RU2219390C2 - Rivet and method of making permanent rivet joint - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: invention can be used in making permanent rivet joints at production and repair of parts made of fibrous polymeric composite materials. According to invention, rivet is provided with central hole located along axis of rivet shank. Shank of rivet is polymerized over length corresponding to thickness of pack of parts to be connected, one of which being repair cover plate. Length of non-polymerized fibers depends on formation of required diameter of snap head. Head is made on end of shank opposite to primary head. Said head is made of polymerized fibers of diameter equal of diameter of hole for rivet. Central rod made of polymeric material is polymerized in center of head. Said polymeric material features high specific breaking and shear strength. Central rod is fitted for free movement along axis of river central hole, and it is provided with groove at a distance equal to height of rivet in compressed state, designed for fixing the rivet by lock-washer. Method of making permanent rivet joint consists in fitting the rivet in holes of parts to be connected and forming snap head. Rivet is driven into hole so that primary head should be located from outer side of repair cover plate and then non-polymerized fibers are impregnated in glue composition and said composition is applied tom outer cylindrical part of rivet shank. Then central rod is tightened by hand in direction of primary head, and rivet is locked by lock-washer, thus forming snap head owing to bending of non-polymerized fibers in radial direction. After polymerization, central rod is broken at groove level. EFFECT: improved adaptability to manufacture of permanent rivet joint in process of production and repair pf parts in difficult-to-get-at places and at one-side getting to repair section. 3 cl, 1 dwg

Description

 The invention relates to aeronautical engineering, in particular to the design of an aircraft glider, and can be used in other engineering industries to obtain one-piece rivet joints in the manufacture and repair of parts made of fibrous polymer composite materials (PCM) such as carbon-boroplastics, etc.

 Known rivets and methods for producing permanent connections of parts in hard-to-reach places (or in the absence of an approach for the formation of the closing head of the rivet on the inside) to the repaired area using conventional and special [1] rivets made of various metals, alloys, and PCM rivets [2].

 All metal rivets are intended, as a rule, for joining two or more parts made of metal materials. One of the drawbacks of metal rivets is that when two or more parts made not of metals, but of polymer composite materials such as carbon-boron plastics are connected, microcracking (destruction of the binder) of the connected parts due to impact or other mechanical effects that occur during their formulation, as well as under the influence of moisture, they strongly correlate, due to the fact that carbon, being the extreme cathode element in a galvanic research in interaction with metals, creates an electrical potential, which leads to corrosion of less inert metals in direct contact with it.

 The closest to the invention in technical essence and the achieved result is an integral rivet connection of parts containing rivet made in PCM in coaxial openings of connected parts [2], the rod of which is made of a fibrous composite material with fibers of low stiffness oriented along the axis of the rivet and the shell of related to the details of the fibrous composite material, the fibers of which have a high specific shear strength and are oriented along the rivet axis . In this case, the shell has a length corresponding to the thickness of the connected parts. The rivet core on one side is made with a embedded head. The longitudinal fibers of the rod itself (at the time of setting) are not impregnated with the adhesive composition, but are tightly packed in a polyethylene shell inside the shell. The shell from the end is fixed on the mortgage head of the rivet using an adhesive composition. Obtaining a rivet joint here is achieved by inserting a rivet through the technological hole, placing embedded heads on the inside of the damaged skin, applying an adhesive composition to the outer cylindrical part of the shell. After polymerization of the adhesive composition, the repair pad through its coaxial holes is fixed at the protruding ends of the rivets. Then, polyethylene shells are removed from the rivet rods. Using a syringe, impregnate the longitudinal fibers of the rods with a viscous adhesive composition over the entire height of the rivet rod. The formation of the closing heads of the rivets is carried out in the cold state using a mandrel made of fluoroplastic [2].

 The disadvantage of the developed rivet and the method of obtaining an integral connection is that the rivet is made of two parts independent from each other, it needs to be installed through the technological hole, placing the embedded head on the inside of the damaged skin on the adhesive composition, which leads to an increase in the time for the technological operation, accurate coaxial drilling of all holes of the repair connection (plating and lining) before installing rivets is also required, and additional special new equipment. Ultimately, the use of this rivet leads to a decrease in the manufacturability of riveted joints.

 The objective of the invention is to improve the manufacturability of one-piece rivet joints in the manufacturing process of aircraft parts and their repair with combat operational damage to the airframe made of polymer composite materials such as carbon-boroplastics in remote places and with a one-sided approach to the repair site.

