METHOD FOR MANUFACTUIUNG AN INTEGRAL ROTATIONALLY
SYMMETRICAL METAL PART FROM COMPOSITE FIBROUS STRUCTURES
The present invention relates to a method for manufacturing an integral rotationally
symmetrical metal part from composite fibrous structures in the form of fibers, fiber laps,
fiber fabrics and similar, coated with metal.
The importance of composite materials in the partial or total production of parts has emerged
in recent years, in many technical fields, notably aeronautics, space, military, automobile, etc.,
because of the optimization of the resistance of such materials, for minimal weight and bulk.
As a reminder, such a structure comprises metal composite fibers composed of a metal alloy
matrix, by example titanium Ti alloy, within which extend fibers, for example ceramic fibers
of silicon carbide Sic. Such fibers exhibit a tensile strength much greater than that of titanium
(typically, 4000 MPa compared to 1000 m a ) . It is therefore the fibers which take up the
forces, the metal alloy matrix acting as a binder for the part, and providing protection and
insulation for the fibers, which must not come into contact with one another. Furthermore, the
ceramic fibers are resistant to erosion, but necessarily have to be reinforced with metal.
These composite materials can be used to produce annular, rotationally symmetrical gas
turbine parts for aircraft or other industrial applications, such as rings, shafts, cylinder bodies,
casings, spacers, monolithic part reinforcements such as blades, etc.
The known methods for manufacturing such integral rotationally symmetrical parts consist in
superposing, around a rotary cylindrical mandrel, successive fibrous structures (fibers, fiber
lap or fiber fabric) and then arranging the composite fibrous structures, wound and removed
from the mandrel in a specific receiving outfit for them to be heat treated and to ultimately
obtain the rotationally symmetrical part made of composite material.
For the rotationally symmetrical part to be particularly rigid and withstand forces in different
- directions, notably torsional forces, one of the superposed fibrous structures is oriented in a
first winding direction relative to the longitudinal axis of the mandrel, then the other fibrous
structure is wound on the preceding one in a second winding direction different from the first,
so as to- obtain two composite fibrous structures that have crossed winding directions.
However, it has been noted that crossing over the metal-coated ceramic composite fibers of
the two fibrous structures superposed one on top of the other could create excessive local
stresses which occur during the cooling of the part, after the creep of the thin metal cladding
of the fibers of the structures. These excess stresses drastically reduce the mechanical
characteristics of the part.
The aim of the present invention is to remedy these drawbacks.
To this end, the method for manufacturing an integral rotationally symmetrical part by
superposition, around a rotary cylindrical mandrel, of at least two metal-coated composite
fibrous structures, respectively inner and outer, wound in first and second directions crossed
on said mandrel, is noteworthy in that it consists:
- in arransing: around the inner fibrous structure constructed on the mandrel in the first
winding direction, at least one layer of metal wire,
- in winding, on said layer of metal wire, the outer fibrous structure in the second winding
direction,
- in placing the preform of said part, formed by the fibrous structures and the layer of metal
wire, in a receiving outfit to apply to the preform a hot isostatic compaction or isothermal
forging treatment, and
- in extracting the treated preform from the outfit, and if appropriate, machining the treated
preform to obtain said part.
Thus, by virtue of the invention, the layer of metal wire serves as interface between the
superposed and crossed fibrous structures and increases the metal thickness between the
structures, so that the excess stresses between the composite fibers of the structures no longer
occur.
Advantageously, the metal wire is obtained, for example, by wire drawing and is of the same
nature as the metal of the composite fibrous structures, so that there is obtained, after passage
through the outfit, an intermediate and uniform metal layer that has an appropriate thickness
between the fibers of the structures. However, the wire could be obtained other than by wire
drawing. A "metal wire" should be understood to mean equally one and the same continuous
wire and a plurality of wires placed end to end. The metal wire can also be individual or take
the form of a lap or a band of a plurality of parallel or interlaced wires, a cable, a fabric of
unidirectional wires, etc., without departing from the framework of the invention.
Preferably, the superposed winding layers of the metal wire and of the fibrous structures are
made cold, at ambient temperature, which does not require any complex installation for the
implementation of the relevant steps of the method.
Furthermore, the metal wire is wound substantially orthogonally to the longitudinal axis of the
rotary cylindrical mandrel to form the layer of contiguous turns.
To insulate and protect the inner fibrous structure from the outside, at least one layer of metal
wire, on which the inner fibrous structure is subsequently wound, can be arranged around said
cylindrical mandrel, before the placement of the inner fibrous structure.
