Note: Descriptions are shown in the official language in which they were submitted.
CA 02384078 2002-03-06
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Method for producing a sandwich panel and for producing
a body component
The invention relates to a method for producing a
sandwich panel and for producing a body component.
The invention also relates to a sandwich panel and to a
body component produced using a corresponding method.
Sandwich panels are known from the prior art, primarily
as honeycomb sandwich panels, the honeycomb-like
intermediate layer of which comprises a hard aluminum
alloy. This layer is made "endless" in a discontinuous
method by adhesive bonding by the individual
structures. Finally, covering layers are laminated onto
both sides of the honeycomb structure. The honeycomb
sandwich panels formed in this way cannot be deformed °
in three dimensions, since the walls of the honeycomb
cells are joined to one another. The procedure is
discontinuous and therefore relatively uneconomical.
In another method for producing a sandwich panel which
is known from the prior art, long PET tubes are stuck
together to form a bundle. The PET tube bundle obtained
in this way is then cut into disks perpendicular to the
longitudinal extent of the PET tubes. Finally, covering
layers are laminated onto both sides of each individual
disk. This method too can only be carried out
discontinuously.
° The invention is based on the object of providing° a
method which allows sandwich panels and body components
to be produced economically with little difficulty.
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Furthermore, it is intended to provide a structurally
simple and lightweight sandwich panel and body
component.
This object is achieved by a method for producing a
sandwich panel having the features of patent claim 1.
Advantageous and preferred refinements of the method
according to the invention form the subject matter of
claims 2 to 4.
A sandwich panel according to the invention forms the
subject matter of patent claim 5. Advantageous and
preferred embodiments of the sandwich panel according
to the invention form the subject matter of claims 6
to 10.
The particular advantage of the method according to the
invention compared to the methods for production of a
sandwich panel which are known from the prior art
consists in the fact that the method can be carried out
continuously, despite using an intermediate layer made
from soft, flexible aluminum material.
A sandwich panel according to the invention has a high
strength and is extremely lightweight. Moreover, it can
be designed so that it can be deformed in three
dimensions by using a suitable arrangement of the
recesses.
Sandwich panels which have been produced in accordance
with the invention can preferably be used in automotive
engineering (roof linings, rear parcel shelves, etc)
and in display technology.
The cup-like recesses can be formed by pressing or by
deep-drawing.
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To allow the cup-like recesses to be formed without
damage to the material, the material of the flexible
metal foil preferably has a modulus of elasticity of at
least 70 x 103 N/mm2.
The flexible metal foil expediently consists of A1 or
an A1 alloy or. of Cu or a Cu alloy, which is
expediently from 10 um to 200 Vim, preferably 20 ~.m to
100 ~.m, thick.
The cup-like recesses are formed substantially in the
shape of an ellipsoid, a sphere, a cylinder, a
truncated cone or a truncated pyramid.
The covering layers may consist of metal, for example
of A1 or an Al alloy or of Cu or a Cu alloy, which is
preferably from 0.5 mm to 2.0 mm thick.
However, the covering layers may also consist of
plastic, e.g. of PET or PP or PS or ABS.
It-is also possible to use a Resopal plate as the
covering layer. A Resopal plate of this type is from
0.4 mm to 2.0 mm, preferably 1.3 mm, thick.
The covering layers are preferably adhesively bonded to
the flexible metal foil.
The covering layers may not only be planar but may also
be curved, since the intermediate layer can adapt to
its shape. Moreover, it may be structured, for example
it may have ribs. -
Finally, it is also possible for a sandwich panel to be
formed in multilayer form. For this purpose, a further
intermediate layer comprising flexible metal foil with
cup-like recesses is applied to one of the covering
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layers, and a further covering layer is secured to the
intermediate layer.
A method for producing a body component which achieves
the object of the invention forms the subject matter of
patent claim 11. By contrast to the method according to
patent claim 1, in this method the other covering layer
is formed directly by the metal body sheet.
The laminated structure which is bonded on ensures that
the body component has a high strength combined with a
low weight. In particular the torsional rigidity is
very high. Moreover, the body component according to
the invention has good acoustic properties and
excellent resistance to corrosion.
The adhesive used is preferably an encapsulated,
heat-activatable adhesive system which is activated at
a temperature of over 165°C and then fully reacts. The
laminated structure and the metal body sheet are joined
by the application of pressure and the simultaneous
supply of heat. The body component is then able to
withstand temperatures of over 200°C.
Before the joining operation, encapsulated foam systems
or foam systems provided with microcapsules may be
introduced between laminated structure and metal body
0
sheet, which foam systems are activated during the
joining. This results in good heat and sound
insulation.
fThe covering layer is preferably an aluminum sheet.
The method according to the invention can be used to
produce, for example, car roofs, hoods, trunk lids,
doors or other three-dimensionally deformed components
as the body components.
