Composite plate for the aeronautical industry

Abstract

The invention relates to a composite plate (10), in particular 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 bonding the fiber scraps to one another; - a second layer (16) comprising non-woven carbon fiber scraps (14) and a thermoplastic binder bonding the fiber scraps to one another; and - a foam layer (18) positioned 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.

Description

[0001] DESCRIPTION

[0002] TITLE: COMPOSITE PLATE FOR THE AERONAUTICAL INDUSTRY

[0003] Technical field of the invention

[0004] The invention relates to a composite plate, particularly for the aeronautical industry, this composite plate being made from carbon fiber scraps.

[0005] Technical background

[0006] The technical background includes, in particular, EP-B1-0 798 102, JP-A-2013 230579 and FR-A1-3 133 330.

[0007] Carbon fiber consumption has exploded over the past ten years. Production has adapted to meet this 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.

[0008] During their manufacture, the layers of warp and weft yarns are gradually released as the blade preform is created, in order to achieve the desired blade thickness. Once the blade is removed from the loom, the warp and weft strands are cut. The cut carbon yarns then become waste from the weaving process.

[0009] 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.

[0010] Until recently, these carbon fiber scraps were practically unused. While recycling channels for such carbon fiber scraps have developed, they are saturated with demand, particularly from the automotive industry. Consequently, carbon fiber scraps are undervalued (at around €1 / kg), and the market for their reuse remains limited. Most are pyrolyzed and then ground into powder, which is used as filler in primers, paints, or thermoplastic materials.

[0011] The applicant plans to valorize carbon fiber scraps in order to set up a new industry.

[0012] In document FR-A1-3 133 330, the applicant has developed a semi-finished recycled product based on carbon fiber scraps. The product is in the form of a roll of non-woven tape containing carbon fiber scraps 100 mm or less in length and a binder that ensures the cohesion of the fibers and the tape's strength. This semi-finished product, as such, cannot be used directly in a thermoforming or thermocompression manufacturing process and must be transformed to be fully utilized. For example, after transformation, 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, or for panel assemblies.In addition, it could be more widely used in the field of transport (automotive, nautical) or in industrial manufacturing, for example the manufacture of molds.

[0013] In document FR-A1-3 139 026, the applicant has developed a process 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.

[0014] Generally speaking, manufacturing a composite plate can be time-consuming, especially when the plate comprises several superimposed layers bonded together to ensure cohesion at their interfaces. Thus, even if the plate consists of only three layers of material, an adhesive layer is required between two adjacent layers, resulting in a five-layer composite plate (three layers of material and two layers of adhesive). The material layers typically undergo a surface preparation step to improve bonding, further extending the plate's manufacturing time. Moreover, current composite plate technology does not always accommodate all aeronautical component designs: small radii, double curvature, steep slopes (greater than 45°), etc.

[0015] The invention proposes an improvement which simplifies the composition and manufacture of a composite plate of this type, and addresses all or part of the problems mentioned above.

[0016] Summary of the invention

[0017] The invention provides for this purpose a composite plate, particularly for the aeronautical industry, this composite plate having a sandwich structure and comprising:

[0018] - a first layer comprising non-woven carbon fiber scraps and a thermoplastic binder ensuring the bonding of the fiber scraps together,

[0019] - a second layer comprising non-woven carbon fiber scraps and a thermoplastic binder ensuring the bonding of the fiber scraps together, and

[0020] - a layer of foam sandwiched between the first and second layers, this layer of foam being made of thermoplastic compatible with that of the first and second layers, the layers of the composite plate being bonded together by melting their respective thermoplastic materials at the interfaces between the layers.

[0021] The invention thus proposes to produce the composite plate using three layers. The plate's distinctive feature 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.

[0022] The advantages offered by the invention are numerous and include:

[0023] - a reduction in the plate weight while maintaining the same mechanical performance (particularly in bending);

[0024] - a relatively short manufacturing time, compared to standard solutions, thanks to the use of thermoplastic materials, perfectly compatible with each other, and rapid stamping / thermoforming processes;

[0025] - the absence of glue at the interface, since the consolidation of the plate is done by the thermoplastic bond; this saves material cost and operation in the standard manufacturing range; - we avoid the management of the glue meniscus at the interface between the layers which can be extremely complicated to manage; etc.

