CompositesWorld
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FEBRUARY 2018 60 CompositesWorld FOCUS ON DESIGN Hybrid composite struts reduce vehicle weight, improve handling Pultruded carbon/glass fiber composite underbody stiffeners move into medium-volume Mercedes-AMG production vehicles. » A joint development team from Daimler AG's (Stuttgart, Germany) R&D; organization and the Mercedes-AMG perfor- mance car division began investigating ways to trim mass cost- efficiently from body-in-white (BIW) structural components. An early target (circa 2011) was pairs of all-steel strut bars on various performance-vehicle models — one pair on some vehicles; two pairs on others. Functionally, the struts increase vehicle rigidity and improve handling. Strut bars — usually inexpensive compressed steel tubes — are well established on production vehicles. Already well optimized in terms of cost and weight, these benchmarks provide limited opportunities to improve either in the incumbent steel format. But composites — particularly in the form of carbon fiber-reinforced plastic (CFRP) — offered new opportunities to lightweight the struts, yet meet demanding mechanical and thermal performance, while also keeping the economics reasonable. Issues with conventional strut bars Chassis strut bars are structural components designed to resist compression and tension in the longitudinal direction by providing outward-facing support along each bar's longest axis, thereby holding two components apart and preventing them from flexing or collapsing. Correctly designed and installed, strut bars help stiffen substructures. e practical result is a reduc- tion in chassis flex as vehicles cross uneven surfaces or take tight corners, experienced as improved vehicle "handling" for drivers. Although several higher performance metals (e.g., titanium) were considered to replace traditional steel struts, they were eliminated because they would add cost but could not meet all of the mechanical requirements for the desired lightweight design. e team then turned to CFRP. "Struts are used frequently in the substructure or front section of Multi-material, multi- vehicle chassis struts Engineers from Daimler AG's R&D; organization and Mercedes-AMG's performance car division jointly developed hybrid composite strut bars that have replaced conventional steel underbody chassis struts, resulting in a number of benefits. The application was first used on the Mercedes-Benz SLS AMG Coupé Black Series vehicles (2013) and has since been expanded to four other platforms within the Mercedes-AMG product line. Source | Daimler AG By Peggy Malnati / Contributing Writer