CH711201B1 - Composite material for timepieces and jewelery. - Google Patents

Abstract

The invention relates to a composite material for the production of parts, comprising at least a first layer (10) formed of unidirectional sheets of synthetic filaments preimpregnated with a thermosetting resin (100, 101, 102, 110, 111, 112), the unidirectional webs having a first orientation, and at least a second layer (20) formed by a thin sheet of a metallic material. The invention also relates to a method for producing a composite part, comprising at least two layers. The invention also relates to a watch component or a piece of jewelery obtained from such a composite material.

Description

Description

Field of the Invention [0001] The present invention relates to the technical field of composite materials based on unidirectional webs. More specifically, the invention relates to a material for the production of timepieces and jewelery, and a method of manufacturing composite parts from a stack of such a material, and the parts obtained.

BACKGROUND OF THE INVENTION [0002] Many composite materials exist on the market and are known for their mechanical properties as well as their lightness. One of these composites is the thin-ply prepreg composite which can be formed of glass filaments, carbon or aramid which are previously coated with a thermosetting resin.

[0003] Thin-ply prepreg composites generally comprise several unidirectional sheets superimposed on each other at different angles. A unidirectional web consists exclusively or almost exclusively of synthetic filaments deposited parallel to each other and pre-impregnated so as to facilitate handling of the web. Such composites are marketed by North Thin Ply Technology, for example, or by Hexcel.

Thus, it is known from FR 2 937 583 to produce composite material parts based unidirectional layers pre-impregnated composite filament.

To form a structure, or a preform, several layers are stacked one above the other, in a different orientation, to form the preform which will be secured under a defined pressure and a defined temperature.

Because of their good mechanical characteristics and their final appearance, thin-ply prepreg composites are used in many fields, such as watchmaking, where the combination of lightness and good mechanical properties is particularly appreciated. . Such a composite material is used in particular for trim parts such as the middle part, the bezel or the bottom.

However, the current composite materials confer a sporty appearance and do not allow to obtain parts combining the lightness of composites and the aesthetic appearance of metals. In addition, such a material is fragile, especially in terms of resistance to shocks and scratches. SUMMARY OF THE INVENTION [0008] The object of the invention is in particular to overcome the various drawbacks of these known techniques.

More specifically, an object of the invention is to provide a composite material suitable for producing parts having satisfactory mechanical properties, including good resistance to shocks, scratches and scratches, while maintaining an attractive appearance.

These objectives, as well as others which will appear more clearly later, are achieved according to the invention with the aid of a composite material, comprising at least a first layer formed of at least one unidirectional sheet in synthetic filaments pre-impregnated with thermosetting resin, the at least one unidirectional sheet having a first orientation, and at least one second layer formed by a thin sheet of a metallic material.

According to other advantageous variants of the invention: the metallic material is a titanium nickel alloy; the metallic material is an at least partially amorphous metal or alloy; the unidirectional sheet made of synthetic filaments has a thickness of between 30 μm and 150 μm; the thin sheet of at least partially amorphous material has a thickness of between 40 μm and 150 μm, and more preferentially between 80 μm and 100 μm; the orientation of the synthetic filaments of the unidirectional sheet is chosen from the orientation at -90 °, -45 °, + 45 ° or 0 °; the first layer preferably comprises at least two superimposed unidirectional sheets, each having a distinct orientation, and more preferably at least three superimposed unidirectional sheets, each having a distinct orientation; the composite material comprises a plurality of first and second layers; the synthetic filaments are chosen from: carbon filaments, glass filaments, silicon carbide filaments, very high molecular weight polyethylene filaments called UHMWPE, liquid crystal polymer filaments called LCP, quartz filaments silicon carbide filaments, aramid filaments, or polyethylene terephthalate filaments known as PET; the synthetic filaments are colored; the thermosetting resin is a resin of the family of polyepoxides, of the family of acrylics, of the family of polyurethanes or else of the family of polysiloxanes; the thermosetting resin comprises photoluminescent fillers, carbon nanotube fillers or even nano-diamond fillers.

