U.S. patent application number 11/251337 was filed with the patent office on 2006-03-30 for laminate system for a durable controlled modulus flexible membrane.
This patent application is currently assigned to WARWICK MILLS, INC.. Invention is credited to Charles A. Howland.
Application Number | 20060068158 11/251337 |
Document ID | / |
Family ID | 23321771 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060068158 |
Kind Code |
A1 |
Howland; Charles A. |
March 30, 2006 |
Laminate system for a durable controlled modulus flexible
membrane
Abstract
A fabric system for producing at least a woven fabric of
controlled modulus or elongation in the MD or warp axis, has a core
layer which is the main structural element, and may have one or
more woven cover fabrics adhesively bonded with an off axis
configuration to one or both sides of the core layer. In a
preferred embodiment the core fabric is covered with at least one
off axis fabric on both sides. The cover fabrics may also have
resin or film top layers laminated or coated on their outside
surfaces, for mechanical performance or UV protection or both.
Inventors: |
Howland; Charles A.;
(Temple, NH) |
Correspondence
Address: |
MAINE & ASMUS
100 MAIN STREET
P O BOX 3445
NASHUA
NH
03061-3445
US
|
Assignee: |
WARWICK MILLS, INC.
New Ipswich
NH
|
Family ID: |
23321771 |
Appl. No.: |
11/251337 |
Filed: |
October 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10293828 |
Nov 13, 2002 |
6998165 |
|
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11251337 |
Oct 14, 2005 |
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60337732 |
Nov 13, 2001 |
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Current U.S.
Class: |
428/105 ;
428/109; 428/111; 428/113; 442/239; 442/261; 442/286 |
Current CPC
Class: |
Y10T 428/24107 20150115;
Y10T 428/24074 20150115; Y10T 442/3252 20150401; Y10T 428/24091
20150115; Y10T 442/322 20150401; Y10T 442/365 20150401; Y10T
428/24116 20150115; Y10T 442/3228 20150401; Y10T 428/24124
20150115; Y10T 442/3528 20150401; Y10T 442/3301 20150401; Y10T
442/3854 20150401; Y10T 428/24099 20150115; Y10T 428/24058
20150115; B63H 9/067 20200201; Y10T 442/3317 20150401; Y10T
442/3472 20150401; B32B 5/26 20130101 |
Class at
Publication: |
428/105 ;
428/109; 428/111; 428/113; 442/239; 442/261; 442/286 |
International
Class: |
B32B 5/26 20060101
B32B005/26; B32B 5/12 20060101 B32B005/12; B32B 27/12 20060101
B32B027/12 |
Claims
1. A flexible laminate system with angularly distributed,
controlled modulus threadlines comprising: a flexible core layer
with yarn spacing of greater than 15 epi and up to 30 epi in the
MD, and having an elongation in the MD of less than 0.25 percent at
10 lbf/inch and less than 0.5 percent at 50 lbf/inch; and at least
one fabric cover layer oriented with its respective threadlines at
a bias angle with respect to the threadlines of said core layer,
said cover layer being bonded to said core layer and having a resin
top coating applied thereto.
2. The flexible laminate system of claim 1, said at least one
fabric cover layer comprising at least two said fabric cover
layers.
3. The flexible laminate system of claim 1, said core layer having
less than two percent crimp in the MD.
4. The flexible laminate system of claim 3, said core layer having
at least 21 epi in the CM and an elongation in the CM of not more
than 0.5 percent at 10 lbf/inch.
5. The flexible laminate system of claim 4, said core layer
comprising fibers from among the group of fibers consisting of
polyaromatic amide, polyethylene, Carbon, multifilament liquid
crystal polymer, PBO, para-aramid, Polyester, PEN, aramid polymer,
and Nylon or polyamide fiber.
6. The flexible laminate system of claim 5, comprising a uniform
angular distribution of the machine direction and cross machine
threadlines of said core and cover layers.
7. The flexible laminate system of claim 6, said cover layers
having an uncoated air permeability of greater than 100 cfm/ft2 and
less than 1000 cfm/ft2.
8. The flexible laminate system of claim 7, said core layer
comprising thermoplastic multifilament liquid crystal polymer
yarn.
9. The flexible laminate system of claim 7, said core layer
comprising 1500 denier thermoplastic multifilament liquid crystal
polymer yarn.
10. The flexible laminate system of claim 7, said cover layer
comprising polyester yarn configured at greater than 15.times.15
epi.
