WO2012085000A1

WO2012085000A1 - Process for recycling a composite material part and system for the implementation thereof

Info

Publication number: WO2012085000A1
Application number: PCT/EP2011/073475
Authority: WO
Inventors: Amélie DARFEUILLE; Jacques Cinquin
Original assignee: European Aeronautic Defence And Space Company Eads France
Priority date: 2010-12-21
Filing date: 2011-12-20
Publication date: 2012-06-28
Also published as: FR2969027A1; FR2969027B1

Abstract

The invention relates to a process for recycling a part made of a composite material having a thermoplastic matrix reinforced by continuous fibres, comprising the following operations: cutting (10) the part to be recycled (1) into lamella along a plane containing fibres, cutting (20) the lamella into chips of predefined dimensions, insertion (30) of the chips into a mould of predetermined shape, and hot pressing (40) of the chips in the mould in order to obtain a recycled part (2). It also relates to a recycling system implementing this process.

Description

METHOD FOR RECYCLING A COMPOSITE MATERIAL PART AND ITS IMPLEMENTING SYSTEM

Field of the invention

The invention relates to a method for recycling a composite material part and, in particular, a piece of thermoplastic matrix composite material reinforced with continuous fibers. This method allows a transformation of a composite material part into strips of composite material that can be reused to manufacture new parts made of composite material. The invention also relates to a system for implementing this method.

The invention has applications in the field of recycling and, in particular, in the field of recycling thermoplastic matrix composite materials reinforced with continuous fibers.

State of the art

Currently, for ecological reasons, we try to recycle as much as possible the waste produced by man. Composite materials are an increasingly important part of non-recycled waste. Indeed, the development of composite materials is recent. The first pieces of composite materials, produced a few years ago, arrive today at the end of their life and become waste. As the use of these composite materials, replacing the metal, has experienced a very strong growth in recent years, in many sectors such as automotive and aerospace, the number of end-of-life parts will evolve rapidly in the coming years.

Currently, this waste is not recycled and is dumped, which generates pollution. Some of these composite parts are large parts, such as wing panels, or fuselages of aircraft in future years, and their landfill will involve increasing amounts of material, which is a real problem. It is therefore important, to limit these discharges and the pollution they produce, to be able to recycle the composite material parts.

More and more pieces of composite material are made of a material comprising a thermoplastic matrix. This thermoplastic matrix has a reversible liquid solid transition; it can therefore be implemented. It is therefore possible to recycle composite parts end of life or scrap composite material not used in the production of parts.

Currently, there are few techniques for recycling composite material parts. One of these techniques consists in grinding the composite parts at the end of their life in order to transform said parts into a powder or a coarse ground material which can be added, as a filler, in the manufacture of new composite material parts, for example BMC type (Bulk Molding Compound, in Anglo-Saxon terms). However, these powders and ground materials being used only as additional load in the manufacture of new parts, all parts made of composite material can not be recycled with such a process.

Another recycling technique for composite materials proposes recycling recycled carbon fibers pre-impregnated with a PEEK (Polyetheretherketone) matrix. Such a technique is described in the article "Recycling of APC-2 Offcuts" by R. J. Day, A.K. Wood and S. F. Pang, Manchester Materials Science Center, Grosvenor Street, Manchester, MI 7HS, UK. It involves shredding the unused scrap of new composite materials in order to make a short-fiber reinforced PEEK injection compound by adding pure PEEK using a bis-screw extrusion process. However, this technique only allows to use falls of composite materials, that is to say the parts of a composite material not used to produce a new part. It does not allow any recycling end of life parts and therefore does not solve the problems of landfilling these parts.

Another technique proposes to grind waste from a pre-impregnated composite material for reuse in the manufacture of another composite material plate by means of a compression molding process. This technique is described in the article "Recycling Carbon-Fiber-Reinforced Thermoplastic Composites, G. Schinner, J. Brandt and H. Richter, Journal of Thermoplastic Composite Materials 1996; 9; 239. However, this technique only makes it possible to obtain a grind of composite material, with short fibers that do not make it possible to obtain a plate having good mechanical properties. The plates thus obtained have very few applications.

Presentation of the invention

The purpose of the invention is precisely to overcome the disadvantages of the techniques described above. To this end, the invention provides a method for recycling the composite material parts, including those at the end of life, by cutting these parts into slats that can be molded by hot pressing to make new parts.

