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Materials Research The Importance of Materials Research for Safety in Autonomous Driving

Editor: MA Alexander Stark

Some road users are uncomfortable with the idea of autonomous driving becoming a reality soon. Innovative construction and well-tested materials can improve passenger safety. In this context, multi-materials for lightweight construction are playing an increasingly important role.

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In future, the interiors of vehicles will be completely different, as the passengers no longer necessarily sit upright oriented in the direction of travel, but travel from A to B comfortably in a lying position or reading. New concepts and materials are required to protect the occupants in the event of a braking maneuver or a crash.
In future, the interiors of vehicles will be completely different, as the passengers no longer necessarily sit upright oriented in the direction of travel, but travel from A to B comfortably in a lying position or reading. New concepts and materials are required to protect the occupants in the event of a braking maneuver or a crash.
(Bild: Pixabay / CC0 )

Virtually all high-turnover industries in Germany are depending on innovations made in materials research to maintain or expand their leading position in global competition. High-performance materials with new properties are therefore in demand. For example, in automotive engineering, aviation, the electrical industry or for medical and environmental technology, they are the basis of future-proof solutions. The second driving force is digitization and the opportunities it offers by creating more efficient production processes and new business models. In order to manufacture tailor-made products according to individual customer requirements economically, experts need a profound understanding of the material properties and thus of the internal structure of the materials.

Sensor Lenses from the 3D Printer

Ensuring the safety of vehicle occupants and passers-by is a challenge when it comes to self-driving cars. In future, the interiors of the vehicles will be completely different, as the passengers no longer necessarily sit upright and oriented towards in the direction of travel, but they rather travel from A to B comfortably in a lying position or reading. To protect the occupants in the event of a braking maneuver or crash, new concepts and materials are required. Sensors that ensure the safety of passers-by must function reliably in all weather conditions, including fog, snow and heavy rainfall. At the same time, it is essential that all electronic systems are protected against hacker attacks or data loss, if we want to turn today's approaches into tomorrow's reality.

In vehicle and aircraft construction, multi-material lightweight materials are playing an increasingly important role. Developers use the individual advantages of different materials, for example in hybrid designs, to open up new fields of applications. Experts consider new production technologies such as additive manufacturing as particularly promising. In this production process, the workpieces are designed on the computer and the acquired data is applied in layers using a 3D printer. This technology makes it possible to produce very small components with dimensions of less than a thousandth of a millimeter. This results in particularly stable materials consisting of miniature grids and frameworks, as well as in very small, ultra-precise lenses for sensors and optics, but also in tiny frameworks for the propagation of cells in body-like environments.

With regard to the energy transition, advanced materials will also be required to increase efficiency and environmental sustainability, and for the transport and storage of energy. Batteries for vehicles must not only be lighter and more environmentally friendly — they must also not burst into flames or release harmful substances in the event of an accident. The same applies to fuel cells, whose service lives have been greatly increased in recent years thanks to new materials and production processes.

Material Failure: Development of New Measuring Methods

Prof. Dr. Peter Gumbsch and his research team are working on numerous of these innovation topics under the motto "more economical, more efficient and safer". His research supports industrial concepts for self-driving vehicles, resource-saving buildings and power plants and designs materials with completely new properties. His research groups at the Karlsruhe Institute of Technology (KIT) and the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg ensure that self-driving cars become safer, turbines lower losses, pumps and fuel cells more durable.

To achieve these goals, individual components up to complete structures or vehicles are tested thousands of times on test benches. Prof. Gumbsch's teams develop new measuring methods to understand the details of material failures. The time required for these tests and thus the costs involved are considerable. Therefore, the scientists create highly complex computer models that help them predict the deformation and failure of materials in advance. This approach saves time and resources. Their models set new standards in research and industry in terms of precision and reliability.

