Composite material protective bushing and mounting method thereof

Abstract

The invention discloses a composite material protection bushing and an installation method thereof, when the composite material protection bushing is installed on a special extrusion core rod, the composite material protection bushing can be tightly attached to the core rod, and the composite material protection bushing and the core rod can be placed in a composite material installation hole together in a clearance mode. And when the protective bushing and the core rod are arranged in the composite material mounting hole, the tapered core rod is pulled by using a mounting tool to enable the protective bushing to generate radial expansion, and meanwhile, the inner wall of the composite material mounting hole is extruded, so that the protective bushing is plastically deformed and is tightly combined with the composite material mounting hole. By providing high interference amount, the protective bush generates plastic deformation, the protective bush has a sealing effect and certain push-torsion resistance while being tightly combined with a composite material, and a composite material hole is protected from being damaged due to the influence of a bolt.

Description

Technical Field

[0001] The invention belongs to the technical field of protective bushings, and in particular relates to a protective bushing for composite materials. Background Art

[0002] Due to the excellent physical and mechanical properties of composite materials, their use in aerospace structures has increased year by year. Especially in recent years, with the rapid development of the aviation industry, composite materials have gradually replaced metal materials in aircraft structural design and become the main aircraft structural material.

[0003] There are three main types of connection for composite structures: adhesive connection, mechanical connection and hybrid connection. Currently, mechanical connection is the most widely used connection for aircraft composite materials. During mechanical connection, interference fit bolts will cause cracking in the composite materials, resulting in the structural connection being the weakest link in the composite laminate structure. Therefore, solving the initiation of damage to composite structures and improving the quality of interference connections of composite structures have become key technical issues currently faced in aircraft assembly. Summary of the invention

[0004] The purpose of the present invention is to provide a high interference amount to cause the protective bushing to produce plastic deformation, tightly combine with the composite material, have a sealing effect and a certain anti-twist and twist ability, and protect the composite material hole from being damaged by the bolt.

[0005] The technical solution of the present invention is as follows: A composite material protective bushing, consisting of a cylindrical part and a flange part, wherein the flange part extends radially outward from the end of the cylindrical part, and the inner angle of the flange part is 100°≤α≤180°. The composite material protective bushing is an integrally formed structure, and the composite material protective bushing is made of titanium alloy or stainless steel into a cylindrical metal part. The composite material protective bushing has an inner angle α of 100° for the flange part, an inner angle α of 130° for the flange part (counterbore hole type), or an inner angle α of 180° for the flange part (T-type), as well as flangings at other angles, which can be suitable for countersunk holes or straight holes, and has a certain elasticity as a whole.

[0006] Also provided is a method for installing the composite material protective bushing.

[0007] Step 1: The composite material protective bushing is pretreated, and a solid dry film lubricant is applied to the inner diameter hole wall of the composite material protective bushing, and a special coating is added to the outside of the composite material protective bushing;

[0008] Step 2: placing the pretreated composite material protective bushing into the composite material substrate mounting hole;

[0009] Step 3: placing the composite protective sleeve together with the composite substrate on top of the top sleeve;

[0010] Step 4: Place a matching tapered extrusion mandrel on top of the composite material protective bushing, and the tapered extrusion mandrel fits tightly with the hollow part of the composite material protective bushing;

[0011] Step 5: Start the pulling gun to pull the tapered extrusion core rod out from the bottom of the top sleeve, so that the composite material protection bushing expands radially and squeezes the inner wall of the composite material installation hole, so that the composite material protection bushing is plastically deformed and tightly combined with the composite material installation hole;

[0012] Step 6: Remove the top cover and the installation is complete

[0013] The inner diameter hole wall of the bushing is coated with a solid dry film lubricant to reduce the tension required during the extrusion installation of the cold extruded joint. The high interference is provided by the wall thickness of the protective bushing and the main diameter of the core rod, so that the protective bushing is combined with the composite material after elastic-plastic deformation, and the composite material hole is guaranteed not to be damaged by the bolt.

[0014] When the composite material protective bushing is installed on a special extrusion mandrel, it can fit tightly with the mandrel and can be placed in the composite material mounting hole with a gap together with the mandrel. When the protective bushing and the mandrel are placed in the composite material mounting hole, the installation tool is used to pull the tapered mandrel to cause the protective bushing to expand radially, and at the same time squeeze the inner wall of the composite material mounting hole, so that the protective bushing is plastically deformed and tightly combined with the composite material mounting hole. Special coatings or special treatments can be added to the outside of the protective bushing to give the bushing some special properties, such as adding adhesives to improve its sealing effect.