11. The flexible laminate system of claim 7, said cover layer
comprising 70 denier polyester yarn configured at 50.times.50
epi.
12. The flexible laminate system of claim 7, an aliphatic urethane
resin top coating applied to at least one said said cover
layer.
13. The flexible laminate system of claim 10, said core layer
comprising thermoplastic mutlifilament liquid crystal polymer yarn
and polyester yarn alternated in a modified weave pattern.
14. The flexible laminate system of claim 7, further comprising
defined inner and outer surfaces, and having at least one film top
layer on the outer surface.
15. The flexible laminate system of claim 7, comprising a core
layer weave density of less than 50%.
16. A flexible laminate system with angularly distributed,
controlled modulus threadlines comprising: a flexible core layer
with yarn spacing up to 30 epi in the MD, elongation in the MD of
less than 0.25 percent at 10 lbf/inch and less than 0.5 percent at
50 lbf/inch, and yarn spacing of at least 15 epi in the CM and
elongation in the CM of not more than 0.5 percent at 10 lbf/inch,
said core layer comprising fibers from among the group of fibers
consisting of polyaromatic amide, polyethylene, Carbon,
multifilament liquid crystal polymer, PBO, para-aramid, Polyester,
PEN, aramid polymer, and Nylon or polyamide fiber; and at least two
fabric cover layers comprising polyester yarn and oriented to said
core layer with their respective threadlines at a bias angle with
respect to the threadlines of said core layer, said cover layers
being bonded to said core layer and having a resin top coating
applied thereto, said layers of said laminate system being
adhesively bonded together, said laminate system further comprising
defined inner and outer surfaces, and having at least one film top
layer bonded to said outer surface.
17. The flexible laminate system of claim 16, comprising a core
layer weave density of less than 50%.
18. A flexible laminate system with angularly distributed,
controlled modulus threadlines comprising: a fabric core layer and
at least two fabric cover layers, said core layer having less than
two percent crimp in the MD and elongation in the MD of less than
0.25 percent at 10 lbf/inch, said core layer comprising
thermoplastic multifilament liquid crystal polymer yarn and
polyester yarn alternated in a modified weave pattern, and having
at least 21 epi in the CM, with elongation in the CM of not more
than 0.5 percent at 10 lbf/inch, said cover layers comprising a
woven polyester yarn fabric of at least 50.times.50 epi with resin
coating, cut and formed with a bias angle with respect to said core
layer, a said cover layer adhesively bonded to each side of said
core layer, and an aliphatic urethane resin top coating applied to
each said cover layer.
19. The flexible laminate system of claim 18, comprising a core
layer weave density of less than 50%.
20. The flexible laminate system of claim 19, comprising a core
layer weave construction of at least 15 and up to 30 epi in the
MD.
21. The flexible laminate system of claim 20, said core layer
having elongation of the MD at 50 lbf/inch of web of less than 0.5
percent.
Description
[0001] This application is a continuation of pending U.S.
application Ser. No. 10/293,828 filed Nov. 13, 2002 which claims
the benefit of U.S. Provisional Application No. 60/337,732 filed
Nov. 13, 2001.
FIELD OF INVENTION
[0002] This invention relates to the construction of multi-layered,
controlled modulus, special purpose fabrics, and in particular to
woven fabrics of controlled modulus or elongation in the machine
direction (MD) or warp axis, with covering layers bonded thereto in
off axis configurations.
BACKGROUND OF THE INVENTION
[0003] The applications for flexible membranes in general include
products such as sails, airfoil and wing systems, aircraft control
surfaces, inflatable structures, airships, temporary shelters,
liquid storage tanks, fuel tanks, flotation devices, seals and
gaskets for aircraft surfaces, and door seals. Current materials in
flexible membranes are based on the following techniques:
[0004] Core structural fiberous components are made of bonded scrim
fiber groups. These core layers of flexible membrane designs are
generally constructed with less than 10 yarns per inch in each of
two orthogonal orientations. The structure of the core layer is
generally formed by resin-bonded intersections between cross
machine (CM) and machine direction (MD) yarns.
[0005] The MD and CM fibers provide along their thread lines or
yarn directions the basic mechanical properties of elongation
resistance and tensile strength. The control of elongation is
important as this property allows the fabrication of structures
that retain their designed shape over a range of loads. The modulus
of a membrane material can be approximated by the elongation of
fibers of that material under defined loads. Testing methods for
measuring elongation follow ASTM (American Society for Testing and
Materials) standards and use sample lengths up to 16 inches for
testing accuracy.
