U.S. patent application number 15/605224 was filed with the patent office on 2017-12-14 for ultrasonic weld-bonding of thermoplastic composites.
This patent application is currently assigned to GM Global Technology Operations LLC. The applicant listed for this patent is GM Global Technology Operations LLC. Invention is credited to Bradley J. Blaski, Pei-chung Wang.
Application Number | 20170355150 15/605224 |
Document ID | / |
Family ID | 60573584 |
Filed Date | 2017-12-14 |
United States Patent
Application |
20170355150 |
Kind Code |
A1 |
Wang; Pei-chung ; et
al. |
December 14, 2017 |
ULTRASONIC WELD-BONDING OF THERMOPLASTIC COMPOSITES
Abstract
Methods for ultrasonic welding of thermoplastic polymer
workpieces and assemblies made therefrom are provided. The method
may comprise disposing a first region of a first thermoplastic
polymer workpiece and a second region of a second thermoplastic
polymer workpiece between an ultrasonic horn and an anvil of an
ultrasonic welding device. The first workpiece has a preformed
deformation and at least one of the first and/or second workpieces
has an adhesive precursor applied thereto. The ultrasonic horn or
anvil seats within the preformed deformation. Ultrasonic energy is
applied from the ultrasonic horn to create a weld nugget between
the first and second workpieces. The assembly thus formed has a
green strength sufficient to be further processed immediately. The
methods provide a robust weld joint with controlled adhesive
bondline thickness.
Inventors: |
Wang; Pei-chung; (Troy,
MI) ; Blaski; Bradley J.; (Sterling Heights,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM Global Technology Operations LLC |
Detroit |
MI |
US |
|
|
Assignee: |
GM Global Technology Operations
LLC
Detroit
MI
|
Family ID: |
60573584 |
Appl. No.: |
15/605224 |
Filed: |
May 25, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62349845 |
Jun 14, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 66/1122 20130101;
B29C 66/8322 20130101; B29C 65/7855 20130101; B29C 66/472 20130101;
B29C 65/08 20130101; B29C 65/72 20130101; B29C 66/73921 20130101;
B29C 65/483 20130101; B29C 66/71 20130101; B29C 66/30221 20130101;
B29C 65/7829 20130101; B29C 66/7212 20130101; B29L 2031/30
20130101; B29L 2031/7172 20130101; B29C 66/81422 20130101 |
International
Class: |
B29C 65/08 20060101
B29C065/08; B29C 65/48 20060101 B29C065/48 |
Claims
1. A method for ultrasonic welding of polymeric workpieces, the
method comprising: disposing a first region of a first
thermoplastic polymer workpiece and a second region of a second
thermoplastic polymer workpiece between an ultrasonic horn and an
anvil of an ultrasonic welding device, wherein the first
thermoplastic polymer workpiece has a preformed deformation in the
first region and at least one of the first thermoplastic polymer
workpiece and the second thermoplastic polymer workpiece has an
adhesive precursor applied thereto, wherein at least one of the
ultrasonic horn or the anvil seats within the preformed deformation
to provide a predetermined bondline between the first thermoplastic
polymer workpiece and the second thermoplastic polymer workpiece;
and applying ultrasonic energy from the ultrasonic horn to create a
weld nugget between the first thermoplastic polymer workpiece and
the second thermoplastic polymer workpiece, wherein an assembly of
the first thermoplastic polymer workpiece and the second
thermoplastic polymer workpiece having the weld nugget has a green
strength so that the assembly can be further processed
immediately.
2. The method of claim 1, further comprising oscillating the first
thermoplastic polymer workpiece and the second thermoplastic
polymer workpiece at a frequency of greater than or equal to about
15 KHz to less than or equal to about 40 KHz.
3. The method of claim 1, wherein the deformation has a depth of
greater than or equal to about 0.5 mm and less than or equal to
about 3 mm and a diameter or width of greater than or equal to
about 7 mm and less than or equal to about 20 mm.
4. The method of claim 1, wherein the deformation has a
cross-sectional shape that corresponds to a cross-sectional shape
of the ultrasonic horn and the method further comprises seating the
ultrasonic horn in the deformation during the disposing.
5. The method of claim 4, wherein the deformation has a round or
oval cross-sectional shape.
6. The method of claim 1, wherein the weld nugget has a diameter of
greater than or equal to about 3 mm and less than or equal to about
18 mm.
7. The method of claim 1, wherein the first thermoplastic polymer
workpiece and the second thermoplastic polymer workpiece each
independently has a thickness of greater than or equal to about 0.5
mm to less than or equal to about 5 mm.
8. The method of claim 1, wherein the predetermined bondline where
the adhesive is formed between the first thermoplastic polymer
workpiece and the second thermoplastic polymer workpiece has an
average thickness of greater than or equal to about 0.25 mm to less
than or equal to about 1.25 mm.
9. The method of claim 1, wherein the first thermoplastic polymer
workpiece and the second thermoplastic polymer workpiece are a
composite material comprising: a thermoplastic polymer formed from
a material independently selected from the group consisting of:
polyamide resin, polystyrene resin, acrylonitrile styrene resin,
acrylonitrile-butadiene-styrene resin, polyvinyl alcohol resin,
vinyl chloride resin, vinylidene chloride resin, vinyl acetate
resin, acrylic resin, polyacrylate resin, methacrylate resin,
polypropylene resin, polyethylene resin, polycarbonate resin,
polyacetal resin, polylactide resin, polyethylene terephthalate
resin, polyethylene naphthalate resin, polybutylene terephthalate
resin, polyphenylene ether resin, polyphenylene sulfide resin,
polysulfone resin, polyether sulfone resin, polyether ether ketone
resin, copolymers, and combinations thereof; and a reinforcement
material selected from the group consisting of: carbon fibers,
glass fibers, carbon black particles, and combinations thereof.
10. The method of claim 1, wherein the adhesive precursor forms an
adhesive selected from the group: acrylates, methacrylates,
epoxies, copolymers, and combinations thereof.
11. The method of claim 1, wherein the assembly is transferred to
at least one downstream processing station and after processing in
the downstream processing station, the adhesive precursor is
permitted to react and form the adhesive at ambient conditions.
12. The method of claim 1, wherein the first thermoplastic polymer
workpiece further comprises a plurality of energy director features
in the preformed deformation that are capable of focusing the
ultrasonic energy as it is applied to initiate heating in the first
region.
