Note: Descriptions are shown in the official language in which they were submitted.
CA 02151786 2004-O1-14
-1-
Formable Com~~asite Panel
The present invention relates to a formable composite panel having a plurality
of layers with
at least one outer layer of an aluminium alloy and a core layer out of
plastic, and relates also
to the manufacture of and use of the composite panels.
Known from EP 0 019 835 are formable metal-plastic-metal structural laminates
and
processes for manufacturing such laminates. The metal-plastic-metal structural
laminates may
e.g. concern such having a core of polymeric resin, clad on both sides with a
metal skin
which has a thickness e.g. of 0.05 to 0.5 mm. The choice of metal-plastic-
metal laminate
makes it possible to achieve good stretch formability without delamination. If
aluminium or
aluminium alloys are selected for the metal skin, then the thickness of that
metal skin may
amount to 150 to 300 um and the thickness of the intermediate polymeric resin
between 450
and 900 lun . This results in a laminate of maximum thickness of 750 to
15001un . The
described structural laminates exhibit relatively small sheet thicknesses and
a thick layer of
plastic. This is intended to provide laminates having good sound insulation
properties.
Described in EP 0 184 549 is a thin formable composite panel having a
plurality of layers,
which is made up of at least one outer layer of an aluminium alloy with a flat
stress-strain
curve and a thermoplastic core layer of plastic. Described are outer layers of
0.05 to 1 mm
thickness and core layers of 0.3 to 3 mm. The outer layers are e.g. of iron-
bearing aluminium
alloys. These composite panels refer to particular alloys and exhibit an
exceptionally thick
core layer.
The above mentioned composite panels are suitable for many purposes, but not
e.g. for the
production of equipment and automobiles. In these Helds, there is a greater
demand for
composite panels with high structural strength accompanied by sound and
vibration
absorbing characteristics. Such composite panels are required e.g. for the
housings of
machines and equipment and in particular in the bodywork of road bound
vehicles such as
lorries and private cars. Decisive from the practical standpoint are good
formability by
commonly known methods such as e.g, deep drawing, stretch drawing, or bending,
and the
easy use of conventional joining methods such as e.g. flanging, spot welding,
clinching etc.
Sandwich-type laminates featuring thin-gauge sheets of two steel sheets and an
intermediate
viscoelastic layer have become known e.g. for the production of vehicle bodies
and engines,
housings and the like. The knowledge available up to now points to steel as
being en
excellent material for the outer layers of such thin-sheet sandwich panels, as
a very good
sound dampening effect can be achieved with steel combined with a viscoelastic
intermediate
Case 2032
CA 02151786 2004-O1-14
-2-
layer. The degree of sound dampening achieved with such thin-sheet sandwich
panels of steel
combined with an intermediate layer is substantially greater than that using
steel alone and
very substantially greater than with aluminium. Because of its low density,
aluminium would
be an excellent material for the outer layers of composite panels as this
would enable a
considerable reduction in weight to be achieved.
The object of the present invention is to provide a composite panel which has
optimum sound
dampening properties, can be joined using the usual joining technologies such
as e.g. spot
welding, clinching or flanging, is easily deformed and can be worked into
almost any shape
required e.g. by deep-drawing, stretch-drawing or other forming methods, and
which makes
use of the advantages of aluminium such as corrosion resistance, low density
etc.
That object is achieved by way of the invention in that the core layer is 20
to 150 um thick
and each outer layer of aluminium alloy is 400 to 1600 um thick and each layer
of aluminium
alloy is of a formable aluminium alloy of the type AA lxxx (pure Al), AA 3xxx
(AIMn), AA
Sxxx (AIMg), AA 6xxx (AIMgSi), AA 7xxx (AIZnMg) or AIFeSi.
Highly formable aluminium alloys are useful for the outer layers. The x in the
alloy
designations may be a number from 0 to 9 and can be taken from the register of
aluminium
alloys.
Preferred are outer layers of an age-hardenable aluminium alloy of the AIMgSi
type, where
the magnesium and the silicon content lie in an area of the ternary
equilibrium phase diagram
for AIMgSi alloys limited by the boundary points
A = 1 % silicon/ 0.6 % magnesium
B = 1.8 % / 0.6 % magnesium
silicon
C = 1.8 % / 0.2 % magnesium
silicon
D = 1.2 % / 0.2 % magnesium.
silicon
Figure 1 shows the equilibrium phase diagram for such AIMgSi alloys and the
corresponding
composition limits that define the field in question. Figure 1 is the ternary
phase diagram for
the AIMgSi alloys i.e. the diagram showing the solubility limits in the solid
state and has been
taken from METALS HANDBOOK, 8th edition, Vol. 8, Metallography, Structures and
Phase Diagrams, ASM, 1973, S. 397 and plotted on orthogonal axes.
