COMPOSITE PLATE FOR THE AERONAUTICAL INDUSTRY

Abstract

Composite plate (10), particularly for the aeronautical industry, this composite plate (10) having a sandwich structure and comprising: - a first layer (12) comprising non-woven carbon fiber scraps (14) and a thermoplastic binder ensuring the bonding of the fiber scraps together, - a second layer (16) comprising non-woven carbon fiber scraps (14) and a thermoplastic binder ensuring the bonding of the fiber scraps together, and - a foam layer (18) sandwiched between the first and second layers (12, 16), this foam layer (18) being made of thermoplastic, the layers (12, 16, 18) of the composite plate (10) being bonded together by fusion of their respective thermoplastic materials at the interfaces between the layers. Figure for the abbreviation: Figure 1

Description

Title of the invention: COMPOSITE PLATE FOR THE AERONAUTICAL INDUSTRY Technical field of the invention

[0001] The invention relates to a composite plate in particular for the aeronautical industry, this composite plate being made from carbon fiber scraps. Technical background

[0002] Carbon fiber consumption has exploded over the last ten years. Production has adapted to meet the growing demand. Primarily used in composite structures, carbon fibers are widely used in the production of woven composite blades for new-generation turbofan engines, particularly woven composite blades for twin-spool turbofan engines.

[0003] During their manufacture, the layers of warp and weft yarns are released as the preform of the blade is created in order to achieve the different thicknesses of the blade. When the blade is released from the loom, a cutting operation is performed on the warp and weft strands. The cut carbon yarns then become waste from the weaving process.

[0004] Thus, for the manufacture of woven composite blades alone, carbon fiber scraps represent a potential of several hundred tons per year distributed across all production plants. Furthermore, these carbon fiber scraps retain their mechanical properties because they have not been subjected to stress. They can be used to manufacture new composite parts.

[0005] Until recently, these carbon fiber scraps were practically unused. Indeed, although recycling channels for such carbon fiber scraps have developed, they are saturated with demand, particularly from the automotive industry. Carbon fiber scraps are therefore undervalued (at around €1 / kg) and the markets for reusing such fibers are still underdeveloped. They are mostly pyrolyzed and then ground into powder, which constitutes fillers for primers, paints, or thermoplastic materials.

[0006] The applicant plans to valorize carbon fibre scraps in order to set up a new sector.

[0007] In document FR-A1-3 133 330, the applicant has developed a semi-finished recycled product based on carbon fiber scraps. The product is presented in the form of the This product consists of a roll of non-woven tape made from carbon fiber scraps 100 mm or less in length, and a binder that ensures fiber cohesion and tape strength. This semi-finished product, as such, cannot be used directly in thermoforming or thermocompression manufacturing processes and must be further processed to be fully utilized. For example, after processing, the product could be used to manufacture semi-structural parts. This type of part is widely used in the aerospace industry, particularly for interiors, cabins, and seats, as well as for panel assemblies. Furthermore, it could be used more broadly in the transportation sector (automotive, marine) or in industrial manufacturing, such as mold making.

[0008] In document FR-A1-3 139 026, the applicant has developed a method for manufacturing a composite plate from carbon fiber scraps. The composite plate has a sandwich structure with layers comprising carbon fiber scraps and a thermoplastic binder.

[0009] Generally speaking, manufacturing a composite plate can be a lengthy process, particularly when the plate comprises several superimposed layers that are bonded together to ensure cohesion between the layers at their interfaces. Thus, even if the plate consists of only three layers of material, a layer of adhesive must be provided between two adjacent layers of material, resulting in a five-layer composite plate (three layers of material and two layers of adhesive). The material layers generally undergo a surface preparation step to improve bonding, which further extends the plate's manufacturing time.

[0010] Moreover, current composite plate technology does not always allow addressing all the designs of aeronautical parts: small radius, double curvature, slope with a large angle (greater than 45°), etc.

