U.S. patent application number 13/148057 was filed with the patent office on 2011-12-01 for method for manufacturing a structure with cellular cores for a turbojet nacelle.
This patent application is currently assigned to AIRCELLE. Invention is credited to Thierry Deschamps, Bertrand Desjoyeaux, John Moutier.
Application Number | 20110290333 13/148057 |
Document ID | / |
Family ID | 40901996 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110290333 |
Kind Code |
A1 |
Desjoyeaux; Bertrand ; et
al. |
December 1, 2011 |
METHOD FOR MANUFACTURING A STRUCTURE WITH CELLULAR CORES FOR A
TURBOJET NACELLE
Abstract
The invention relates to a method for manufacturing a structure
with cellular cores (202) that can be used in the structural panel
of a turbojet nacelle, including at least one block of cellular
cores (A, B) having a central portion (5a, 5b) with core honeycomb
cells (7a, 7b) and at least two side portions (9a, 9a', 9b, 9b')
each including side honeycomb cells (11a, 11b), wherein said method
includes the following steps: A) forming junction walls on the side
honeycomb cells (11a, 11b), the junction walls being capable of
interacting for forming a junction area (213); B) unfolding the
junction walls thus formed; and C) joining the walls thus unfolded
(46) and belonging to two different side portions (9a, 9b)
end-to-end so that said junction walls (46) are fitted together so
as to form a junction area (213). The invention also relates to a
structural panel and to a nacelle including a structure with
cellular cores obtained by said method.
Inventors: |
Desjoyeaux; Bertrand;
(Sainte Adresse, FR) ; Deschamps; Thierry;
(Heuqueville, FR) ; Moutier; John; (Le Havre,
FR) |
Assignee: |
AIRCELLE
Gonfreville l'Orcher
FR
|
Family ID: |
40901996 |
Appl. No.: |
13/148057 |
Filed: |
January 8, 2010 |
PCT Filed: |
January 8, 2010 |
PCT NO: |
PCT/FR2010/000019 |
371 Date: |
August 5, 2011 |
Current U.S.
Class: |
137/15.1 ;
156/197; 428/116 |
Current CPC
Class: |
B32B 2307/50 20130101;
B32B 3/12 20130101; B32B 2038/0052 20130101; Y10T 137/0536
20150401; B32B 7/12 20130101; B32B 15/14 20130101; F02C 7/04
20130101; F02K 1/827 20130101; Y02T 50/672 20130101; B32B 15/04
20130101; B32B 3/266 20130101; B32B 15/20 20130101; B32B 3/18
20130101; B32B 2307/724 20130101; B32B 2307/7242 20130101; Y10T
428/192 20150115; B32B 5/142 20130101; B32B 37/12 20130101; G10K
11/172 20130101; B32B 5/24 20130101; Y10T 156/1003 20150115; Y10T
428/24149 20150115; B32B 38/0012 20130101; Y02T 50/60 20130101;
B32B 2307/546 20130101; B32B 2605/18 20130101; B32B 2307/102
20130101 |
Class at
Publication: |
137/15.1 ;
156/197; 428/116 |
International
Class: |
F02K 99/00 20090101
F02K099/00; B32B 3/12 20060101 B32B003/12; B31D 3/02 20060101
B31D003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 5, 2009 |
FR |
09/00500 |
Claims
1. A method for manufacturing a structure with cellular cores that
can be used in a structural panel of a turbojet nacelle, including
at least one block of cellular cores having a central portion with
core honeycomb cells and at least two side portions each including
side honeycomb cells, wherein said method comprises: A) forming
junction walls on the side honeycomb cells, the junction walls
being capable of interacting for forming a junction area; B)
unfolding the junction walls thus formed; and C) joining the walls
thus unfolded and belonging to two different side portions
end-to-end so that said junction walls are fitted together so as to
form a junction area.
2. The method according to the preceding-claim 1, wherein a length
of each junction wall is greater than or equal to a largest length
of the side and/or core honeycomb cells.
3. The method according to claim 1, wherein the side parts
belonging to cellular core blocks, whereof the side and core
honeycomb cells have different sizes, are joined end-to-end.
4. The method according to claim 1, wherein, in step A, one opens
the edge honeycomb cells situated on edges of a side part of a
block intended to be joined and honeycomb cells adjacent to the
edge honeycomb cells so as to form the junction walls.
5. The method according to claim 4, wherein the edge and adjacent
honeycomb cells are opened by section to a lateral side and/or a
wall of a honeycomb cell.