[0006] These scrims are not generally of woven construction, and
have very little structural integrity when the resin bonds have
been broken. In short this type of bonded scrim has little
durability with out modification and the addition of other
components. In most systems these scrims deliver most of the fiber
content necessary in CM and MD to control elongation and provide
adequate tensile strength.
[0007] Fibers such as KEVLAR(.TM.) brand para-aramid, SPECTRA(.TM.)
brand UHMW polyethylene, DYNEEMA(.TM.) brand UHMW polyethylene,
Carbon, VECTRAN(.TM.) brand multifilament liquid crystal polymer,
Zylon(.RTM.) polybenzoxazole (PBO), TECHNORA(.TM.) brand
para-aramid, Polyester (Polyethyleneterephthalate) PEN
(Polyethylene Naphthalate), TWARON(.TM.) brand para-aramid polymer,
and Nylon polyamide fiber and polyester are all used in these core
element scrims. (The applicant makes no claim to the trademarks.)
Because of cost, larger yarn sizes are preferred. Most of these
scrims use structural yarns of 1000 denier or larger. In some cases
smaller non-structural yarns will be used in the opposing direction
to provide for the bonding sites.
[0008] Polyester, PEN, Nylon, VECTRA(.TM.) brand polyester film,
and other films are used for web stability. Because the scrim core
layer does not provide off thread line stiffness, additional
elements are used in current systems. In all current designs at
least one layer of a stiff film (e.g. 1/2 mil polyester) is
incorporated in the laminate. The film most commonly used is
polyester, with a film thickness of from one quarter to one and two
thousands of an inch. It should be noted that the addition of these
films is not a means of adding a thermoplastic adhesive to the
structure. These films are used to provide off-threadline
mechanical properties and general mechanical durability.
[0009] All or most of the interconnect between MD and CD fibers in
the core element or layer is adhesive or resin based. Because the
core elements are not generally woven the integrity of these
systems is based on the various resin adhesive bonds in the
assembly. These resin adhesive systems are typically crosslinked
elastomers or other crosslinked adhesive resins. Yarn is bonded to
yarn and yarn is bonded to film. The result of this dependence on
film interlayer and adhesive is that these structures have overall
durability that is limited to the properties of the film and the
adhesives used. The low to no twist yarn used in these scrims
contributes to these adhesive failures.
[0010] Because of the limitations of film mechanical properties,
off axis fiber components have been developed. Some products add
low count, less than 15 ends per inch (epi) structures or elements
on thread lines that are off or non-aligned with the 0 to 90 degree
angle between the MD and CM axis. As with the MD and CM scrims
these yarn layers are coarse, low-end count structures. Again, like
the core scrims, the off axis scrims are not woven and at most
contain crossing points only in one direction. Also like the core
scrims these off axis scrims comprise yarns of little or no twist.
Twist is a secondary process and adds cost.
[0011] Because of the limitations of the non-woven core, film and
off axis elements, some systems include woven cover fabrics bonded
to the outside of the system. These wovens may contain all the yarn
types of the core elements. However most cover fabrics use deniers
much smaller than 1000. In all current products the cover fabric is
bonded to the core materials with its MD and CM at 0 and 90 degrees
to the core elements. Only laid or bonded scrims are placed off
axis.
[0012] Simple coated and saturated fabrics are also used for
flexible membrane applications. In these designs there are no scrim
elements. However films may be attached by adhesive bonding.
[0013] Resin bonded membrane systems have a catastrophic failure
mode. Because there is little woven interlock in the structural
fiber elements of the current systems, the structure can fail
without failure of the fiber. Low and no twist fiber contributes to
this result. These structures can delaminate and the fiber separate
without breakage of fiber. In flex and tear mode the potential
performance of the fiber is not realized unless the adhesive
bonding quality is equal to the fiber strength. In practice this is
not possible, so adhesive bonding failures are a cause for
premature and catastrophic failures.
[0014] Resin and films have limited properties relative to fiber.
Because of the high dependence on resin bonding, current products
are limited in durability to the flex and adhesion of the bonding
mechanisms.
[0015] The cosmetics of these products may suffer from local
delaminating and mildew prior to a failure in performance. Because
the core and off axis fiber layers use larger yarns, there tend to
be void spaces or interstices in the fabric composite. When
moisture enters these void spaces between the films, delaminating
and mildew are frequently the result.
