Fastener based on composite material

Abstract

The invention provides a fastener based on a composite material. The fastener comprises a nut, a screw rod, a gasket, a clamping piece pair and a nut. The screw rod is divided into a smooth section and a threaded section; the nut is connected with the smooth section; the smooth section and the surface of the nut are provided with woven composite materials; the gasket sleeves the screw rod and is positioned at the joint of the smooth section and the threaded section; the clamping piece pair is arranged on the outer side of the threaded section and connected with the threaded section and the nut through the inner threads and the outer threads respectively. All the components of the fastener are made of composite materials, corrosion resistance is high, the fatigue problem in connection of composite material components can be effectively solved, the application field is wide, and the service life is long.

Description

Technical Field

[0001] The present invention relates to the technical field of fasteners, and in particular to a fastener based on a composite material. Background Art

[0002] Composite components have been widely used in modern engineering. Due to their excellent mechanical properties and lightweight characteristics, they have become important materials in the fields of aerospace, automobile manufacturing, etc. However, metal fasteners are still traditionally used in the connection and fastening of composite components. Although this combination of metal and composite materials can provide the necessary mechanical strength, it also brings potential fatigue problems. There is obvious heterogeneity between metal materials and composite materials, and there are significant differences in stress and strain characteristics. Especially under cyclic loading conditions, the fatigue performance of the contact interface between metal fasteners and composite materials is poor, and microcracks are prone to occur and gradually expand, eventually leading to failure of the connection. In addition, the use of metal fasteners can lead to electrochemical corrosion problems, which accelerates the performance degradation of fasteners and composite materials.

[0003] Although the composite fasteners currently on the market have alleviated the fatigue problem in the connection between metal and composite materials to a certain extent, stress concentration still exists in the threaded section and the screw and nut connection. This stress concentration not only causes the yield and fracture of local materials, but also easily causes the loosening and damage of fasteners. This problem is particularly prominent in high-frequency vibration and impact load environments, posing a serious threat to the overall reliability of the structure. Therefore, how to design and manufacture composite fasteners that can effectively disperse stress and improve fatigue performance has become an important topic of current technical research. In response to this problem, it is necessary to deeply understand the mechanical properties of composite materials and the stress distribution law of threaded connections, and to improve the performance of composite fasteners through optimized design and advanced manufacturing processes.

[0004] High-performance fiber-reinforced composites are widely used in various industries due to their excellent mechanical properties. Common high-performance fiber-reinforced composites include glass fiber-reinforced composites, carbon fiber-reinforced composites and aramid fiber-reinforced composites. Aramid fibers and other organic fibers are similar to glass fibers and are easy to weave into various fabrics, which facilitates the molding process of composite materials. Domestic and foreign researchers have conducted a lot of research on the fiber surface modification of aramid fiber composites. By compounding aramid fabric with flexible epoxy resin, highly flexible aramid fabric-reinforced epoxy composites are obtained. In addition, aramid short fibers are mainly used to reinforce thermoplastic composites to improve their fracture strength. Aramid fiber-reinforced resin-based composites have high strength, good corrosion resistance and fatigue resistance, and have broad application prospects.

[0005] At present, the preparation methods of composite threaded fasteners mainly include pultrusion, compression molding, injection molding and braiding-pressure impregnation. Pultrusion has high production efficiency, low cost and stable product quality, but it can only produce threaded products with constant cross-section and is not suitable for threaded products with steps. The mold design of the compression molding method is complex, and the surface threads will also make demolding difficult. The bolts prepared by the braiding-pressure impregnation method have high mechanical strength, but the fibers need to be woven, and the fibers will be damaged when turning the threads. Injection molding is the preferred preparation method. The finished product manufactured by this method has good integrity and is suitable for mass production. Summary of the invention

[0006] The present invention aims at solving the problems in the prior art and proposes a fastener based on composite materials. The fastener has the advantages of strong environmental adaptability, convenient assembly and disassembly, fast construction, strong corrosion resistance and good insulation. In a high-frequency vibration environment, the fastener has obvious advantages in connecting composite components, can effectively avoid potential fatigue problems, and improve the reliability and service life of the overall structure.

