WO2023156728A1

WO2023156728A1 - Method for manufacturing an instrumented strand

Info

Publication number: WO2023156728A1
Application number: PCT/FR2023/050190
Authority: WO
Inventors: Marc WARIS; Adrien TOUZE; Marc-Antoine COLOT
Original assignee: Safran
Priority date: 2022-02-18
Filing date: 2023-02-13
Publication date: 2023-08-24

Abstract

The present invention relates to a method for manufacturing an instrumented strand (1), intended for a textile operation for forming a fibrous preform of a part made of composite material. The method comprises: • unreeling at least one wire-based detection element (5) which is able to transmit a physical signal, with reinforcing wires (104; 108) being attached around said at least one unreeling wire-based detection element so as to form a preform (110) of the instrumented strand; and • depositing a retaining binder (111) on the instrumented strand preform obtained in this way, so as to obtain the instrumented strand.

Description

Title of the invention: Process for manufacturing an instrumented strand

Technical area

The invention proposes the manufacture of a strand provided with a detection element intended to undergo a textile operation with the aim of forming a fibrous preform of a composite material part and its applications for checking the preform or the part.

Prior technique

Structural Health Monitoring (SHM) aims to maintain and extend the life of structural parts, detect and predict their failures. Current techniques typically implement instrumentation on the surface of the part, once its manufacture has been completed, by installing gauges and most often temporarily. This instrumentation is limited in particular in that it does not make it possible to control the step of forming the matrix, carried out for example by injection molding by resin transfer (“Resin Transfer Molding”; “RTM”). Other techniques offer instrumentation at the heart of the material by eliminating a part or by modifying the textile architecture of the reinforcement in order to be able to install the instrumentation. These techniques are not entirely satisfactory because they can have an impact on the mechanical strength of the manufactured part.

Disclosure of Invention

According to a first aspect, the invention relates to a method for manufacturing an instrumented strand intended for a textile operation for the formation of a fibrous preform of a part made of composite material, comprising:

- a scrolling of at least one wired detection element capable of transmitting a physical signal, reinforcing threads being attached around said at least one wired detection element in scrolling mode so as to form a preform of the strand instrumented, and

- depositing a holding binder on the preform of the instrumented strand thus obtained so as to obtain the instrumented strand.

The strand manufactured according to the invention makes it possible to instrument the material directly during the textile operation of forming the fiber preform with a minimal impact on the textile properties, such as the volume rate of fibers or the weaving weave for the case of a woven preform. The mechanical strength of the part is thus not altered due to the instrumentation. Further, it becomes possible to perform control during the matrix forming step. The strand manufactured according to the invention allows durable instrumentation throughout the life cycle of the part, both during its manufacture and during its period of service. Furthermore, the fact of attaching the reinforcing threads around the scrolling detection element makes it possible to avoid undulations of the latter and to ensure that it extends substantially straight in the instrumented strand, in order to avoid any risk of damaging it.

In an exemplary embodiment, the added reinforcing threads comprise a first set of reinforcing threads made of a first material, and a second set of reinforcing threads made of a second material different from the first material. Such a feature makes it possible to provide a strand with hybrid reinforcing threads, improving the performance of the latter.

In particular, the first material may be glass and the second material carbon.

The presence of glass threads can make it possible to have a role of tracer so as in particular to help the positioning of the fibrous preform in the injection mold for forming the matrix, and the carbon threads make it possible to improve the compatibility of the strand instrumented with carbon strands intended to form the rest of the fiber preform. These materials are particularly suitable for the manufacture of a turbomachine fan part, but those skilled in the art will recognize that other materials can be envisaged depending on the intended application. In an exemplary embodiment, the method further comprises forming the reinforcing threads by separating the threads of a reinforcing strand before forming the preform of the instrumented strand.

Obtaining reinforcing threads by opening a reinforcing strand makes it possible to limit the impact of the instrumentation on the diameter of the strand and on the textile to be obtained. In an exemplary embodiment, the preform of the instrumented strand comprises a winding of reinforcing threads around said at least one wired detection element.

Such a feature makes it possible to optimally protect the wired detection element.

In an exemplary embodiment, said at least one wired detection element is an optical fiber.

The implementation of an optical fiber is preferred because it is suitable for supplying a wide variety of information and therefore capable of allowing more flexible control. Other detection elements can nevertheless be envisaged, as will be mentioned below.

