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Because of the CO2 emission issue and growing transportation costs due to high fuel prices, it is urgent that car manufacturers significantly reduce the weight of their products. Lightweight composite materials from Quadrant Plastic Composites (QPC) can help them reach their weight reduction targets.
(Published on November-December 2008 – JEC Magazine #45)
KARL-HEINZ KALMBACH, BUSINESS LINE LEADER, EXTERIOR & STRUCTURES, QUADRANT PLASTIC COMPOSITES
Reducing a car’s weight by 10% can improve its fuel efficiency by around 5-7%.
The majority of cars on the road (about 66%) are midsize models with an average weight of 1,500 kg. Reducing their weight by about 10% means saving 120-150 kg. One of the ways for OEMs to achieve this goal is to use an extended material mix in the future, including composite materials. QPC has been active in the automotive industry for many years, offering lightweight thermoplastic composites such as SymaLITE and structural advanced composites with textile reinforcements. The new European legislation on CO2 reduction is also placing growing pressure on OEMs to reduce weight. In Germany, for example, traffic creates 11.9% of the total CO2 emissions. From 2012, a new EU regulation will set the CO2 emission limit at 130 g/km. The total European motor pool will have to fulfil this demand by 2015.
The lightweight thermoplastic composite materials from QPC can help reduce vehicle weight significantly. These material include two main groups: structural composites with or without textile reinforcement, and low-weight reinforced thermoplastic composites (LWRT); see Figure 1a and 1b. Structural composites have a density in the 1.1-1.7 g/cm3 range, while the areal weight of LWRT ranges from 1,200 to 2,100 g/m2.
Most of the structural materials have a PP resin matrix, but other matrix systems are also available. The reinforcement fibres are mainly chopped or continuous glass fibres. Chopped fibre length ranges from at least 25 mm up to 100 mm, which is one of the main differences with other fibre-reinforced materials and processes. An additional fabric reinforcement can be used to achieve tailor-made material properties and significantly higher mechanical properties.
A wide range of applications
QPC’s latest innovative material developments for structural applications are mineral-filled grades for non-textile reinforced materials with improved mechanical properties (about 25% better). By using a multilayer design for fabric-reinforced materials, it is possible to eliminate additional steel reinforcements, as is already the case for front-end applications. Furthermore, heat-resistant materials using PP/PA blends, PA or PBT as resin are opening up new application fields. For extreme loads, a steel-cord-reinforced grade was developed in cooperation with Bekaert and Voestalpine Polynorm Plastics. These grades allow high-speed performance up to 80 km/h, with an excellent integrity and energy absorption level.
LWRT, the second material group, are lightweight materials used for interiors and underbodies. To save further weight in underbody applications, the automotive industry tends to replace hard materials made by injection moulding, LFT or GMT technology with these low-density materials (Fig. 2). The SymaLITE grades also exhibit excellent acoustic performance.
Both material groups have been used in different mass-produced car models for many years. If all of these applications were combined in one car, the weight-saving potential would be over 50 kg, just for the structural materials. These applications include bumper carriers, pedestrian beams, engine cradles, front-end carriers, instrument panel carriers, seating, hatchback structures, underbodies and more. The maximum weight saving is achieved by replacing metals with composites (Fig. 3).
As far as interiors are concerned, the weight-saving potential of LWRT is not as high as with structural grades. However, roughly 8 kg can be saved by using these materials in applications like instrument panel toppers, tunnel covers, door panel inserts, headliners, parcel shelves, load floors, seat back covers, trunk liners and more (Fig. 4).
Combining LWRT with structural grades would enable a weightsaving potential of more than 60 kg. It is important to understand that all materials and the corresponding applications are specified at different OEMs and fulfil all requirements. For this reason, radical innovations are not necessary, because lightweight designs can be achieved with existing systems and without excessively long pre-development phases and development times.