Case 2032
CA 02151786 2004-O1-14
-3-
The outer layers are in particular in the form of sheets, strips and thin
strips of high
mechanical strength, good formability and low Baring properties. In
particular, e.g. in the
case of the above mentioned AIMgSi alloys, the magnesium and silicon contents
of the
AIMgSi alloys may be selected such that, at the homogenisation and solution
treatment
temperature of 450°C to 550°C which is normal for this type of
alloy, they exhibit a
silicon-excess of at least 0.1 %, preferably at least 0.2 °Io which
cannot be dissolved in the
alpha matrix and is in a finely dispersed form in that matrix, the total
silicon content being
at most 1.8 % Si. The alloy out of which the outer layer is made, may also
contain
additions of at most 0.3 % chromium, manganese, zirconium and/or titanium.
'The alloy
for the outer layers may be manufactured by continuous casting or strip
casting, hot and
cold rolling to the required sheets, coils and thin strips, the alloy
preferably being cooled
in the air after hot rolling. The cold rolled alloy may be solution treated
for up to 2 hours,
preferably 1 hour and in particular at most 30 minutes including heating up
time. A highly
preferred version is such that, in the course of cold rolling, the alloy is
solution treated at a
thickness of 1 to 5 times the final thickness, preferably at 1.3 to 4 times
the end thickness,
quenched, naturally age-hardened and cold rolled to final thickness in this
condition.
Useful is a composite panel having a 20 to 150 dun thick core layer on both
sides of which
is a 400 to 1600 pm thick outer layer of aluminium alloy. Preferred are
composite panels
having a 25 to 50 Pm thick core layer. Preferred are composite panels having
400 to 1500
thick outer layers. The core layer of plastic may be a material that is soft
under shear
loading conditions e.g. an elastomer or a thermoplastic. Suitable
thermoplastics are e.g.
polyolefins of the polyethylene type and polypropylenes, whereby, crystalline
and amor
phous or mixed forms rnay be employed. Further core layers of plastic may be
of the
polyurethane type or of the type containing acrylics, in particular acrylic
viscoelastic
polymers may be selected for this purpose. The thermoplastic polymers may for
example
also be a copolymer of polyethylene or polypropylene and an ethylene type
unsaturated
carboxylic acid. The preferred carboxylic acid is acrylic acid.
The core layer may exhibit a short-time elastic modules of 103 to 108 Pascal
and a loss
factor of GII/GI of 0.1 to 1 in the service temperature range. The service
temperature may
be e.g. from - 40°C to + 100°C and usefully from - 10°C
to + 40°C.
The plastic core layer may be for example a 25 to 150 Nm thick film or a 20 to
150 ~
thick laminate of films or a 20 to 150 um thick coating. The total thickness
of coatings,
however, is preferably 25 to 50 lun . A film or film laminate may exhibit for
example a
lower and upper adhesive layer and between these the film or film laminate.
The adhesive
Case 2032
CA 02151786 2004-O1-14
-4-
layer may be both an adhesive in the form of a coating or a layer, or may be
an adhesive
film. The adhesive may be employed in amounts of e.g. 0.1 to 15 g/m2, or an
adhesive film
may e.g. be 6 to 25 um thick. A film laminate may for example be made up of
two or
more monofilms of the same or of different plastics. The formable composite
panel
according to the present invention preferably feature a lower and an upper
outer layer and
between them the above mentioned core layers. Among the useful versions of
composite
panels are those with an upper and lower outer layer and with a core layer in
the form of a
plastic film that exhibits adhesive properties towards the metal layers. In
another preferred
version the core features a plastic film or a plastic film laminate which is
joined on both
sides to the outer layers. It is also possible to provide one or both outer
layers with a layer
of adhesive in liquid or pasty form or in the form of a dry coating, and to
bring the coated
side of the outer layer into contact with the non-coated side of an untreated
outer layer or
to bring both adhesive treated sides of the outer layers into contact with
each other and to
join these permanently to each other. The adhesive layer may be deposited e.g.
by
brushing, spraying, wiping, rolling etc. either over the whole surface or only
part thereof
e.g. in the form of a pattern on the outer layer surfaces) in question. If
desired, a solvent
or dispersion agent may be removed under reduced pressure and/or under the
influence of
heat or simply by allowing to dry. The outer layers, may be joined permanently
to each
other under the influence of pressure and/or heat, this whether employing the
aid of
adhesives, films, or adhesives and films.