More specifically, the invention relates to a method for recycling a piece of thermoplastic matrix composite material reinforced with continuous fibers, characterized in that it comprises the following operations:

cutting of the piece to be recycled into strips according to a plane containing fibers,

cutting slices into chips of predefined size, inserting the chips into a mold of predetermined shape, and

- hot compression of the chips in the mold to obtain a recycled part.

This method has the advantage of allowing the recycling of all the composite material parts to be recycled to make new parts.

The method of the invention may include one or more of the following features:

- The cutting of the coin to be recycled is made parallel to the surface of said piece.

- The slats are flat and have a predefined geometry. This characteristic can allow automation of the cutting of the chips lamellae.

the slats are cut into a predefined width and thickness. In this way, the slats can have dimensions adapted to the manufacturing mold of the new part. - The chips are inserted into the mold so that their fibers are parallel to the plane of the mold, which allows, after hot compression, that the fibers of the chips are bonded together.

the chips are cut according to a geometry adapted to the shape of the mold.

the cutting of the slats in the part to be recycled can be carried out plan by plane, over the entire thickness of said part.

The invention also relates to a system for recycling a piece of thermoplastic matrix composite material reinforced with continuous fibers to implement the method described above. This system comprises:

a slat cutting machine capable of cutting a piece to be recycled into slices according to a plane containing fibers,

a chipping machine capable of cutting the slices into chips of predefined dimensions,

a mold capable of receiving chips, and

- Compression tooling adapted to the mold and able to heat compress the chips in the mold to obtain a recycled part.

According to one embodiment of the invention, the cutting machine of this system comprises a mandrel capable of holding a cutting blade of a width adapted to the width of the slats to be cut.

According to other embodiments of the system, the cutting machine may comprise means for moving the mandrel capable of linearly moving the cutting blade along the length of the workpiece to be recycled and over the width of said workpiece.

The cutting blade of this cutting machine can be inclined at an angle greater than 90 ° with respect to the advancing path of said blade.

The cutting machine of the system of the invention can integrate the chip machine, the cutting blade of the cutting machine being driven by a rotary movement associated with a rectilinear movement parallel to the surface of the workpiece to be recycled for directly allow chip cutting of said part. Brief description of the drawings

Figure 1 shows a functional diagram of the recycling process of the invention.

FIG. 2 diagrammatically represents a cutting machine enabling the method of FIG. 1 to be implemented.

Figure 3 shows schematically the different machines of the recycling system of the invention.

Description of Detailed Embodiments of the Invention

The invention relates to a method for recycling end-of-life composite material parts and / or scrap or composite material scrap in order to manufacture new composite material parts. This process relates in particular to parts made of a thermoplastic matrix composite material reinforced with continuous fibers, such as glass fibers or carbon fibers, for example.

This recycling process, represented in functional form in FIG. 1, comprises an operation 10 of slicing the component 1 made of composite material to be recycled. This piece 1 may be a piece at the end of life or a fall or rebus composite material or other composite material to recycle. The cutting operation 10 slices consists of cutting the piece 1 in thin layers, called slats. The width and the thickness of these lamellae are modifiable parameters, in particular as a function of the part to be recycled, of the new part to be manufactured and / or of the cutting tool used. The length of the slats may be identical to the length of the part 1 to be recycled; this length can also be predefined according to the new part to be manufactured and / or the cutting tool used.

Whatever these parameters of width, length and thickness, the slats are cut in a plane containing the fibers. The slats are thus cut in a plane parallel to the surface of the part 1, this plane containing the fibers in their greatest length. Such cutting allows to maintain a relatively long fiber length.

In the preferred embodiment of the invention, the operation 10 consists of delaminating the part 1 to be recycled, over the entire length of said piece, in slats of constant thickness and width. The thickness of these strips may be of the order of 0.1 to 1 mm. The width may be of the order of 15 to 20 mm.

As shown in FIG. 1, an operation 20 then consists in cutting these strips into chips. The dimensions of the chips can be chosen according to the dimensions of the new part to be manufactured. These dimensions can also be standard so as to be easily adaptable to all kinds of new parts to be manufactured. These chips of predefined size have the advantage of being easy to use for the manufacture of new parts, whatever the dimensions of these new parts. They have especially the advantage of having relatively long fibers compared to the fibers of the ground materials of the prior art. The fibers of the chips of the invention have a maximum length equal to the largest dimension of the chips. The chips obtained according to the process of the invention have a predefined and reproducible geometry, which makes it easy to use them for the manufacture of a new piece of composite material. They also have fibers long enough to provide the new part with correct mechanical properties, for example impact resistance, breaking stress, etc.

