U.S. patent application number 14/249579 was filed with the patent office on 2015-10-15 for process for joining carbon fiber composite materials using self-piercing rivets.
This patent application is currently assigned to Ford Global Technologies, LLC. The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Aindrea McKelvey Campbell, Amanda Kay Freis, Garret Sankey Huff.
Application Number | 20150290914 14/249579 |
Document ID | / |
Family ID | 54264355 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150290914 |
Kind Code |
A1 |
Campbell; Aindrea McKelvey ;
et al. |
October 15, 2015 |
Process For Joining Carbon Fiber Composite Materials Using
Self-Piercing Rivets
Abstract
A joint and related method. The joint includes bottom and top
layers contacted to form first and second contacting portions. The
bottom layer is a fiber composite material that is non-ductile at
room temperature. A joint member joins the bottom and top layers
such that the joint and the top layer are unexposed through the
bottom layer.
Inventors: |
Campbell; Aindrea McKelvey;
(Beverly Hills, MI) ; Huff; Garret Sankey; (Ann
Arbor, MI) ; Freis; Amanda Kay; (Ann Arbor,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
Ford Global Technologies,
LLC
Dearborn
MI
|
Family ID: |
54264355 |
Appl. No.: |
14/249579 |
Filed: |
April 10, 2014 |
Current U.S.
Class: |
411/502 ;
156/272.2; 156/308.2; 156/92 |
Current CPC
Class: |
B29K 2063/00 20130101;
B29C 66/7422 20130101; B29C 66/0242 20130101; B32B 2605/00
20130101; B29C 66/74283 20130101; B29C 66/742 20130101; B29C 65/14
20130101; B29C 66/73117 20130101; B29K 2077/00 20130101; B21J
15/025 20130101; B29C 65/10 20130101; B29C 66/81433 20130101; B32B
2037/0092 20130101; B29C 65/564 20130101; B29C 66/8322 20130101;
B29K 2309/08 20130101; B29C 66/7394 20130101; B29C 66/21 20130101;
B29C 66/91945 20130101; B29C 65/36 20130101; B29C 66/71 20130101;
B29C 66/41 20130101; F16B 5/04 20130101; B29C 66/7392 20130101;
B29C 66/81431 20130101; B29C 65/02 20130101; B29C 66/7212 20130101;
B29C 66/919 20130101; F16B 19/086 20130101; B32B 2038/0096
20130101; B21J 15/08 20130101; B29C 65/72 20130101; B32B 38/0036
20130101; B21J 15/147 20130101; B29C 66/721 20130101; B29K 2307/04
20130101; B29C 65/562 20130101; B29C 66/1122 20130101; B29C 66/7212
20130101; B29K 2307/04 20130101; B29C 66/7212 20130101; B29K
2309/08 20130101; B29C 66/71 20130101; B29K 2063/00 20130101; B29C
66/71 20130101; B29K 2077/00 20130101 |
International
Class: |
B32B 37/18 20060101
B32B037/18; B32B 38/00 20060101 B32B038/00; F16B 19/08 20060101
F16B019/08; B32B 37/02 20060101 B32B037/02 |
Claims
1. A joint comprising: first and second components contacted to
form first and second contacting portions, the second component
being a fiber composite material being non-ductile at room
temperature; and a joint member joining the first and second
components such that the joint and the first component are
unexposed through the second component.
2. The joint of claim 1, wherein the joint member is a
self-piercing rivet ("SPR").
3. The joint of claim 2, wherein the SPR includes a head and a
shaft.
4. The joint of claim 3, wherein the SPR shaft contacts and extends
into the first component a length.
5. The joint of claim 1, wherein the first component is an aluminum
material.
6. The joint of claim 1, wherein the second component is a
composite material.
7. The joint of claim 1, wherein the first and second components
are first and second panels, respectively.
8. The joint of claim 1, wherein the fiber composite material is a
carbon fiber composite material.
9. The joint of claim 1, wherein the fiber composite material
exhibits increased ductile behavior at an elevated temperature.
10. A method comprising: contacting bottom and top layers to form a
joint between the two layers, the bottom layer being a non-ductile
fiber composite material at room temperature; elevating the
temperature of a fastening portion of the bottom layer to make the
fastening portion ductile; and joining the bottom and top layers
while the fastening portion is at the elevated temperature.
