METHOD FOR RECYCLING A THERMOPLASTIC ORGANIC MATRIX COMPOSITE PART

Abstract

This document relates to a process for recycling a recoverable thermoplastic organic matrix composite part, in particular an end-of-life or damaged part, comprising: introducing (2) said part into a forming tool; heating (4) said part in said tool; applying pressure (5) to said part in said tool; cooling (6) said part in said tool; and removing (7) the recycled part from said tool. Abstract figure: Figure 1

Description

Title of the invention: METHOD FOR RECYCLING A COMPOSITE PART WITH A THERMOPLASTIC ORGANIC MATRIX Technical field

[0001] The present disclosure relates to the field of parts made of thermoplastic organic matrix composite material. Prior art

[0002] In the aeronautical field in particular, a part made of thermoplastic organic composite material undergoes a certain amount of damage. This damage or degradation may be visible, such as impacts or deformations, or occur within the material during aging, decohesion between the matrix and the fibers, intra-matrix cracks or even during delaminations. This damage or degradation within the material leads to a progressive reduction in the mechanical strength of the part. These phenomena are taken into account in order to carry out appropriate dimensioning of the part. For this, fatigue characterizations of the material of the part are carried out.

[0003] At the end of its life, a thermoplastic organic matrix composite part can be destroyed, which is environmentally unfavorable, or it can be recycled. The recycling of such a part consists of grinding the part to reduce the part to chips or granules that can be used in the manufacture of a new part. However, in this case, the mechanical properties of the part material after grinding are degraded compared to those of the original material. Thus, grinding a part made of thermoplastic organic matrix composite material with continuous fibers will give a recycled part having fibers of dispersed lengths between 1 and 50 mm long. Such treatment therefore modifies the stiffness and strength of the recycled part.

[0004] As a result, currently end-of-life thermoplastic organic matrix composite parts are not reused for the same function during recycling. The same applies to thermoplastic organic matrix composite parts that are damaged prematurely during use. Summary

[0005] The present disclosure proposes an additional recycling process suitable for parts whose thermoplastic matrix includes damaged areas (rupture or delamination) while the fibers or the reinforcing fabric is still in good condition. The process of the present disclosure makes it possible in particular to preserve the same function of the recycled part as the original part.

[0006] A method is proposed for recycling a recoverable thermoplastic organic matrix composite part, in particular a part at the end of its life or damaged, comprising: the introduction of said part into a shaping tool; the heating of said part in said tool; applying pressure to said part in said tooling; cooling said part in said tooling, and removing the recycled part from said tooling.

[0007] The present method makes it possible to restore the mechanical properties of a thermoplastic organic matrix composite part. This part may be at the end of its life or damaged in a visible manner, whether by an impact, a break or a deformation, or in a non-visible manner. The defects concerned are of the type decohesion of the fibrous reinforcement with respect to the thermoplastic resin, local plasticization or internal cracks.

[0008] The application of thermocompression, namely heating and application of pressure to said part, makes it possible to promote reconsolidation mechanisms within the part to be recycled.

[0009] In the case where the part is a part with an overmolded part, a step of removing said overmolded part can be carried out before introducing said part into said tooling.

[0010] The removal step may be machining or chemical removal, including chemical stripping with a suitable solvent.

[0011] The PEI Short Fibers part of a part, in PAEK continuous fiber composite, overmolded by a PEI short fiber composite can be solubilized by a chlorine solvent which is ineffective for the PAEK composite.

[0012] In the case of an overmolded part, the method may include overmolding the part before cooling said part.

[0013] The tool for shaping the part to be recycled can be preheated before introducing said part.

[0014] Alternatively or additionally, said part may be preheated before introduction into said tooling.

[0015] When introducing said part into the shaping tool for the part to be recycled, a thermoplastic film or a composite ply with a thermoplastic organic matrix for reinforcement may be added to said part.

[0016] This step ensures sufficient pressure to finish the material in areas to be restored without changing the geometry of the part.

[0017] The part comprising an amorphous thermoplastic matrix, the heating of the part to be recycled can be carried out at a temperature higher than the transition temperature vitreous Tg of said amorphous thermoplastic matrix or, the part comprising a crystalline thermoplastic matrix, the heating of the part to be recycled can be carried out at a temperature higher than the melting temperature Tf of said crystalline thermoplastic matrix.