In an exemplary embodiment, the optical fiber comprises a core having at least one optical Bragg grating filter.

The use of an optical Bragg grating filter makes it possible to give a particularly precise state of the material health of the part or the preform. The invention also relates to a method for manufacturing a part made of composite material, comprising:

- the manufacture of at least one instrumented strand by implementing a method as described above,

- the formation of a fibrous preform of the part to be obtained by carrying out one or more textile operations implementing said at least one instrumented strand, and

- the formation of a matrix in a porosity of the fibrous preform.

In an exemplary embodiment, the fiber preform is formed by three-dimensional weaving.

In an exemplary embodiment, the part is a part of a fan of an aircraft engine, such as a fan blade or a fan casing. It is possible to carry out a method for monitoring a physical parameter in a fiber preform as described above or in a part as described above, comprising at least the detection of a possible modification of the propagation of the physical signal conducted by the wired detection element using a control unit, and the determination of information relating to the physical parameter from the detection carried out.

In an exemplary embodiment, the physical parameter is chosen from at least one of: the progression of a matrix material in the porosity of the fibrous preform, the temperature within the fibrous preform during a firing of a matrix material impregnating the fibrous preform, or the application of mechanical stresses in the composite material part.

According to a second aspect, the invention relates to a strand intended to undergo a textile operation for the formation of a fibrous preform of a composite material part, comprising a core comprising at least one wired detection element able to transmit a physical signal , and at least one reinforcement wire distinct from the wired detection element and wound around the core.

The strand according to the invention makes it possible to instrument the material directly during the textile operation of forming the fiber preform with a minimal impact on the textile properties, such as the fiber volume rate or the weaving weave for the case of a woven preform. The mechanical strength of the part is thus not altered due to the instrumentation. Further, it becomes possible to perform control during the matrix forming step. The strand according to the invention allows durable instrumentation throughout the life cycle of the part, both during its manufacture and during its period of service.

The implementation of an optical fiber is preferred because it is suitable for supplying a wide variety of information and therefore capable of allowing more flexible control. Other detection elements can nevertheless be envisaged, as will be mentioned below. In an exemplary embodiment, said at least one reinforcing thread is wrapped around the core.

As a variant, the strand comprises a plurality of reinforcing threads braided around the core.

In an exemplary embodiment, said at least one reinforcing thread is made of carbon, glass, aramid or ceramic.

These materials are particularly suitable for the manufacture of a turbomachine fan part, but those skilled in the art will recognize that other materials can be envisaged depending on the intended application.

The invention also relates to a fibrous preform intended to form the fibrous reinforcement of a part made of composite material, comprising one or more strands as described above.

In an exemplary embodiment, the fibrous preform is woven by three-dimensional weaving.

In an exemplary embodiment, the fiber preform is a preform of a part of an aircraft engine fan.

The invention also relates to a part made of composite material comprising a fibrous preform as described above and a matrix densifying a porosity of the fibrous preform.

According to one example, the part can be a fan part of an aircraft engine, such as a fan blade or a fan casing.

The invention also relates to a method for monitoring a physical parameter in a fiber preform as described above or in a part as described above, comprising at least the detection of a possible modification of the propagation of the physical signal conducted by the wired detection element with the aid of a control unit, and the determination of information relating to the physical parameter from the detection carried out.

In an exemplary embodiment, the physical parameter is chosen from at least one of: the progression of a matrix material in the porosity of the fibrous preform, the temperature within the fibrous preform during a firing of a matrix material impregnating the fibrous preform, or the application of mechanical stresses in the composite material part. Brief description of the drawings

[Fig. 1] Figure 1 shows, schematically and partially, an example of an installation for manufacturing an instrumented strand according to the first aspect of the invention.

[Fig. 2] Figure 2 shows, schematically and partially, a cross section of the instrumented strand manufactured by the installation of Figure 1.

[Fig. 3] Figure 3 shows, schematically and partially, an example of a strand according to the second aspect of the invention.

[Fig. 4] Figure 4 shows, schematically and partially, another example of a strand according to the second aspect of the invention.

[Fig. 5] FIG. 5 schematically represents an example of an optical fiber that can be used in an instrumented strand within the scope of the invention.

[Fig. 6] FIG. 6 represents intensity-wavelength graphs relating respectively to an incident wave at the input of the optical fiber of an instrumented strand usable in the context of the invention, to the wave transmitted at the output of this fiber optic and to the wave reflected at the input of this optical fiber.

