Manufacturing process for a composite part

Abstract

A method for manufacturing a composite turbomachine part, the method comprising the following steps: - supplying at least one spool of fiber strands (30), said strands (30) comprising fibers (31) of at least one first type of fiber, - weaving a preform of the part from said strands (30), - inserting the preform into a mold, - injecting a precursor of a part matrix into the mold and hardening the precursor to form a matrix embedding the preform, and - obtaining the composite part. Each fiber strand (30) also comprises fibers (32) of a second type of fiber, said fibers (32) of the second type of fiber being arranged radially in the center of the strand (30) and being completely surrounded radially by the fibers (31) of the first type. Figure to be published with the abbreviation: 5

Description

Title of the invention: Method for manufacturing a composite part Technical field of the invention

[0001] The invention relates to a method for manufacturing a composite part. The part is, for example, part of an aircraft, and more specifically of a turbomachine, such as part of a fan casing, part of a fixed blade structure, or in particular a fan blade. Prior art

[0002] It is known to inspect structural mechanical parts by tomographic methods, for example radiographic or acoustic, in order to detect the presence of possible defects on the surface and inside the part or to check the shape and / or positioning of internal parts and structures not directly observable.

[0003] These methods are reliable, non-invasive and allow inspection of the inside of the parts, which makes it possible to quickly determine the condition of the part and decide whether to potentially put it back into operation or replace it.

[0004] A tomographic measurement consists of scanning an observed object, here a mechanical part, by means of a beam of waves, and measuring the transmitted beam in all directions in order to reconstruct a three-dimensional image of the object.

[0005] Such an examination is represented in [Fig. 1], and implements a tomography device 1, for the inspection of a part 20.

[0006] The tomography device 1 includes at least one emitting device 3, configured to emit an incident beam 5 of wave pulses towards the part 20, for example radio frequency waves, X-rays or acoustic waves, and at least one receiver 7 capable of capturing a transmitted beam 9 of waves, arranged on either side of the part 20.

[0007] The part 20 is generally mounted on a support 11 rotating around an axis A, in order to be observed from all directions during the tomographic measurement.

[0008] The waves pass through the part 20, and the transmitted beam 9 from the part 20 is captured by the receiver 7. The intensity distribution of the transmitted beam 9 obtained is converted into a two-dimensional greyscale image of the part 20 by the processing device 13.

[0009] The part 20 is rotated by means of the support 11, and two-dimensional images of the part 20 are acquired in all directions.

[0010] A three-dimensional greyscale image, or tomographic image, can then be reconstructed by digital processing from the two-dimensional images obtained under all directions of observation, said tomographic image comprising a plurality of voxels each exhibiting a respective grey level, representative of the material's absorption density at that point.

[0011] In the present case, part 20 observed by tomography is of a composite material which comprises several distinct phases comprising different materials, represented in [Fig.2].

[0012] Such a part is for example part of an aircraft, and more specifically of a turbomachine, such as part of a fan casing, part of a fixed blade structure, or in particular a fan blade.

[0013] Such a composite material comprises fibers wound together to form strands, generally supplied on reels.

[0014] Said strands are woven in one or more weaving planes, according to a two-dimensional pattern, as shown in [Fig.2], with weft strands 22 extending along a weft direction X and warp strands 21 extending along a warp direction Y.

[0015] Alternatively, the weaving can be three-dimensional, with strands extending along a third direction, for example along a thickness direction Z.

[0016] The weaving is carried out on a loom on which the strands are mounted, so as to form a fibrous preform of the part to be produced. The preform is then placed in a mold and embedded in a precursor which is solidified in the mold to form a solid matrix 23 around the preform.

[0017] The fibers forming the strands 21, 22 can be carbon fibers, glass fibers, synthetic polymer fibers, or a mixture of several types of fibers. The matrix 23 comprises, for example, one or more polymers and / or resins, which solidify around the weave to form the composite part 20.