11. The method of claim 10, wherein the fastening portion is the
first contacting portion.
12. The method of claim 10, wherein the joining step includes
joining the first and second contacting portions with one or more
rivets.
13. The method of claim 10, wherein the elevated temperature is in
the range of 100 to 300.degree. C.
14. The method of claim 10, wherein the elevating step is carried
out using a radiant, inductive or convective heat.
15. The method of claim 10, wherein the fiber composite material
includes a carbon fiber material and a polymeric material.
16. The method of claim 10, wherein the elevated temperature is
within +/-30% of the glass transition temperature (in Kelvin) of
the fiber composite material.
17. A method comprising: contacting first and second panels to form
a joint between the two panels, the second panel being a
non-ductile fiber composite material at room temperature; elevating
the temperature of only a fastening portion of the second panel to
make the fastening portion ductile; and joining the first and
second panels while the second panel is at an elevated temperature
with one or more rivets to form a joined portion.
18. The method of claim 17, wherein the elevated temperature is in
the range of 100 to 300.degree. C.
19. The method of claim 17, wherein the fiber composite material
includes a carbon fiber material and a polymeric material.
20. The method of claim 17, wherein the elevated temperature is
within +/-30% of the glass transition temperature (in Kelvin) of
the fiber composite material.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a process for joining
carbon fiber composite materials, such as carbon fiber composite
panels, using self-piercing riveting.
BACKGROUND
[0002] Composite materials, such as composite material panels, are
used to manufacture structural and body panels for vehicles and
other products. The composite materials panels are typically made
of one or more polymeric resins reinforced with a material, such
as, but not limited to, carbon fibers, glass fibers and natural
fibers. Composite material panels are typically fabricated of
strong, light-weight materials. In certain applications, composite
material panels are joined to panels made of aluminum, steel or
other composite materials. Fasteners, such as, but not limited to,
clinch joints or rivets, may be used to join the dissimilar panels
together.
SUMMARY
[0003] According to one embodiment, a joint is disclosed. The joint
includes first and second components contacted to form first and
second contacting portions. The second component is a fiber
composite material that is non-ductile at room temperature. A joint
member joins the first and second components such that the joint
and the first component are unexposed through the second
component.
[0004] According to another embodiment, a method is disclosed. The
method includes contacting bottom and top layers to form a joint
between the two layers. The bottom layer is a non-ductile fiber
composite material at room temperature. The method further includes
elevating the temperature of a fastening portion of the bottom
layer to make the fastening portion ductile. The method also
includes joining the layers while the fastening portion is at the
elevated temperature.
[0005] In yet another embodiment, a method is disclosed. The method
includes contacting first and second panels to form a joint between
the two panels. The second panel is a non-ductile fiber composite
material at room temperature. The method also includes elevating
the temperature of only a fastening portion of the second panel to
make the fastening portion ductile. The method further includes
joining the first and second panels while the second panel is at an
elevated temperature with one or more rivets to form a joined
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A is a fragmented, perspective view of bottom and top
layers to be joined;
[0007] FIG. 1B is a cross-sectional view taken along the line 1B-1B
of FIG. 1A;
[0008] FIG. 2 is a schematic view of the steps of a process for
joining fiber composite materials using self-piercing riveting;
[0009] FIG. 3A is a cross-sectional view of a glass fiber composite
material panel joined to an aluminum panel using a self-piercing
riveting method;
[0010] FIG. 3B is a bottom view of the button of FIG. 3A;
[0011] FIG. 4A is a cross-sectional view of a carbon fiber
composite material panel joined to an aluminum panel using a
self-piercing riveting method;
[0012] FIG. 4B is a bottom view of the button of FIG. 4A;
[0013] FIG. 5A is a cross-sectional view of a carbon fiber
composite material panel joined to an aluminum panel using a
self-piercing riveting method that includes the application of heat
to the carbon fiber composite material; and
[0014] FIG. 5B is a bottom view of the button of FIG. 5A.