13. An assembly comprising: a first thermoplastic polymer workpiece
having has a preformed deformation in a first region; a second
thermoplastic polymer workpiece; an adhesive disposed between the
first thermoplastic polymer workpiece and the second thermoplastic
polymer workpiece that defines a predetermined bondline having an
average thickness of greater than or equal to about 0.25 mm to less
than or equal to about 1.25 mm; and a weld nugget formed between
the second thermoplastic polymer workpiece and the first
thermoplastic polymer workpiece in a region corresponding to the
preformed deformation.
14. The assembly of claim 13, wherein the deformation has a depth
of greater than or equal to about 0.5 mm and less than or equal to
about 3 mm and a diameter or width of greater than or equal to
about 7 mm and less than or equal to about 20 mm.
15. The assembly of claim 13, wherein the deformation has a round
or oval cross-sectional shape.
16. The assembly of claim 13, wherein the weld nugget has a
diameter of greater than or equal to about 3 mm and less than or
equal to about 18 mm.
17. The assembly of claim 13, wherein the first thermoplastic
polymer workpiece and the second thermoplastic polymer workpiece
each independently has a thickness of greater than or equal to
about 0.5 mm to less than or equal to about 5 mm.
18. The assembly of claim 13, wherein the first thermoplastic
polymer workpiece and the second thermoplastic polymer workpiece
are a composite material comprising: a thermoplastic polymer formed
from a material independently selected from the group consisting
of: polyamide resin, polystyrene resin, acrylonitrile styrene
resin, acrylonitrile-butadiene-styrene resin, polyvinyl alcohol
resin, vinyl chloride resin, vinylidene chloride resin, vinyl
acetate resin, acrylic resin, polyacrylate resin, methacrylate
resin, polypropylene resin, polyethylene resin, polycarbonate
resin, polyacetal resin, polylactide resin, polyethylene
terephthalate resin, polyethylene naphthalate resin, polybutylene
terephthalate resin, polyphenylene ether resin, polyphenylene
sulfide resin, polysulfone resin, polyether sulfone resin,
polyether ether ketone resin, copolymers, and combinations thereof;
and a reinforcement material selected from the group consisting of:
carbon fibers, glass fibers, carbon black particles, and
combinations thereof.
19. The assembly of claim 13, wherein the adhesive is selected from
the group: acrylates, methacrylates, epoxies, and copolymers and
combinations thereof.
20. The assembly of claim 13, wherein the preformed deformation in
the first region further comprises a plurality of energy director
features.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/349,845 filed on Jun. 14, 2016. The entire
disclosure of the above application is incorporated herein by
reference.
FIELD
[0002] The present disclosure relates to new methods and systems
for improved ultrasonic weld-bonding of thermoplastic polymeric
materials.
BACKGROUND
[0003] This section provides background information related to the
present disclosure which is not necessarily prior art.
[0004] In a vibration welding process, such as ultrasonic welding,
adjacent surfaces of a workpiece or multiple workpieces are joined
together by applying vibrational energy. For example, two or more
workpieces may be joined together, while calibrated vibrational
energy is transmitted from an ultrasonic welder through at least
one of the workpieces. The vibration creates surface friction along
interfacing surfaces and internal friction of the workpieces. Where
the workpieces are formed of a polymeric or plastic material, the
resultant heat softens the interfacing surfaces, and thus fuses or
bonds the workpieces by forming a weld nugget between the
workpieces.
[0005] In current ultrasonic welding techniques for polymeric
materials, an adhesive is applied between the workpieces that
requires curing or cross-linking after the formation of ultrasonic
energy. Pressure is applied during the ultrasonic welding process
(between the ultrasonic horn and anvil) that forces the adhesive to
migrate outside of the welded region where the weld nugget is
formed. The process of forming the weld nugget via ultrasonic
welding therefore causes undesirable variation in bond line
thicknesses and joint strengths. Further, the post-welding curing
must be done to provide sufficient strength between the workpieces
before further processing of the workpieces can proceed in an
assembly line, for example, heating the workpieces for at least 10
minutes (e.g., at 100.degree. C.) or longer. Typically, such curing
is done in a furnace or by other techniques that apply heat to the
polymeric workpieces. Thus, not only does the post-welding curing
process take considerable cycle time, but the heating process can
ultimately weaken the workpieces. It would be desirable to have a
new method of ultrasonic welding of polymeric materials that
minimizes cycle time during assembly, but also improves control
over the bond line formed between workpieces.
SUMMARY
[0006] This section provides a general summary of the disclosure,
and is not a comprehensive disclosure of its full scope or all of
its features.
[0007] In various aspects, the present disclosure provides a method
for ultrasonic welding of polymeric workpieces. In one aspect, the
method may include disposing a first region of a first
thermoplastic polymer workpiece and a second region of a second
thermoplastic polymer workpiece between an ultrasonic horn and an
anvil of an ultrasonic welding device. The first thermoplastic
polymer workpiece has a preformed deformation in the first region.
Further, at least one of the first thermoplastic polymer workpiece
and the second thermoplastic polymer workpiece has an adhesive
precursor applied thereto. At least one of the ultrasonic horn or
the anvil seats within the preformed deformation to provide a
predetermined bondline between the first thermoplastic polymer
workpiece and the second thermoplastic polymer workpiece. The
method further includes applying ultrasonic energy from the
ultrasonic horn to create a weld nugget between the first
thermoplastic polymer workpiece and the second thermoplastic
polymer workpiece. An assembly of the first thermoplastic polymer
workpiece and the second thermoplastic polymer workpiece having the
weld nugget is thus formed that has a green strength so that the
assembly can be further processed immediately.
[0008] In one aspect, the method further includes oscillating the
first thermoplastic polymer workpiece and the second thermoplastic
polymer workpiece at a frequency of greater than or equal to about
15 KHz to less than or equal to about 40 KHz.
[0009] In one aspect, the deformation has a depth of greater than
or equal to about 0.5 mm and less than or equal to about 3 mm and a
diameter or width of greater than or equal to about 7 mm and less
than or equal to about 20 mm.
[0010] In one aspect, the deformation has a cross-sectional shape
that corresponds to a cross-sectional shape of the ultrasonic horn
and the method further includes seating the ultrasonic horn in the
deformation during the disposing.
[0011] In one aspect, the deformation has a round or oval
cross-sectional shape.
[0012] In one aspect, the weld nugget has a diameter of greater
than or equal to about 3 mm and less than or equal to about 18
mm.
