Method, device and computer program for manufacturing elements from chips of recycled elements

Abstract

The invention relates to a method for manufacturing an element made of composite material from chips of at least one first recycled element, the chips being grouped into families according to chip types. After obtaining (125) a plurality of desired characteristics of the element made of composite material and after obtaining, from the desired characteristics and using a knowledge base (135) comprising a set of composition rules, each composition rule associating characteristics of a sample formed of chips of at least one second recycled element with at least one chip type forming the sample and at least one chip arrangement forming the sample, at least one composition rule of the set, at least one chip type and at least one chip arrangement to be used for manufacturing the element made of composite material are estimated (130) using the at least one obtained rule.

Description

[0001] TITLE: Method, device and computer program for manufacturing a composite material element from recycled element chips

[0002] The present invention relates to the field of recycling composite materials, in particular composite materials comprising carbon fibers. It relates in particular to a method, a device and a computer program for manufacturing a composite material element from chips of recycled elements.

[0003] Carbon fiber composite materials are used in many technical fields for their mechanical properties, particularly strength and lightness, for example in the aeronautics, automotive, and nautical sectors, but also in the construction, energy, etc. sectors.

[0004] Carbon fiber composite materials generally consist of carbon fibers embedded in a matrix.

[0005] Several methods can be used to manufacture carbon fibers, the principle being a deposition of carbon at very high temperature, either from paper or viscose ("ex-cellulose" fibers), or from polyacrylonitrile ("ex-PAN" fibers), or from petroleum or coal residues ("ex-pitch" fibers).

[0006] Carbon fibers are included in the matrix in a given orientation, for example unidirectionally, or in the form of woven fiber sheets.

[0007] Regarding the matrix, it is generally made of a polymer or essentially comprises a polymer. The matrix can also be called an "adhesive" or a "resin" (the matrix generally being a polymer). As is well known, the matrix can be thermoplastic or thermosetting in nature.

[0008] Thermosetting polymers undergo a chemical reaction (crosslinking) during the shaping of the composite material, which generates chemical bonds and is irreversible. The most efficient thermosetting polymers for forming a carbon fiber composite material are polyepoxides (known as "epoxies").

[0009] Thermoplastic polymers are polymers that, beyond a certain temperature, called the "phase transition temperature," below their thermal degradation temperature, become viscous and can thus be shaped. When the temperature drops below this phase transition temperature, the polymer hardens and regains its initial stiffness. The transition from the viscous state to the solid state is reversible. The most common thermoplastic polymers are polyethylene (PE), polyethylene terephthalate (PET), or polycaprolactam (PA-6). For certain applications, specialty thermoplastic polymers can be used, such as poly(phenylene ether ketone) (PEEK), poly(phenylene sulfide) (PPS), or polyetherimide (PEI).

[0010] With the numerous and increasingly widespread applications of carbon fiber composite materials, the question of recycling these materials arises. Recycling may concern composite material components at the end of their life or having suffered damage, manufactured components that do not or no longer meet certain standards required for their intended use, or, more rarely, components not used at a certain date.

[0011] To recycle composite materials reinforced with carbon fibers, three main categories of methods have been developed: so-called mechanical recycling, so-called chemical recycling and so-called thermal recycling.

[0012] Mechanical recycling consists, in principle, of breaking up and grinding existing composite material parts to at least partially separate the fibers from the resin, so as to obtain more or less long fibers that can be reused as reinforcement in new resin. The low-fiber particles resulting from grinding, which are in powder form, can be mixed with a resin when forming a new composite material element.

[0013] The crushed composite pieces are used as fillers or reinforcements in molded parts, but are not actually intended to replace virgin carbon fibers as used in conventional composite manufacturing processes (based on non-recycled materials). It is generally accepted that the mechanical properties (flexural strength or flexural stiffness) of a part obtained by a state-of-the-art mechanical recycling process are at least divided by four compared to a similar new part.

[0014] Chemical recycling involves chemically degrading the hardened resin of a composite material in order to recover the carbon fibers present in this material. The recovered fibers are then generally aligned and / or spun to create a yarn from several thousand recovered fibers. The mechanical properties of parts formed from composite materials containing these recycled fibers are significantly lower than those of composite materials containing new, non-recycled carbon fibers. Finally, thermal recycling consists in its principle of thermally degrading the resin of a composite material to recover the carbon fibers. Heat can be provided by a pyrolysis process, which generally consists of burning the resin in a furnace, by a fluidized bed process which uses the combined action of a solvent and a high temperature, and finally by microwaves.

[0015] Although these processes are being optimized, the recovered fibers have significantly degraded mechanical properties compared to new fibers. The recovered fibers are generally short, they must be aligned and spun to be reused in applications requiring correct mechanical characteristics. Otherwise, they are used as fillers, as are, for example, the powders obtained in the mechanical recycling processes mentioned above.

[0016] The present invention aims to propose a method, a device and a computer program for improving the manufacture of a composite material part from chips of recycled elements, the composite material part having high mechanical properties, at a controlled economic and environmental cost.

[0017] Statement of the invention

[0018] The invention relates to the manufacture of a composite material part comprising chips of different types at least partly included in a matrix, arranged so as to obtain predetermined technical characteristics. Each chip has a substantially constant thickness defined between two parallel opposite faces of the chip, each chip comprising carbon fibers at least partly included in an adhesive cured during a first curing prior to the formation of said part. At least a majority of the fibers of the chip extend substantially parallel to the opposite faces of the chip. The matrix in which each chip is at least partly included is formed of an adhesive cured during a second curing. Thus, a bonding interface is formed between the matrix and each chip of the part.

[0019] A first aspect of the invention relates to a method for manufacturing a composite material element from chips of at least one first recycled element, said chips being grouped into families according to chip types, the method comprising,

[0020] - obtaining a plurality of desired characteristics of said composite material element,

[0021] - obtaining, from the desired characteristics, using a knowledge base comprising a set of composition rules, each composition rule associating characteristics of a sample formed from chips of at least one second recycled element with at least one type of chips forming said sample and an arrangement of the chips forming said sample, at least one composition rule of said set, and

[0022] - estimating, using said at least one rule obtained, at least one type and arrangement of chips to be used to manufacture said element in composite material, said elements being elements based on synthetic fibers.

[0023] Thus, from the desired characteristics of an element to be manufactured, it is possible to obtain a composition of chips having different characteristics and an arrangement of the latter making it possible to achieve or tend towards the desired characteristics.

