RU2769143C1 - Rivet and method for obtaining a non-detachable rivet connection of parts without a two-way access to the rivet seam - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to mechanical engineering and can be used for non-detachable connection of parts made of a composite material. Rivet comprises a rod made of a polymer composite material with fibres oriented along the axis thereof. The rod has a cylindrical head at one end, a thread along the entire length, a calibrated neck located at a distance from the cylindrical head, and a two-sided longitudinal flat extending from the calibrated neck to the end of the rod. A washer made of a hardened composite material, the outer diameter whereof is 0.5 to 5 mm greater than the size of the hole in the connected parts, is set on the head. The washer has cutouts along the outer diameter, forming lobes, elastically deformed when passing through the hole of the connected parts, and flattening outside of the hole. A sleeve made of a prepreg of a composite material is installed supported by the washer and compressed by a nut made of a hardened composite material. After heating the sleeve to the temperature of polymerisation of the prepreg, the parts of the rivet and the connected material turn into a durable monolith.

EFFECT: increase in the security of the resulting connection is provided as a result.

3 cl, 5 dwg

Description

The invention relates to mechanical engineering, and can also be used in the aircraft industry and other industries, to obtain one-piece riveting joints in the production and repair of highly loaded parts made of polymeric carbon composite materials that do not have a two-sided approach to the rivet seam.

When performing riveting work in the production and repair of aircraft structures, there are places that do not allow a two-way approach to the repair area. The invention of a rivet and a method for producing a permanent rivet connection of parts from a composite material is known (patent RU No. 2582472 pub. 27.04.2016). The rivet consists of a rod made of a polymeric composite material with fibers oriented along the axis of the rod, with a cylindrical head at one end and an uncured upper part of the rod at the other end, installed in a body made of a cured prepreg of a composite material related to the parts to be joined and consisting of cylindrical coaxial embedded head and sleeve, while the insert head is countersinked, and the lower part of the sleeve is made into a cone under the connected parts by the thickness of the ring. The outer diameter of the body sleeve is equal to the diameter of the cylindrical head of the rivet, and the inner diameter is equal to the diameter of the rod, the outer diameter of the ring is equal to the outer diameter of the sleeve, while only the uncured part of the rod has a fluoroplastic shell.

The disadvantage of such a rivet is low reliability and strength, which is due to insufficient screed of the parts to be joined into the package, since the ring is made of uncured prepreg, and the rod and sleeve are not threaded.

The disadvantage of this method is the low manufacturability and strength of the rivet seam, due to the fact that the prepreg ring at the time of installation is in an uncured (non-polymerized) state, which leads to insufficient screed of the parts to be joined into the package.

A rivet and a method for producing a permanent rivet joint in carbon composite structures are known (patent RU No. 2691725 pub. 06/17/2019), taken as a prototype. A rivet consisting of a rod made of a polymer composite material with fibers oriented along its axis, with a cylindrical head at one end, installed in a cone consisting of a cylindrically coaxial embedded head and a bushing. In this case, the lower part of the bushing is made into a cone, a ring is installed between the cylindrical head of the rivet and the lower part of the body bushing, the length of the body bushing is equal to the thickness of the connected parts, and the cone of the lower part of the body bushing is under the connected parts by the thickness of the ring, the outer diameter of the body bushing is equal to the diameter of the cylindrical rivet head, and the inner diameter of the rod, the outer diameter of the ring is equal to the outer diameter of the sleeve. The rivet rod has a thread in its entire length and a calibrated neck located from the cylindrical head of the rivet at a distance equal to the thickness of the parts to be connected; the cone has a hexagonal shape, while the ring is made of titanium alloy. A method for producing a permanent rivet joint, which consists in placing a rivet in the holes of the parts to be joined that do not have a two-sided approach to the purchase seam. After placing the rivet in the coaxial holes of the parts to be joined, the embedded head of the rivet body is rotated until a calibrated neck of the rod appears at the level of its outer surface, and the protruding part of the rod is removed along the calibrated neck.

The disadvantages of this invention is the use of parts made of a titanium alloy, which creates an increased voltage at an operational temperature difference of more than 100°C. the difference between the coefficients of thermal linear expansion of titanium and the composite material is about 10, the rivet and the material to be joined will be subjected to cyclic loading, which may adversely affect the rivet joint. In addition, it is rather difficult to obtain a cone from a titanium cylinder using a cone part made of a composite material.

This invention solves the problem of creating a rivet structure entirely from carbon-composite material, increased reliability and a simple method for assembling it with a one-sided approach to the riveting seam.

This technical result is achieved in that the rivet contains a rod made of a polymer composite material with fibers oriented along its axis, a cylindrical head at one end. The rod has a thread in its entire length and a calibrated neck located from the cylindrical head of the rivet at a distance equal to the thicknesses of the parts to be connected, the washer and the height of the nut, from the calibrated neck to the end of the rod a two-sided longitudinal flat is made. A washer made of a cured polymer composite material is installed on the cylindrical head, its diameter is larger than the size of the coaxial holes of the parts to be connected by 0.5…5 mm, and the outer diameter of the washer is made in the form of petals that allow it to pass through the holes of the parts to be connected. The washer is fitted with a composite prepreg sleeve, which is compressed by a cured composite nut during assembly.

