aluminium in commercial vehicles - European Aluminium Association

132 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER IX
Prototype floor section made
of bonded sheets and extruded
stiffeners
1.4. Application
of adhesives
As adhesive bonding is working
by surface forces, prerequisites
for a well functioning adhesive
joint are
a) the choice of an appropriate
adhesive for the materials to be
combined
b) the existence of a suitable
material surface
A suitable surface means, that
the surface area must be large
enough to transfer the applied
forces and that it is capable to
ensure a proper bonding. This
can be achieved through a
suitable pre-treatment. Any
residues of dirt like moisture,
oils, dust etc. must be removed
prior to application of the adhesive.
This can be done by chemical
means with the use of
detergents, degreasers or etching
agents or mechanically by
grinding. In any case the surface
must be absolutely clean before
gluing. It might be favourable to
use a primer for better wetting
of the metal surface by the
adhesive as well.
Patented by Alcan
The joint construction should be
related to the adhesion process
and its requirements for large
bonding areas. Peeling and
cleaving forces on adhesive
joints must be avoided and
bending forces should be
reduced to a minimum.
The adhesive can be applied
manually (e.g. with the use of
cartridges) or for larger areas
with automated machines. The
bonding should take place in a
dry and well ventilated and
dust-free workshop.
The work must be done in strict
compliance with the manufacturer
s rules. The production parameters
such as resin/hardener ratio,
duration and pressure component
fit up during adhesive curing, curing
temperature, etc. must be controlled
properly.
1.5. Creep and ageing
The durability of adhesive joints
depends on factors such as proper
pre-treatment, chemical composition
of the adhesive and
service conditions like stresses,
temperature, humidity and exposure
to ultraviolet radiation (polymers
are sensitive to this kind of
radiation and tend to lose their
mechanical properties).
The ageing of bonded joints can
be caused by creep under stress
(creep can be defined as timedependent
increase in the
length of visco-elastic substances
subject to a constant
tensile load).
Adhesive joints should therefore
be inspected regularly to prevent
damages and to enable
repair prior to a possible failure.