[0024] According to a particular embodiment, the desired characteristics include at least a flexural modulus of elasticity, a flexural strength, a tensile modulus of elasticity, a tensile strength, an interlaminar shear strength, an elastic limit, light polarization properties, heat dissipation properties, acoustic behavior and / or behavior to electromagnetic waves.

[0025] Still according to a particular embodiment, the types of chips are determined according to parameters comprising at least one armor, a linear or surface mass, a mass of the chip, a thickness, a shape, a roughness, a porosity, a surface chemistry, thermal dissipation characteristics, electromagnetic properties and / or light polarization properties.

[0026] Still according to a particular embodiment, the estimation of at least one type of chips comprises the determination of a ratio of chips from different chip families.

[0027] Still according to a particular embodiment, the method further comprises obtaining several composition rules, the estimation comprising an extrapolation or an interpolation from the composition rules obtained.

[0028] Still according to a particular embodiment, the synthetic fibers comprise carbon fibers and / or para-aramid synthetic fibers.

[0029] A second aspect of the invention relates to a method of constructing a knowledge base for the manufacture of a composite material element from chips of at least one first recycled element, the method comprising,

[0030] - obtaining a plurality of parameters characterizing each of the chips of at least one second recycled element,

[0031] - determining chip families according to said plurality of parameters, - estimating characteristics of a sample comprising chips of said at least one second recycled element,

[0032] - the determination of at least one composition rule associating the estimated characteristics with at least one type of chips included in said sample and an arrangement of the chips included in said sample, a type of chips corresponding to a family of chips and

[0033] - the storage of said at least one determined composition rule in said knowledge base.

[0034] The method according to the invention thus allows the establishment of rules allowing the manufacture of composite material elements having particular characteristics, from recycled elements, for example according to the manufacturing method described previously.

[0035] According to a particular embodiment, the characteristics of said sample comprise at least a flexural modulus of elasticity, a flexural strength, a tensile modulus of elasticity, a tensile strength, an interlaminar shear strength, an elastic limit, light polarization properties, heat dissipation properties, acoustic behavior and / or behavior to electromagnetic waves.

[0036] Still according to a particular embodiment, the types of chips are determined according to parameters comprising at least one reinforcement, a linear or surface mass, a mass of the chip, a thickness, a shape, a roughness, a porosity, a surface chemistry, and / or thermal dissipation characteristics, electromagnetic properties and / or light polarization properties.

[0037] Still according to a particular embodiment, the composition rule associates the characteristics with a ratio of types of chips forming said sample and an arrangement of the chips forming said sample.

[0038] Still according to a particular embodiment, said estimation of characteristics of a sample comprises a simulation of said sample.

[0039] Still according to a particular embodiment, said estimation of characteristics of a sample comprises a manufacture of said sample and at least one measurement (435) of said manufactured sample. Said sample may be an element made of composite material manufactured according to the manufacturing method described previously.

[0040] Still according to a particular embodiment, the method further comprises a repetition, for different samples, of the steps of estimating characteristics, determining at least one composition rule and storing said at least one rule. Still according to a particular embodiment, the method further comprises a repetition, for different samples, of the step of estimating characteristics and comprising a modification of at least one previously stored composition rule.

[0041] A third aspect of the invention relates to a device configured to implement the methods described above. The advantages provided by this device are similar to those described previously with regard to the methods.

[0042] A computer program, implementing all or part of the method described above, installed on pre-existing equipment, is in itself advantageous, since it allows easy and rapid access and selection of an event likely to interest a user.

[0043] Thus, the present invention also relates to a computer program comprising instructions for implementing the method described above, when this program is executed by a processor.

[0044] This program may use any programming language (e.g., an object language or otherwise) and be in the form of interpretable source code, partially compiled code, or fully compiled code.

[0045] Another aspect relates to a non-transitory storage medium of a computer-executable program, comprising a data set representing one or more programs, said one or more programs comprising instructions for, upon execution of said one or more programs by a computer comprising a processing unit operatively coupled to memory means and to an input / output interface module, to execute all or part of the method described above.

[0046] Brief description of the drawings

[0047] Other characteristics, details and advantages of the invention will appear on reading the detailed description below. This is purely illustrative and must be read in conjunction with the appended drawings, in which: Figure 1 schematically illustrates an example of steps in a method for manufacturing an element made of composite material from chips of recycled elements, according to embodiments of the invention; Figure 2 schematically illustrates an example of steps for preparing chips of recycled elements, according to embodiments of the invention; Figure 3 illustrates examples of arrangements of chips having different characteristics, in particular different sizes; Figure 4 illustrates an example of steps for constructing and updating a rule base for defining manufacturing parameters, for example types of chips and their arrangement, from characteristics of an element to be manufactured;and Figure 5 illustrates an example of a device that can be used to implement, at least partially, embodiments of the invention, in particular steps described with reference to Figures 1, 2 and 4.;

[0048] Detailed description

[0049] In general, the invention relates to the manufacture of a part made of composite material comprising different types of chips at least partly included in a matrix, arranged in a particular way during the manufacture of the part so that the types of chips and their arrangement make it possible to obtain the desired characteristics for the part, in particular particular mechanical characteristics.

[0050] According to some embodiments, each chip has a substantially constant thickness defined between two parallel opposite faces of the chip, each chip comprising carbon fibers at least partially included in an adhesive cured during a first curing prior to the formation of said part. At least a majority of the fibers of the chip extend substantially parallel to the opposite faces of the chip. The matrix in which each chip is at least partially included may be formed of a thermosetting adhesive crosslinked during a second curing, or of a cured thermoplastic adhesive. In this case, a bonding interface is formed between the matrix and each chip of the part.Alternatively, if each chip comprises carbon fibers at least partly included in a thermoplastic adhesive cured during a first curing prior to the formation of said part, no adhesive is added and the matrix is ​​formed from the thermoplastic adhesive of each chip of the part.

[0051] The bonding interface may essentially comprise mechanical adhesion bonds (mechanical anchoring such as physical anchoring of the adhesive in the asperities of the solid surface of the chips), as well as possibly a diffusion bond (diffusion of the adhesive in the chip) and / or a thermodynamic type bond, in particular of the “Van der Waals” type.

