U.S. patent application number 14/019787 was filed with the patent office on 2014-01-16 for hybrid composite for erosion resistant helicopter blades.
This patent application is currently assigned to Teledyne Scientific & Imaging, LLC. The applicant listed for this patent is Teledyne Scientific & Imaging, LLC. Invention is credited to Janet B. Davis, Sergio dos Santos e Lucato, David B. Marshall, Olivier H. Sudre.
Application Number | 20140014263 14/019787 |
Document ID | / |
Family ID | 43380962 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140014263 |
Kind Code |
A1 |
Davis; Janet B. ; et
al. |
January 16, 2014 |
HYBRID COMPOSITE FOR EROSION RESISTANT HELICOPTER BLADES
Abstract
A protective hybrid composite for a rotor blade is based on the
use of tape cast ceramic layers densified by pre-ceramic polymer
infiltration methods and laminated together with polymer matrix
composite prepregs, with or without an embedded metallic mesh, to
form a conforming helicopter blade cladding that is laminated to
the blade surface for added erosion protection. The hybrid
composite is fabricated to net shape and laminated to the blade
using either an adhesive or a polymer composite prepreg inner
layer. Installation is accomplished by a standard composite
fabrication method of vacuum bagging the blade while the system is
laminated to its surface. Repair methods based on removal of
ceramic tiles is facilitated by incorporation of a metallic mesh
element laminated beneath the ceramic tiles that can be used to
heat the tile and decrease its adhesion strength.
Inventors: |
Davis; Janet B.; (Thousand
Oaks, CA) ; Marshall; David B.; (Thousand Oaks,
CA) ; Sudre; Olivier H.; (Thousand Oaks, CA) ;
dos Santos e Lucato; Sergio; (Thousand Oaks, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Teledyne Scientific & Imaging, LLC |
Thousand Oaks |
CA |
US |
|
|
Assignee: |
Teledyne Scientific & Imaging,
LLC
Thousand Oaks
CA
|
Family ID: |
43380962 |
Appl. No.: |
14/019787 |
Filed: |
September 6, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12650172 |
Dec 30, 2009 |
8556589 |
|
|
14019787 |
|
|
|
|
61220033 |
Jun 24, 2009 |
|
|
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Current U.S.
Class: |
156/242 |
Current CPC
Class: |
B64C 27/473 20130101;
B29D 99/0025 20130101; B64C 2027/4736 20130101 |
Class at
Publication: |
156/242 |
International
Class: |
B29D 99/00 20060101
B29D099/00 |
Claims
1. A method of making a hybrid composite for a helicopter blade
comprising: tape casting ceramic materials in thin sheets and
including an organic binder that renders the thin sheets flexible;
densifying the thin sheets without applied pressure; forming in a
green state the thin sheets into curved ceramic segments formed to
net shape; laminating the thin sheets with polymer composite
prepreg layers at low temperature.
2. The method of claim 1, wherein the densifying includes
pressureless sintering to full or nearly full density.
3. The method of claim 2, further comprising introducing
pre-ceramic polymer infiltrations to aid in the densifying.
Description
PRIORITY
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/650,172 filed Dec. 30, 2009; said
application claims priority to and the benefit of U.S. Patent
Application No. 61/220,033 filed Jun. 24, 2009, which is
incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to a hybrid composite segment.
Specifically, the present invention is for a hybrid composite
segment for erosion resistant helicopter rotor blades.
BACKGROUND OF THE INVENTION
[0003] Impact from sand and other debris can be detrimental to the
lifetime of rotating components such as helicopter blades. In a
desert environment, blade leading edges are exposed to both rain
and sand erosion.
[0004] One attempt at protecting blade leading edges is to use a
leading edge metallic erosion strip consisting of nickel (Ni) on an
outboard portion and titanium (Ti) on the inboard portion of the
blade. The metallic strips are further protected by polymeric tapes
or coating even though these are generally less effective in rain
erosion conditions.
