U.S. patent application number 11/612512 was filed with the patent office on 2008-04-03 for window skin panel and method of making same.
Invention is credited to Paul S. Nordman.
Application Number | 20080078494 11/612512 |
Document ID | / |
Family ID | 34226012 |
Filed Date | 2008-04-03 |
United States Patent
Application |
20080078494 |
Kind Code |
A1 |
Nordman; Paul S. |
April 3, 2008 |
WINDOW SKIN PANEL AND METHOD OF MAKING SAME
Abstract
A lightweight, structurally strong skin panel having one or more
optically transparent areas forming see-through windows, and a
method of making same. A plurality of layers of pre-preg fiber tape
comprised of a plurality of optically transparent fibers
pre-impregnated with an optically transparent resin is positioned
over a plurality of metal sheets, with each metal sheet having a
plurality of openings where windows are to be formed. The pre-preg
tape layers and the metal sheets are layered onto one another such
that one or more of the metal sheets is sandwiched between a pair
of the pre-preg tape layers. The assembly is placed in a molding
tool, and the tool placed within a vacuum bag. A vacuum assisted
resin transfer forming process is used, together with heating of
the molding tool, to produce a high strength, lightweight,
integrated skin panel having optically transparent window portions.
The skin panel eliminates the bulky and heavy frame structure
traditionally employed on aircraft windows and has sufficient
structural strength to be used as a portion of the skin of a
fuselage of an aircraft without the need for reinforcing frame-like
elements around the window areas.
Inventors: |
Nordman; Paul S.; (Renton,
WA) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
34226012 |
Appl. No.: |
11/612512 |
Filed: |
December 19, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10654765 |
Sep 4, 2003 |
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11612512 |
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Current U.S.
Class: |
156/168 |
Current CPC
Class: |
Y02T 50/43 20130101;
B29C 70/84 20130101; B32B 17/10853 20130101; B29L 2031/3076
20130101; B64C 1/1484 20130101; B32B 17/02 20130101; B29C 70/885
20130101; B32B 17/10302 20130101; B29C 70/745 20130101; B29C 70/088
20130101; Y02T 50/40 20130101; B29L 2031/778 20130101 |
Class at
Publication: |
156/168 |
International
Class: |
A43D 43/06 20060101
A43D043/06 |
Claims
1. A method of forming a high strength, structural window skin
panel, comprising: using a plurality of metal sheets to form a
frame structure, wherein each said metal sheet includes an opening
defining a window area; aligning said metal sheets with one another
so that said openings are aligned to form a uniform window opening;
laying a plurality of generally optically transparent, fiber
pre-preg tape layers pre-impregnated with an optically transparent
resin against said metal sheets such that at least one of the metal
sheets is sandwiched between a pair of said fiber pre-preg tape
layers; further arranging said fiber pre-preg tape layers to fully
cover said uniform window opening while overlaying said metal
sheets; heating the metal sheet and the fiber pre-preg tape layers
such that said optically transparent resin flows and wets the fiber
pre-preg tape layers and the metal sheets; and curing, the fiber
pre-preg tape layers and the metal sheets such that the fiber
pre-impregnated resin tape layers and metal sheets form an
integrated, lightweight window skin panel having an optically
transparent, single pane window portion, and having an allowable
tension strength of at least about 40,000 pounds per square inch
per ply of and in the frame panel.
2. The method of claim 1, wherein the fiber pre-preg tape layers
are each are comprised of glass fibers.
3. The method of claim 1, wherein the resin comprises an optically
transparent aliphatic epoxy resin.
4. The method of claim 1, wherein the fiber pre-preg tape layers
comprise fibers having an index of refraction matching an index of
refraction of the resin.
5. The method of claim 1, wherein at least one of the metal sheets
comprises a metallic foil strip.
6. The method of claim 1, wherein at least one of the metal sheets
is comprised of aluminum.
7. The method of claim 1, wherein at least one of the metal sheets
is comprised of titanium.
12. The method of claim 1, wherein the fiber pre-impregnated resin
tape has a width of approximately 0.125 inch (3.175 mm) to about
12.0 inches (304.8 mm).
