Title of the invention
Impregnation mandrel with vacuum liner for making a gas
turbine'casing made of composite material
5 Background of the invention
The present invention relates to the general field of
gas turbine casings, and molre particularly holding casings of
gas turbine fans for aeronautical engines.
In a gas turbine aeronautical engine, a fan casing
10 fulfils a number of functions. It defines the incoming air
stream to the engine, supports abradable material with respect
to the tip of the fan vanes, supports an optional structure
for sound wave absorption for acoustic inlet treatment of the
engine and incorporates or supports a holding shield. The,
15 latter comprises a trap for catching debris such as ingested
items or fragments of damaged vanes thrown out by centrifuge
action to prevent them from passing through the casing and
reaching other parts of the aircraft.
Making a casing for holding a fan made of composite
20 material has already been proposed. Reference could be made to
document EP 1 961 923 which describes the production of a
casing made of composite material of evolutive thickness,
comprising the formation of a fibrous reinforcement by
superposed layers of a fibrous texture and densification ofthe
fibrous reinforcement by a matrix. According to this
invention, the fibrous texture is made by three-dimensional
v~eaving with evolutive thickness and is wound in several
superposed layers onto a mandrel having a central wall of
5 profile corresponding to that of the casing to be manufactured
and two lateral flanges of profile corresponding to those of
the external flanges of the casing. The resulting fibrous
preform is held on the mandrel and impregnation by resin is
completed under vacuum prior to polymerisation. The winding on
10 a mandrel of a woven texture of evolutive thickness as
described in this document directly gives a tubular preform
having the'preferred profile with variable thickness.
In practice, the resin impregnation step cvnducLed
under vacuum requires a supple envelope (or liner) to be
15 applied to all the fibrous reinforcement, and especially at
the level of the flanges of the reinforcement which will later
form the external flanges of the casing. A difference in
pressure is then set between the exterior and the space
delimited by the mandrel and the liner containing the fibrous
20 reinforcement. The injection of resin into this space can then
start.
During this step, it was noted that setting the vacuum
tends to generate tension in the layers of fibrous texture
positioned at the level of the angles of flanges between the
25 flanges and the central wall of the mandrel, this tension
setting causing the fabrics to unstick at the origin of resin
compaction and mass defects between the layers.
Aim and summary of the invention
30 The main aim of the present invention is therefore to
rectify such drawbacks by proposing a solution for
impregnation by vacuum liner ensuring uniform compaction of
the fibrous reinforcement, especially at the level of the
angles of flanges.
This aim is attained by an impregnation mandrel for
making a gas turbine casing made of composite material,
5 comprising:
an impregnation mandrel on which is intended to be held
a fibrous reinforcement formed by superposed layers of a
fibrous texture, the mandrel comprising a central annular wall
the profile of which corresponds to that of the casing to be
10 manufactured and two lateral flanges whereof the profiles
correspond to those of external flanges of the casing to be
manufactured;
compaction bars each comprising a corner intended Lo be
supported against the part of the fibrous reinforcement
15 covering the angles formed between the central wall and the
flanges of the mandrel, and a coupling flange intended to be
fixed on the corresponding flange of the mandrel;
a supple envelope forming a vacuum liner intended to be
applied at least to that part of the fibrous reinforcement
20 covering the central wall of the mandrel; and
means for injecting resin into a space delimited
between the vacuum liner and the mandrel at a longitudinal end
of the fibrous reinforcement and for extracting it at an
opposite end.
25 The compaction bars of the mandrel according to the
invention are positioned once the winding operation is
completed and before placing of the vacuum liner. These
compaction bars ensure uniform compaction of the part of the
fibrous reinforcement covering the angles of flanges prior to
30 setting the vacuum. In this way, any risk of formation of
resin mass between the layers of the fibrous reinforcement
during this operation for setting the vacuum can be prevented.
Also, the compaction bars are intended to be fixed
directly on the impregnation mandrel, which properly and
repeatedly controls the geometry of the external flanges of
the casing to be manufactured.
5 The mandrel preferably comprises at least one resin
injection orifice terminating inside the space delimited
between the vacuum liner and the mandrel at a longitudinal end
of the fibrous reinforcement, and at least one resin
extraction orifice placed at the longitudinal end of the
10 fibrous reinforcement opposite to where the resin injection
orifice terminates.
In this case, the resin injection orifice can be formed
in one of the flanges of the mandrel and the resin extraction
orifice can be formed in the other flange. Advantageously, the
15 resin injection orifice terminates at the corner of a socalled
injection compaction bar, whereas the resin extraction
orifice terminates downstream of the so-called extraction
opposite compaction bars.
