FR3117212A1 - DEVICE FOR DETECTING THE THERMAL THRESHOLD OF A THREE-DIMENSIONAL WEAVED COMPOSITE PART MOLDED BY RESIN TRANSFER - Google Patents

Abstract

This thermal threshold detection device (18) of a composite part (12) comprises a detection means (22) of an overrun of a temperature threshold in the part (12) and a transmission means (20) exceeded threshold information, the transmission means (20) comprising a first electrical terminal and a second electrical terminal, the detection means (22) comprising an electrical circuit connected to the first and second terminals. The electric circuit is provided with a first branch provided with a first retaining means for keeping the connection closed on the first branch, a first opening means for interrupting the connection on the first branch when the first retaining means is inactive, the first retaining means being configured to become inactive from a first predefined temperature, the transmission means (20) comprising an RFID tag (26). Figure for abstract: Fig 1

Description

DEVICE FOR DETECTING THE THERMAL THRESHOLD OF A THREE-DIMENSIONAL WEAVED COMPOSITE PART MOLDED BY RESIN TRANSFER

The present invention relates to a thermal threshold detection device and method, in particular for a composite part intended to form an aircraft turbojet engine blade.

Aircraft equipped with turbojet engines are generally equipped with blades formed by composite parts.

Frequently, it is sought to determine whether the composite part with a polymer matrix forming the blade has been subjected to a temperature above a certain threshold, such as 140° C. for example. Indeed, this temperature can alter the mechanical properties of the matrix material. For example, the vane temperature rise may be caused by an external event during part operation, such as a thermal pipe leak near the part.

To find out if the blade temperature has reached a threshold, a temperature sensor such as a thermocouple can be incorporated into the composite part. However, such a sensor requires a wired connection which has the following drawbacks: heavy, bulky and can impact/disturb the mechanical behavior of the composite part. In addition, such a sensor requires maintenance to change the electrical power supply system.

Another solution consists in using a chromatic paint which evolves according to the temperature. However, chromatic paints do not have sufficient reliability over time because they are too sensitive to the external environment, in particular to dust and humidity. In addition, this solution requires having visual access in order to ascertain whether a threshold has been reached.

The invention aims to remedy these drawbacks.

More particularly, the invention aims to provide a means for determining, with sufficient long-term reliability, whether the part has reached a thermal threshold without requiring the incorporation of a device that is heavy, bulky or disrupts the mechanical behavior of the part.

To this end, there is proposed a device for detecting the thermal threshold of a composite part with three-dimensional weaving and molded by resin transfer, comprising means for detecting an overrun of a temperature threshold in the part and means for transmitting exceeded threshold information detected by the detection means, the transmission means comprising a first electrical terminal and a second electrical terminal, the detection means comprising an electrical circuit connected to the first and second terminals.

According to a general characteristic of this device, the electrical circuit is provided with a first branch provided with a first retaining means for maintaining the connection closed on the first branch, with a first opening means for interrupting the connection on the first branch when the first retaining means is inactive, the first retaining means being configured to become inactive from a first predefined temperature, the transmission means comprising an RFID tag.

Thanks to such an arrangement, it is possible to transmit the measured temperature and to power the sensor electrically without requiring a wired connection and/or an autonomous power supply means within the sensor, which optimizes the mass and the size of the sensor.

Preferably, the first opening means is capable of exerting a residual mechanical stress on the first branch and/or in which the first retaining means comprises a component with a known melting temperature.

Such a design choice makes it possible to avoid a return to the initial state, even if the temperature then drops. This results in better efficiency in the detection of the thermal threshold overrun.

In an advantageous embodiment, the first opening means comprises an elastic return means.

Advantageously, the component comprises an MCP 137 alloy.

Such an alloy, which has a melting point of 137°C, is particularly advantageous in the case of a turbine turbojet engine blade, in which it is generally desired to determine whether the part has been subjected to a temperature above 140°C, this temperature can alter the mechanical properties of the material.

According to another embodiment, the component comprises an MCP 79 alloy.