DETAILED DESCRIPTION
[0015] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention that
may be embodied in various and alternative forms. The figures are
not necessarily to scale; some features may be exaggerated or
minimized to show details of particular components. Accordingly,
specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a representative basis
for teaching one skilled in the art to variously employ the present
invention.
[0016] As the automotive industry strives to meet customer fuel
economy expectations and Corporate Average Fuel Economy (CAFE)
requirements, interest in alternative light-weight materials,
including, without limitation, fiber composite materials, has
increased. Joining methods for conventional steel structures have
traditionally used resistance spot-welding. In the case of vehicles
using aluminum and mixed metal joining applications, self-piercing
rivet (SPR) technology has been utilized. One benefit of SPR
technology is that it is capable of being implemented in high
volume production assembly processes. Further, it is compatible
with adhesive joining methods, and therefore, both methods can be
used in conjunction. However, the challenge often faced with SPR
technology is that the material of the panels being joined must be
ductile enough to form an adequate button. The button is a result
of creating the joint and providing suitable deformation to provide
adequate mechanical interlock and a button with acceptable
characteristics, e.g. the absence of unacceptable button
cracking
[0017] Composite materials, such as carbon fiber or glass fiber
composite materials, have not been found suitable for certain
joining processes and related materials. Certain of these composite
materials often have limited ductility and are not susceptible to
the large displacements and deformation required to produce an
adequate SPR button. One problem is that the reinforcing fibers may
break through the surface of the composite panel. Carbon or natural
fiber reinforcing fibers may absorb moisture if they break through
the surface of the composite panel. Fibers that absorb moisture can
be objectionable because they may cause corrosion and may weaken
the joints. Carbon fibers, when exposed to moisture, may cause
galvanic corrosion when the fibers come into contact with metal
parts or fasteners.
[0018] While adhesive joining processes have been used to join
composite materials, the use of these processes results in a lower
volume production method. Further, until the adhesive cures, the
uncured joint is susceptible to displacement and/or movement
between the parts or panels being joined. A joining solution which
can be integrated into high volume production requirements is
needed for joining low ductility fiber composite materials. One or
more embodiments of the present invention relate to a method for
joining fiber composite materials using SPRs that produces a button
with superior shaping characteristics (and mechanical
interlock).
[0019] In one or more embodiments, ductility refers to plasticity
or the extent to which the material can be plastically deformed
without fracture. While fiber composite materials have relatively
low ductility, metals and metal alloys tend to have high ductility.
In contrast, fibrous composite materials are typically non-ductile
at ambient temperatures. In one or more embodiments, the present
invention is directed to a process to improve the ductility of
fiber composite materials prior to and/or during the self-piercing
riveting joining process.
[0020] Composite materials may include carbon fiber and glass fiber
composites, natural fibers, flakes, or particles, and combinations
thereof. Composite materials can be produced with a variety of
different fiber densities and formats. Non-limiting examples of
composite material formats include randomly dispersed fibers or
aligned fibers. Composite materials may have various matrix
materials (otherwise referred to as surrounding materials),
including without limitation thermoplastic polymers, such as
polyamide or thermosets, such as epoxy.
[0021] FIG. 1A depicts a fragmented view of bottom layer and top
layer 10 and 12 to be joined using SPRs. The bottom layer is
adjacent to the die when set on the riveting machine, as described
in more detail below. FIG. 1B is a cross-sectional view taken along
the line 1B-1B of FIG. 1A and shows first contacting portion 14 of
bottom layer 10 and second contacting portion 16 of top layer 12.
Bottom layer 10 may be formed of a composite material. Top layer 12
may be formed of an aluminum alloy, steel, magnesium alloy. The
bottom and top layers collectively define a fastening region 18
that later receives a fastener, such as, but not limited to an
SPR.
[0022] A heater 20 may be used to elevate the temperature of a
fastening region 18 to make the fastening region 18 ductile to
reduce cracking and fractures upon joining the bottom and top
layers 10 and 12. The first contacting portion 14 and second
contacting portion 16 are joined while at least a portion of
fastening portion 18 is at an elevated temperature. In one or more
embodiments, heat is applied to the composite material local to the
fastening region 18 and prior to joining the layers. In an
alternative embodiment, both bottom and top layers 10 and 12 are
formed of a fiber composite material.
