A lightweight composite material shaped by a unique assembly technique forms a grille opening reinforcement (GOR) designed specifically for the high-performance 2016 Ford Shelby GT350 Mustang. The two-piece GOR is an industry first, and the automaker is in the process of applying for a patent, according to Peter Thai, Performance Body Exterior Engineer at Ford Motor Co.
Developing a GOR that would fit in a packaging space smaller than the 2015 Mustang was no easy task, noted Gari Schalte, Magna Exteriors’ Product Line Engineering Manager-Front End Modules.
“We ran over 50 CAE iterations of the GOR for both geometry changes as well as material changes before the carbon-filled material was evaluated,” said Schalte, noting that an additional five iterations were performed to optimize the short carbon-filled PA66.
BASF’s Ultramid polyamide thermoplastic resin with 20% short carbon fiber composition marks its automotive application debut on the high-performance GT350 Mustang, said Brian Shaner, Market Segment Manager for Automotive Body-in-White, Chassis & Exterior Performance Materials at BASF Corp.
The 2016 GT350 Mustang GOR weighs 8.1 lb (3.7 kg), a drop of 2.5 lb (1.1 kg) from the metal stamping over-molded plastic predecessor. Ford engineers opted to bypass the beauty cover, saving an additional 1.9 lb (0.86 kg) versus the former metal-plastic hybrid design.
Magna’s patented Resistive Implant Welding (RIW) joining process was used to produce a closed section structure from two injection-molded plastic parts.
Explained Schalte, “Injection molding allowed for the efficient use of the space available after the hood, headlamps, and fascia styling surfaces were lowered by 10 mm (0.4 in).” That reduced packaging space would not have permitted the metal-plastic hybrid design to fit, due to the stamped steel’s upstanding flange and draw feasibility constraints.
The carbon-fiber composite GOR locates and supports the hood latch, and it supports the crash sensors, upper radiator attachments, headlamps, and the front fascia.
“We knew from our experience developing the 2015 Mustang GOR that a 10-mm smaller section over-molded plastic steel design would not be stiff enough to meet the NVH requirements and that a box section [would be] required,” explained Schalte.
The box section has 10 ribs per side on the lower half and 14 ribs per side on the upper half to stiffen the structure for NVH performance and support the bumper fascia. “There are an additional 14 ribs per side and 38 ribs for NVH performance and positioning the fascia for safety requirements,” said Schalte, noting the carbon composite component improved the modal frequency by 2 Hz.
Magna’s RIW technology produces the closed section without a resin-rich area at the joint.
The tooling investment associated with a closed-section design was reduced by 75% in comparison to the 2015 Mustang’s five stamped steel components.
“A great deal of work was required by Magna, Ford, and BASF to validate the design of a closed-section thermoplastic GOR, and additional development work was required for the welding process to allow for the welding of a conductive carbon-filled resin.”
The two-piece GOR on the 2016 Ford Shelby GT350 Mustang represents an overall 41% weight savings when compared to the 2015 Mustang’s metal-plastic hybrid GOR with beauty cover.