A composite rod and a method of making the same

Abstract

The present application belongs to the field of composite material processing, and particularly relates to a composite material rod, which uses a fiber liner as a rod body support part, and is coupled with a connecting structure at both ends of the fiber liner, the connecting structure is circumferentially provided with a continuously wound accommodating cavity, fiber composite material is wound along the direction of rotation of the accommodating cavity of the connecting structure, and is wound at a transformed winding angle to the fiber liner to ensure the continuity of the fiber composite material. The fiber composite material is wound on the connecting structure with a spiral continuous groove and the pipe body of the fiber liner, the fiber composite material is partially axial and flat, has no arc surface transition, has high tensile and compression strength, and excellent fatigue performance. The spiral continuous groove of the present application provides a winding direction and a fixed space for the composite material, so that the winding of the composite material can effectively connect the pipe body of the fiber liner and the connecting structure, and ensure the connecting strength.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of composite material processing, and particularly relates to a composite material rod and a preparation method thereof. It is particularly suitable for use in the field of propulsion systems and suspension systems. BACKGROUND

[0002] Composite materials are widely used in the field of aerospace due to their light weight, high specific strength and specific stiffness, good anti-vibration performance and strong designability. At present, a truss structure composed of carbon fiber composite material rods and metal joints and various types of composite material support rods are used as main load-bearing components, mainly bearing axial tensile and compressive loads. The rod and the joint are generally connected by a sleeve jointing and gluing form. The main features of this form are: simple structure, main load-bearing type is shear force, when the main direction of carbon fiber is consistent with the axial direction of the rod, the gluing strength is high, and the load-bearing capacity is strong.

[0003] According to the search, CNCN201910605214.4 discloses a forming method of a composite material pull rod and the composite material pull rod. The metal joint and the composite material layer are integrally wound and formed, co-curing is realized, the assembly of the metal joint and the composite material in the later period is avoided, and high forming efficiency is achieved. The pull rod prepared by combining the automatic dry fiber yarn winding process and the resin pouring two composite material forming process advantages has high strength, high appearance quality and high dimensional accuracy. The metal joint connecting position is wound and locally reinforced by using a non-geodesic winding rule at the joint position, the ability of the pull rod to bear external loads is further increased, the preparation of a light-weight high-strength composite material pull rod is truly realized, and the demand for special loads is met.

[0004] CN201210388517.3 discloses a high tensile load composite material pipe and a preparation method thereof. In view of the technical difficulty of light weight and large tensile load of the composite material pipe, the metal joint form of the composite material pipe is optimized, the trend of the end part of the large tensile load composite material component being damaged due to local stress concentration is effectively weakened, the local optimization of the end part of the pipe is realized through the process optimization of the pipe layer structure, and the composite material pipe suitable for the high tensile load working condition is designed and successfully developed.

[0005] The above-mentioned composite material is wound and covered on the entire metal joint, and then wound back to the rod body. The composite material of the rod body and the metal joint forms an obvious camber surface, stress concentration is easy to occur, and damage or even destruction is more likely to occur under fatigue working conditions. Therefore, a composite material rod design and forming method with high tensile and compressive strength and high fatigue life is invented to solve the problem that the composite material rod is easy to produce stress concentration and more likely to be damaged or even destroyed under fatigue working conditions. SUMMARY

[0006] The composite rod for propulsion system and suspension system requires high tensile and compressive strength, especially high fatigue performance, and the existing composite rod technology cannot fully meet the requirements, how to solve the design and forming method of the composite rod with high tensile and compressive strength and high fatigue life becomes a problem to be solved urgently. The composite rod provided by the present application solves the problem that the connection between the composite rod body and the joint is easy to produce displacement under the vibration of tensile and compressive fatigue load, and the connection reliability of the composite rod manufactured is high.

[0007] The connecting structure with spiral continuous groove is designed, the continuous composite fiber is wound into the groove under suitable tension, and is wound to the rod body at a suitable angle, so that the strength of the composite material is maximized, and the connection strength is ensured.

[0008] In order to achieve the above object, the technical scheme adopted by the present application is:

[0009] The composite rod provided by the present application solves the problem that the connection between the composite rod body and the joint is easy to produce displacement under the vibration of tensile and compressive fatigue load, and the connection reliability of the composite rod manufactured is high.

[0010] The fiber composite material is wound on the connecting structure with spiral continuous groove and the pipe body of the fiber lining pipe, the fiber composite material is partially axial and straight, there is no arc surface transition, the tensile and compressive strength is high, and the fatigue performance is excellent.