 The task is achieved in that the rivet (see drawing) is made as follows: the embedded head (1) and the rivet shaft (2) are made of polymerized fibrous composite material oriented along the axis of the rod to a value equal to the thickness of the connected package, then unpolymerized fibers ( 3), the length of which is determined from the conditions for the formation of the height and diameter of the locking head. The ends of the fibers are polymerized into a common bundle (4) with a diameter equal to the diameter of the rod. There is a hole in the center of the rivet rod (2) along its axis, in which a rod of polymer material (5) freely moves, one end of which is polymerized in the center of the fiber bundle (4). Before the rivet is directly inserted into the mounting hole, the unpolymerized fibers (3) are impregnated with a viscous epoxy composition. After inserting the rivet rod into the mounting hole, the central rod (5) is pulled toward the insertion head. Due to its movement, a closing head is formed due to the bending of unpolymerized fibers (3) in the radial direction. The rod is fixed in an extended position due to a groove on its body (6) and a split fixing washer (7), which ensures the required fixed position. After polymerization of the locking head, the core breaks off along the groove.

 A method of obtaining a rivet joint in the repair of aircraft parts made of polymer composite materials is as follows (see drawing). In the skin (9) of the aircraft, the damaged portion (8) is removed. The connecting parts of the casing (9) and the overlay (10) have coaxial holes (11), which are drilled immediately before setting rivets, and after installing two rivets in order to fix the casing and overlay.

 Immediately before the rivet is inserted into the hole (11), unpolymerized fibers (3) are impregnated with a viscous epoxy composition, the outer cylindrical part of the shaft (2) and the inside of the insert head (1) of the rivet are wetted with a similar epoxy composition. After the rivet is inserted into the hole on the outside of the repair section (11) (see drawing, a), the central rod is tightened with a hand (see drawing, b). The insertion head is polymerized in the cold state (see drawing, c), the rod (5) is fixed by means of a groove on its body (6) and a split fixing washer (7) (see drawing, b). After polymerization of the locking head, the rod (5) breaks off along the groove (6) (see drawing, c). The flashing and locking heads perform the functions of anchors, thereby providing high tensile strength of the rivet (to break the heads) (see drawing, d).

 A comparative analysis with the prototype of the proposed rivet shows that it is characterized by the presence of unpolymerized longitudinal fibers, the end of which is polymerized into a common bundle, a central hole along the axis of the rivet rod, and a rod freely moving along the axis, the end of which is polymerized in the center of the fiber bundle. The formation of the embedded head of the rivet due to the approach to the repair area on the one hand increases the manufacturability of obtaining a rivet connection.

 The technical result is achieved due to the manufacture of the rivet in one piece, reducing the time for its installation, due to the lack of need for applying the adhesive composition under the embedded head and holding a certain time, as well as the absence of the need for special equipment for installing the rivet and forming the closing head.

 The effectiveness of the formation of the proposed technical solution is achieved due to the manufacturability of the proposed riveted connection of parts.

LITERATURE
1. Goryunov Yu.B. Riveting work. - Military publishing house of the Ministry of Defense of the USSR. - Moscow, 1960, pp. 54-67.

 2. Copyright certificate of the USSR 1810627, 1983 (prototype).

Claims (2)

1. A rivet containing a rod of composite fiber material, with fibers having a high specific tensile and shear strength, oriented along the axis of the rivet, having a embedded head, characterized in that it has a central hole located along the axis of the rivet rod, the rivet rod is polymerized by the length corresponding to the thickness of the package of connected parts, one of which is a repair pad, the length of unpolymerized fibers is determined from the condition of forming the diameter of the locking head, on The end of the rivet rod end, which is opposite to the embedded head, has a head made of polymerised fibers with a diameter equal to the diameter of the rivet hole, in the center of the head is a central rod of polymer material with high specific tensile and shear strength, the central rod is able to freely move along the axis of the central rivet holes and has a groove at a distance equal to the height of the rivet in a compressed state, which serves to fix the rivet with a lock washer. 2. A method of obtaining a permanent rivet joints, including the placement of a rivet in the holes of the parts to be joined and the formation of a locking head, characterized in that the rivet is inserted into the hole of the parts to be joined, placing the insert head on the outside of the repair lining, impregnating unpolymerized fibers with the adhesive composition, and also applying it on the outer cylindrical part of the rivet rod, and then with the help of the hand pull the central rod in the direction of the embedded head and fix it with a lock washer oh, thereby allowing formation of the closing head by bending unpolymerized fibers in the radial direction after the polymerization central rod breaks off along the groove.