The invention also relates to a method of producing a composite material part comprising at least a first layer, and at least a second layer, the method comprising the following steps: - producing at least a first layer, with synthetic filaments, in the form of at least one unidirectional sheet pre-impregnated with thermosetting resin in a first direction of orientation; - Making at least a second layer, with a metallic material, in the form of a thin sheet; - To form a preform by assembling by stacking at least a first layer and at least a second layer; - Secure the preform through a polymerization step or crosslinking of the resin under negative pressure and in a temperature cycle, and then cool the preform.

According to other advantageous variants of the method according to the invention: the first layer comprises a plurality of pre-impregnated unidirectional layers; a plurality of first and second layers are superimposed.

The invention also relates and in particular any timepiece component for a timepiece or jewelry piece made of composite material according to the invention and obtained by the previously described method of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the invention will appear more clearly on reading the following description of a particular embodiment of the invention, given as a simple illustrative and nonlimiting example, and appended figures, among which: FIG. 1 is a sectional view of a composite material according to the invention; figs. 2a, 2b and 2c show diagrams illustrating the possible combinations for producing the composite material according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0016] The invention relates to a composite material 1 for producing composite parts. The composite material 1 according to the invention comprises at least a first layer 10 formed of at least one unidirectional sheet of synthetic filaments preimpregnated with thermosetting resin, the unidirectional sheet having a first orientation, and at least a second layer 20 formed by a thin sheet of metal material.

The thermosetting epoxy resin Araldite® GY 282 Huntsman provides the best results for the realization of unidirectional sheets. The final composite material may have, for example, an alternation of one hundred and fifty first and second layers.

According to a preferred embodiment of the invention, the metallic material used is a titanium nickel alloy. Such an alloy has the advantage of having excellent characteristics of damping and fatigue resistance. Once consolidated the resulting composite combines lightness, high strength and good shock absorption properties.

Of course other metals or alloys can be used, such as gold, titanium, copper, or aluminum.

According to another embodiment of the invention, the metal material used is an at least partially amorphous metal or alloy, such as zirconium base alloys, nickel-based, or platinum-based. Such a material has the advantage of minimizing the risks of corrosion and increasing the mechanical strength, which allows a better resistance of the composite material over time.

As can be seen in FIG. 1, the composite material 1 can be composed of a plurality of layers 10, 11 formed of at least one unidirectional sheet pre-impregnated with synthetic filaments and a plurality of layers 20, 21 formed by a thin sheet of metallic material. .

According to one embodiment of the invention, the unidirectional web pre-impregnated synthetic filaments forming the first layer 10 has a thickness between 30 pm and 150 pm, and the thin sheet of metal material has a thickness of preferably between 10 pm and 150 pm, and more preferably between 80 pm and 100 pm.

According to a preferred embodiment of the invention, the first layer may comprise at least two superimposed unidirectional layers, each having a distinct orientation, and more preferably, three superimposed unidirectional layers, each having a distinct orientation.

According to the needs of those skilled in the art, especially for resistance, the orientation of the synthetic filaments is selected from the orientation at -90 °, -45 °, + 45 ° or 0 ° for example. One can also imagine a succession of unidirectional layers with an incrementation of one degree to each layer.

The orientation of the synthetic filaments relative to each other is chosen to obtain a symmetry in the complex to obtain the desired mechanical characteristics. It is noted that the pairs of preferred orientations are -90 / 0 ° and -45 / + 45 °.

According to a first exemplary embodiment illustrated in FIG. 2a, the first layer 10 comprises three unidirectional sheets superimposed on each other, the first unidirectional sheet 100 being oriented at 0 °, the second unidirectional sheet 101 being oriented at + 45 ° and the third unidirectional sheet 102 being oriented at 90 ° . The second layer 20 may consist of at least one titanium nickel alloy sheet for example, or an amorphous or partially amorphous metal or alloy. The second layer 20 may be covered by a new layer 11 which may be identical to the first layer, the new layer 11 may also have three unidirectional layers 110, 111 and 112 with different orientations, for example 90 °, -45 ° and 0 °.