Such an alloy, which has a melting temperature of 79° C., can in particular be used to provide relevant information as to the risk that another blade of the turbojet engine could cross a thermal threshold.

Advantageously, the electrical circuit comprises a second branch branched off from the first branch, the second branch being provided with a second retaining means for maintaining the connection closed on the second branch, with a second opening means for interrupting the connection to the second branch, when the second retaining means is inactive, the second retaining means being configured to become inactive from a second predefined temperature different from the first temperature.

Such a design of the electric circuit makes it possible to detect the overrun of several thermal thresholds, corresponding to different temperatures.

Preferably, each branch comprises a resistor, said resistors being substantially equal.

This increases the precision of the detection of the overrun of several thermal thresholds, by maximizing the voltage difference between a situation of detection of an overrun of the thermal threshold and a situation of non-detection of this overrun.

According to another aspect, there is proposed a composite part with three-dimensional weaving and molded by resin transfer, the part preferably being a blade for an aircraft turbojet engine, the part comprising a matrix, a reinforcement, and a detection device such as previously defined.

Preferably, the transmission means is located on the surface of the part.

Such a position of the transmission means makes it possible to promote the transmission, in particular wireless, of the temperature measured to an external device.

It is also possible to provide that the part is intended to be pivotable about an axis of rotation and comprises an end adjacent to the axis of rotation and an end opposite to the axis of rotation, the transmission means being close to the axis of rotation. adjacent end.

This facilitates the transmission, in particular wireless, of the temperature measured to an external device in the case of a pivoting part such as a turbojet engine blade.

According to another aspect, there is proposed a blade intended to be incorporated into an aircraft, comprising a detection device as defined above.

According to yet another aspect, there is proposed a turbomachine intended to be incorporated into an aircraft, comprising a composite part as defined above.

According to another embodiment, there is proposed a turbomachine intended to be incorporated into an aircraft, comprising a blade as defined above.

According to another aspect, an aircraft is proposed comprising a turbomachine as defined previously.

According to yet another aspect, a process for manufacturing a composite part is proposed, in which a three-dimensional reinforcement is woven, then resin transfer molding is implemented.

According to a general characteristic of this process, a detection device as defined above is integrated into the part.

According to yet another aspect, there is proposed a method for detecting the thermal threshold of a composite part with three-dimensional weaving molded by resin transfer in which a detection means detects an overrun of a temperature threshold in the part and a means transmission transmits the exceeded threshold information detected.

According to a general characteristic of this method, a detection device as defined above is used.

The invention will be better understood and other aims, characteristics and advantages will become apparent on reading the following detailed description comprising embodiments given by way of illustration with reference to the appended figures, presented by way of non-limiting examples. , which may be used to complete the understanding of the invention and the presentation of its realization and, where appropriate, contribute to its definition, on which:

is an isometric representation of a turbojet incorporating a composite part and a detection device according to the present invention.

is a front view of the turbojet of the .

is a schematic representation of a blade of the turbojet of Figures 1 and 2.

And are schematic illustrations of one branch of the sensing device shown in the , respectively to a maintained connection state and to an interrupted connection state.

is a schematic representation of a thermal threshold detection method according to another aspect of the present invention.

, , And are schematic illustrations of the detection device of Figures 1 to 3 at different stages of the process of the .

With reference to the , a turbojet engine 2 has been schematically represented. The turbojet engine 2 is intended to be incorporated into an aircraft (not shown), for example an airplane.

The turbojet engine 2 comprises a frame 4. A direct orthonormal vector base 6 attached to the frame 4 is defined. The vector base 6 consists of a vector X, a vector Y and a vector Z. The frame 4 has a axisymmetric shape about an axis 8 parallel to the vector X. In the present application, except where indicated otherwise, the terms "axial" and "radial" and variations of these terms will be understood as referring to axis 8.

The turbojet engine 2 comprises a hub 10 having a shape of revolution around the axis 8. In a manner known per se, the hub 10 is capable of pivoting, relative to the frame 4, around the axis 8.