SUMMARY OF THE INVENTION
[0016] The applications for high strength, low stretch, flexible
membranes in general include products such as sails, airfoil and
wing systems, aircraft control surfaces, inflatable structures,
airships, temporary shelters, liquid storage tanks, fuel tanks,
flotation devices, seals and gaskets for aircraft surfaces, and
door seals. There are a number of other and emerging products that
have similar high strength, low stretch, flexible membrane
performance requirements as the products listed above. The
invention is directed to a flexible membrane system and materials
that can be applied to all of these products and other products
having similar membrane performance requirements. The invention is
susceptible of many forms and applications.
[0017] The invention, simply stated, is a fabric or flexible
membrane system for producing at least a woven fabric of controlled
modulus or elongation in the MD or in the warp axis. This is the
main structural element or core layer of the membrane and a
principal component of invention. One or more woven cover fabrics
may be adhesively and or thermoplasticly bonded to one or both
sides of the core layer off the primary axis, adding one or more
further threadline directions of controlled modulus or elongation
to the system.
[0018] It is therefore an object of the invention to provide a
flexible membrane system with a woven fabric core and woven cover
fabrics all incorporating high strength fibers and a large
percentage of crossing points, where the cover fabrics are applied
with a calculated off-bias orientation to the core layer such that
there is a reduced, uniform angle of shear dependence as between
interlayer thread lines.
BRIEF DESCRIPTION OF THE FIGURES
[0019] FIG. 1 is a three part diagrammatic illustration of a three
layer composite membrane with a FIG. 1A core scrim with zero angle
machine direction, to which a FIG. 1B plus 60 degree off axis cover
fabric is applied to one side, and a FIG. 1C minus 60 off axis
cover fabric is applied to the other side.
[0020] FIG. 2 is a diagrammatic illustration of a point in a
composite of the FIG. 1 layers where crossings are superimposed to
show the uniform distribution and angular spacing of the machine
direction and cross machine threadlines of the three layers.
[0021] FIG. 3 is a diagrammatic illustration of a 5 layer composite
membrane with a core layer and 4 off bias layers configured to
provide uniform distribution and angular spacing of the machine
direction and cross machine threadlines of the five layers.
DESCRIPTION OF PREFERRED EMBODIMENT
[0022] The invention is susceptible of many embodiments. Herein
described are preferred embodiments not limiting of the scope of
the invention. In a first preferred embodiment there is a core
fabric covered with an off axis cover fabric on both sides. It is
preferred that a known chemical adhesion promoter such as
isocyanate or epoxy materials be used on the interface of the core
and cover fiber bundles. The cover fabrics may also have resin or
film top layers laminated or coated on their outside surfaces.
These layers may provide mechanical performance or UV protection or
both.
[0023] The core fabric is constructed in the form of a woven
material using a structural fiber. The fiber may be any of
polyaromatic amide, polyethylene, Carbon, multifilament liquid
crystal polymer, PBO, para-aramid, Polyester, PEN, aramid polymer,
and Nylon or polyamide fiber, and commercial or brand name variants
thereof.
[0024] Crimp is measured by marking a length of fiber in a weave,
then removing this fiber from the weave and applying a one tenth
gram load per denier. The stretched length of the fiber over the
length of the fiber as measured in the weave is the crimp. The
design of the weaving pattern affects weave crimp and fabric tear
strength and damage tolerance. The elongation under load in the
thread line directions of the core element is the result of control
of crimp and the elongation characteristics of the yarns
selected.
[0025] The design of the core material or fabric should address
control of the weaving crimp in the fiber. In order to be a true
weave there must be crossing points present in both axes of the
fabric or core element. Unlike a bonded scrim, which has crossing
points only in the CM direction and hence no crossing point pairs a
plain weave utilizes 100% of the potential crossing points. The
reduction of crossing points in the weave tends to reduce the
crimp, and hence elongation. However, enough crossing points must
be maintained in the weave of the core structure to provide
sufficient toughness. Core layers of preferred embodiments contain
at least 5% of available cross over in the weave. The resistance of
the system to abrasion and flogging will be improved by higher
levels of crossing points.
[0026] The core woven of the preferred embodiment also incorporates
high modulus yarn. There is no preferred embodiment for the fiber
content of the core woven. There are a wide range of user
mechanical and performance requirements affecting the final
selection of fiber content. The core layer or woven may contain at
least one high modulus yarn of greater than 10 grams per denier
(gpd) in warp. The core woven may contain at least one high modulus
yarn greater than 10 gpd in filling. The core woven may contain
additional yarns that are greater than 10 gpd in warp or fill.