It may be interesting, for aesthetic reasons, to superpose two or more sheets of metal material to form the second layer 20 so as to better visualize this component at the final appearance of the composite part. In fact, in the preceding example, for a layer 10 of three unidirectional layers of a thickness of 30 μm for example, a thickness greater than or equal to 90 μm is desirable to be able to clearly visualize the layer of metallic material within the material. composite.

According to a second exemplary embodiment illustrated in FIG. 2b, the first layer 10 comprises two unidirectional sheets superimposed on each other, the first unidirectional sheet 100 'being oriented at 45 °, and the second unidirectional sheet being oriented at -45 °. The second layer 20 may consist of at least one titanium nickel alloy sheet for example, or an amorphous or partially amorphous metal or alloy. The second layer 20 may be covered by a new layer 11 which may be identical to the first layer 10, the new layer 11 may also have two unidirectional sheets 110 'and 111' with different orientations, for example 0 ° and 90 °. Here again, the thicknesses may vary according to the needs of the person skilled in the art and the result that one wishes to obtain. By increasing the number of unidirectional layers per layer it is obvious that the composite material obtained will be stronger but the aesthetic appearance will approach a so-called sporty aspect, which is not desired here.

According to another embodiment, the first layer 10 comprises a single unidirectional sheet 100 "superimposed directly on the second layer 20 which may consist of a titanium nickel alloy sheet for example, or a metal or an alloy amorphous or partially amorphous The second layer 20 may be covered by a new layer which may be identical to the first layer, the new layer may also have a single unidirectional layer 110 "with different orientations, for example 90 °, -45 ° and 0 °.

Of course, and according to the needs of the skilled person, the composite material 1 may comprise a plurality of first and second layers so as to achieve the desired thickness before machining it. Ideally, the composite material comprises between eight layers and five hundred layers in total, the material may comprise 70% first layer and 30% second layer.

There is a wide variety of synthetic filaments, in the context of the invention, the filaments can be chosen from among these: carbon filaments, glass filaments, silicon carbide filaments, filaments made of very high molecular weight polyethylene (UHMWPE) such as Dyneema®, Vectran® filaments, quartz filaments such as Quartzel®, aramid filaments, silicon carbide filaments such as Nicalon®, or filaments polyethylene terephthalate (PET).

The filaments can also be of natural origin such as cellulosic filaments or silk filaments.

According to the needs of those skilled in the art, and in particular for obtaining particular properties, the first layer 10 may be composed of layers of different materials or layers with filaments of different materials. For example, carbon filaments and ultra-high density polyethylene filaments could each be used in a separate web, or in a single web.

These filaments, such as Vectran®, PET or glass filaments, can receive a color in the mass during their manufacture so as to obtain a particular aesthetic appearance, we can for example imagine colored filaments for contrasting with the layer of metallic material and thus better bring out the metallic material. One can also imagine an alternation of the color of the filaments within the same layer of filaments.

In order to secure the filaments and the layers together, a resin or matrix of thermosetting type is chosen according to the desired properties. This resin may be an epoxy resin, an acrylic resin, a polyurethane resin or a polysiloxane resin. According to a preferred variant of the invention, the unidirectional sheets are pre-impregnated by applying the resin to the filaments before superposing the layers on one another.

In order to promote the adhesion of the metal material layers to the unidirectional layers of synthetic filaments, it is necessary to perform a pretreatment of the second layer 20 of metallic material by the following treatment valid for steels, alloys of aluminum and titanium. Such a treatment makes it possible to remove the greases and the surface layer of oxides and thus optimally prepare the sheet of the second layer 20 for bonding with the unidirectional layer.

The metal sheet is prepared for bonding by a succession of bath treatment with different solvents and then rinsed under demineralized water and dried in a vacuum furnace. A functionalized silane primer is then immediately applied on both sides by coating.

