Title of the invention
Impregnation clamping mandrel for making gas turbine
casings made of composite material
5 Background of the invention
The present invention relates to the general
field of gas turbine casings, and more particularly
holding casings of gas turbine fans for aeronautical
engines.
10 I11 a gas turbine aeronautical engine, a fan
casing 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
15 absorption for acoustic inlet treatment of the engine
and incorporates or supports a holding shield. The
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 ~.
20 through the casing and reaching other parts of the
aircraft.
Making a casing for holding a fan made of
composite 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
5 texture and densification of the fibrous reinforcement
by a matrix. According to this invention, the fibrous
texture is made by three-dimensional weaving with
evolutive thickness and is wound in several superposed
layers onto a mandrel having a central wall of profile
10 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 complet6d under vacuum prior
15 to polymerisation. The winding on 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, carrying out this process poses
20 the problem of holding the fibrous preform during its
winding on the mandrel. During this winding, sufficient
traction force should indeed be exerted on each layer
of fibrous texture to ensure effective compaction of
the letter. This requires in particular that the first
25 layer of fibrous texture which is wound on the mandrel
be correctly packed up against the latter before
successive layers are wound on.
For this purpose, document FR 2 945 573
discloses an impregnation mandrel in which the hooking
30 of the first layer of fibrous texture is done by a
removable plate fitted with points which penetrate the
layer of fibrous texture. Even though efficacious, this
type of hooking can have the risk of seeing the points
of the plate damage the fibrous preform if a too strong
winding tension is applied on the latter.
5 Aim and summary of the invention
The principal aim of the present invention is
therefore to rectify such drawbacks by proposing
mechanical holding of the first layer of fibrous
texture, which applies strong winding tension without
10 the risk of damaging the fibrous preform.
This aim is attained by an impregnation mandrel
for making gas turbine casings made of material
composite, the mandrel comprising an annular wall
whereof the profile of the external surface corresponds
15 to that of the internal surface of the casing to be
made, and two lateral flanges whereof the profiles
corresponds to those of external flanges of the casing
to be made, the mandrel also comprising, according to
the invention, a removable clamping device of a layer
20 of fibrous texture wound on the mandrel.
The clamping of the free end of the layer of
fibrous texture wound on the mandrel prevents any risk
of deterioration of the preform irrespective of the
winding tension applied to the latter. Also, this
25 clamping device is removable such that it can be
withdrawn prior to resin impregnation to prevent any
risk of degradation of the preform during the hot
polymerisation operation. Finally, holding the first
layer of fibrous texture on the mandrel is mechanical
30 (and not chemical) which ensures total safety on the
preform prior to resin impregnation.
The clamping device advantageously comprises a
removable plate intended to be positioned in a
corresponding recess made through the wall of the
mandrel, said plate comprising an external surface
5 whereof the profile is capable of reconstituting the
profile of the external surface of the mandrel and a
slot extending in position between the lateral flanges
of the mandrel and intended to receive a free end of
the layer of fibrous texture wound on the mandrel.
10 Such a clamping device preferably further
comprises a pad capable of exerting a clamping force on
the free end of the layer of fibrous texture wound on
the mandrel by means of tightening screws. The
tightening screws ark advantageously accessible from
15 the interior of the mandrel.
The plate of the clamping device can comprise
fixing flanges which are xntended in position to be
fixed on the annular wall of the mandrel by means of
fixing screws.
20 Also, the plate of the clamplng device can
comprise a grip accessible from the interior of the
mandrel when the clamping plate is in position.
Another aim of the invention is a winding
machine of a fibrous texture on an impregnation
25 mandrel, comprising a take-up mandrel on which a
fibrous texture produced by three-dimensional weaving
is intended to be stored, the take-up mandrel having an
axis of rotation substantially horizontal, an
impregnation mandrel such as defined previously and on
30 which the fibrous texture stored on the take-up mandrel
is intended to be wound in superposed layers, the
impregnation mandrel having a substantially horizontal
axis of rotation parallel to the axis of rotation of
the take-up mandrel, electric motors for driving the
mandrels in rotation about their respective axis of
rotation, and a control unit of the electric motors
5 driving the mandrels in rotation.
Another aim of the invention is an impregnation
method of a fibrous texture for making gas turbine
casings made of material composite, comprising winding
a first layer of fibrous texture on an impregnation
10 mandrel such as defined previously, maintaining a free
end of the first layer of fibrous texture on the
impregnation mandrel by means of the clamping device,
winding other layers of fibrous texture on the
impregnation mandrel, withdrawal of the clamping devic6
15 and its replacement by a sealing plug, and impregnating
the fibrous texture wounded on the mandrel par resin
injection.