[0018] X-ray tomography inspection of such a composite part is particularly relevant, as it allows for verification of the quality and regularity of the strand weave, as well as verification of the correct positioning of the preform within the part's structure for optimal contribution to mechanical properties. Such verification can be performed during manufacturing to improve the process, and after manufacturing to check the quality of the resulting parts.

[0019] In order to improve the contrast of tomography images and thus facilitate the detectability of the preform strands in the tomographic image, it is known to add tracers in some of the strands, i.e. contrast fibers of a different composition from the rest of the strand and which offer maximum contrast in tomography compared to the other fibers and the matrix, thus forming tracer strands that are easily detectable and whose arrangement can be followed with greater precision.

[0020] These tracer strands are arranged at specific locations in the weave, determined in order to precisely visualize the position of the preform.

[0021] This is particularly relevant in cases where the components of the part do not naturally offer high contrast, as may be the case with carbon fibers in polymer or resin matrices.

[0022] These processes can be further improved. Indeed, as shown in [Fig.3], the tracer strands 24 are made by co-winding a bundle of standard fibers 25 and contrast fibers 26 during the formation of the tracer strand 24, so that in each tracer strand 24, the contrast fibers 26 are arranged spirally in the strand.

[0023] Such a winding implies an intermittent signature when the tracer strand is observed along a transverse direction, which complicates the precise detection of the position of the tracer strand, particularly during automatic three-dimensional image analysis.

[0024] Furthermore, it is common to use strands of different sizes in the preform, generally referenced according to the number of fibers in each strand, the positions of which must be respected for good performance. Such differences in strand sizes further complicate the detection of tracer strands, and tracer strands do not allow for easy differentiation between the different strand sizes for the analysis of the weave and the part as a whole. Presentation of the invention

[0025] The invention aims to remedy these drawbacks by proposing a method for manufacturing composite parts that allows for precise and reliable tomographic analysis of the weave of the preform strands as well as the positioning of the preform in the finished part.

[0026] To this end, the invention relates to a method for manufacturing a composite part of a turbomachine, the method comprising the following steps:

[0027] - supply of at least one reel of fiber strands, said strands comprising fibers of at least one first type of fibers,

[0028] - weaving a preform of the part from said strands,

[0029] - insertion of the preform into a mold,

[0030] - injection into the mold of a precursor of a matrix of the part and hardening of the precursor to form a matrix embedding the preform, and

[0031] - obtaining the composite part,

[0032] characterized in that each fiber strand also comprises fibers of a second type of fiber, said fibers of the second type of fiber being arranged radially at the center of the strand and being entirely surrounded radially by the fibers of the first type.

[0033] Such a process makes it possible to obtain a composite part in which the position of each of the strands can be visualized by tomography with improved contrast, thus reliably and precisely determining the position of the strands and the quality of the weave. Furthermore, the arrangement of fibers of the second type at the center of the strand allows for a strand signature that corresponds locally and precisely to its direction.

[0034] Each fiber strand can comprise an amount of fibers of the second type which depends on the total amount of fibers in the strand.

[0035] Such a characteristic makes it possible to identify the nature and size of each strand on the tomographic image thanks to the intensity of its signature.

[0036] The quantity of fibers of the second type in each strand can depend linearly on the total quantity of fibers in the strand.

[0037] Such a characteristic makes it possible to differentiate between several categories of strand sizes, while maintaining a constant influence between the different categories of fiber types in the strands.

[0038] The quantity of fibers of the second type in each strand can depend on a characteristic dimension of the part and / or a characteristic volume of the part.

[0039] Such a feature allows for a quantity of fibers in each strand that ensures sufficient image contrast and enables the detection of said fibers, depending on the total image size. The quantity of fibers of the second type can also be determined based on the imager characteristics.

[0040] The characteristic dimension is, for example, a greater length of the part, measured along any direction.

[0041] Alternatively, the characteristic dimension can be a transverse thickness of the part, measured perpendicular to a local extent plane of the part.

[0042] The characteristic volume of the room can be a total overall volume of the room, that is to say a volume occupied by the room in space.

