En­gines made from plas­tic

The Witness - Wheels - - MOTORING - DAVID SZODNY

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.

PHOTO: SUP­PLIED

Fraun­hofer project group’s en­gine is made from fi­bre-re­in­forced plas­tic suit­able for in­jec­tion mould­ing in­stead of alu­minium.

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