Further, the core woven may contain only yarns that are greater
than 10 gpd in warp and fill.
[0027] The elongation under load in the thread line directions of
the cover fabrics is the result of control of crimp and the
elongation characteristics of the yarns selected. Cover fabric will
typically contain more crossing points than the core structure.
Issues of abrasion and damage tolerance are paramount to control of
elongation in these cover fabric elements or components of the
membrane system. The preferred embodiment cover fabrics have warp
and fill ends counts that are greater than 15 ends per inch. End
counts of 50 ends per inch in warp and fill are more preferred in
order to deliver a stable, more easily processed web. The higher
end count also produces a fabric as opposed to an open weave scrim,
which is thicker for a given amount of fiber weight.
[0028] In the preferred embodiment the uncoated cover fabric has
air permeability as measured by ASTM (American Society for Testing
and Materials) methods, greater than 100 cfm/ft2 and less than 1000
cfm/ft2. This provides for a maximum level of stability while
preserving adequate open area for mechanical strike through or
penetration of top coatings to adhesives on the core layers.
[0029] Cover fabrics in the prior art can be woven of fiber that is
greater than 1600 denier. The preferred embodiment cover fabrics of
the invention are made from fiber that is greater than 50 denier
and generally much less than 1600 denier. These smaller yarns give
the best thickness and cover for a given mass content of fiber.
Preferred embodiment cover fabrics utilize at least 5% of the
available crossovers in the weave. As in the design of the core
woven, the cover fabric(s) are preferably true woven with crossing
points in both directions. Cover fabrics containing 100% of the
crossing points are preferred for stability. The use of plain
weaves gives the most stable weave possible.
[0030] Preferred embodiment cover fabrics are supplied and used as
off-axis webs in the construction of a flexible membrane of the
invention. An off axis web of cover fabric is typically formed by
bias cutting from woven or knit tubes. In this process the cover
fabric is first formed as a tube. The tube is then slit in a
helical manner, resulting in a long sheet or off axis web of cover
fabric. This process is typical of bias binding materials. [00311
Forming of off axis web cover fabrics by bias cutting and splicing
allows wovens to be used that are not made on shuttle weaving
machines. The thinner materials that can be made on this type of
shuttle-less machinery allow for having spliced joints in the cover
fabric web which do not create large variations in the thickness of
the web. It will be readily apparent from this description that the
angle of the helical cut will determine the angle of bias of the MD
threadline off the axis of the web. For example, a tube cut
lengthwise, parallel to the tube axis, will result in a web with an
on-axis MD threadline, the length of the tube and the width of the
tube diameter. A tube helically cut at a 45 degree angle off the
tube axis will produce a web with the MD threadline oriented 45
degrees away from the resulting edge or axis of the tube or
resulting web.
[0031] After bias cutting, the cover fabrics are laminated to the
core fabric with their thread lines oriented at the angle
determined by the tube bias cut angle. The tube bias cut angle, as
will be readily understood by those skilled in the art from the
above description, is selected in advance to produce the desired
variation in the cover fabric bias from the reference angles of 0
and 90 degrees of the MD and CM thread lines of the core structure
or layer.
[0032] For the purpose understanding the following examples and the
claims, it can be assumed that the MD (machine direction) and the
CM (cross machine) threadlines of the core fabric and the cover
layers are constructed at right angles. If the MD of a core layer
is designated as a 0 degree reference angle, the CM of the core
layer can be understood to be at a nominal 90 degrees to the MD
reference angle reference, for all practical purposes. With respect
to a core layer MD threadline and the MD threadline of a cover
layer, clockwise rotation in the plane of the fabric or the
membrane is considered positive, and counterclockwise rotation is
negative, as viewed from a common side of the plane of the
membrane. If the MD of the core fabric or layer is defined as the 0
degree reference angle, a bias angle of a cover fabric can be
stated as between 0 and 90 degrees positive or negative from the MD
or reference angle of the core fabric It will be understood that
the bias angle applies to the MD of the cover fabric with respect
to the MD of the core fabric, and the CM's of the respective layers
are displaced 90 degrees from their respective MDs. The distinction
between positive and negative bias angles is most noteworthy when
there is more than one cover layer, as will be apparent in the
examples that follow.
[0033] A first preferred embodiment flexible membrane has at least
one cover fabric bonded to the core fabric with its MD displaced at
a 45 degree bias angle from the MD of the core fabric, so that the
flexible membrane system has four threadline angles uniformly
distributed at 45 degree apart throughout the membrane. In this
example, the angular order of the threadlines is MD.sub.core,
MD.sub.cover, CM.sub.core, CM.sub.cover. These additional
threadlines avoid the requirement to use film to support off axis
loads.
