megatrends

As vehicles age, the heat affected zone around
spot welds can develop micro cracking that
leads to increased flexing of the body. This can
lead to squeaks and rattles from trim
components, especially where tolerances have
been tightened to increase the feeling of
quality. The current trend is strongly towards
an increasingly premium experience, so this is
a developing problem reflected in a growing
number of costly squeak and rattle warranty
claims.
We’ve worked with one vehicle manufacturer
who was so concerned by this issue that it
was stopping them offering the longer
warranties that increasing competition in their
sector demanded. Traditional work-around
solutions, such as additional spot welding or
TIG welding of the body-in-white
supplemented by new reinforcing components,
had already been rejected due to the
increased cost and manufacturing complexity.
The project with 3M was so successful that a
number of barrier components, or compliant
foams, used at critical trim interfaces to
reduce squeak and rattle were also eliminated,
creating further savings in materials and
processes.
Can you comment on any potential
safety benefits?
Safety is another reason to adopt adhesive
joining, particularly as a supplement to
conventional techniques. Vehicles with fatigued
welds are clearly not as safe as new vehicles,
but there are further layers of complexity to
the safety case. Structural engineers now have
to manage more energy, more quickly in
Q1 2013
smaller spaces, so consistency is vital. Point
fixing such as spot-welding creates localised
stress points, but adhesive bonding spreads
the loads, not only making the join stronger
but also allowing more of the material to
contribute to energy absorption. Some new,
lightweight structures would not be possible
without adhesives to improve crash
worthiness. And unlike welds, an adhesive
bond maintains the majority of its strength
throughout the vehicle’s life.
Do adhesives offer any advantages in
terms of weight reduction compared to
welding?
Spot welds are by definition points of high
stress, so the main light-weighting advantage is
that by spreading the stresses across a wider
area, you enable the use of thinner gauge
materials. The increased stiffness, coupled with
the superior durability of the join, also allows
some reinforcing components to be
eliminated.
The elimination of the need to weld all the
components also enables the use of
materials that can be difficult and expensive
or impossible to weld, such as aluminium and
carbon fibre. We are seeing growing use of
hybrid structures, where disparate materials
such as steel and aluminium or aluminium
and carbon must be joined. You can’t weld
these combinations, so you either have to
use physical fastenings which are expensive
to apply and create localised stresses, or you
bond them. Even lower cost cars now use a
considerable multitude of steel
specifications, many of which are difficult to
Megatrends
weld or difficult to weld to steels with
significantly different specifications.
Adhesives are largely materials independent
- particularly with the new generations that
3M is developing specifically to reduce
substrate sensitivity - so are an important
enabling technology for these more complex
light-weight, hybrid structures.
How will the use of adhesives in car
manufacturing evolve in the next
decade?
Applications are growing in every region as
vehicle manufacturers come under increasing
pressure to reduce fuel consumption and
CO2 emissions. The 2020 requirements can
only accelerate this trend, driving
sophisticated materials into higher volume
segments.
3M is focussing its R&D on techniques that
allow this to be accomplished alongside
improvements in process robustness and
efficiency that often more than mitigate the
increased cost of materials. I’m also going to
predict that it won’t just be materials that
change, but that we will also start to see new
construction architectures in volume
production. With so many vehicles now reliant
on structural adhesives, body-in-white
engineers are developing tremendous
confidence in the technique. We are already
seeing some concepts using adhesives to
open-up possibilities for radical new
architectures. I’d say we’ll see some of these
ideas entering production possibly in
significant volumes, driven by the reduction in
weight that can be achieved.
We are finding that most vehicle
manufacturers start by introducing
adhesives as a supplement to spot welds or
rivets as an incremental change, to solve
specific challenges
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Automotive World Megatrends magazine | www.automotiveworld.com
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