GB2553515A

GB2553515A - Method

Info

Publication number: GB2553515A
Application number: GB1614804.1A
Authority: GB
Inventors: G Jones Dean; Hocking Matthew; Huckin Luke
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2016-09-01
Filing date: 2016-09-01
Publication date: 2018-03-14
Also published as: GB201614804D0

Abstract

A method of repairing a fibre-reinforced matrix composite component, comprising removing at least a portion of the component by laser ablation 66. A process output, e.g. plasma, plume, and/or acoustic signal resulting from the laser ablation, is monitored 68 and detected e.g. by camera, light and/or ultrasound detector, and in response and preferably by comparison 70 relative to a reference value or range, the laser ablation is controlled by being maintained, modified and/or stopped, e.g. by modification 74 of speed, path, shielding, assistive gas, and/or type of laser. The method may be used for removing coatings (fig 3) e.g. glue, polyurethane or paint, and to remove a particular number of layers (64, 62, 60, fig 3). The body may be defined as an organic or ceramic matrix composite. The whole may be in a control system with a controller (78, fig 5). The method is designed for repairing a component in a gas turbine engine (fig 1), e.g. a casing or a carbon fibre reinforced fan blade.

Description

(71) Applicant(s):

Rolls-Royce pic (Incorporated in the United Kingdom)

Buckingham Gate, LONDON, SW1E 6AT, United Kingdom (72) Inventor(s):

Dean G Jones Matthew Hocking Luke Huckin (56) Documents Cited:

WO 2002/029853 A2 DE 003911329A1 US 4588885 A

WO 1993/012905 A1 US 5204517 A (58) Field of Search:

INT CL B23K

Other: Online: WPI, EPODOC (74) Agent and/or Address for Service:

Rolls-Royce pic

IP Department (SinA-48), PO Box 31, DERBY, Derbyshire, DE24 8BJ, United Kingdom (54) Title of the Invention: Method

Abstract Title: Repairing a fibre-reinforced composite by removing a portion by laser ablation with responsive monitoring of the process (57) A method of repairing a fibre-reinforced matrix composite component, comprising removing at least a portion of the component by laser ablation 66. A process output, e.g. plasma, plume, and/or acoustic signal resulting from the laser ablation, is monitored 68 and detected e.g. by camera, light and/or ultrasound detector, and in response and preferably by comparison 70 relative to a reference value or range, the laser ablation is controlled by being maintained, modified and/or stopped, e.g. by modification 74 of speed, path, shielding, assistive gas, and/or type of laser. The method may be used for removing coatings (fig 3) e.g. glue, polyurethane or paint, and to remove a particular number of layers (64, 62, 60, fig 3). The body may be defined as an organic or ceramic matrix composite. The whole may be in a control system with a controller (78, fig 5). The method is designed for repairing a component in a gas turbine engine (fig 1), e.g. a casing or a carbon fibre reinforced fan blade.

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Application No. GB1614804.1

RTM

Date :8 March 2017

Intellectual

Property

Office

The following terms are registered trade marks and should be read as such wherever they occur in this document:

Blu-ray

Intellectual Property Office is an operating name of the Patent Office www.gov.uk/ipo

METHOD

TECHNICAL FIELD

The present disclosure concerns a method of repairing a composite component and/or a system for use in repairing a composite component.

BACKGROUND

Gas turbine engines are typically employed to power aircraft. Typically a gas turbine engine will comprise an axial fan driven by an engine core. The engine core is generally made up of one or more turbines which drive respective compressors via coaxial shafts. The fan is usually driven off an additional lower pressure turbine in the engine core.

The fan comprises an array of radially extending fan blades mounted on a rotor. The fan blades and/or a casing that surrounds the fan may be manufactured from composite materials. In composite fan blades, the blades may include a composite body and a metallic leading edge and a metallic trailing edge.

Composite components generally include reinforcing fibres (e.g. high strength or high stiffness fibres) embedded in a matrix, e.g. a plastic matrix material. In many examples, composite components are formed of laminates, where adjacent stacked plies are bonded together to build the composite component. Composite components are often coated with a glue layer, a polyurethane layer and with a paint layer.

During use, the composite component may be damaged. In the case of a fan blade or casing, the damage may be caused by impact with a foreign object. It is desirable to, where possible, repair the damaged component rather than replace it. Conventionally, mechanical cutting techniques, for example grinding or milling, are used to remove the required layers of material, e.g. the coatings, before being re-coated and/or a cured patch being applied to repair the composite component.