[0026] The composite plate according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0027] - the first and second layers have the same composition;

[0028] - the binder of the first and second layers is polycarbonate (PC);

[0029] - the foam layer is based on polyethersulfone (PES);

[0030] - the foam layer has a density between 40 and 130kg / m 3 ;

[0031] - the foam layer has a compressive strength 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);

[0032] - the foam layer has a variable thickness depending on the need and is generally greater than the thickness of each of the first and second layers;

[0033] - the first and second layers each have a thickness between 0.5mm and 4mm, particularly once consolidated;

[0034] - the foam layer has a thickness between 1 mm and 100 mm;

[0035] - the fiber scraps have a length less than or equal to 100mm;

[0036] - the plate consists of the aforementioned three layers and does not include any others, in particular between the first and second layers;

[0037] - the plate is devoid of a layer of glue.

[0038] 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.

[0039] Brief description of the figures

[0040] Other objects, features and advantages of the invention will become clearer in the following description, made with reference to the attached figure, in which:

[0041] [Fig.1] Figure 1 is a very schematic view of a composite plate according to the invention.

[0042] Detailed description of the invention The invention relates to a composite plate 10 which is schematically illustrated in figure 1.

[0043] Composite plate 1 is intended for use in manufacturing parts by thermoforming or thermocompression, for example. The part to be manufactured is an industrial part, generally produced in small to medium batches. 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 allow for the production of 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 marine sectors, and in industrial manufacturing, such as mold making. For example, in the automotive sector, there is a significant interest in reducing vehicle weight to simultaneously lower fuel consumption.

[0044] The composite plate 10 has a sandwich structure and consists of three layers:

[0045] - a first layer 12 comprising non-woven carbon fiber scraps 14 and a thermoplastic binder ensuring the bonding of the fiber scraps together,

[0046] - a second layer 16 comprising non-woven carbon fiber scraps 14 and a thermoplastic binder ensuring the bonding of the fiber scraps to each other, and

[0047] - a layer of foam 18 interposed between the first and second layers 12, 16, this layer of foam being made of thermoplastic compatible with that of the first and second layers.

[0048] 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.

[0049] The first and second layers 12, 16 can have the same composition.

[0050] The binder for the first and second layers 12, 16 is, for example, polycarbonate (PC). The first and second layers 12, 16 can each have a thickness E1 between 0.5 mm and 4 mm.

[0051] 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.

[0052] 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 FR-A1-3 139 026, the fiber scraps are combined with a thermoplastic layer.

[0053] The foam layer 18 is preferably based on polyethersulfone (PES).

[0054] The foam layer 18 can have a density between 40 and 130kg / m³ 3 .

[0055] The foam layer 18 can have a compressive strength 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).

[0056] The foam layer 18 preferably has a thickness E2 greater than the thickness E1 of each of the first and second layers 12, 16.

[0057] The foam layer 18 has a thickness E2 between 1 mm and 100 mm.

[0058] Fiber scraps 14 preferably have a length less than or equal to 100mm.

[0059] The composite plate 10 is preferably produced by a stamping process, which relies on thermomechanical tooling that will assemble, 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 to each other, and - a layer of foam (18) interposed between the first and second layers (12, 16), this layer of foam (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 joined together by fusion of their respective thermoplastic materials at the interfaces between the layers.

2. Composite plate (10) according to claim 1, in which 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, in which the foam layer (18) has a density between 40 and 130 kg / m³ 3 .

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 (E1) between 0.5mm and 4mm.

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

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.

10. Composite plate (10) according to any one of the preceding claims, wherein the foam layer has a thickness greater than the thickness of each of the first and second layers.

11. Composite plate (10) according to any one of the preceding claims, wherein it is constituted by said three layers and does not comprise any others, in particular between the first and second layers.

12. Composite plate (10) according to any one of the preceding claims, wherein it is devoid of an adhesive layer.

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