The coupling flanges of the extraction compaction bars
20 may comprise grooves ensuring passage of the resin.
The vacuum liner can be intended to be also applied to
the compaction bars and be fixed tightly by its free ends to
the flanges of the mandrel.
The coupling flanges of the compaction bars are
25 preferably intended to be fixed tightly on the flanges of the
mandrel.
For each flange of the mandrel, there can be four
compaction bars and they can be put end to end angularly to
cover the total circumference of the mandrel..
30 Another aim of the invention is a winding machine of a
fibrous texture on an impregnation mandrel, comprising a takeup
mandrel on which a fibrous texture is intended to be
stored, produced by three-dimensional weaving, the take-up
mandrel having a substantially horizontal axis of rotation, an
impregnation mandrel such as defined previously, the
impregnation mandrel having a substantially horizontal axis of
rotation parallel to the axis of rotation of the take-up
5 mandrel, electric motors for driving the mandrels in rotation
about their respective axis of rotation, and a control unit of
the electric motors for driving the mandrels in rotation.
Brief description of the diagrams
10 Other characteristics and advantages of the present
invention will emerge from the following description, in
reference to the attached diagrams which illustrate an
embodiment devoid of any limiting character, in which:
Figure 1 is a schematic view and side elevation of a
15 blinding machine of a fibrous texture on an impregnation
mandrel according to the invention;
Figure 2 is a view of the impregnation mandrel of the
winding machine of Figure 1 during placing of the compaction
bars;
20 Figure 3 is a sectional view along 111-111 of Figure 2;
and
Figure 4 is a sectional view of the impregnation
mandrel of Figure 3 after placing of the vacuum liner.
25 Detailed description of the invention
The invention will now be described within the scope of
its application to the production of a fan casing in an
aeronautical engine with a gas turbine.
An example of a manufacturing process of such a fan
30 casing is described in document EP 1 961 923 which can be
referred to.
The casing is made of composite material with fibrous
reinforcement densified by a matrix. The reinforcement is made
of fibres such as carbon, glass, aramide or ceramic and the
matrix is made of polymer, for example epoxide, bismaleimide
or polyimide.
Briefly, the manufacturing process described in this
5 document consists of making a fibrous texture by threedimensional
weaving with chain take-up on a drum (hereinbelow
called take-up mandrel) having a profile determined as a
function of the profile of the casing to be manufactured.
The resulting fibrous texture is then transferred to
10 the mandrel of a resin injection mould (hereinbelow called
impregnation mandrel) the external profile of which
corresponds to the internal profile of the casing to be
manufactured.
While the preform is held on the impregnation mandrel,
15 impregnation is then done with resin. For this purpose, a
supple envelope (also called vacuum liner) is applied tightly
to the preform and the resin is injected into the resulting
mould. Impregnation is assisted by a difference in pressure
being set between the exterior and the interior of the mould
20 containing the preform (air vacuum). After impregnation, a
resin polymerisation step is carried out.
The invention applies to any type of winding machine
whereof the function is automated transfer of the fibrous
texture stored on the take-up mandrel to the impregnation
25 mandrel of the resin injection mould, such as shown in
Figure 1.
Reference could be made to patent application
FR 11 53212 (not yet published) which describes in detail the
structure and operation of such a machine.
30 Briefly, the winding machine 10 comprises a frame 12
supporting especially a take-up mandrel 14 and an impregnation
mandrel 100 according to the invention. These mandrels are
removable, that is, they can be dismantled from the frame.
The take-up mandrel 14 receives the fibrous texture 16
produced for example by three-dimensional weaving. It is borne
by a horizontal axle 18 one end of which is mounted to rotate
on the frame 12 of the winding machine and the other end is
5 coupled to the output shaft of an electric engine 20, for
example an electric motoreducer on alternating current.
The assembly constituted by the take-up mandrel 14, its
axle 18 and its electric engine 20 can translate relative to
the frame along the axis of rotation of the take-up mandrel.
10 This degree of liberty in translation of the take-up mandrel
creates alignment of this mandrel on the impregnation mandrel
prior to winding of the fibrous texture on the impregnation
mandrel.
The impregnation mandrel I00 of the winding machine is
15 intended to receive the fibrous texture stored on the take-up
mandrel, in superposed layers. In a way known per se, it has a
central annular wall 102 whereof the profile of the external
surface corresponds to that of the internal surface of the
casing to be made and two lateral flanges 104a, 104b whereof
20 the profiles correspond to those of the external flanges of
the casing at its upstream and downstream ends to enable it to
be mounted and linked to other elements.
