Efforts to produce lighter vehicles necessarily include engine parts, such as the cylinder casing, which could shed up to 20 percent of its weight if it were made of fiber-reinforced plastic rather than aluminum – without added costs. Such injection-molded parts are even suitable for mass production.
Until now, carmakers have relied on aluminum to reduce the weight of engine components such as the cylinder block. In the future, car manufacturers will be able to achieve further weight savings by designing cylinder blocks in which certain parts are made of fiber-reinforced plastics. An experimental engine developed by the Fraunhofer project group for new drive systems (NAS), which forms part of the Fraunhofer Institute for Chemical Technology ICT, in collaboration with SBHPP, the high-performance plastics business unit of Sumitomo Bakelite Co. Ltd., Japan, demonstrates this principle. “We used a fiber-reinforced composite material to build a cylinder casing for a one-cylinder research engine,” reports Dr. Lars-Fredrik Berg, who is the project leader and manager of the research area Lightweight Powertrain Design at the Fraunhofer Project Group for new drive systems. “The cylinder casing weighs around 20 percent less than the equivalent aluminum component, and costs the same.” It seems an obvious solution, but getting there involved numerous technical challenges, because the materials used have to be able to withstand extreme temperatures, high pressure and vibrations without suffering damage.
The EPA says that for every 100 pounds taken out of the vehicle, the fuel economy is increased by 1-2 percent. A small car with a 1.6-liter engine
* reducing weight by five percent led to an increase in fuel economy of 2.1 percent on the EPA combined rating.
* reducing weight by 10 percent gave a 4.1 percent mileage boost
* reducing weight by 20 percent improved fuel economy by 8.4 percent.
Berg’s team uses a glass-fiber-reinforced phenolic composite developed by SBHPP, which fulfills all of these requirements and comprises 55 percent fibers and 45 percent resin. A lighter-weight but more expensive alternative is to use a carbon-fiber-reinforced composite – the choice depends on whether the carmaker wishes to optimize the engine in terms of costs or in terms of weight.
The researchers produce these components from granulated thermoset plastics using an injection molding process. The melted composite material, in which the glass fibers are already mixed with the resin, hardens in the mold into which it was injected. The scientists analyzed the process using computer simulations to determine the best method of injecting the material in order to optimize the performance of the finished product. The process is compatible with mass production scenarios and the manufacturing costs are significantly lower than those for aluminum engine parts, not least because it eliminates numerous finishing operations.
SOURCE – Fraunhofer-Gesellschaft, EPA