13. A method of manufacturing a lightweight, structurally strong,
integrated transparent window skin panel, comprising: providing a
plurality of pre-preg tape layers each having fibers
pre-impregnated with an optically transparent resin, the resin and
the fibers being selected to have substantially the same index of
refraction; providing a plurality of metal sheets each having a
plurality of spaced apart openings formed therein; arranging said
metal sheets such that said spaced apart openings in each of said
sheets are aligned to form a corresponding plurality of spaced
apart window opening areas; layering the pre-preg tape layers and
the metal sheets onto a tool such that the metal sheets and the
pre-preg tape layers are aligned one atop the other so that the
pre-preg tape layers completely cover the openings and overlay a
periphery of the metal sheets, with at least a pair of the pre-preg
tape layers sandwiching at least one of the metal sheets; heating
the tool, the metal sheets, and the pre-preg tape layers so that
the resin flows to cover portions of the metal sheets and wets the
fibers in each of the pre-preg tape layers, the resin and fibers
being substantially transparent to form a plurality of see-through
window portions in the skin panel, with the skin panel having a
structural strength sufficiently strong to be used as a portion of
a fuselage skin panel of an aircraft.
14. The method of claim 13, wherein providing the pre-preg tape
layers pre-impregnated with a resin comprises providing a plurality
of pre-preg tape layers each pre-impregnated with a transparent,
aliphatic epoxy resin.
15. The method of claim 13, wherein providing a plurality of metal
sheets comprises providing a plurality of aluminum sheets.
16. The method of claim 13, wherein providing a plurality of metal
sheets comprises providing a plurality of titanium sheets.
17. The method of claim 13, wherein the fibers are comprised of
glass fibers.
18. The method of claim 13, wherein providing a plurality of
pre-preg tape layers comprises providing a plurality of pre-preg
tape layers each having a width of approximately 1/8'' (3.175 mm)
to about 12'' (304.8 mm).
19. The method of claim 13, further comprising placing a caul plate
atop the metal sheets, the pre-preg tape layers and tool.
20. The method of claim 19, further comprising placing the caul
plate, the metal sheets, the pre-preg tape layers, and the tool
into a vacuum bag and removing the air therein.
21. The method of claim 13, using an autoclave to heat the tool,
the metal sheets and the pre-preg tape layers.
22. The method of claim 21, wherein the autoclave heats the tool,
metal sheets, and the pre-preg tape layers to approximately 250
degrees Fahrenheit under approximately 100 to 200 psi of pressure;
and wherein the tool, metal sheets and the pre-preg tape layers are
allowed to cure at a temperature of about 250.degree. F. for
approximately 3-5 hours.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part
application of U.S. application Ser. No. 10,654,765 filed Sep. 4,
2003, and presently pending, which is incorporated by reference
into the present application. The present application is also
related in general subject matter to U.S. application Ser. No.
10/655,257, filed Sep. 4, 2003, and U.S. application Ser. No.
11/316,173, filed Dec. 22, 2005, the disclosures of which are also
both incorporated by reference into the present application.
FIELD
[0002] The present disclosure relates to transparent window skin
panels, and more particularly to a laminated transparent window
skin panel and method of making same particularly well adapted for
use in forming structurally strong yet lightweight, optically
transparent skin panels for use with mobile platforms such as
aircraft and spacecraft.
BACKGROUND
[0003] Passenger windows in most commercial aircraft are relatively
small in size. This is due, in part, to the limited capabilities of
current transparent window materials and also due to the heavy and
complex support structure needed to support the windows within the
frame of the aircraft. Such present day window assemblies used on
various forms of airborne mobile platforms such as aircraft,
spacecraft, rotorcraft, etc., often are of double pane
construction. The use of double pane construction (involving two
distinct, optically transparent window panels) has typically been
required to meet structural strength goals. The use of two distinct
window panels, however, adds weight that limits the payload
capacity of the mobile platform.
[0004] Typically, the transparent window materials used in the
above-described double panel window assemblies consist of a
transparent polymer. While very successful and exhibiting such
useful qualities as high durability and easy formation of complex
shapes, these polymer windows do have a limited strength
capability.
[0005] Windows made from transparent materials also typically
require a supplemental support structure, often termed in the
industry as a "doubler", that extends about the periphery of the
transparent window portion. The doubler interfaces the transparent
window panel to the skin panel of the mobile platform and provides
the needed structural strength at the peripheral region of the
transparent window panels to enable them to be secured to the
surrounding skin panel structure. This doubler support structure
generally is made up of one or more window forgings, window panes,
and/or stringers. Each component is designed to strengthen the skin
panel which surrounds and supports the window. However, the doubler
structure increases the cost and weight of the completed window
assembly, thereby providing an incentive to keep passenger windows
relatively small.