[0013] In one aspect, the first thermoplastic polymer workpiece and
the second thermoplastic polymer workpiece each independently has a
thickness of greater than or equal to about 0.5 mm to less than or
equal to about 5 mm.
[0014] In one aspect, the predetermined bondline where the adhesive
is formed between the first thermoplastic polymer workpiece and the
second thermoplastic polymer workpiece has an average thickness of
greater than or equal to about 0.25 mm to less than or equal to
about 1.25 mm.
[0015] In one aspect, the first thermoplastic polymer workpiece and
the second thermoplastic polymer workpiece are a composite material
including: a thermoplastic polymer formed from a material
independently selected from the group consisting of: polyamide
resin, polystyrene resin, acrylonitrile styrene resin,
acrylonitrile-butadiene-styrene resin, polyvinyl alcohol resin,
vinyl chloride resin, vinylidene chloride resin, vinyl acetate
resin, acrylic resin, polyacrylate resin, methacrylate resin,
polypropylene resin, polyethylene resin, polycarbonate resin,
polyacetal resin, polylactide resin, polyethylene terephthalate
resin, polyethylene naphthalate resin, polybutylene terephthalate
resin, polyphenylene ether resin, polyphenylene sulfide resin,
polysulfone resin, polyether sulfone resin, polyether ether ketone
resin, copolymers, and combinations thereof; and a reinforcement
material selected from the group consisting of: carbon fibers,
glass fibers, carbon black particles, and combinations thereof.
[0016] In one aspect, the adhesive precursor forms an adhesive
selected from the group: acrylates, methacrylates, epoxies, and
copolymers and combinations thereof.
[0017] In one aspect, the method further includes transferring the
assembly to at least one downstream processing station and after
processing in the downstream processing station, the adhesive
precursor is permitted to react and form the adhesive at ambient
conditions.
[0018] In one aspect, the first thermoplastic polymer workpiece
further includes a plurality of energy director features in the
preformed deformation that are capable of focusing the ultrasonic
energy as it is applied to initiate heating in the first
region.
[0019] In one further aspect, a region around the weld nugget is
substantially free of any ghost welds.
[0020] In other aspects, the present disclosure provides an
assembly that includes a first thermoplastic polymer workpiece
having has a preformed deformation in a first region and a second
thermoplastic polymer workpiece. The assembly further includes an
adhesive disposed between the first thermoplastic polymer workpiece
and the second thermoplastic polymer workpiece that defines a
predetermined bondline having an average thickness of greater than
or equal to about 0.25 mm to less than or equal to about 1.25 mm.
The assembly also includes a weld nugget formed between the second
thermoplastic polymer workpiece and the first thermoplastic polymer
workpiece in a region corresponding to the preformed
deformation.
[0021] In one aspect, the deformation has a depth of greater than
or equal to about 0.5 mm and less than or equal to about 3 mm and a
diameter or width of greater than or equal to about 7 mm and less
than or equal to about 20 mm.
[0022] In one aspect, the deformation has a round or oval
cross-sectional shape.
[0023] In one aspect, the weld nugget has a diameter of greater
than or equal to about 3 mm and less than or equal to about 18
mm.
[0024] In one aspect, the first thermoplastic polymer workpiece and
the second thermoplastic polymer workpiece each independently has a
thickness of greater than or equal to about 0.5 mm to less than or
equal to about 5 mm.
[0025] In one aspect, the first thermoplastic polymer workpiece and
the second thermoplastic polymer workpiece are a composite material
including: a thermoplastic polymer formed from a material
independently selected from the group consisting of: polyamide
resin, polystyrene resin, acrylonitrile styrene resin,
acrylonitrile-butadiene-styrene resin, polyvinyl alcohol resin,
vinyl chloride resin, vinylidene chloride resin, vinyl acetate
resin, acrylic resin, polyacrylate resin, methacrylate resin,
polypropylene resin, polyethylene resin, polycarbonate resin,
polyacetal resin, polylactide resin, polyethylene terephthalate
resin, polyethylene naphthalate resin, polybutylene terephthalate
resin, polyphenylene ether resin, polyphenylene sulfide resin,
polysulfone resin, polyether sulfone resin, polyether ether ketone
resin, copolymers, and combinations thereof; and a reinforcement
material selected from the group consisting of: carbon fibers,
glass fibers, carbon black particles, and combinations thereof.
[0026] In one aspect, the adhesive is selected from the group:
acrylates, methacrylates, epoxies, copolymers, and combinations
thereof.
[0027] In one aspect, the preformed deformation in the first region
further includes a plurality of energy director features.
[0028] In one further aspect, a region around the weld nugget is
substantially free of any ghost welds.
[0029] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
DRAWINGS
[0030] The drawings described herein are for illustrative purposes
only of selected embodiments and not all possible implementations,
and are not intended to limit the scope of the present
disclosure.
[0031] FIG. 1 shows a schematic of a system for ultrasonic bonding
of polymeric materials;
[0032] FIG. 2 shows a schematic of two polymeric workpieces to be
joined having an applied adhesive precursor, where one workpiece
has a protruding preformed deformation in accordance with various
aspects of the present disclosure;
[0033] FIG. 3 shows a schematic where the two polymeric workpieces
in FIG. 2 are disposed between an ultrasonic horn and an anvil in
an ultrasonic welding apparatus in accordance with various aspects
of the present disclosure; and
[0034] FIG. 4 shows a schematic of an assembly after ultrasonic
welding of two polymeric workpieces joined with a weld nugget and
an adhesive in accordance with various aspects of the present
disclosure.
[0035] FIG. 5 shows a schematic of two polymeric workpieces to be
joined having an applied adhesive precursor, where one workpiece
has a protruding preformed deformation including an energy director
layer defining a plurality of energy directors in accordance with
certain aspects of the present disclosure.
[0036] FIG. 6 shows a schematic of an assembly after ultrasonic
welding of the two polymeric workpieces in FIG. 5 joined with a
weld nugget formed at least in part from the energy director layer
and an adhesive in accordance with various aspects of the present
disclosure.
[0037] FIG. 7 shows a magnified image (50 times magnification) of a
fractured surface of an overlap region of two welded polymeric
workpieces having ghost welds formed therein.
[0038] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION
[0039] Example embodiments are provided so that this disclosure
will be thorough, and will fully convey the scope to those who are
skilled in the art. Numerous specific details are set forth such as
examples of specific compositions, components, devices, and
methods, to provide a thorough understanding of embodiments of the
present disclosure. It will be apparent to those skilled in the art
that specific details need not be employed, that example
embodiments may be embodied in many different forms and that
neither should be construed to limit the scope of the disclosure.