SUMMARY

According to an aspect there is provided a method of repairing a composite component. The composite component comprises a body having a fibre reinforced matrix. The method comprises removing at least a portion of the composite component using laser ablation and during laser ablation, monitoring a process output created by the laser ablation. In response to the monitored process output, the laser ablation is maintained, modified and/or stopped.

The composite component may comprise one or more coatings provided on the body. The laser ablation may comprise removing at least a portion of the one or more coatings.

The method described herein permits accurate selective coating and/or ply removal from a composite component. The laser ablation process outputs can be used as layer identifiers to indicate when a transition between layers has been reached. This indication can then be used to inform whether to continue with the laser ablation or whether to change the laser ablation parameters, for example the parameters may be modified for optimal removal of an adjacent layer (e.g. coating or ply).

The process output may be plasma, plume and/or acoustic signals.

When a laser impacts a surface plasma may be created. The properties of this plasma can be analysed to indicate the properties of the material the laser is impacting, for example using laser induced breakdown spectroscopy (LIBS).

When a laser impacts a surface, a plume may be created. The plume may include vapour, smoke and/or particulate debris. The quantity and properties of the vapour, smoke and/or particulate debris can indicate the material that is being ablated.

When a laser impacts a surface, an acoustic signal may be emitted.

Plasma, plume and acoustics may all be monitored, or alternatively only one or two of these may be monitored.

Monitoring the process output may comprise detecting the process output using a camera, a light detector, and/or an ultrasound detector.

The method may comprise comparing the process output to a reference process output (or reference process output range). If the monitored process output (or monitored process output range) is above or below the reference process output (or reference process output range), the laser ablation may be modified and/or stopped.

The reference process output (or reference process output range) is defined by a predetermined process output (or predetermined process output range).

The method may comprise measuring the process output at the start or at a point in time during the laser ablation to define the reference process output (or the reference process output range).

Modifying laser ablation may comprise changing the laser speed, changing the laser path, changing the type or amount of shielding, changing the type or amount of assist gas, and/or changing the type of laser used during ablation.

The composite component may comprise one or more coatings provided on the body. The method may comprise removing one coating from the composite component using laser ablation and the monitored process output indicating once a second coating is reached, in response to the monitored process output, modifying the laser ablation to remove the second coating using laser ablation.

The coatings of the component may be glue, polyurethane and/or paint.

The body of the composite component may be defined by an organic matrix composite or a ceramic matrix composite.

In the case of an organic matrix composite, the composite may have a plastic resin matrix reinforced with carbon fibres.

The component may be a component of a gas turbine engine, for example a fan blade or a casing.

According to an aspect there is provided a system for repairing a composite component. The composite component comprises a body having a fibre reinforced matrix. The system comprises a laser for removing at least a portion of the composite component by laser ablation. The system also comprises a detector for detecting a process output created during laser ablation. The system further comprises a control system configured to receive a signal from the detector and based upon the received signal control the laser so as to either maintain, modify or stop the laser ablation.

The control system may comprise a controller configured to perform the method according to the previous aspect.

The controller may be configured to compare the signal received from the detector to a reference signal, and if the detected signal is outside the reference signal the controller may be configured to stop the laser or to modify the properties of the laser ablation process.

The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore except where mutually exclusive any feature described herein may be applied to any aspect and/or combined with any other feature described herein.

DESCRIPTION OF THE DRAWINGS

Embodiments will now be described by way of example only, with reference to the Figures, in which:

Figure 1 is a sectional side view of a gas turbine engine;

Figure 2 is a perspective view of a fan blade;

Figure 3 is a sectional view of a portion of a body of the fan blade of Figure 2;

Figure 4 is a block diagram of a method of repairing a composite component; and

Figure 5 is a schematic of an arrangement used to repair a composite component.

DETAILED DESCRIPTION

With reference to Figure 1, a gas turbine engine is generally indicated at 10, having a principal and rotational axis 11. The engine 10 comprises, in axial flow series, an air intake 12, a propulsive fan 13, an intermediate pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, an intermediate pressure turbine 18, a low-pressure turbine 19 and an exhaust nozzle 20. A nacelle 21 generally surrounds the engine 10 and defines both the intake 12 and the exhaust nozzle 20.