[0052] Throughout this document, the term "substantially" conventionally refers to the perception of that characteristic according to the system used for its measurement or manufacture. If a characteristic is observed with the naked eye, the term "substantially" therefore refers to an observer's perception of that characteristic. An expression containing the term "substantially" must be interpreted as a technical characteristic produced within the tolerance margin of its manufacturing method. In particular, the "substantially parallel" character between two elements can be understood to within 10° of angle. If the fiber considered is included in a fabric (typically taffeta, twill or satin), the direction of extension of the fiber is considered by neglecting the fiber undulations related to the weaving.

[0053] By "chips at least partly included in a matrix", it is specified that each chip is embedded in the matrix, with the possible exception of certain chips that may emerge on the surface of the part. Similarly, by "carbon fibers at least partly included in an adhesive cured during a first curing" it is specified that the carbon fibers are embedded in the adhesive of a chip, with the possible exception of certain fibers that may emerge on the surface of the chip.

[0054] Suitable adhesives for composite materials may be selected from the group consisting of thermosetting resins such as epoxy resins, cyanate ester resins, and phenolic resins. Suitable epoxy resins include bisphenol A diglycidyl ethers, bisphenol F diglycidyl ethers, epoxy novolac resins and N-glycidyl ethers, glycidyl esters, aliphatic and cycloaliphatic glycidyl ethers, glycidyl ethers of aminophenols, glycidyl ethers of any substituted phenols, and mixtures thereof. Also included are modified blends of the aforementioned thermosetting polymers. By "modified blend" is meant a polymer modified, typically by the addition of rubber or thermoplastic.

[0055] Any suitable catalyst (or "hardener") can be used. The catalyst will be chosen to match the resin used. The catalyst can be accelerated. For example, when a dicyandiamide catalyst is used, a substituted urea can be used as an accelerator.

[0056] The curing agent with epoxy resin may also be selected from Dapsone (DDS), Diamino-diphenyl methane (DDM), BF3-amine complex, substituted imidazoles, accelerated anhydrides, metaphenylenediamine, diaminodiphenyl ether, aromatic polyetheramines, aliphatic amine adducts, aliphatic amine salts, aromatic amine, adducts and salts of aromatic amines. Suitable accelerators include Diuron, Monuron, Fenuron, Chlortoluron, toluenediisocyanate bis-urea and other substituted homologues.

[0057] Suitable adhesives for composite materials can also be selected from the group consisting of thermoplastic resins. Thermoplastics can be divided into high-performance plastics, engineering plastics, and standard plastics. Most thermoplastics used in composite materials are high-performance plastics or engineering plastics. These plastics differ from standard plastics in particular by their greater wear resistance and chemical resistance. However, standard thermoplastics can offer advantages, such as polypropylene combined with glass fibers (GF / PP) or SrPP and SrPET (Self-Reinforced Polypropylene and Self-Reinforced Polyethylene terephthalate), because their glass transition temperature is not very high.

[0058] Thermoplastics, depending on their nature, can be hard in amorphous or crystalline form. Commonly used amorphous thermoplastics in composite materials include polyetherimides (PEI), polyethersulfone (PES), polysulfones (PSU), polycarbonates (PC), and polycarbonate / acrylonitrile butadiene styrene (PC / ABS). Commonly used crystalline thermoplastics in composite materials include polyamides (PA), polyethylene (PE), polyethylene terephthalate (PTA), polyphthalamide (PPA), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK).

[0059] Each chip is formed so that the majority of its fibers are oriented parallel to the chip faces. This allows the fibers to be of significant length and have a controlled orientation within the chip. Ultimately, the length and orientation of the fibers in the chips, and the arrangement of the chips within the part, give it high mechanical properties.

[0060] The chips can in particular be obtained by cutting into carbon fiber composite material elements to be recycled, as explained in more detail below. The formation of a part in accordance with the invention therefore allows the recycling of such elements, using a low-pollution mechanical process, while providing good mechanical performance to the formed part.

[0061] The faces of each chip may have a surface area, called the chip surface, of at least 10 mm 2These values, given as examples, are understood as minimums. Depending on the parts considered, the chips may have a much larger surface area, for example around 3 cm 2 , 5 cm 2 , 10 cm 2 , or 20 cm 2 , 100 cm 2 The chips formed and used here thus have a large surface area, allowing the inclusion of very long carbon fibers since the latter extend substantially parallel to the opposite faces of the chip.

[0062] Each chip advantageously has a small thickness (e) compared to its other dimensions. A chip being thus an essentially two-dimensional part, of small thickness, its other dimensions typically correspond to the largest dimension (d) measurable on the surface of the chip and to the dimension measured perpendicularly, also on the surface of the chip. The ratio (e)Z(d) is for example between 0.2 and 0.0001 and preferably between 0.06 and 0.0005. It is noted that unless otherwise indicated, the ranges are understood to be inclusive.

[0063] In the composite material part, the carbon fibers advantageously extend mainly in parallel planes. Furthermore, the chips may have a unidirectional arrangement of the carbon fibers, in two distinct directions, for example a first direction and a second direction forming an angle of 90° between them, or in multiple directions, it being observed that a controlled orientation of the chips and therefore of the fibers in the part allows the desired mechanical properties to be obtained. In addition, the chips may be arranged in the part in a repetitive pattern, corresponding to a particular relative arrangement of several chips.

[0064] The carbon fibers present in each chip can be arranged in sheets each having a weave of carbon fibers.

[0065] In the composite material part, the shape and dimensions of the chips used are chosen to achieve the desired mechanical properties. For illustration, each chip can be substantially rectangular in shape (i.e. the faces of each chip are substantially rectangular) with several different sizes.

[0066] The thickness of the chips can, for example, be between 100 pm and 1 mm.

[0067] The composite material may include fibrous areas, formed by the chips and representing between 20% and 85% by volume of the part and non-fibrous areas, made up of the adhesive added and hardened during the second hardening, forming the rest of the part. A part made of composite material may include:

[0068] - a plurality of zones comprising carbon fibers and a first adhesive, the carbon fibers having a non-random orientation within the same zone, and all of the carbon fibers of said zones being oriented along substantially parallel planes, and

[0069] - at least one zone devoid of carbon fibers, comprising a second adhesive, the plurality of zones comprising carbon fibers and a first adhesive being at least partly included in the at least one zone devoid of carbon fibers comprising a second adhesive, that is to say that the second adhesive of the at least one zone devoid of carbon fibers encompasses at least 75%, preferably at least 80%, even more preferably at least 85% such as for example 90%, of the surface of the plurality of zones comprising carbon fibers and the first adhesive.