[0023] The fiber composite material components can be heated to a
temperature near the glass transition temperature of the composite
material to achieve adequate ductility of the composite material.
Once the composite material reaches a desired elevated temperature,
layers 10 and 12 are joined through a process, such as riveting.
The composite material may be heated before or after the layers 10
and 12 are contacted. It should be understood that the components
to be fastened may include one or more fiber composite materials or
may be a fiber composite material with one or other materials such
as a metal. Metals, such as, but not limited to, aluminum alloys,
steel or magnesium alloys, are used in sheet fabrication and
fastened by SPRs, including, but not limited to pan heads and
counter sunk rivets. The application of heat to fasten a
non-ductile fiber composite component may be used for other joining
methods including but not limited to flow-drill screwing and
clinching, as increasing the ductility of the composite layer is
advantageous for these fastening techniques, as well.
[0024] The heat may be applied by radiant, inductive or convective
heat transfer while the components are on a conveyor or stationary.
Radiant heat may be provided by a hot surface such as an
electrically heated solid material or a light source. Convective
heat transfer may be provided by a heat gun or hot gas blower, such
as, blowers used in furnaces or hot-air impingement. The elevated
temperature of the composite material to change the material to
exhibit plastic or ductile behavior is dependent on the type of
matrix or resin material and is related to its glass transition
temperature. Epoxy materials may require up to 300.degree. C. to
achieve ductile behavior. For fiber composite materials, the
temperature for ductile behavior may range from 25 to 300.degree.
C., and, in one embodiment, from 100 to 250.degree. C. for carbon
fiber reinforced composite materials. The heat source is selected
to not pose a risk of damaging the composite material. In one
embodiment, the composite component and the other component are
contacted while the heat is being applied. To this end, high power
laser heating would not be acceptable, as it may chemically and
irreversibly degrade the constituents of the composite when under
intense localized heating. Moreover, the focused beam of the laser
may not heat the composite part over a sufficient area, as the
thermal conductivity may be significantly lower than what is found
in metals. Hence, heating via radiant (e.g., a near-infrared
source) or convection heating is contemplated in one or more
embodiments of the present invention.
[0025] Referring to FIG. 2, a schematic view of the steps according
to one method embodiment of the present invention for self-piercing
riveting of fiber composite materials is provided. Step 1 results
in the placement of bottom layer 10 (e.g., fiber composite
material) and top layer 12 (e.g., aluminum) so that they can be
joined at the fastening region 18. Step 2 shows the application of
heat from a heater 20 to elevate the temperature of at least a
portion of the fastening region 18. The heat may be applied to
either the bottom layer 10 at the first contacting portion 14 or
the top layer 12 at the second contacting portion 16, or to both
layers 10 and 12 of the first and second contacting portions 14 and
16, respectively. The heat may also be applied only to the external
surfaces of layers 10 and/or 12 to avoid chemical or irreversible
degradation of the layers.
[0026] The non-ductile components absorb heat to elevate the
temperature in the fastening region 18. The heat may be radiant or
conductive heat. The heat may be supplied from one or more heaters.
Step 3 illustrates rivet 22, punch 24, blankholder 26 and die 28
that are placed about the fastening region 18 to be joined. In step
4, punch 24 is lowered and begins to deform layers 10 and 12. In
step 5, rivet 22 is inserted, or pierced, into top layer 12 and the
bottom layer 10 material deforms into die 28 and button 30 is
formed. Step 6 shows button 30 and the joined layers 10 and 12.
[0027] FIG. 3A is a cross-sectional view of an aluminum panel 32
joined to a glass fiber composite panel 34 with an SPR 36. SPR 36
includes head 38 and shaft 40, which is deformed into an elliptical
shape upon extending into panels 32 and 34. SPR 36 extends into
both the glass fiber composite panel 34 and the aluminum panel 32.
