Note: Descriptions are shown in the official language in which they were submitted.
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METAL-SKINNED COMPOSITE VEHICLE BODY PANEL
FIELD OF THE INVENTION
[0001] The present invention relates to body panels for vehicles.
BACKGROUND OF THE INVENTION
[0002] It is known in the automotive industry to use sandwich PANELS of carbon
fiber and aluminum honeycomb for vehicle body panels, particularly on very
expensive,
high performance sports cars. While such body panels are advantageous in that
they are
typically much lighter than conventional steel body panels while being able to
match a
steel panel in terms of strength, their use has traditionally been limited to
very expensive
and/or very low production volume vehicles for several cost-related reasons.
One reason
in particular is that a lot of labour is typically involved in providing these
body panels
with a class `A' surface finish that is paintable and suitable for use as an
exterior surface
of the vehicle. As a result, higher production volume vehicles and vehicles at
a more
reasonable price point are not provided with these body panels even though
there is
generally a strong motivation in the automotive industry to lighten vehicles.
It would be
beneficial if the costs associated with these types of body panel could be
reduced so that
the benefits thereof can economically be applied to higher production volume
vehicles
and to vehicles that are at a more affordable price point for an average
consumer.
SUMMARY OF THE INVENTION
[0003] In a first aspect, the invention is directed to a vehicle body panel
that
includes a first layer made of a metal, a second layer that contains resin
that contains
fiber material, a third layer made from a third layer material that defines a
plurality of
structural cells, and a fourth layer that contains resin that contains fiber
material.
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[0004] In a preferred embodiment, the layers have specific properties. The
first
layer is not more than about 0.016 inch thick and that is made from a 2024-T3
Aluminum
alloy. The second layer is not more than about 0.010 inch thick and that is
made up of an
epoxy that contains fiber material; the third layer is made up of a plurality
of hexagonal
honeycombs oriented generally perpendicularly to the first layer. The third
layer is made
from 5052 aluminum having a sheet thickness of not more than about 0.0007
inch. The
third layer has a layer thickness of not more than about 0.080 inch. Each
honeycomb cell
is not more than about 1/8 inch wide across the hexagon (from face-to-face, as
opposed to
the distance from vertex to vertex). The fourth layer is made up of a second
resin that
contains fiber material.
[0005] In a second aspect, the invention is directed to a method of making a
vehicle body panel in a die having a first die plate and a second die plate,
comprising:
inserting a first layer preform in the second die plate, wherein the first
layer preform is made up of a metal;
inserting a charge kit in the first die plate, wherein the charge kit is made
up of a second layer, a third layer and a fourth layer all joined together,
wherein the
second layer contains resin that contains fiber material, wherein the third
layer is made up
of a plurality of honeycombs oriented generally perpendicularly to the first
layer preform,
and wherein the fourth layer contains resin that contains fiber material;
heating the charge kit sufficiently to cause the charge kit to permit
deformation;
closing the first and second die plates together to cause the charge kit to
conform to the space between the second die plate and the first layer preform
and to
cause the charge kit to join to the first layer preform;
hardening the charge kit to form a molded part that includes the charge kit
and the first layer preform;
opening the first and second die plates; and
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removing the molded part from the die.
[0006] In a third aspect, the invention is directed to another method of
making a
vehicle body panel in a die having a first die plate and a second die plate
wherein the first
and second die plates together define a die cavity, comprising:
inserting a charge kit in the first die plate, wherein the charge kit is made
up of a first layer, a second layer, a third layer and a fourth layer all
joined together,
wherein the first layer is made from metal, the second layer contains resin
that contains
fiber material, the third layer is made up of a plurality of honeycombs
oriented generally
perpendicularly to the first layer preform, and the fourth layer contains
resin that contains
fiber material;
heating the charge kit sufficiently to cause the charge kit to permit
deformation;
closing the first and second die plates together to cause the charge kit to
conform to the die cavity;
hardening the charge kit to form a molded part;
opening the first and second die plates; and
removing the molded part from the die.