[0005] Other attempts at increasing the life of rotor blades can be
found in U.S. patent application publication no. 2005/0169763, for
example, which uses a strip of resilient polymer adhered to the
leading edge of the blade. Others have simply placed a ceramic
component onto the leading edge of the rotor blade, as disclosed in
U.S. Pat. Nos. 6,447,254, 5,782,607, and 5,542,820. Still others
have capped the leading edge with a nanoparticle-reinforced
elastomer, as disclosed in U.S. Pat. No. 6,341,747. However, the
above prior art attempts do not increase the time between
maintenance of the rotor blades and decrease costs.
[0006] In view of the above, it will be apparent to those skilled
in the art from this disclosure that there exists a need for an
improved erosion resistant helicopter rotor blade. This invention
addresses this need in the art as well as other needs, which will
become apparent to those skilled in the art from this
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Referring now to the attached drawings that form a part of
this original disclosure:
[0008] FIG. 1 illustrates a plurality of hybrid segments in
accordance with an embodiment of the present invention;
[0009] FIG. 2A illustrates the plurality of hybrid segments
disposed on a leading edge of a helicopter rotor blade in
accordance with the embodiment of the present invention;
[0010] FIG. 2B is a magnified view and partial cut-away of selected
hybrid segments in FIG. 2A;
[0011] FIG. 3A illustrates another embodiment of the present
invention wherein the hybrid segments are disposed on a leading
edge and include tiles that extend across an upper and lower
surface of the blade;
[0012] FIG. 3B is a magnified view and partial cut-away of selected
hybrid segments in FIG. 3A;
[0013] FIG. 4A is a partial cut-away and schematic of the
embodiment shown in FIGS. 3A and 3B;
[0014] FIG. 4B is a partial cut-away and schematic of another
embodiment of the present invention wherein a gap is present at a
tip of the blade;
[0015] FIG. 4C is a partial cut-away and schematic of another
embodiment of the present invention wherein tiles are staggered in
position from one layer to the next layer;
[0016] FIG. 4D is a partial cut-away and schematic of another
embodiment of the present invention wherein tiles of varying
thicknesses are in a staggered array; and
[0017] FIG. 5 is a partial cut-away and schematic of another
embodiment of the present invention with an embedded metallic
mesh.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Referring to FIGS. 1-2, a first embodiment of a hybrid
composite 1 is shown generally at 1. The hybrid composite 1
includes a plurality of hybrid segments 12 disposed on a leading
edge 11 of a rotor blade 10. The hybrid composite 1 protects areas
of the blade 10 most prone to erosion damage. The hybrid segments
12 are disposed side by side on the blade 10 on a portion of the
blade and are spaced apart at a predetermined distance. Thus,
protection is provided at a lower cost because the hybrid segments
12 can be placed only in areas that experience high erosion. Each
of the hybrid segments 12 includes multiple thin layers of
erosion-resistant ceramic material, alternating with layers of
tough fiber-reinforced polymer matrix composite 16.
[0019] The hybrid composite 1 comprises multiple thin layers of
segmented, erosion-resistant ceramic material, alternating with
continuous layers of fiber reinforced polymer matrix composite 16.
The number of layers is preferably 2 to 10 layers, for example,
that provides an overall thickness of the composite 1 in the range
of 1 to 3 mm, for example. The hybrid composite 1 is tolerant to
damage, while presenting a ceramic surface with high hardness and
erosion resistance. When disposed on the blade 10, the hybrid
composite 1 takes the form of a net shaped cladding. Thus, the
present invention advantageously provides a hybrid composite 1
formed as a net shaped cladding that is laminated directly to the
surface of the blade 10 using the polymer matrix composite 16 or
another adhesive. In addition, the curved ceramic segments, which
are formed to net shape, are laminated with polymer composite
prepreg layers. The ability to produce the ceramic elements to net
shape using thin flexible tape-cast layers that can be molded in
their green state is beneficial.