6. The method according to claim 1, comprising an additional step D
in which the fitting done in step C is maintained by clamps or
staples.
7. A structural panel for a nacelle surrounding a turbojet engine,
comprising at least one cellular core structure obtained using the
method according to claim 1.
8. The panel according to claim 7 being an acoustic panel whereof
the cellular core structure(s) are coated on one faces thereof with
an outer skin impermeable to air and on their-another face with an
air-permeable perforated inner skin.
9. The panel according to claim 7, having at least two cellular
core structures superimposed one on the other.
10. An aircraft engine nacelle, comprising at least one structural
panel according to claim 7.
11. The nacelle according to the preceding claim, wherein the
structural panel(s) are situated in an air intake zone of said
nacelle.
Description
TECHNICAL FIELD The present invention relates to a method for
making a structure with cellular cores for use in a structural
panel for a turbojet nacelle.
[0001] The invention also relates to a panel and a nacelle
including such a structure with cellular cores.
BACKGROUND
[0002] Airplane turbojet engines are surrounded by a nacelle to
protect them and ensure the operation thereof. The nacelle is made
up of walls composed of non-structural panels and structural
panels. The latter parts ensure a sufficient stiffness of the
nacelle. To that end, structural panels usually have one or more
layers of cellular core structures (commonly called "honeycomb"
structures). These layers are generally covered with a skin on
their so-called outer face, i.e. the face radially furthest from
the axis of the engine, and on their inner face, i.e. the face
radially closest to the axis of the engine.
[0003] The structural panel is then assembled by arranging the
different skins and layers, which are then pasted on a mold with
the required shape. The assembly is cured in a furnace so as to
grip the layers and polymerize the adhesives.
[0004] In parallel, turbojet engines generate substantial noise
pollution. There is therefore a strong demand aiming to reduce this
pollution, and even more so given that the turbojet engines used
are becoming increasingly powerful.
[0005] To that end, some of the panels used are acoustic structural
panels whereof the layers are generally covered on the outer face
with an air-impermeable skin, called "solid," and on the inner face
with an air-permeable perforated skin, called "acoustic."
[0006] The structural acoustic panel can also comprise several
layers of cellular core structures between which a multi-perforated
skin, called a "septum," is located. This skin is adhered between
the cellular core structures by heating during the assembly/gluing
phase of the panel.
[0007] Such panels constitute acoustic resonators able to "trap"
the noise and therefore attenuate the sound emissions towards the
outside of the nacelle.
[0008] In a known manner, a cellular core structure comprises at
least one cellular core block comprising a central part having core
honeycomb cells and two lateral parts each having a plurality of
honeycomb joining cells.
[0009] The acoustic properties of the acoustic structural panel,
i.e. its noise absorption rate as a function of the frequency and
sound level of the noise, depend in particular on the joining of
the cellular core block(s).
[0010] The join of the cellular joining cells is commonly done
using a foaming adhesive, such as the FM410.RTM. adhesive, which
has a significant expansion capacity. The adjacent edges of the
cellular core block(s) are coated with the adhesive, which, when it
expands, blocks the honeycomb cells by creating
overthicknesses.
[0011] The use of adhesive requires too long a placement and cutout
time of the overthicknesses from an industrial perspective.
[0012] Furthermore, these overthicknesses have the drawback of
decreasing the effective acoustic surface of the cellular core
structure as well as causing abrupt impedance interruptions, which
contributes to decreasing the acoustic performance of the acoustic
panel during the operation of the turbojet engine.
[0013] Also known from application WO2008/113904 is a structure
with cellular cores whereof the honeycomb edge cells situated on
the edges of several blocks with cellular cores making up said
structure have been sectioned, then fitted together to join said
blocks.
[0014] However, such a structure with cellular cores requires
maintenance by stressing the cellular core structure, which makes
production more complex.
[0015] Moreover, this embodiment does not make it possible to
obtain optimal bending strength.
BRIEF SUMMARY
[0016] One aim of the present invention is therefore to provide a
cellular core structure that is easy to manufacture and has good
bending strength.
[0017] Another aim of the present invention is to provide a
cellular core structure able to effectively absorb the noise from
the turbojet engine in an acoustic panel.
