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1st September 2017, Cologne

Auto success for multiaxial Tepex

Continuous glass fibre layers designed to withstand bending and torsional stress. © LanxessLanxess, headquartered in Cologne, Germany, reports that its Tepex dynalite multiaxial thermoplastic composites are finding new applications in vehicle interiors.

One example is the backseat system of an off-road vehicle made by a leading European OEM. The centre backseat is equipped with a load-through that enables the backrest of each seat to be folded down individually. This load-through component is produced by shaping and back-injecting Tepex dynalite.

“The part marks the entry of this composite material into the lightweight design of backseat systems and is further evidence of its enormous potential in series production applications,” says Henrik Plaggenborg head of technical marketing and business development Tepex Automotive.

“The new component is more than 40 percent lighter than its steel counterpart, adds Harri Dittmar, project manager and Tepex applications specialist. “At the same time, this safety-relevant component withstands all load scenarios, because the orientation of the continuous fibre layers in the two millimeteres-thick semi-finished product is designed to bear the mechanical stress.”

Tepex is manufactured by Lanxess subsidiary Bond-Laminates, which is based in Brilon, Germany.

The lightweight component was developed by Brose Fahrzeugteile, of Coburg, Germany, with support from the Lanxess High Performance Materials business unit.

For functional reasons, the load-through is only mounted on one side, at the top of the rear seat’s backrest. Because of its position, it is exposed to both bending and torsion forces. To withstand these load scenarios, a special multiaxial design was chosen for the continuous-glass-fibre layers in the thermoplastic composite.

Multiaxial Tepex is a new development from Bond-Laminates, which makes the composite sheets significantly stronger than before by combining the Tepex fabric with tapes in a technically complex process. The semi-finished product for the load-through has a core consisting of four layers, each 0.25 millimeters thick, which have a fibre orientation of +45 and -45 degrees relative to the component’s longitudinal axis and are arranged symmetrically. They absorb the torsion forces. In contrast, the bending forces are absorbed by the two outer layers, each 0.5 millimeters thick, in which 80 percent of the continuous fibres are in the direction of force. “In case of a frontal collision, this multiaxial layer design ensures that the lightweight component withstands the impact of the accelerated load in the trunk and, in case of a rear collision, the inertia forces pressing the passenger into the seat,” explains Dittmar.

One-shot process

To manufacture the load-through, a blank of the semi-finished product is heated, placed in the injection mould, shaped and back-injected with a glass fibre reinforced thermoplastic. In addition to ribbing that lends the part high stiffness, numerous functional elements are integrally moulded on the component in the injection moulding step, such as mounts for the headrest, various mounting points and screw connections, and the surrounding groove to which the rear, textile covering of the load-through is mounted. With a conventional steel design, this functional component would have had to be welded or screwed on separately.

The mould for the load-through was optimized with the help of a draping simulation developed by Lanxess as part of its HiAnt services. Under this brand name, the company has combined its extensive range of services for supporting customers through the entire component engineering process.

Various shaping strategies were visualized and evaluated in the draping simulation. The results were incorporated in moUld design from the outset and helped to reduce the development time significantly. Lanxess derived the design of the semi-finished product blank on the basis of the specific moUld technology. The blank is pre-shaped or locally held in place inside the mould before the mould is fully closed.

“This prevents the formation of folds and the over-extension of the continuous fibres during shaping of the semi-finished product,” says Dittmar.

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