CN120773377A - Large-opening composite material shell bonding forming method for embedded pin joint - Google Patents

Abstract

The invention provides a large-opening composite material shell bonding molding method of a pre-buried pin joint, which comprises the steps of preparing a joint of a pre-buried yarn hanging pin, bonding an elastic layer/joint/heat insulation layer, preparing a winding core mold, winding a composite material on the winding core mold, solidifying and molding the shell, and processing the yarn hanging pin. The forming method realizes uniform and stable winding of the large-opening shell fiber through the embedded yarn hanging pin joint, simplifies the winding forming process of the large-opening shell, avoids secondary processing of a winding layer and damages the continuity of the fiber, and simultaneously designs the bonding area of the joint and the heat insulation layer and the length of the annular groove of the joint through local reinforcement of the joint, thereby improving the axial bearing capacity of the large-opening shell and taking the winding forming process and the bearing performance of the shell into consideration.

Description

Large-opening composite material shell bonding forming method for embedded pin joint

Technical Field

The invention belongs to the field of manufacturing of composite material shells of solid rocket engines, and particularly relates to a bonding molding method of a large-opening composite material shell of a pre-buried pin joint.

Background

The carbon fiber composite material shell has been widely used for solid rocket engine shells due to the advantages of light weight, high strength, strong designability and the like. In recent years, high mass ratio and high thrust weight requirements are put forward for solid rocket engines, and a large-opening composite shell meeting the requirement of free filling of shaped charges becomes an important direction for developing high-performance engines. However, for the large-opening composite shell, the requirements of good fiber winding process, strong joint bearing capacity and good sealing performance are met, which clearly brings challenges to the molding and manufacturing of the large-opening shell.

The large-opening composite material shell is mainly wound through a prefabricated false end socket, the end socket is cut off after forming to form a large-opening structure, meanwhile, the large-opening end is radially perforated and connected with an external structure through a pin, and a metal piece is embedded into a winding layer to form a sealing surface in the shell sealing structure, such as patent CN221277885U. In order to solve the problem of large fiber consumption caused by the prefabricated false head, the large-opening winding is performed in a mode of arranging the wire hanging pin, but the shell needs to perform secondary processing on the winding layer at the position of the wire hanging pin after forming, and the continuity of winding fibers is damaged. Although the forming method is easy to realize in process, the connecting structure is complex, the fiber strength is weakened by the perforation of the winding layer or secondary processing, and the sealing surface is easy to deform in the winding forming process, secondary processing is needed, so that the shell forming process is increased. Aiming at the problems, the invention provides a large-opening fiber winding composite material shell bonding molding method for embedded pin joints, which combines a winding molding process and shell bearing performance.

Disclosure of Invention

In order to overcome the defects in the prior art, the inventor conducts intensive research, provides a large-opening composite material shell bonding molding method for embedding pin joints, solves the problems that fibers are easy to slip, the axial bearing capacity is weak, a winding layer and a sealing surface (namely the inner surface of the joint) are secondarily machined in the molding process of the large-opening composite shell, and simplifies the shell winding molding process.

The technical scheme provided by the invention is as follows:

A large-opening composite material shell bonding molding method of a pre-buried pin joint comprises the following steps:

Preparing two groups of joints, namely a front joint and a rear joint, processing an annular groove on the outer wall of the joint, and embedding a yarn hanging pin in the annular groove area;

bonding an elastic layer with pin holes on the outer surface of the joint, and bonding a heat insulation layer on the inner surface of the joint to obtain the joint with the elastic layer and the heat insulation layer;

The method comprises the steps of sleeving a sand core mould on a winding mandrel and positioning, sleeving a front joint and a rear joint with an elastic layer and a heat insulation layer on the front section and the rear section of the sand core mould, coating the middle section of the sand core mould with the heat insulation layer, overlapping the heat insulation layer dislocation positions of the front joint and the rear joint, winding at least 1 layer of dry fiber on the outer surface of the combination, and presulfiding the heat insulation layer to obtain the winding mandrel;

Winding a gum dipping fiber tow on a winding mandrel, penetrating the gum dipping fiber tow by a yarn hanging pin in the winding process, and penetrating a reinforcing material to locally reinforce the annular groove of the joint;

And (3) curing the wound composite material shell, demolding after curing, and cutting off the yarn hanging pins of the protruding parts of the composite material shell to obtain the large-opening composite material shell with the embedded pin joints.

