In petroleum refining or steel production, countless carbon-based compounds are produced that can no longer be used
– thanks to a new application, they could be used to make lightweight materials made of carbon fiber.

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Cars are getting heavier. In the same category, the change compared to 30 years ago is dramatic: the weight of cars has increased by more than 15 percent. This goes against the principle of making vehicles more efficient to reduce greenhouse gas emissions and increase the range of electric vehicles. The solution to this problem would be to use lighter materials that also meet safety requirements, but the problem is that they are expensive at the moment, so they would add a lot to the price of the car.

This was noticed by the US Department of Energy, which is why four years ago it launched a study to find ways to make cars more efficient and reduce fuel consumption by reducing their overall weight. A heavier car requires a bigger engine, stronger brakes, etc., so reducing the weight of the body or other components has a ripple effect that produces additional weight savings. The ministry has therefore urged the development of lightweight structural materials that meet the safety requirements of today’s conventional steel panels, but can be produced cheaply enough to replace steel completely in standard vehicles. This research has come to an end early 2022.

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Composites made of carbon fibers are not a new idea – you can find them in tennis rackets or bicycles. The question is, why not in cars? You can see the answer above; due to the relatively high production costs (compared to steel or aluminum structural elements), such composites have so far only been used in a few very expensive models. Making a pickup truck out of carbon fiber instead of steel, for example, would roughly double the cost. If you want to cut these costs, you need two things: a low-cost starting material and a relatively simple processing method.

One source of low-cost starting material is the waste material left over from petroleum refining, which refineries currently supply for low-value applications such as asphalting, or even treat as waste. This material is unusable for further combustion, too dirty to be used as a fuel, and this is especially true with tightening environmental regulations. Another alternative, which the team also tested, is a by-product of coking coal used in steel production.

So the cheap raw material is there, but what about the process? According to the researchers, making carbon fiber requires minimal investment, both in terms of energy and the complexity of the process. The waste materials in question are made up of different molecules – and changing their size or shape dramatically changes their properties.

By carefully modeling the ways bonds form and crosslink between the constituent molecules, the researchers have developed a method to predict how a given processing condition will affect the properties of the resulting fiber. As the researchers explained, the results were predicted with “startling” accuracy – characteristics such as fiber density or elasticity could all be predicted. The new carbon fibre can therefore not only be produced cheaply, but also offers additional advantages over conventional carbon fiber materials, as it can have compressive strength, meaning it can be used for load-bearing applications. This is not only good for the automotive industry, but opens up the possibility for a whole range of potential applications.

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