complex components are created in the layering process, which would not be feasible using abrasive processes such as milling or turning. Almost with unlimited options, cavities, honeycomb and grid structures or air and coolant channels can be integrated into components in the 3D printing process; wall thickness can be varied or neuralgic junctions can be reinforced in car bodies. Additive manufacturing can process a wide range of high-strength metal alloys (including titanium, aluminum and steel alloys) and high-performance plastics. Since tool and mold construction is no longer required, small batch production and individual parts can be implemented cost-effectively.

Laser metal fusion – the laser establishes the desired shape in a powder bed. Source: TRUMPF Laser- und Systemtechnik GmbH
Mounting bracket: Additive-manufactured material is now only found along the power flow lines – that saves weight. Source: TRUMPF Laser- und Systemtechnik GmbH
Grid structures – complex structures cannot be produced using abrasive techniques. 3D printing is needed. Source: Renishaw
Heat exchanger – additive manufacturing offers enormous spatial design potential; Source: Concept Laser GmbH

Additive manufacturing

Additive manufacturing is an innovative technology with high potential in lightweight construction. It is also known as 3D printing. In additive manufacturing, components are created by fusing plastic or metal powders into thousands of razor-thin layers. In most cases, lasers are used. The lasers draw the information on where the powder is to be exposed directly from the design data. Unexposed powder can then be removed. Cavities, channels, grids or randomly-shaped walls remain in the component.

The lighter the desired component is to be, the less material is used and the faster the component is finished. 3D printing can be summarized as follows: the lighter, the more cost effective!

3D printing makes bionic lightweight construction possible

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Source: Steinbach AG
Delicate plastic structures with special functionalities in 3D printing

Textile machinery: starting point for resource-efficient construction

Steel and prestressed concrete are among the most important materials in building construction. Because of the low strength of concrete, it must be reinforced in areas with high load stresses. Such reinforcements are usually made of steel. The problem: steel rusts. In order to protect the concrete reinforcement from corrosion, the concrete components must be appropriately thick enough. This results in component thicknesses of over 90 mm and a correspondingly heavier weight. The alternative: The building material is no longer reinforced with steel but with textile-reinforced structures made of carbon and glass fibers, which cannot rust. In addition, this reinforcement can be positioned depending on demands. This allows a component thickness of only 20 mm and thus significantly less weight. The transport costs and the associated exhaust emissions are reduced.

A warp knitting machine for the manufacturing of textile fabrics, for example, for concrete reinforcement; Source: KARL MAYER Textilmaschinenfabrik GmbH

With textile-reinforced concrete, the favorable material properties of concrete are combined with those of the technical textiles. These textiles consist, for example, of glass or carbon fibers.

Yarns are needed to produce textiles. A yarn combines many fine fibers into fiber bundles. These yarns are then processed on textile machinery, specifically with warp knitting machines, into net-like cores or even three-dimensional spacer fabrics.

Non-corrosive and lightweight: Textile structures reinforce concrete; Source: Groz-Beckert KG

Composite over steel

Textile-reinforced concrete has already proven itself in practice. A specific example: A pedestrian bridge in the Swabian town of Albstadt-Lautlingen, built in 2010. The one-hundred-meter-long bridge has an epoxy-resin-impregnated fiberglass fabric on the upper and lower side of the bridge slab, and a stirrup reinforcement in the bridge’s ribs. A total of 3,800 m² of the textile fabric was installed in the six sections of the bridge. An additional 3,800 m² was required for testing including strength verification.

The longest textile-reinforced bridge in the world in Albstadt-Lautlingen; Source: Groz-Beckert KG

“If it were a conventional bridge made of reinforced concrete, the superstructure would have weighed roughly 350 tons. The textile-reinforced bridge, on the other hand, only comes in at 200 tons – we saved nearly 40% concrete.”

Roland KarleHead of the Competence Center for Textile Construction at Groz-Beckert

2016 Zukunftspreis

In 2016, the Deutsche Zukunftspreis was awarded to a research team from Dresden. Federal President Gauck honored them for their project named “Carbon concrete, a fascinating material – economical, efficient, attractive”. The three professors, Chokri Cherif, Manfred Curbach and Peter Offermann from the Technische Universität Dresden, are pursuing the goal of replacing around 20 percent of reinforced concrete with carbon concrete in the near future.

