JEC COMPOSITES MAGAZINE - Issue #53 - November/December 2009 - 30

FEATURE “Automotive” Composite body structure The concept of a fully load-bearing body structure was shown to be feasible with the E-LFT process. Using a clever design and fibre arrangement, even a commodity polymer such as glass-fibre-reinforced PP can be used to produce a passenger cell that meets standard requirements. Andreas Rüegg, Mechanical Engineer ETH, Esoro (1) Mark Berlin, Mechanical Engineer FH, Weber Automotive (2) Norbert Stötzner, Mechanical Engineer FH, Weber Automotive (3) Diego Jaggi, CEO, Esoro (4) Fig. 1: E-LFT base materials Left: EF tapes (continuous unidirectional fibres) – PPGF60 Middle: E-LFT part (2/3 rear seatback) Right: LFT base materials (glass & PP-granulate) – PPGF30 ong fibre-reinforced thermoplastics (LFT) are already used for components in high-volume applications, thanks to their low cost and good processing capabilities. Despite their great potential in lightweight construction – due to their low density – their mechanical properties are often lower than those of metallic materials. So far, this has prevented their use in more highly stressed structures such as automotive bodies. Combining conventional LFT processing with unidirectional continuous fibre inserts (EF) will make it possible to produce such structures. L Structural elements produced: tailgate and rear seatback The first series application is the tailgate [1] of the Smart Fortwo, a two-part locally reinforced part with a fully visible grained surface (Figure 2). The components consist of glass-fibrereinforced polypropylene (PPGF30 and PPGF60 UD). Compared to previous versions of the coupé and convertible, stiffness is 20% greater for the same weight, at 10% lower cost. The E-LFT process The E-LFT (Endless- and Long-Fibre Thermoplastic) process combines unidirectional continuous fibre tapes (EF) with the well-established LFT technology (Figure 1). LFT moulding compounds have relatively modest mechanical properties, but provide excellent design freedom and enable the economical production of large components. Unidirectional continuous fibre tapes (EF) have excellent mechanical properties and can be inserted three-dimensionally to conform to load paths and component geometry. The materials are heated and processed by compression moulding to ensure maximum fibre length in the LFT. Injection moulding trials were also performed with promising results. This single-step process yields highly structural lightweight parts, which can replace metal structures. Production volumes range from 20,000 to 300,000 parts per line and per year. Fig. 2: Tailgate of the Smart Fortwo – the first E-LFT application This modular solution for convertible and coupé versions, along with the creation of additional storage space in the tailgate system, was honoured by the 2008 JEC Award for the best new development in the field of Ground Transport & Automotive. Up to 700 parts are produced daily at Weber Fibertech, Germany . As part of an OEM study, a new generation of E-LFT rear seatbacks was created, which fully meets the greatly increased safety requirements. The divisible 40/60% backrest system jec composites magazine / No53 November - December 2009

JEC COMPOSITES MAGAZINE - Issue #53 - November/December 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #53 - November/December 2009