[0011] The spiral continuous groove of the present application provides the winding direction and fixing space for the fiber composite material, so that the fiber composite material winding can be effectively connected with the connecting structure and the fiber lining pipe, and the connection strength is ensured.

[0012] Further, the fiber lining pipe is a lining pipe with a hollow inner cavity, the connecting structure is coupled with the end part of the lining pipe, the accommodating cavity is a spiral continuous groove, the connecting structure and the lining pipe are fixed as a whole by the first winding of the fiber composite material, and a certain thickness of the fiber composite material is wound on the periphery to form a bearing structure, the strong structure is formed by continuously winding the fiber composite material in the accommodating cavity of the connecting structure and the lining pipe, and the connection strength of the whole composite rod is ensured. The first wound fiber composite material is preferably high-strength fiber impregnated with high-strength and high-toughness resin, and the second wound fiber composite material is high-strength fiber prepreg.

[0013] The connecting structure is generally made of metal material, is provided with a stepped structure, and a spiral continuous groove is arranged on the outer wall of the stepped structure in a ring shape, so that the fiber composite material is wound through the groove structure for positioning and fixing, and winding is more convenient.

[0014] Further, the inner circular part of the two ports of the liner pipe is an inner tapered surface, which is contracted from the two ports of the liner pipe to the middle of the liner pipe. This structure can make the connecting end of the connecting structure abut against the liner pipe, and the connecting structure can be inserted into the inner tapered surface to make the connection more compact.

[0015] Further, the connecting structure is two, which are arranged on the two sides of the fiber liner pipe, and the spiral directions of the spiral continuous grooves of the two oppositely arranged connecting structures are opposite.

[0016] Further, the ratio of the groove width to the groove depth of the spiral continuous groove is 1-4:1. The arrangement of this structure is particularly beneficial to the winding of the fiber composite material, and the limitation of the ratio of the groove width to the groove depth makes the contact area of the spiral continuous groove and the fiber composite material larger.

[0017] Further, the connecting structure is a metal joint, the two side ends of the connecting structure are internally threaded, and the rotation directions of the internal threads at the two ends are opposite, which are used for fixing and connecting external mechanical systems.

[0018] Further, the tail part of the spiral continuous groove of the connecting structure is provided with a circular table structure, and the length and taper of the circular table structure are consistent with the inner circular tapered surfaces of the two end parts of the liner pipe.

[0019] Another object of the present application is to disclose a preparation method of the composite material rod, comprising the following steps:

[0020] S1. Fiber liner pipe preparation: prepare a metal rod mold, install it on a winding device, wind the fiber liner pipe material on the mold under the action of tension, and wind to the target thickness; after winding, transport to a rotary curing furnace for first-time curing;

[0021] S2. Fiber liner pipe finishing: demold to obtain a fiber liner pipe blank, and process two end tapered surfaces of the fiber liner pipe;

[0022] S3. Sand blasting of the connecting structure and the inner tapered surface of the fiber liner pipe;

[0023] S4. Coupling of the connecting structure and the fiber liner pipe: clean the circular table structure of the connecting structure and the inner tapered surface of the fiber liner pipe, uniformly brush high-strength and high-toughness adhesive, and then align and bond, to ensure that the two tapered surfaces are completely matched in place and then perform second-time curing;

[0024] S5. Winding of the fiber composite material: install the prepared connecting structure-fiber liner pipe blank to a numerical control winding device, and clean the surface to ensure that there is no oil stain;

[0025] S51. Set the winding procedure, first use fiber composite material along the (high-strength fiber impregnated with high-toughness resin) along the spiral continuous groove of the connecting structure, adjust to large angle winding when winding to the fiber liner pipe, adjust to spiral continuous groove winding again at the other end connecting structure, until more than 1 / 2 of the groove depth;

[0026] S52. Replace the fiber composite material (high-strength fiber prepreg) for re-winding, timely change the winding angle, until the target outer diameter, winding angle and ply [± 14 / 90 / 90 / ± 18 / 90 / 90 / ± 14] 3S, finally wind 2-4 layers of heat shrink film;

[0027] S6. After the whole third curing and cooling, the load-bearing structure is formed, and the heat shrink film is removed, that is, the composite rod product.

[0028] Further, the first curing process is: first heated to 80-120℃, and kept for 1-4h; then the temperature is raised to 120-160℃, and kept for 1-4h, finally the temperature is lowered to below 150℃ and kept for at least 2h; the second curing process is keeping at 100-120℃ for 2-5h, and keeping at 140-160℃ for 2-4h; the third curing process is consistent with the first curing process.

