BMW Carbon Fiber Lightweight Vehicles
Author: Elaine Horn, developed from speech by Dr. Joerg Pohlman for the National Petroleum Council and
follow-up interview (June/Sept 2011)
In 2007, BMW began a new strategy to redesign its vehicle concepts with “project i”. “Project i” is
an ongoing think-tank concept started by BMW’s Management Board with the mission to develop
sustainable, visionary and trend-setting concepts for mobility while fulfilling the challenges of the
consumer and staying true to BMWs core values of being fun to drive and the ultimate driving
experience. This method of thinking resulted in new processes, technologies, vehicle concepts and a
new approach to development, production and distribution for BMW. Rather than following the
traditional design and production steps of designing and drawing a vehicle before understanding
how to produce it, under the new methods, the design team went to the production team and asked
for a zero emission production process and then designed the vehicle with the end-goal in mind.
The efforts and new ideas from “project i" led to BMWs MINI E, a 2-seater EV conversion car based
on the MINI produced in late 2008. BMW’s next model released in 2011, the ActiveE, is based on
BMW’s 1 series. The Active E is still a conversion car but it is a 4-seater and has the addition of an
entirely new BMW electric drive train. BMW will launch the BMW i series (i3 and i8) in 2013. The
BMW i series vehicles are not conversions, but purpose built. The BMW i3 is an electric vehicle (EV)
and the BMW i8 a plug in hybrid electric vehicle (PHEV).
BMW i3 Concept
BMWi8 Concept
BMWs new strategy also initiated its partnership with SGL Group in 2009 to create the SGL
Automotive Carbon Fibers JV to focus on innovating vehicle lightweighting through carbon fibers.
BMW’s i series vehicles feature a new LifeDrive Architecture that includes an aluminum chassis and a
carbon fibre passenger cell, developed to eliminate the additional weight from the battery and
provide new safety measures.
LifeDrive Architecture
While there is not a significant difference in the conventional drive train and the electric drive train,
vehicle conversions add battery weight that also require additional weight to be added onto the
vehicle to meet safety requirements. BMW’s solution is to develop purpose built vehicles that are
optimized for the characteristics of PEVs (Plug in Electric Vehicles- covering both EVs and PHEVs).
BMW created a LifeDrive architecture with materials such as aluminum and carbon fiber. Although
the cost of the battery has come down significantly and will continue to do so, it is still a major cost
contributor to the PEV price. Thus, reducing any amount of weight helps because there is less
battery needed to meet range needs. In addition, the weight reductions allow the car to have better
torque and drivability, i.e. more fun to drive (the BMW way.)
1
The LifeDrive archictecture separates the passenger cell (the Life module) from the chassis (the Drive
module). Keeping the Life module separate from the Drive module and utilizing aluminum and new
carbon fiber materials provides several advantages. In a typical rear or front crash, there is no
contact with the carbon fibre Life Cell, just the aluminum Drive Module, so the vehicle is easier to
repair. The carbon fiber also protects better than traditional aluminum. The carbon fiber, which is
stiffer and stronger than metal, stays intact during a crash and absorbs the energy rather than
denting and collapsing. Carbon fibre has been used in motor sports- eg. Formula 1. In addition, as
the Life Cell is separate, it will be easier and cheaper to develop derivative vehicles based on the
same platform. Finally, the new design allows for the battery to have a lower weight distribution
under the Drive module which leads to more fun driving – the BMW way.
Using Carbon Fiber Reinforced Polymer (CFRP)
The use of Carbon Fiber Reinforced Polymer (CFRP) material within the vehicle is a significant change
to traditional vehicle designs. The carbon fiber composite industry is still a very small market in
comparison to the steel and aluminum industries (See Figure 1). Carbon Fiber has typically been
utilized in small, niche industries such as the aerospace industry, windmills, sporting goods and
motor sports race cars like Formula 1.
Figure 1: Steel, Aluminum and Carbon Fiber Market Overview
Source: SGL Automotive Group
There are several key features/properties to CFRP:
● extremely durable and extremely light (approx. half the density of aluminum),
● at least 30% lighter than aluminum and 50% lighter than steel for identical component use,
● hard, stiff and strong material approximately 2X the strength of steel
● outstanding damping and high level of energy absorption in a crash
● resistant against corrosion, acids and solvents,
● shows no fatigue over a long service life,
● allows customization of component properties due to the material’s unique anisotropy
Given these properties, BMW has found both cost savings and sustainability savings. Because CFRP
is resistant to corrosion, acids and solvents, BMW needs to use fewer coatings and less paint. In
addition, reducing the painting and coatings also reduces the water needed. Approximately 10% of
water typically used will be needed in vehicle production.