[0015] Beneficial effects of the present invention:

[0016] 1) Compared with the traditional cold shrink installation bushing, the cold extrusion protection bushing is more convenient to install; and the gap installation can effectively prevent damage to the composite material installation hole during installation;

[0017] 2) Compared with traditional bonded bushings, cold extruded protective bushings do not require adhesives and sealants for installation, have low labor costs, high reliability, good process control effects, and do not require other compounds or additional repair bonding or sealing. After installation, the bushing has better coaxiality;

[0018] 3) Good installation quality, applicable to most composite materials;

[0019] 4) It can improve the damage tolerance of composite materials to a limited extent and increase the fatigue strength of composite materials;

[0020] 5) It can enhance the service life of composite material holes, and the installation and removal of fasteners in the installation holes will not cause damage to the holes;

[0021] 6) It can make the composite material have good electrical conductivity between the connecting structure and improve the lightning resistance of the composite material;

[0022] 7) Can protect the geometry of the mounting hole under compressive loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings herein are incorporated into and constitute a part of the specification, showing embodiments consistent with the present invention, and together with the specification, are used to explain the principles of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0024] Figure 1 A schematic diagram of the structure of the composite material protective bushing provided by the present invention, wherein the inner side angle α of the flange portion is 100°;

[0025] Figure 2 A schematic diagram of the structure of the composite material protective bushing provided by the present invention, in which the inner side angle α of the flange portion is 130°;

[0026] Figure 3 A schematic diagram of the structure of the composite material protective bushing provided by the present invention, in which the inner side angle α of the flange portion is 180°;

[0027] Figure 4 This is a structural schematic diagram of a composite material protective bushing placed in a composite material substrate mounting hole;

[0028] Figure 5 This is a schematic diagram of the installation structure of the composite material protection bushing;

[0029] Figure 6 This is a schematic diagram of the composite material protective bushing provided by the present invention after installation.

[0030] In the accompanying drawings: 1-composite material protective sleeve, 11-cylindrical part, 12-flange part

[0031] 2-composite material substrate, 3-gap DETAILED DESCRIPTION

[0032] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and fully convey the concept of the example embodiments to those skilled in the art.

[0033] See also Figure 1-3 , FIG. 1 shows a schematic diagram of a partial composite material protective bushing structure provided by the present invention, Figure 1-3They are schematic diagrams of the composite material protective bushing having a flange portion with an inner angle α of 100°, a flange portion with an inner angle α of 130° (counter sink hole type) or a flange portion with an inner angle α of 180° (T type).

[0034] like Figure 6 The present invention shows a method for installing a composite material protective bushing, step 1: pre-treating the composite material protective bushing, coating the inner diameter hole wall of the composite material protective bushing with a solid dry film lubricant, and adding an adhesive to the outside of the composite material protective bushing to improve its sealing effect;

[0035] Step 2: placing the pretreated composite material protective bushing into the composite material substrate mounting hole;

[0036] Step 3: placing the composite protective sleeve together with the composite substrate on top of the top sleeve;

[0037] Step 4: Place a matching tapered extrusion mandrel on top of the composite material protective bushing, and the tapered extrusion mandrel fits tightly with the hollow part of the composite material protective bushing;

[0038] Step 5: Start the pulling gun to pull the tapered extrusion core rod out from the bottom of the top sleeve, so that the composite material protection bushing expands radially and squeezes the inner wall of the composite material installation hole, so that the composite material protection bushing is plastically deformed and tightly combined with the composite material installation hole;

[0039] Step 6: Remove the top cover and the installation is complete.

[0040] Figure 4-5 This is a comparison diagram before and after the installation of the composite material protection bushing. The composite material protection bushing 1 is placed in the installation hole of the composite material substrate 2 with a certain gap 3. After the above installation, it is completely and tightly combined with the composite material installation hole.

[0041] Any modification or equivalent substitution made to the technical solution of the present invention, as long as it does not depart from the spirit and scope of the technical solution of the present invention, is included in the scope of the claims of the present invention.

Claims

1. A composite material protective bushing, characterized in that: It comprises a cylindrical part and a flange part, wherein the cylindrical part is a hollow structure, the flange part radially extends outward from the end of the cylindrical part, and the inner side angle of the flange part is 100°≤α≤180°.

2. The composite material protective bushing according to claim 1, characterized in that: The composite material protection bushing is an integrally formed structure, and the composite material protection bushing is made of one of titanium alloy and stainless steel.

3. A method for installing a composite material protective bushing according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: The composite material protective bushing is pretreated, and a solid dry film lubricant is applied to the inner diameter hole wall of the composite material protective bushing, and a special coating is added to the outside of the composite material protective bushing; Step 2: placing the pretreated composite material protective bushing into the composite material substrate mounting hole; Step 3: placing the composite protective sleeve together with the composite substrate on top of the top sleeve; Step 4: Place a matching tapered extrusion mandrel on top of the composite material protective bushing, and the tapered extrusion mandrel fits tightly with the hollow part of the composite material protective bushing; Step 5: Start the pulling gun to pull the tapered extrusion core rod out from the bottom of the top sleeve, so that the composite material protection bushing expands radially and squeezes the inner wall of the composite material installation hole, so that the composite material protection bushing is plastically deformed and tightly combined with the composite material installation hole; Step 6: Remove the top cover and the installation is complete.

4. The method for installing a composite material protective bushing according to claim 3, characterized in that: The special coating in step 1 is an adhesive coating.

Images