[0007] In a fourth aspect, the invention is directed to another method of
making a
vehicle body panel in a die having at least a first die plate wherein the
first die plate
defines a first die cavity portion, comprising:
inserting a charge kit in the first die plate, wherein the charge kit is made
up of a first layer, a second layer, a third layer and a fourth layer all
joined together,
wherein the first layer is made from metal, the second layer contains resin
that contains
fiber material, the third layer is made up of a plurality of honeycombs
oriented generally
perpendicularly to the first layer preform, and the fourth layer contains
resin that contains
fiber material;
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heating the charge kit sufficiently to cause the charge kit to permit
deformation;
applying pressure to the charge kit to cause the charge kit to conform to
the first die cavity portion;
hardening the charge kit to form a molded part; and
releasing the molded part from the die.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention will now be described by way of example only with
reference to the attached drawings, in which:
[0009] Figure 1 is an sectional view of a vehicle body panel in accordance
with
an embodiment of the present invention;
[0010] Figures 2a, 2b and 2c are parts of a table of test data showing the
performance of several different body panels, some of which are made in
accordance
with embodiments of the present invention;
[0011] Figures 3a-3g are sectional views of a die illustrating the process for
manufacturing the body panel shown in Figure 1
[0012] Figure 3h is another sectional view of the panel shown in Figure 1 and;
[0013] Figure 4 is a flow diagram illustrating the process for manufacturing
the
body panel shown in Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Reference is made to Figure 1, which shows a vehicular body panel 10,
in
accordance with an embodiment of the present invention. The body panel may be
any
suitable type of body panel, such as a hood, or a roof panel for a vehicle.
The body panel
10 is made up of a plurality of layers including: a first layer 12 made of a
metal, a second
layer 14 made of a resin containing fibers, a third layer 16 made of a
material containing
structural cells 17 and a fourth layer 18 made of a resin containing fibers.
The first layer
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12 is made from a metal that has a suitable combination of low density,
mechanical
strength and paintability. Examples of some materials that may be suitable
include
Aluminum alloys, Magnesium alloys, Titanium alloys and steel. Figures 2a-2c
show a
table of selected metals used in test samples of body panels.
[0014] The first layer 12 is thinner than metal sheet material that is
typically used
for vehicle body panels. For example, in a typical Aluminum alloy body panel
of the
prior art, the thickness of the sheet metal used therein may be approximately
0.040 inch
or more. By contrast, the sheet thickness of the first layer 12 may be as low
as about
0.008 inch, in particular where the material is a fully hard Aluminum alloy,
such as 1100-
H 18 Aluminum alloy. The sheet thickness of the first layer 12 may be as low
as about
0.012 inch, in particular where the material is a half-hard Aluminum alloy.
The range of
acceptable sheet thickness for the first layer is between about 0.008 inch and
about 0.016
inch.
[0015] Some other Aluminum alloys that may be used for the first layer 12
include: 2024-T3 and 6061-T6.
[0016] Where the first layer material is a Magnesium alloy, particular an
alloy
that is tempered to a half hard state, the thickness of the first layer may be
in the range of
about 0.016 inch or greater. The thickness may be less than, for example,
0.020 inch. A
particular alloy that maybe used is AZ31B-H34.
[0017] By making the first layer from a relatively thin sheet, the costs
associated
with stamping and/or otherwise forming or cutting the first layer 12 are
reduced
compared to the costs associated with the forming of sheet metal used for
conventional
vehicle body panels (ie. body panels that are made from sheet metal only).
[0018] The first layer 12 has a first surface 20 that has a class `A' finish
that
makes it suitable for painting as a visible exterior surface of the vehicle.
The preparation
of the first surface 20 to make it suitable for use as an exterior surface is
well known. By
providing the metallic first layer, the comparatively laborious treatment that
is required
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for preparing some resin surfaces to be suitable as paintable exterior
surfaces, is avoided.
The first layer 12 has a second surface 21 that is opposed to the first
surface 20.
[0019] The second layer 14 is a resin that includes fiber material, and joins
the
first layer to the third layer. The resin itself may be any suitable type of
resin such as an
epoxy. The table in Figures 2a-2c shows several examples of second layer
material that
can be used. The fiber may be any suitable type of fiber. The fiber may be
weaved, and
if so, it may have any suitable angle to the weave relative to the
longitudinal axis of the
vehicle on which the body panel 10 is to be used. For example, the weave may
be at 0
degrees and 90 degrees relative to the vehicle's longitudinal axis.
Alternatively, the
weave may be at -45 degrees and +45 degrees relative to the vehicle's
longitudinal axis.
Alternatively, the fibers may instead be unidirectional. The fibers may be
provided in
some combination of the aforementioned possibilities. In an alternative
embodiment, the
fibers may instead be randomly oriented, and may be less than about 1 inch in
length.