In some example embodiments, well-known processes, well-known
device structures, and well-known technologies are not described in
detail.
[0040] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting. As used herein, the singular forms "a," "an," and "the"
may be intended to include the plural forms as well, unless the
context clearly indicates otherwise. The terms "comprises,"
"comprising," "including," and "having," are inclusive and
therefore specify the presence of stated features, elements,
compositions, steps, integers, operations, and/or components, but
do not preclude the presence or addition of one or more other
features, integers, steps, operations, elements, components, and/or
groups thereof. Although the open-ended term "comprising," is to be
understood as a non-restrictive term used to describe and claim
various embodiments set forth herein, in certain aspects, the term
may alternatively be understood to instead be a more limiting and
restrictive term, such as "consisting of" or "consisting
essentially of." Thus, for any given embodiment reciting
compositions, materials, components, elements, features, integers,
operations, and/or process steps, the present disclosure also
specifically includes embodiments consisting of, or consisting
essentially of, such recited compositions, materials, components,
elements, features, integers, operations, and/or process steps. In
the case of "consisting of," the alternative embodiment excludes
any additional compositions, materials, components, elements,
features, integers, operations, and/or process steps, while in the
case of "consisting essentially of," any additional compositions,
materials, components, elements, features, integers, operations,
and/or process steps that materially affect the basic and novel
characteristics are excluded from such an embodiment, but any
compositions, materials, components, elements, features, integers,
operations, and/or process steps that do not materially affect the
basic and novel characteristics can be included in the
embodiment.
[0041] Any method steps, processes, and operations described herein
are not to be construed as necessarily requiring their performance
in the particular order discussed or illustrated, unless
specifically identified as an order of performance. It is also to
be understood that additional or alternative steps may be employed,
unless otherwise indicated.
[0042] When a component, element, or layer is referred to as being
"on," "engaged to," "connected to," or "coupled to" another element
or layer, it may be directly on, engaged, connected or coupled to
the other component, element, or layer, or intervening elements or
layers may be present. In contrast, when an element is referred to
as being "directly on," "directly engaged to," "directly connected
to," or "directly coupled to" another element or layer, there may
be no intervening elements or layers present. Other words used to
describe the relationship between elements should be interpreted in
a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the
term "and/or" includes any and all combinations of one or more of
the associated listed items.
[0043] Although the terms first, second, third, etc. may be used
herein to describe various steps, elements, components, regions,
layers and/or sections, these steps, elements, components, regions,
layers and/or sections should not be limited by these terms, unless
otherwise indicated. These terms may be only used to distinguish
one step, element, component, region, layer or section from another
step, element, component, region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. Thus, a first step, element, component, region, layer or
section discussed below could be termed a second step, element,
component, region, layer or section without departing from the
teachings of the example embodiments.
[0044] Spatially or temporally relative terms, such as "before,"
"after," "inner," "outer," "beneath," "below," "lower," "above,"
"upper," and the like, may be used herein for ease of description
to describe one element or feature's relationship to another
element(s) or feature(s) as illustrated in the figures. Spatially
or temporally relative terms may be intended to encompass different
orientations of the device or system in use or operation in
addition to the orientation depicted in the figures.
[0045] Throughout this disclosure, the numerical values represent
approximate measures or limits to ranges to encompass minor
deviations from the given values and embodiments having about the
value mentioned as well as those having exactly the value
mentioned. Other than in the working examples provided at the end
of the detailed description, all numerical values of parameters
(e.g., of quantities or conditions) in this specification,
including the appended claims, are to be understood as being
modified in all instances by the term "about" whether or not
"about" actually appears before the numerical value. "About"
indicates that the stated numerical value allows some slight
imprecision (with some approach to exactness in the value;
approximately or reasonably close to the value; nearly). If the
imprecision provided by "about" is not otherwise understood in the
art with this ordinary meaning, then "about" as used herein
indicates at least variations that may arise from ordinary methods
of measuring and using such parameters. For example, "about" may
comprise a variation of less than or equal to 5%, optionally less
than or equal to 4%, optionally less than or equal to 3%,
optionally less than or equal to 2%, optionally less than or equal
to 1%, optionally less than or equal to 0.5%, and in certain
aspects, optionally less than or equal to 0.1%.
[0046] In addition, disclosure of ranges includes disclosure of all
values and further divided ranges within the entire range,
including endpoints and sub-ranges given for the ranges.
[0047] Example embodiments will now be described more fully with
reference to the accompanying drawings.
[0048] As noted above, in a vibration welding process like
ultrasonic welding, adjacent surfaces of a workpiece or multiple
workpieces are joined together by applying ultrasonic energy or
vibrational energy to the workpiece. An exemplary and simplified
conventional ultrasonic welding device 20 is shown in FIG. 1. A
first polymeric workpiece 30 comprises a polymer, such as a
thermoplastic polymer, and has a planar or flat shape in a region
to be welded. A second polymeric workpiece 32 likewise comprises a
polymer, like a thermoplastic polymer, and also has a planar or
flat shape in the region where it will be welded. An adhesive
precursor 34 is applied between the first polymeric workpiece 30
and the second polymeric workpiece 32.
[0049] As shown, the first polymeric workpiece 30 and the second
polymeric workpiece 32 are clamped together between an ultrasonic
horn 40 and an anvil 42 on an opposite side. Thus, the ultrasonic
horn 40 contacts the first polymeric workpiece 30, while the anvil
42 contacts the second polymeric workpiece 32. The ultrasonic horn
40 is also known as a sonotrode and together with an affiliated
ultrasonic transducer vibrates when energized and generates
ultrasonic energy that is transmitted through the first polymeric
workpiece 30 to the second polymeric workpiece 32. The anvil 42 may
be formed of a relatively large piece of metal having sufficient
rigidity for opposing the ultrasonic horn 40. Together the
ultrasonic horn 40 and anvil 42 define a welder body of a welding
apparatus. While not shown, the ultrasonic horn 40 and/or the anvil
42 may include welding pads and other welding system
components.
