Reducing a car’s weight actually makes it more fuel efficient. In an attempt to build lighter cars, a group of scientists, at the Germany-based Fraunhofer Society, has developed an innovative technique of replacing traditional aluminium engine blocks with specially-designed plastic parts. The technology, which is compatible with mass production, could bring about a 20-percent reduction in weight, without any added costs.
In general, the powertrain system, containing the engine, accounts for a substantial portion of the vehicle’s weight. The concept of lighter cars has been around since the 1960s, when aluminium cylinder blocks were first introduced to the automotive industry. Efforts to build sturdy plastic car parts actually date back to the 1980s. Up until now, however, the manufacturing process of such components was extremely time-consuming and expensive.
This time around, the Fraunhofer Project Group for New Drive Systems (NAS) has developed an experimental engine, that consists of lighter injection-molded fiber-reinforced plastic components. By incorporating such parts into the standard aluminium engine block design, the researchers have managed to reduce its weight by an impressive 20-percent. Speaking about the project, Dr. Lars-Fredrick Berg, the head of the research facility Lightweight Powertrain Design at NAS and the study’s leader, said:
We used a fiber-reinforced composite material to build a cylinder casing for a one-cylinder research engine. The cylinder casing weighs around 20 percent less than the equivalent aluminium component, and costs the same… We have proved that it is capable of the same performance as conventionally built engines.
Using plastic parts in place of heavier aluminium segments actually reduces the vehicle’s total fuel consumption. Furthermore, it helps lower the engine noise as well as the heat radiated from its core. However, to be able to achieve such a feat, one needs to use materials that are capable of withstanding high temperatures and pressure, without incurring any damage. According to the team, the plastic material needs to be sturdy and rigid, while also being resistant to petrol, glycol, oil and water-based coolants. Its thermal expansion coefficient should not be more than that of metal, such that it can easily adhere to the aluminium parts. A lighter, yet more expensive alternative would be carbon fiber-reinforced composite. Berg said:
First we looked at the engine design and identified the areas subject to high thermal and mechanical loads. Here we use metal inserts to strengthen their wear resistance.
The scientists have built a prototype of the engine, using glass-fiber-reinforced composite. Developed by SBHPP, the material, comprising 55-percent fibers and remaining 45-percent resin, is produced from granulated thermoset plastics via an injection molding process. Once combined, the glass fiber and resin composite is injected into a special mold, where it hardens to optimum rigidity. Not only is the technology suitable for mass production, the manufacturing costs of the plastic cylinder parts are significantly lower than that of the aluminium engine blocks.
The team is currently working towards designing a lighter and more flexible multi-cylinder plastic-based engine. According to Berg, the prototype is scheduled to be unveiled at the 2015 Hannover Messe, between April 13 and 17.