Brief description of the drawings
20 Other characteristics and advantages of the
present invention will emerge from the follot~ing
description, in reference to the attached diagrams
which illustrate an embodiment devoid of any limiting
character, in which:
25
Figure 1 is a schematic view and side elevation
of a winding machine of a fibrous texture on an
impregnation mandrel according to the invention;
Figure 2 is a perspective view of the
30 impregnation mandrel of Figure 1;
Figure 3 is a sectional view along 111-111 of
Figure 2; and
Figure 4 is a view corresponding to Figure 3
showing the impregnation mandrel on completion of
winding.
5 Detailed description of the invention
The invention nil1 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
10 fan 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
reinforceinent is made of fibres such as carbon, glass,
15 aramide or ceramic .and the matrix is made of polymer,
for example epoxide, bismaleimide or polyimide.
Briefly, the manufacturing process described in
this document consists of making a fibrous texture by
~. three-dimensional weaving with chain.take-up on a drum
20 (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 the mandrel of a resin injection mould
25 (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, impregnation is then done with resin. For this
30 purpose, .an envelope is applied 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 containing the preform. After impregnation, a
resin polymerisation step is carried out.
The invention applies to any type of winding
5 machine whereof the function is automated transfer of
the fibrous texture stored on the take-up mandrel to
the impregnation mandrel of the resin injection mould,
such as shown in Figure 1.
Reference could be made to patent application
10 FR 11 53212 (not yet published) which describes in
detail the structure and operation of such a machine.
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.
15 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
20 which 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 20, for example an
electric motoreducer on alternating current.
The assembly constituted by the take-up mandrel
25 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. This degree of liberty
in translation of the take-up mandrel creates alignment
of this mandrel on the impregnation mandrel prior to
30 winding of the fibrous texture on the impregnation
mandrel.
The impregnation mandrel 100 of the blinding
machine is 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
5 whereof the profile of the external surface corresponds
to that of the internal surface of the casing to be
made and two lateral flanges 104 vlhereof the profiles
correspond to those of the external flanges of the
casing at its upstream and downstream ends to enable it
10 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 mandrel and whereof one end
is mounted to rotate on the frame 12 of the vlinding
15 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 20, 24 of the two mandrels and controls the
20 rotation speed of each mandrel. More generally, this
control unit controls all the 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
25 texture on the impregnation mandrel is done as follows:
the free end of 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
30 in rotation are activated and controlled by the control
unit so as to apply adequate winding tension on the
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
5 necessary to effect 4 turns 1/8 to produce a fibrous
reinforcement having a thickness conforming to the
specifications of the casing to be manufactured.
According to the invention, the impregnation
mandrel 100 comprises a removable device for clamping
10 the free end 28 of the first layer 16a of fibrous
texture which is wound on the impregnation mandrel.
More precisely, as shown in Figure 2, this
device comprises especially a plate 106 which ensures
clamping of this free end of fhe first layer of fibrous
15 texture.
This plate 106 is removable and is intended to
be positioned at the start of the winding operation in
a corresponding recess 108 through the annular wall 102
of the mandrel. For this purpose, the plate of the
20 clamping device comprises two opposite fixing flanges
110 which are fixed on the annular wall of the mandrel
by means of fixing screws 112, and sealing joints 114
which can also be inserted between the flanges and the
annular wall of the mandrel.
25 The plate 106 can also comprise a grip 116
which makes gripping easier. It is evident that this
grip and the fixing screws 112 are accessible fromthe
interior of the impregnation mandrel.
The external surface 118 of the plate 106 of
30 the clamping device is profiled so as to reconstitute
the profile of the external surface of the annular wall
102 of the impregnation mandrel when it is mounted on
the latter. . ,
The pLate 106 of the-clamping device also has a
slot 120 extending transversally between the two
5 lateral flanges 104 of the mandrel, this slot being
dimensioned to receive the free end 28 of the first
layer 16a of fibrous texture wound on the mandrel to
hold it by clamping.
Also, a pad 122 is housed inside the plate at
10 the level of the slot 120, this pad being capable of
being gripped tightly against the free end 28 of the
first layer 16a of fibrous texture by way of tightening
screws 124 accessible from the interior of the mandrel
(Figure 3). So, once the end of the first layer of
15 fibrous texture is inserted into the slot of the plate,
the tightening screws 124 are screwed so as to exert
clamping force of this end of layer of fibrous texture
between the pad 122 and the annular wall 102 of the
plate 106. . .
