Automotive Articles

Plastic helps front-end carrier carry the load

The 2007 Jeep Wrangler’s front-end carrier (FEC) represents the first use of reinforced plastic as a structural load member for a body-on-frame assembly, according to system supplier Decoma International.

The application was a finalist in the Society of Plastics Engineers’ (SPE) annual Automotive Innovation Awards, which recognize innovative plastics use in a variety of categories.

The original FEC design called for an all-steel welded system that consisted of eight components and had a mass of 15.6 lb (7.1 kg). The bonded plastic/steel assembly, which is an integral part of the
front-end body structure, features two fewer components and is about 3 lb (1.4 kg) lighter.

Long-glass-fiber-reinforced polypropylene (Celstran PP-GF 40-03 supplied by Ticona) provides structural connection between the upper and lower steel tube crossmembers. Dow Automotive’s
Betamate low-energy substrate adhesives (LESA) join the upper crossmember to the plastic carrier to distribute stresses and improve modal performance. This assembly allowed joint stiffnesses to be maintained while improving durability performance.

Decoma engineers used predictive warp analysis to ensure final product capability.

The front-end carrier is molded by Toledo Mold and Die. “In the traditional assembly of hybrid
front-end carriers, the metal reinforcement is attached to the plastic using mechanical techniques such as rivets, heat stakes, or through over-molding,” said Dave Recktenwald, Dow Automotive Plastic Bonding Market Development Manager. “When the substrates are bonded with Betamate LESA, the metal reinforcements and molded plastic parts can be optimized for reduction of part thickness, resulting in significant weight savings and improved structural performance.”

Betamate LESA, which bonds longglass filled polypropylene and e-coated steel with no pre-treatment or primers, is also used on the 2007 Dodge Nitro’s front-end carrier.

Not only do the plastic components manage all vertical loads between the upper and lower closed-section steel tubes, they also provide mounting features for other front-end components.
Functional integration examples include a molded-in element for attaching the temperature sensor, a radiator grille attachment, and headlamp mounting points. A molded rib serves as an air guide to prevent bypass of the heat exchangers.

In addition to a 15% weight savings, the plastic/steel assembly offers a 25% cost savings (about $3) vs. the traditional all-steel construction, according to the system supplier. “We can estimate
$250,000 of cost avoidance in the areas of stamping tools and body fixturing tools,” a Decoma engineer said during an SPE presentation.The technology can be used on all vehicles with similar body-on-frame construction, says Decoma.

Source : SAE International.