Liftages moving to polyolefins?

The roof is the premium location to reduce the weight of a vehicle since the center of gravity is lowered and the vehicle’s stability is improved.  The rear of the vehicle is not typically a major focus area for weight reduction.  A variety of factors, however, are promoting the increased penetration of non-steel materials into liftgate modules.  Some of these factors include:

  • Optimization of mass distribution and not just simply focusing on total mass reduction
  • Part integration especially the spoiler
  • Aggressive designs are easier to accomplish with injection molding rather than stamping
  • Vehicle facelifts are easier and variations can be produced with common inner panel deign content

The European OEMs have been the pioneers in the liftgate and hatchback conversion to composites.  This innovation was shown several years ago with the hatchback on the Renault Modus.Modus Mod

Plastic Omnium is one of the most active liftgate suppliers.  One of the hottest selling SUVs in Europe and North America is the Range Rover Evoque.  The Composite liftgate is supplied by Plastic Omnium and is made from a SMC inner and TPO outer shell.  The Peugeot 508 SW has a similar construction and saved 6 kg compared with an all-metal construction.

Plastic Omnium and Brose have developed a concept based on an all-plastic structure.  The benefits are greater integration potential and design flexibility while reducing weight compared with steel tailgates.  The tailgate structure is made from composite materials and ensures high stiffness and low thermal expansion for a uniform fit.  The outer skin, as well as the spoiler, of thermoplastic offers high design flexibility and ease of producing multiple variants.  The low weight of the structure allows the use of an innovative drive concept for opening and closing the gate.  A single spindle drive, which is located horizontally and hidden in the spoiler space, moves the tailgate.  This offers lower weight and significant acoustic advantages.

The use of composites in liftgates is not new in Japan.  For years Hitachi and Daikyo- Nishikawa have been supplying Nissan and Mazda, respectively, with such constructions.  About 2 years ago Toyota decided to enter this market and produce liftgates initially in-house as it is a customary practice at Toyota.  This signals a seal of approval for composites liftgates in Japan and a positive sign for the future expanded use of long glass fiber reinforced PP, SMA and perhaps carbon fiber composites.

In North America, the Lincoln MKT crossover was the first vehicle to use a non-steel composition for a liftgate.  Since 2010, the liftgate module was produced with a magnesium inner panel and an aluminum outer panel since 2010.  The magnesium-aluminum liftgate weighs 87.5 pounds versus 109.5 pounds for a standard steel construction.

Magna has started production of a thermoplastic composite liftgate in North America for the Nissan Rogue.  Increasingly, integration is becoming a selling point in a liftgate module.  Many parts can be integrated into a liftgate module.  Once the issue of wiper abrasion has been cost-effectively addressed, the liftgate glass could move to PC and the entire part could be multi-injected in one tool.