[0034] It will be readily apparent that each additional cover layer
within the overall membrane system will add 2 more threadlines to
the total, permitting a further reduction on the the average
angular displacement as between all threadlines in the plane of the
membrane, and permitting further refinement to the inter-layer
orientations to optimize the desired combination of performance
parameters.
[0035] Referring to FIGS. 1 and 2, for example, in a second
preferred embodiment of the invention, two covers 20 and 30 may be
applied to the core fabric 10 in various arrangements such as
applying one cover to one side of the core fabric, and one cover to
the other side of the core fabric, or both both covers to one side
of the core fabric. The MD lines are shown as solid lines. The CM
threadlines are shown as dashed lines. No inference as to relative
density, crossing point coverage or other weave details is intended
in these figures. The orientation between layers 10, 20, and 30
with respect to their threadlines may be as follows; e.g. the first
cover fabric 20 can have off-axis bias of its MD angle of +60
degrees to the core fabric 10 MD reference angle, and the second
cover fabric 30 can have an off-axis bias of -60 degrees. As will
be readily apparent from this teaching, the dashed CM threadlines
of the cover fabrics 20 and 30 are oriented at minus 30 and plus 30
of the core layer 10 MD reference angle.
[0036] Referring specifically to FIG. 2, where a crossing point in
each of the three layers of FIG. 1 is hypothetically aligned to
illustrate the angular order and displacement of the threadlines,
the net result of the calculated off-axis bias in the covers is a
three layer, 2 threadlines per layer, flexible laminate or membrane
or system that has a fiber-based reinforcement threadline every 30
degrees in the plane of the membrane, with the threadlines
alternating between an MD and a CM threadline. The smaller the
angle between the thread lines, the smaller the shear angle that
the matrix must support. The smaller angles and the alternating MD
and CD threadlines also offer the highest control of elongation in
a nearly isotropic manner.
[0037] As another example, in a third preferred embodiment of the
invention, three covers may be applied to the core fabric in
various arrangements such as applying one cover to one side of the
core fabric, and two covers to the other side of the core fabric,
their respective threadline angles may be aligned as follows; e.g.
the first cover fabric can have an off-axis bias of +45 or -45
degrees, and the other two can have any combination of 22.5 and
67.5 degree bias angles, both being either positive or negative
angles from the reference angle of the core layer. This provides a
membrance system that has fiber-based reinforcement every 22.5
degrees in the plane of the membrane. The smaller the angle between
the thread lines, the smaller the shear angle that the matrix must
support. The orientation of MD's to CD's in the plane of the
membrane is not ideally distributed in an alternating manner when
there is an odd number of covers and each is used with an exclusive
bias angle, but the smaller angles still offer the highest control
of elongation in a nearly isotropic manner.
[0038] Referring to FIG. 3, more covers can be integrated into the
design using the principles of the invention to select bias angles
contributing to the omnidirectional performance of the membrane.
Here, illustrated similarly to the example of FIG. 2, four off-axis
covers 41, 42, 43, 44 have been added to a core layer 40, with bias
angles of plus and minus 36 degrees and plus and minus 72 degrees,
resulting in an MD-CM-MD-CM alternating order of threadlines at 18
degrees apart.
[0039] It will be apparent from the above description and examples,
and is within the scope of the claims, that in the alternative,
while not preferred, the core fabric can be produced and prepared
for assembly of the membrane as an off-axis web. The actual MD,
although off axis from the running direction of the roll or web
from which it is dispensed, may still be designated as the
reference angle of the core layer. The MD and CM threadline angles
of cover layers are still appropriately referenced and calculated
from the actual MD threadlines of the core fabric web, even thought
it is not aligned with the length or running direction of the core
layer roll or web.
[0040] There is no preferred embodiment for yarn type and total
fiber content in the cover fabrics. Like the main structural layer,
various grades of the system are useful. Depending on the range of
modulus and tensile properties required for a specific application,
the fiber type and content can be adjusted. For example, the cover
fabric may contain yarn of greater than 10 gpd. The cover fabric
may contain yarn of less than 10 gpd. And the cover fabric may
contain yarn of greater than 10 gpd and yarn of less than 10
gpd.