Construction with textile structures

In construction, concrete must be reinforced with steel. However, this has serious disadvantages because the material is very heavy and the corrosion of the steel can lead to dangerous cracks or unsightly chipping of the concrete. A welcome alternative is textile-reinforced concrete. This innovative solution offers significant advantages: primarily a significant weight reduction and a longer service life.

This is why there are many application possibilities for lightweight construction, particularly in the construction sector. Thus, textile-reinforced structures are used in the roofing of stadiums and large halls as well as in structural engineering.

Textile machinery: starting point for resource-efficient construction

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Mechanical engineering – Making the “bigger picture” happen

Many lightweight constructions are as complex as the technologies required to manufacture these components. The mechanical engineers have this expertise.

If a production process is to be executed efficiently from start to finish, all those involved in the individual process steps have to collaborate closely in the development of the technology. The mechanical engineers always focus on the common objectives. They derive their innovative strength from their self-perception – that they must constantly find new technological answers to the new challenges.

“Holistic process observations and concepts for complete production systems are the major challenges facing companies in the German mechanical engineering sector.”

Lothar GräbenerSchuler Pressen GmbH and member of the Board of the Hybrid Lightweight Technologies working group

Visions

Otto Lilienthal could only dream of altitudes above 800 meters. That is as high as today’s skyscrapers. Elevators which can travel to such heights can no longer be made due to excessive intrinsic steel cable weights. Intermediate transfer stations are necessary. Thanks to significantly lighter carbon fiber cables and the technical expertise of mechanical engineering, people will arrive at their destination in the future with fewer station changes.

A corresponding functional principle is also to be used for a space elevator – for transporting goods or for releasing geostationary satellites. In 1895, the Russian mathematics teacher and space pioneer Konstantin Eduardowitsch Ziolkowski, a contemporary of Lilienthal, took the first steps in this direction. NASA and other organizations are now working on the concept of a space elevator. The cables would then most likely be made out of carbon nanotubes…

There are still lots of unsolved problems, but there is plenty of potential for lightweight construction!

 

Authors

Dr. Walter Begemann

Project Manager, VDMA Hybrid Lightweight Technologies

From 2009 to 2012, Dr. Walter Begemann served as project manager for electromobility at VDMA. Subsequently, the production of fiber composite components became the focus of the Composite Technology forum. In 2016, the area was extended to include the combination of composites with metals.

Ines Polak

VDMA Foundry Machinery, Metallurgical Plants and Rolling Mills and Thermo Process Technology

Project Manager market information, statistics and marketing, Foundry Machinery Associations, Metallurgical Plants and Rolling Mills, Thermo Process Technology.
Ines Polak has been responsible for sector-specific economic and market information as well as marketing projects in these trade associations since 2009.

Nicolai Strauch

VDMA Textile Machinery Trade Association PR Manager, Textile Machinery Association

Nicolai Strauch has worked at VDMA since 2006. In addition to public relations, his field of work includes market monitoring and market information, events, the Chinese liaison office, as well as the next generation of engineers.

Ina Vettkötter

VDMA Plastics and Rubber Machinery Association, Project Manager Communications

Ina Vettkötter has worked in the VDMA Plastics and Rubber Machinery Association since 1993. Since 2011, she has been responsible for the design and implementation of communication and press projects at major trade fairs in Germany and abroad. Her field of work also includes plastics recycling.

Interesting links

VDMA Metallurgy

VDMA Metallurgy is the joint platform of metallurgical machinery producers. It comprises the Foundry Machinery, Metallurgical Plants and Rolling Mills as well as Thermo Process Technology Associations with a total of approximately 150 members.

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Plastics and Rubber Machinery Association

Roughly 200 manufacturers of plastics and rubber machinery are organized in the trade association.

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Hybrid Lightweight Technologies Working Group

The working group is made up of roughly 200 members and includes companies from more than 10 VDMA trade associations and user industries as well as research institutes collaborate.

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Textile Machinery Association

About 120 of the most important manufacturers of textile machinery and accessories are organized in the trade association. The members are primarily medium-sized companies which represent about 90 percent of the total volume of the sector.

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Additive Manufacturing Working Group

The Additive Manufacturing Association in the VDMA offers its members from industry and scientific research a variety of services related to industrial 3D printing technologies. It is the cross-industry platform where potential users and development partners meet and work together.

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