The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow into the intermediate pressure compressor 14 and a second air flow which passes through a bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 14 compresses the airflow directed into it before delivering that air to the high pressure compressor 15 where further compression takes place.

The compressed air exhausted from the high-pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 17, 18, 19 before being exhausted through the nozzle 20 to provide additional propulsive thrust. The high 17, intermediate 18 and low 19 pressure turbines drive respectively the high pressure compressor 15, intermediate pressure compressor 14 and fan 13, each by suitable interconnecting shaft.

Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.

Various components of the gas turbine engine are composite components. For example, the components may be made from organic matrix composites (e.g. fan blades and fan casing) or ceramic matrix composites (e.g. compressor or turbine blades or stators).

Referring to Figure 2, a composite fan blade generally comprises an aerofoil body 42 having a leading edge 44, a trailing edge 46, a concave pressure surface wall 48 extending from the leading edge to the trailing edge and a convex suction surface wall extending from the leading edge to the trailing edge. The fan blade has a root 52 via which the blade can be connected to the hub. The fan blade has a tip 56 at an opposing end to the root. The fan blade may also have an integral platform 54 which may be hollow or ribbed for out of plane bending stiffness. The fan blade includes a metallic leading edge and a metallic trailing edge. The remainder of the blade (e.g. the body of the blade) is made from composite material. In the present example, the composite material is a carbon fibre reinforced resin matrix.

Referring now to Figure 3, the body 58 of the blade is coated with several coatings. The coating proximal to the body 58 is a glue layer 60. The coating applied to the glue layer is a polyurethane layer 62, and the outermost coating (which is applied to the polyurethane layer) is a paint layer 64.

During use, composite components, such as the composite fan blade, may require repair. To repair a component the regions of damage are removed. For example, if only a portion of the paint layer is damaged, it is desirable to remove said portion of the paint layer. The component is then repaired using either a resin patch and/or by applying the appropriate coatings to the repair region. For example, if only the paint layer is damaged, the damaged region of paint layer can be removed and then the region can be repainted.

The coating layers 60, 62, 64 often have varying depths due to manufacturing tolerances, in service modifications, or previous repairs. As such, if a specific depth is selected for material removal, it can result in under or over removal of a layer. Neither of these results are desirable and risk, in some cases affecting the structural integrity of the component, particularly if over removal occurs (i.e. a portion of the coating or body below the coating to be removed is removed).

One method of coating removal is laser ablation. During laser ablation, plasma may be produced (provided the laser is directed with sufficient intensity), and a laser plume will be produced. Laser plume includes vapour, smoke and/or particulate debris. There are also acoustic sounds emitted when the laser impacts a coating.

As will now be described, the plasma, plume and/or acoustics can be used during the method of removal to indicate properties of the material being removed.

Referring to Figure 4, a method of repair of a composite component such as a fan will now be described.

Firstly, as indicated at block 66, a laser is directed at a region of the composite component requiring repair. The laser used for laser ablation may be an infrared laser, a green laser, an ultraviolet laser or a Nd:YAG (neo-dymium-doped yttrium aluminium garnet) laser. The laser power, frequency, beam width, beam spacing, scan speed and number of passes can be selected for optimal removal of the coating. The path of the laser is defined so as to remove a coating from the region requiring repair.

In the present example, the laser removes a coating layer by layer, that is, the laser removes the outermost layer 64, then if desired the layer 62, and finally if desired the layer 60. In exemplary embodiments a portion of the composite body 58 may also be removed. For example, in the case of a laminate structure, one or more of the plies may be removed on a ply-by-ply basis.

Now referring to block 68, whilst the coating layer is removed, for example whilst layer 64 is removed, the plasma, plume and/or acoustic sound is detected.

In the case of the plasma, an optical and/or vision camera system may be used. For example, light detectors optionally coupled with light dispersers may be used, and a method such as laser induced breakdown spectroscopy (LIBS) can be employed to analyse the chemical properties of the plasma. In the case of the plume, the chemical composition of the vapour, smoke, and/or debris may be detected and/or the relative percentage volumes of vapour, smoke and/or debris may be detected. In the case of acoustic sound, the sound may be detected using an ultrasonic detector.

Referring now to block 70, the properties detected at block 68 are compared to reference properties. These properties may be properties that are predetermined, for example from a database, or they may be the properties of the coating layer when the laser removal process first commenced. The reference properties may be a range of properties. The properties may be for example chemical composition, volume of smoke, vapour and debris, and/or acoustic signature.