For the same purpose, at least one layer of metal wire can be arranged around the outer
fibrous structure, so that the part obtained has, on the surface, a thickness of outer and inner
metal layers.
According to an exemplary embodiment, the first winding direction of the inner fibrous
structure is oriented at an angle relative to the longitudinal axis of the cylindrical mandrel, the
second winding direction of the outer fibrous structure then being oriented symmetrically to
the first relative to a radial direction of the mandrel, at right angles to its longitudinal axis. For
the range of values, if the winding direction of the inner fibrous structure is between 30"- 60"
relative to the longitudinal axis of the mandrel, the winding direction of the outer structure
will be between 30"- 60" + W2.
Tn this example, the inner and outer fibrous structures inay be in the form of individual and
parallel fibers wound in succession around the mandrel, or in the form of laps or strips of
parallel fibers, or in the form of fabrics of parallel fibers, said structures being arranged
crossed on the mandrel.
According to another exemplary embodiment, the first winding direction of the inner fibrous
structure is parallel to the longitudinal axis of the cylindrical mandrel, the second winding
direction of the outer fibrous structure then being oriented at an angle relative to the
longitudinal axis of the mandrel.
In this example, the inner fibrous structure may be in the form of a fabric of mutually parallel
fibers wound around the cylindrical mandrel parallel to its longitudinal axis, the outer fibrous
structure being able to be any structure but, obviously, with the fibers oriented at an angle
relative to those of the inner structure which are parallel to the mandrel.
Moreover, the metal wires used can have different diameters, and layers with a plurality of
superposed windings of these wires may be provided in alternation with the superposed
fibrous structures, the number of which can be greater than two.
The figures of the appended drawing will give a clear understanding as to how the invention
can be produced. In these figures, identical references designate similar elements.
Figures 1, 2, 3, 4A, 4B, 4C1, 4C2, 5, 6A, 6B and 7 schematically show the main steps of the
method according to the invention, for manufacturing m integral rotationally symmetrical
part from composite fibrous structures, figures 4A, 4B, 4C1 and 4C2 presenting various
possible outer fibrous structures used after the method step illustrated in figure 3, while
figures 6A and 6B schematically represent perform treatment outfits for obtaining the part.
The aim of the method is to manufacture an annular integral rotationally symmetrical part 1,
illustrated in figure 7, solely fiom elongate elements in the form of wires, fibers or similar, as
will be seen hereafter.
For this, the method consists in using a rotary cylindrical mandrel 2 of longitudinal axis X and
in first of all winding, around the lateral surface 3 thereof, in a first step illustrated in figure 1,
at least one metal wire 4. Given the application of the part 1 to the aeronautical field, the
metal wire 4 is produced notably in a titanium alloy of TA6V or 6242 type to provide thermomechanical
resistance and lightness, and it is obtained in this non-limiting example by wire
drawing so as to be able to be available in spool or reel form from which the wire is drawn.
Dimensionally, its diameter depends on the part to be obtained and can, for example, be of the
order to a few tenths of a millimeter.
In the example illustrated in figure 1, the drawn metal wire 4 is taken from a spool which is
not represented and is driven, substantially perpendicularly to the axis X, around the lateral
surface 3 of the cylindrical mandrel 2 over a predetermined extent corresponding to the length
that is to be obtained, after manufacture, for the rotationally symmetrical part 1, by thus
forming a plurality of contiguous turns 5, and over a predetermined plurality of superposed
layers 6.
Figure 2 shows the three layers 6 formed by the windings of contiguous turns 5 of the same
metal wire 4 around the mandrel. It would also be possible to use a metal wire 4' such as that
shown in cross section in figure 1, with a different diameter, less in this case than the diameter
of the metal wire 4. This is to show that it is possible to wind metal wires that have distinct
diameters.
The method continues with a second step shown in figure 2 and consisting in arranging a
composite fibrous structure 7 around the drawn metal wire 4.
In this example, the composite fibrous structure 7 takes the form of a fabric 8 of fibers 9
joined together in parallel and made of ceramic (Sic) or of a similar material, coated with
metal. The latter and the metal of the drawn wire are of identical nature (as an example, of
titanium alloy of TA6V or 6242 type) to optimize the subsequent step of the method
concerning the hot isostatic compaction or isothermal forging operation. The fabric 8 of the
fibrous structure 7, qualified as inner, since it is turned toward the mandrel, is wound around
the metal wire 4 so that the fibers 9 are arranged parallel to the longitudinal axis X of the
mandrel 2 (with a zero helix angle), thus defining a first direction Dl of orientation of the
fibers of the fabric 8.