[0070] Areas with carbon fibers can also be distributed throughout the composite part in a pattern.

[0071] The first adhesive may be the same as the second adhesive, the first adhesive having cured before the second adhesive, or different.

[0072] The composite material part can, for example, be a flat or curved panel.

[0073] Figure 1 schematically illustrates an example of steps of a method for manufacturing a composite material element from recycled element chips according to embodiments of the invention.

[0074] As illustrated, the process here comprises three phases: a phase 100 of cutting the elements to be recycled into chips, a phase 105 of manufacturing preparation to determine in particular the chips to be used and their arrangement and a phase 110 of manufacturing.

[0075] According to the illustrated example, the phase of preparing the chips to be used for the manufacture of an element comprises a step of cutting the elements to be recycled into chips (step 115) and a step of classifying the chips obtained into families (step 120). The elements to be recycled are elements based on synthetic fibers, for example elements based on carbon fibers and / or para-aramid synthetic fibers such as Kevlar fibers (Kevlar is a trademark). By way of illustration, the examples described essentially concern carbon fibers.

[0076] The chips are obtained by cutting the elements to be recycled (step 115), for example by mechanical cutting. The cutting of the chips can be carried out using a cutting machine such as a blade device, for example of the planer type, comprising a blade for separating thin slices of regular thickness from the surface of an element over which it is passed. The material to be cut is positioned in the cutting machine according to the organization of the carbon fibers it contains.

[0077] If the fibers in the material to be cut are unidirectional, i.e., included in a matrix substantially parallel, in a single direction, then the fibers may be positioned parallel to the direction of advance of the blade device. If the fibers are included in the form of woven sheets, the workpiece is preferably placed such that the weft or warp threads are substantially parallel to the direction of advance of the blade device. The fibers may also be arranged in a succession of layers, each layer comprising unidirectional fibers, but the layers having different fiber orientations. This is the case, for example, for so-called "four-directional" materials, the layers of which may have the following successive relative orientations: 0° (reference layer), 90°, 45°, -45°.The blade device can then be adjusted so that its blade attacks the element between two layers of fibers, whether two layers of unidirectional fibers or two woven webs.

[0078] The slices obtained may in particular have a thickness of between 200 pm and 1 mm, preferably between 200 pm and 500 pm.

[0079] The items to be recycled can be cut to the desired length for chips before being cut into slices by the cutting machine, so that chips of the desired length are obtained directly from the cutting machine.

[0080] Alternatively, the slices are then re-cut to obtain chips. Typically, they are cut transversely by any suitable cutting means, for example by sawing, to form thin rectangular chips of regular length. Other chip shapes can of course be cut from the resulting slices.

[0081] For example, for the production of flat panels, chips of 10 cm to 20 cm in length can be obtained and allow very good results to be obtained in terms of mechanical performance. Longer lengths can also be implemented, such as around 50 cm, or even 1 m.

[0082] Of course, the cutting process described above can be adapted according to the application considered and the quantities to be produced.

[0083] When the material to be recycled is a pre-coated, but uncured, carbon fiber fabric, this material may first be cured (polymerized for a material coated with a thermosetting resin) and then cut to the desired chip shape. Alternatively, it may be cut to the desired chip shape and then cured. Alternatively, it may be cut to the desired chip shape without being subsequently cured. Such a fabric generally having a thickness of between 200 μm and 500 μm, the chip thus obtained has a thickness entirely suitable for use according to the present invention for forming a part, in particular a molded part, made of composite material.

[0084] Once the chips are formed, they are therefore in the form of fine elements comprising carbon fibers included, at least in part, in a resin. The chips are therefore in the form of substantially two-dimensional parts (in that their thickness is very small compared to its other dimensions). The surface area of ​​the chips is advantageously at least 10 mm 2 , and preferably greater than 3 cm 2 , of the order of 10 cm 2 , or even higher, for example up to 100 cm 2 approximately.

[0085] When the hardening of the chip matrix is ​​prior to the formation of the final part by molding, we speak of first hardening (in order to distinguish it from the hardening of the part matrix, which aims to bind the chips, and which will be carried out during the molding of the part).

[0086] The carbon fibers are oriented in the resin of the chips. Preferably, they are substantially parallel, orthogonal to each other, and / or oriented at 45° to each other.

[0087] Since the fibers of the chips have a substantially constant thickness, they have two opposite faces (between which the thickness is defined). The cutting of the chips is carried out in such a way as to keep the carbon fibers intact as much as possible. To achieve this, the cutting of the chips is carried out in such a way that the fibers (in their majority, or even in their quasi-totality or their totality) extend parallel to the opposite faces of the chips. The fibers thus extend in planes parallel to the general plane of extension of the chip, and can have a great length despite the low thickness of the chips.

[0088] By "majority" we mean more than 50% in number and by "almost all" we mean more than 90% in number.

[0089] Several cutting machines or several settings of the same cutting machine can be used to cut parts to be recycled into chips of varying sizes and shapes. Therefore, as illustrated in Figure 2, several types of cutting can be implemented, for example n types of cutting referenced here 115-1 to 115-n. Combined with different parts to be recycled and different arrangements of the fibers in these parts, this results in chips having different characteristics in terms of sizes, in terms of arrangement of the fibers, etc. and therefore in terms of mechanical characteristics.

[0090] In order to improve the use of the chips obtained, the latter are grouped into categories or families, for example into p families according to the example illustrated in Figure 2 (referenced 200-1 to 200-p), according to their characteristics, for example according to their thickness, their dimensions, their shape, their mass, their linear or surface mass, the orientation of the fibers (e.g., unidirectional or woven), the reinforcement (e.g., twill, plain, satin, etc.), their roughness, their porosity, their surface chemical properties, their heat dissipation characteristics, their electromagnetic properties, their light polarization properties, etc. By way of illustration, the chips can be grouped according to the following families: where the value of parameter E1 is greater than that of parameter E2.

[0091] Other parameters can be taken into account. Furthermore, the number of families is not necessarily equal to 5. It can be lower or higher than this value.