If the properties are within the reference range the laser continues to remove the coating and the laser parameters are maintained, as indicated by block 72. The plasma, plume and/or acoustic outputs are monitored and the steps of block 68 and 70 are repeated.

If the properties are out of the reference range, the laser parameters are either modified as indicated by block 74 or the laser removal process is stopped as indicated by block 76.

The parameters may be modified if for example, the removal of the coating can be optimised by changing the laser parameters. Alternatively, the laser parameters may be modified for removal of another coating layer. For example, the laser parameters required for optimal removal of a paint layer are different to those for optimal removal of a polyurethane layer, which are different to those optimal for a glue layer, which are different to those optimal for a removal of a portion of the body. The parameters that may be modified include the laser power, frequency, beam width, beam spacing, scan speed and number of passes. The type of laser may also be changed for optimal coating removal.

The parameters may also be modified to alter the laser path, for example, if the detected properties indicate that the coating has been fully removed in one portion but still remains in another portion.

The laser removal process will be stopped for example if it has been indicated that the layer of coating has been removed.

The advantage of the described method is that the laser removal process can be adapted using feedback from measured properties to improve removal of coatings, and/or layers of the body. Furthermore, the measured properties can indicate a transition between coatings, the body, or plies within the body, and as such, the risk of over or under removal of material from a component is reduced.

Referring now to Figure 5, equipment that may be used to implement the method of Figure 4 is illustrated. The equipment includes a laser arrangement 76, which may include a laser, a beam expander and a galvo-scanning system. The laser arrangement is connected to control apparatus. The equipment also includes detectors 90, 92. In this example two detectors are shown, one is an optical detector and one an acoustic detector, but in alternative embodiments one or more detectors may be provided, of any suitable type.

The control apparatus includes a controller 78, a user input device 80, and an output device 82. In some examples, the apparatus may be a module. As used herein, the wording ‘module’ refers to a device or apparatus where one or more features are included at a later time and, possibly, by another manufacturer or by an end user. For example, where the apparatus is a module, the apparatus may only include the controller, and the remaining features may be added by another manufacturer, or by an end user.

The controller 78, the user input device 80, and the output device 82 may be coupled to one another via a wireless link and may consequently comprise transceiver circuitry and one or more antennas. Additionally or alternatively, the controller, the user input device and the output device may be coupled to one another via a wired link and may consequently comprise interface circuitry (such as a Universal Serial Bus (USB) socket). It should be appreciated that the controller, the user input device, and the output device may be coupled to one another via any combination of wired and wireless links.

The controller may comprise any suitable circuitry to cause performance of the methods described herein and as illustrated in Fig. 4. The controller may comprise: control circuitry; and/or processor circuitry; and/or at least one application specific integrated circuit (ASIC); and/or at least one field programmable gate array (FPGA); and/or single or multi-processor architectures; and/or sequential/parallel architectures; and/or at least one programmable logic controllers (PLCs); and/or at least one microprocessor; and/or at least one microcontroller; and/or a central processing unit (CPU); and/or a graphics processing unit (GPU), to perform the methods.

In various examples, the controller may comprise at least one processor 84 and at least one memory 86. The memory stores a computer program 88 comprising computer readable instructions that, when read by the processor, causes performance of the methods described herein, and as illustrated in Fig. 4. The computer program may be software or firmware, or may be a combination of software and firmware.

The processor 84 may include at least one microprocessor and may comprise a single core processor, may comprise multiple processor cores (such as a dual core processor or a quad core processor), or may comprise a plurality of processors (at least one of which may comprise multiple processor cores).

The memory 86 may be any suitable non-transitory computer readable storage medium, data storage device or devices, and may comprise a hard disk and/or solid state memory (such as flash memory). The memory may be permanent non-removable memory, or may be removable memory (such as a universal serial bus (USB) flash drive or a secure digital card). The memory may include: local memory employed during actual execution of the computer program; bulk storage; and cache memories which provide temporary storage of at least some computer readable or computer usable program code to reduce the number of times code may be retrieved from bulk storage during execution of the code.

The computer program 88 may be stored on a non-transitory computer readable storage medium. The computer program may be transferred from the nontransitory computer readable storage medium to the memory. The nontransitory computer readable storage medium may be, for example, a USB flash drive, a secure digital (SD) card, an optical disc (such as a compact disc (CD), a digital versatile disc (DVD) or a Blu-ray disc). In some examples, the computer program may be transferred to the memory via a wireless signal or via a wired signal.