[0011] The invention offers an improvement that simplifies the composition and the manufacture of a composite plate of this type, and to address all or part of the problems mentioned above. Summary of the invention

[0012] The invention provides for this purpose a composite plate, particularly for the aeronautical industry, this composite plate having a sandwich structure and comprising:

[0013] - a first layer comprising scraps of non-woven carbon fibers and a thermoplastic binder ensuring the bonding of the fiber scraps together,

[0014] - a second layer comprising scraps of non-woven carbon fibers and a thermoplastic binder ensuring the bonding of the fiber scraps together, and

[0015] - a layer of foam sandwiched between the first and second layers, this the foam layer being made of thermoplastic compatible with that of the first and second layers,

[0016] the layers of the composite plate being bonded together by melting their respective thermoplastic materials at the interfaces between the layers.

[0017] The invention thus proposes to produce the composite plate using three layers. The distinctive feature of the plate is that it includes an intermediate or inner layer of foam, which makes it possible to achieve the desired functional thickness and to lighten the plate while providing it with good mechanical properties.

[0018] The advantages provided by the invention are numerous and include, in particular:

[0019] - a lightening of the plate at iso mechanical performance (in bending particularly);

[0020] - a relatively short manufacturing time, compared to solutions standard, thanks to the use of thermoplastic materials, perfectly compatible with each other, of rapid stamping / thermoforming type processes;

[0021] - the absence of glue at the interface, since the consolidation of the plate is achieved by the thermoplastic bonding; this results in savings in material costs and operating costs within the standard manufacturing range;

[0022] - we eliminate the need to manage the meniscus of glue at the interface between the layers which can be extremely complicated to manage; etc.

[0023] The composite plate according to the invention may comprise one or more of the following features, taken individually or in combination with each other: - the first and second layers have the same composition; - the binder of the first and second layers is polycarbonate (PC); - the foam layer is based on polyethersulfone (PES); - the foam layer has a density between 40 and 130kg / m3; - the foam layer has a compression resistance of between 0.35 and 1.7 MPa (ASTMD1621), and / or a tensile strength between 1.5 and 3.3 MPa (ASTMD1623), and / or a shear strength between 0.6 and 1.7 MPa (ASTMC273);

[0024] — the foam layer has a variable thickness depending on the need and in general greater than the thickness of each of the first and second layers; - the first and second layers each have a thickness between 0.5mm and 4mm, particularly once consolidated; - the foam layer has a thickness between 1mm and 100mm; - the fiber scraps have a length less than or equal to 100mm;

[0025] — the plate is made up of said three layers and does not include any others between the first and second layers;

[0026] — the plate is devoid of a layer of glue.

[0027] The composite plate according to the invention is preferably made up of the three layers mentioned above and therefore does not include any other layers and in particular layers of glue. Brief description of the figures

[0028] Other objects, features and advantages of the invention will become more apparent in the following description, made with reference to the attached figure, in which:

[0029] [Fig-1] [Fig.1] is a very schematic view of a composite plate according to the invention. Detailed description of the invention

[0030] The invention relates to a composite plate 10 which is schematically illustrated in [Fig.1].

[0031] The composite plate 1 is intended for use in manufacturing a part by thermoforming or thermocompression, for example. The part to be manufactured is an industrial part, generally produced in small to medium series. The part can be used in non-structural or semi-structural applications, namely applications in which the part is able to support its own weight while also being able to withstand light external loads. In particular, in the aerospace industry, such properties are desirable because they make it possible to obtain parts with a particularly favorable mechanical strength-to-weight ratio.However, the invention's potential applications extend beyond the aerospace industry, as this type of property is highly sought after in the transportation industry, particularly in the automotive and nautical sectors, and in industrial manufacturing, such as mold making. For example, in the automotive sector, there is a real interest in reducing vehicle weight to simultaneously reduce their energy consumption.