[0092] According to other embodiments, the chips are divided into families and sub-families, according to two or more levels of depth, the families being linked to one or more first criteria, for example the orientation of the fibers, the sub-families being linked to one or more second criteria, for example the dimensions of the chips, and so on. Returning to Figure 1 and in a following phase (phase 105), the characteristics, for example the mechanical characteristics, of the composite material element to be manufactured from chips of recycled elements are obtained (step 125) and an analysis is carried out to identify manufacturing parameters (step 130), for example the types of chips to be used and their distribution.

[0093] Characteristics of the composite material element to be manufactured (step 125) may be obtained directly from technical specifications of the element, for example a file from an application such as a computer-aided design application and / or may be provided by a user, for example via a graphical interface. They may also be determined from other characteristics of the element to be manufactured. Such characteristics of the element to be manufactured include for example a flexural modulus of elasticity, a flexural strength, a tensile modulus of elasticity, a tensile strength, an interlaminar shear strength, a yield strength, dimensions, light polarization properties, heat dissipation properties, acoustic behavior, electromagnetic wave behavior, etc.

[0094] These characteristics are then used to determine manufacturing parameters (step 130). According to particular embodiments, a rule engine or an artificial intelligence engine is used. By way of illustration, a rule engine containing rules associating characteristics of elements to be manufactured from chips with manufacturing parameters such as types of chips to be used and their distribution, stored for example in a database 135, can be used to select one or more rules and identify manufacturing parameters, for example by applying the closest rule or by extrapolation from two (or more) closest rules.

[0095] Such rules include, for example:

[0096] These rules, or some of them, can be defined by specialists and / or users. They can also be automatically entered into the database from measurements or simulation, as described below with reference to Figure 4.

[0097] Figure 3 illustrates examples of chip arrangements having different characteristics, including different sizes. Of course, many other arrangements are possible and other chip sizes or shapes can be used. It is observed here that the chips can be placed relative to each other precisely or randomly or pseudo-randomly, for example according to given directions and / or densities. It is thus possible to provide that all the chips of the same family are placed on the same layer, for example an external surface of the element to be manufactured, in the same direction (which can be defined relative to the element to be manufactured or to a direction of other chips), with certain densities in certain regions of the element to be manufactured and other densities in other regions of the element to be manufactured.

[0098] Returning to Figure 1 and at the end of manufacturing preparation phase 105, manufacturing phase 110 can begin.

[0099] As illustrated, this phase includes a first step of preparing the adhesive and, optionally, coating (step 140).

[0100] In this step, after obtaining the chips corresponding to the manufacturing parameters determined previously, the chips can be mixed with a liquid adhesive in order to coat them, with a view to their molding (it being noted that the adhesive can be provided in different ways, for example in the form of a spray, by casting, etc.). In this case, if chips from several families are used, they are preferably mixed with the liquid adhesive by family so that they can be arranged in a mold according to the manufacturing parameters determined, for example in layers.

[0101] This step can be carried out before the chips are placed in the mold intended to form the desired part, or during or even after placement in the mold. By way of illustration, the production of parts conforming to embodiments of the invention on a pilot or prototype scale is described below. In this example, the chips are mixed with an adhesive before being placed in a mold. On a prototype scale, the mixing can be carried out manually in a suitable container, for example made of aluminum. The mixing is preferably vigorous or mechanized in order to homogenize the thickness of adhesive on each chip.

[0102] The chips can first be weighed into the container, then the adhesive (e.g., a resin / hardener system, see below) is prepared and added. Coating is complete when each chip is well and evenly coated with adhesive. Adding the adhesive and mixing the chips and adhesive can be done automatically. An automatic mixer can be used to mix the chips and adhesive.

[0103] The amount of adhesive to be added to the chips is determined by the characteristics of the part (e.g., panel) to be produced. The amount of adhesive to be added depends, for example, on the desired volume or mass percentage of chips in the final material, to obtain the desired mechanical properties, and on the adhesive used, particularly its density. The masses applied can also be determined by the panel thicknesses to be obtained.

[0104] For many applications where high mechanical performance is required, it is important to maximize the proportion of chips in the material. The inventors have produced parts containing up to 80% chip mass percentage and estimate that parts containing up to 85% chip mass percentage, or even slightly more, can be successfully produced.

[0105] Various adhesives can be used. Generally, all adhesives known to be used as a matrix in composite materials containing carbon fibers can be used, with the possible exception of adhesives that would be incompatible with the cured adhesive present in the chips. By incompatible, it is understood that the adhesive used would cause an unwanted chemical reaction with the cured adhesive present in the chips or would be poorly suited to forming mechanical bonds with the chips. For example, two-part epoxy system adhesives can be used. Such two-part epoxy systems comprise an epoxy resin and a hardener. When the resin and the hardener are brought into contact, polymerization begins. The polymerization time varies depending on the nature of the system used.

[0106] A first two-component epoxy system mentioned as an example is the system marketed by the company SIKA under the name ADEKIT H9011 (ADEKIT is a registered trademark). The transparency of the adhesive once cured allows the chips to be seen in the final part. A second two-component epoxy system mentioned as an example is a system marketed by the company SICOMIN under the name "EPOXY RESIN SR 1700 + STANDARD HARDENER SD 2803".

[0107] As indicated above, many adhesives can be used for the formation of parts in accordance with various embodiments of the invention. In particular, systems intended for composite production applications (infusion, injection, lamination resins), but also systems intended for structural applications as adhesives. The systems may in particular have a density of between 1.03 and 1.38 at 25°C. Their dynamic viscosity may in particular be between 0.4 and 80 Pa.s. They may in particular have a modulus of elasticity (once cured) of between 2 GPa and 4 GPa. The polymerization of these adhesives can take place at room temperature or at a higher temperature, of the order of 70°C. Since the polymerization times are significantly different depending on the thermosetting adhesive system, the choice of the system may also depend on this time, according to the mechanical properties and the desired cycle times.

[0108] The additive(s) may also include fillers. Fillers refer to all the particulate elements that can be added to the adhesive to modify its properties and / or to lower its cost for the same volume. The fillers considered include, in particular, mineral or organic particles that can improve certain properties of the final part, in particular its resistance to scratching or abrasion.

[0109] These fillers are most often of a mineral nature (aluminum, calcium, etc.) in the form of particles whose size is in the order of nanometers or micrometers. The adhesive may also include glass microbeads.

[0110] The filler used may also contain carbon dust, for example from the preparation and cutting operations of the elements to be recycled. In this case, it is therefore an organic filler.