[0018] To that end, according to a first aspect, the invention
relates to a method for manufacturing a structure with cellular
cores that can be used in the structural panel of a turbojet
nacelle, including at least one block of cellular cores having a
central portion with core honeycomb cells and at least two side
portions each including side honeycomb cells, wherein said method
includes the following steps:
[0019] A) forming junction walls on the side honeycomb cells, the
junction walls being capable of interacting for forming a junction
area;
[0020] B) unfolding the junction walls thus formed; and
[0021] C) joining the walls thus unfolded and belonging to two
different side portions end-to-end so that said junction walls are
fitted together so as to form a junction area.
[0022] The joining of one or more cellular core blocks by fitting
junction walls together makes it possible to avoid stressing the
structure obtained using the inventive method. Indeed, the junction
is made by simply interweaving said walls without the latter
necessarily being in contact.
[0023] The bending strength is improved. In fact, the majority of
the junction walls not being in contact with each other, they can
each deform freely without impacting the other walls. Moreover, the
stresses pass through the outer skins from one outer skin to the
other, which makes it possible to prevent the concentration of
forces in the axis of the joint.
[0024] Furthermore, the cellular core structure obtained using the
inventive method has the advantage of not obstructing the honeycomb
cells at the joints of the cellular core blocks. As a result, the
cellular core structure very effectively absorbs the noise from the
operation of the turbojet engine.
[0025] According to other features of the invention, the inventive
method comprises one or more of the following optional features,
considered alone or according to all possible combinations: [0026]
the length (e) of each junction wall is greater than or equal to
the largest length of the side and/or core honeycomb cells, which
makes it possible to improve the bending strength; [0027] the side
parts belonging to cellular core blocks whereof the side and core
honeycomb cells have different sizes are joined end-to-end, which
makes it possible to adapt the mechanical strength of the structure
as needed; [0028] in step A, one opens the edge honeycomb cells
situated on the edges of a side part of a block intended to be
joined and honeycomb cells adjacent to the edge honeycomb cells so
as to form the junction walls, which allows a simple and effective
formation of the junction walls; [0029] the edge and adjacent
honeycomb cells are opened by section to a lateral side and/or a
wall of a honeycomb cell; [0030] the inventive method comprises an
additional step D in which the fitting done in step C is maintained
by fastening members, in particular by clamps or staples, which
makes it possibly to durably maintain the cellular core structure
without stress.
[0031] According to a second aspect, the invention relates to a
structural panel for a nacelle surrounding a turbojet engine,
characterized in that it is equipped with at least one cellular
core structure obtained using the inventive method.
[0032] Preferably, the panel according to the invention is an
acoustic panel whereof the cellular core structure(s) are coated on
one of their faces with an outer skin impermeable to air and on
their other face with a perforated inner skin, which makes it
possible to benefit from the advantages of said structure in an
acoustic structural panel.
[0033] According to one preferred alternative, the inventive panel
includes at least two cellular core structures superimposed one on
the other, which makes it possible to strengthen the mechanical
rigidity of the panel according to the invention.
[0034] According to another aspect, the invention relates to an
aircraft engine nacelle, characterized in that it comprises at
least one panel according to the invention.
[0035] Preferably, the structural panel(s) are situated in the air
intake zone of said nacelle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The invention will be better understood upon reading the
following non-limiting description, done in reference to the
appended figures.
[0037] FIG. 1 is a cross-sectional view of a single-layer
structural panel according to the present invention;
[0038] FIG. 2 is a cross-sectional view of a dual-layer structural
panel according to the present invention;
[0039] FIG. 3 is a diagrammatic view of the inventive method;
[0040] FIG. 4 is a top view of a structure obtained at the end of
the inventive method;
[0041] FIG. 5 is a front view of a honeycomb cell used in the
present invention;
[0042] FIG. 6 is an alternative of the embodiment of FIG. 3.
DETAILED DESCRIPTION
[0043] As shown in FIG. 1, the structural panel 1 according to the
invention can be a single-layer acoustic panel comprising a
cellular core structure 2 according to the invention formed by one
or more, and in this case two cellular core blocks A and B joined
together. In the event a single cellular core block is used, it is
joined on itself to form a cellular core structure, for example by
forming a substantially cylindrical structure that can be used in a
nacelle air intake.
[0044] The cellular core block(s) A and B used can have any
geometric shape, such as square, or any other suitable shape.
[0045] In the event the inventive structure includes a plurality of
cellular core blocks A, B defining a plurality of junction zones,
it is then possible to choose each block to obtain the desired
mechanical strength and, if applicable, the desired acoustic
absorption.