[Fig. 7] FIG. 7 schematically represents the shift in the wavelength of the wave reflected at the input of an optical fiber of an instrumented strand usable in the context of the invention following deformations of this fiber.

[Fig. 8] Figure 8 shows, schematically and partially, a fiber preform usable in the context of the invention.

[Fig. 9] FIG. 9 schematically and partially represents the monitoring of a physical parameter in a fiber preform obtained by implementing the invention.

[Fig. 10] FIG. 10 represents, schematically and partially, the monitoring of a physical parameter in a part made of composite material obtained by implementing the invention.

Description of embodiments

FIG. 1 represents an example of installation 100 making it possible to form an instrumented strand with a wired detection element, here in the form of a fiber optical. The technique exemplified implements a technique of commingling threads (known under the name of “commingling” in the Anglo-Saxon literature). In general, the instrumented strand can be produced by a continuous manufacturing method during which the reinforcing threads are obtained by separating (a so-called "spreading" technique) the constituent threads of a reinforcing strand then are then added around the scrolling wireframe sensing element. Mention may be made of document WO 2016/057735 which describes the spacing technique followed by a commélage of threads.

The installation 100 exemplified in FIG. 1 comprises a coil 102 on which is wound a reinforcing strand which is here formed of a plurality of son 104 of glass reinforcement. The threads 104 are separated from each other by a drawing technique under tension known per se using a separating roller 103 which has, in the example illustrated, a longitudinal section of progressive thickness with a region of extra thickness in its middle zone. Those skilled in the art will recognize that other roll structures 103 are possible to achieve the spacing of the wires 104. The installation 100 further comprises a coil 101 on which is wound the optical fiber 5 which is scrolled by conveying by the roller 103 and the roller 109. By way of example, an optical fiber 5 marketed under the reference “SM1250 Bend Insensitive Polyimide” can be used. The installation comprises two guide devices 105 and 107 making it possible to guide the wires 104 so as to bring them progressively closer to the optical fiber 5 in motion. In the example illustrated, the devices 105 and 107 can be in the form of eyelets possibly movable in rotation so as to wind the wires 104 around the optical fiber 5 if desired. The preform 110 of the instrumented strand is formed at the drive roller 109 on which the fiber 5 and the yarns 104 are combined. The preform 110 of the instrumented strand is driven by the roller 109 towards a bath 111 of a holding binder contained in a reservoir 113. A conveying element 115 is immersed in the bath in order to make the preform 110 scroll through the bath 111 The holding binder can be polymeric. By way of example, the bath 111 can be formed by an aqueous solution of a polymer such as polyvinylpyrrolidone (PVP) but those skilled in the art will recognize that other compounds can be considered. The preform 110 coated with the holding binder is then driven through an oven 119 using the conveying elements 117 and 121 to bake the binder and increase its rigidity so as to obtain the instrumented strand 1 which is then wound around of the spool 123 awaiting a textile operation to form the fiber preform of the part.

The example illustrated relates to a particular case where a second set of reinforcing threads 108 is combined with the threads 104 and the optical fiber 5. The installation comprises a coil 106 on which is wound a second reinforcing strand which is here formed of a plurality of carbon reinforcing threads 108. The threads 108 are separated by a separating roller 103 and are then guided and attached around the optical fiber 5 as described for the threads 104. The example makes it possible to obtain an instrumented strand 1 with glass reinforcing threads and made of carbon, the presence of carbon strands making it possible to improve the mechanical performance of the instrumented strand and to reduce the heterogeneity with the rest of the fibrous preform of the part to be obtained, which may comprise carbon strands in the case of a fan part preform (blade or casing) of an aircraft engine. Figure 2 shows a cross-sectional view of the strand 1 thus obtained. The example illustrated relates to an instrumented strand comprising reinforcing threads formed from different materials, but the scope of the invention is not departed from when using reinforcing threads formed from the same material added around the optical fiber 5 .

A description has just been given of a possible technique for the continuous manufacture of a strand instrumented by an optical fiber separate from the reinforcing threads 104 and 108 and intended for integration into a part made of composite material, according to the first aspect of the invention. Figures 3 and 4, which will now be described, relate to two examples relating to the second aspect according to the invention.