[0041] Lamination systems for bonding core and cover materials
provide high peel and tear strength. Core materials or fabrics of
the invention, by their design, have controlled and limited void
content left unfilled by resin after the cover fabrics are applied
and the lamination process is complete. This limited void content
reduces the potential for delaminating and mildew problems. In a
preferred embodiment membrane, resin is in intimate contact with
the core fibers and the cover fibers. Its preferred that a chemical
bonding agent be used at this fiber interface to inprove adhesion.
There are no film layers between the first fabric cover and the
core fabric. Without the use of structural film layers, the
adhesive resin systems surround and penetrate the woven elements.
This allows for the preferred combination of chemical and
mechanical bonding.
[0042] The elimination of the film between the cover fabrics and
the core fabric permits the cover fabric to be fully saturated with
the adhesive resin without significant levels of voids between it
and the core layer. The preferred embodiment lamination method and
resulting laminate of core and cover does not require film for
mechanical performance, but it may contain a film layer at some
level external of the structural combination of core and cover for
further purposes such as UV resistance.
[0043] Thermo plastic resins and coating can be used for thermal
repair and heat-sealing for joining of seams when assembling webs
of the membrane into useful structural forms such as fluid
airfoils, diaphragms, envelopes, and partitions.
[0044] Top coating or film can provide good levels of UV
(ultraviolet light) protection to the fiber. The materials that
provide good UV protection are well known to those skilled in the
art. The selection will depend on factors including cost, weight,
total life, heat-sealing, and adhesion to other layers. Materials
that provide UV protection include but are not limited to EPDM
(Ethylene Propylene), Hytril (EBXL-Hytril thermoplastic elastomer),
Hypalon(.RTM.) brand chlorosulfonated polyethylene elastomers
(CSPE), silicone, florosicones, Aliphatic urethanes, acrylic film,
floro polymers like Tedlar(.RTM.), Kynar(.RTM.) or Teflon(.RTM.)
brand products, vinyl films, and other materials know for their UV
resistance. (No claim is made to any such terms as may be
trademarks.) Topcoats or films can provide pigmentation and
coloration for UV and aesthetic reasons. The addition of pigments
to coatings is also well known to those skilled in the art.
[0045] In the case where a different fluid is present on the
backside of the membrane system, select fibers, yarns, and fabrics,
and in particular, special coatings and films appropriate to the
particular fluid many be used. The materials may be selected to
provide different or additional features or improvements such as
solvent resistance, chemical resistance, and controlled
permeability to gases.
[0046] There are a large number of coatings and films and their
several applications that are well known to those skilled in art
and are equally applicable here. Given the large number of
potential materials that can be contained in the membrane system of
the invention, it is not possible to list all possible
combinations. Most of the UV resistant materials listed above have
applications to the fluid and gas retention. A few materials are
unique to gas retention, such as Polyester films, butyl rubber, and
Aclar films.
[0047] A preferred embodiment flexible membrane of the invention,
suitable for use as an airfoil for a large offshore yacht, for
example, utilizes a core material which contains 1500 denier
Vectran HS(.RTM.) brand multifilament liquid crystal polymer yarn
in the MD. The construction is 30 yarns in the MD. In this example
the stretch or modulus in the MD is less than 1/4 percent at a 10
lbf/inch, (pounds force per square inch) with a breaking load of
1690 lbf/inch.
[0048] In the cross machine direction the yarn is 1500 denier
Vectran HS(.RTM.) type thermoplastic material and 500 denier
polyester. The weave is 6 ends of polyester and one of the
thermoplastic material, repeated three time per inch, for a total
of 21 epi. In this example the stretch of the CM is 1/2 percent at
10 lbf/inch, with a breaking load of 230 lbf/inch.
[0049] The weave pattern is modified basket
2.times.2.times.2.times.1 in the fill with the polyester weaving as
a pair and the thermoplastic material weaving single. The polyester
yarn does not provide the high modulus behavior in the filling but
the additional crossing points add significantly to the overall
mechanical properties of the woven. The total crossing points of
this example is 78%.
[0050] The cover fabric for this embodiment is made of a polyester
yarn of 70 denier. The weave construction is 50.times.50 epi. The
uncoated permeability as measured by ASTM methods is 400
cfm/ft.sup.2. The weave is plain.
[0051] The cover fabric is scoured free of contaminants and coated
with stabilizing adhesive resin such as a urethane. The resin
coating helps stabilize the cover fabric during the biasing
process. The cover fabric is cut and formed into a 45-degree bias
materials as described above, using adhesive bonding of lap joints
where necessary.
[0052] The core material is coated both sides with a urethane resin
and a biased cover fabric is applied to each side in a lamination
process.
