Home' Australian Automotive Aftermarket Magazine : Australian Automotive Aftermarket e-Zine - Sep13 Contents TECHNICAL COLUMN
First and foremost, the integrity of the body
must contribute to passenger safety by
minimising the impact on vehicle occupants in
The body must absorb as much energy as
possible and slow the actual force of the
On the other hand, the increasing regulatory
demand for emission and fuel consumption
improvement requires the body to be as light as
possible, with a shape and form that minimises
For passenger comfort, the body must
minimise noise and vibration and be torsionally
stiff enough to meet ride and handling
New regulations with respect to
sustainability require the vehicle manufacturer
to be responsible for the environmental impact
of end-of-life vehicles and meet recyclability
All of these primary design requirements
must be met at a reasonable cost and have the
ability for high volume manufacturing while
meeting aftermarket reparability benchmarks.
The body structure being referred to is
known by the industry as a ‘Body-In-White’
(BIW) where all pressing, welding and metal
finishing is complete prior to painting.
This article will review the materials,
processes and future technologies required to
meet the ever increasing requirements of the
vehicle body structure.
Steel: The primary reason for using steel in
the automotive body structure is its inherent
capability to absorb energy in a crash situation.
This, in combination with good formability,
relatively easy joining capability, familiarity and
low cost has often made steel the first choice of
designers for body-in-white (BIW) applications.
But given the need to reduce weight, steel
has been under threat for some time and, as a
result, a huge amount of research has been
undertaken by the steel industry to maintain its
pre-eminent position in the business.
One such project, conducted by a
consortium of the largest steel producers called
the Future Steel Vehicle (FSV), has found the
potential to reduce the mass of a car body by 39
percent compared to the baseline steel body
The optimised FSV body would weigh just
176.8kg putting steel on par with today’s
aluminium production designs.
This was achieved by using more than 20
new, advanced high strength steels (AHSS)
which should be commercially available to the
market in the 2015 to 2020 timeframe.
Aluminium: Up to now the growth in
aluminium in the automotive industry has been
in castings for engine, transmission, wheel and
heat exchanger applications.
The cost and difficulty to press aluminium
has been the biggest impediment to its large
scale use in sheet applications.
Despite these impediments, the use of
aluminium in the US auto industry is expected
to triple by 2015.
To meet this demand, producers are adding
production capacity but nevertheless spot
shortages are expected to occur.
Currently the industry is using aluminium
sheet for hoods, fenders, doors and tailgates but
the big weight reduction will come when
manufacturers switch to aluminium BIW.
At least one US manufacturer is expected to
produce an aluminium body-in-white in 2015.
In Europe, Audi, Mercedes Benz and Jaguar
have produced vehicles with aluminium bodies.
For example the recently launched
Mercedes SL roadster has a 255kg aluminium
BIW that reportedly cut around 140kg from the
Earlier this year Land Rover released its all
new aluminium body Range Rover onto the
The all-aluminium monocoque body has
resulted in a vehicle that is 420kg lighter than
its predecessor, due in part to a 39 percent
lighter body structure, which translates to a
saving of 180kg over an equivalent steel body.
Half of the aluminium used is made from
recycled material and 85 percent of the vehicle
Plastics: In the past the use of carbon fibre
has been confined to low volume sports
supercars such as the Lamborghini Aventador
or the McLaren P1, primarily due the cost of
the raw material and its processing.
Later this year, BMW will launch its all new
electric car designated as the i3, which will
incorporate a carbon fibre body shell mounted
on an aluminium space-frame with plastic
According to BMW, the weight saving of
250kg over an all steel body and 175kg over an
all-aluminium body will give the i3 the agility
and range advantage over other contemporary
electric vehicles such as the Nissan Leaf and
the Renault Fluence.
The woven carbon fibre mats are supplied
from a purpose built plant in Washington
Statem USA to the German Leipzig plant where
they are moulded into shape, trimmed, cleaned
and any holes cut using high pressure water
The body shell is assembled by robots and
bonded together using two-pack polyurethane
According to BMW the process is slower
than a conventional all steel body shop, but not
by much, as eliminating the press shop and
paint shop saves time in the process.
Investment is also less as there are no
conveyors; welding machines and the robots are
lighter duty as they don’t have to carry very
heavy spot welding guns.
The moulded plastic body skin panels are
painted at a sister plant.
BMW claims that crash testing of this new
body concept is as safe, if not safer, than a
conventional body in a crash.
It also claims that crash repair will also be
cheaper, as 95 percent of crashes will only
affect the exterior panels, which are easily
replaced, with just 2.5 percent affecting the
AUTOMOTIVE BODY STRUCTURES
Apart from the obvious need to meet the aesthetic demands of the consumer, the
design of a vehicle body must meet a growing number of design criteria to serve
its many functions.
50 AUTOMOTIVE AFTERMARKET MAGAZINE SEPTEMBER 2013
Readers are invited to send
technical enquiries of a
general nature to:
AAAM SEPT 2013:AM MAGAZINE SHELL 5/9/13 2:23 PM Page 50
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