FIG. 3 illustrates an example of a strand la according to the second aspect of the invention which has been obtained by wrapping a plurality of reinforcing threads 3a around a core formed by a wired detection element 5a capable of transmitting a physical signal, as an optical signal or an electrical signal. The covering operation is a known operation per se. Element 5a may comprise a conduction portion capable of transmitting the physical signal surrounded by a sheath. In the example illustrated, element 5a is an optical fiber. Of course, the number of reinforcing threads 3a and of element(s) 5a used per strand can vary and is not limited to the case illustrated. The element(s) 5a may have a diameter smaller than the diameter of the wire(s) 3a. As indicated above, the material of the wires 3a is chosen according to the application envisaged, these wires 3a possibly being made of carbon or of glass in the case of the manufacture of a part for the cold part of an aeronautical turbomachine. By way of example, it is possible to use an optical fiber 5a marketed under the reference “SM1250 Bend Insensitive Polyimide” as mentioned above in connection with the first aspect of the invention. The strand 1a thus obtained can then be wound around a reel awaiting completion of the textile operation. FIG. 4 illustrates a strand lb according to an alternative embodiment in which a plurality of reinforcing threads 3b have been braided around a core formed by an element 5a.

The following details a possible structure for the optical fiber 5 in connection with FIG. 5, it being understood that this description also applies to the case of the optical fiber 5a implemented in the context of the second aspect of the invention.

The optical fiber 5 illustrated comprises a core 50 allowing the transmission of an optical signal surrounded by a sheath 54 which participates in the confinement of the optical signal in the core 50. The sheath 54 and the core 50 are surrounded by a protective coating 56, by example in polymeric material. In the example illustrated, the core 50 comprises at least one optical filter 52 with a Bragg grating (“Fiber Bragg Grating” in the English literature), or several of these filters positioned one after the other along the core 50 The Bragg grating optical filter 52 corresponds to a structure known per se in which there is a periodic variation of the refractive index with a step p which makes it possible to reflect a precise wavelength, as will be mentioned in new in the sequel. The optical fiber 5 present in the part made of composite material or in the preform of this part is intended to be connected to a control unit to carry out monitoring. The control unit may include a light source, such as a laser, for sending light into the optical fiber as well as an analyzer for analyzing the reflected optical signal, and in particular for determining its wavelength in order to compare it with the reference wavelength filtered by the optical fiber . It is possible to place the control unit in the fan of the turbomachine, or alternatively connect it only to carry out the control and disconnect it once the control is finished. The control unit can comprise a data storage device making it possible to store information relating to the optical signal passing through the optical fibers for continuous or subsequent analysis. FIG. 6 shows the effect of the optical Bragg grating filter 52 on an incident light wave having a distribution of light intensity IE as a function of the wavelength at the optical fiber input as illustrated in graph 6A. The graph 6B shows the transmitted light intensity IT as a function of the wavelength through the optical filter 52 and the graph 6C shows the reflected light intensity IR by the optical filter 52. The optical filter 52 makes it possible to reflect the light at wavelength _λB therefore to filter this wavelength with a certain precision as illustrated in graph 6C (reference wavelength filtered by the optical fiber). The wavelength reflected by the optical filter 52 is given by the formula below and is provided by the manufacturer of the optical fiber: [Math. 1]

At _B= 2*n*p in this formula n the effective refractive index and p the pitch of the filter. Traction or compression of the optical fiber leads to a change in the pitch P of the filter and, consequently, in the reflected wavelength. There is a linear relationship between the variation in wavelength and the variation in the length of the filter 52 (ie the deformation) as indicated in the formula below. The analysis of the variation of À _B makes it possible to deduce the deformation therefrom.

[Math. 2]

Lo designating the length of the filter 52 allowing the filtration of the wavelength λ _B and the factor k corresponding to the fiber factor supplied by the manufacturer of the fiber. Figure 7 shows the effect on the reflected wavelength of a stress applied to the optical fiber. Graph 7A shows that applying tensile stress to the fiber results in a shift to higher wavelengths of the reflected wavelength. The application of a compressive stress results conversely in a reduction in the reflected wavelength (graph 7B). We can refract the rest of the light at the end of the optical fiber so that it does not interfere with the measurement and we then deduce, from the wavelength shift of the optical signal reflected by the optical fiber, the deformation of the latter which makes it possible, if desired, to go back to the stress at the level of the filter 52. According to an example, several optical filters 52 with Bragg gratings can be arranged in series with different pitches in order to distinguish the signals reflected by the various filters. It is thus possible to locate the application of the stress or the strain along the fiber. It is also possible to use the optical filters to form pressure or acceleration sensors. It is also possible to measure the temperature applied to the preform, for example during the formation of the die, or to the part due to a change in the refractive index of the optical fiber leading to a modification in the propagation of the signal. optical, also leading in the case of the use of a Bragg grating filter to a modification of the reflected wavelength.