As figure 2 shows, a single layer 10 of the fabric 8 is formed around the wire 4. Obviously, a
winding of a plurality of layers 10 could be provided from the same fabric, even from one or
more other distinct fabrics wound concentrically.
Then, according to a third step of the method illustrated in light of figure 3, a drawn metal
wire 11 which originates from a spool which is not represented and which is fed in
substantially orthogonally to the longitudinal axis X of the rotary cylindrical mandrel 2, is
arranged around the fabric 8 of the inner composite fibrous structure 7.
The metal wire 11 forms a single layer 12 of contiguous turns 13 around the fabric 8. A
winding of a plurality of layers is once again possible, dependent on the diameter of the wire
used and on the separation to be provided between the inner composite fibrous structure 7 and
a then outer composite fibrous structure 14 to be superposed as will be see hereinbelow.
The drawn metal wire 11 can be the same (diameter, nature) as that used to form the layers 6
on the mandrel 2 and originate from the same spool. However, it could also have a different
diameter.
By virtue of the placement, as inner fibrous structure 7, of a fabric 8 with ceramic fibers 9
parallel to the longitudinal axis X of the mandrel 2, a number of possibilities can be envisaged
with regard to the outer fibrous structure 14 to produce, at this stage, a preform E of the
integral part to be obtained 1, and these possibilities are shown in figures 4A, 4B, 4C1 and
4C2.
As figure 4A shows, the outer fibrous structure 14 is made up of ceramic composite fibers 15,
coated with metal, that may or may not be identical to the preceding fibers. These fibers 15
are wound in succession around the turns 13 of the layer 12 of intermediate metal wire 11,
which is located, according to the invention, between the two fibrous structures 7 and 14. The
fibers 15 are contiguous and oriented in a second direction D2 relative to the axis X of the
mandrel 2, forming a helical angle A relative thereto. Thus, the wound fibers 15 and the fibers
9 of the fabric 8 have different respective directions of orientation Dl and D2 that are crossed
to allow for the production of rigid. integral. composite rotationally sym~netricalp arts. Some
of the fibers 15 are only partially represented.
The number of wound fibers 15 is variable and is a function of the helical angle A to be given,
which is, for example, of the order of 30" to 60°, and of the diameter of the fibers. A single
layer 16 of the fibers 15 is made around the metal wire 1 1. However, a plurality of layers can
be envisaged.
Thus, at this stage of the manufacturing method, the two inner 7 and outer 14 fibrous
structures are not in direct contact with one another, being separated by the layer of winding
of the intermediate drawn metal wire 11 serving as interface, in order to eliminate any
excessive stress that might occur between them during the cooling of the preform E formed by
the structures and the metal wires.
Instead of the individual composite fibers 15, the outer fibrous structure 14 may be made up
of a successive winding of laps or strips 17 each made up of parallel composite fibers 18 (six
in this example), that is to say, having a core made of ceramic or of a similar material coated
with metal, preferably identical to the drawn wire 11. To keep the fibers 18 of a lap 17
mutually parallel, transversal metal weaving wires 19, of identical nature to the drawn wire,
are provided at regular intervals. Here again, the number of laps 17 to cover the layer 12 of
intermediate metal wire 11 is dependent on the width of the lap and on the helical angle A
thereof relative to the winding axis X of the rotary cylindrical mandrel 2. The helical angle A
of the laps defines the second direction D2 of the outer fibrous structure 14, crossing the
direction Dl of the inner fibrous structure 7. It can be seen, in figure 4B, that two successive
identical laps 17 are used to form a single layer 20 of the outer fibrous structure 14. More than
one layer 20 could obviously be envisaged. And it goes without saying that the outer fibrous
structure 14 covers all of the layer of metal wire 11.
According to another design shown in figures 4C1 and 4C2, the outer fibrous structure 14
takes the form of a fabric 21 with metallic composite fibers 22, assembled together in parallel.