[0006] Accordingly, it would be highly desirable to provide a new,
single pane window panel and method of making same that is both
lightweight and sufficiently structurally strong to act as a
structural skin panel on a mobile platform. In particular, it would
be highly desirable to provide a new, lightweight, integrated,
single pane window panel assembly especially well suited for an
aircraft or spacecraft, or other form of mobile platform, that has
sufficient structural strength to function as a skin panel for the
mobile platform. Furthermore, it would be desirable to provide an
integrated window panel assembly that is sufficiently structurally
strong to act as a skin panel without the need to incorporate the
traditional doubler support structure at the peripheral area of the
window panel portion of the assembly. Such a lightweight,
integrated window panel assembly would enable even larger windows
to be used on present day aircraft and spacecraft without incurring
significant additional weight.
SUMMARY
[0007] A transparent window skin panel and method of making same
for use in a mobile platform is provided. In one embodiment the
transparent window skin panel includes a plurality of metal sheets.
A fiber reinforced resin at least partially surrounds the plurality
of metal sheets and sandwiches at least a portion of one metal
sheet therebetween. The fiber reinforced resin is optically
transparent. A cutout is formed within each of the plurality of
metal sheets. The cutout corresponds to a window area in the fully
formed transparent window skin panel. The window skin panel is
sufficiently structurally strong to act as an integral portion of
the fuselage of a mobile platform, for example as a portion of a
fuselage of an aircraft or spacecraft. The window skin panel has a
single pane construction that is an important factor in achieving
its light weight, as compared to double pane windows.
[0008] A method of manufacturing the transparent window skin panel
is also provided. The method includes using a pre-preg tape layer
comprised of a plurality of fibers pre-impregnated with a resin and
a metal sheet. The pre-preg tape layer and the metal sheet are
layered onto a tool such that the metal sheet and the pre-preg tape
layer are aligned one atop the other, with the pre-preg tape layer
extending over an aligned cutout or window opening area in the
metal sheet. The tool, metal sheet, and pre-preg tape layer are
heated such that the resin flows to partially cover the metal sheet
and the fibers. When the assembly of the metal sheet and pre-preg
tape layer is cured, the fibers of the pre-preg tape layer and the
resin are substantially optically transparent and thus form a
see-through window portion in the skin panel.
[0009] In one specific method of manufacture, a plurality of metal
sheets are incorporated and a plurality of pre-preg tape layers are
arranged to sandwich at least one of the metal sheets. The assembly
is placed in a heated mold and formed in a single step into a
lightweight, integrated skin panel having a generally optically
transparent, single pane window area.
[0010] In its various embodiments, the skin panel forms a
lightweight yet structurally strong panel that provides the
important benefit of an integrally formed window portion. Since the
window portion of the assembly effectively forms a single pane
window portion that does not require any separate doubler structure
around the perimeter of the transparent window portion, the
assembly provides a significant weight savings over conventional
double pane window assemblies presently used in many aircraft and
spacecraft. The weight savings increases the payload of the
aircraft or spacecraft. Alternatively, the weight savings allows
significantly larger windows to be employed in a mobile platform
without incurring any additional weight penalty over conventional
double pane windows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present disclosure will become more fully understood
from the detailed description and the accompanying drawings,
wherein:
[0012] FIG. 1 is a partial view of a front of an aircraft having an
embodiment of a transparent window skin panel constructed in
accordance with the present disclosure;
[0013] FIG. 2 is a side cross sectional view of the transparent
window skin panel taken in the direction of arrow 2-2 in FIG. 1;
and
[0014] FIG. 3 is an exploded perspective view of the materials used
to construct the transparent window skin panel of FIG. 2.
DETAILED DESCRIPTION
[0015] The following description of various embodiment(s) is merely
exemplary in nature and is in no way intended to limit the present
disclosure, its application or its uses.
[0016] Referring to FIG. 1, there is illustrated one embodiment of
a transparent window skin panel 10 constructed according to
principles of the present disclosure. The skin panel 10 is shown
mounted to and forming a fuselage portion of an aircraft 12. The
aircraft 12 generally includes a skin 13. The window skin panel 10
includes a frame area 14 and a plurality of single pane windows 16.
While in the particular example provided, the transparent window
skin panel 10 is illustrated as including three side windows of the
aircraft 12, it is to be understood that the transparent window
skin panel 10 may be used in any portion of the aircraft 12 and
have a single window or any plurality of windows. The single pane
windows 16 may be significantly larger in area than conventional,
double pane windows. However, because of the significant weight
savings provided by the transparent window skin panel 10 over
conventional double pane window assemblies, no additional weight
penalty is incurred when using larger windows.
