Sticking
Points
As automotive manufacturers continue
using mixed materials in their designs,
the use of structural adhesives
will rise, as they can further
enhance performance,
lightweighting and aesthetics
A utomotive companies are under
pressure to meet stringent
emissions targets and the
contribution of design engineers
will be crucial in achieving this. Factors
such as improving engine performance
and creating a sleeker, more
aerodynamic, chassis are
usually cited as major
factors in the drive
towards improved
fuel effi ciency, but
another critical – and
ongoing – issue is
lightweighting.
Lightweighting
downsides of combining
mixed materials – such as
preventing galvanic corrosion
underpins nearly
everything that
automotive companies are
trying to achieve. Stripping
weight helps improve power-toweight
structural adhesives
also overcomes some
of the potential
between dissimilar
ratio and allows extra features,
metals”
such as enhanced cabin protection, or
more extensive control systems, to be
introduced without affecting fuel effi ciency.
“Design engineers can select from a
wide range of materials, encompassing
advanced metals, engineering plastics
and composites,” says Antonio Pagliuca,
senior technical specialist adhesives for
3M’s Automotive and Aerospace Division.
“The trick is to select exactly the right
material for each application.”
One way to do this, Pagliuca continues,
is to create hybrid structures, where
components made from different materials
are combined into a single
product: for example,
a front-end module,
which incorporates
components
made from
several different
materials.
While this
approach
maximises
the inherent
advantage of each
material, there is still
a challenge to overcome:
how to fi x them together,
“Using
without affecting structural integrity or
the characteristics of each material.
Historically, this has been done with rivets
and fasteners, but is increasingly being
achieved using structural adhesives.
“According to a study in 2017 from the
Center for Automotive Research (CAR) in
the USA, the use of mild steel for body in
white will plummet from 55% today to just
5% in 2040, as it is replaced by stronger,
lower-density materials, such as aluminium
and polymer composites,” says Pagliuca.
“Such mixed material designs are
increasingly held together with adhesives;
research from CAR reveals that some
vehicle models use more than 10 times
more adhesive than they did in 2001,
due largely to the use of mixed materials.
According to CAR, adhesives will become
the dominant form of joining by 2030.”
Pagliuca also claims that the use
of adhesive-bonded mixed materials
can make a double contribution to
lightweighting. Modern advanced
materials, such as composites, have lower
densities than those they are replacing (for
example, mild steel), while the preferred
method of joining them (adhesive bonding)
removes the need for bolts and rivets –
further cutting body weight.
“Using structural adhesives also
overcomes some of the potential
downsides of combining mixed materials
– such as preventing galvanic corrosion
between dissimilar metals,” he adds.
“At the same time, the cleaner look of
bonded joints (compared with mechanical
fasteners) creates better-looking, more
effi cient product builds, without the need
for extra fi nishing work, so streamlining
production.”
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