The impregnation mandrel is borne by a horizontal axis
22 which is parallel to the axis of rotation 18 of the take-up
25 mandrel and whereof one end is mounted to rotate on the frame
12 of the winding machine and the other end is coupled to the
output shaft of an electric engine 24, for example an electric
motoreducer on alternating current.
A control unit 26 is connected to the electric motors
30 20, 24 of the two mandrels and controls the rotation speed of
each mandrel. More generally, this control unit controls the
assembly of operating parameters of the winding machine, and
especially the displacement in translation of the take-up
mandrel when motorised.
With such a machine, winding of the fibrous texture on
the impregnation mandrel is done as follows: the free end of
5 the fibrous texture of the take-up mandrel is first fixed on
the impregnation mandrel by means of a device for holding by
clamping described hereinbelow, then the engines for driving
the mandrels in rotation are activated and controlled by the
control unit so as to apply adequate winding tension on the
10 fibrous texture.
Winding of the fibrous texture in superposed layers on
the impregnation mandrel can then start and be executed in the
direction of rotation marked by arrow - F in Figure 1. By way of
example, it might be necessary to effect 4 turns 1/8 to
15 produce a fibrous reinforcement 28 having a thickness
conforming to the specifications of the casing to be
manufactured.
According to the invention, the impregnation mandrel
100 is provided with means ensuring impregnation by resin
20 under vacuum liner on completion of the winding operation.
More precisely, as shown in Figures 2 to 4, the
impregnation mandrel comprises so-called angular compaction
bars which are intended to be positioned on the mandrel at the
level of the parts of the fibrous reinforcement 28 covering
25 the angles formed between the central wall 102 and the flanges
104a, 104b of the latter.
These bars comprise a first series of compaction bars
106a intended to be mounted against the part of the fibrous
reinforcement covering the angle formed betvreen the central
30 wall of the mandrel and the flange 104a, and a second series
of compaction bars 106b intended to be mounted against the
part of the fibrous reinforcement covering the angle formed
between the central wall of the mandrel and the other flange
104b.
The compaction bars 106a, 106b of these series cover
the entire circumference of the mandrel and are sectored. So,
5 in the example illustrated in Figure 2, each series comprises
four compaction bars each extending over 90' approximately and
put end to end angularly to cover the total circumference of
the impregnation mandrel. Of course, the number of bars per
series could be different.
10 Each compaction bar 106a, 106b comprises a corner 108a,
108b which is intended to be supported against the part of the
fibrous reinforcement covering the angles formed between the
central wall 102 and the flanges 104a, 104b of the mandrel,
and a coupling flange 110a, llOb intended to be fixed on the
15 corresponding flange of the mandrel.
Placing the compaction bars on the impregnation mandrel
ensures uniform compaction of the fibrous reinforcement at the
level of the flange angles. This placing can be ensured by
using a specific tool of tension type, for example.
20 Once in place, the compaction bars are fixed on the
impregnation mandrel by means of their coupling flanges 110a,
llOb and by means for example of screws 112. This fixing is
made tight by the presence of O-ring joints 114 positioned
against an internal face of the coupling flanges about the
25 boreholes made for passage of screws and plugs 116 sealing the
openings made in the coupling flanges for passage of these
same screws.
A supple envelope 118 forming a vacuum liner is then
applied to at least that part of the fibrous reinforcement
30 covering the central wall of the mandrel. As shov~n in
Figure 4, this vacuum liner 118 is preferably applied at the
same time to the fibrous reinforcement at the level of the
central part of the mandrel, but also covers the compaction
bars 106a, 106b, at the level of its free ends, to be fixed
tightly on the flanges 104a, 104b of the mandrel. The material
used to make the vacuum liner 118 is for example nylon (the
choice of material will depend especially on the class of
5 temperature of the resin).
The impregnation mandrel further comprises means for
injecting resin into the resulting mould. For this purpose,
one of the flanges of the mandrel (here the flange 104a)
comprises at least one resin injection orifice 120 which
10 terminates inside a space 122 delimited between the corner
108a of a corresponding compaction bar 106a (also called
"injection compaction bar") and the corresponding flange 104a.
In this way, the injection of resin is done at the level of
one of the free ends of the fibrous reinforcement 28 held on
15 the mandrel.
The resin is extracted at the level of the opposite
flange (specifically here flange 104b). For this purpose, this
flange comprises one or more extraction orifices 124 which
terminate in a space delimited betvieen the free end opposite
20 the vacuum liner 118 and the flange 104b, this space being
situated downstream of the corresponding compaction bars 106b
(also called "extraction compaction bars"). Downstream here
means relative to the flow of the resin between the two
longitudinal ends of the fibrous reinforcement held on the
25 mandrel.
