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Plastics properties

Carbon fiber, Kevlar, graphene – modern materials used in the automotive industry

14 November 2022

At a time when energy efficiency is becoming increasingly important, the automotive industry is implementing new car manufacturing technologies and looking for innovative materials to make cars safer yet lighter. In addition to solutions used in the aerospace industry, such as carbon fibers and Kevlar, innovative foamed plastics may prove to be an interesting option. 

Carbon fiber – properties and applications 

Carbon fiber or CFRP is actually a carbon fiber-reinforced composite. It usually takes the form of a multilayer resin-coated fabric, which has minimal weight, yet remarkable mechanical resistance. Carbon has up to four times the tensile strength of high-grade steel, while also being extremely flexible, which has led to its use in aircraft, spacecraft, and sports cars, among other applications. The most famous example of a car for which carbon fiber was used is the Lexus LFA. Its body consists of 65% of this very material.

Production of carbon fiber components – how is it done and what is made of carbon composite? 

The strength of carbon fiber allows it not only to be used to make car body parts, such as the roof or trunk lid, but also some mechanical parts or interior components, including pillars or floor panels. To manufacture parts from carbon, molds are used that correspond to the shape of the final product. These can be filled in four different ways. The first and most labor-intensive of these involves laying down layers of fabric, which are then hand-saturated with resin. The second method involves the use of so-called pre-impregnates, or layers pre-saturated with resin. The third technology is Resin Transfer Molding, which involves pressure-filling a mold with already placed layers of fabric with resin. The last and fastest method called C-SMC (Carbon Fiber Reinforced Sheet Molding Compound) involves injecting resin mixed with finely cut fibers into a mold. However, the disadvantage of composite reinforcement made using this method is the lower strength of the final product. The final stage of production in either case is annealing the carbon fiber parts for several hours at a temperature of about 180°C. Once the resin has cured, the parts can then be mechanically processed. 

Is carbon fiber harmful? 

Carbon fiber has a number of excellent properties, but many people wonder about its impact on human health. Finished, resin-coated carbon products are completely safe. Carbon fibers exert harmful effects only at the manufacturing stage, when they are cut. Microfibers cause skin irritation and damage, which can lead to further infections. Fiberglass dust also has an irritating effect on the eyes, and – if inhaled with air for a long time – it can even cause fibrosis and lung cancer. That's why people who work with carbon fiber products on a daily basis wear appropriate protective clothing and a mask equipped with a special filter.  

Kevlar – application in car construction 

What is Kevlar, also known as aramid fibers? It's a synthetic polymer that was accidentally invented in the 1960s in the United States. At the time, a team of researchers was looking for a lightweight and strong material that could replace rubber in tires, which was supposed to make it possible to reduce gasoline consumption. The result was a very strong polymer with a high degree of particle ordering, which is more than five times lighter than steel and has a very high tensile strength of as much as 3,620 MPa. It takes twice the force of carbon fiber and as much as four times that of steel to break aramid fibers. In automotive applications, it is used extensively in the construction of lightweight racing and performance car bodies, but not only. It can also be found in popular car models, where it is used to reinforce critical components such as timing belts and radiator hoses. In motorsports, it also has the important function of protecting the clutch as a component of special linings. 

Padding the clutch with Kevlar – what does it do? 

The Kevlar fiber friction lining is very durable even at high temperatures, so it easily transmits more torque to high-powered engines, such as those used in sports cars or off-road vehicles. It provides a significantly longer clutch life than traditional linings, so it is recommended for harsh operating conditions. 

Properties and applications of graphene 

Graphene is a super material, which has not yet been fully explored by modern science for all its possibilities. The material, with a two-dimensional structure composed of carbon molecules forming a pattern of perfect hexagons, is both lighter and stronger than carbon fiber and Kevlar. One square kilometer of graphene weighs only 757 grams, yet it is extremely flexible and has excellent electrical properties. It is an ideal material not only for the production of super-lightweight bodies, but in the future it could also be used to produce, for example, extremely efficient batteries or even roll-up touchscreen displays. Currently, the latest applications of graphene in the automotive industry include the production of anti-corrosive car paints, wheel arches, as well as the experimental plating of a lightweight single-seater racer. The graphene used in its production was said to be 20% lighter than carbon fiber and up to 200 times stronger than steel. 

Foamed polypropylene EPP – material properties and applications 

Among the material innovations in the automotive industry, there can be no shortage of expanded polypropylene EPP, a material that initially gained particular recognition in modeling and later in car bumper structures. The material's lightweight, foamed structure is composed of 95% air, so EPP automotive components are about 50% lighter than their counterparts made of traditional plastics, yet they are extremely strong. The combination of mechanical resistance and minimal weight makes EPP sometimes compared to carbon fiber. Its important distinguishing feature is its so-called shape memory. It does not permanently deform under impact, but returns to its initial form. Thanks to this feature, it has already revolutionized the production of components responsible for safety, such as headrests, seat bases, car pillars and car door panels. Due to its excellent insulating, acoustic and electrical properties, the material has also found future applications in the production of battery packs for electric cars, as well as hydrogen storage. The manufacturing process for EPP components is very easy and involves foaming polypropylene resin and then injecting the foam into a mold under low pressure. What’s worth highlighting, the material is optimal from the economical point of view for industrial mass production and widely available at raw material producers in many varieties.  

Carbon fiber, graphene, Kevlar or EPP – applications and properties 

The technological race to finalize an ultralight and super-strong car is still on. Materials such as carbon fiber, graphene and Kevlar are still not widespread in large-scale mass production due to their relatively high prices. In comparison, injection molding of EPP components is a well-known and readily available technology that allows for the fast and cost-effective manufacturing of reproducible components even with very complex shapes or with additional inserts of different materials. The production methods used at our 44 plants spread across 9 countries allow all product parameters to be precisely tailored to individual design needs. 

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