[0050] A downward arrow indicates a direction that pressure is
applied to the first polymeric workpiece 30 and the second
polymeric workpiece 32 when the ultrasonic horn 40 is brought into
contact with the first polymeric workpiece 30. A double-sided arrow
shows vibrational oscillation of the workpieces 30, 32. The
vibrational energy from the ultrasonic horn 40 creates surface
friction along interfacing surfaces of the first polymeric
workpiece 30 and the second polymeric workpiece 32 and internal
friction of the workpieces 30 and 32. The resultant heat softens
the interfacing surfaces, thus bonding the first polymeric
workpiece 30 and the second polymeric workpiece 32 to form a weld
nugget 50. A bondline 52 is defined where the adhesive is present
(after the adhesive precursor 34 is cured) between the first
polymeric workpiece 30 and the second polymeric workpiece 32.
[0051] In a conventional ultrasonic welding process like that shown
in FIG. 1, the pressure that is applied between the ultrasonic horn
40 and anvil 42 during welding (either by clamping and/or through
application of ultrasonic energy) causes the adhesive precursor 34
between the first polymeric workpiece 30 and the second polymeric
workpiece 32 to be forced away from the site or region where the
weld nugget 50 is formed. Thus, the adhesive precursor 34 is pushed
away from the region of the weld nugget 50 and thinned out or
removed as it extends outwards. In this manner, the adhesive
precursor 34 spreads outward in an undesirable and uncontrolled
manner and results in an unpredictable or uneven bondline in the
cured adhesive in the region in and around the weld nugget 50. The
uneven bondline can cause variable strength in the bond.
[0052] In conventional processes, after the ultrasonic welding is
conducted, the assembly is further treated to cure/react the
adhesive precursor to provide sufficient green strength of the
adhesive bond for additional processing. Thus, after welding, in a
conventional process the assembly is transferred to a furnace for a
set amount of time (e.g., a furnace at 100.degree. C. for 10
minutes) or is allowed to cure or react for longer periods at
ambient conditions (e.g., for 24 hours). This curing/reaction time
slows processing and cycle time considerably. Furthermore, the heat
from the welding process can also degrade the adhesive precursor
34, especially where it is thinnest, and thus can diminish the
strength of the weld-bonded polymeric composite assembly that is
formed.
[0053] The present disclosure contemplates a new method of
ultrasonic welding polymeric workpieces together. It should be
noted that while two workpieces are discussed, the concepts in the
present disclosure are equally applicable to a single workpiece
that is being joined at different regions or to multiple workpieces
(e.g., three of more) being joined together. At least one of the
first thermoplastic polymer workpiece and the second thermoplastic
polymer workpiece has an adhesive precursor applied thereto. With
reference to FIG. 2, a first workpiece 60 comprising a first
thermoplastic polymer and a second workpiece 62 comprising a second
thermoplastic polymer are to be joined. The first and second
thermoplastic polymers may be the same or distinct from one
another. Thermoplastic polymers are capable of softening under
frictional heat (e.g., surface friction) between the workpieces and
vibration from ultrasonic energy to form a fused bond. The
thermoplastic polymer may be formed from any suitable kind of
thermoplastic resin. By way of non-limiting example, the
thermoplastic polymer may include: nylons or polyamide resins
(nylon 6, nylon 11, nylon 12, nylon 46, nylon 66, nylon 610),
polystyrene resin, acrylonitrile styrene resin,
acrylonitrile-butadiene-styrene resin, polyvinyl alcohol resin,
vinyl chloride resin, vinylidene chloride resin, vinyl acetate
resin, acrylic resin, polyacrylate resin, methacrylate resin,
polypropylene resin, polyethylene resin, polycarbonate resin,
polyacetal resin, polylactide resin, polyethylene terephthalate
resin, polyethylene naphthalate resin, polybutylene terephthalate
resin, polyphenylene ether resin, polyphenylene sulfide resin,
polysulfone resin, polyether sulfone resin, polyether ether ketone
resin, copolymers, and combinations thereof.
[0054] In certain aspects, the first workpiece 60 comprising a
first thermoplastic polymer and/or the second workpiece 62
comprising a second thermoplastic polymer may be a polymeric
composite material that comprises a thermoplastic polymer matrix
and a reinforcement material, such as a plurality of reinforcing
particles or fibers distributed therein. In certain aspects, a
polymeric composite may include a plurality of carbon fibers, glass
fibers, or carbon black, as the reinforcement material, by way of
non-limiting example. The plurality of reinforcing particles or
fibers may be included at greater than or equal to about 5 weight %
to less than or equal to about 90 weight % of the total composite,
and in certain variations, optionally at greater than or equal to
about 15 weight % to less than or equal to about 60 weight %. In
one example, a suitable polymeric composite structure for a
workpiece may be a thermoplastic carbon fiber reinforced
composite.
[0055] In certain aspects, the first thermoplastic polymer
workpiece and the second thermoplastic polymer workpiece are a
composite material each independently comprising a thermoplastic
polymer formed from a material selected from the group consisting
of: polyamide resin, polystyrene resin, acrylonitrile styrene
resin, acrylonitrile-butadiene-styrene resin, polyvinyl alcohol
resin, vinyl chloride resin, vinylidene chloride resin, vinyl
acetate resin, acrylic resin, polyacrylate resin, methacrylate
resin, polypropylene resin, polyethylene resin, polycarbonate
resin, polyacetal resin, polylactide resin, polyethylene
terephthalate resin, polyethylene naphthalate resin, polybutylene
terephthalate resin, polyphenylene ether resin, polyphenylene
sulfide resin, polysulfone resin, polyether sulfone resin,
polyether ether ketone resin, copolymers, and combinations thereof
and a reinforcement material selected from the group consisting of:
carbon fibers, glass fibers, carbon black particles, and
combinations thereof.
[0056] In certain aspects, the first thermoplastic polymer
workpiece and the second thermoplastic polymer workpiece are
composite materials that independently comprise a polyamide
thermoplastic polymer and a reinforcement material selected from
the group consisting of: carbon fibers, glass fibers, carbon black
particles, and combinations thereof.
[0057] In one non-limiting variation, the thermoplastic composite
may be nylon 6 having about 30 weight % carbon fiber distributed
therein. Such thermoplastic composite materials may be manufactured
from a compression molding process or an injection molding
process.
[0058] With renewed reference to FIG. 2, the second workpiece 62
has an adhesive precursor 64 applied to a surface 66. It should be
noted that the adhesive precursor 64 may be applied continuously or
alternatively to select regions of the surface 66. In certain
aspects, as will be described further below, the adhesive precursor
forms an adhesive selected from the group: acrylates,
methacrylates, epoxies, copolymers, and combinations thereof, by
way of example.
