Aircraft rod comprising glass fibers embedded in an organic matrix

Abstract

The invention relates to a rod (20) for a pneumatic tire (10), comprising: at least one strand of glass fiber embedded in an organic matrix, wherein the diameter D of the rod (20) is from 14 to 25 mm and wherein the breaking strength (Fm) of the rod (20) is greater than or equal to 150 kN. Figure for abbreviation: Fig. 2

Description

Title of the invention: Aircraft rod comprising glass fibers embedded in an organic matrix

[0001] The invention relates to tire bead wires. It is applicable to all types of tires for all types of vehicles.

[0002] A tire conventionally comprises two circumferential beads designed to allow the tire to be attached to the rim. Each bead includes an annular reinforcing bead.

[0003] Prior art is known for an aircraft tire comprising a rod with a core and six layers of steel wire wound around the core. The core is made of a steel monofilament. The monofilament is bent upon itself and its two ends welded to form a substantially circular ring.

[0004] We also know from the prior art and in particular from document EP133110 an aircraft tire comprising a rod including a lightweight metal core and an outer layer of steel wires wound around the core.

[0005] We also know from the prior art and in particular from document WO2013182599 an aircraft tire comprising a bead comprising a core comprising at least one strand of a multifilament textile fiber embedded in an organic matrix and an outer layer of steel wires wound around the core.

[0006] The disadvantage of such rods is that, on the one hand, the manufacturing process is complex due to the assembly of the layers of wires around the core, and on the other hand, the architecture of such rods implies the presence of capillaries which can deform the rod during compression phenomena, impacting the performance of the tire.

[0007] The invention aims to find a rod to remedy these drawbacks.

[0008] For this purpose the invention relates to a rod for pneumatics comprising at least one strand of a glass fiber embedded in an organic matrix, in which the diameter D of the rod goes from 14 to 25 mm and in which the breaking force of the rod is greater than or equal to 150 kN in accordance with ISO 6892 of 1984.

[0009] The inventors of the invention discovered that glass fibers embedded in an organic matrix have high breaking strength while maintaining a controlled diameter. This eliminates a step of assembling the layers of fibers around the core and reduces the need for fining inside the rod since there are no capillaries, thus preserving the rod's shape and ensuring the compression ratio. In addition to these advantages, the mass of the rod is considerably reduced compared to prior art rods.

[0010] The glass fiber allows the reinforcement of the organic matrix.

[0011] By organic matrix, we mean any matrix comprising, by weight, more than 50%, preferably more than 75%, and more preferably more than 90%, of organic matter. The organic matrix may contain minerals and / or metals originating from its manufacturing process, as well as mineral and / or metallic additives intentionally added.Thus, an organic matrix can, for example, be a thermosetting polymeric matrix, for example based on unsaturated polyester, polyepoxide, phenolic derivative or aminoplast, or a thermostable matrix, for example based on cyanate, polybismaleimide, polyimide, polyamidoimide, or a thermoplastic matrix, for example based on polypropylene, polyamide, saturated polyester, polyoxymethylene, polysulfone and polyethersulfone, polyetherketone and polyetheretherketone, polyphenylene sulfide, polyetherimide, or a thermoplastic or crosslinked elastomer, for example based on polyurethane, silicone or rubber, or an organic matrix resulting from a mixture of these matrices.

[0012] Preferably, the organic matrix is ​​thermoset, preferably crosslinked. For example, it is a resin crosslinkable by ionizing radiation, such as ultraviolet-visible radiation, an accelerated electron beam, or X-rays. Alternatively, a composition comprising a resin crosslinkable by a peroxide may be chosen, with subsequent crosslinking then being carried out, when required, by means of a heat input, for example, by microwaves. Preferably, a composition of the type curable by ionizing radiation is used, the final polymerization being easily initiated and controlled by means of an ionizing treatment, for example, of the UV or UV-visible type. As a crosslinkable resin, a polyester resin (i.e., based on unsaturated polyester) or a vinyl ester resin is most preferably used. Even more preferably, a vinyl ester resin is used.

[0013] In one embodiment, the rod comprises a single strand, and preferably is made of a single strand.

[0014] In one embodiment, the rod forms a monolithic torus. By monolithic, it is understood that the torus exhibits no discontinuities in material or joints at the macroscopic scale. Because the torus is monolithic, the core is less fragile than the core of the prior art rod, which exhibits a weakness at the weld point of its ends. Preferably, the elementary filaments are distributed homogeneously throughout the volume of the torus.

[0015] In another variant, the rod forms a winding of the strand in several turns.