The large-opening composite material shell bonding molding method for the embedded pin joint has the following beneficial effects:

(1) In addition, the annular groove is designed to provide a height space for the implantation of the yarn hanging pin in the fiber winding layer, the yarn hanging pin pierces the fiber impregnated fiber tows in the winding process, so that uniform and stable winding of the fiber of the large-opening shell is realized, the winding forming process of the large-opening shell is simplified, secondary processing of the winding layer is avoided, and the continuity of the fiber is damaged.

(2) According to the large-opening composite material shell bonding molding method for the embedded pin joint, the carbon cloth or the prepreg cloth is inserted into the annular groove of the joint to locally reinforce the annular groove of the joint, the reinforcing layer is positioned between the spiral winding layer and the annular winding layer, the bonding area of the specific joint and the heat insulation layer and the specific annular groove length are designed, the axial bearing capacity of the joint is effectively improved, and the process is simple and efficient.

(3) The method for bonding and forming the large-opening composite material shell of the embedded pin joint provided by the invention has the advantages that the spiral and annular alternate winding mode is adopted for the impregnated fiber tows on the winding core mould, the combined winding mode can be accurately matched with the shell load, the annular bearing performance of the shell is improved, the sufficient axial strength is ensured, the balance of strength and rigidity is realized, and the fiber can be arranged according to the annular and axial stress distribution directions of the shell by adopting the given determination mode of the winding angle, the thickness of the spiral winding layer and the annular winding layer of the spiral winding mode, so that the high-efficiency utilization of the fiber strength and the minimization of the material consumption are realized, and the structural efficiency is improved.

Drawings

FIG. 1 is a schematic diagram of a large-opening fiber-wound composite shell structure with embedded pin joints;

FIG. 2 is a schematic structural view of a pre-buried pin joint with a winding layer provided by the invention;

FIG. 3 is a schematic view of an elastic layer/joint/insulation layer combination provided by the present invention;

fig. 4 is a schematic structural view of a winding core mold according to the present invention.

Description of the reference numerals

1-Fiber winding layer, 2-connector, 3-elastic layer, 4-yarn hanging pin, 5-heat insulating layer, 6-winding mandrel, 7-front positioning flange and 8-rear positioning flange.

Detailed Description

The features and advantages of the present invention will become more apparent and clear from the following detailed description of the invention.

The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

The invention provides a bonding and forming method of a large-opening composite material shell of a pre-buried pin joint, which is shown in fig. 1 and a partial view in fig. 2, and comprises the following steps:

S1, preparing a joint of a pre-buried yarn hanging pin

The joints of the embedded yarn hanging pins are required to be arranged at the two ends of the composite shell and used for being connected with an external structure. The connector comprises a front connector and a rear connector, the outer wall of the connector is provided with an annular groove, and after the impregnated fiber tows are wound outside the connector to be molded, an embedded structure is formed in the annular groove area, so that the axial tensile strength of the connector is improved.

The fiber in the impregnated fiber tows is carbon fiber, glass fiber and the like, and the resin is epoxy resin, phenolic resin and the like.

The yarn hanging pin 4 is embedded in the annular groove area, the annular groove is designed to provide a height space for the implantation of the yarn hanging pin 4 in the fiber winding layer 1, the yarn hanging pin is embedded through the connector to realize uniform and stable winding of the fiber of the large-opening shell, the winding forming process of the large-opening shell is simplified, secondary processing of the winding layer is avoided, and the continuity of the fiber is damaged.

The length L_comp of the annular groove is determined by:

wherein P is the set bearing pressure of the shell, D₁ is the outer diameter of the joint groove, S_comp is the interlayer shearing strength of the composite material, K_safe is the safety coefficient, and K is the effective contact area coefficient.

The taper of the top of the yarn hanging pin is 15-45 degrees, the length is adjusted according to the actual winding requirement, the top of the cone section is required to be processed smoothly, and the damage to the impregnated fiber tows in the winding process is avoided.

S2, elastic layer/joint/heat insulation layer bonding

Referring to fig. 3, a layer of adhesive is uniformly coated on the outer surface of the joint 2 and bonded with the elastic layer 3 with pin holes, and a layer of adhesive is uniformly coated on the bonding area of the heat insulation layer on the inner surface of the joint 2 and bonded with the heat insulation layer 5 to obtain the joint with the elastic layer and the heat insulation layer.

The heat insulating layer 5 is made of ethylene propylene diene monomer. The elastic layer 3 adopts nitrile rubber, and is used for improving the bonding strength of the fiber winding layer 1 and the joint 2 and reducing the forming stress of the fiber winding layer.