More specifically, the sheet undergoes a preliminary cleaning with a solvent such as acetone, an aqueous phase degreasing in an ultrasonic tank with a leaching, a pressure rinse with deionized water before being submerged. Then, the sheet undergoes an acid attack in a bath. The sheet is then rinsed with demineralised water and immersed. Finally, the sheet is drained by means of blowing and then dried in an oven.

It should be noted that in the case where the metal sheet is stainless steel, passivation is necessary before draining and blowing.

An additional step may be provided to apply immediately after drying, by coating, a silane primer functionalized on both sides.

According to a particularly advantageous aspect of the invention, the thin sheet of metallic material may be further micro-perforated so that the resin of unidirectional pre-impregnated sheets penetrates the thin sheet of metallic material and thus increases the toughness. and the durability of the assembly. The thin sheet of metallic material may be textured by microbeading or by calendering or chemical etching or by surface laser so that unidirectional pre-impregnated sheets adhere better to the sheet of metallic material.

The resin may comprise charges for carbon nanotubes or nano-diamond charges based on silicon carbide for example, so as to increase the tensile or flexural modules or to improve the scratch resistance. For example, an addition of 0.5% to 1.5% of nano-diamond fillers can increase the hardness of the material, which increases its resistance to scratching and friction.

The resin may also comprise colored charges and / or photoluminescent alkaline earth oxides type doped with one or more lanthanides so as to confer a particular aesthetic appearance to the composite material when the ambient brightness drops. According to this particularly advantageous variant, the material of the filaments is transparent like the glass filament and has a refractive index substantially equal to that of the resin. For example, one will ideally choose to combine the glass filament and the acrylic resin both of which have a refractive index of 1.5.

According to another variant, the phosphorescent pigments can be combined with specific fluorophores to obtain different color pairs day / night.

With these different aspects of the invention, there is a robust composite material that can have an aesthetic appearance other than sporty.

The invention also relates to a method of producing a composite material part according to the invention.

In the first step, at least a first layer is produced, with synthetic filaments, in the form of at least one unidirectional web pre-impregnated in a first direction of orientation. This first layer may comprise several unidirectional sheets of prepreged synthetic filaments, each unidirectional sheet being able to have a distinct orientation.

Then, at least one second layer, consisting of a steel alloy type 316L stainless steel for example, or a nickel-free stainless steel alloy Panacea type, or a metal alloy at least partially amorphous of the zirconium base alloy type, nickel base, or platinum base, in the form of a thin sheet.

A preform is then formed by assembling, by stacking, at least a first layer and at least a second layer.

Finally, the preform is secured by means of a polymerization step or crosslinking of the resin under pressure and according to a predetermined temperature cycle.

After cooling, the preform can be machined into several blocks of equivalent dimensions, for example. It is also possible to machine the solidified preform to the final dimensions of the part to be obtained.

According to another embodiment, the preform may be formed by means of a filament winding, so as to manufacture hollow cylindrical parts. To do this, unidirectional thin sheets of widths from 1 mm to 5 mm impregnated with resin are wrapped around a mandrel which acts as an inner mold. On the same mandrel and at the same time, thin strips of metal alloy 2 mm to 5 mm wide are wound juxtaposed to unidirectional sheets or superimposed with an angle that can vary from 120 ° to 180 °. According to the needs of those skilled in the art, a plurality of first and second layers 10, 20 which can be superimposed to obtain the desired thickness.

Note that the cutting angle of the preform can be chosen to obtain a specific pattern for the final piece.

The components are then machined in the preform obtained, and can be treated with a sol-gel type transparent coating. Advantageously, such a coating may contain a mixture of functional silane prepolymers and hydrolysable silanes, the coating is deposited on the surface and then heat treated. Of course, other types of selective coating may be used, for example, after a copper / gold PVD treatment and then a masking of the off-decoration zone, for example an electroforming made of gold makes it possible to produce a specific decoration on the finished component. 3D.