[0111] Such additives may be provided in the rules used to determine certain manufacturing parameters such as chip types and their positioning.

[0112] The mixture of chips and adhesive is then molded.

[0113] Alternatively, according to particular embodiments, the chips and adhesive are deposited in the mold without prior mixing. A first layer of resin is deposited in the mold manually or automatically. A layer of chips is then arranged, with a predefined pattern, manually or automatically. The layers of adhesive and chips are thus alternated until the desired thickness is obtained. A first way to deposit the resin in the mold is to use a casting method. The resin and the hardener are contained in two independent tanks, and sent to a mixing head by pumps. The two products then meet at the end of the mixing head, in a static mixer, to be deposited in the mold in the form of a bead. Another way to deposit the resin in the mold is the spraying method.The principle is the same as the casting method, but compressed air is applied through a nozzle at the end of the static mixer in order to atomize the bead of adhesive formed in the form of droplets which will be deposited in the mold.

[0114] Overmolding can be performed. To do this, at the end of polymerization, resin is injected into the mold to cover the molded part and obtain a specific surface finish. The high injection pressure during overmolding can allow functional elements to be added to the surface of the molded part (grooves, notches, rails, etc.) or to create the desired surface appearance. Overmolding can also be performed on another mold of the “insert molding” type. As an alternative or in addition to overmolding, a gel coat (or gel coating) can be applied to the mold or a top coat (or finishing coating) can be applied to the part once it has been molded.

[0115] For illustration purposes, it is considered here that the composite material element to be manufactured is a flat panel. The mold used has a concave part, called the female impression, and a part forming a corresponding male impression.

[0116] Before the chips are placed, a release agent can be applied to the internal surface of the mold to facilitate the extraction of the part once it has been formed. Once the chips have been mixed with the adhesive, they should be placed in the female cavity of the mold (step 145), for example according to the manufacturing parameters determined in step 130, then finalize the press molding (steps 150 and 155).

[0117] Depending on the planned production scale, chip placement can be carried out manually, using templates or visual markers (e.g. laser-formed guides), or automatically.

[0118] The adhesive-coated chips are placed in the female cavity of the mold on an extraction plate. The extraction plate allows the panel to be extracted from the mold after the pressing action. It can also be used to adjust the thickness of the panel being formed (several thicknesses can be achieved in the same mold by varying the thickness of the extraction plate). If an extraction plate is used, it forms the internal surface of the mold and it will therefore be the extraction plate that will be coated with release agent if necessary.

[0119] The step of arranging the chips in the mold is important, particularly to enable the manufactured part to have the desired mechanical properties. It must be carried out according to the determined manufacturing parameters.

[0120] Assuming that the chips have unidirectional carbon fibers, the chips can be arranged in the mold randomly, unidirectionally (the chips are all arranged in the same direction, with a certain tolerance, for example, in the order of plus or minus 10° or with less than 10% of the chips not respecting the desired orientation and angle tolerance) or multidirectionally (with similar tolerances where appropriate). Figure 3 illustrates examples of multidirectional fiber arrangements.

[0121] A multidirectional arrangement may consist of making several plies (each comprising one or more layers of chips) with different chip orientations between adjacent plies. For example, with rectangular chips, it is possible to alternate the plies, with a chip arrangement of one ply at 90° to the chips of the adjacent plies. According to certain embodiments, a multidirectional arrangement may therefore be defined as a stack of unidirectional layers as described above.The example at the top left of Figure 3 partially represents three plies (only some chips of each ply are shown to illustrate the stacking of the chips), namely an upper ply in which the chips are oriented in a first direction (x), an inner ply in which the chips are oriented in a direction (y) orthogonal to the direction (x) and a lower ply in which the chips are oriented in the first direction (x). The chips of the flat panel taken here as an example are positioned parallel to the plane (x,y). According to other embodiments, the chips are nested within each other, not forming a stack of unidirectional layers, like the example at the bottom left of Figure 3.

[0122] The arrangements presented above concern a flat panel of small thickness. For the formation of a part having a significant thickness (for example a cube) or having a complex three-dimensional shape, it is also possible to position chips orthogonally to the extension planes for molding, forming a random, unidirectional or multidirectional configuration as described above. These chips, which extend in the thickness of the part, increase the mechanical properties of the part in their direction of extension. Considering an orthogonal coordinate system (x,y,z), as shown in Figure 3, the majority of the chips being oriented in planes parallel to the (x,y) plane, the chips positioned orthogonally, in the z direction (for example parallel to the (x,z) plane or to the (y,z) plane), thus mechanically strengthen the part in the z direction.

[0123] Generally speaking, the arrangement of the chips, provided it is not purely random, can be such that the chips form a particular pattern which is repeated to form the panel (or more generally a piece).

[0124] A pattern corresponds to a particular arrangement of several chips between them in three dimensions. Thus, with the exception of a purely random arrangement, the other arrangements considered (unidirectional, bidirectional, multidirectional, with possibly a three-dimensional arrangement of chips, etc.) can be considered as the repetition of a chip pattern.

[0125] The arrangement, geometry, size of the chips used and the thickness of the plies can be adapted according to the intended application and thus, according to the characteristics of the element to be manufactured. The arrangement, geometry and size of the chips used can also be determined, in particular for an external ply and at least in part, according to aesthetic criteria. Thus, for example, the arrangement, geometry and size of the chips of an external ply can be chosen to form a particular geometric pattern such as a logo.

[0126] To some extent, the longer the chips, the better the mechanical properties. However, in practice, the length of chips that can be formed and used depends on the elements being recycled and the elements to be manufactured, and in particular on their geometric complexity (it is obvious that it is easier to integrate very long chips into a large flat panel than into a curved part with complex geometry and / or many geometric details). Generally speaking, it is advantageous to use chips whose largest dimension, such as length, is between 3 and 20 cm.

[0127] Once the chips are placed in the female cavity of the mold, the mold is closed by positioning the male cavity. The mold is then installed in a press, which is activated to pressurize the contents of the mold (step 150). Prototype panels were produced by applying pressure between 1 and 50 bar.

[0128] When using a thermosetting resin, polymerization can take place at room temperature. However, the mold can be heated to accelerate polymerization. To achieve efficient and uniform heating (a temperature of around 70°C may be desired), two heating plates can be used, one on either side of the mold. To regulate the heating and take into account the exothermic nature of the adhesive polymerization, a closed-loop control, for example PID (proportional, integral, derivative) type, can be used.