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Exemplary embodiments of the invention are explained in
more detail below with reference to drawings, in which:
Fig. 1 shows a plan view of an intermediate layer of a
first embodiment of a sandwich panel,
Fig. 2 shows a first variant of a cup-like recess,
Fig. 3 shows a second variant of a cup-like recess,
Fig. 4 diagra mmatically depicts the procedure involved
in a
method
for
producing
a sandwich
panel,
Fig. 5 shows an exploded view of a second embodiment
of the sandwich panel, as seen from the side,
Fig. 6 shows an exploded view of the sandwich panel
shown in Fig. 5, as seen from above,
Fig. 7 shows a double-layer intermediate layer,
Fig. 8 shows a side view of a third embodiment of a
sandwi ch panel with a double-layer intermediate
layer,
Fig. 9 shows a side view of a fourth embodiment of a
sandwi ch panel with a double-layer intermediate
layer,
Fig. 10 shows a laminated structure for producing a car
roof,
Fig. 11 shows a partial cross section through a car
roof,
Fig. 12 shows the detail XII from Fig. 11.
The intermediate layer 1 shown in Fig. 1 comprises a
flexible metal foil, into which a multiplicity of
recesses 2 have been stamped with a uniform
distribution in one direction. This can be achieved,
for example, by pressing or by deep-drawing.
The flexible metal foil of the intermediate layer 1-may
consist, for example, of Al, an A1 alloy or of Cu or a
Cu alloy, or other metals which can be drawn or
stamped. It is customary to employ metal foils which
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are from 10 ~.m to 200 um thick. In most application
examples, however, the flexible metal foil is from
20 um to 100 um thick.
The material used for the flexible metal foil of the
intermediate layer 1 preferably has a modulus of
elasticity of at least two 2 x 103 N/mmz in the case of
plastics and 70 x 103 N/mmz in the case of metals
(e. g. aluminum).
The cup-like recesses 2 may be in various forms. Two
particularly expedient shapes for the cup-like recesses
2 are shown in Figures 2 and 3.
The recess 2 shown in Fig. 2 is in the shape of half an
ellipsoid, while the recess 2 shown in Fig. 3 is in the
shape of half an ellipsoid which has been cut off in a
straight line at its free end 8.
The cup-like recesses 2 may also be formed in the shape
of spheres, cylinders, truncated cones or truncated
pyramids. The diameter of the cup-like recesses
preferably approximately corresponds to the thickness
of the flexible metal foil which has been deformed into
the intermediate layer.
After the cup-like recesses 2 have been formed in the
flexible metal foil in order to form the intermediate
layer 1, a covering layer 3 or 4 is applied to both
sides of the intermediate layer 1. In the process, at
each recess 2, firstly the opening 7 of the recess 2 is
closed by one covering layer 3, and only then is the
other covering layer 4 joined to the free end 8 of the
corresponding recess 2.
This is important since closing the opening 7 of the
recess 2 by means of the covering layer 3 leads to an
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air cushion being formed in the recess 2, which
prevents the recess 2, which consists of flexible
material, being compressed when the other covering
layer 4 is applied.
The latter method steps are diagrammatically
illustrated in Fig. 4. The arrows in Fig. 4 indicate
the direction of movement of the individual components.
The intermediate layer 1 is conveyed continuously in
one plane. A covering layer 3, which is coated with an
adhesive 9, for example a polyurethane adhesive, on the
side which faces the intermediate layer 1 is fed
continuously to that side of the intermediate layer 1
which is provided with the openings 7 of the recesses 2
and is adhesively bonded thereto, with the result that
the openings 7 are closed off by the covering layer 3.
The covering layer 4, which is likewise coated with an
adhesive 9, for example a polyurethane adhesive, on the
side which faces the intermediate layer 1 is fed to the
intermediate layer 1 - after the covering layer 3, as
seen in the direction of movement of the intermediate
layer 1 - and is adhesively bonded to the free ends 8
of the recesses 2. At this time, the openings 7 of the
recesses 2 have already been closed off by the covering
layer 3. Then, the sandwich structure formed in this
way is cut into sandwich panels of the desired size.
It is also possible first of all to apply only the
covering layer 3 to the intermediate layer 1 on the
side of the openings 7, and for this component to be
temporarily stored as a laminated structure, which is
described in more detail below with reference to
Fig. 10. The other covering layer 4 can be applied at a
later time. This allows the optional application of a
very wide range of covering layers 4.
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The covering layers 3, 4 may consist of metal, e.g. of
A1 or an A1 alloy or of Cu or a Cu alloy. Depending on
the particular application, the thickness of the
covering layers 3, 4 is normally from 0.5 mm to 2.0 mm.
However, it is also possible to use thicker or thinner
covering layers 3, 4.