The composite panels according to the present invention may find application
in a form
featuring two outer layers of the same or different thickness. When outer
layers of
different thickness are employed, the thickness of the second outer layer may
be up to 4
times the thickness of the first outer layer. An outer layer of 1.1 to 3 times
the thickness of
the first layer is preferred. Different thicknesses of outer layers result in
panels of higher
bend strength than monolithic panels of the same overall thickness. If the
application calls
for low weight, then the thickness of one of the outer layers should be as
small as possible.
Preferred are composite panels comprising a core with an outer layer on both
sides of the
core, where one outer layer is thicker than the other outer layer, and the
outer layers are
of an alloy of elevated strength belonging to the AA 6XXX, AA 7XXX or AA SXXX
series of alloys having a manganese content greater than 3%. Such composite
panels
exhibit a high degree of stiffness, especially the thicker outer layer is on
the outside of a
shaped part. Also preferred are composite panels having a core layer and two
outer layers,
where one of the outer layers is of a soft aluminium alloy from the alloy
series AIMn,
AIMg with a magnesium content of less than 3%, or AIFeSi. Such composite
panels
Case 2032
CA 02151786 2004-O1-14
-5-
exhibit good formability and an excellent appearance after coating, especially
when the
outer layer is of a soft alloy.
Composite panels according to the invention having two outer layers may
feature outer
layers of the same or different alloys.
One or both outer layers may be provided with a roughening pattern on one or
both sides.
Especially for the purposes of adhesive joining a surface with a roughening
pattern offers
a higher specific surface area.
The texturing of the surface with a roughening pattern is usefully done by
means of work
rolls exhibiting an appropriate roughening pattern which is transferred to the
surface of
the outer layers in an embossing roll pass with small reduction in thickness.
As in all
embossing processes, the topography of the work roll and therefore that of the
embossed
surface are complementary to one another i.e. peaks or raised parts on the
roll surface
become valleys or recesses in the surface of the component and vice versa.
In the case of aluminium or aluminium alloy sheets the transfer of the
roughening pattern
of the work rolls to the sheet is preferably performed during the last cold
roll pass with a
reduction of 3 to 5%.
Suitable roughening patterns for performing the process according to the
invention can be
achieved by embossing the surface with a texture from work rolls, the surface
of which
has been roughened by the following processes.
1. Spark erosion processes (EDT - electrical discharge texturing). In EDT
processes the
roll is turned past a row of electrodes accompanied by axial oscillation,
whereby the
surface is textured to a predetermined depth. The discharge of electrical
energy
between the roll surface and the electrodes through a dielectric fluid between
electrodes and roll surface, causes small craters to form on the roll surface.
The rough-
ess of the roll can be selected in a known manner by means of a series of
machine para-
meters. The roughness pattern is a statistical distribution of peaks and
valleys. The
EDT process enables average roughness values Ra of 1 to 6 jlm to be selected.
Average value and peak number are to a large extent related to one another.
Suitable
for the process according to the invention is a surface texture of low
roughness and
high peak number.
Case 2032
CA 02151786 2004-O1-14
-6-
2. Shot blast methods (SBT - shot blast texturing) . In the case of SBT the
sharp edged
shot is fed to a centrifugal wheel which propels the shot onto the roll. On
striking the
surface of the roll the individual particles of shot lose their kinetic energy
and in the
process plastically deform the surface of the roll. The roughness of the roll
may be
regulated by the choice of shot particulate size, the speed of rotation of the
centrifugal
wheel and other machine parameters. Average roughness values Ra of 1.5 to 6
lun may
be achieved this way. Here too, the roughness pattern corresponds to a
statistical
distribution of peaks and valleys.
3. Lasertex methods. In this process a laser beam is focused onto the roll
surface by
means of a lens and interrupted by means of a chopper wheel. In the process,
the roll is
rotated and displaced along its axis of rotation. The roll material is melted
locally at the
point of focus of the beam.. The desired roughness is achieved via the speed
of rotation
of the roll, the power of the laser and the point of focus of the laser beam.
The rough-
ness pattern has the appearance of a uniform distribution of craters on the
roll surface.
4. Electron beam processes. (EBG - electron beam graying). In the EBG process
a rotat-
ing roll is led, under vacuum, past a stationary electron beam generator. On
striking the
roll, the high energy electrons release their energy in the form of heat. If
the
temperature is sufficiently high, the volume of material struck is melted and
partially
evaporated. The roughness pattern appearing on the roll is comparable with
that
produced by the lasertex method. The crater depth of the can be adjusted at
will and
. depends on the duration of impingement of the beam. The crater diameters
depend on
the focusing of the electron beam.
5. Isomill process. In the Isomill process the roll surface is engraved in the
circumferential
direction and in the transverse direction to produce a roughness pattern that
is essen-
dally quadratic in form.