[0032] The composite plate 10 has a sandwich structure and comprises three layers:

[0033] - a first layer 12 comprising scraps of non-woven carbon fibers 14 and a thermoplastic binder ensuring the bonding of the fiber scraps together,

[0034] - a second layer 16 comprising non-woven carbon fiber scraps 14 and a thermoplastic binder ensuring the bonding of the fiber scraps together, and

[0035] - a layer of foam 18 interposed between the first and second layers 12, 16, this foam layer being made of thermoplastic compatible with that of the first and second layers.

[0036] The layers 12, 16, 18 of the composite plate 10 are bonded together by melting their respective thermoplastic materials at the interfaces between the layers.

[0037] The first and second layers 12, 16 can have the same composition.

[0038] The binder of the first and second layers 12, 16 is for example polycarbonate (PC).

[0039] The first and second layers 12, 16 can each have a thickness El between 0.5mm and 4mm.

[0040] Each of the first and second layers 12, 16 can be manufactured as described in document FR-A1-3 133 330 or document FR-A1-3 139 026.

[0041] In document FR-A1-3 133 330, carbon fiber scraps are mixed with a binder to create a fiber mat in which the carbon fibers are bonded together by the binder. The mat is then calendered. The binder initially comes in the form of particles or fibers. In document FRAI-3 139 026, the fiber scraps are combined with a thermoplastic layer.

[0042] The foam layer 18 is preferably based on polyethersulfone (PES).

[0043] The foam layer 18 can have a density between 40 and 130kg / m3.

[0044] The foam layer 18 may have a compression resistance between 0.35 and 1.7 MPa (ASTMD1621), and / or a tensile strength between 1.5 and 3.3 MPa (ASTMD1623), and / or a shear strength between 0.6 and 1.7 MPa (ASTMC273).

[0045] The foam layer 18 preferably has a thickness E2 greater than the thickness El of each of the first and second layers 12, 16.

[0046] The foam layer 18 has a thickness E2 between 1mm and 100mm.

[0047] The fiber scraps 14 preferably have a length less than or equal to 100mm.

[0048] The composite plate 10 is preferably produced by a stamping process, which relies on thermomechanical tooling that assembles, by fusion / consolidation (under pressure), the layers of fibers and foam. The plate is then cooled.

Claims

Demands

1. Composite plate (10), particularly for the aeronautical industry, this composite plate (10) having a sandwich structure and comprising: - a first layer (12) comprising non-woven carbon fiber scraps (14) and a thermoplastic binder ensuring the bonding of the fiber scraps together, - a second layer (16) comprising non-woven carbon fiber scraps (14) and a thermoplastic binder ensuring the bonding of the fiber scraps together, and - a foam layer (18) interposed between the first and second layers (12, 16), this foam layer (18) being made of thermoplastic compatible with that of the first and second layers, the layers (12, 16, 18) of the composite plate (10) being bonded together by melting their respective thermoplastic materials at the interfaces between the layers.

2. Composite plate (10) according to claim 1, wherein the first and second layers (12, 16) have the same composition.

3. Composite plate (10) according to claim 1 or 2, wherein the binder of the first and second layers (12, 16) is polycarbonate (PC).

4. Composite plate (10) according to any one of the preceding claims, wherein the foam layer (18) is based on polyethersulfone (PES).

5. Composite plate (10) according to any one of the preceding claims, wherein the foam layer (18) has a density between 40 and 130kg / m3.

6. Composite plate (10) according to any one of the preceding claims, wherein the foam layer (18) has a compressive strength of between 0.35 and 1.7 MPa (ASTMD1621), and / or a tensile strength of between 1.5 and 3.3 MPa (ASTMD1623), and / or a shear strength of between 0.6 and 1.7 MPa (ASTMC273).

7. Composite plate (10) according to any one of the preceding claims, wherein the first and second layers (12, 16) each have a thickness (El) between 0.5mm and 4mm.

8. 7 Composite plate (10) according to any one of the preceding claims, wherein the foam layer (18) has a thickness (E2) between 1mm and 100mm.

9. Composite plate (10) according to any one of the preceding claims, wherein the fiber scraps (14) have a length less than or equal to 100mm.

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