After cutting, one operation is to install the chips in a mold of a predetermined shape corresponding to the shape of the new part to be manufactured. These chips can be arranged randomly in the mold. However, they are arranged so as to always maintain a fiber direction parallel to the plane of the mold.

An operation 40 then consists in molding the chips by hot pressing according to a compression technique known in the field of composite materials. The hot compression cycle used depends on the thermoplastic material considered. During this cycle, the thermoplastic matrix returns to the molten state and flows inside the mold, which makes it possible to bind the fibers of each chip between them thus forming a homogeneous material, without porosity.

Compression tooling, adapted to the mold, is used in order to heat compress the chips in the mold, under a pressure of the order of 10 to 50 bar This compression tool may be a press heating, or any other means of hot compression usually used in the field of composite materials.

Once compressed, the chips constitute a new part 2. This new part 2 may have new functions in the same field as the original part or in a different technical field.

The method of the invention makes it possible, by means of slit cutting, to obtain fibers of relatively long length which make it possible to manufacture a new part, or recycled part, having sufficiently good mechanical properties to be used in some technical areas. Indeed, the mechanical properties of the new parts are lower than those of the initial parts, made with a new composite material, but they are sufficient to meet certain specifications, in applications or sectors where the mechanical strength may be lower. The method of the invention may, in particular, be applied to the manufacture of secondary structure parts such as aerodynamic elements of fuselage wing junctions on an aircraft, or parts subject to little structural effort such as the fins and shutters of aircraft, or for parts of interior fittings of aircraft.

The method of the invention may be implemented by a recycling system represented in FIG. 3 and comprising:

a slat cutting machine 4 making it possible to cut the piece to be recycled 1 into strips according to a plane containing fibers,

a chipping machine 5 making it possible to cut the slats into chips of predefined dimensions,

a mold 6 for receiving the chips and whose shape is adapted to that of the recycled part to be manufactured, and

- Compression tooling 7 of shape adapted to the mold 6 and for hot compressing the chips in the mold to obtain the selected recycled part.

More specifically, the cutting slats, according to the method of the invention is performed by means of a cutting machine. This cutting machine can be any machine for cutting layers of a material. An example of a cutting machine is shown in Figure 2. In this example, the cutting machine 4 comprises a mandrel 4a supporting a cutting blade 4b. Displacement means 4d are fixed, on the one hand, to the mandrel 4a and, on the other hand, to a motor (not shown in the figure) in order to ensure a linear displacement of the cutting blade 4b via the mandrel 4a. The displacement means 4d ensure at least one bidirectional displacement of the cutting blade, that is to say a displacement in the X direction corresponding to the length of the workpiece 1 and a displacement in the Y direction corresponding to the width of the workpiece. said part 1.

In one embodiment of the invention, the displacement means 4d also provide a displacement along the thickness of the workpiece 1 to allow cutting of the workpiece 1 in thickness. In another embodiment, the part 1 to be recycled rests on a movable plate capable of moving the part 1 in a direction Z corresponding to the thickness of said part 1.

The cutting blade 4b of the cutting machine 4 is a blade of great strength. This blade is preferably metal, for example hardened steel. It is fixed on the mandrel 4a by means of fixing means 4c, according to a predefined inclination. The positioning of the blade along the Z axis defines the thickness of the lamellae. In addition, the inclination of the blade has a direct impact on the flatness of the cut slats: the more the blade is inclined towards the surface of the room to be recycled and the slices are easily cut out. This inclination must be at an angle greater than 1 35 ° with respect to the path of advance of the blade, that is to say with respect to the axis X. In the example of FIG. cutting blade 4b is inclined about 140 ° relative to the advancing path of said blade.

The cutting blade 4b can be fixed inclined relative to the mandrel, its inclination relative to the plane of the part 1 to be recycled then being obtained at the attachment 4c of the blade on the mandrel; it can also be fixed rectilinear with respect to the mandrel, its inclination then being obtained thanks to the displacement means 4d.

In a preferred embodiment of the invention, the cutting blade 4b is interchangeable. In this way several blades widths different can be installed on the machine to allow the cutting of slats of different widths.

The angle of inclination of the cutting blade and its advancing speed may be parameterizable data so as to produce different planes of flatness depending on the intended application. These two parameters are preferably optimized to obtain the most flat slats possible.

