Faurecia’s recently introduced Urban Liftgate demonstrator is a showcase for several innovations designed to rethink the rear-end of vehicles. Among the innovations is the use of a new type of composite made of natural flax fibers instead of carbon.
Although the flax-based composite is not comparable mechanically to carbon fiber composites, said Laurent Gillard, Senior Engineering Manager, it has its own intersting properties and offers a lower-cost than carbon fiber and an environmentally friendly solution for lightweighting. The flax-fiber composite provides a weight savings of around 45% Gillard said—in the ballpark of the estimated 50% weight savings from carbon fiber.
For production, Faurecia purchases woven flax fiber (the company has two suppliers) and then uses a resin transfer moulding (RTM) process to produce the composite piece. From a resin transfer standpoint, the behavior of the flax is highly similar to carbon, Gillard said. Faurecia essentially uses the same processing—not exactly the same parameters, but the logic and the approach for tuning the process are the same.
Processing time is essentially the same as carbon, Gillard said; there is no production drawback in using flax vs. carbon.
The mechanical performance is below that of carbon fiber. It’s very difficult to give one number to compare to; there are many sorts of carbon fiber. But, again, on exterior parts, that [mechanical performance] is not really what matters. The load case is not that high, and there are no crash requirements. The intent [behind using flax] is no to replace the mechanical performance of the carbon; the use is more on the look side than the mechanical side.—Laurent Gillard
The flax fiber composite has an appearance very like carbon composite. The demonstrator’s flax-resin roof and spoiler is finished with a metal-tinted clear coat to add reflection and harmonizes with the rest of the car.
Urban Liftgate. The Urban Liftgate offers a series of car customization technologies for high-end decoration solutions.
Faurecia has integrated the third brake light invisibly into the spoiler along the rear roof line. A LED lighting module is covered with a rigid, transparent strip of plastic tinted to match the spoiler. When the light is not activated, the strip blends with the spoiler and cannot be seen. When the brake is applied, the LEDs shine through the transparent cover with a red glow. Similarly, the two brake lights above the bumper employ translucent color panels and high-end translucent metallic paint to remain dark until the car brakes. This lighting system will be offered early in 2017 for 2019 cars.
Below the bumper, Faurecia has applied a varnish containing micro-beads, producing a granulated effect like sharkskin. It helps protect the finish from micro-scratches and frequent high-pressure car washing. Below the rear window is a sprayed-on metallized paint that replaces expensive chrome while providing a shiny chrome-like appearance without the weight. Spray metallization offers a large diversity of color options unattainable with chrome. Textured painting currently is available from Faurecia, and metallized spray should begin appearing on vehicles in 2018.
The paint applied to the vehicle back can be laser-engraved with words, pictures or shapes for state-of-the-art car customization.
New kinematics enable the liftgate to slide over the roof and prevents rear deflection. When opened, the tip of the liftgate is 25cm lower than with conventional kinematic systems, making it an ideal solution for low clearance parking.
Equally, the smart sliding kinematics enables a gain of 18 cm of clearance behind the rear of the car, easing the liftgate opening in tight parallel parking. In addition, the liftgate offers two different opening levels, a full open position where the liftgate slides over the roof and a half-open position for vehicles bearing a roof storage box. The purpose of this sliding door concept is to illustrate a novel way in which kinematics can be integrated into rear door systems.
The demonstrator’s spare wheel tray is fashioned from a composite thermoplastic reinforced with glass fiber to reduce weight and allow for recycling while meeting all crash-test requirements.
The trunk floor is made of Ligneos, Faurecia’s patented real-wood material for large areas with complex shapes. It weighs 20% less than traditional wood paneling. Faurecia today offers more than 40 varieties of Ligneos wood in multiple shades with matte, lacquer and textured finishes for use in automotive interiors.
Urban Liftgate also benefits from aerodynamic bumpers: actuators and motors allow the bumper to change its shape and improve vehicle aerodynamics to reduce air turbulence, for a gain in fuel economy.