A special Dutch steel protect cars during collisions

Cars have become hundreds of kilos heavier over the years. Engineers are therefore working hard to reduce the weight of our four-wheelers without compromising efficiency and costs. Bernard Ennis, senior researcher at Tata Steel, is one of them. He came up with a colleague with the concept of crushable steel, which is both rigid and elastic. “It can absorb collision forces much better.”

Since 2016, new cars have become at least 400 kilograms heavier, from 1553 kilograms to 1947 kilograms in 2023. One reason for this growth is the increase in hybrids, plug-in hybrids, and fully electric cars on the market. Due to their heavy batteries, these vehicles weigh considerably more than cars with only an internal combustion engine. This is a critical downside, as a heavier weight leads to higher energy consumption, more significant wear and tear, and increased costs for both production and use.

When Ennis read an article about metamaterials, he had a eureka moment. Metamaterials are artificial materials with properties that regular materials do not possess due to their specific geometric properties. They can react unnaturally. In conditions where a traditional material cell expands under pressure, a metamaterial can be designed to shrink.

'Smart' steel

“While reading the article, an idea suddenly came to me,” he begins. ”What happens if the properties of metamaterials are combined with steel? Could that mean more safety in the car's crumple zone?” The crumple zone, he explains, is the part of a car designed to dent in a controlled manner in the event of a collision so that the energy is absorbed during the impact. For vehicles with an internal combustion engine, the engine also absorbs energy. Still, an electric motor has much less mass, so the energy must be absorbed differently in the event of a collision.

His curiosity led him to Corentin Coulais, a researcher at the University of Amsterdam who specializes in metamaterials, in 2017. Together, they devised a design for crumple steel with specially shaped holes in the material, which comprises different layers.

Safer and more sustainable

The main advantage of crumple zones is the improved safety for passengers because they absorb the impact of a collision much more gradually. “We discovered that we can absorb 20 times as much energy with the same mass at both low and high speeds,” says the inventor. So, crumple zones can absorb the force of a collision 20 times better. Then, there are the advantages in terms of sustainability. After all, crumple zones are a lot lighter than regular steel. “These constructions are lighter and therefore more sustainable.”

Raised eyebrows

The inventor, convinced of his idea, has come up against many raised eyebrows in recent years. “I made many prototypes, but there I was, working with rubber objects at a steel company. Many people thought I was crazy; they didn't see the potential of my idea.”

Persevere, he thought. Together with colleagues, he conducted laboratory-scale tests and simulations. The next step is designing protection for the battery, a so-called battery box, using metamaterials. Suppose a car is involved in a collision; there is an increased risk of fire hazard from the battery. “Because batteries are under the passengers' seats, there is little time to evacuate. Therefore, protecting the battery is very important.”

Ideally, you want to collect or distribute as much energy as possible over a large surface area. That is precisely where the properties of metamaterials excel.

Ennis: “The most important question is how the price of this innovation compares to the costs of current materials and processes. Production can start as soon as we have an answer to that.”

In talks with the car industry

Ennis is in talks with the car industry. He cannot mention any names yet, ”but think of companies that supply parts to OEMs (Original Equipment Manufacturers). Tata Steel also remains an essential player in this project.”

Inventor at heart

The fact that the idea for crumple zones originated in the head of the Tata Steel engineer is anything but a coincidence. Ennis is an inventor at heart and has several patents to his name. In addition to working on crushable steel, he worked on several other innovation projects at Tata Steel. Previously, he developed vacuum shock absorbers - fuses capable of handling extremely high voltages - for Alstom (England). He also created a new type of high-voltage switch for factory complexes and alloys that can better withstand metal fatigue in seawater.

But the crushable steel is a gem with a lot of potential. The research results were published in the renowned journal Nature. In collaboration with researchers at the University of Amsterdam, Tata Steel founded a new startup: Metamaterial Works. The startup will work on various applications, from protecting batteries in electric cars to improving crash barriers and structures that make buildings more resistant to earthquakes.

The official founding of the company is planned for this summer. Ennis' most important message? “Believe in the idea you have in mind and make sure you maintain the connection with others. You have long since seen why it works, but that does not mean that others will see it, too. As Johan Cruyff said, ‘You will only see it when you understand it.’ I cannot explain it any better,” the inventor smiles.

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