[0016] In another embodiment, the rod comprises several distinct strands. The material of the curtain rod, due to the presence of the organic matrix, presents a high capacity for elastic deformation which is amplified by the plurality of strands. Indeed, by increasing the number of strands and for a predetermined rod dimension, the cross-section of each strand is reduced, therefore the stiffness of the cross-section of each strand is reduced, and the critical bending radius of the rod is decreased.

[0017] The breaking strength measurements of the rod (maximum load in N) can be carried out by any type of commonly used method. For example, a method conforming to ISO 6892:1984 can be used on a straight section of the rod, or a method conforming to the rod tensile test described below.

[0018] The breaking strength measurements of the rod (maximum load in N) are carried out at room temperature, preferably using a circumferential tensile test, known as a rod tensile test, on a tensile testing machine comprising radially moving sectors. During this test, performed under quasi-static conditions, the rod or web to be tested is positioned around the sectors, in this case 12 in number. The simultaneous and progressive movement of the sectors exerts a radial force of increasing intensity on the rod or web. The movements of the sectors are monitored by force sensors that measure the forces exerted on the rod or web.

[0019] The force applied to the rod or web is measured using three force sensors positioned on the moving sectors. The circumferential force applied to the rod or web is calculated from the radial force measured by the force sensors by applying a geometric factor corresponding to the angle of the 12 sectors, i.e., 60°, according to the formula: Circumferential force applied = 1.932 x Radial stress force.

[0020] The breaking force is determined by the maximum force recorded by each of the force sensors after a section of the rod or web breaks. The acquisition frequency is 100 Hz. The breaking force value used is the average of the three values ​​measured by the three sensors.

[0021] By diameter of the rod, we mean the diameter of the smallest circle in which the rod is circumscribed.

[0022] Any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​going from more than a to less than b (i.e. excluding bounds a and b) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (i.e. including the strict bounds a and b).

[0023] Within the scope of the invention, the carbon products mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass.

[0024] Within the framework of the invention, it may also be envisaged that the carbon products mentioned in the description include isotopes of certain chemical elements.

[0025] Advantageously, the breaking force of the rod is less than or equal to 450 kN.

[0026] Preferably, the breaking strength of the rod is greater than or equal to 200 kN and more preferably greater than or equal to 300 kN.

[0027] Preferably, the maximum accessible area of ​​the rod section is less than or equal to 200 mm2.

[0028] By minimum accessible area, we mean the area measured on a section of rod, it being understood that the area is determined by considering the diameter circumscribed around the rod and that the measurement is carried out on 10 sections of rods and the average accessible area is determined.

[0029] Preferably, the maximum accessible surface area of ​​the rod section is greater than or equal to 100 mm2.

[0030] Preferably, the diameter of the rod D is from 14 to 22 mm.

[0031] Advantageously, the fiberglass count ranges from 100 to 1300 tex and preferably from 500 to 1200 tex.

[0032] The count (or linear density) of each glass fiber is determined according to the ASTM DI423 standard. The count is given in tex (weight in grams of 1000 m of product - reminder: 0.111 tex equals 1 denier).

[0033] Preferably, the measured extension modulus of the rod is preferably greater than 15 GPa, more preferably greater than 30 GPa, in particular is from 40 to 80 GPa.

[0034] The deformation measurement of the rod is carried out by following the displacement of a sector using a wire potentiometer.

[0035] The lengthening of the development of the AL rod in mm is calculated by the formula: Rod lengthening = sector displacement x 2 x Pi.

[0036] Before proceeding with the deformation measurement, a pre-accommodation of the sample is performed. This pre-accommodation is set at 100 N. This pre-accommodation allows the initial development of the object to be fixed for the deformation measurement.

[0037] The deformation is given between the ratio of the elongation of the development of the rod AL in mm to its initial development L0 in mm.

[0038] To measure a deformation conforming to this method, it is important not to use a rubber ring between the sectors and the object being measured. Therefore, to measure the breaking strength and elongation, it may be necessary to perform two separate measurements. One measurement with the rubber ring to evaluate The force is measured, and a measurement without the ring is taken to assess the deformation. In this case, the deformation will be consistent until failure. It is important to note that premature failure may occur due to a lower stress distribution; in this case, this should not be considered when measuring failure.

[0039] Another method for measuring the deformation of the rod can be carried out using a laser extensometer. This can make it possible to measure the deformation up to a conformal break.