The production of CFRP fabric is really part of the textile fabric industry. In the past, all vehicles have
been made of metal. Now this new material looks and feels like a textile, and this has led to a
2
rethinking by BMWs engineers. SGL Automotive Carbon Fibers has joined the Manufacturers
Association of Textiles of Bavaria. This new use of a textile is helping to jumpstart an industry that
had lost a significant amount of business to lower cost facilities in Asia and had been in a steep
decline. Processing carbon fibre is now a new high-tech application for the textile industry.
The CFRP parts process starts with the creation of a PAN Precursor made from a crude oil base. The
Precursor is turned into carbon fibre in SGL Automotive Carbon Fiber’s Moses Lake facility (running
on hydropower). Finally the carbon fiber is manufactured into textile fabric and delivered to BMW’s
parts production plants in Landshut and Leipzig. This last process step has the most potential area
for cost benefits and is the most technologically challenging. BMW has been able to bring down
cycle times in CFRP car part manufacturing from 20 minutes down to single digit minutes, increasing
capacity and thus reduce the number of presses needed on the production line, making CFRP
economically feasible.
Why BMW and Why a Joint Venture in CFRP?
Knowing it was advancing into plug-in electric vehicles, BMW wanted to understand what
partnership strategy might provide them the most success in the new market. In the Carbon Fiber
market, there were very few active companies, companies were only operating in certain geographic
areas (Japan, US, and SGL in the EU), it was a very small market (only 39,000 metric tons in 2009),
and non-transparent pricing structures made it hard to see where along the value chain BMW could
reduce costs. Thus, BMW had to partner with a carbon fiber producer to understand the “black box”
of the cost of materials and manufacturing costs.
The JV Partnership brings several benefits to the BMW Group:
 Supply Guarantees: Given the unpredictability of the future electric vehicle market, BMW
needed to be able to securing sufficient long-term production capacity for carbon fibers and
fabrics and needed to be able to scale up production in 1-1.5 yrs to double the estimated
volume in that period and be able to double it again across suppliers.
 Technological Competitiveness: BMW needed to think ahead of the curve and maintain
confidential information within the Carbon Fiber Supplier Market – they needed a partner
versus just a supplier – to maintain their technological advantage (estimated at 3 years) in
manufacturing these new carbon fibers and fabrics
 Financial Competitiveness: BMW needed to secure full cost transparency along the entire
(high cost) CFRP value chain and be able influence reduction in production costs and to
continue to find ways to further reduce production costs.
BMW’s objectives for CFRP
BMWs goal for CFRP is to meet production cost volumes of aluminum in a short period of time ~3-5
years. This would allow CFRP to be competitive at aluminum costs but 30% lighter and thus be able
to be used in conventional ICE vehicles as well. The weight of the i3 is 1250kg including the battery,
saving roughly 300kg through the use of new materials. This is actually lighter than many ICE
vehicles in its vehicle class. The i Series vehicles will be small volumes initially, but the supply chain
is geared up to double this volume in 12-18 months and then double it again. Even this initial small
volume of vehicles will use up to 10% of the entire carbon fiber market. BMW is already discussing
the use of carbon fiber on its other platforms to advance lightweighting across its vehicles, not just
to offset battery weight in its plug-in electric vehicles.
The use of CFRP is key in advancing vehicle manufacturing. Historically, vehicles have increased in
weight due to new features. For instance, the VW Golf has gone from 850kg in the 80’s to 1450kg
3
today due to the addition of safety, electronics and comfort features. We can’t take those
enhancements away from consumers, so all car manufacturers need to find ways to reduce weight
to meet emission standards, including lightweighting. Manufacturers have already taken so many
innovative steps in other areas of the vehicle; reduction of weight is one area where it can be taken
further. However, weight reduction will only “win” as a solution if the features are legally (i.e.
safety) and socially (i.e. design and appearance) accepted.
4