[0046] The cellular core structure 2 is sandwiched between an inner
skin 3 and an outer skin 4, which allow the transition of
mechanical stresses. Furthermore, the presence of these skins 3 and
4 makes it possible to keep the cellular core structure 2 in a
single element.
[0047] These two cellular core blocks A, B include a central
portion 5 comprising core honeycomb cells 7a, 7b and typically
several, in this case two side portions 9a, 9b each comprising a
plurality of side honeycomb cells 11a, 11b. A block can for example
include at least four side portions. The side honeycomb cells 11a,
11b of each block A and B are adjacent to the junction zone 13, the
features of which will be detailed below.
[0048] As shown in FIGS. 3 and 4, the core honeycomb cells 7a, 7b
and the side honeycomb cells 11a, 11b in this case have hexagonal
sections, thereby forming so-called honeycomb structures. It is
possible for said honeycomb cells 7a, 7b and 11a, 11b to have
sections with any geometric shape other than hexagonal. As shown in
FIG. 1, the section of the core 7a and side 11 a honeycomb cells of
the block A can for example be smaller than that of the core 7b and
side 11 b honeycomb cells of the block B, so as to meet the
acoustic and/or mechanical stresses imposed by the manufacturer's
specifications.
[0049] Preferably, the side 11a, 11b and core 7a, 7b honeycomb
cells are made of metal, an alloy, or a composite material so as to
facilitate the production of the core 7a, 7b and side 11a, 11b
honeycomb cells and to impart good mechanical strength to the
latter. The material forming the inner skin 3 can be made in a
metal material, such as aluminum or titanium, or fabric, and the
material forming the outer skin 4 can be a multi-layer composite
material or a metal material such as aluminum or titanium.
[0050] The structural panel 1 as shown in FIG. 1 is an acoustic
panel. In this case, the inner skin 3 includes perforations 15
located facing the core 7a, 7b and side 11a, 11b honeycomb cells.
In this way, the structural panel 1 can absorb the sound annoyance
created by the operation of the turbojet engine.
[0051] In an alternative shown in FIG. 2, the structural panel 101
is a dual-layer panel according to the invention comprising two
layers of cellular core blocks, respectively formed by blocks A, B
and A', B'. Said layers are assembled together by known means and
sandwiched between an inner skin 103 and an outer skin 104 similar
to those of FIG. 1. The other elements forming the structural panel
101 are identical to those of the structural panel 1 shown in FIG.
1, the corresponding references being the same.
[0052] According to one alternative, it is possible to obtain a
structural panel including a number of layers of cellular core
blocks greater than 2, in particular greater than or equal to
3.
[0053] In this dual-layer panel, the cellular core blocks A, B on
the one hand, and A', B' on the other are joined together in one or
more joint zones 113.
[0054] The operating principle of an acoustic panel like those 1
and 101 shown in FIGS. 1 and 2 is known in itself; the panel 1, 101
is intended to be mounted in the inner wall of an aircraft nacelle,
preferably in the air intake zone of said nacelle, so that the
inner skin 3, 103 is located opposite the engine located in said
nacelle.
[0055] The noise emitted by this engine penetrates the honeycomb
cells A, B via orifices 15 situated in the inner skin 3, 103, and
vibrates inside these core 7a, 7b and side 11a, 11b honeycomb cells
that make up the acoustic resonators. In this way, a dissipation of
the acoustic energy and subsequent reduction of the noise level are
possible. In order to improve the acoustic absorption, it is
possible to apply a perforated skin, also called septum, between
the two layers of blocks with a cellular core A, B and A', B' of
the structural panel 101 so that the core 7a', 7b' and side 11a',
11b' honeycomb cells of the blocks A' and B' also make up acoustic
resonators.
[0056] According to the embodiment shown in FIGS. 3 and 4, the
cellular core structure 202 used in the structural panel according
to the invention is obtained using the inventive method, which
includes a step A, symbolized by the arrow 30, a step B, symbolized
by the arrow 31, and a step C (not shown).
[0057] In step A, junction walls 36 are formed on the side
honeycomb cells 11a and 11b, the junction walls 36 being able to
cooperate to form a joint zone.
[0058] To that end, according to the embodiment shown in FIG. 3,
the edge honeycomb cells 33a, 33b are opened situated on the edges
of a side part 9a, 9b of one or more blocks A, B intended to be
joined and the adjacent honeycomb cells 34a, 34b to the edge
honeycomb cells 33a, 33b so as to form the junction walls 36. In
this way, advantageously, junction walls 36 are formed on the side
honeycomb cells 11a and 11b, the junction walls 36 being able to
cooperate to form a joint zone.