[0007] The present invention is achieved through the following technical scheme: a fastener based on composite materials, including a nut, a screw, a washer, a pair of clips, and a nut; the screw is divided into a smooth section and a threaded section; the nut is connected to the smooth section; the surfaces of the smooth section and the nut are provided with a woven composite material; the washer is sleeved on the screw and is located at the connection between the smooth section and the threaded section; the pair of clips is arranged on the outside of the threaded section and is connected to the threaded section and the nut respectively through internal and external threads.

[0008] Preferably, the threaded section is of an annular groove type, the thread depth remains unchanged along the rod end direction, and the thread spacing gradually decreases from the smooth section to the threaded section.

[0009] Preferably, the woven composite material is an aramid fiber composite material; the woven composite material is a plain weave type.

[0010] Preferably, the fiber direction of the smooth section of the screw is spiral with respect to its axial direction.

[0011] Preferably, the nut type is a countersunk type.

[0012] Preferably, the nut is made of a composite material, and the fiber distribution direction is circumferential; the nut is provided with an internal thread, and the internal thread type is a helical thread.

[0013] Preferably, the pair of clips are two clips with semicircular cross-sections and are provided with internal threads and external threads; the external threads of the pair of clips are oblique threads; and the pair of clips are made of composite materials.

[0014] Preferably, the gasket is made of a rubber-like soft material.

[0015] Preferably, the screw rod, nut, clip pair and nut are made of glass fiber reinforced plastic, basalt fiber reinforced resin or carbon fiber reinforced composite material.

[0016] The beneficial effects of the present invention are as follows: the screw is divided into a smooth section and a threaded section, the surface of which is provided with a woven composite material and is manufactured by an integrated molding method; the clip pair is used as a transition connection to avoid the stress concentration problem and nut dislocation phenomenon caused by directly setting the oblique thread, thereby improving the fatigue performance of the overall connection; the various components of the fastener are made of composite materials, which have strong corrosion resistance, can effectively solve the fatigue problem in the connection of composite components, have a wide range of applications, and have a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of fastener installation molding; Figure 2 This is a detailed view of the screw. Figure 3 This is a local detail diagram of the clip pair; Figure 4 This is a partial detail diagram of the nut; Figure 5 A schematic diagram of the steps for installing composite panels and fasteners; In the figure: 1 is a nut; 2 is a screw; 21 is a smooth section; 22 is a threaded section; 3 is a washer; 4 is a pair of clips; 41 is an internal thread; 42 is an external thread; 5 is a nut; 6 is a braided composite material; 7 is a composite material plate. Specific implementation methods

[0018] The present invention is further described below in conjunction with specific embodiments and drawings. More details are set forth in the following description to facilitate a full understanding of the present invention, but the present invention can obviously be implemented in a variety of other ways different from the description herein. For those skilled in the art, any replacement, improvement or transformation made to the embodiments of the present invention is within the scope of protection of the present invention, and the scope of protection of the present invention should not be limited by the content of this specific embodiment. It should be noted that the subsequent other drawings are only used as examples and are not necessarily designed according to the scale and size in the examples, and should not be used as a limitation on the scope of protection actually required by the present invention.

[0019] like Figure 1 As shown, the present invention provides a fastener based on composite materials, including a nut 1, a screw rod 2, a washer 3, a pair of clips 4 and a nut 5.

[0020] like Figure 2As shown, the screw 2 is divided into a smooth section 21 and a threaded section 22, with a woven composite material 6 on the surface, and is manufactured by an integrated molding method. The size of the smooth section 21 is determined according to the design requirements to adapt to composite components of different thicknesses. The threaded section 22 is a ring groove type, and the cross section adopts a trapezoidal cross section. The thread depth remains unchanged along the free end of the threaded section 22, and the thread spacing gradually decreases to match the force characteristics of the threaded section and improve the stability of the connection. The nut 1 is a countersunk type, connected to the smooth section 21 of the screw 2, and is designed to be an obtuse angle, which reduces stress concentration when connected to the screw 2 and enhances the connection strength. High-strength and high-toughness materials such as woven composite materials 6 such as aramid fibers are used for the screw 2 and the nut 1 to improve their bearing capacity.