[0043] Alternatively, the characteristic volume of the part can be a total volume of solid in the part.

[0044] The process may further include, after obtaining the composite part, a step of acquiring at least one three-dimensional image of said composite part by means of a tomography device and a step of checking the positions of the strands in the composite part by visualizing the fibers of the second type in said at least one three-dimensional image.

[0045] Such a feature makes it possible to control the quality of the weaving and the positions of the strands in the piece after its manufacture.

[0046] The fibers of the first type can be carbon fibers or fibers comprising at least one synthetic organic polymer, and the fibers of the second type can be glass fibers.

[0047] Such a characteristic allows for a significant contrast between the fibers of the second type on the one hand and the fibers of the first type and the matrix on the other hand, in X-ray tomography.

[0048] The invention also relates to a composite turbomachine part obtained by a process as above, comprising strands of fibers embedded in a matrix, in which fibers of the second type are arranged radially in the center of each strand and surrounded radially by fibers of the first type.

[0049] The part may be at least a part of a turbomachine blade, in particular a fan blade. Brief description of the figures

[0050] [Fig-1] [Fig.1] is a schematic side view of a tomography device during the inspection of a mechanical part,

[0051] [Fig.2] [Fig.2] is a schematic detail view of a part made of material woven composite,

[0052] [Fig. 3] [Fig. 3] is a schematic view of a tracer strand of a composite part of the state of the art,

[0053] [Fig.4] [Fig.4] is a flowchart of a part manufacturing process according to the invention,

[0054] [Fig.5] [Fig.5] is a schematic cross-sectional view of a strand of a part composite obtained according to a process according to the invention, and

[0055] [Fig.6] [Fig.6] is a schematic cross-sectional view of a strand of a The part according to the invention is a schematic cross-sectional view of four types of strands of a composite part obtained according to a process according to the invention. Detailed description of the invention

[0056] A process 100 for manufacturing a composite part 20 will now be described, with reference to [Fig.4].

[0057] The process 100 includes a step of supplying 110 with at least one spool of fiber strands intended for the production of a fibrous preform of the part 20.

[0058] Such a strand 30 is shown in cross-section in [Fig.5].

[0059] According to the invention, each of said strands 30 comprises fibers 31 of at least one first type of fibers and fibers 32 of a second type of fibers.

[0060] The second type fibers 32, or contrast fibers, exhibit high contrast when observed by tomography, for example by X-rays, compared to the first type fibers 31 and the matrix 23.

[0061] For example, the fibers 31 of the first type are carbon fibers, which offer a low contrast with a polymer and / or resin matrix 23, while the fibers 32 of the second type are glass fibers, which offer a good contrast with the carbon fibers and with said matrix 23, in particular due to their much higher density.

[0062] Indeed, on a classic tomographic image, carbon fibers and the matrix are visible with fairly similar shades of grey, while glass fibers appear white and are therefore easily detectable.

[0063] According to the invention, the fibers 32 of the second type are arranged radially in the center of the strand 30 and are completely surrounded radially by the fibers 31 of the first type.

[0064] The term center of the strand 30 is understood for each radial plane, that is to say that the fibers 32 of the second type form the "core" of the strand 30 while the fibers 31 of the first type surround them.

[0065] Here, the radial direction describes any dimension perpendicular to a local overall elongation direction of the strand 30.

[0066] By "fully radially surrounded", it is meant that the fibers 32 of the second type are not exposed in the radial directions, so that only the fibers 31 of the first type are visible to the naked eye on the strand.

[0067] Advantageously, the fibers 31 of the first type are regularly distributed circumferentially around the fibers 32 of the second type, so that a radial thickness E of fibers 31 of the first type around the fibers 32 of the second type is substantially constant on the periphery of the strand 30.

[0068] According to one embodiment, each strand 30 comprises a majority of fibers 31 of the first type and a minority of fibers 32 of the second type.

[0069] In particular, the number of fibers 32 of the second type can depend linearly on the total number of fibers in the strand 30, for example 1 / 1000 of the fibers included in the strand 30.