[0017] With reference to FIG. 2, a cross section of the transparent
window skin panel 10 is shown. In one embodiment the frame 14
includes a plurality of structural sheets, for example, metal
sheets, that form rigid structural panels. One or more pre-preg
fiber tape layers 22 form the transparent single pane windows. The
pre-preg fiber tape layers 22 are saturated with an optically
transparent resin, to be described in greater detail in the
following paragraphs. In the embodiment of FIG. 2, at least one of
the metal sheets 20 is sandwiched between the fiber pre-preg tape
layers 22. In this example three metal sheets 20 are illustrated,
however, a greater or lesser number of metal sheets 20 may be used
as needed to provide the desired degree of structural strength and
rigidity. While the metal sheets 20 in this example are shown
having a uniform thickness, it will be appreciated that different
thicknesses could just as easily be used. The single pane window
skin panel 10 has an allowable tension strength of preferably about
40,000-60,000 pounds per square inch per ply of fiber reinforced
resin material, and more preferably about 50,000 pounds per square
inch per ply of fiber reinforced resin material. This makes the
transparent window skin panel 10 especially well suited for the
demanding needs of commercial aircraft, military aircraft and
aerospace applications.
[0018] The transparent window skin panel 10 is preferably lap
spliced to the skin 13 of the aircraft 12. This lap splice (not
shown) results in a high strength coupling wherein the transparent
window skin panel 10 is mechanically fastened to an adjacent skin
panel (not shown) of the aircraft skin 14.
[0019] Turning now to FIG. 3, one preferred method of constructing
the transparent window skin panel 10 will now be described. A
molding tool 24 is provided, illustrated schematically in FIG. 3,
capable of receiving the components of the transparent window skin
panel 10. The tool 24 has a smooth polished surface 26 shaped to
form the outer surface of the transparent window skin panel 10.
Alternatively, a glass mold may be used to form the smooth outer
surface of the tool 24. The shape of the single pane windows 16,
while illustrated as essentially rectangular and flat in FIGS. 1
and 2, may comprise any shape. For example, the single pane windows
16 could comprise round, square, oval or hexagon shapes if desired.
Virtually any shape of single pane window 16 could be formed. For
an aircraft application, the transparent window skin panel 10 will
ideally be made with single pane windows 16 that are substantially
rectangular or oval in shape, and which have a slight cross
sectional curvature to match the overall curvature of the fuselage
into which the transparent window skin panel 10 will be
integrated.
[0020] With further reference to FIG. 3, a plurality of metal
sheets 28 and a plurality of fiber pre-preg tape layers 30 are then
provided. Each metal sheet 28 includes a plurality of spaced apart
openings 34 formed therethrough. The metal sheets 28 are further
aligned so that one of the single pane windows 16 is able to be
formed in within each of the openings 34. Again, while the openings
34 (and therefore the windows 16) are illustrated as rectangular,
it is to be understood that any shape may be employed. The shape of
the openings 34 will dictate the shape of the single pane windows
16.
[0021] The metal sheets 28 are preferably made of aluminum due to
its light weight and high strength. However, various other metals
may just as easily be employed including, for example, titanium,
stainless steel, magnesium or carbon steel. Preferably, the metal
sheets 28 are constructed from metal foil tape laid out to form and
meet the preferred shape and dimensions of the metal sheet 28.
Alternatively, a single sheet of metal may be substituted for the
use of a plurality of the metal sheets 28.
[0022] The pre-preg tape layers 30 each include a plurality of
fiber plies 36 that are woven together to form a fiber mesh. The
orientations of the fiber plies 36 are based on the desired
directional strength of the transparent window skin panel 10. The
fiber plies 36 may be arranged to provide unidirectional or
bi-directional strength (e.g., the fiber plies 36 may run either in
one direction or a plurality of directions). In one form the fiber
plies 36 may be comprised of a weave of glass fibers each having a
rectangular cross section. Fibers having other cross sectional
shapes besides a rectangular cross sectional shape may also be
used.
[0023] For commercial aircraft applications, in order to carry the
loads in the fuselage, the fiber plies 36 are preferably arranged
in a plurality of different orientations. Typical layup
orientations are designated in degrees with zero degrees being
along the longitudinal axis of the fuselage and 90 degrees being
around the circumference of the fuselage. In one embodiment, the
fiber plies 36 are arranged with about 25% of the plies oriented in
the zero degree direction, about 25% in the 90 degree direction,
about 25% in the +45 degree direction and about 25% in the -45
degree direction. The resin 38 may comprise an aliphatic epoxy
resin, although various other resins that are generally transparent
when fully cured may be employed. The resin 38 is also preferable
selected to be highly resistant to ultraviolet degradation, and
aliphatic epoxy resin meets this criterion well. The index of
refraction of the resin 38 is also preferably matched to the index
of refraction of the fiber plies 36.