Related to: Possibilities of Lightweight Material Construction

Detailed Prediction of Crash Behavior

In day-to-day business, Peter Gumbsch and his teams focus on what happens "when things go wrong", i.e. when materials or material composites are under stress. Whether it's fluctuating exposure to extreme heat, continuous mechanical stress or a sudden crash — at first, they look at physical and mechanical properties to acquire a model that precisely describes the material and its behavior under stress and thus makes it predictable. One example is welding spots in automotive engineering. Such places are typically not cut out for a crash situation. A weld seam is used to connect two sheets in a stable manner. Nevertheless, a weld seam can also serve as a predetermined breaking point by yielding in the event of an impact.

If the connection is too tight, the entire structure could be catapulted into the interior in an accident. Vehicle manufacturers want to avoid this under all circumstances. Fraunhofer researchers in Freiburg developed a computer model to precisely predict the crash behavior of welding spots. The model helps car designers to develop new approaches. The same was achieved, for instance, for the prediction of the deformation and fracture behavior of aluminium rims.

Developing Reliable Models

Fiber composites offer new possibilities for the lightweight construction of vehicles or wind turbine blades, but they also pose new safety challenges. With the aid of a thermal camera, Prof. Gumbsch and his team were able to prove how and where the energy of an impact is converted into heat in a composite material. Since such materials are very heat-sensitive and conduct heat very poorly, the energy generated locally at the fracture point apparently plays a very central role in the fracturing of the material. So far, however, exactly this aspect has not been considered in crash models. The researchers are therefore eager on integrating this objective into their computer models. Their goal is to produce novel composite materials with improved material properties.

The way the fibers are processed, their orientation towards each other and their intertwining also effect stability and breakage behavior. In her doctorate, Zalikha Murni Abdul Hamid, supported by the Hector Fellow Academy, investigates how and under what conditions various composites tear. At the same time, she is developing a prediction model that will later make it possible to design lightweight components with precisely defined features on a computer. In the future, such a model would help to predict the reliability of composites under various loads and thus make a significant contribution to the safety of these materials and save considerable costs.

Related to: Lightweight Construction is Essential

More Efficient Energy Generation Is a Prerequisite

Prof. Gumbsch believes that a look into the detailed properties of the materials is also an important pillar for establishing a more efficient energy production. For instance, tremendous forces act in the bearings of wind turbines. On the one hand, this leads to a lot of energy to be lost through friction and on the other hand, the bearings deform and wear out. These effects affect an infinite number of technical applications. However, the physical phenomena involved are not yet understood very well. Therefore, Prof. Gumbsch and his colleagues at KIT analyze what happens under the surface of the stressed materials. It is only in recent years that researchers have been able to detect changes in the interior of the deformed materials with the aid of special imaging methods. Copper as a soft metal and sapphire as an extremely hard counterpart serve as example systems that provide decisive physical data for the subsequent model calculations.

On the Trail of the Material of the Future

The Hector Fellow Academy provides an intensive and creative exchange across disciplinary boundaries: an idea for cooperation between Prof. Dr. Peter Gumbsch and Prof. Dr. Martin Wegener from the Institute of Applied Physics and Institute of Nanotechnology at KIT was born. Their common goal is to develop meta-materials with special mechanical properties. The researchers wondered whether and how collapsible, unstable structures could be used in practice.

As a result, their project team presented three-dimensional grid shapes with surprising properties: Some are suitable as reusable, lightweight shock absorbers and the other as honeycomb camouflage covers concealing underlying structures. Prof. Wegener's team of experts is able to produce these materials as high-precision three-dimensional nanostructures using a 3D laser printing process developed at the KIT.

The researchers are certain that they are on the track of a material of the future. They are currently examining to what extent the main features of the reusable shock absorber and the camouflage structure can also be used commercially. The unconventional project of a stable shock absorber made of unstable basic structures is regarded as a prime example of the direction in which materials research will develop in the future: Complex computer models allow new test procedures, unusual material designs and unusual material combinations that later prove themselves in practice.

Increasing digitalization is already enabling more effective manufacturing strategies and new business ideas that result in solutions tailored specifically to the customers’ demands. Industry and trade must seize these opportunities and convert them into innovative products and services.

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