[0059] The first workpiece 60 has at least one preformed protrusion
or deformation 70 in a region where the welding will occur to join
the first workpiece 60 to the second workpiece 62. While only one
preformed deformation 70 is shown, where workpieces having large
surface areas are to be joined and welded, multiple preformed
deformations may be present in the first workpiece 60 to provide
multiple sites for welding in accordance with certain aspects of
the present disclosure. Also, while not shown, the region to be
welded may occur at terminal edges of the first workpiece 60 and
the second workpiece 62. As noted above, such thermoplastic
materials may be manufactured from a compression molding process or
an injection molding process. In such processes, the die(s) (or
mold(s)) for forming the first workpiece 60 complement one another
to define one or more preformed deformation 70 during the
compression molding or injection molding process.
[0060] As shown in FIG. 3, in certain aspects, the method may
comprise disposing a first region 72 of the first workpiece 60 and
a second region 74 of the second workpiece 62 between an ultrasonic
horn 80 and an anvil 82. The ultrasonic horn 80 and anvil 82 form
part of an ultrasonic welding device known in the art (not shown).
At least one of the ultrasonic horn 80 or the anvil 82 seats within
the preformed deformation 70. As shown in FIG. 3, the ultrasonic
horn 80 is seated in the preformed deformation 70, but the
orientation of the anvil 82 and/or first workpiece 60 could be
reoriented so that the anvil 82 seats within the preformed
deformation 70. In certain aspects, the preformed deformation 70
has a cross-sectional shape that generally corresponds to a
cross-sectional shape of the ultrasonic horn and the method further
comprises seating the ultrasonic horn in the preformed deformation
70. For example, the preformed deformation 70 may have a round or
oval cross-sectional shape that corresponds to a round or oval
cross-sectional shape of the ultrasonic horn 80. Other shapes are
likewise contemplated for the preformed deformation 70 and
ultrasonic horn 80 (or anvil 82), such as rectangular or other
shapes.
[0061] In this manner, the first workpiece 60 contacts the second
workpiece 62 along the preformed deformation 70, so that the
protrusion enhances contact between the workpieces. The preformed
deformation 70 is dimensioned to control and provide a
predetermined bondline 84 thickness of adhesive (formed by reacting
or curing adhesive precursor 64) between the first workpiece 60 and
the second workpiece 62 in regions 86 outside the welding zone.
[0062] Next, the method includes applying ultrasonic energy from
the ultrasonic horn 80 to create a weld nugget 90 between the first
workpiece 60 and the second workpiece 62. The preformed deformation
70 protrudes and brings the ultrasonic horn 80 in closer proximity
to the opposing workpiece (here second workpiece 62) to form a
stronger or more desirable ultrasonic weld nugget 90 than where the
first workpiece 60 and second workpiece 62 are separated with
adhesive disposed therebetween. The weld nugget 90 may have a
diameter of greater than or equal to about 3 mm and less than or
equal to about 18 mm, in certain variations, the weld nugget 90 may
have a diameter of greater than or equal to about 5 mm to less than
or equal to about 18 mm. The preformed deformation 70 induces a
mixed-mode loading under a given remote loading so that the peel
strength of the joint can be improved. Further, the amount of
spread of the adhesive precursor 64 is desirably controlled in
accordance with certain aspects of the present disclosure so that
it does not extend beyond a terminal edge or flange 92 of the first
workpiece 60 to better control adhesive spread and bondline
thickness. Furthermore, the size of the preformed deformation 70
and ultrasound horn's 80 dimensions (e.g., diameter) can be
selected to minimize adhesive degradation at the edge of the flange
92. When ultrasonic energy is applied, the first workpiece 60 and
the second workpiece 62 may oscillate at a frequency of greater
than or equal to about 15 KHz to less than or equal to about 40
KHz, optionally greater than or equal to about 20 KHz to less than
or equal to about 30 KHz. The force squeezes the adhesive/adhesive
precursor 64 so that the ultrasonic waves can be transmitted
through the workpieces, and consequently the heat can be produced
at the faying interfaces of the workpieces 60, 62. In this manner,
a weld is produced in accordance with certain aspects of the
present teachings that minimizes the adhesive degradation by
tailoring a weld schedule of force from the ultrasonic horn over
time, where the force may be applied at the same levels, but more
rapidly than in a conventional welding process.
[0063] In this manner, a green assembly 94 is formed that includes
the first workpiece 60, second workpiece 62, weld nugget 90, and
the adhesive precursor 64. The green assembly 94 formed by such a
method has a green strength such that the assembly can be further
processed immediately, for example, in an assembly line. By
"immediately," it is meant that the green assembly 94 can be
transferred in less than or equal to about 30 seconds, optionally
less than or equal to about 20 seconds, optionally less than or
equal to about 10 seconds, optionally less than or equal to about 5
seconds, and in certain variations, optionally transferred within
about 1 second to about 5 seconds after the ultrasonic horn 80 and
anvil 82 are withdrawn and the welding process is complete. Thus,
the methods of certain aspects of the present disclosure may
further include transferring the green assembly 94 to at least one
downstream processing station in an assembly line production
process. In certain aspects, the weld schedule of time versus horn
force for the ultrasonic welder can be optimized to obtain a
desired green strength (e.g., strength to hold the workpieces/parts
together) while minimizing the adhesive degradation.
[0064] After all the processing is completed, the adhesive
precursor 64 is permitted to react or cure to form an adhesive at
ambient temperature and pressure conditions. For example, the
ambient temperature may be room temperature of about 20.degree. C.
(68.degree. F.) and ambient pressure may be about 101 kPa (1 atm).
In this manner, the curing can be delayed in comparison to
conventional assembly methods for plastic workpieces and thus, the
curing or heating station need not follow welding, so that
processing of the green assembly 94 may be conducted immediately
and far more rapidly, amounting to a decreased processing or cycle
time and well as decreased costs associated with tooling.
[0065] In this manner, a robust solution for joining parts opens up
new opportunities to use polymeric composites to achieve weight
reduction, performance and corrosion resistance improvement in
various applications, including in vehicles. The processes
according to certain aspects of the present disclosure provide
greater robustness of assemblies through improvement of the welding
process and part design. Polymeric composites are widely used in
vehicles, such as automobiles, motorcycles, boats, tractors, buses,
mobile homes, campers, and tanks, and their utilization will be
increasing in the future with efforts to further reduce vehicle
mass. Reinforced composites are particularly suitable for use in
components of an automobile or other vehicle (e.g., motorcycles,
boats), but may also be used in a variety of other industries and
applications, including aerospace components, industrial equipment
and machinery, farm equipment, heavy machinery, by way of
non-limiting example. For example, reinforced composites may be
used to form automotive structural components having contoured or
complex three-dimensional shapes. Non-limiting examples include gas
tank protection shields, underbody shields, structural panels, door
panels, interior floors, floor pans (e.g., of a cargo van), roofs,
exterior surfaces, storage areas, including glove boxes, console
boxes, trunks, trunk floors, truck beds, and the like.