20 It is evident that only that part 28a of the
end 28 of the first layer 16a of fibrous texture which
is intended to reconstitute the internal surface of the
casing to be made is held by clamping on the
impregnation mandrel (the parts of this end of the
25 first layer of fibrous texture which are intended to
reconstitute the external flanges of the casing to be
made are not). In fact, no winding tension is applied
at the level of its parts of the fibrous texture during
its winding on the impregnation mandrel, such that it
30 is unnecessary to provide holding for the latter. Also,
this solution has the advantage of simplifying the
holding device. - -
Also, so that only the part 28a of the end 28
of the first layer of fibrous texture which is intended
to reconstitute the internal surface of the casing to
be made is inserted into the slot 120 of the plate 106
5 to be held there by clamping, it is first necessary to
cut out this free end 28 as shown in Figure 1,
especially at the level of the parts 28b which will
reconstitute the external flanges of the casing.
Once all the layers of fibrous texture are
10 wound on the impregnation mandrel, the clamping device
is withdrawn prior to the resin impregnation operation.
For this purpose, the tightening screws 124 of the
washer, as well as the fixing screws 112 of the plate
106 are unscrewed' so as to release the plate from its
15 recess 108 in the impregnation mandrel.
Once the plate 106 is withdrawn, the free end
of the first layer 16a of fibrous texture which
projects inside the mandrel can be cut off, for example
using a cutter blade. Alternatively, this free end can
20 be left in place, which consequently requires adapting
the geometry of the sealing plug described hereinbelow,
so as to integrate the overthickness attached to this
layer.
A sealing plug 200 such as that shown in
25 Figure 4 is then positioned in the recess 108 of the
impregnation mandrel in place of the plate 106 of the
clamping device. Such a plug is overall identical to
the clamping plate, except that it has no slot or pad.
In particular, the latter has an external surface 204
30 reconstituting the profile of the external surface of
the annular wall of the mandrel and can be fixed on the
latter by means of fixing flanges 208 and screws 210
(sealing joints 212 can also be inserted). The plug
also comprises a grip 214 accessible from the interior
of the mandrel. Once the plug 200 is in place and fixed
on the impregnation mandrel, the resin impregnation
5 operation can start.

Claims
1. An impregnation mandrel (100) for making gas
turbine casings made of composite material, the mandrel
5 comprising an annular wall (102) the profile of the
external surface of which corresponds to that of the
internal surface of the casing to be made, and two
lateral flanges (104) the profiles of which correspond
to those of external flanges of the casing to be made,
10 characterised in that it further comprises a removable
clamping device of a layer of fibrous texture wound on
the mandrel.
2. The mandrel according to Claim 1, wherein
15 the clamping device comprises a removable plate (106)
intended to be positioned in a corresponding recess
(108) made through the wall (102) of the mandrel, said
plate comprising an external surface whereof the
profile is capable of reconstituting the profile of the
20 external surface of the mandrel and a slot (120)
extending in position between the lateral flanges of
the mandrel and intended to receive a free end (28) of
the layer of fibrous texture wound on the mandrel.
25 3. The mandrel according to Claim 2, wherein
the clamping device further comprises a pad (122)
capable of exerting a clamping force on the free end of
the layer of fibrous texture wound on the mandrel by
means of tightening screws (124).
30
4. The mandrel according to Claim 3, wherein
the tightening screws (124) are accessible from the
interior of the mandrel.
5 5. The mandrel according to any one of Claims 2
to 4, wherein the plate (106) of the clamping device
comprises fixing flanges (110) which when in position
are intended to be fixed on the annular wall of the
mandrel by means of fixing screws (122).
10
6. The mandrel according to any one of Claims 2
to 5, wherein the plate (106) of the clamping device
comprises a grip (116) accessible from the interior of
the mandrel when the clamping plate is'in position.
15
7. A winding machine (10) of a fibrous texture
on an impregnation mandrel, comprising:
a take-up mandrel (14) on which a fibrous
texture (16) produced by three-dimensional weaving is
20 intended to be stored, the take-up mandrel having a
substantially horizontal axis of rotation (18);
an impregnation mandrel (100) according to any
one of Claims 1 to 6 on which the fibrous texture
stored on the take-up mandrel is intended to be wound
25 in superposed layers, 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
mandrels in rotation about their respective axis of
30 rotation; and
a control unit (26) of the electric motors
driving the mandrels in rotation.
' 8 . An impregnation method of a fibrous texture
for making gas turbine casings -made of material
composite, comprising:
5 vrinding a first layer (16a) of fibrous .texture
on an impregnation mandrel according to, any one of
claims 1 to 6;~
maintaining a free end (28) pf the first layer
of fibrous texture on the impregnation mandrelby means
10 of the clamping device;
winding other layers of fibrous texture on the
impregnation mandrel;
withdrabral of the clamping device and its
replacement by a sealing plug (200); and
15 impregnating the fibrous 'texture wounded on the
mandrel par resin injection.