[0020] The erosion-resistant ceramic material comprises a hard
ceramic containing, for example, Al.sub.2O.sub.3, SiC,
Si.sub.3N.sub.4 and B.sub.4C. In the embodiment shown in FIGS. 1-2,
the exterior ceramic material constitutes an exterior shell 14, and
the interior ceramic material constitutes an interior shell 18. A
layer of the polymer matrix composite 16 is disposed between the
exterior shell 14 and the interior shell 18 as well as between the
interior shell 18 and the leading edge 11.
[0021] The exterior shell 14 protects against erosion from sand and
rain. Furthermore, the multilayer structure of the hybrid composite
1 protects against unusually excessive erosion that may eventually
penetrate the exterior shell 14. The polymer matrix composite 16
includes optimal reinforcement architectures to reduce crack
opening displacements of the ceramic shells 14, 18 or tiles 20 in
the event of fracture and to bond strongly to the ceramic material
to prevent the loss of broken fragments.
[0022] The hybrid segments 12 are bent around the leading edge 11
so as to generally take the form of the leading edge 11. That is,
the hybrid segments 12 can be C-shaped or U-shaped. Specifically,
the hybrid segments 12 are formed such that an exterior surface
follows the outer-mold line profile of the blade 10 including the
leading edge or blade tip 11 curvatures. In other words, the
exterior shell 14 is disposed on a layer of the polymer matrix 16
positioned on the interior shell 18 such that the exterior shell 14
continues or matches an exterior contour of the blade 10. The
interior shell 18 is directly adhered to the leading edge 11 of the
blade 10 using the polymer matrix composite 16 or an adhesive.
[0023] In use, a plurality of the hybrid segments 12 is disposed on
the blade 10. Preferably, the segments 12 are spaced apart at a
predetermined distance. The predetermined distance can affect the
stiffness and is determined to allow deflection matching to the
underlying blade 10. In addition, the lateral dimensions of the
hybrid segments 12 can affect stiffness and are determined or
adjusted accordingly.
[0024] Various hybrid segments 12 can be replaced as they become
worn without having to replace all of the segments 12. That is, if
a portion of the blade 10 experiences more wear than other
portions, the corresponding hybrid segments 12 with higher wear can
be replaced. In addition, the composition of the hybrid segments 12
can be varied to tailor stronger segments for those portions of the
blade 10 that consistently have more wear than other portions.
[0025] Unlike prior art components that are formed as a single
piece along the length of the leading edge, the hybrid segments 12
are not monolithic. Specifically, the hybrid segments 12 are made
as replaceable pieces that are disposed on the leading edge 11 and
are individually removable as wear occurs. This advantageously
allows failure in a non-catastrophic manner. That is, the hybrid
segments 12, in their segmented geometry, can be replaced without
replacing an entire, one-piece component that covers the entire
length of the leading edge.
[0026] Indeed, the use of the hybrid segments 12 advantageously
allows field repair by replacement of individual hybrid segments 12
or individual exterior shells 14. As explained in detail below, the
hybrid composite 1 can include a metallic mesh 22 to aid in removal
of the hybrid segments 12 or merely the exterior shell 14.
[0027] The hybrid composite 1 is assembled as a single blade cover
or cladding with at least one continuous polymer matrix composite
16 layer holding the hybrid segments 12 in place. The design and
manufacture of the hybrid composite 1 facilitates assembly while
not precluding subsequent replacement of individual damaged hybrid
segments 12. The ceramic tiles 20 and polymer composite matrix 16
layers are assembled and formed onto the blade 10 by vacuum molding
in a tool that defines the outer mold line shape. Once assembled,
the laminate stacks are vacuum bagged and warm pressed to form a
final configuration.