The turbojet engine 2 comprises a plurality of vanes 12. The vanes 12 are fixed to the hub 10 and extend radially outwards from the hub 10. As a result, the vanes 12 pivot, relative to the frame 4, around of axis 8.

The blades 12 are formed from a three-dimensionally woven composite piece, also known as “3D woven”. The blades 12 are molded by resin transfer, also designated by the Anglo-Saxon name “Resin Transfer Molding” or by the corresponding acronym “RTM”.

More particularly, in a manner known per se, the blades 12 comprise a matrix (not referenced), for example made of epoxy, and a reinforcement (not referenced), comprising in this case a three-dimensional fabric, for example fiberglass or in carbon fiber.

Each blade 12 has an elongated shape, substantially directed in the radial direction. Each vane 12 comprises a hub-side end 14 and a tip-side end 16. The hub-side end 14 corresponds to an inner radial end of the vane 12, adjacent to the axis 8. The tip-side end 16 corresponds to a outer radial end of blade 12, opposite to axis 8.

Referring to Figures 1 to 3, a blade 12 includes a thermal threshold detection device 18. The device 18 has the function of detecting whether the corresponding blade 12 has been subjected to a predefined temperature. In the example illustrated, a single blade 12 comprises a detection device 18. However, it is possible without departing from the scope of the invention to consider incorporating detection devices 18 on several of the blades 12 of the turbojet engine 2, or even on the all blades 12.

The device 18 comprises a transmission means 20, a detection means 22 and an electrical connection means 24 integrated into the volume of the blade 12. The detection means 22 is capable of detecting whether the composite part forming the blade 12 has exceeded one or more temperature thresholds. The electrical connection means electrically connects the transmission means 20 and the detection means 22, so that the detection means 22 is electrically powered and so that the transmission means 20 receives the information of exceeding a threshold of temperature by the composite part constituting the blade 12.

With reference to the , the transmission means 20 comprises a radio tag, in particular a radio tag according to RFID technology 26, said radio tag having two electrical terminals 28 and 30. Radio tag 26 is preferably passive, i.e. that is to say that it does not have a battery likely to increase its mass, and that it is powered by a radio wave generated by a reader, preferably RFID, and which operates advantageously on the ultra high frequency band, also known by the acronym "UHF", which typically corresponds to frequencies of 860 MHz to 960 MHz.

In the example illustrated, the transmission means 20 is arranged on an outer surface 32, schematically represented in FIG. 3, of the composite part forming the blade 12. Again with reference to FIGS. 1 to 3, the transmission means 20 is located close to the end on the hub side 14.

The turbojet engine 2 comprises a reader, specifically a reader according to RFID technology 34. In the example illustrated, the RFID reader 34 is placed on the hub 10. the RFID reader 34 on a different part, for example on the frame 4 or on a fin (not referenced) fixed to the frame 4. The RFID reader 34 can also be portable and supported by a user (not shown) located in front of the turbojet 2.

The RFID reader 34 is placed at a distance, relative to the transmission means 20, preferably between 50 mm and 3000 mm. When the RFID reader 34 is not arranged on the pivoting assembly constituted by the hub 10 and the blades 12, the positioning of the transmission means 20 as close as possible to the axis of rotation 8 is advantageous insofar as it favors the transmission of energy and information by ultra high frequency waves between the RFID reader 34 and the transmission means 20.

Again with reference to the , the detection means 22 comprises a plate 36 and an electrical circuit 38. The plate 36 is made of an insulating material such as a polymer material, ceramic material, or even a printed circuit of the FR4 type. The electrical circuit 38 can be produced by conductive tracks made on the plate 36.

The electrical circuit 38 comprises three branches 40, 42 and 44 connected in parallel between two nodes 46 and 48. More particularly, each branch 40, 42 and 44 is capable of implementing an electrical connection between the nodes 46 and 48.

Each branch 40, 42 and 44 comprises a resistor 50. The three resistors 50 are substantially identical and have a resistance R ₅₀ of between 10 Ω and 5 M Ω, in this case 1 KΩ.