[0066] In other aspects, the present disclosure provides an
assembly 100 in FIG. 4 comprising a first thermoplastic polymer
workpiece 102 having has a preformed deformation 104 in a first
region to be welded. The assembly 100 also includes a second
thermoplastic polymer workpiece 106, which may have a conventional
planar or flat surface 108 in the region to be joined. An adhesive
110 is disposed between the first thermoplastic polymer workpiece
102 and the second thermoplastic polymer workpiece 106. A thickness
of the bondline 112 of the adhesive 110 is shown. In certain
aspects, the adhesive 110 defines a predetermined bondline 112
having an average thickness of greater than or equal to about 0.25
mm to less than or equal to about 1.25 mm. The assembly 100 also
includes a weld nugget 114 formed between the second thermoplastic
polymer workpiece 106 and the first thermoplastic polymer workpiece
102 in a region corresponding to the preformed deformation 104. The
weld nugget 114 may be formed by the methods described above.
[0067] In certain aspects, the first thermoplastic polymer
workpiece 102 and the second thermoplastic polymer workpiece 106
each independently has a thickness of greater than or equal to
about 0.5 mm to less than or equal to about 5 mm. Notably, as shown
in FIG. 4, the first thermoplastic polymer workpiece 102 has a
distinct thickness from that of second thermoplastic polymer
workpiece 106, although in alternative variations, the thicknesses
may be the same. The preformed deformation 104 may have a depth 120
of greater than or equal to about 0.5 mm and less than or equal to
about 3 mm. The preformed deformation 104 may have a diameter (in
the case of a round or circular cross-section) or width 122 (e.g.,
a greatest dimension across the preformed deformation 104) of
greater than or equal to about 7 mm and less than or equal to about
20 mm. In certain aspects, the preformed deformation 104 has a
round or oval cross-sectional shape, although in alternative
variations, it may be rectangular or have other shapes.
[0068] The first thermoplastic polymer workpiece 102 and the second
thermoplastic polymer workpiece 106 can be any of the materials
described above. The adhesive 110 may be selected from the group:
acrylates, methacrylates, epoxies, copolymers, and combinations
thereof. Examples of suitable adhesives include methacrylate
adhesives, such as PLEXUS.RTM. MA300, PLEXUS.RTM. MA310,
PLEXUS.RTM. MA320, PLEXUS.RTM. MA425, PLEXUS.RTM. MA530, and
PLEXUS.RTM. MA830 all commercially available from ITW Plexus. An
example of another suitable adhesive is an epoxy commercially
available as HENKEL.TM. 5089. In certain preferred aspects, the
adhesive precursor may be one that has two parts that are mixed
around a ratio of 1:1 for ease of commercial production and
processing.
[0069] In yet another variation shown in FIG. 5, a first
thermoplastic polymer workpiece 130 and a second thermoplastic
polymer workpiece 132 are to be welded. An adhesive precursor 134
is disposed on a planar surface 136 of the second thermoplastic
polymer workpiece 132. The first thermoplastic polymer workpiece
130 has a preformed deformation 140 in a region to be welded. An
energy director layer 142 is formed on a contact side 144 of the
preformed deformation 140. In certain aspects, the energy director
layer 142 defines a plurality of energy director features 146. The
energy director features 146 have specific material properties that
promote localized heating and enhance the contact of the workpieces
together to form a localized and controlled weld therebetween. The
primary function of the energy director features 146 in the energy
director layer 142 is to concentrate applied ultrasonic energy to
rapidly initiate the heating and melting of the area at the faying
or contacting interfaces of the first and second thermoplastic
polymer workpieces 130, 132. The energy director layer 142 with the
plurality of energy director features 146 is shown on the contact
side 144 of the preformed deformation 140 of the first
thermoplastic polymer workpiece 130, but may instead be formed on
the second thermoplastic polymer workpiece 132 in alternative
variations. It should be noted that in alternative variations, the
energy director features 146 need not be formed as a continuous
layer as shown in FIG. 5, but may instead form discrete and
discontinuous features on the surface of the preformed deformation
140.
[0070] Each energy director feature 146 may be a raised triangular
bead of material molded onto one of the workpieces, although
alternative shapes are also contemplated, such as convex shaped
protrusions, like rounded protrusions, bumps, nubs, and the like.
The energy director layer 142 defining the plurality of energy
director features 146 may be formed in the same compression molding
process as the first thermoplastic polymer workpiece 130, where the
material is selectively disposed as a layer on the blank forming
the first thermoplastic polymer workpiece 130 or within select
regions of an appropriately shaped mold region. The energy director
layer 142 defining the energy director features 146 may be formed
of a polymeric material, such as a resin or composite comprising
one or more reinforcement materials. In certain aspects, the energy
director layer 142 may comprise a common resin or polymer as the
first thermoplastic polymer workpiece 130. The material properties
(fabricated during molding) of energy director features 146 can be
tailored to localize heat generation, which enhance the contact
between the first and second thermoplastic polymer workpieces 130,
132 when ultrasonic weld-bonding of thermoplastic composites.
[0071] For example, the resin or polymer in the energy director
layer 142 may melt or soften prior to the surrounding first
thermoplastic polymer workpiece 130. In certain variations, an
initial modulus of the material forming the energy director layer
142 is less than or equal to about 75% of a comparative modulus of
the material forming the first thermoplastic polymer workpiece 130
on which the energy director layer 142 is formed. For example,
where the first thermoplastic polymer workpiece 130 comprises a
carbon fiber reinforced nylon composite (for example, having about
30 weight % carbon fiber), the energy director layer 142 may be a
carbon fiber reinforced nylon composite having a lower carbon
content (<30 weight % carbon fiber), so that the initial modulus
is at least 75% less than that of the first thermoplastic polymer
workpiece 130.