In the example of figure 4C1, the fibers 22 are oriented obliquely relative to the perpendicular
sides 23, 24 of the fabric 21 in the form of a rectangular strip. In this way, when the fabric 21
is offered up by its corresponding side 23 (small side) parallel to the longitudinal axis X of the
cylindrical mandrel 2, it is wound, by the rotation of the latter, over the layer 12 of
intermediate drawn wire 11 and these oblique parallel composite fibers 22 form the desired
helical angle A defining the second direction D2 of the outer fibrous structure 14, crossed
with the first direction Dl of the inner fibrous structure 7. The dimension of the fabric 21 is
sufficient to cover all of the layer of drawn wire. A layer 25 (or a plurality of layers if
necessary) of fabric 21 is thus wound on the intermediate drawn wire 11.
In the example of figure 4C2, the fibers 22 are parallel to the side 23 of the fabric 21 to be
wound and are linked together by wires 27. Also, to have a direction of orientation D2 of the
fibers that is different from that of Dl of the inner structure, the fabric 21 itself is offered up
obliquely by one of its corners 26 relative to the rotary cylindrical mandrel 2, so as to fonn the
desired helical angle A. Thus, the parallel fibers 22 of the fabric 21 are wound around the
layer 12 of drawn metal wire 11 in the desired second direction D2, crossed with the first
direction Dl of the inner fibrous structure 7, parallel to the axis X of the cylindrical mandrel
2. The dimension of the fabric 21 is such that it makes it possible to cover all of the layer 12
of drawn wire by the winding of said fabric over one or more layers 25.
Thus, whatever the solutions retained, the two fibrous structures 7 and 14 have directions Dl,
D2 that are crossed and are separated from one another by at least one layer 12 of contiguous
turns 13 of the metal wire 11 acting as interface, in accordance with the invention. As for the
successive layers making up the two fibrous structures 7 and 14, their fibers are always
parallel from one layer to another with an orientation Dl or D2.
At this stage, as figure 5 shows, a subsequent step of the method consists in winding, on the
outer fibrous structure 14, at least one layer 28 of drawn metal wire 29 which can be taken
from the same feed spool as previously. Thus, a winding with contiguous turns 30 of the wire
29, performed substantially orthogonally to the axis X of the cylindrical mandrel 2, is
obtained (as a reminder, wire andlor fabric of metal wires).
Obviously, before this subsequent step, other superposed fibrous structures could be arranged
by taking care to alternate between them according to the invention, intermediate layers of
metal wire.
A preform E of the rotationally symmetrical part to be produced is obtained, which is
constructed only from drawn metal wires 4, 11, 29 and inner and outer structures 7, 14 with
composite fibers in individuals, lap, fabric or other form.
Then, as figure 6 shows, the preform E is transferred to a compaction outfit 3 1, schematically
represented, where the hot isostatic compression step (CIC) is performed in an isothermal
press or in an autoclave (the choice depending in particular on the number of parts to be
produced).
However, before its transfer, there can be a step of linking or securing the windings of the
metal wire to ensure the cohesion of all of the superposed layers of turns during the transfer to
the compaction station. For this, a welding step can be performed, for example an electrical
spot welding, on the windings of the visible inner and outer turns. Instead of the welding, foil
or leaf, not represented, could be arranged to hold in place the windings of the preform E,
welded or not. The latter, if made of a compatible material may they be involved in the
manufacture of the part.
After the preform E has been transferred and placed in the vacuum press outfit 3 1, figure 6A,
more particularly in an open cylindrical receptacle 32 of the press, the reception volume of
which, defined by its walls 33, corresponds to that of the part to be obtained, the receptacle is
closed by a cover 34 of a shape complementing the opening of the receptacle and the
transversal face of the preform E facing it.
Under the action of the compression exerted by the plates of the press symbolized by the
arrows F on the outfit, and at an appropriate high temperature, the identical metal of the
drawn wires 4, 11, 29 and of the cladding of the composite fibers of the structures 7, 14
become pasty eliminating all the empty spaces between the compressed turns, and ultimately
densifying the part being obtained by the displacement of the cover relative to the receptacle,
without acting on the silicon carbide matrices of the fibers.
In the variant represented in figure 6B of the autoclave outfit 31, the receptacle 32 and the
cover 34 with the preform E inside are placed in a deformable pocket 36 made of mild steel
which is then introduced into the autoclave of the outfit 3 1. As an example, this autoclave is
raised to an isostatic pressure of 1000 bar and a temperature of 940°C (for TA6V). so that all
of the pocket 36 is deformed, arrows F1, by shrinking through the evacuation of the air
expelled through the hole 37 and is pressed against the receptacle 32 and the cover 34 which,
in their turn, compress, under a uniform pressure, the windings of wires and fibers until the
metal of which they are made (diffusion welding) creeps, as previously.