The bond length L of the joint to the insulation layer is determined by:

Wherein S₁₂ is the shear strength between the heat insulating layer and the joint, and D₂ is the diameter of the joint-heat insulating layer bonding surface.

S3, preparing a winding core mold

The method comprises the steps of sleeving a sand core mould on a winding mandrel 6, positioning the sand core mould through a front positioning flange 7 and a rear positioning flange 8, sleeving a front joint and a rear joint with an elastic layer and an insulating layer on the front section and the rear section of the sand core mould, coating the insulating layer on the middle section of the sand core mould and overlapping with the insulating layer of the front joint and the rear joint, winding at least 1 layer of spiral and at least 1 layer of annular dry fiber on the outer surface of the combination body after the insulating layer is coated, shaping and restraining the insulating layer, putting the combination body into a curing furnace to presulfiding the insulating layer, and vulcanizing at a temperature of 100-120 ℃ for 3-5 hours to obtain the winding core mould, wherein the curing temperature is shown in fig. 4.

The lap joint length of the heat insulation layer coated on the middle barrel section of the sand core mold and the heat insulation layer of the front joint is 10-15 mm, and the lap joint length of the heat insulation layer coated on the middle barrel section of the sand core mold and the heat insulation layer of the rear joint is 10-15 mm.

S4, winding the composite material

And (3) winding the impregnated fiber tows on the winding core mould prepared in the step (S3) according to a designed layering scheme. Because the large-opening composite material shell is in a full-opening form at two ends, the composite material shell adopts a front-back equal-pole hole winding scheme. In the winding process, the yarn hanging pins pierce through the impregnated fiber tows, so that the slippage of the fibers is avoided, the fibers are ensured to be wound along a designed winding path, the deviation from the design track is avoided, the uniform and stable winding of the fibers is realized, the secondary processing of a winding layer is avoided, and the continuity of the fibers is damaged.

The impregnated fiber tows on the winding core mould adopt a spiral and annular alternate winding mode. The winding angle α of the spiral winding manner is determined by the following formula:

Wherein D₁ is the set diameter of the front pole hole, D₂ is the set diameter of the rear pole hole, and D_out is the outer diameter of the winding core mold barrel section.

The spiral wound layer thickness h_α is determined by:

Where k_s is the stress balance coefficient and σ_fb is the fiber strength.

The hoop winding layer thickness h_θ is determined by:

In the winding process, carbon cloth or prepreg cloth is inserted to locally reinforce the annular groove of the joint, the number of reinforcing layers can be adjusted according to the bearing performance of an actual shell, and the reinforcing layers are required to be overlapped in a staggered mode, so that the overhead of impregnated fiber tows is reduced, and the local stress concentration is reduced.

The reinforcing layer in the joint annular groove is positioned between the spiral winding layer and the annular winding layer, the reinforcing angle mainly comprises 0 degree and +/-45 degrees, wherein 0 degree and +/-45 degrees adopt carbon cloth or prepreg cloth for reinforcing, 90-degree annular fiber winding outside the reinforcing layer compacts the 0 degree and +/-45 degrees reinforcing cloth through winding tension, and layering defects are avoided after forming.

In addition, the number of the yarn hanging pins on the joint in the step S1 can be calculated from the winding angle, and the following formula is specific:

wherein R is the joint radius of the hanging pin, b is the bandwidth of the dipped fiber tows, and alpha is the winding angle.

S5, solidifying and forming the shell

And (3) putting the shell wound in the step (S4) into a curing furnace for curing, and demolding after curing to form the large-opening composite shell with the embedded pin joint.

S6, processing a hanging yarn pin

And (5) cutting off the yarn hanging pin 4 of the protruding part of the composite material shell obtained in the step (S5) to finally obtain the large-opening fiber winding composite material shell with the embedded pin joint.

Example 1

S1, preparing embedded pin joint

Preparing a yarn hanging pin with the length of 38mm and phi 3mm, wherein the top cone angle of the yarn hanging pin is 30 degrees, the yarn hanging pin is subjected to R0.2 rounding treatment, the depth of a joint and a yarn hanging pin connecting hole is 2mm, the length of a joint partial annular groove is 33mm through the method (1), and a threaded connecting hole is formed at the end part of the joint and is connected with an external structure.

