Hyundai’s new Sonata to employ composite rear armrest and rear seatback frames

Like many nations, South Korea is introducing regulations to boost fuel efficiency in its vehicle fleet, requiring automakers to boost fuel economy by 20% between 2015 and 2020 to 20 km/l (47 mpg). Automakers there face a challenging few years in the lead-up to implementation of this new regulatory regime, and they prioritizing mass reduction as one means of improving vehicle miles per gallon. If vehicles do not meet these standards, Korean automakers face fines of KRW82,352/km per car they fall short, meaning if an OEM assembles 100,000 vehicles the fine will amount to KRW8.23 billion ($7.6 million).

To shred pounds from its curb weight, the latest iteration of Hyundai’s Sonata sedan has switched from steel tube frames to glass fiber-reinforced polypropylene (PP) for the rear armrest and rear seatback.

Detailing development of the armrest at the recent JEC Asia show, Yong-Sik Kong, Principal Research Engineer at Hyundai Advanced Materials’ R&D Center noted that a key performance parameter was to keep deflection within 40 mm when subjected to a vertical or lateral load of 40 kgf. The interim design was able to satisfy this design parameter while reducing the frame weight by 22.4% from 1,464 g to 1,135 g.

A subsequent plastic composite version optimized using CAE was also 20% lighter than a steel tube variant with a revised design, weighing 900 g versus the 1100 g for the steel version. The number of parts was also reduced by 50%.

In manufacturing the rear armrest, the GF-PP frame is injection molded with glass fiber mat (40%) prepositioned in the injection tool. Once molded, holes are cut, an insert molded steel component is added, and foam-in-place polyurethane is carried out to complete the finished part.