[0024] In one embodiment, the pre-preg tape layers 30 may each be
about 0.125 inch (3.175 mm) to about 12.0 inches wide (304.8 mm).
However, tape layers of other suitable dimensions could just as
easily be employed.
[0025] With further reference to FIG. 3, the metal sheets 28 and
the pre-preg tape layers 30 are then laid atop the tool 24 in an
order corresponding to the desired order of lamina in the
transparent window skin panel 10. In the particular example
provided, the metal sheets 28 alternate with double layers of the
pre-preg tape layers 30 such that at least one of the metal sheets
28 is sandwiched between a pair of the pre-preg tape layers 30.
[0026] A flexible caul plate 40 having a polished surface, to form
a high quality optical surface for the finished windows 16
(illustrated schematically in FIG. 3) is then closed onto the
components. A vacuum bag 42 is used to seal the tool 24, the
pre-preg tape layer 30 and the metal sheets 28. The air trapped
within the vacuum bag 42 is then removed under suction. Finally,
the components are placed in an autoclave 44 (illustrated
schematically in FIG. 3).
[0027] The components may be heated to preferably approximately 250
degrees Fahrenheit under a pressure of preferably approximately
100-200 psi. Within the autoclave, the resin 38 melts and flows
through the fiber plies 36 to fully wet (e.g. fully covering and
saturating) the fiber plies 36 and metal sheets 28. The transparent
window skin panel 10 is then cured at a suitable temperature, for
example about 250.degree. F., over a period of time, for example
about 3-5 hours, until the resin 38 hardens. The components are
then removed from the autoclave 44, vacuum bag 42, and the tool 24
and caul plate 40, and the transparent window skin panel 10 is
removed. The metal sheets 28 correspond to the metal sheets 20
within the frame 14 (FIG. 2) and the resin 38 and fiber plies 36
make up the pre-preg fiber tape layers layers 22 (FIG. 2). The
fiber plies 36 and resin 38 form the single pane windows 16 within
each of the openings 34.
[0028] As noted above, the single pane windows 16 (FIGS. 1 and 2)
are generally optically transparent. To impart transparency, the
resin 38 is transparent and the fibers of the fiber plies 36 have
an index of refraction such that they are substantially
transparent. The index of refraction of the fiber used in the fiber
plies 36 is matched to the index of refraction of the resin 38. In
this way, the transparent window skin panel 10 is generally
optically transparent in the areas of the openings 34 in the metal
sheets 28.
[0029] By integrally forming the optically transparent resin 22 and
fiber plies 36 of the single pane window 16 with the metal sheets
20 of the frame 14 area, the solid and high strength transparent
window skin panel 10 is provided. Simultaneously, the heavy doubler
or like support structure typically used as a reinforcing frame
structure for aircraft windows is substantially eliminated, thus
reducing the weight of the aircraft. This allows for larger windows
to be employed, if desired, without increasing the weight of the
aircraft.
[0030] In present day commercial aircraft construction, the weight
savings provided by the single window pane construction of the
transparent window skin panel 10 is substantial. In a large,
commercial passenger jet aircraft having about 200 windows, the
construction of the single pane windows 16 can produce a weight
savings of about 2000 pounds, or roughly the equivalent of about 10
passengers, over a fuselage constructed with the same number of,
and comparably sized, double pane windows. For a commercial
passenger jet aircraft amount having about 75 windows, the weight
savings is estimated to be about 500 pounds, or approximately about
2.5 passengers. This weight savings amounts to a significant fuel
savings for a commercial aircraft, or alternatively can allow the
payload to be increased over what could be achieved with an
aircraft having conventional double pane windows,
[0031] While the present disclosure has been described in
connection with aircraft windows, it will be appreciated that the
various embodiments described herein can be incorporated on other
forms of mobile platforms such as buses, trains, ships, rotorcraft,
spacecraft, etc., where composite panels may be employed. The
weight savings and structural strength provided by the window skin
panel 10 is especially advantageous for use with the fuselage or
body portions of mobile platforms, where the overall weight of the
mobile platform is an important consideration for performance or
fuel economy reasons. The present invention can also be implemented
on fixed structures where lightweight panels having window portions
are needed.
[0032] The description of the various embodiments herein is merely
exemplary in nature. Thus, variations that do not depart from the
gist of the present disclosure are intended to be within the scope
of the appended claims.
* * * * *