The outer layers may, if desired, be anodised, be treated with another process
that thick-
ens the oxide layer, or they may be decoratively anodised. Also, the surfaces
of the outer
layers may be provided with conversion layers e.g. a chromate or phosphate
conversion
layer. Likewise, especially the visible surfaces of the composite panels may
be altered
structurally and/or chemically i.e. by coating, chromating, phosphadng and
provided with
other layers that change the attractiveness of the material or improve the
surface. The
composite panels according to the present invention may be manufactured in the
form of
Case 2032
,._ -7- _
panels or in strip form, and the strips may be rolled or coiled and then
uncoiled and cut to
size according to the requirements of its use.
The present invention relates also to a process for manufacturing the
composite panel
according to the invention, whereby a first outer layer, is for example
uncoiled from a
spool and one of the surfaces is covered completely with an adhesive film as
the core
layer. As a rule the adhesive film contains a protective layer in order to
prevent the
adhesive film from adhering to itself and to the alignment and pressure rolls.
The adhesive
side of the film is brought into contact with the surface of the outer layer
and joined
permanently to it by means of rolls applying pressure to it. Following that,
the protective
film is pulled off the adhesive film. A second outer layer is uncoiled from a
second spool
and brought onto the adhesive layer; under the influence of pressure and/or
heat, for
example by passing between rollers or rolls or in a strip press or the like,
the second outer
layer is joined permanently to the outer layer and adhesive film laminate to
give a three
layer laminate. This composite may again be coiled up or be cut to size
immediately.
In another manufacturing process the composite panels according to the
invention may be
produced as follows. A first outer layer is e.g. uncoiled or unrolled. An
adhesive in liquid
to pasty form is applied, covering one of the surfaces of the first outer
layer, for example
by spraying, brushing or wiping or the like, and any solvent present removed
under
reduced pressure and/or elevated temperature. The adhesive forms the core
layer. The
second outer layer, likewise e.g. uncoiled strip, is unrolled and preheated
and then the first
outer layer with the coating of adhesive and the preheated second outer layer
presented to
each other such that the adhesive lies between the two outer layers. The outer
layers are
joined together permanently by means of rollers or rolls or in a strip press,
for example
under pressure and/or temperature, if necessary cooled and coiled again or cut
directly to
size. In this process the second layer may be prepared e.g. in such a way that
the outer
layer is previously covered with an adhesive as core layer in liquid to pasty
form, any
solvent present removed under reduced pressure and/or heat and, if desired,
also a
protective film laid over the adhesive, and the strip coiled up again. If now
such a coiled
strip is employed, one adhesive layer may be brought into contact with the
other adhesive
layer, whereby a more intimate join is achieved between the adhesive layers
than would be
possible between the adhesive layer and metal. The layers of adhesive form the
actual core
layer in the final composite.
Figure 2 shows a cross-section anywhere in a formable panel according to the
invention,
comprising for example of the two outer layers 1 and 3 and the core layer 2.
Case 2032
21517
The present invention relates also to shaped parts containing the formable
panel according
to the present invention. Shaped parts may be for example body parts of road
bound
vehicles, housings, parts of housings for machines and equipment, covers and
cladding for
machines, equipment and buildings. Car body parts may be for example car
bonnets, boot
lids, doors, wings, inner wings, parts separating passenger cabin and engine
space, interior
cladding of doors, roofs, bumpers or also chassis parts such as longitudinal
and transverse
beams or longitudinal and transverse stiffening elements. Housings and parts
of housings
for machines and equipment may be for example cylinder head covers or oil
sumps on
internal combustion engines, cladding for electromotors and the like; these
may also be
cladding parts for household equipment such as refrigerators, washing
machines, dish
washers, clothes washers, vertical and horizontal deep-freeze boxes etc.
Covers, dividing
walls, walls, floors, roofs etc., or shaped parts on buildings etc., may
likewise be included.
Parts that may be subject to vibration e.g. also housings or covers on
building machines or
testing equipment may also be manufactured out of the composite panels.
The composite panels may also be provided on one or both sides with cladding
or
decorative layers such as e.g. paint or other coating layers, or also layers
of plastic or
textiles or other textile-like material. For example, for the interior
cladding of vehicles,
such as vehicle doors, the composite panels may be clad with leather, leather-
like or textile
material.
The composite panels according to the present invention are fonmable into
almost any
shape e.g. by means of deep-drawing, stretch-drawing or by combinations of
both such
methods. Further, the composite panels can be joined by conventional joining
methods.
The composite panels according to the invention can be joined and so made into
larger
parts e.g. by means of resistance welding, stud welding, laser welding, spot
welding,
adhesive bonding, bolting, folding, flanging or clamping.
35
Case 2032