[0028] In the embodiment of the hybrid composite 1 shown in FIG. 3,
each of the hybrid segments 12 further include a plurality of tiles
20. Specifically, the hybrid segments 12 are extended across the
blade 10 using multiple thin layers of erosion-resistant ceramic
material, in the form of tile 20, alternating with layers of
fiber-reinforced polymer matrix composite 16. The tiles 20 are
placed sequentially and are substantially aligned with one another
as the plurality of tiles 20 extend across the top and bottom
surfaces of the blade 10. The erosion-resistant ceramic material of
the tile 20 comprises a ceramic containing, for example,
Al.sub.2O.sub.3, SiC, Si.sub.3N.sub.4 and B.sub.4C. In the
embodiment of FIG. 3, the exterior ceramic material bent around the
leading edge 11 and in the form of exterior tiles 20 constitutes
the exterior shell 14, and the interior ceramic material bent
around the leading edge 11 and in the form of interior tiles 20
constitutes the interior shell 18. The number of layers is
preferably 2 to 10 layers, for example, that provides an overall
thickness of the composite 1 in the range of 1 to 3 mm, for
example.
[0029] FIGS. 4A-D are schematics illustrating examples of hybrid
composites 1 with various laminate stacks. FIG. 4A is the stack
used in the embodiment of FIG. 3 and has uniform thickness ceramic
tiles 20 that overlie one another in alignment. The embodiment in
FIG. 4B also has ceramic tiles 20 that overlie one another in
alignment but also have hybrid segments 12 that are in two
sections. In other words, a gap is present at the tip of the blade
10 and a layer of the polymer matrix composite is disposed therein.
The embodiment of FIG. 4C includes ceramic tiles 20 having a
uniform thickness that are staggered in position from one layer to
the next. FIG. 4D also illustrates tiles 20 that are staggered from
one layer to the next. However, the tiles 20 are of varying
thickness and a thick, single-layer hybrid segment 12 is disposed
at the blade tip 11.
[0030] A method of making the hybrid composite 1 is provided
herein. Basically, the hybrid segments 12 and tiles 20 are made by
tape casting a slurry of ceramic materials in thin sheets and
densifying to net shape without applied pressure. Thus, the hybrid
segments 12 can be formed as curved ceramic segments. The thin
sheets preferably take the form of a tile and are laminated with
polymer composite prepreg layers. The inventive method of making
the hybrid segments 12 advantageously produces ceramic elements to
net shape using thin flexible tape-cast layers that can be molded
in their green state. As cast, the green thin sheets (tapes)
contain an organic binder that renders them flexible. In this
state, the green thin sheets can be placed within ceramic tooling
and shaped. Upon heat-treatment, the binder burns out and the
sheets partially sinter and become rigid. In this way, the hybrid
segments 12 are formed such that its exterior surface follows the
outer-mold line profile of the blade 11 including the blade tip
curvatures. The binder phase in the tape facilitates lamination of
green tapes at room temperature. Therefore, thin green tapes can be
stacked together to increase the thickness of the ceramic tiles or
to produce tiles with a tapered thickness. The tile thickness can
also be tapered by ply drop-off during lamination rather than by
costly machining. Thicker surface tiles can be used in highly
impacted areas and thinner tiles in areas that experience less
severe erosion in service. Furthermore, the ability to use tape
lamination to build complex shaped ceramic tiles will allow
consideration of a large number of protective cover designs without
the restriction of a processing cost penalty.
[0031] The use of pressureless sintering to full or nearly full
density advantageously provides a large decrease in cost relative
to hot-pressed materials. Previously, high density was achieved by
using expensive hot pressing. The method of making the hybrid
composite 1 further includes the addition of a pre-ceramic polymer
infiltrations rather than pressure to aid densification. After
pressureless sintering, the relative density of the ceramic hybrid
segments will be at least 65%, for example. The density is
increased by infiltration of the connected porosity with a
pre-ceramic polymer or precursor slurry that can be converted to
ceramic through an additional heat-treatment. High-yield slurries
and precursors are used routinely by those skilled in the art to
densify alumina and silicon carbide fiber reinforced composites.
