A German car manufacturer was looking for a solution to locally reinforce a battery box molded from a DLFT (direct long glass fiber thermoplastic) polypropylene (PP) compression molding compound. Crash test requirements stipulated that a 29-kilogram battery was not allowed to break through the wall of the console at an impact speed of 50.4 km/h, translating to withstanding a force of around 45 times that of gravity. This requirement was beyond the performance of the DLFT compound itself.
|PP-glass fiber fabric composite stands up to a force of 45 G.|
The solution adopted was a 320 x 230-mm, 0.5-mm thick insert consisting of a single-layer fabric containing 47 percent by volume continuous glass fiber rovings largely aligned in the same direction that was fully consolidated, impregnated and embedded in a PP matrix. The Tepex composite was supplied by Bond-Laminates, a subsidiary of Lanxess.
The semi-finished products from the company are increasingly being used to reinforce components made of fiber-reinforced thermoplastic compression molding compounds in areas subjected to high stress. The Tepex dynalite 104-RGUD600 insert reinforces the front wall of the console, which may be hit by the top of the battery in an accident.
Tepex was adopted in place of an insert based on a consolidated hybrid yarn fabric made of glass and PP fibers that could not satisfy the impact requirements at high and low temperatures. “The replacement was made possible because the console reinforced with our material passes the recently tightened crash test for the component. This is thanks to our composite’s high stiffness, strength and toughness across a wide temperature range,” explains Harri Dittmar, applications developer for Tepex.
“Consoles reinforced with our inserts meet the test conditions including for the new tests at -30 °C and +85 °C. In contrast, the previous component solution fails at these temperatures,” says Dittmar. A penetration test to DIN EN ISO 6603-2 is one example that shows how tough the composite material grade is. It is around eight to nine times more impact-resistant at room temperature than a pure DLFT compression molding compound based on polypropylene. The stiffness of the console is six times greater than a DLFT component manufactured solely from polypropylene and three times greater than the replaced design.
Dittmar expects Tepex dynalite to be used more frequently in the future in automotive engineering for various components relevant in crash scenarios for targeted local reinforcement of DLFT flow molding compounds: “Tepex boosts the performance of the cost-effective DLFT molding compounds and expands their range of uses. DLFT compression molds are also much more cost-effective than injection molds.” As well as battery consoles, other possible applications include battery holders and various vehicle undercarriage components.