The lengthwise displacement of the cutting blade can also be parameterized so that slices of different lengths can be cut according to the intended application.

Once the blade chosen, the forward speed and inclination parameterized, the machine 4 cut slats of identical geometry.

According to the invention, the slats are then cut into chips by means of a chipping machine 5. This chipping machine can be a conventional machine.

In one embodiment of the invention, the slat cutting machine 4 integrates the chip machine. For this, the cutting blade 4b is driven by a rotary movement (planer type) associated with a rectilinear movement parallel to the surface of the workpiece to be recycled to directly allow cutting chips of said workpiece.

It is understood from the foregoing that the recycling process of the invention can be automated to provide a continuous cutting of slats along the entire surface of the workpiece 1 to be recycled and then over the entire thickness of said workpiece. In other words, the automation of the method of the invention can provide for a rectilinear displacement of the cutting blade along the length of the workpiece 1 to be recycled, in the direction of the fibers of said workpiece 1, in order to produce a first blade and then a lateral displacement to cut a second lamella along the length of the piece 1, etc. Once the surface of the part is totally cut off, the cutting is continued slice by slat by the next surface of the piece. The cutting of the workpiece is thus carried out plan by plan, over the entire thickness of the workpiece 1 to be recycled. It should be noted that the cutting of the workpiece 1 can also be done thickness by thickness, over the entire surface of the workpiece 1. The slices thus cut are then recovered automatically to be automatically cut into chips. The process which has just been described makes it possible to manufacture new pieces of composite material which are almost isotropic, that is to say whose properties do not vary with the direction. In addition, although the mechanical properties of these new parts are lower than the properties of the parts from which they are derived, these properties are sufficient to meet the specification of non-structural parts or secondary structures that do not require extreme stresses.

Claims

1. Process for recycling a piece of thermoplastic matrix composite material reinforced with continuous fibers, characterized in that it comprises the following operations:

- cutting (10) of the piece to be recycled (1) into slats in a plane containing fibers,

- Cutting (20) slats into chips of predefined dimensions,

inserting (30) the chips into a mold of predetermined shape, and

- Hot pressing (40) of the chips in the mold to obtain a recycled part (2).

2. Recycling process according to claim 1, characterized in that the cutting of the workpiece to be recycled is made parallel to the surface of said workpiece.

3. recycling process according to any one of claims 1 to 2, characterized in that the lamellae are flat and have a predefined geometry.

4. recycling process according to any one of claims 1 to 3, characterized in that the slats are cut in a predefined width and thickness.

5. recycling process according to any one of claims 1 to 4, characterized in that the chips are inserted into the mold so that their fibers are parallel to the plane of the mold.

6. Recycling process according to any one of claims 1 to 5, characterized in that the chips are cut in a geometry adapted to the shape of the mold.

7. Recycling process according to any one of claims 1 to 6, characterized in that the cutting of the slats in the room to be recycled is carried out plan by plane, over the entire thickness of said room.

8. Recycling system of a piece of thermoplastic matrix composite material reinforced with continuous fibers, suitable for implementing the method according to any one of claims 1 to 7, characterized in that it comprises:

- A lamella cutting machine (4) adapted to cut a workpiece to be recycled (1) in strips in a plane containing fibers,

a chipping machine (5) able to cut the slices into chips of predefined dimensions,

a mold (6) capable of receiving chips, and

- Compression tooling (7) adapted to the mold and capable of hot compressing the chips in the mold to obtain a recycled part.

9. Recycling system according to claim 8, characterized in that the cutting machine (4) comprises a mandrel (4a) adapted to maintain a cutting blade (4b) of a width adapted to the width of the lamellae to be cut

10. Recycling system according to claim 9, characterized in that the cutting machine (4) comprises means (4d) for moving the mandrel capable of linearly moving the cutting blade (4b) along a length of the part to be recycled. (1) and the width of said piece.

1 1. Recycling system according to claim 9 or 10, characterized in that the cutting blade (4b) of the cutting machine is inclined at an angle greater than 90 ° with respect to the advancing path of said blade.

Recycling system according to claim 9 or 10, characterized in that the cutting machine (4) incorporates the chip machine (5), the cutting blade (4b) of the cutting machine being driven by a rotary movement associated with a rectilinear movement parallel to the surface of the part to be recycled to allow a chip cutting of said part directly.