The Nissan composite hatchback panel (rear panel) is a good example of what is feasible in thermoplastic composite materials, even for high-volume applications.
OEM Nissan, molder Hitachi and material supplier Quadrant Plastic Composites (QPC) teamed up for this complex rear door application. In the development partnership, Nissan was responsible for design, specifications, and economics. Hitachi, as a tier 1 supplier, handled the part development, all moldings, assembly, and logistics. QPC advised on materials for the inner part and provided CAD/ CAE, tooling and processing support. The development process was based on previous experience with DaimlerChrysler’s first A-Class model, which has a similar rear-door concept. The same material combination is used for Nissan’s Stagea and Infinity models.
Including that first DaimlerChrysler A-Class series, more than 1.7 million cars have already been equipped with this type of rear door solution. The experience gained from all these applications has provided thorough knowledge on these composite hatchback panels.
Thermoplastic materials may be used for the same interior and exterior hatchback door functions achievable with steel applications, such as flip windows, integrated rear lights, and wrap-around or inlay door construction. The level of integration is even higher with thermoplastic materials, which provide good electrical performance for electronic attachment parts and allow producing aerodynamic spoiler geometries in a single step, among many other things. The Nissan Murano’s complex interior and exterior shapes can be compression molded and injection molded in a single step, while a comparable metal part would require more individual manufacturing steps.
Inner Part in Thermoplastic Composite
The inner structural part is made out of GMT/GMTex materials. These guarantee a stiff, strong, lightweight, and crashworthy solution, thanks to the glass-mat reinforcement and local weave inlay. The three-dimensional forming of these woven materials allows the absorption of high loads, with long-fiber content in all critical areas of the part at the same time. Different weave-inlay orientations can be used to achieve tailored material properties. One-step forming of complex shapes without the need for additional trimming is state of the art, thanks to the use of a flow-molding process during compression molding. GMT/GMTex processing gives competitive cycle times. Functional integration, e.g. screw domes or guiding, can be done in a single processing step. Thermoplastic materials are also used for mass-produced parts such as seats, instrument panel carriers, spare wheel wells, battery boxes, battery trays, door module carriers, underbody shields, pedestrian protection beams, bumper beams, and front end carriers.
The Nissan Composite Hatchback Panel (rear panel)
The Nissan Murano rear door system consists mainly of two large one-step-molded parts:
– an inner structural part that is compression molded in GMT/ GMTex and
– an outer part that is injection molded in Noryl GTX. The pillar and lock area feature some additional metal reinforcement. The composite hatchback panel is quite large (~1600mm in the Y direction, ~920mm in Z direction) compared to the conventional doors in this SUV market segment, and even more so compared to passenger cars. All attachment parts – hinges, wiring harnesses, lock, gas spring fixations, rubber stops, third stoplight, rear window, and license lumps – are mounted onto the body-in-white of the rear door in a series of pre-assembly steps.
Using thermoplastic materials reduces the weight of each car by about 5 kg and provides styling flexibility that is not possible with metal materials. Integrating components also reduces cost, compared to a steel solution with identical functions. The GMT/ GMTex materials used for the structural part ensure the crashworthiness of the rear door system.
(Published on August-September 2005 – JEC Magazine #19)