[0018] This temperature makes it possible to soften the thermoplastic matrix of the part to be recycled.

[0019] The cooling of the part to be recycled can be carried out dynamically and in a controlled manner.

[0020] The removal of the part may be a demolding carried out at a temperature in accordance with the temperature recommended for the manufacture of the part.

[0021] The demolding of the part after restoration will thus be carried out at a temperature identical or close to that used during the initial manufacture of the part.

[0022] The thermoplastic material of the part to be recycled can be PAEK, PEI, PPS, PESU, PSU, PC or PA. In the case of thermoplastic resins of the PAEK or PEI type, for simple thermocompression, the preform and therefore the tooling will be heated to a temperature between 350 and 400°C. For operation on a stamping type, the preform can be heated in an oven, for example infrared to a temperature between 350 and 400°C and stamped in a tooling heated to a temperature between 150 and 250°C.

[0023] For any other material, refer to the material suppliers' data sheets in order to set the appropriate temperatures for the restoration cycle.

[0024] The end-of-life aircraft part provided may be previously manufactured by stamping a stack of thermoplastic organic matrix composite plies, by thermocompression of a long-fiber preform, by thermocompression of a molding compound, or by injection of a resin filled or not filled with short fibers. Brief description of the drawings

[0025] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which: Fig.l

[0026] [Fig.l] represents a first diagram of the recycling process according to the present disclosure. Fig. 2

[0027] [Fig.2] represents a second diagram of the recycling process according to the present disclosure, comprising a step of preheating the shaping tool. Fig. 3

[0028] [Fig.3] represents a third diagram of the recycling process according to the present disclosure, comprising a step of preheating the part and a step of pre- heating of the shaping tool. Fig. 4

[0029] [Fig.4] represents a fourth diagram of the recycling process according to the present disclosure, comprising a step of removing overmolding and a step of overmolding the part. Description of the embodiments

[0030] The present disclosure relates to a method for recycling a recoverable thermoplastic organic matrix composite part. This part is a part at the end of its life or damaged. For example, a part of a commercial aircraft seat structure undergoes, during its use, loads and discharges associated with the movements of passengers, the different phases of flight but also thermal aging and exposure to the external environment with particular hygrometry and temperatures. During this use, the part may be damaged. The damage may be visible, for example impacts, rupture or deformations, or not visible to the naked eye during decohesion of the fibrous reinforcement and the thermoplastic organic matrix, local plasticization or internal cracks. The situation is the same for parts such as supports or bridges made of thermoplastic composite.

[0031] To recycle such parts, the steps of a recycling process will notably include as shown in [Fig.l] after recovery 1 of the end-of-life or damaged part: - the introduction 2 of said part into a shaping tool; - heating 4 of said part in said tool; - applying pressure 5 to said part in said tooling; - the cooling 6 of said part in said tool, and - the removal 7 of the recycled part from said tool.

[0032] Such a method aims to repair the stresses or deformations undergone by the part during its subsequent use. This method also aims to restore the initial mechanical properties of damaged areas of the part at the end of its life. This method restores the thermoplastic organic matrix. This method applies in the case where the fiber reinforcement is not damaged, in particular when the fibers are not broken and in the case where the arrangement of the fibers is not modified.

[0033] To do this, the part is introduced into a shaping tool. The shaping tool has the theoretical shape of the final part. This part undergoes a new cycle of heating and pressure application. This is called thermocompression. These two steps relating to thermocompression contribute directly to the restoration of the thermomechanical properties of the part. These three steps introduction of the part into the shaping tool, heating and applying pressure to said part is carried out directly on the part to be treated in its geometric shape obtained at the end of its life or after having suffered damage.

[0034] The end-of-life or damaged part is a thermoplastic matrix composite part. According to a first example, it is a monolithic part. Such a part can be manufactured by stamping a stack of thermoplastic matrix composite plies, by thermocompression of a preform with discontinuous long fibers, thermocompression of a bulk molding compound, or by injection of a resin filled or not with short fibers. The method does not apply to parts that have suffered significant damage to the fiber reinforcement, such as fiber breakage or a modification of their arrangement.

[0035] We will subsequently distinguish the stages of the process according to the type of initial manufacture of the end-of-life or damaged part.