Examples of tracking possibilities offered by the instrumented strand on the composite material part and preform of this part will be described below. The rest of the description applies in an equivalent manner to the examples of strands 1, la and 1b of FIGS. 2 to 4.

A fibrous preform 10 of the part to be obtained can be formed by three-dimensional weaving from a plurality of strands 1 described above (FIG. 8). The invention is not limited to this case and the fibrous preform can alternatively be obtained by two-dimensional weaving or braiding of the strands 1. In the example of FIG. 8, the preform 10 comprises a plurality of strands 1 present at the times in warp direction CH and weft direction TR but this does not depart from the scope of the invention if it is otherwise. It is possible to form a fibrous preform solely from strands 1 as described above, or with a mixture of these strands 1 with separate strands, devoid of the element 5. The preform 10 may comprise son of carbon, glass , aramid or ceramic or a mixture of such yarns. In general, the position of the strand or strands integrating the element 5 is chosen according to the physical parameter to be monitored. In addition, it can be ensured that the instrumented strand or strands are visible from a surface of the preform 10. This can make it possible, in the case of the use of glass reinforcing threads having a tracer function, to help positioning of the fibrous preform in the mold in which the matrix material is intended to be brought. In the case of a woven preform, one or more strands 1 forming weft, respectively warp, strands can bind one or more warp, respectively weft layers. These bonded warp or weft layers may themselves comprise one or more strands 1. During weaving, element 5 is integrated into preform 10 as the strand 1 to which it belongs is woven. The strand(s) 1 may be present at the core of the preform 10.

Examples of monitoring physical parameters on a fiber preform 10 or on a composite material part 40 are illustrated in connection with Figures 9 and 10.

In the case of FIG. 9, it is desired to follow the progression of a matrix material 30 in a porosity of the preform 10. In order to carry out its densification, the preform 10 is positioned in a mold 20 comprising a form 22 and a counter-form 24 delimiting between them at least one orifice 26 for introducing the matrix material 30. The matrix material 30 is introduced along the direction marked by the arrow IM through the orifice 26, for example by injection, and penetrates into the porosity of the preform 10. In general, the matrix material 30 can be a resin and a curing of the resin introduced into the porosity of the fibrous preform can then be carried out in order to obtain a part made of composite material with an organic matrix. The advancing front of the material 30 in the porosity of the preform 10 is materialized by the reference F in FIG. 9. The optical fiber 5 is connected to a control unit U by a link 50. The signal coming from the control unit U can be transmitted and analyzed by a computer which can return a result giving information on the progress of the edge F. The optical fiber 5 comprises, in a manner known per se, a core forming the conduction portion which is capable of transmitting an optical signal along the longitudinal axis of the fiber and a sheath which surrounds the core and participates in the confinement of the signal optical in the heart. The presence of material 30 around the optical fiber 5 leads to a modification of the propagation of the optical signal in the conduction portion of the fiber 5. The techniques for detecting such a modification of the propagation of the optical signal are known per se. The optical fiber 5 can for example comprise one or more Bragg gratings and the detection of the modification of the optical signal can be carried out by analysis of the spectral response in transmission or in reflection.

FIG. 10 relates to an example of monitoring a finished part 40. The case has been shown here of a fan blade 40 which conventionally comprises a root zone 44, an aerodynamic profile zone 42 and a crown 46. The blade 40 also defines a leading edge BA (upstream edge relative to the air circulation in the fan) and a trailing edge BF (downstream edge relative to the air circulation in the fan). The control unit U is connected to the optical fiber 5 in the same way as in FIG. 9. Continuous monitoring can be carried out, in particular during the operation of the blade 40, or the optical fiber 5 to carry out the check then disconnect it once the check has been carried out. In the example considered, the evolution of the mechanical stresses applied in the part 40 in operation is monitored by detecting a modification in the propagation of the optical signal transmitted by the optical fiber 5. A technique similar to that described above can allow the detection of such a change. The invention can also be applied to the manufacture of a composite material turbomachine fan casing, or to other parts. More generally, the examples of application in FIGS. 9 and 10 implement an optical fiber but those skilled in the art will recognize that other elements 5 can be envisaged such as a thermocouple allowing in particular the monitoring of the temperature within the preform during the firing cycle of the material 30, an electrical conductor whose resistance or resistivity may be altered or a dielectric sensor. These other elements can be used as an alternative or in combination with the optical fiber.