[0053] A top coating is made of a resin based on aliphatic
urethane, pigmented with five percent by weight of titanium dioxide
pigment. The coating is applied to the each of the cover fabric in
a 1.5 mil thickness. The mass per square yard of the laminate is
17.5 oz/yd.sup.2. The thickness of the coating is 22 mils. The
resulting flexible membrane system as tested by the applicant had
an MD slit tear measurement when performed to FAA (Federal Aviation
Administration) standards, of 580 lbf/in.
[0054] As will be readily understood by those skilled in the art,
the preferred embodiments are illustrative of the invention, and
not exhaustive of the scope of the invention. Other and various
embodiments are within the scope of the invention as described
above and claimed below.
[0055] For example, there is within the scope of the invention a
flexible laminate system with at least one core consisting of a
fibrous layer configured with elongation in the MD at 50 pounds
force per inch of web of less than 0.5 percent elongation, and at
least one cover comprising a fabric layer with yarn spacing in at
least one direction greater than 15 ends per inch, where the cover
is bonded to the core with the cover MD axis at a bias angle with
respect to the core MD.
[0056] The bias angles may be about 45 degrees respectively. The
cover may be at least a first and a second cover, where the first
cover bias angle is about +60 degrees, and the second cover bias
angle is about -60 degrees. And the at least one cover may be at
least a first, second and third cover, where the first cover bias
angle is about +22.5 degrees, the second cover bias angle is about
-45 degrees, and the third bias angle is about +67.5 degrees. And
also, the at least one cover may be at least first, second, third,
and fourth covers, where the covers have respective bias angles of
about +36 degrees, -36 degrees, +72 degrees, and -72 degrees.
[0057] Also, the at least one cover may be multiple covers, where
the covers are bonded to the core with respective cover MD's at
different bias angles with respect to the core MD. The fibrous
layer may be a woven layer having less than 2 percent crimp in the
MD. And the woven layer may have less than 50% of its available
crossing points. The flexible laminate system may further consist
of a UV protective film layer external of the core and the
cover.
[0058] As another example, there is a flexible laminate system with
first and second woven layers, where the first layer has less than
2% crimp in the MD, and the second layer includes at least one
cover layer with yarn spacing in at least one direction of greater
than 15 ends per inch. The first woven layer is combined with the
second woven layer such that the first layer is bonded to the cover
layer with the cover layer MD at a bias angle to the first layer
MD. Also, the second woven layer may consist of multiple cover
layers, where the first layer is combined with the second layer
such that the cover layers are bonded to the first layer with
respective cover layer MDs at different bias angles with respect to
the first layer MD.
[0059] The first woven layer may have elongation in the MD at 50
pounds force per inch of web of less than 0.5 percent. The first
woven layer may have less than 50% of its available crossing points
used.
[0060] As yet another example, there is a flexible laminate system
with first and second woven layers, where the first layer is a core
layer that has less than 50% of its available crossing points, the
second layer consists of a cover layer with yarn spacing in at
least one direction of greater than 15 ends per inch, and the cover
layer is bonded to the first layer with its cover layer MD at a
bias angle to the first layer MD. Also, the second woven layer may
be or have multiple cover layers, where the first layer is combined
with the second layer wherein the cover layers are bonded to the
first layer with respective cover layer MDs at different bias
angles with respect to the first layer MD.
[0061] The first woven layer may have elongation in the MD at 50
pounds force per inch of web of less than 0.5 percent. The first
woven layer may have less than 2% crimp in the MD.
[0062] There is also another example; a flexible laminate system
consisting of a core and at least two covers of a common cover
fabric, where the core uses 1500 denier thermoplastic multifilament
liquid crystal polymer yarn, the core construction has up to 30 epi
in the MD with elongation in the MD of less than 0.25 percent at 10
lbf/inch. The core consists of mutlifilament liquid crystal polymer
yarn and polyster yarn alternated in a modified weave pattern
having at least 21 epi in the CM, with elongation in the CM of not
more than 0.5 percent at 10 lbf/inch. The total core crossing
points consist of greater than 50 percent. The common cover fabric
consists of 70 denier polyester yarn woven at 50.times.50 epi, with
a resin coating, cut and formed with a 45 degree bias angle. There
is a cover applied to one or each side of the core, and an
aliphatic urethane resin top coating is applied to each cover.
[0063] Other examples within the scope of the invention and the
claims that follow will be readily apparent to those skilled in the
art from the description and figures provided.
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