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.

In manufacturing the rear armrest, the GF-PP frame is injection moulded with glass fiber mat (40%) prepositioned in the injection tool.

Once moulded, holes are cut, an insert moulded steel component is added, and foam-in-place polyurethane is carried out to complete the finished part.

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%.

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).

South Korea automakers face a challenging few years in the lead-up to the implementation of this new regulatory regime. They are prioritising mass reduction as one means of improving vehicle miles per gallon.


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