[0021] like Figure 2 As shown, the braided composite material 6 uses high-strength and high-tenacity fibers such as aramid fibers. The material is plain woven, and the fiber direction is spiral with the axial direction of the smooth section 21 of the screw to improve the force characteristics of the smooth section 21.

[0022] like Figure 3 As shown, the clip pair 4 is two clips with semicircular cross-sections, with internal threads 41 and external threads 42, the internal threads 41 match the threaded section 22 of the screw, and the external threads 42 are oblique threads, which match the internal threads of the nut 5. The cross section of the internal thread 41 adopts a trapezoidal cross section, and the pitch of the threads gradually decreases along the axial direction of the free end of the threaded section 22, and the thread depth remains unchanged, so as to improve the bearing capacity of the internal thread 41.

[0023] like Figure 4 As shown, the internal thread of the nut 5 is also an oblique thread, which is used to tighten the clamping piece pair 4.

[0024] like Figure 5 As shown, the fastener installation process of the present invention is as follows: First, insert the main part of the fastener (screw and nut) into the composite material plate 7. Then, place the washer 3 on the component to be connected, and use the clip pair 4 and the nut 5 to further tighten the screw 2. Finally, tighten the nut 5 to complete the constraint of the screw 2. The entire installation process is quick and reliable, ensuring the stability of the fastener and the quality of the connection. Apply torque through the nut 5 to tighten the clip pair 4 to constrain the screw thread section 22. The clip pair 4 serves as a transition connection to avoid the stress concentration problem caused by directly setting the oblique thread and the phenomenon of nut 5 dislocation, thereby improving the fatigue performance of the overall connection. The washer 3 is made of soft materials such as rubber to improve the redundancy of the fastener connection and avoid the adverse effects caused by thread manufacturing errors.

[0025] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these examples and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the scope of protection of the present invention.

Claims

1. A fastener based on a composite material, characterized in that: It includes a nut, a screw rod, a washer, a pair of clips, and a nut; the screw rod is divided into a smooth section and a threaded section; the nut is connected to the smooth section; the surfaces of the smooth section and the nut are provided with a woven composite material; the washer is sleeved on the screw rod and is located at the connection between the smooth section and the threaded section; the pair of clips is arranged on the outside of the threaded section and is connected to the threaded section and the nut through internal and external threads respectively.

2. The composite material-based fastener according to claim 1, characterized in that: The threaded section is of an annular groove type, the thread depth remains unchanged along the rod end direction, and the thread spacing gradually decreases from the smooth section to the threaded section.

3. The composite material-based fastener according to claim 1, characterized in that: The braided composite material is an aramid fiber composite material; the braiding type of the braided composite material is a plain weave type.

4. The composite material-based fastener according to claim 3, characterized in that: The fiber direction of the smooth section of the screw is spiral with respect to its axial direction.

5. The composite material-based fastener according to claim 1, characterized in that: The nut type is a countersunk type.

6. The composite material-based fastener according to claim 1, characterized in that: The nut is made of a composite material, and the fiber distribution direction is circumferential; the nut is provided with an internal thread, and the internal thread type is an oblique thread.

7. The composite material-based fastener according to claim 1, characterized in that: The pair of clips are two clips with semicircular cross-sections and are provided with internal threads and external threads; the external threads of the pair of clips are oblique threads; the pair of clips are made of composite materials.

8. The composite material-based fastener according to any one of claims 1 to 7, characterized in that: The material of the gasket is a rubber-like soft material.

9. The composite material-based fastener according to any one of claims 1 to 7, characterized in that: The materials of the screw rod, nut, clip pair and nut are glass fiber reinforced plastic, basalt fiber reinforced resin or carbon fiber reinforced matrix composite material.

Images