The fibers may be glass fibers, aramid fibers, carbon or graphite fibers,
polyethylene
fibers or other types of fiber.
[0020] The resin may be a thermoset material, such as, for example, epoxy,
urethane, vinyl ester, polyester or a polyamide. Alternatively, the resin may
be a
thermoplastic material, such as polyethylene, polypropylene, or nylon.
[0021] An exemplary material that can be used for the second layer 14 is
MTM28/GFO100, which is an epoxy with a glass fabric made by Advanced
Composites
Group Inc. of Tulsa, Oklahoma, USA.
[0022] The second layer 14 may be made up of a single ply or multiple plies of
material. Where multiple plies are provided, all the plies are preferably made
from a
resin that contains fibers. It is optionally possible for the plies to differ
in terms of their
composition.
[0023] The thickness of the second layer 14 may be within a range of about
0.006
inch to about 0.016 inch for some single ply configurations, and may be up to
about
0.028 inch for two-ply configurations.
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[0024] The second layer 14 has a first surface 22 that mates with the second
surface 21 of the first layer 12, and a second surface 24 that is opposed to
the first surface
22.
[0025] The third layer 16 is made up from a third layer material that defines
a
plurality of structural cells 17. In the embodiment shown in Figure 1, the
cells 17 are in
the form of hexagonal honeycombs that are oriented generally perpendicularly
to the first
layer. Alternatively, the cells 17 may be in some other form such as diamond-
shaped
honeycombs, square honeycombs, or any other suitable type of honeycomb. For
the
purposes of the present disclosure and claims, a honeycomb is intended to
denote a
hollow, polygonal structure that is not necessarily limited to being a
hexagonal structure.
[0026] The third layer material may be any suitable material, such as 5052
Aluminum alloy. The wall thickness of the third layer material may be
approximately
0.0007 inch. In an exemplary embodiment where the cells 17 are hexagons, the
size of
each cell 17 may be less than or equal to about 1/8 inch across the hexagon
(face-to-face).
The density of the honeycomb formed with the aforementioned Aluminum alloy may
be
about 3.1 lbs/cu. ft.
[0027] The thickness of the third layer 16 may be between about 0.080 inch and
about 0.100 inch, particularly when the cells 17 are hexagonal honeycombs.
Other
thicknesses may, however, alternatively be used.
[0028] A preferred honeycomb for use in the body panel 10 is under the
material
spec: 3.1 1/8 0.0007N 5052 aluminum, made by Hexcel Corporation, Stamford,
Connecticut, USA.
[0029] The third layer 16 has a first surface 26 and a second opposing surface
28.
The first surface 26 is connected to the second surface 24 of the second
layer.
[0030] The fourth layer 18, and covers the opposite side of the third layer
16.
The fourth layer 18 has a first surface 30 and a second surface 32. The first
surface 30 is
connected to the second surface 28 of the third layer 16. The second surface
28 may be
exposed, since it does not have to have a class `A' finish, because it is not
a surface of the
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vehicle that is visible during normal use of the vehicle. This does not mean
that the
second surface 32 of the fourth layer 18 can never be visible to a person
using the vehicle
or located near the vehicle. For example, in an embodiment where the body
panel 10 is a
hood, the second surface 32 of the fourth layer 18 may be the underside of the
hood,
which is only visible when the hood is opened, and which is therefore not
visible during
normal use of the vehicle.
10031] In a particularly preferred embodiment, the first layer 12 is an
Aluminum
alloy that is half-hard with a thickness of about 0.012 inch; the second layer
14 is a single
ply of epoxy with glass fabric under the product number MTM28/GFO100 made by
Advanced Composites Group, with a thickness of 0.010 inch; the third layer 16
has a
layer thickness of 0.08 inches and is made up of hexagonal honeycombs with a
density of
3.1 lb./cu. ft. and have a dimension of 1/8 inch across the hexagon (face-to-
face), with
walls that are non-perforated and made from 0.0007 inch thick 5052 Aluminum
alloy;
and the fourth layer 18 is the same thickness and material as the second layer
14.