The covering layers 3, 4 may also consist of plastics,
for example of PET or PP or PS or ABS or may be
designed as Resopal plates. In this case, it is
preferable to use Resopal plates with a thickness of
from 0.4 mm to 2.0 mm.
In the second embodiment of the sandwich panel, which
is shown in Fig . 5 and 6 , the covering layers 3 , 4 are
not coated with an adhesive. A double-sided adhesive
sheet 5 is in each case arranged between the covering
layers 3, 4 and the intermediate layer 1. The adhesive
sheet 5 is activated by thermal means.
It is also possible for an encapsulated adhesive system
to be used as the adhesive. An encapsulated adhesive
system is a two-stage adhesive. A first component is
activated at, for example, 70-80°C. The other component
is activated during the deformation to form the
component, at a temperature of, for example, 160-180°C.
This results in a transition from thermoplastic to
thermoset.
Fig. 7 shows a two-layer intermediate layer 1 having a
plurality of upwardly extending recesses 2' and a
plurality of downwardly extending recesses 2, which are
in each case formed in a flexible metal foil. A row of
recesses 2 alternates with an adjoining row comprising
recesses 2'. The two metal foils are adhesively bonded
to one another, so that one metal foil forms the
covering layer which closes off the recesses 2 or 2' of
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the other metal foil. However, it is also possible for
the recesses 2, 2' of each metal foil to be closed off
by a covering layer and for these covering layers to be
joined to one another.
The two-layer intermediate layer 1 shown in Fig. 7 is
used in the second embodiment of the sandwich panel,
which is shown in Fig. 8. In each case one double-sided
adhesive sheet 5 or 5' is arranged between the free
ends of the recesses 2, 2' and the associated covering
layers 3 and 4. The recesses 2, 2' are in each case in
the shape of half an elongate ellipsoid.
The fact that there are fewer upwardly extending
recesses 2' than downwardly extending recesses 2 means
that the bending resistance of the sandwich panel in
one direction is greater than in the other direction,
so that the sandwich panel can be bent in order to
adapt its shape according to installation conditions.
The third embodiment shown in Fig. 9 differs from the
second embodiment with regard to the shape of the
recesses 2, 2' which in this case are formed in the
shape of a compressed ellipsoid.
Fig. 10 shows a laminated structure 10 for the
production of the car roof 22 which is shown in Fig. 11
and comprises an aluminum plate 10, an aluminum foil
16, which is provided with cup-like recesses 18, and a
deformed metal body sheet 24, which are adhesively
bonded to one another.
The laminated structure 10 comprises the aluminum
plate 12, to the upper surface of which a double-sided
adhesive sheet 14 has been stuck. The aluminum foil 16,
into which a multiplicity of cup-like cylindrical
recesses 18 has been stamped in one direction, is
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adhesively bonded to the opposite side of the adhesive
sheet 14 from the aluminum plate 12. The adhesive
sheet 14 is activated by thermal means. The adhesive
sheet 14 causes the openings 28 of the recesses 18 in
the aluminum foil 16 to be closed off in an airtight
manner. The end faces 26 of the recesses 18 are planar
and run parallel, at one height, to the aluminum
plate 12.
An encapsulated adhesive system 20, the first component
of which has been activated at 70-80°C, is applied to
the end faces 26 of each of the recesses 18. The other
component has an activation temperature of 160-180°C.
The laminated structure 10 can be temporarily stored in
this state.
To produce the car roof 22 shown in Fig. 11, the
laminated structure 10 is laid, in a press tool, onto
the inner side of a metal body sheet 24 which has
already been deformed, in such a way that the end
faces 26 bear against the metal body sheet 24, the
encapsulated adhesive system 20 being arranged between
the metal body sheet 24 and the end faces 26.
Then, the laminated structure 10 and the metal body
sheet 24 are joined under pressure, with heat being
supplied at the same time, the temperature of this heat
being above the activation temperature of the second
component of the encapsulated adhesive system 20. This
results in a transition of the adhesive system 20 from
the thermoplastic to the thermoset, with the result
that a thermally stable bond is formed.
The metal body sheets 24 used are preferably steel
sheets or aluminum sheets with a thickness of less
than 0.6 mm. The thickness of the aluminum plate 12 is
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preferably from 100 to 200 ~.. The recesses 18
preferably have an external diameter of from 5 to 8 mm,
a height of from 2 to 5 mm and are distributed
uniformly at intervals of from 2 to 5 mm. As an
alternative to the adhesive sheet 14, it is also
possible to use a different thermoplastic or
encapsulated adhesive.
Before the joining operation, encapsulated foam systems
or foam systems provided with microcapsules may be
introduced between laminated structure and metal body
sheet, and these foam systems are activated during the
joining. This results in good heat and sound
insulation.
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