[0070] Generally, the strands 30 are supplied in several dimensions, and are intended to be placed at different locations in the preform according to their dimensions, with several examples shown in [Fig.6].

[0071] A strand 30 is notably dimensioned according to the number of fibers wound to form the strand, with for example strands of 24000 fibers, 48000 fibers, 72000 fibers and 96000 fibers, as shown in [Fig.6], where these strands 30 are respectively referenced 24K, 48K, 72K and 96K.

[0072] In this case, the number of fibers of the second type can respectively be chosen to be equal to 24, 48, 72 and 96 fibers of the second type per strand 30, i.e. 1 / 1000 total fibers in the strand.

[0073] The process 100 then includes a weaving step 120 of a preform of the part 20 from said strands, employing a loom on which the bobbins have been loaded.

[0074] The strands 30 are in particular positioned at predetermined locations in the preform according to their respective dimensions.

[0075] The weaving of the preform can be two-dimensional with one or more stacked weaving planes, or three-dimensional.

[0076] The process then includes steps of inserting 130 the preform into a mold, then injecting 140 into the mold a precursor of the matrix 23 and hardening 150 the precursor to form the matrix 23 embedding the preform.

[0077] Depending on the nature of the matrix, the precursor can be a solution comprising one or more chemical compounds, intended to crosslink in a controlled manner in the mold.

[0078] The process finally includes a step of extraction from the mold and obtaining 160 the composite part 20, and, advantageously, after obtaining the composite part 20, a step of acquiring 170 at least one three-dimensional image of said composite part by means of the tomography device 1, in particular X-ray tomography, and a step of checking the positions of the strands 30 in the composite part by visualizing the fibers 32 of the second type in said at least one three-dimensional image. For example, the part 20 is then validated or rejected, depending on the results of this analysis.

Claims

Demands

1. A method (100) for manufacturing a composite turbomachine part (20), the method comprising the following steps: - supplying (110) at least one spool of fiber strands (30), said strands (30) comprising fibers (31) of at least one first type of fiber, - weaving (120) a preform of the part (20) from said strands (30), - inserting (130) the preform into a mold, - injecting (140) into the mold a precursor of a matrix (23) of the part (20) and hardening (150) the precursor to form a matrix (23) embedding the preform, and - obtaining (160) the composite part (20), characterized in that each fiber strand (30) also comprises fibers (32) of a second type of fiber, said fibers (32) of the second type of fiber being arranged radially at the center of the strand (30) and being entirely surrounded radially by the fibers (31) of the first type.

2. A method (100) according to the preceding claim, wherein each strand (30) of fibers comprises an amount of fibers (32) of the second type which depends on the total amount of fibers in the strand (30).

3. A method (100) according to the preceding claim, wherein the quantity of fibers (32) of the second type in each strand (30) depends linearly on the total quantity of fibers in the strand (30).

4. A method (100) according to the preceding claim, wherein the quantity of fibers (32) of the second type in each strand (30) depends on a characteristic dimension of the part (20) and / or a characteristic volume of the part (20).

5. A method (100) according to any one of the preceding claims, wherein the method further comprises, after obtaining (160) the composite part (20), a step of acquiring (170) at least one three-dimensional image of said composite part (20) by means of a tomography device (1) and a step of checking the positions of the strands (30) in the composite part (20) by visualizing the fibers (32) of the second type in said at least one three-dimensional image.

6. A method (100) according to any one of the preceding claims, wherein the fibers (31) of the first type are carbon fibers or fibers comprising at least one synthetic organic polymer, and the fibers (32) of the second type are glass fibers.

7. Composite turbomachine part (20) obtained according to a process (100) according to any one of the preceding claims, comprising strands (30) of fibers embedded in a matrix (23), in which fibers (32) of the second type are arranged radially at the center of each strand (30) and surrounded radially by fibers (31) of the first type.

8. Composite part (20) according to the preceding claim, wherein the part (20) is at least a part of a turbomachine blade, in particular a blower blade.

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