[0040] The nominal secant modulus at X% deformation is defined as the modulus of the measured object at a deformation value of X / 100. The nominal stress F / SO is determined, where F is the measured force and SO is the initial cross-section of the object, for a deformation of X / 100, and the elastic secant modulus at X% deformation is calculated by dividing this stress value by the deformation value: Modulus in MPa = Force in N x L0 in mm / (S0 in mm² x AL in mm). In the context of the invention, this modulus measurement is calculated for a deformation of 0.5%.

[0041] The measurement can be taken directly from the beads before the tire is manufactured. It can also be taken from beads extracted from the tire. In this case, it is necessary to extract the bead without damaging it at this stage; a person skilled in the art will know how to perform this extraction without damage. For measurements requiring knowledge of the elongation (deformation and / or modulus), the extraction method must not leave any rubber on the surface of the bead.

[0042] Advantageously, the section of the rod is round, square, hexagonal or triangular in shape.

[0043] Advantageously, the section of the rod is arbitrary.

[0044] More preferably, the section of the rod is round in shape.

[0045] The invention also relates to a method for manufacturing the rod as defined above comprising the following steps: - at least one glass fiber is supplied; - the glass fiber(s) are impregnated with a vinylester resin; - the resin is at least partially crosslinked under UV and IR radiation and - a heating step is carried out to ensure complete crosslinking of the resin.

[0046] Preferably, the heating step is carried out between 5 and 40 minutes at a temperature ranging from 180 to 200°C.

[0047] Preferably, a subsequent step is carried out of gluing the rod with an adhesive composition.

[0048] In another advantageous embodiment, such an adhesive composition is for example of the RFL type (acronym for Resorcinol-Formaldehyde-Latex) but also adhesive compositions such as those described in WO2015118041.

[0049] Finally, the invention also relates to a pneumatic tire comprising at least one rod as defined above.

[0050] Preferably, the tire is for aircraft. Given the large number of tires carried on an aircraft, which can reach more than twenty units, the reduction in mass of each tire allows a relatively significant reduction in the total mass of the aircraft.

[0051] Alternatively, the tire is for a land vehicle. By land vehicle, we mean any vehicle except aircraft.

[0052] The invention will be better understood upon reading the following examples, given solely by way of non-limiting examples and made with reference to the drawings in which: - [Fig. 1] is a cross-sectional view perpendicular to the circumferential direction of a tire (10) according to the invention; and - [Fig.2] is a cross-sectional view perpendicular to the axis of the rod (assumed to be straight and at rest) of the rod (20) according to the invention.

[0053] Figure 1 shows a tire according to the invention, designated by general reference numeral 10. In this case, the tire 10 is intended to be mounted on an aircraft and has dimensions 46x17 R20. Alternatively, the tire 10 is intended to be mounted on a land vehicle, for example, a heavy goods vehicle.

[0054] The tire 10 comprises a crown 12 reinforced by a crown reinforcement 14, two sidewalls 16, and two bead 18, each bead 18 being reinforced with an annular bead 20. The crown 14 is surmounted by a tread not shown in this schematic figure. A carcass reinforcement 22 is wound around the two bead 20 in each bead 18 and includes a inversion 24 facing outwards from the tire 20, which is shown here mounted on a rim 26. The carcass reinforcement 22 consists of at least one plies reinforced by cables. The reinforcement 22 is of the radial type. Alternatively, the reinforcement 22 consists of at least two plies reinforced by cables and is of the bias type.

[0055] Each rod 20 has a generally toroidal shape and a substantially circular cross-section. Alternatively, the rod 20 has a polygonal cross-section, for example, square, rectangular or hexagonal, or even an elliptical or oblong cross-section.

[0056] A rod 20 according to the invention is shown in [Fig.2].

[0057] The rod 20 comprises glass fibers embedded in an organic vinyl ester matrix, the diameter of the rod is 14.58 mm and its breaking strength is 200 kN. The glass fiber count is 600 tex.

[0058] The measured extension modulus of the rod is 70 GPa, which is greater than 15 GPa, greater than 30 GPa, and therefore between 40 and 80 GPa.

[0059] The surface area of ​​the rod is 167 mm2.

[0060] The thermosetting resin is of the vinylester type. Without this definition being limiting, the vinylester resin is preferably of the epoxy vinylester type. A vinylester resin, in particular of the epoxy type, is more preferably used, which is at least partly based on (i.e., grafted onto a structure of the type) novolac (also called phenoplast) and / or bisphenolic, or preferably a vinylester resin based on novolac, bisphenolic, or novolac and bisphenolic, as described for example in applications EP 1 074 369 and EP 1 174 250. A novolac and bisphenolic type epoxyvinylester resin has shown excellent results; by way of example, the vinyl ester resins "ATLAC 590" or "ATLAC E-Nova FW 2045" from the company AOC (both diluted with styrene) may be cited. Such epoxyvinylester resins are available from other manufacturers such as Reichhold, Cray Valley, UCB.