[0032] A method for manufacturing the body panel 10 is described as follows,
with reference to Figures 3a-3h. As shown in Figure 3g, a die 40 which defines
a die
cavity 41 (Figure 3g) is provided for molding the body panel 10. The die 40
includes a
first die plate 42 containing a first die cavity portion 44 (Figure 30, and a
second die
plate 46 containing a second die cavity portion 48. In the exemplary
embodiment shown
in Figures 3a-3h, the die plates 42 and 46 extend generally horizontally and
are movable
along a vertical axis A between the open and closed positions. It will be
understood that
this does not mean that both die plates 42 and 46 must be moveable. It is
intended to
cover embodiments wherein one die plate (eg. the second, or upper die plate
46) is
movable, while the first die plate 42 is stationary. The die plates 42 and 46
are movable
between an open position wherein they are separated by a selected amount, and
a closed
position wherein they mate together. In the open position, one or both of the
die plates
42 and 46 can receive the materials to be molded, and also a molded part can
be removed
from one of the die cavity portions 44 and 48. In the closed position, the
materials fed
into the die cavity are molded and hardened (eg. cured) as necessary. The
method of
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manufacture is shown at 100 in Figure 4. Figures 3a-3h illustrate steps in the
method
shown in Figure 4. An optional first step 102 (Figure 4) is provided in the
event that an
add-on element 51 (Figure 3b) will be mounted to the body panel 10. At step
102 a
support 52, which is used to support the add-on element 51, is positioned at a
selected
position on the first mold plate 42. The support 52 may be made from any
suitable
material, such as, for example, one or more plies of fiberglass. In an
embodiment
wherein the body panel 10 is a hood, there may be several add-on elements 51,
including,
for example, a latch, one or more hinges, and a prop rod insert block.
Accordingly, there
by may be several supports 52 positioned at selected positions on the first
die plate 42.
The first die plate 42 is heated so that the support 52 heats up thereby
increasing
malleability.
[0033] At step 104 (Figure 4), the add-on element 51 (Figure 3b) is positioned
in
the support 52. The support 52, which has been heated somewhat and is somewhat
malleable as a result, is urged down into an associated depression 54 in the
first die plate
42. The depression 54 is part of the first die cavity portion 44. The support
52 need not
be positioned all the way down into the depression 54 at step 104.
[0034] At step 106 (Figure 4), a charge kit 56 (Figures 3c and 3d), which is a
preformed sandwich of the second, third and fourth layers 14, 16 and 18, is
provided and
is positioned in the first die plate 42. In some embodiments, particularly
wherein the
charge kit 56 is positioned manually by an operator into position in the first
die plate 42,
the charge kit 56 is provided with one or more locating apertures 58 which
mount on one
or more locating dowels 60 projecting from the surface of the die plate 42.
The locating
apertures 58 and the locating dowels 60 ensure that the charge kit 56 is
positioned in a
selected position on the die plate 42. The apertures 58 may optionally be
sized to fit
snugly on the dowels 60. Alternatively, one or more of the apertures 58 may be
in the
form of slots.
[0035] The charge kit 56 may be preformed at a separate station (not shown)
where a CNC machine cuts the second, third and fourth layers to desired sizes.
The
layers 14, 16 and 18 are then placed in their respective positions to form the
sandwich.
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The second and fourth layers 14 and 18 extend beyond the edges of the third
layer 16,
and together form an edge portion 61. Along the edge portion 61, the second
and fourth
layers 14 and 18 may be stapled or otherwise joined by some suitable means
thereby
substantially fixing the position of the third layer 16 in between them. In
embodiments
where the second and fourth layers 14 and 18 are stapled, the staples used
therefor are
positioned outside any portions of the die plates 42 where they will damage
the surfaces
62 and 64 on the first and second die plates that make up the die cavity 41
(Figure 3g).
The locating apertures 58 are also provided in the edge portion 61.
[0036] At step 108 (Figure 4), a first layer preform 66 (Figure 3e) is
provided and
is positioned in the second die plate 46. The first layer preform 66 forms the
first layer
12 in the body panel 10. The first layer preform 66 is already formed into
substantially
its final shape prior to insertion in the second die plate 46. The forming of
the first layer
preform 66 can be carried out in another station (not shown). As a result of
its close fit
with the surface 64 that defines the second die cavity portion 48, locating
apertures are
not necessary for the first layer preform 66. A vacuum chuck system may be
provided in
the second die plate 46 to hold the first layer preform 66 in place in the
second die cavity
portion 48.