Input/output devices may be coupled to the system either directly or through intervening input/output controllers. Various communication adaptors may also be coupled to the controller to enable the apparatus to become coupled to other apparatus or remote printers or storage devices through intervening private or public networks. Non-limiting examples include modems and network adaptors of such communication adaptors.

The user input device 80 may comprise any suitable device for enabling an operator to at least partially control the apparatus. For example, the user input device may comprise one or more of a keyboard, a keypad, a touchpad, a touchscreen display, and a computer mouse. The controller 78 is configured to receive signals from the user input device.

The output device 82 may be any suitable device for conveying information to a user. For example, the output device may be a display (such as a liquid crystal display, or a light emitting diode display, or an active matrix organic light emitting diode display, or a thin film transistor display, or a cathode ray tube display), and/or a loudspeaker, and/or a printer (such as an inkjet printer or a laser printer). The controller 78 is arranged to provide a signal to the output device to cause the output device to convey information to the user.

The controller 78 is configured to control the laser assembly 76. That is, the controller has the ability to start and stop the laser process, and to change the laser process parameters, such as laser power, frequency, beam width, beam spacing, scan speed and number of passes. Further, in examples where the laser assembly 76 includes two or more lasers of different types, the controller can select the laser to be used. The controller may start and stop a process and/or modify a process based on commands from the user input device.

The controller 78 may cause display of the laser ablation progress and properties on the user output device 82 during or after the laser ablation process.

The controller 78 is arranged to receive information form the detectors 90, 92 indicative of the laser process properties such as plasma, plume and acoustics. A processor 94 may be provided remotely or may form part of the controller. The processor 94 may process information from one or more of the detectors 90, 92 and send this information to the controller 78. For example, the processor 94 may be configured to perform spectroscopy.

The controller performs analysis of the information from the detectors as discussed in the method previously described, and controls the laser assembly accordingly.

It will be understood that the invention is not limited to the embodiments abovedescribed and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and subcombinations of one or more features described herein.

Claims

1. A method of repairing a composite component, the composite component comprising a body having a fibre reinforced matrix, the method comprising:

removing at least a portion of the composite component using laser ablation;

during laser ablation, monitoring a process output created by the laser ablation; and in response to the monitored process output, maintaining, modifying and/or stopping the laser ablation.

2. The method according to claim 1, wherein the composite component comprises one or more coatings provided on the body, and wherein the laser ablation comprises removing at least a portion of the one or more coatings.

3. The method according to claim 1 or 2, wherein the process output is plasma, plume and/or acoustic signals.

4. The method according to any one of the previous claims, wherein monitoring the process output comprises detecting the process outputs using a camera, a light detector, and/or an ultrasound detector.

5. The method according to any one of the previous claims, comprising comparing the process output to a reference process output, and if the monitored process output is above or below the reference process output, modifying and/or stopping the laser ablation.

6. The method according to claim 5, wherein the reference process output is defined by a predetermined process output.

7. The method according to claim 5, comprising measuring the process output at the start or at a point in time during the laser ablation to define the reference process output.

8. The method according to any one of the previous claims, wherein modifying laser ablation comprises changing the laser speed, changing the laser path, changing the type or amount of shielding, changing the type or amount of assist gas, and/or changing the type of laser used during ablation.

9. The method according to anyone of the previous claims, wherein the composite component comprises one or more coatings provided on the body, and wherein the method comprises removing one coating from the composite component using laser ablation and the monitored process output indicating once a second coating is reached, in response to the monitored process output, modifying the laser ablation to remove the second coating using laser ablation.

10. The method according to any one of the previous claims, wherein the coatings of the component are glue, polyurethane and/or paint.

11. The method according to any one of the previous claims, wherein the body of the composite component is defined by an organic matrix composite or a ceramic matrix composite.

12. The method according to any one of the previous claims, wherein the component is a component of a gas turbine engine, for example a fan blade or a casing.

13. A system for repairing a composite component, the composite component comprising a body having a fibre reinforced matrix, the system comprising:

a laser for removing at least a portion of the composite component by laser ablation;

a detector for detecting a process output created during laser ablation; and a control system configured to receive a signal from the detector and based upon the received signal control the laser so as to either maintain, modify or stop the laser ablation.

Intellectual

Property

Office

Application No: Claims searched:

GB1614804.1

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