[0061] The core 30 is manufactured for example by impregnating the fiber as described in US document 3,730,678 or by injecting the organic matrix into a mold where the fiber has been previously placed or as described in EPI document 167080.

[0062] The rod is manufactured using the following steps: - at least one fiberglass is supplied; - the glass fiber(s) are impregnated with a vinylester resin; - the resin is at least partially crosslinked under UV and IR radiation and - a heating step is carried out to ensure complete crosslinking of the resin.

[0063] COMPARATIVE MEASUREMENTS

[0064] The rod 20 according to the invention was compared with the rod 100 of the prior art. The tire 10 according to the invention was also compared with a tire of the prior art comprising two rods 100 of the prior art.

[0065] Table 1 below summarizes the characteristics resulting from the measurements carried out.

[0066] [Tables 1] Rod 100 Rod 20 Breaking strength (Fm) in kN 200 200 Core / material; Cl / material Fl; C2 / material F2 CVR; Cl / 23; C2 / 28 CVR,-,- Metal wire diameter (mm) Fl / F2 1.30 / 1.30 - Fiberglass (Tex) content 600 600 Fiberglass core diameter (mm) 9 14.58 Rod diameter D (mm) 14.28 14.58 Rod surface area (mm²) 213 167 Tensile modulus (GPa) 190 70 Process: ease of processing Time saving (min) 0 9 Pneumatic Rod mass saving (%) 100 -53% Tire mass saving (%) 100 -3%

[0067] The bead 20 according to the invention makes it possible to considerably reduce the mass of the bead compared to the prior art and consequently the mass of the tire. Furthermore, it eliminates a step of assembling the layers of yarn around the core, which saves time, and finally, it limits creep inside the bead since there are no capillaries, thus preserving the bead structure and guaranteeing the compression ratio.

[0068] The invention is not limited to the embodiments described above.

[0069] Indeed, the bead according to the invention can be mounted on a tire other than an aircraft tire. For example, the bead can be intended for a tire for industrial vehicles chosen from among vans, heavy vehicles such as "Heavy Goods Vehicles" - i.e., subways, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles -, agricultural or civil engineering equipment, other transport or handling vehicles.

Claims

Demands

1. Rod (20) for pneumatic (10), characterized in that it comprises: at least one strand of a glass fiber embedded in an organic matrix, in which the diameter D of the rod (20) is from 14 to 25 mm and in which the breaking force (Fm) of the rod (20) is greater than or equal to 150 kN in accordance with ISO 6892 of 1984.

2. Rod (20) according to the preceding claim, wherein the breaking force (Fm) of the rod (20) is less than or equal to 450 kN.

3. Rod (20) according to any one of the preceding claims, wherein the breaking force (Fm) of the rod (20) is greater than or equal to 200 kN and more preferably greater than or equal to 300 kN.

4. Rod (20) according to any one of the preceding claims, wherein the maximum accessible area of ​​the cross-section of the rod (20) is less than or equal to 200 mm2.

5. Rod (20) according to any one of the preceding claims, wherein the organic matrix is ​​of the thermoset type, preferably cross-linked and more preferably of the vinylester type.

6. Rod (20) according to any one of the preceding claims, wherein the diameter D of the rod is from 14 to 22 mm.

7. Rod (20) according to any one of the preceding claims, wherein the fiberglass count is from 100 to 1300 tex and preferably from 500 to 1200 tex.

8. Rod (20) according to any one of the preceding claims, wherein the measured extension modulus of the rod (20) is preferably greater than 15 GPa, more preferably greater than 30 GPa, in particular is from 40 to 80 GPa.

9. Rod (20) according to any one of the preceding claims, wherein the section of the rod (20) is round, square, hexagonal or triangular in shape.

10. A method for manufacturing the rod (20) according to any one of the preceding claims, wherein: - at least one glass fiber is provided; - the glass fiber(s) is / are impregnated with a vinyl ester resin; - the resin is at least partially crosslinked under UV and IR radiation and - a heating step is carried out to ensure complete crosslinking of the resin.

11. Method of manufacturing the rod (20) according to the preceding claim, wherein a subsequent step of gluing the rod (20) with an adhesive composition is carried out.

12. Pneumatic (10), characterized in that it comprises at least one rod (20) according to any one of claims 1 to 9.

13. Pneumatic (10) according to the preceding claim, for aircraft.

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