A minimalist approach to vehicle design doesn't necessarily mean Spartan. As demonstrated in the Jeep Renegade concept, designers can combine advanced styling and function with small energy and environmental footprints—from production through end-of-life recyclability.
The Renegade is a concept for a plug-in/serial hybrid with a small diesel engine. It features the use of Tegris, a lightweight thermoplastic composite containing 100% polypropylene that was developed by Milliken and Co. The composite material is used for the chassis, interior molded tub and door panels, seat frames, and in the instrument panel.
Tegris, previously named MFT for molded fiber technology, can provide the strength and stiffness of carbon-fiber reinforced materials, with just a 30% weight penalty but substantial cost advantages. Tegris has a 65% weight advantage compared to steel, 52% compared to ABS (acrylonitrile butadiene styrene), and 32% compared to aluminum, according to Milliken.
Further, Tegris costs a small fraction of the price of carbon-fiber composites and does not require the addition of resins, which produce volatile emissions, according to Scott Anderson, Senior Interior Designer for Chrysler. It is energy-efficient to produce, and because it is capable of being formed into large, complex shapes such as the interior tub, it is very cost-effective. Tegris, which returns to its 100% polypropylene state during recycle extrusion, is fully recyclable and safer to handle than composites containing glass fibers. If a component is made of several materials, the recycling process starts with chopping and then separation according to density, explained Anderson.
The Tegris seat structure goes into a molding tool with urethane roll material, and soy foam cushioning material is injected to produce a one-piece seat with a urethane skin on the exterior. Foam can be injected to form several layers of different density to provide support and comfort for the seating surface, Anderson said. Also, the urethane skin can be made in color and with graining. The process eliminates cutting of materials, stitching, adhesives, and fasteners.
A similar approach is used for the instrument panel, but in the Renegade a cross-car beam made of hydroformed aluminum is in place during the panel's molding process, Anderson explained. Molding into single components eliminates fasteners and adhesives, improving assembly quality and reducing NVH. Although the concept's exterior panels are of carbon fiber, that was chosen because it was the available fabrication method for the one-of body. Tegris also might be used in a production car.
The Renegade also is a nearly wireless concept. A power strip runs through the cross-car beam. The gauges cluster mounts to the steering column, and a rotating circular screen at the center of the steering wheel enables the driver to select drive functions, including those for four-wheel drive. A swiveling touch-screen LCD tablet replaces the conventional center stack control head.
Other devices, such as cellular, navigation, and infotainment, would be wirelessly connected to the LCD tablet, with its display serving as a slave to a chosen device.
Wireless circuitry also would be used for exterior lighting and even the individual wheel speed sensors. The sensors would be somewhat similar to but far more responsive than the sensors and in-car receiver used for a tire-pressure monitoring system. Lighting and other applications would be triggered by wireless sensors and controlled by the driver through the LCD tablet.
Eliminating wire not only improves assembly quality and reliability but also helps to simplify end-of-life recycling by eliminating wire and its plastic insulation.
The battery pack is located under the seats, so a console food heater/chiller simply plugs in. Because the Renegade is an open dune-buggy type vehicle, it has no conventional HVAC, only a Peltier-junction system for heating and cooling the seats.
The Renegade concept is intended to demonstrate an efficient sustainability ratio, Anderson said. This value, also referred to as "emergy," is the ratio of the energy to produce, transport, and assemble all systems, divided by the energy required for disassembly and disposal. In addition to low energy use in all processes, a 1-to-1 ratio would show good efficiency.