[0059] In this embodiment, the edge 33a and 33b and adjacent 34a
and 34b honeycomb cells are opened by section on a lateral side
and/or a wall of a honeycomb cells using any means known by those
skilled in the art. Thus, for example, it is possible to make a
cutout using a cutting tool such as a pair of scissors.
[0060] According to another embodiment not shown, it is possible to
use one or more cellular core blocks whereof the junction walls are
formed during the production of said block(s). According to another
embodiment, the junction walls can be attached using any means
known by those skilled in the art on a cellular core block already
formed.
[0061] In step B, the junction walls 36 thus formed are unfolded
using any means known by those skilled in the art, in particular by
using a clip. The deployment of the junction walls 36 thereby makes
it possible to obtain a larger length of the joint zone.
[0062] As shown in FIG. 4, in step C, the walls thus unfolded 46
belonging to two different side parts 9a and 9b are joined
end-to-end so that said junction walls 46 fit together to form a
joint zone 213.
[0063] Advantageously, the cellular core structure obtained using
the method according to the present invention has the advantage of
not obstructing the honeycomb cells at the junction of the cellular
core blocks. As a result, the inventive structure effectively
absorbs the noise coming from the operation of the turbojet
operation.
[0064] According to one alternative, the junction walls 46 are
unfolded so as to arrange them substantially parallel to each other
so that the junction walls 46 thus unfolded fit together like a
comb.
[0065] The structure according to the invention 201 can be formed
by a single block joined on itself or by joining a plurality of
cellular blocks, in particular two blocks A, B or three cellular
blocks.
[0066] The unfolded junction walls 46 can advantageously have a
length e greater than or equal to the largest length l of a larger
side or core honeycomb cell.
[0067] The largest length l is defined as the greatest distance
between two edges of the honeycomb cell that are not immediately
adjacent. In the case of regular honeycomb cells, this largest
length l corresponds to the diameter of the circle inscribed or
marked out of the largest honeycomb cell.
[0068] The fitting together in step C can be done in the "ribbon"
direction 51, corresponding to the orientation of the cellular core
block A, B before expansion (see FIG. 5). The direction of
"expansion" 53 corresponds to a direction perpendicular to the
ribbon direction 51 (see FIG. 5). In one alternative, it is also
possible to join one block in the "ribbon" direction and another
block in the "expansion" direction.
[0069] The "expansion" direction designates the direction in which
the core 7a, 7a', 7b, 7b' and side 11a, 11a', 11b, 11b' honeycomb
cells are opened so as to form open cells able to trap sound and
thereby form the honeycomb structure.
[0070] Thus in the case shown in FIG. 3, the fitting together is
done in the ribbon direction.
[0071] It is also possible for the opening of the honeycomb cells
11a, 11b to allow fitting together in the expansion direction, as
shown in FIG. 6.
[0072] According to one embodiment, in step C, at least two
cellular core blocks whereof the side and core honeycomb cells are
different sizes are joined end-to-end. According to one
alternative, a same cellular core block can have side and core
honeycomb cells of different sizes.
[0073] Thus, in the event at least two cellular core blocks of
different sizes are joined, the largest length l is taken relative
to the largest side and core honeycomb cells present in block A
and/or block B.
[0074] In the event two blocks are joined including side and core
honeycomb cells of substantially the same size, the largest length
l can be taken relative to any side or core honeycomb cells.
[0075] According to one embodiment, the inventive method can
comprise an additional step D in which the fitting together done in
step C is maintained using fastening members.
[0076] The fastening members are for example clamps or staples,
which makes it possible to ensure good maintenance.
[0077] The junction can be maintained by compacting in a bladder
before curing prior to applying a usual glue between the cellular
core blocks thus joined to fasten the outer skin.
[0078] The structure 2, 102, 202 obtained using the inventive
method has one or more joint zones 13, 113 and 213, which are not
stressed. Thus, the implementation of the method is simplified
compared to the embodiments described in the prior art.
[0079] Furthermore, the majority of the junction walls 46 are not
in contact, which makes it possible to ensure good bending
strength. In fact, the junction walls 46 can each deform
independently of the other junction walls. The interweaving of the
cellular core blocks allows the passage of forces from one outer
skin to the other so as to avoid a concentration of these forces in
the axis of the junction.
* * * * *