The rivet works as follows: it is pre-assembled into the holes of the parts to be joined, while the petals are slightly elastically deformed, and after passing through the holes, the washer becomes flat due to springback, which will lock the rivet when moving in the opposite direction. Then the nut is screwed in, which compresses the bushing from the prepreg of the composite material, then the end of the rod is removed along the calibrated neck. To cure the prepreg of the composite material, the sleeves are heated to the polymerization temperature of the composite material used, for example, with a radiation lamp.

Thus, the parts to be joined, the rivet shaft, the washer, the nut and the sleeve, after polymerization, turn into a single whole, which is necessary for the reliable operation of the product.

Fig. 1 - design of the rivet, fig. 2 - washer, fig. 3 - a device for installing a rivet in the holes of the parts to be joined, fig. 4 - installation of a rivet in the holes of the parts to be joined, fig. 5 - final assembly of the rivet.

The rivet (Fig. 1) contains a rod 1 with a cylindrical head 2, on which a washer 3 is located, the sleeve 4 made of a composite prepreg rests on the latter, which is compressed by a nut 5 made of a hardened composite material.

The rod 1 (Fig. 1) of the rivet is made of a polymer composite material with fibers oriented along its axis, at one end with a cylindrical head 2 and has a thread for the entire length of the rod. The rod has a two-sided flat 6 and a calibrated neck 7, which is located from the cylindrical head at a distance equal to the thickness of the parts to be joined 10, the washer 3 and the height of the nut 5 (Fig. 3, Fig. 5). The washer 3 (Fig. 2) is made of a hardened composite material with an outer diameter 8 larger by 0.5 ... 5 mm than the size of the holes 9 of the connected parts 10 (Fig. 3, Fig. 5), cutouts 11 are made on the outer diameter of the washer 3, which allow petals 12 (Fig. 3) elastically deform when passing through the holes 9 of the connected parts 10, and after passing the hole, the washer 3 becomes flat due to springback and stops the return of the rivet (Fig. 3).

For example, to install a rivet (Fig. 3) in the holes 9 of the connected parts 10, in order to more easily overcome the resistance of the elastic deformation of the petals 12, it is enough to use a simple device. The metal pressure 14 at the point of contact with the washer 3 has a diameter equal to or less than the inner diameter 15 of the petals 12 (Fig. 2), (Fig. 3). After setting the pressure 14 on the rod 1, the nut 5 is wound, such an assembly is inserted into the holes 9 and, overcoming the resistance of the elastic deformation of the petals 12 of the washer 3, passes through the holes 9 (Fig. 3). The washer 3 becomes flat and excludes the return of the rod 1 from the holes 9. To hold the rod 1 with the washer 3 in the holes 9, a stopper 16 is used, which holds the rod 1 by the calibrated neck 7 (Fig. 4). Screw the nut 5, remove the pressure 14, install the sleeve 4 and the nut 5, remove the stopper 16, carry out the final assembly of the rivet. After tightening the nut 5, the protruding end 13 of the rod 1 is removed along the calibrated neck 7. The rivet is heated, for example, with a radiation lamp, to the polymerization temperature of the prepreg composite material of the sleeve 4 (Fig. 5).

Thus, the parts to be joined, the rivet shaft, the washer, the nut and the sleeve are transformed into a single whole, which is necessary for the reliable operation of the product.

Claims (3)

1. A rivet containing a rod made of a polymer composite material with fibers oriented along its axis, made with a cylindrical head at one end, a thread along the entire length, a calibrated neck located at a distance from the cylindrical head, and a double-sided longitudinal flat from the calibrated neck to the end a rod, and a bushing made of a prepreg of a composite material, characterized in that it is equipped with a washer made of a cured composite material mounted on a cylindrical head, made with an outer diameter exceeding the size of the hole in the parts to be joined by 0.5-5 mm, and cutouts along the outer diameter, forming petals with the possibility of elastic deformation, and a nut made of a hardened composite material, while the calibrated neck is located at a distance from the cylindrical head of the rod, equal to the thickness of the parts to be connected, the thickness of the washer and the height of the nut, the bushing is mounted resting on the washer, and the nut is screwed onto the rod with bushing compression capability. 2. A method for producing a permanent rivet connection of parts that do not have a two-sided approach to the rivet joint, characterized in that the rivet according to claim 1 is placed in the hole of the parts to be joined made of composite material to ensure elastic deformation of the washer petals when it passes through the hole of the parts to be joined, by means of a nut the sleeve is compressed from the prepreg of the composite material, and after tightening the nut, the protruding part of the rod is removed along the calibrated neck and heating is carried out to ensure the polymerization of the prepreg of the composite material of the sleeve. 3. The method according to p. 2, characterized in that the heating is carried out with a radiation lamp.

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