Such a method makes it possible to manufacture timepieces made of composite material according to the invention. Thus, watch cases, dials, plates, bridges, glasses, highlights, crowns, pushers, buckles, clasps or appliques intended to be assembled on the dials can be manufactured.

Such a material is particularly interesting for providing timepieces particularly lightweight, very resistant, and combining the aesthetic appearance of a metal which makes it stand out from conventional composite materials.

By way of illustrative and nonlimiting example, a movement plate can be made from a material comprising a succession of first layers 10 comprising four unidirectional sheets of carbon filaments pre-impregnated with an epoxy resin loaded with 1% nano-diamonds, and second layers 20 nickel titanium alloy, and combine the advantages of toughness, shock absorption, scratch resistance and lightness particularly sought after in the watch industry.

Such a material is also interesting for making jewelry pieces. One can for example achieve cufflinks, or bracelets from the composite material according to the invention.

Of course, the present invention is not limited to the example shown and is susceptible of various variations and modifications that will occur to those skilled in the art, while remaining within the scope of the claims.

Claims (17)

claims Composite material (1) for producing parts, comprising at least a first layer (10) formed of at least one unidirectional sheet of synthetic filaments preimpregnated with a thermosetting resin (100, 101, 102, 110, 111, 112), the unidirectional web having a first orientation, and at least a second layer (20) formed by a thin sheet of a metallic material. The composite material (1) of claim 1, wherein the metallic material is a nickel titanium alloy. The composite material (1) according to claim 1, wherein the metallic material is an at least partially amorphous metal or metal alloy. 4. composite material (1) according to one of claims 1 to 3, wherein the unidirectional web of preimpregnated synthetic filaments has a thickness between 30 pm and 150 pm. 5. composite material (1) according to one of claims 1 to 4, wherein the thin sheet of metal material has a thickness between 40 pm and 150 pm, and more preferably between 80 pm and 100 pm. 6. composite material (1) according to one of claims 1 to 5, wherein the orientation of the synthetic filaments of the unidirectional web is selected from the orientations at -90 °, -45 °, + 45 ° or 0 °. 7. composite material (1) according to one of claims 1 to 6, wherein the first layer preferably comprises at least two superimposed unidirectional layers, each having a distinct orientation, and more preferably at least three superimposed unidirectional layers, each having a separate orientation. 8. Composite material (1) according to one of claims 1 to 7, comprising a plurality of first and second layers. 9. composite material (1) according to one of claims 1 to 8, wherein the synthetic filaments are selected from: carbon filaments, glass filaments, silicon carbide filaments, polyethylene filaments of molar mass UHMWPE, liquid crystal polymer filaments called LCP, quartz filaments, silicon carbide filaments, aramid filaments, or polyethylene terephthalate filaments known as PET. The composite material (1) according to claim 9, wherein the synthetic filaments are colored. 11. composite material (1) according to any one of claims 1 to 9, wherein the thermosetting resin is a resin of the family of polyepoxides, the family of acrylics, the family of polyurethanes or the family of polysiloxanes . 12. composite material (1) according to claim 11, wherein the thermosetting resin comprises color fillers, photoluminescent charges, carbon nanotube fillers or nanodiamond charges. 13. A method of producing a composite part, comprising at least a first layer, and at least a second layer, characterized in that it comprises the following steps: - making at least a first layer, with synthetic filaments, in the form of a unidirectional web pre-impregnated in a first direction of orientation; - Make at least a second layer, with a metallic material, in the form of thin sheet; - To form a preform by assembling by stacking at least a first layer and at least a second layer; -solidariser the preform through a step of polymerization or crosslinking of the resin under negative pressure and in a temperature cycle, and then cool the preform. The method of claim 13, wherein the first layer comprises a plurality of pre-impregnated unidirectional webs. 15. The method of claim 13, wherein a plurality of first and second layers are superimposed. 16. Watch component for a timepiece made of a composite material obtained from a composite material according to claims 1 to 12. 17. Jewelery piece made of a composite material obtained from a composite material according to claims 1 to 12.