[0129] A first curing step preferably takes place while the mold is under pressure (step 150). Some adhesives, depending on their nature, require a second air curing step (step 160), also known as post-curing.

[0130] For the ADEKIT H9011 system, the polymerization time is 16 hours at 70°C. For comparison, the complete polymerization of this adhesive takes around a week at room temperature.

[0131] The process described above thus allows the manufacture of molded parts made of composite material formed from elements made of composite material based on synthetic fibers, for example carbon fibers or para-aramid fibers, to be recycled.

[0132] The process described above involves molding the part. Alternatively, other shaping techniques can be used. For example, a pultrusion process or a calendering process can be used.

[0133] Figure 4 illustrates an example of steps for building and updating a rule base to define manufacturing parameters, for example chip types and their arrangement, from characteristics of an element to be manufactured.

[0134] As illustrated, the first step here is a step of obtaining characteristics of an element to be manufactured, in particular technical characteristics such as mechanical characteristics, for example identical or similar to step 125 described with reference to FIG. 1.

[0135] A test is then performed to determine whether manufacturing parameters are imposed or not (step 400), for example entered by a user, for example via a graphical interface. If manufacturing parameters are not imposed, a test is performed to determine whether the characteristics obtained from the element to be manufactured are close to characteristics of at least one rule stored in the rule base 135 described with reference to FIG. 1. To determine whether the characteristics obtained from the element to be manufactured are close to characteristics of at least one stored rule, the difference can be compared, parameter by parameter, with thresholds, the characteristics obtained from the element to be manufactured being considered as not close to characteristics of at least one stored rule if at least one difference is greater than the corresponding threshold.Alternatively, the differences are accumulated, possibly with weighting, and compared with a single threshold. Other criteria can be used to estimate the proximity of the obtained characteristics concerning the element to be manufactured and the characteristics of the rules.

[0136] If manufacturing parameters are imposed or if the characteristics obtained from the element to be manufactured are not close to characteristics of at least one stored rule, a next step consists of obtaining the manufacturing parameters (step 410). As described previously, these parameters can be entered by a user, for example through a graphical interface. These parameters include for example one or more types of chips to be used and their arrangement or information making it possible to determine these types of chips and their arrangement.

[0137] If, on the contrary, manufacturing parameters are not imposed and if the characteristics obtained from the element to be manufactured are close to characteristics of at least one stored rule, a following step consists of obtaining manufacturing parameters (step 415), for example from the rule associated with the closest characteristics or by extrapolation from values ​​provided by rules (for example 2 or 3 rules) associated with the closest characteristics.

[0138] By way of illustration, if the characteristics of an element to be manufactured include significant resistance to mechanical stress exerted in a single longitudinal direction and a woven appearance on the outside, it can be determined that these characteristics are close to those referred to in rule 2 of the table provided previously comprising an example of rules, to which are associated manufacturing parameters indicating types of chips to be used and their proportions, here 80% chips from family 1 and 20% chips from family 2, the chips from family 2 being for example placed on the outer layers and the chips from family 1 being for example arranged in an inner layer.

[0139] After obtaining the manufacturing parameters and if these do not include types of chips to be used and their arrangement, the type(s) of chips to be used and their arrangement are determined from the parameters obtained (step 420).

[0140] A test is then performed to determine whether the element to be manufactured must actually be manufactured or whether it must be simulated (step 425). This choice can be made automatically, for example according to the context, or made by a user, for example via a graphical interface. When the choice is made automatically, it may nevertheless be necessary for it to be validated by a user. According to certain embodiments, an element to be manufactured is manufactured and simulated.

[0141] After the element has been manufactured (step 430), if it is to be, certain of its characteristics are measured (step 435), for example its flexural modulus of elasticity, its flexural strength, its tensile modulus of elasticity, its tensile strength, its interlaminar shear strength, its yield strength, its dimensions, etc., to enable the establishment of a link between these characteristics and the manufacturing parameters of this element.

[0142] Similarly, if the element to be manufactured must be simulated, some of its characteristics are estimated (step 440), typically the same as those measured on a manufactured element, to, again, allow the establishment of a link between these characteristics and the manufacturing parameters of this element.

[0143] In a subsequent step (step 445), the rule base, for example rule base 135, is updated. This step may consist of modifying an existing rule, for example to add one or more parameters or one or more characteristics or to adjust a range of values ​​of one or more parameters or one or more characteristics. This update may also consist of adding a rule. These modifications or additions may be made automatically, if necessary after validation by a user. Alternatively, these modifications or additions may be made by a user on the basis of the manufacturing parameters of the element and the measured or simulated characteristics. These parameters and characteristics may be presented to a user via a graphical interface that he can also use to modify a rule that he has chosen or that has been automatically selected or to add a new rule.In other embodiments, the rules engine is replaced or used in addition to an artificial intelligence engine, for example an artificial neural network whose inputs are the characteristics of the element to be manufactured and whose outputs are the manufacturing parameters. Such an engine can be trained with measured or simulated characteristics and corresponding manufacturing parameters.

[0144] This rule base and / or this artificial intelligence engine constitute a knowledge base which makes it possible to estimate the manufacturing parameters of a composite material element from recycled element chips according to the characteristics of the element to be manufactured.

[0145] Figure 5 illustrates an example of a device that can be used to implement, at least partially, embodiments of the invention, in particular steps described with reference to Figures 1, 2 and 4.

[0146] The device 500 is for example a server, a computer, a terminal or a personal device such as a smartphone or a tablet.

[0147] The device 500 preferably comprises a communication bus 502 to which are connected:

[0148] - a central processing unit or microprocessor 504 (CPU, acronym for Central Processing Unit in Anglo-Saxon terminology);

[0149] - a 506 read-only memory (ROM, acronym for Read Only Memory in English terminology) which can contain an operating system and programs such as "Prog";

[0150] - a random access memory or cache memory 508 (RAM, acronym for Random Access Memory in English terminology) comprising registers adapted to record variables and parameters created and modified during the execution of the aforementioned programs; and

[0151] - a communication interface 526 connected to a distributed communication network 528, for example a wireless communication network and / or a local communication network, the interface being capable of transmitting and receiving data, in particular to and from a user's device.