[0036] Case of a part at the end of its life or damaged initially manufactured by stamping:

[0037] In this case, the end-of-life or damaged part is not obtained by overmolding.

[0038] As illustrated in [Fig.l], in such a configuration, the recycling method is as mentioned above, namely that the end-of-life or damaged part is subjected in particular to a heating and pressure application step. The shaping tool may have the shape of the initial part or be adapted to the shape of the end-of-life or damaged part.

[0039] As shown schematically in the method of [Fig.2], the shaping tooling of the part to be recycled can be preheated 8 before introduction of said part. The preheating temperature of the mold is chosen to facilitate the introduction of the end-of-life or damaged part into the shaping tooling. This temperature also makes it possible to optimize the restoration / repair cycle. Two particular preheating temperature values ​​are to be considered with interest: - the temperature set for the restoration cycle in accordance with the temperature recommended for the manufacture of the part, - the ejection temperature of the part during demolding in accordance with the temperature recommended for the manufacture of the part.

[0040] The temperature of the tooling and the exposure time of the part in the tooling are established so that the thermoplastic organic matrix is ​​brought to the target temperature throughout the part. This step is carried out at a time sufficient to allow the mobility of the polymer chains in the areas to be restored or repaired. This time depends on the thickness of the part to be heated. For example, in the case of thermoplastic resins of the PAEK or PEI type, for simple thermocompression, The shaping tool is heated to a temperature between 350 and 400°C. For operation on a stamping type, the tool is heated to a temperature between 150 and 250°C. For any other material, refer to the material suppliers' data sheets to determine the appropriate temperatures for the restoration cycle.

[0041] The shaping tool may be equipped with dynamic thermal control technology. For example, this dynamic thermal control technology may be the technology proposed by the company Surface Génération Itd (UK) based on regulation by pulsed air or a technology based on induction.

[0042] The shaping tool may comprise at least one pressure sensor. This pressure sensor makes it possible to verify that the process of pressurizing the material is taking place. The restoration operation requires, in fact, imposing sufficient pressure on the material to promote the reconsolidation mechanisms of the material. This minimum pressure must be ensured by the implementation means during the restoration / repair cycle.

[0043] As shown in [Fig.2], when introducing said part into the tool for shaping the part to be recycled, a thermoplastic film or a thermoplastic organic matrix composite ply for reinforcement 9 can be added to said part. This thermoplastic film or thermoplastic organic matrix composite ply makes it possible to ensure sufficient pressure for finishing the material in the areas to be restored without changing the geometry of the part.

[0044] Said part can be preheated 10 before introduction into said tool. This tool can, as mentioned above, also be preheated 8. Such a method is schematically represented in [Fig.3].

[0045] The preheating temperatures of the tooling and the part are chosen to facilitate the introduction of the part into the preheated tooling and to optimize the restoration / repair cycle. The part can be preheated to a temperature up to the glass transition temperature Tg - 10°C for amorphous thermoplastic matrices. The part can be preheated to a melting temperature Tf - 10°C for semi-crystalline thermoplastic matrices. Such a preheating method makes it possible to introduce the part without plastically deforming it.

[0046] The part comprising an amorphous thermoplastic matrix, the heating of the part to be recycled can be carried out at a temperature higher than the glass transition temperature Tg of said amorphous thermoplastic matrix or for which, the part comprising a crystalline thermoplastic matrix, the heating of the part to be recycled can be carried out at a temperature higher than the melting temperature Tf of said crystalline thermoplastic matrix.

[0047] This specific heat treatment makes it possible to soften the thermo- organic matrix plastic.

[0048] An opening of the shaping tool and the step of heating the part before applying pressure to said part can be dynamically controlled. This dynamic control makes it possible to control a proliferation of the material before applying pressure to said part. By proliferation, we mean a recovery in thickness, an increase in the thickness of the treated part compared to the part at the end of its life not yet treated. The proliferation of the preform during the step of heating the part alone allows good reconsolidation when closing the shaping tool.

[0049] The application of pressure can be carried out by a vacuum tank, a membrane or in an autoclave.

[0050] The thickness of the part can be reduced during the thermocompression operation. This ensures that the part is pressurized.

[0051] The cooling of the part to be recycled can be carried out dynamically and in a controlled manner.

