Engines made from plastic
RECENT government requirements for greater fuel efficiency have led to lighter cars hitting the market, but there’s only so much that can be shaved off the body and chassis.
To find further weight reductions, a Fraunhofer project group is developing ways of building engine cylinder blocks that are partly plastic.
Lighter engines that can do the job of their heavier cousins have been around since the first aluminium engine blocks were made in the sixties. Going a step further with plastic has been on the drawing boards since the eighties, but plastic parts able to withstand engine heat and stress could only be made in small volumes and at great cost. The approach taken by the Fraunhofer project group for new drive systems (Nas) was to create an experimental engine using fibre-reinforced plastic suitable for injection moulding instead of aluminium.
“We used a fibre-reinforced composite material to build a cylinder casing for a one-cylinder research engine,” said Lars-Fredrik Berg, project leader and manager of the research area Lightweight Powertrain Design at Nas. “The cylinder casing weighs around 20% less than the equivalent aluminium component and costs the same.”
Fraunhofer said that using plastic also has the advantages of reduced fuel consumption, less noise and less engine heat. However, achieving this meant overcoming problems with heat and vibrations.
He said that in areas subject to high thermal and mechanical loads they used metal inserts to strengthen the wear resistance.
Other problems the project faced were getting the plastic to bond well with and expand like metal, redesigning engine parts to keep heat away from the plastic, and making the plastic rigid yet also capable of withstanding contact with oil, petrol, glycol and water coolants. The project settled on a glass-fibre reinforced phenolic resin of 55% fibres and 45% resin that uses granulated thermoset plastics in an injection-moulding process.
Fraunhofer said that a prototype of the engine will be shown at Hannover Messe this month. — Gizmag.com.
Fraunhofer project group’s engine is made from fibre-reinforced plastic suitable for injection moulding instead of aluminium.