Wherein P is the set bearing pressure of the shell, D₁ is the outer diameter of the annular groove of the joint, 219mm is taken, S_comp is the interlayer shearing strength of the composite material, 70MPa is taken, K_safe is the safety coefficient, 1.3 is taken, and k is the effective contact area coefficient, and 0.75 is taken.

S2, elastic layer/joint/heat insulation layer bonding

Coating an adhesive on the outer surface of the joint 2, coating a nitrile rubber elastic layer with the thickness of 0.5mm, uniformly coating an adhesive on the bonding area of the heat insulation layer on the inner surface of the joint 2, and coating an ethylene propylene diene monomer rubber layer with the thickness of 2mm to form the joint with the heat insulation layer.

To increase the axial load capacity, the joint bond length to the insulation can be calculated to be 286mm according to equation (2).

Wherein S₁₂ is the shear strength between the heat insulating layer and the joint, 8MPa is taken, D₂ is the diameter of the joint bonding surface between the joint and the heat insulating layer, and 220mm is taken.

S3, preparing a winding core mold

The method comprises the steps of sleeving a sand core mould on a winding mandrel 6, positioning through a front positioning flange 7 and a rear positioning flange 8, sleeving a front joint and a rear joint with an elastic layer and a heat insulation layer on the front section and the rear section of the sand core mould, coating an ethylene propylene diene monomer heat insulation layer with the thickness of 2mm on the middle barrel section of the sand core mould, overlapping with the heat insulation layer dislocation of the front joint and the rear joint, overlapping the heat insulation layer with the overlapping length of 10mm, winding 2 layers of spiral and 2 layers of annular T800 carbon fibers on the surface of the composite body after the heat insulation layer is coated, shaping and restraining the heat insulation layer, putting the heat insulation layer into a curing furnace, presulfiding the heat insulation layer, vulcanizing at 110 ℃ and vulcanizing for 4h.

S4, winding the composite material

And (3) designing a shell winding layering scheme by adopting an isopolar hole mode, wherein the winding angle is 28.6 degrees, the winding angle is shown in a calculation formula (3), the impregnated fiber tows adopt a spiral and annular alternate winding mode, the spiral and annular winding thickness can be calculated by a formula (4) and a formula (5), 10 spiral layers and 7 annular layers are obtained, and the impregnated fiber tows are wound on the winding mandrel prepared in the step (S3) after the winding scheme is determined. Meanwhile, the joint annular groove is locally reinforced, the number of reinforcing layers can be adjusted according to the actual bearing performance of the shell, and staggered lap joints of 10mm are reserved between the reinforcing layers, so that fiber overhead is reduced, and local stress concentration is reduced. The reinforcing layer is positioned between the spiral winding layer and the circumferential winding layer, the reinforcing angle mainly comprises 0 degree and +/-45 degrees, wherein 0 degree and +/-45 degrees adopt carbon cloth or prepreg cloth for reinforcing, and 90 degrees circumferential fiber winding outside the reinforcing layer compacts the 0 degree and +/-45 degrees reinforcing cloth through winding tension.

Wherein d₁ is the diameter of the front pole hole, d₂ is the diameter of the rear pole hole, d_out is the outer diameter of the winding core mould barrel section, and d 230mm.

The spiral wound layer thickness h_α is determined by:

Wherein k_s is stress balance coefficient, 0.65 is taken, and the strength of sigma_fb fiber is taken as 5900MPa.

The hoop winding layer thickness h_θ is determined by:

In addition, the number of the joint pins in the step S1 can be calculated from the winding angle, specifically, as shown in the formula (6), and the number of the pins in the present invention is 98.

Wherein R is the joint radius of the hanging pin position, 109.5mm is taken, b is the bandwidth of the impregnated fiber tow, 8mm is taken, and alpha is the winding angle.

S5, solidifying and forming the shell

And (3) putting the shell wound in the step (S4) into a curing furnace for curing, and demolding after curing to form the large-opening composite shell with the embedded pin joint.

S6, pin machining

Cutting off the yarn hanging pins of the protruding part of the composite material shell obtained in the step S5 to finally obtain the large-opening fiber winding composite material shell with the embedded pin joint, realizing that the pressure bearing performance of the phi 230 shell is more than or equal to 24MPa, the fiber is stably wound and does not slide when the winding angle is 28.6 degrees, and the winding layer and the sealing surface (namely the inner surface of the joint) do not need secondary processing.

The invention has been described in detail in connection with the specific embodiments and exemplary examples thereof, but such description is not to be construed as limiting the invention. It will be understood by those skilled in the art that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, and these fall within the scope of the present invention. The scope of the invention is defined by the appended claims.