Thus, after the CIC treatment, cooling and removal from the receptacle have stopped, the
composite integral rotationally symmetrical part 1 is obtained, represented in figure 7, which
is made of titanium alloy of TA6V or 6242 type, with, at its core, the ceramic matrices
(silicon carbide, for example) of the fibers 9-15 or 18 or 22 forming crossed reinforcing
inserts, but separated by the metal layer derived from the intermediate wire, and the thickness
of which is such that it avoids the appearance of stress between the crossed, superposed
ceramic fibers. The part 1 can obviously be subjected machining operations after the CIC
treatment.
Obviously, the direction of orientation of the fibers of the inner structure could be different
from that described above (parallel to' the axis of the mandrel), in the same way that the
choice of a fabric as inner fibrous structure is in no way mandatory, any other choice being
able to be envisaged. The same applies for the outer fibrous structure. It should also be
specified that the steps of winding of the wires and of the fibrous structures are performed at
ambient temperature without having to use a complex installation.
As examples, the coated composite fibers can be, in addition to SiClTi as described above,
made of SiCIAI, SiCISiC, SiCB, etc ...
Dimensionally, the minimum radius of the mandrel is a function of the diameter of the metal
wire and should be greater than the latter. The length of the part, for its part, can reach several
meters if necessary.

CLAIMS.
1. A method for manufacturing an integral rotationally symmetrical part by superposition,
around a rotary cylindrical mandrel (2), of at least two metal-coated composite fibrous
structures, respectively inner (7) and outer (14), wound in first and second directions crossed
on said mandrel, characterized in that it consists:
- in arranging, around the inner fibrous structure (7) constructed on the mandrel (2) in the first
winding direction @I), at least one layer of metal wire (1 I),
- in winding, on said layer of metal wire (1 I), the outer fibrous structure (14) in the second
winding direction @2),
- in placing the preform (E) of said part, formed by the fibrous structures (7, 14) and the layer
of metal wire (1 I), in a receiving outfit (3 1) to apply to the preform a hot isostatic compaction
or isothermal forging treatment, and
- in extracting the treated preform from the outfit, and if appropriate, machining the treated
preform to obtain said part (1).
2. The method as claimed in claim 1, in which the metal wire (11) is obtained by wire
drawing and is of the same nature as that of the inner (7) and outer (14) composite fibrous
structures.
3. The method as claimed in one of the preceding claims, in which the superposed winding
layers of the metal wire (1 1) and of the fibrous structures (7, 14) are made cold, at ambient
temperature.
4. The method as claimed in one of the preceding claims, in which the layer (12) of metal
wire (1 1) is wound substantially orthogonally to the longitudinal axis of the rotary cylindrical
mandrel (2).
5. The method as claimed in one of the preceding claims, in which at least one layer of metal
wire (4), on which the inner fibrous structure (7) is subsequently wound, is arranged around
said cylindrical mandrel (2), before the placement of the inner fibrous structure (7).
6. The method as claimed in one of the preceding claims, in which at least one layer of metal
wire (29) is arranged around the outer fibrous structure (14).
7. The method as claimed in one of the preceding claims, in which the first winding direction
(Dl) of the inner fibrous structure (7) is oriented at an angle relative to the longitudinal axis
(X) of the cylindrical mandrel (2), the second winding direction @2) of the outer fibrous
structure (14) being oriented symmetrically to the first relative to a direction at right angles to
the longitudinal axis of the mandrel.
8. The inethod as claimed in the preceding claim, in which the inner (7) and outer (14) fibrous
structures are in the form of individual and parallel fibers
(15) wound in succession around the mandrel, or in the form of laps or strips (17) of parallel
fibers, or in the form of fabrics (21) of parallel fibers, said structures being arranged crossed
on the mandrel.
9. The method as claimed in one of claims 1 to 6, in which the first winding direction (Dl) of
the inner fibrous structure (7) is parallel to the longitudinal axis (X) of the ~~lindrical'mandrel
(2), the second winding direction @2) of the outer fibrous structure (14) being oriented at an
angle relative to the longitudinal axis of the mandrel.
10. The method as claimed in the preceding claim, in which the inner fibrous structure (7) is
in the form of a fabric of mutually parallel fibers wound around the cylindrical mandrel (2)
parallel to its longitudinal axis, the outer fibrous structure (14) having the fibers oriented at an
angle relative to those of the inner structure which are parallel to the mandrel.