To allow the resin to pass from the fibrous
reinforcement 28 to the extraction orifice or the extraction
orifices 124, it is necessary for it to get over the
extraction compaction bars 106b. At the level of their
30 internal face, the coupling flanges 110b of the latter also
have a plurality of grooves 126 (see Figure 3) extending
radially outwards and dimensioned to allow such passage of
resin.
Also, it is evident that the extraction orifice or the
extraction orifices can be used to set up the vacuuming of the
liner 118 by creating a difference in pressure between the
exterior and the space delimited by the mandrel and the liner
5 containing the fibrous reinforcement. For this purpose, it
might be necessary to place vacuum drainage fabric between the
vacuum liner and the flange 104b of the mandrel in its part
downstream of the extraction compaction bars 106b (such fabric
prevents discontinuity of the vacuum as far as the extraction
10 orifices). Setting vacuum assists the resin injection
operation.
Once the vacuum is set, the resin is injected into the
mould formed by the impregnation mandrel covered by the vacuum
liner. On completion of this operation, a resin polymerisation
15 step is conducted as known per se.

Claims
1. An impregnation mandrel for making a gas turbine
casing made of composite material, comprising:
5 an impregnation mandrel (100) on which a fibrous
reinforcement (28) is intended to be held, formed by
superposed layers of a fibrous texture, the mandrel comprising
a central annular wall (102) whereof the profile corresponds
to that of the casing to be manufactured and two lateral
10 flanges (104a, 104b) the profiles of which correspond to those
of external flanges of the casing to be manufactured;
compaction bars (106a, 106b) each comprising a corner
(108a, 108b) intended to be supported against the part of the
fibrous reinforcement covering the angles formed between the
15 central wall and the flanges of the mandrel, and a coupling
flange (110a, 110b) intended to be fixed on the corresponding
flange of the mandrel;
a supple envelope (118) forming a vacuum liner intended
to be applied at least on that part of the fibrous
20 reinforcement covering the central wall of the mandrel; and
means (120, 124) for injecting resin into a space (122)
delimited between the vacuum liner and the mandrel at a
longitudinal end of the fibrous reinforcement and for
extracting it at an opposite end.
25
2. The mandrel according to Claim 1, comprising at
least one resin injection orifice (120) terminating inside the
delimited space between the vacuum liner and the mandrel at a
longitudinal end of the fibrous reinforcement, and at least
30 one resin extraction orifice (124) placed at the longitudinal
end of the fibrous reinforcement opposite to where the resin
injection orifice terminates.
3. The mandrel according to Claim 2, wherein the resin
injection orifice ~ (120) is formed in one of the flanges (104a)
of the mandrel and the resin extraction orifice (124) is
formed in the other flange (104b).
5
4. The mandrel according to in Claim 3, wherein the
resin injection orifice (120) terminates at the corner (108a)
of a so-called injection compaction bar (106a), whereas the
resin extraction orifice (124) terminates downstream of said
10 opposite extraction compaction bars (106b).
5. The mandrel according to in Claim 4, wherein the
coupling flanges (110b) of the extraction compaction bars
(106b) comprise grooves (126) ensuring passage of the resin.
15
6. The mandrel according to any one of Claims 1 to 5,
wherein in which the vacuum liner (118) is intended to be also
applied to the compaction bars (106a, 106b) and be fixed
tightly by its free ends to the flanges of the mandrel.
7. The mandrel according to any one of Claims 1 to 6,
wherein the coupling flanges (110a, 110b) of the compaction
bars (106a, 106b) are intended to be fixed tightly on the
flanges of the mandrel.
25
8. The mandrel according to any one of Claims 1 to 7,
wherein for each flange of the mandrel, there are four
compaction bars that are put end to end angularly to cover the
total circumference of the mandrel.
30
9. A winding machine (10) of a fibrous texture on an
impregnation mandrel, comprising:
a take-up mandrel (14) on which a fibrous texture (16)
is intended to be stored, produced by three-dimensional
weavlng, the take-up mandrel having a substantially horizontal
axis of rotation (18);
5 an impregnation mandrel (100) according to any one of
Claims 1 to 8, the impregnation mandrel having a substantially
horizontal axis of rotation (22) parallel to the axis of
rotation of the take-up mandrel;
electric motors (20, 24) for driving the r~~andrelsi n
10 rotation about their respective axis of rotation; and
a control mit (26) of the electric motors for driving
the mand~els in rotation.