[0029] Further, the winding angle of the spiral continuous groove winding is 70-78°, and the winding angle is adjusted to 84-86° when winding to the fiber liner pipe.

[0030] Compared with the prior art, the beneficial effects of the application are:

[0031] The composite rod of the application solves the problems of strength instability and low fatigue life of slender composite rod products, and greatly improves the product reliability.

[0032] The composite rod solves the problems of strength instability and low fatigue life of slender composite rod products, and greatly improves the product reliability.

[0033] Further, the manufacturing method of the high-strength high-fatigue-life composite rod is disclosed, which is completed through a plurality of processes such as fiber liner pipe preparation, metal connecting structure processing, metal connecting structure and fiber liner pipe fixed by taper surface bonding, and load-bearing structure manufacturing. The composite rod prepared by the method has stable performance and high product consistency. BRIEF DESCRIPTION OF DRAWINGS

[0034] Fig. 1 The overall structure of the composite rod according to the present application is shown in the figure.

[0035] Fig. 2 The structure of the inner liner tube of the composite rod according to the present application is shown in the figure.

[0036] Fig. 3 The structure of the connecting structure of the composite rod according to the present application is shown in the figure.

[0037] In the figure, 1 is the liner tube, 2 is the connecting structure, 3 is the load-bearing structure, 11 is the inner taper surface, 21 is the helical continuous groove, and 22 is the circular truncated cone structure. DETAILED DESCRIPTION

[0038] In order to facilitate the description and understanding of the present application, the following will be combined with the accompanying Figs. 1-3 The embodiments of the present application will be described in detail. Embodiment 1

[0039] The fiber liner tube of the composite rod in this embodiment is the rod body support part, and the connecting structure 2 is coupled at both ends of the fiber liner tube. The fiber composite material is wound along the direction of rotation of the accommodating cavity of the connecting structure 2, and the fiber liner tube is wound at a transformed winding angle to ensure the continuity of the composite high-strength fiber material. The fiber liner tube in this embodiment is the liner tube 1 with a hollow inner cavity, and the connecting structure 2 is coupled with the end part of the liner tube 1. The accommodating cavity is the helical continuous groove 21, and the connecting structure 2 and the liner tube 1 are fixed as a whole by winding the fiber composite material. The fiber composite material winding serves as the framework of the composite rod. The solidified fiber prepreg is wound outside the fiber composite material to form the load-bearing structure 3, and the overall composite rod connection strength is ensured by utilizing the strength of the composite material.

[0040] The fiber liner tube in this embodiment is prepared by one of the winding and pultrusion molding methods using one or more of glass fiber, aramid fiber, carbon fiber, and basalt fiber. The overall structure of the fiber liner tube is cylindrical, and the inner circular part of the two ports of the liner tube 1 is an inner taper surface that is contracted from the two ports of the liner tube 1 to the middle of the liner tube. The design of this structure is to couple the connecting structure 2 with the end part of the liner tube 1. Correspondingly, the circular truncated cone structure is arranged at the connecting end of the connecting structure 2 and the liner tube 1, and the length and taper of the inner circular part of the two end parts are consistent with the length and taper of the inner taper surface. In this embodiment, in order to ensure the strength and lightweight of the product, the fiber liner tube is preferably 1.8-2.5mm in thickness, 1:9-1:10.5 in taper of the inner taper surface, 20-30mm in length, and not less than 12.5 in surface roughness.

[0041] The connecting structure 2 is provided with a stepped structure, and a helical continuous groove 21 is arranged on the outer wall of the stepped structure in a ring shape, so that the fiber composite material is wound and positioned and fixed through the groove structure, and the winding is more convenient. The ratio of the groove width to the groove depth of the helical continuous groove 21 is 1-4:1, and the helical angle is 70-78°; in this embodiment, the groove width is preferably 4-8 mm, the groove depth is 2-5 mm, the length is 80-120 mm, and the helical directions of the helical continuous grooves 21 arranged oppositely left and right are opposite. The arrangement of such a structure is particularly beneficial to the winding of the fiber composite material, and the limitation of the ratio of the groove width to the groove depth makes the contact area between the helical continuous groove and the fiber composite material larger.

[0042] And the connecting structure 2 is a metal joint, the two ends of the connecting structure 2 are internally threaded, and the internal threads at the two ends are opposite in rotation direction, used for fixedly connecting an external mechanical system.