Figures 4 and 5 schematically illustrate branch 40. Branches 42 and 44 are substantially identical to branch 40.

With reference to the , branch 40 comprises a conductive element with residual mechanical stress 52. In the example illustrated, element 52 comprises an elastic return means such as a leaf spring tending to move away from plate 36.

The branch 40 comprises a component with a known melting temperature 54. For example, the component 54 can comprise a solder point made of lead, bismuth, tin, indium or any other alloy made of an electrically conductive material and which has its liquid solid melting point in the desired range of values.

The known melting temperature component 54 retains the conductive element 52 against the plate 36, as long as the melting temperature has not been reached. In this way, as long as the melting temperature has not been reached, the electrical connection implemented by the branch 40 remains closed as illustrated on the . As soon as the melting temperature has been reached, as shown in the , the component 54 melts, the conductive element 52 deviates from the plate 36 and the connection implemented by the branch 40 is interrupted. In this way, the component 54 makes it possible to retain the closed connection on the branch 40 and the element 52 makes it possible to interrupt the connection when the component 54 exceeds the melting temperature.

Again with reference to the , the known melting temperature component 54 of leg 40 has a melting temperature of 79°C, the known melting temperature component 54 of leg 42 has a melting temperature of 108°C and the component with a melting temperature of known fusion 54 of branch 44 has a fusion temperature of 137°C. In this case, the known melting temperature component 54 of branch 40 is an MCP alloy 79 based on bismuth, indium and tin, 54 of branch 42 is an MCP alloy 108 based on zinc ( 1.8%), indium (52.2%) and tin (46%) and the known melting temperature component 54 of branch 44 is an MCP 137 alloy based on bismuth and tin.

Electrical connection means 24 comprises two electrical lines 56 and 58. Electrical line 56 electrically connects electrical terminal 28 to node 46. Electrical line 58 electrically connects electrical terminal 30 to node 48.

With reference to the , a thermal threshold detection method in the composite part constituting the blade 12 of the includes an initialization step E01. During step E01, as shown in the , the known melting temperature components 54 of the branches 40, 42 and 44 are in the solid state and the conductive elements 52 are in contact with the components 54.

Still during step E01, the RFID reader 34 transmits electromagnetic energy by induction which enables the RFID tag 26 to generate electrical energy. The RFID tag 26 is equipped with an internal electronic circuit which makes it possible to measure the electrical resistance in the electrical circuit 38. More particularly, the intensity is divided between the three branches 40, 42 and 44. As a result , the resistance measured between nodes 46 and 48 is equal to R ₅₀ /3.

The process of comprises a second step E02 during which the detection means 22 detects an overrun of a temperature threshold.

More particularly, in the case where the blade 12 is subjected to a temperature comprised between 79° C. and 108° C., as illustrated in FIG. 8, the component with a known melting temperature 54 of the branch 40 melts and the element conductor 52 of branch 40 moves away from plate 36. As a result, the electrical connection on branch 40 is broken, the electrical connection on branches 42 and 44 is kept closed, and the resistance measured between nodes 46 and 48 becomes R ₅₀ /2.

If, during step E02, the blade 12 is subjected to a temperature of between 108°C and 137°C, then the components with a known melting temperature 54 of the branches 40 and 42 melt, and the conductive elements 52 branches 40 and 42 move away from plate 36. The electrical connection on branches 40 and 42 is then interrupted, the electrical connection on branch 44 is maintained and the resistance measured between nodes 46 and 48 is equal to R ₅₀ .

If, during step E02, the blade 12 is subjected to a temperature going beyond 137°C, then the components with a known melting temperature 54 of the branches 40, 42 and 44 melt and the conductive elements 52 legs 40, 42 and 44 move away from platen 36. As a result, the electrical connection on legs 40, 42 and 44 is broken so that electrical circuit 38 becomes open.

The conductive element with mechanical residual stress 52 cannot return to its initial shape after having moved away from the plate 36, even if the temperature drops again. Therefore, the detection of a threshold overrun will continue to indicate that the threshold has been exceeded, even in the event of a temperature falling below the threshold.