[0152] Optionally, the device 500 may also have the following elements:

[0153] - a hard disk 520 which may contain the aforementioned "Prog" programs and data processed or to be processed according to the invention; - a keyboard 522 and a mouse 524 or any other pointing device such as an optical pen, a touch screen or a remote control allowing the user to interact with the programs according to the invention;

[0154] - a reader 510 of removable storage media 512 such as a memory card or a disk, for example a DVD disk; and

[0155] - a 514 graphics card connected to a 516 screen.

[0156] The communication bus allows communication and interoperability between the different elements included in the device 500 or connected to it. The representation of the bus is not limiting and, in particular, the central unit is capable of communicating instructions to any element of the device 500 directly or via another element of the device 500.

[0157] The executable code of each program enabling the programmable device to implement the processes according to the invention may be stored, for example, in the hard disk 520 or in read-only memory 506.

[0158] According to a variant, the executable code of the programs may be received via the communication network 528, via the interface 526, to be stored in a manner identical to that described previously.

[0159] More generally, the program(s) may be loaded into one of the storage means of the device 500 before being executed.

[0160] The central unit 504 will control and direct the execution of the instructions or portions of software code of the program(s) according to the invention, instructions which are stored in the hard disk 520 or in the read-only memory 506 or in the other aforementioned storage elements. When the power is switched on, the program(s) which are stored in a non-volatile memory, for example the hard disk 520 or the read-only memory 506, are transferred into the random access memory 508 which then contains the executable code of the program(s) according to the invention, as well as registers for storing the variables and parameters necessary for implementing the invention.

[0161] Depending on the embodiment chosen, certain acts, actions, events or functions of each of the methods described herein may be performed or occur in a different order than that in which they were described, or may be added, merged or not performed or not occur, as the case may be. Furthermore, in certain embodiments, certain acts, actions or events are performed or occur concurrently and not successively. Although described through a number of detailed exemplary embodiments, the proposed method and the equipment for implementing the method include various variations, modifications and improvements which will be apparent to those skilled in the art, it being understood that these various variations, modifications and improvements are part of the scope of the invention, as defined by the following claims.In particular, while the examples presented are related to elements to be recycled and manufactured based on synthetic fibers, the invention can be implemented with other types of fibers, including natural fibers such as flax fibers and / or mineral fibers such as glass or basalt fibers. In addition, different aspects and features described above can be implemented together, or separately, or substituted for each other, and all different combinations and sub-combinations of the aspects and features are within the scope of the invention. Furthermore, some systems and equipment described above may not incorporate all of the modules and functions described for the preferred embodiments.

Claims

CLAIMS 1. Method for manufacturing a composite material element from chips of at least one first recycled element, said chips being grouped into families according to chip types, the method comprising, - obtaining (125) a plurality of desired characteristics of said composite material element, - obtaining, from the desired characteristics, using a knowledge base (135) comprising a set of composition rules, each composition rule associating characteristics of a sample formed from chips of at least one second recycled element with at least one type of chips forming said sample and an arrangement of the chips forming said sample, at least one composition rule of said set, and - estimating (130), using said at least one rule obtained, at least one type and arrangement of chips to be used to manufacture said element in composite material, said elements being elements based on synthetic fibers.

2. Method according to claim 1, according to which the desired characteristics comprise at least a flexural modulus of elasticity, a flexural strength, a tensile modulus of elasticity, a tensile strength, an interlaminar shear strength, an elastic limit, light polarization properties, heat dissipation properties, acoustic behavior and / or behavior to electromagnetic waves.

3. A method according to claim 1 or claim 2, wherein the chip types are determined according to parameters comprising at least one of armor, linear or surface density, chip mass, thickness, shape, roughness, porosity, surface chemistry, heat dissipation characteristics, electromagnetic properties and / or light polarization properties.

4. A method according to any one of claims 1 or 3, wherein estimating at least one type of chips comprises determining a ratio of chips from different chip families.

5. Method according to any one of claims 1 or 4, the method further comprising obtaining several composition rules, the estimation comprising an extrapolation or an interpolation from the obtained composition rules.

6. A method according to any one of claims 1 or 5, wherein the synthetic fibers comprise carbon fibers and / or para-aramid synthetic fibers.

7. Method for constructing a knowledge base for the manufacture of a composite material element from chips of at least one first recycled element, the method comprising, - obtaining a plurality of parameters characterizing each of the chips of at least one second recycled element, - determining (120) chip families according to said plurality of parameters, - the estimation (435, 440) of characteristics of a sample comprising chips of said at least one second recycled element, - determining (445) at least one composition rule associating the estimated characteristics with at least one type of chips included in said sample and an arrangement of the chips included in said sample, a type of chips corresponding to a family of chips and - the storage of said at least one determined composition rule in said knowledge base.

8. The method of claim 7, wherein the characteristics of said sample include at least one of flexural modulus of elasticity, flexural strength, tensile modulus of elasticity, tensile strength, interlaminar shear strength, yield strength, light polarization properties, heat dissipation properties, acoustic behavior and / or electromagnetic wave behavior.

9. A method according to claim 7 or claim 8, wherein the chip types are determined according to parameters comprising at least one of reinforcement, linear or surface mass, chip mass, thickness, shape, roughness, porosity, surface chemistry, and / or heat dissipation characteristics, electromagnetic properties and / or light polarization properties.

10. A method according to any one of claims 7 to 9, wherein the composition rule associates the characteristics with a ratio of chip types forming said sample and an arrangement of the chips forming said sample.

11. A method according to any one of claims 7 to 10, wherein said estimation of characteristics of a sample comprises a simulation (440) of said sample.

12. Method according to any one of claims 7 to 11, according to which said estimation of characteristics of a sample comprises a fabrication (430) of said sample and at least one measurement (435) of said fabricated sample.

13. The method of claim 12, wherein said sample is a composite material element manufactured according to the method of any one of claims 1 to 6.

14. Method according to any one of claims 7 to 13, the method further comprising a repetition, for different samples, of the steps of estimating characteristics, determining at least one composition rule and storing said at least one rule.

15. Method according to any one of claims 7 to 13, the method further comprising a repetition, for different samples, of the step of estimating characteristics and comprising a modification of at least one previously stored composition rule.

16. Computer program comprising instructions for implementing each of the steps of the method according to one of claims 1 to 11, when this program is executed by a processor.

17. Device comprising a processing unit configured to execute each of the steps of the method according to one of claims 1 to 15.

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