Claims

[Claim 1] Method of manufacturing an instrumented strand (1) intended for a textile operation for the formation of a fiber preform (10) of a part made of composite material, comprising:

- a scrolling of at least one wired detection element (5) capable of transmitting a physical signal, reinforcing threads (104; 108) being attached around said at least one wired detection element in scrolling fashion so as to form a preform (110) of the instrumented strand, and

- depositing a holding binder (111) on the preform of the instrumented strand thus obtained so as to obtain the instrumented strand.

[Claim 2] A method according to claim 1, wherein the insert reinforcing threads comprise a first set of reinforcing threads (104) of a first material, and a second set of reinforcing threads (108) of a second material different from the first material.

[Claim 3] A method according to claim 2, wherein the first material is glass and the second material is carbon.

[Claim 4] A method according to any one of claims 1 to 3, wherein the method further comprises forming the reinforcing yarns (104; 108) by spacing the yarns of a reinforcing strand before forming the preform (110) of the instrumented strand.

[Claim 5] Method according to any one of Claims 1 to 4, in which the preform (110) of the instrumented strand comprises a winding of the reinforcing threads (104; 108) around the said at least one wired detection element (5) .

[Claim 6] A method according to any one of claims 1 to 5, wherein said at least one wired sensing element (5) is an optical fiber.

[Claim 7] A method according to claim 6, wherein the optical fiber (5) comprises a core (50) having at least one Bragg grating optical filter (52).

[Claim 8] A method of manufacturing a part (40) of composite material, comprising:

- the manufacture of at least one instrumented strand (1) by implementing a method according to any one of claims 1 to 7,

- the formation of a fibrous preform (10) of the part to be obtained by carrying out one or more textile operations implementing said at least one instrumented strand, and

- the formation of a matrix in a porosity of the fibrous preform.

[Claim 9] A method according to claim 8, wherein the fiber preform (10) is formed by three-dimensional weaving.

[Claim 10] A method according to claim 8 or 9, wherein the part (40) is a part of a fan of an aircraft engine.

[Claim 11] Fibrous preform (10) intended to form the fibrous reinforcement of a part (40) made of composite material, comprising one or more strands (1; la; lb) intended to undergo a textile operation for the formation of the preform fiber, the said strand(s) comprising a core comprising at least one wired detection element (5; 5a) capable of transmitting a physical signal, and at least one wire (104;

108; 3a; 3b) of reinforcement distinct from the wired detection element and wound around the core.

[Claim 12] A preform (10) according to claim 11, wherein said at least one wired sensing element (5; 5a) is an optical fiber.

[Claim 13] Preform (10) according to Claim 11 or 12, in which the said at least one reinforcing thread (3a) is wrapped around the core.

[Claim 14] A preform (10) according to claim 11 or 12, wherein the strand (lb) comprises a plurality of reinforcing threads (3b) braided around the core.

[Claim 15] A preform (10) according to any one of claims 11 to 14, wherein said at least one reinforcing thread (104; 108; 3a; 3b) is carbon, glass, aramid or ceramic.

[Claim 16] A fibrous preform (10) according to any one of claims 11 to 15, wherein the fibrous preform is woven by three-dimensional weaving.

[Claim 17] A fiber preform (10) according to any one of claims 11 to 16, wherein the fiber preform is a one-piece preform (40) of an aircraft engine fan.

[Claim 18] Part (40) of composite material comprising a fiber preform (10) according to any one of claims 11 to 17 and a matrix densifying a porosity of the fiber preform.

[Claim 19] Method for monitoring a physical parameter (F) in a fibrous preform (10) according to any one of Claims 11 to 17 or in a part (40) according to Claim 18, comprising at least the detection of a possible modification of the propagation of the physical signal conducted by the wired detection element (5; 5a) using a control unit (50), and the determination of information relating to the physical parameter from of the detection performed.

[Claim 20] Method according to claim 19, in which the physical parameter is chosen from at least one of: the progression (F) of a matrix material (30) in the porosity of the fibrous preform (10), the temperature within the fiber preform during a firing of a matrix material impregnating the fibrous preform, or the application of mechanical stresses in the part (40) made of composite material.