These composites are infiltrated and heated to a temperature
suitable for ceramic conversion of the precursor but below the
densification temperature of the polymer composite matrix several
times prior to heating (without pressure) to the final sintering
temperature. Ultimately, the final density will depend on the
number of infiltration cycles used. In this way, polymer composite
matrix densities greater than approximately 90%, for example can be
achieved.
[0032] The use of segmented ceramic layers in the hybrid composite
1, which simplifies production of conformal structures, allows
field repair by replacement of individual tiles after damage,
contributes to high damage tolerance of the composite under impact
and bending loads, and contributes to the ability to strain-match
the blade 10.
[0033] The present invention also advantageously provides the
ability to select fiber volume fraction and lay-up within the
continuous polymer matrix composite 16 layer, which allows the
stiffness in various loading directions to be controlled. The
present invention further provides the ability to attach hybrid
laminates with a hard, dense ceramic strike face (the exterior
surface of exterior shell 18) under ambient temperature conditions
that will not damage the blade 10. That is, the hybrid composite 1
including the hybrid segments 12 with tiles 20 is field removable
and replaceable.
[0034] The composite 1 can also be configured to account for
thermal conductivity and dielectric requirements established to
ensure that a deicing system installed in the blades 10 remains
functional. Through selection of materials for the ceramic strike
face and the fiber reinforcement, conductivity can be 12 W/mK or
0.20 cal/cm sec K, for example. Thus, the present invention
provides the protection described above without hindering the
deicing system of the blade 10.
[0035] Referring to FIG. 5, the hybrid composite 1 may include a
conductive metallic mesh 22 comprised of wires embedded beneath a
layer of ceramic material. The metallic mesh 22 is laminated
directly beneath a ceramic layer of the hybrid segment 12. The
metallic mesh 22 can be used in any of the embodiments described
herein. In the embodiment shown in FIG. 5, the metallic mesh 22 is
directly beneath the exterior shell 14. However, the metallic mesh
22 may be placed beneath each layer of ceramic material, as
conditions require. The metallic mesh 22 is used to heat the
polymer matrix composite 16 beneath a damaged segment 12 or
individual tile 20. The tile 20, for example, is removed and a new
tile 20 (and possibly a new prepreg layer) is laminated in its
place.
[0036] To remove a tile 20, the mesh 22 beneath it is heated by
passing a current through the wires of the mesh 22 or by using
handheld RF or microwave generators (such as those used as medical
devices) to reduce the adhesive strength of the polymer matrix
composite 16 locally. The replacement tile 20 is placed into the
gap left by the removed tile 20. A vacuum bag and heating pad is
then placed locally over the new tile 20 to affix it to the erosion
resistant cladding. Additionally, the embedded metallic mesh 22
could serve a dual role by providing lightening strike
protection.
[0037] In understanding the scope of the present invention, the
term "comprising" and its derivatives, as used herein, are intended
to be open ended terms that specify the presence of the stated
features, elements, components, groups, integers, and/or steps, but
do not exclude the presence of other unstated features, elements,
components, groups, integers and/or steps. The foregoing also
applies to words having similar meanings such as the terms,
"including", "having" and their derivatives. The terms of degree
such as "substantially", "about" and "approximate" as used herein
mean a reasonable amount of deviation of the modified term such
that the end result is not significantly changed. For example,
these terms can be construed as including a deviation of at least
.+-.5% of the modified term if this deviation would not negate the
meaning of the word it modifies.
[0038] While only selected embodiments have been chosen to
illustrate the present invention, it will be apparent to those
skilled in the art from this disclosure that various changes and
modifications can be made herein without departing from the scope
of the invention. For example, the size, shape, location or
orientation of the various components can be changed as needed
and/or desired. Components that are shown directly connected or
contacting each other can have intermediate structures disposed
between them. The functions of one element can be performed by two,
and vice versa. It is not necessary for all advantages to be
present in a particular embodiment at the same time. Thus, the
foregoing description of the embodiments according to the present
invention is provided for illustration only, and not for the
purpose of limiting the invention.
* * * * *