[0043] In this embodiment, the circular truncated cone structure 22 of the connecting structure 2 is connected to the inner conical surface of the liner pipe 1 through a high-strength tough adhesive, the roughness of the inner liner pipe bonding surface is not less than 12.5, and the connecting part is a beveled structure. That is, the connecting structure 2 and the liner pipe 1 are tightly connected together.

[0044] The load-bearing structure 3 in this embodiment is composed of high-strength fibers (such as carbon fibers, aramid fibers, etc.) and high-strength and high-toughness resins. The fibers impregnated with resin are wound along the helical continuous groove, and the winding of the inner liner pipe is adjusted to a large angle to ensure the continuity of the fibers connecting the metal connecting structure. Embodiment 2

[0045] This embodiment proposes a preparation method of the composite rod of embodiment 1, which comprises the following steps:

[0046] S1. Fiber liner pipe preparation: prepare a metal rod mold, chrome plate the surface, install it on a winding device, and wind the fiber liner pipe material on the mold under the action of tension to the target thickness; in this embodiment, carbon fibers are wound on the mold under the action of 60-65 N tension, and the winding thickness is 1.8-2.5 mm; after winding, it is transferred to a rotary curing oven for the first time; the curing process is: first heated to 80-120℃, and kept for 1-4h; then the temperature is raised to 120-160℃, and kept for 1-4h, and finally the temperature is lowered to below 150℃ and kept for at least 2h; in this embodiment, it is heated to 100℃ and kept for 2h, then heated to 120℃ and kept for 2h, and heated to 150℃ and kept for 2h again.

[0047] S2. Fiber liner pipe finishing: demolding to obtain a fiber liner pipe blank, and machining two end conical surfaces of the fiber liner pipe by using a diamond tool; so that the conical surface has no pits, fiber delamination and other damages.

[0048] S3. Sandblasting the connecting structure and the inner taper surface of the fiber liner pipe; specifically, sandblasting the metal joint round table and the inner taper surface of the liner pipe with 36-mesh white jade, at a pressure of 3-5 MPa.

[0049] S4. Coupling of the connecting structure and the fiber liner pipe: clean the round table structure of the connecting structure and the inner taper surface of the fiber liner pipe, brush and coat high-strength and high-toughness adhesive, and then align and bond them, and ensure that the taper surfaces of the two are completely matched in place before performing the second curing; the curing process is to keep the temperature at 100-120°C for 2-5 h and at 140-160°C for 2-4 h.

[0050] S5. Winding of the fiber composite material: install the connecting structure-fiber liner pipe blank prepared above to the numerical control winding equipment, and clean the surface to ensure that there is no oil stain.

[0051] S51. Set the winding program, first wind the high-strength fiber impregnated with high-strength and high-toughness resin along the spiral continuous groove 21 of the connecting structure, adjust to large-angle winding when winding to the fiber liner pipe, and the winding angle is 86°; adjust to winding along the spiral continuous groove again when winding to the other end connecting structure, until more than 1 / 2 of the groove depth, which is 4 / 5 of the groove depth in this embodiment.

[0052] S52. Wind the high-strength fiber prepreg, the winding angle and the layup [±14 / 90 / 90 / ±18 / 90 / 90 / ±14] 3S, and finally wind 2-4 layers of heat-shrinkable film.

[0053] S6. Perform the third curing as a whole, and the process parameters are the same as those of the first curing; after cooling, remove the heat-shrinkable film, and the composite rod product is formed. Example 3

[0054] In the preparation method of the composite rod of this embodiment, the fiber liner pipe is made of high-strength glass fiber, S51. Set the winding program, first wind the high-strength fiber impregnated with high-strength and high-toughness resin along the spiral continuous groove 21 of the connecting structure, adjust to large-angle winding when winding to the fiber liner pipe, and the winding angle is 84°; adjust to winding along the spiral continuous groove again when winding to the other end connecting structure, until 5 / 6 of the groove depth; the rest is the same as in Example 2.

[0055] Take the composite rod of Example 1 as an example, perform fatigue test under compression load of 4.9-24.1 kN and tensile load of 11.1-30.2 kN, a total of 13 groups, and the test results are as follows.

[0056]

[0057] The composite rod of the present application is wound into the groove by continuous composite fiber under suitable tension and is wound to the rod body at a suitable angle, which maximizes the strength of the composite material and ensures the connection strength. The tensile and compressive strength is high, and the fatigue performance is excellent.