What is not described in detail in the present specification is a well known technology to those skilled in the art.

Claims (10)

1. The large-opening composite material shell bonding and forming method of the embedded pin joint is characterized by comprising the following steps of:

Preparing two groups of joints, namely a front joint and a rear joint, processing an annular groove on the outer wall of the joint, and embedding a yarn hanging pin in the annular groove area;

bonding an elastic layer with pin holes on the outer surface of the joint, and bonding a heat insulation layer on the inner surface of the joint to obtain the joint with the elastic layer and the heat insulation layer;

The method comprises the steps of sleeving a sand core mould on a winding mandrel and positioning, sleeving a front joint and a rear joint with an elastic layer and a heat insulation layer on the front section and the rear section of the sand core mould, coating the middle section of the sand core mould with the heat insulation layer, overlapping the heat insulation layer dislocation positions of the front joint and the rear joint, winding at least 1 layer of dry fiber on the outer surface of the combination, and presulfiding the heat insulation layer to obtain the winding mandrel;

Winding a gum dipping fiber tow on a winding mandrel, penetrating the gum dipping fiber tow by a yarn hanging pin in the winding process, and penetrating a reinforcing material to locally reinforce the annular groove of the joint;

And (3) curing the wound composite material shell, demolding after curing, and cutting off the yarn hanging pins of the protruding parts of the composite material shell to obtain the large-opening composite material shell with the embedded pin joints.

2. The method for bonding and forming the large-opening composite shell of the embedded pin joint according to claim 1, wherein the top of the yarn hanging pin is conical, and the top of the conical section is smoothly processed.

3. The method for bonding and molding a large-opening composite shell of a pre-buried pin joint according to claim 1, wherein the length L_comp of the annular groove on the joint is determined by the following formula:

wherein P is the set bearing pressure of the shell, D₁ is the outer diameter of the joint groove, S_comp is the interlayer shearing strength of the composite material, K_safe is the safety coefficient, and K is the effective contact area coefficient.

4. The method for bonding and forming a large-opening composite shell of a pre-buried pin joint according to claim 1, wherein the bonding length L of the joint and the heat insulation layer is determined by the following formula:

Wherein P is the set bearing pressure of the shell, K_safe is the safety coefficient, K is the effective contact area coefficient, S₁₂ is the shearing strength between the heat insulation layer and the joint, and D₂ is the diameter of the joint and the bonding surface of the heat insulation layer.

5. The method for bonding and forming the large-opening composite shell of the embedded pin joint as claimed in claim 1, wherein the impregnated fiber tows are wound on a winding mandrel in a spiral and annular alternating mode.

6. The method for bonding and forming a large-opening composite shell of a pre-buried pin joint according to claim 5, wherein the winding angle α of the spiral winding manner is determined by the following formula:

Wherein D₁ is the set diameter of the front pole hole, D₂ is the set diameter of the rear pole hole, and D_out is the outer diameter of the winding core mold barrel section.

7. The method of bonding and molding a large-opening composite shell of a pre-buried pin joint according to claim 5, wherein the thickness h_α of the spiral wound layer is determined by the following formula:

Wherein K_s is a stress balance coefficient, sigma_fb is fiber playing strength, D_out is winding mandrel barrel section outer diameter, P is set shell bearing pressure, K_safe is a safety coefficient, and alpha is winding angle.

8. The method for adhesively bonding large-opening composite shells of embedded pin joints according to claim 5, wherein the hoop winding layer thickness h_θ is determined by the following formula:

Wherein K_s is a stress balance coefficient, sigma_fb fiber exerts strength, D_out is the outer diameter of a winding core mold barrel section, P is a set shell bearing pressure, K_safe is a safety coefficient, and alpha is a winding angle.

9. The method for bonding and forming the large-opening composite shell of the embedded pin joint according to claim 5, wherein the reinforcing layer in the annular groove of the joint is positioned between the spiral winding layer and the annular winding layer, the reinforcing angle comprises 0 degrees and +/-45 degrees, and the 0 degrees and +/-45 degrees are reinforced by adopting carbon cloth or prepreg cloth.

10. The method for bonding and forming the large-opening composite shell of the embedded pin joint according to claim 1, wherein the number of the hanging pins on the joint is determined by the following formula:

wherein R is the joint radius of the hanging pin, b is the bandwidth of the dipped fiber tows, and alpha is the winding angle.