The process of comprises a third step E03 during which the transmission means 20 transmits to the RFID reader 34 the value of the resistance measured between the nodes 46 and 48 and/or the possible opening of the electrical circuit 38. The RFID reader 34 can then transmit this information to a control device (not shown) of the turbojet engine 2, which deduces therefrom whether the blade 12 has exceeded a thermal threshold.

The device and the method according to the invention therefore make it possible to detect, reliably over the long term, the exceeding of a temperature threshold by a turbojet blade or another composite part. In addition, detection is made possible without however requiring the incorporation of a particularly heavy device, such as a thermocouple, and requiring an independent power supply means.

Claims (13)

Device for detecting the thermal threshold (18) of a composite part (12) with three-dimensional weaving and molded by resin transfer, comprising:
- means (22) for detecting an overrun of a temperature threshold in the room (12), comprising an electrical circuit (38) and,
- a transmission means (20) of exceeded threshold information detected by the detection means (22) comprising a first electrical terminal (28) and a second electrical terminal (30) connected to the electrical circuit (38),
characterized in that the electrical circuit (38) comprises a first branch (40, 42, 44) provided with:
- a first retaining means (54) to keep the connection closed on said at least first branch (40, 42, 44),
- a first opening means (52) to interrupt the connection on said at least first branch (40, 42, 44) when the first retaining means (54) is inactive,
the first retaining means (54) being configured to become inactive from a first predefined temperature and,
the transmission means (20) comprising a radio tag, in particular a radio tag according to RFID technology (26). Device (18) according to Claim 1, in which the first opening means (52) is able to exert a residual mechanical stress on the first leg (40, 42, 44) and/or in which the first retaining means comprises a known melting temperature component (54). Device (18) according to Claim 2, in which the first opening means comprises an elastic return means (52). A device (18) according to claim 2 or 3, wherein the component (54) comprises an MCP 137 alloy and/or an MCP 79 alloy. Device (18) according to any one of Claims 1 to 4, in which the electrical circuit (38) comprises a second branch (40, 42, 44) in parallel with respect to the first branch (40, 42, 44), the second branch (40, 42, 44) comprising:
- a second retaining means (54) to keep the connection closed on the second branch (40, 42, 44),
- a second opening means (52) to interrupt the connection on the second branch (40, 42, 44) when the second retaining means (54) is inactive,
the second retaining means (54) being configured to become inactive from a second predefined temperature and different from the first temperature. A device (18) according to claim 5, wherein each leg (40, 42, 44) includes a resistor (50), said resistors (50) being substantially equal. Composite part (12) with three-dimensional weaving and molded by resin transfer, the part (12) preferably being a blade for an aircraft turbojet engine (2), the part (12) comprising a matrix, a reinforcement, and a detection (18) according to any one of claims 1 to 6, the transmission means (20) preferably being located on the surface of the part (12). Composite part (12) according to Claim 7, in which the part (12) is intended to be pivotable around an axis of rotation (8) and comprises an end (14) adjacent to the axis of rotation (8) and an end opposite (16) to the axis of rotation (8), the transmission means (20) being close to the adjacent end (14). Blade (12) intended to be incorporated in an aircraft, comprising a detection device (18) according to any one of Claims 1 to 6. Turbomachine (2) intended to be incorporated in an aircraft, comprising a composite part (12) according to claim 7 or 8 and/or a blade (12) according to claim 9. Aircraft comprising a turbomachine (2) according to claim 10. Process for manufacturing a composite part (12), in which a three-dimensional reinforcement is woven, then resin transfer molding is implemented, characterized in that a detection device (18) according to one of any of claims 1 to 6 to the piece (12). A method of detecting the thermal threshold of a composite part (12) with three-dimensional weaving molded by resin transfer in which a detection means (22) detects an overshoot of a temperature threshold in the part (12) and a means of transmission (20) transmits the detected exceeded threshold information, characterized in that a detection device (18) according to any one of Claims 1 to 6 is used.