[0052] Case of parts initially manufactured by stamping - overmolding:

[0053] We now study the case of a part composed of several materials and initially produced by stamping and overmolding. The part may have been produced in one step if stamping and overmolding take place in the same tool, or in two steps if the part is first stamped and then a preform is introduced into an injection tool to carry out the overmolding.

[0054] In such a case, the recycling process is the same as before. The only difference in this type of configuration is that it is not possible to preheat the part. It is therefore not possible to use an infrared oven at the risk of melting an overmolded part and losing the shape. The part must be introduced cold into a cold shaping tool, i.e. not preheated.

[0055] As illustrated in [Fig.4], the part being a part with an overmolded part, a step of removing said overmolded part 11 can be carried out before introducing said part into said tooling.

[0056] The removal step may be machining or chemical removal. The chemical removal may be carried out using a solvent specific to the thermoplastic matrix used for the overmolded part.

[0057] The method may then include overmolding of the part 12 before cooling said part.

[0058] The overmolded part can be made with a new material. Alternatively, the overmolded part can be made from the previously removed overmolded part. In this second case, it is necessary to grind the overmolded elements to reconstitute granules which can be injected.

[0059] The overmolded part can be produced in the shaping tool or in a dedicated tool.

[0060] Case of a hybrid part:

[0061] A hybrid part is understood to mean a part manufactured with two composite materials that are different in terms of the nature of the fiber reinforcement and / or thermoplastic resin matrix. An example of a hybrid part comprises a PAEK composite with continuous fibers and a PEI composite with short fibers.

[0062] The short fiber thermoplastic overmolded part can be thermally removed.

[0063] We study the case of an overmolded hybrid part. This overmolded hybrid part comprises a material A comprising continuous fibers with a softening temperature higher than a material B used for overmolding. This scenario makes it possible to melt and evacuate the material in the overmolded areas without affecting the continuous fibers which are treated according to the aforementioned method.

[0064] For example, a hybrid part will be defined in which the continuous fiber part is made of PAEK, PEEK or PEKK and the overmolded area will be made of PEI material filled with short fibers. The short fiber component in PEI can be eliminated by melting by heating the part to a temperature above the glass transition temperature Tg of PEI, i.e. 210°C, and below the melting temperature Tf of PEEK, 300°C. Thanks to this process step, only the PEI part will pass into the molten state and can thus be eliminated from the continuous fiber PEEK part.

[0065] The short fiber thermoplastic overmolded part can be chemically removed.

[0066] We study the case of an overmolded hybrid part comprising a material A comprising continuous fibers insensitive to a chemical agent and a material B used for overmolding configured to dissolve with the chemical agent. This chemical removal makes it possible to remove the material B from the part without affecting the material A with continuous fibers. The material A is then treated according to the aforementioned method.

Claims

Claims

1. Method for recycling a recoverable thermoplastic organic matrix composite part, in particular a part at the end of its life or damaged, comprising: - the introduction (2) of said part into a shaping tool; - the heating (4) of said part in said tool; - the application of pressure (5) to said part in said tool; - the cooling (6) of said part in said tool, and - the removal (7) of the recycled part from said tool.

2. Method according to claim 1, for which the part being a part with an overmolded part, a step of removing said overmolded part (11) is carried out before the introduction of said part into said tooling.

3. A method according to claim 2, wherein the step of removing said overmolded portion (11) is machining or chemical removal.

4. Method according to any one of the preceding claims, comprising overmolding the part (12) before cooling said part.

5. Method according to any one of the preceding claims, in which the tooling for shaping the part to be recycled is preheated (8) before introduction of said part.

6. A method according to any preceding claim, wherein said part is preheated (10) before introduction into said tooling.

7. Method according to any one of the preceding claims, in which, when introducing said part into the tool for shaping the part to be recycled, a thermoplastic film or a composite ply with a thermoplastic organic matrix for reinforcement (9) is added to said part.

8. Method according to any one of the preceding claims, for which, the part comprising an amorphous thermoplastic matrix, the heating of the part to be recycled is carried out at a temperature higher than the glass transition temperature Tg of said thermo- matrix amorphous plastic or for which, the part comprising a crystalline thermoplastic matrix, the heating of the part to be recycled is carried out at a temperature higher than the melting temperature Tf of said crystalline thermoplastic matrix.

9. Method according to any one of the preceding claims, in which the cooling (6) of the part to be recycled is carried out dynamically and in a controlled manner.

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