[0058] The above is only an embodiment of the present application, which is not limited to the field involved in this embodiment. The specific structure and characteristics known in the art and other common knowledge in the scheme are not described in detail. It should be pointed out that for those skilled in the art, without departing from the content of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, which will not affect the effect and practicality of the patent. The protection scope claimed in the present application should be subject to the content of its claims, and the specific implementation mode and other records in the specification can be used to explain the content of the claims.

Claims

1. A method for preparing a composite material rod, characterized in that, The composite material rod uses a fiber liner as the rod body support. Connecting structures (2) are coupled to both ends of the fiber liner. The connecting structures (2) have continuously wound cavities circumferentially. The fiber composite material is wound along the spiral direction of the cavities in the connecting structures (2) until the fiber liner is wound at varying winding angles to ensure the continuity of the fiber composite material. The fiber liner is a hollow liner (1), and the connecting structures (2) are coupled to the ends of the liner (1). The inner circular portions of the two ends of the liner (1) are inner conical surfaces (11), and the cavities are... A spiral continuous groove (21) is provided at the tail of the spiral continuous groove (21) with a frustum structure (22). The connecting structure (2) and the liner (1) are fixed together by the first winding of the fiber composite material. Then, the fiber composite material is wound around the periphery to form a load-bearing structure (3). The fiber composite material is wound on the connecting structure with the spiral continuous groove and the fiber liner to keep the composite material part axially straight and without arc transition. The fiber composite material is continuously wound on the accommodating cavity and the liner of the connecting structure to form a strong structure, ensuring the overall connection strength of the composite material rod. Its preparation method includes the following steps: S1. Fiber liner preparation: Prepare a metal rod mold and install it on the winding equipment. Wind the fiber liner material onto the mold under tension until the target thickness is reached. After winding, transfer it to a curing oven for the first curing. S2. Finishing of fiber liner: Demolding to obtain fiber liner blank, and machining the tapered surfaces at both ends of the fiber liner; S3. Sandblast the connecting structure and the inner conical surface of the fiber liner; S4. Coupling of connecting structure and fiber liner: Clean the frustum structure (22) of the connecting structure and the inner conical surface (11) of the fiber liner, apply high-strength and high-toughness adhesive, and then align and bond them. Ensure that the conical surfaces of the two are fully fitted and then perform a second curing. S5. Winding of fiber composite materials: The above-prepared connecting structure - fiber liner blank is installed on a CNC winding machine and the surface is cleaned. S51. Set the winding program. First, use fiber composite material to wind along the spiral continuous groove (21) of the connecting structure for the first time. When winding to the fiber liner, adjust to a large angle winding. When reaching the other end of the connecting structure, readjust to wind along the spiral continuous groove until it is greater than 1 / 2 of the groove depth. S52. Rewind the fiber composite material, changing the winding angle as needed until the target outer diameter is reached, and finally wind multiple layers of heat-shrink film. S6. After the whole is cured and cooled for the third time, a load-bearing structure is formed (3). Remove the heat shrink film, that is, the finished composite material rod.

2. The method for preparing the composite material rod according to claim 1, characterized in that, The inner conical surface (11) contracts from the two ends of the liner (1) toward the middle of the liner (1).

3. The method for preparing the composite material rod according to claim 2, characterized in that, There are two connecting structures (2), which are placed on both sides of the fiber liner tube. The spiral directions of the spiral continuous grooves (21) of the two connecting structures (2) are opposite.

4. The method for preparing the composite material rod according to claim 3, characterized in that, The ratio of the width to the depth of the spiral continuous groove (21) is 1-4:

1.

5. The method for preparing the composite material rod according to claim 4, characterized in that, The connection structure (2) is a metal connector. The two ends of the connection structure (2) are internal threads, and the internal threads at both ends are in opposite directions, which is used to fix and connect to an external mechanical system.

6. The method for preparing the composite material rod according to claim 5, characterized in that, The length and taper of the frustum structure are consistent with the inner conical surfaces at both ends of the liner.

7. The method for preparing the composite material rod according to claim 1, characterized in that, The first curing process is as follows: first heat to 80-120℃ and hold for 1-4 hours; then raise the temperature to 120-160℃ and hold for 1-4 hours; finally cool down to below 150℃ and hold for at least 2 hours. The second curing process is as follows: hold at 100-120℃ for 2-5 hours and at 140-160℃ for 2-4 hours. The third curing process is the same as the first curing process.

8. The method for preparing the composite material rod according to claim 1, characterized in that, The winding angle of the spiral continuous groove (21) is 70-78°, and the winding angle is adjusted to 84-86° when winding the fiber liner.

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