[0037] Prior to insertion into the second die plate 46, any protective
covering that
may be present on the first layer preform 66 is removed. Additionally, the
metallic first
layer 12 may undergo a cleaning process to prepare it for joining to the
second layer. The
cleaning process may include a solvent wash. Alternatively, the cleaning
process may be
electro-chemical, such as anodizing (in embodiments wherein the first layer is
made from
an Aluminum alloy).
[0038] At step 110 (Figure 4), and as shown in Figures 3f and 3g, the second
die
plate 46 is moved towards the first die plate 42 so as to bring the first
layer preform 66
into contact with the charge kit 56 with a selected joining pressure. The
locating dowels
60 are at this time received in dowel receiving apertures 67 in the second die
plate 46.
The joining pressure is selected to provide a close bond between them and
between the
elements that make up the charge kit 56. At the joining pressure, the third
layer 16 is
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crushed by a selected amount. The amount of crushing of the third layer 16
depends on
the region of the die cavity 41. Initially the pressure may be about 75 psi,
and then may
be increased to the joining pressure using any suitable method. At the joining
pressure,
the main portion, shown at 68, of the body panel 10, the third layer 16 may be
crushed by
about 5% to about 10% of its uncrushed thickness. In a hem portion 70 that is
outside of
the main portion 68, the die cavity 41 may be sized to substantially
completely crush the
third layer 16. The die 40 may be kept closed for any suitable amount of time
to permit
the second and fourth layers 14 and 18 to harden (to cure in the case where a
thermoset
material is used (eg. epoxy), or to form in the case where a thermoplastic
material is
used).
[0039] The temperature that is used to cure the second and fourth layers 14
and
18 in embodiments wherein they are thermoset materials may be about 300
degrees F to
about 600 degrees F. The time required for the material to cure may be, for
example,
between about 2 minutes and 10 minutes. In the case where a thermoplastic
material is
used for one or both of the second and fourth layers 14 and 18, the forming
time for the
thermoplastic material may be less than 2 minutes.
[0040] At step 112, once the material in the die cavity 41 has been cured (or
otherwise hardened), the die 40 is opened and the molded part (shown at 68 in
Figure 3g)
is removed therefrom. In some embodiments the molded part 68 may be removed
while
hot. At step 114, the edge portion 61 is trimmed from the molded part 68. The
trimming
may be carried out by any suitable means, such as by shears, shearing dies,
saws, cutting
discs, laser, abrasive waterjet, and CNC cutting tools.
[00411 At step 116, the molded part 68 is hemmed thereby forming the body
panel 10. This hemming step 116 may entail applying mastic at a suitable
location (ie.
to, or proximate to the hem portion 70), folding over the hem portion 70 so
that the
mastic holds it in the folded position thereby forming a hem.
[0042] It is optionally possible to form the metallic first layer 12 in the
die 40 at
the same time as the second, third and fourth layers 14, 16 and 18 are formed,
instead of
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preforming the first layer. In such a case, the pressures in the die 40 that
cause the
selected amount of crushing of the third layer 16 would also have to be high
enough to
form the first layer 12 into the desired shape. The feasibility of this
process would
depend on several factors such as the geometry (both initial and final) of the
first layer
12, the material properties of the first layer 12 and of the second, third and
fourth layers
14, 16 and 18. In such an embodiment, the charge kit may be made up of all
four layers
12, 14, 16 and 18 placed together into the first die cavity portion 44. In
such an
alternative, the first layer 12 could be joined to the second layer 14 in the
charge kit in
any suitable in any suitable way. A benefit of this alternative embodiment is
that the step
of separately preforming the first layer 12 would be avoided, thereby saving
cost, labour
and floor space associated with that step.
[0043] In another alternative, the die 40 may be made up of a single die plate
that
may be similar to the lower die plate 42 (Figure 3a) that defines a die cavity
portion for
receiving the charge kit. An elastomeric sheet would then be pressed against
the charge
kit to push the charge kit into the die cavity portion in the die plate. Fluid
pressure or
some other suitable pressure generating means is provided on the other side of
the
elastomeric member so as to cause the elastomeric member to press against the
charge
kit. The single die plate is heated so as to soften the charge kit.
Alternatively any other
means of generating pressure and using the pressure to urge the charge kit
into a die
cavity portion could be used to form the molded part 68.
[0044] While the above description constitutes a plurality of embodiments of
the
present invention, it will be appreciated that the present invention is
susceptible to further
modification and change without departing from the fair meaning of the
accompanying
claims.