[0072] The energy director layer 142 defining the plurality of
energy director features 146 may have an overall thickness 148
(from terminal ends of the energy director features 146 through and
to an opposite terminal surface of the energy director layer 142)
of greater than or equal to about 0.1 mm to less than or equal to
about 0.5 mm. Each energy director feature 146 may have a width
(e.g., along its base) of greater than or equal to about 0.1 mm to
less than or equal to about 0.5 mm and a height of greater than or
equal to about 0.1 mm to less than or equal to about 0.5 mm. The
height and density (e.g., placement pattern and density) of the
plurality of energy director features 146 on the energy director
layer 142 on the contact surface 144 of the first thermoplastic
polymer workpiece 130 improves weld growth and minimizes adhesive
degradation at the edge of a flange.
[0073] After welding, as shown in FIG. 6, an assembly 150 is formed
that includes the first thermoplastic polymer workpiece 130 welded
to the second thermoplastic polymer workpiece 132 via a weld nugget
160 in a region corresponding to the preformed deformation 140. The
weld nugget 160 includes a least a portion of the material that
forms the energy director layer 142 and material from the first
thermoplastic polymer workpiece 130 and/or the second thermoplastic
polymer workpiece 132. The weld nugget 160 may be formed by the
methods described above.
[0074] After polymerizing or curing, the adhesive precursor 134
forms an adhesive 162 that is disposed between the first
thermoplastic polymer workpiece 130 and the second thermoplastic
polymer workpiece 132, as previously described above. The adhesive
162 may extend further out laterally than the first thermoplastic
polymer workpiece 130. A thickness of the bondline 152 of the
adhesive 162 is shown. In certain aspects, the adhesive 162 defines
a predetermined bondline 152 as described above in the previous
embodiments, for example, having an average thickness of greater
than or equal to about 0.25 mm to less than or equal to about 1.25
mm.
[0075] FIG. 7 shows an overhead image of an ultrasonically welded
region between two terminal regions of respective thermoplastic
polymer workpieces where the surface is fractured. In the overlap
region between the two welded polymeric workpieces, the free
surfaces vibrate at an edge of overlap 176 during the ultrasonic
welding. In FIG. 7, an ultrasonic weld nugget 170 is formed.
Adhesive 172 is shown around the weld nugget 170. Heat from welding
can degrade the adhesive 172 properties, and consequently the
strength of the weld-bonded polymeric composite. It has been
discovered that for regions that experience excessive vibration and
heat (e.g., where terminal ends of polymeric workpieces overlap)
during ultrasonic welding, ghost welds 174 may appear outside of
the weld nugget 170. Ghost welds 174 thus damage the adhesive 172
and result in a local stress concentration, and consequently weaken
the bond strength of the adhesive 172. In various aspects, the
design including a workpiece having the energy director layer 142
with the plurality of energy director features 146, especially in
combination with a preformed deformation/protrusion in the region
to be welded, can serve to localize and direct ultrasonic energy
into the weld nugget 170, while minimizing or avoiding formation of
undesirable ghost welds 174. In certain variations, the region to
be welded may be substantially free of ghost welds outside of the
primary nugget. The term "substantially free" as referred to herein
means that the ghost welds external to the primary weld nugget are
absent to the extent that that physical properties and limitations
attendant with their presence (e.g., measurable weakening of
adhesive bond strength) are avoided. In this manner, material
properties, geometry and density of energy directors can serve to
improve the weld growth and minimize adhesive degradation at the
faying surfaces between workpieces being joined together. The
present disclosure thus provides ultrasonic weld-bonding with
improved robustness at the weld joint.
[0076] In one aspect, the present disclosure contemplates methods
of making a workpiece having an energy director layer with the
plurality of energy director features. First, a layer of resin or
polymeric material (e.g., 0.3 mm thick Nylon 6) can be added on
select regions of the surface of the polymeric blank or disposed
within the select regions of the mold. The mold may define a shape
for the workpiece that includes the preformed deformation and one
or more energy director features. The blank and resin/polymeric
material can be molded together in the mold, for example, in a
compression molding process, to form a protruded or deformed
region, which may have an energy director layer defining a
plurality of energy director features formed from the resin or
polymeric material. The energy director features may be those
described above. The plurality of energy director features may be
capable of focusing the ultrasonic energy as it is applied. The
energy director features may have specific material properties that
promote localized heating and enhance the contact of the workpieces
together. The preformed deformation or protrusion sets the bondline
thickness between the workpieces.
[0077] In other aspects, the present disclosure provides a method
for forming an assembly comprising a first thermoplastic polymer
workpiece having a preformed deformation and an energy director
layer with the plurality of energy director features in a first
region to be welded. The assembly also includes a second
thermoplastic polymer workpiece, which may have a planar or flat
surface including in the region to be joined. The first and second
thermoplastic polymer workpieces may be married together. The
preformed deformation having an energy director layer defining a
plurality of energy director features may have tailored material
properties (fabricated from compression molding). The resin or
polymer in the energy director layer promotes localized heating,
enhances the contact of the first and second thermoplastic polymer
workpieces. For example, the resin or polymer in the energy
director layer may melt or soften prior to the surrounding
workpiece materials to facilitate formation of the weld nugget in a
select and predetermined region.
[0078] An adhesive is disposed between the first thermoplastic
polymer workpiece and the second thermoplastic polymer workpiece,
which may be formed from an adhesive precursor. The preformed
deformation sets a bondline thickness between the first and second
thermoplastic polymer workpieces and thus a bondline thickness of
the adhesive. A thickness of the bondline of the adhesive may be in
the range described previously above. A weld nugget is produced
between the second thermoplastic polymer workpiece and the first
thermoplastic polymer workpiece in a region corresponding to the
preformed deformation and energy director layer defining the energy
director features via ultrasonic weld-bonding. The weld nugget may
be formed by the methods described above.
[0079] The energy director features, which may be located in the
preformed deformation, are capable of focusing the ultrasonic
energy as it is applied. In certain aspects, a weld is produced
while minimizing the adhesive degradation with an appropriate weld
schedule. For example, the welded region may be substantially free
of ghost welds external to the primary weld nugget. Further, by
adjusting the size of the preformed deformation and horn size (for
various flange widths), adhesive degradation at edge of the flange
and in the welded region can be minimized or prevented.
[0080] The foregoing description of the embodiments has been
provided for purposes of illustration and description. It is not
intended to be exhaustive or to limit the disclosure. Individual
elements or features of a particular embodiment are generally not
limited to that particular embodiment, but, where applicable, are
interchangeable and can be used in a selected embodiment, even if
not specifically shown or described. The same may also be varied in
many ways. Such variations are not to be regarded as a departure
from the disclosure, and all such modifications are intended to be
included within the scope of the disclosure.
* * * * *