Shaft 40 extends into aluminum panel 32 an orthogonal horizontal
distance from the intersection region 42 of the aluminum panel 32,
glass fiber composite panel 34 and SPR 36. The distance d.sub.1 on
the left cross-section of shaft 40 is about 0.20 mm and the
distance d.sub.2 on the right cross-section of shaft 40 is about
0.19 mm. As shown, there is minimal variation in the distances
d.sub.1 and d.sub.2. Joints formed with SPRs exhibiting sufficient
interlock and showing this minimal variation form a strong and
durable joint. Referring to FIG. 3B, a bottom view of button 44 of
FIG. 3A is shown. The button 44 is smooth and free of cracks or
paths for moisture permeation or egress and other flaws, which are
further characteristics of a robust and durable joint.
[0028] FIG. 4A is a cross-sectional view of an aluminum component
48 joined to a carbon fiber composite material component 50 using
an SPR technique at room temperature. SPR 52 includes head 54 and
shaft 56. Void 58 is formed between SPR 52 and aluminum component
48. Void 58 is shown in FIG. 4a. The joint shows poor interlock
with asymmetry of the SPR shaft 56. The orthogonal horizontal
distance d.sub.1 on the left cross-section of shaft 56 is about
0.17 mm and the distance d.sub.2 on the right cross-section of
shaft 56 is about 0.28 mm. As shown, there is a significant
variation in the distances d.sub.1 and d.sub.2. Joints formed with
SPRs showing this significant variation exhibit poor mechanical
interlock that may form a weak joint, and moreover, may exhibit low
process capability and repeatability.
[0029] Referring to FIG. 4B, a bottom view of button 60 from FIG.
4A is shown. Button 60 is fractured and shows cracks or paths for
moisture egress thereby making the materials of the joint
susceptible to corrosion or premature failure. The type of failure
shown in FIGS. 4A and 4B are also not reproducible and therefore
the early failure cannot be accommodated for by design. As shown in
FIGS. 4A and 4B, the fractures and/or cracks 61 in button 60
penetrate such that a portion or region of the aluminum component
48 and SPR 52 are exposed. Such exposure makes aluminum component
48 and SPR 52 susceptible to corrosion and/or premature failure.
This result exhibits unacceptable button cracking While the
asymmetrical interlock may be addressed by using a different rivet
material, unacceptable button cracking cannot be addressed by using
a different material. Rather, the hot riveting method of one or
more embodiments satisfactorily provides a resulting joint with
acceptable button properties, as described below in reference to
FIGS. 5A and 5B.
[0030] FIG. 5A is a cross-sectional view of an aluminum component
62 joined to a carbon fiber composite material component 64 using
an SPR technique at an elevated temperature. In the embodiment
shown, the carbon fiber composite material component 64 was heated
to a temperature of between 180 to 210.degree. C. prior to joining
it with the aluminum component 62. SPR 66 includes head 68 and
shaft 70. Region 74 of the joint shown in FIG. 5A is a void between
SPR 66 of aluminum component 62. SPR 66 extends into both the
carbon fiber composite panel 64 and the aluminum panel 62. Shaft 70
extends into carbon fiber composite material component 64 an
orthogonal horizontal distance from intersection region 76 of
components 62 and 64 and SPR 66. Distance d.sub.1 on the left
cross-section of shaft 70 is about 0.19 mm and the distance d.sub.2
on the right cross-section of shaft 70 is about 0.16 mm. As shown,
there is minimal variation in the distance d.sub.1 and d.sub.2.
Joints formed with SPRs exhibiting sufficient interlock and showing
this minimal variation form a strong and durable joint. The
enhanced ductility and material flow accomplished by heating carbon
fiber composite material component 64 to an elevated temperature
results in adequate interlock between components 62 and 64,
symmetry of the shaft 70 and reduced cracking of the button 72 of
FIGS. 5A and 5B. As shown in FIGS. 5A and 5B, the fractures and/or
cracks 78 do not penetrate such that a portion or region of the
aluminum component 62 or SPR 66 is exposed. Such unexposed surfaces
reduce the susceptibility of aluminum component 62 or SPR 66 to
corrosion or premature failure, and provide a repeatable and
consistent solution to the unacceptable button cracking described
above.
[0031] While exemplary embodiments are described above, it is not
intended that these embodiments describe all possible forms of the
invention. Rather, the words used in the specification are words of
description rather than limitation, and it is understood that
various changes may be made without departing from the spirit and
scope of the invention. Additionally, the features of various
implementing embodiments may be combined to form further
embodiments of the invention.
* * * * *