Solid rocket engine composite material skirt connecting structure and forming method thereof

Abstract

The application discloses a solid rocket engine composite skirt connecting structure and a forming method thereof, and the connecting structure comprises a composite skirt, a skirt hole reinforcing ring, a connected cabin section and a connecting piece; the composite skirt and the skirt hole reinforcing ring are integrally formed; the rear end of the composite skirt and the skirt hole reinforcing ring is connected with the connected cabin section through the connecting piece; the connected cabin section is an L-shaped nested inner lap joint structure, which plays a butt joint limiting and bearing function; and the front end thickness transition section of the composite skirt is connected with a fiber winding structure layer of a combustion chamber shell. Compared with a traditional metal skirt connecting structure, the application has obvious weight reduction effect; compared with a traditional composite material skirt hinge block connecting structure, the application has a simpler connecting mode, guarantees the fiber continuity of the composite material skirt connecting area, adopts the skirt hole reinforcing ring as a metal reinforcing piece, and solves the problems of insufficient in-plane shear stiffness and strength of the composite material and damage of the hole position. The application has simple structure and forming process, high maturity and low cost.

Description

Technical Field

[0001] This invention relates to the field of solid rocket motors, and more specifically to a composite material skirt connection structure for solid rocket motors and its molding method. Background Technology

[0002] With the continuous development of materials science and molding technology, fiber-reinforced composite materials have gradually replaced traditional metal materials and become the main material for solid rocket motor casings due to their advantages of high specific strength, high specific modulus, and lightweight properties. The skirt, as the carrier connecting the combustion chamber casing of a solid rocket motor to other sections, is a crucial component. During engine operation, the connection points are often subjected to the combined effects of complex loads such as bending moment, axial compression, axial tension, shear, and temperature shock, making the reliability of the connection structure paramount. Generally, the axial compression load of an engine is much greater than the axial tension load, and the bending moment load generated by lateral overload during high engine maneuvers is also a major factor contributing to engine disintegration in flight. Therefore, the engine's load conditions must be comprehensively considered in the skirt connection design.

[0003] Composite material skirts offer significant weight reduction compared to traditional metal skirts, effectively improving the engine's mass-to-weight ratio. However, due to the isotropic nature of composite materials, low shear stiffness, and low shear strength, as well as manufacturing defects such as discontinuous thickness of column sections and connecting sections, and ply overlap in traditional composite material skirts, the actual performance of composite material skirts differs greatly from theoretical designs, and connection design is difficult. Therefore, this invention patent proposes a composite material skirt connection structure and its molding method for solid rocket motors, comprehensively considering the above-mentioned problems and effectively improving the reliability of the composite material skirt connection structure. Summary of the Invention

[0004] The purpose of this invention is to provide a composite material skirt connection structure for solid rocket motors and its molding method, thereby solving the problems of difficult molding of composite material skirts, complex connection structures, low structural strength, and low reliability of connection structures. The specific technical solution is as follows:

[0005] This invention provides a composite material skirt connection structure for a solid rocket motor. The connection structure includes a composite material skirt, a skirt hole reinforcing ring, a connected section, and a connector. The composite material skirt and the skirt hole reinforcing ring are integrally formed. The rear ends of the composite material skirt and the skirt hole reinforcing ring are connected to the connected section via the connector. The connected section is an L-shaped nested overlapping structure, serving as a docking limit and load-bearing function. The front thickness transition section of the composite material skirt is connected to the fiber-wound structure layer of the combustion chamber shell.

[0006] Furthermore, the connector is any one of countersunk screws, pan head screws, pan head screws, and load-bearing structural pins.

[0007] Furthermore, when the connector is a load-bearing structural pin, the connecting hole of the connected compartment is a normal hole with a 1-2mm margin at the bottom for limiting the position; when the connector is a countersunk screw, pan head screw, or pan head screw, the connecting hole of the connected compartment is a threaded through hole.

[0008] Furthermore, the front thickness transition section of the composite skirt and the fiber-wound structural layer of the combustion chamber shell are obtained through the following connection method:

[0009] S1. Apply nitrile rubber-based adhesive interface glue to the inner surface of the mating position, and then connect the thickness transition section at the front end of the composite skirt to the fiber winding structure layer of the combustion chamber shell, wherein the thickness of the adhesive layer is greater than or equal to 0.3mm;

[0010] S2. Apply nitrile rubber-based adhesive interface glue to the upper surface of the mating position and wrap the fixing layer of the composite skirt.

[0011] Furthermore, the fixing layer is composed of circumferentially wound fibers and an axially reinforcing layer, the proportion of which is adjusted according to the axial load requirements.

[0012] Furthermore, the composite material skirt is laid up according to the blanket curve method, and the ±45° layup ratio is not less than 50%; the skirt hole reinforcing ring (2) is staggered with double rows of holes under severe load.

[0013] This invention also provides a method for molding a composite material skirt connection structure for a solid rocket motor. The method involves integrally molding a composite material skirt and a skirt hole reinforcing ring. The specific steps are as follows: take a male mold and a female mold, lay fiber layers layer by layer on the surface of the male mold, with smooth transition surfaces, stacking from the first layer to the nth layer, where n is an integer greater than or equal to 2, and insert a thickness transition layer between the two consecutive layers. After laying, assemble the skirt hole reinforcing ring blank, and after assembly, close the mold with the female mold. High-temperature curing and molding are then performed to obtain an integrally molded composite material skirt blank and skirt hole reinforcing ring blank.

[0014] Furthermore, the integrally formed composite material skirt blank and skirt hole reinforcing ring blank are further machined to obtain an integrally formed composite material skirt and skirt hole reinforcing ring.

[0015] Furthermore, the thermal expansion coefficients of the male and female molds are matched with those of the composite skirt; the thermal expansion coefficient of the skirt hole reinforcing ring blank is higher than that of the composite skirt blank, and the two achieve an interference fit during the process of cooling to room temperature after high-temperature curing, which is used to improve the connection reliability between the two.

[0016] Furthermore, the skirt hole reinforcing ring blank is made of alloy steel or titanium alloy. Before assembly, the mating surfaces of the skirt hole reinforcing ring blank are sandblasted and coated with interface adhesive with a thickness of ≥0.2mm. During assembly, it is heat-insulated at 60℃. The female mold includes 3 to 6 circumferential lobes to achieve uniform pressure distribution during the curing process.

[0017] The advantages of this invention compared to the prior art are:

[0018] (1) The present invention has a significant weight reduction effect compared with the traditional metal skirt connection structure, and the connection method is simpler compared with the traditional composite material skirt hinge block connection structure.

[0019] (2) The present invention has high structural reliability. The design ensures the fiber continuity in the composite material skirt connection area and uses the skirt hole reinforcing ring as a metal reinforcement to solve the problems of insufficient in-plane shear stiffness and strength of composite materials and easy damage at the hole position.

[0020] (3) The present invention has high adaptability. The radial connection of screws can be applied to engines of various projectile diameters, which solves the connection problem of small projectile diameter composite shells.

[0021] (4) The present invention has a simple structure and molding process, is easy to install and assemble, has a high degree of process maturity, low cost and good economic efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the composite material skirt connection structure of the solid rocket motor of the present invention.

[0023] Figure 2 This is a schematic diagram of the preparation of the composite material skirt of the solid rocket motor of the present invention, which is assembled with a metal skirt hole reinforcing ring.

[0024] Figure 3 This is a schematic diagram of the integrated molding method of the solid rocket motor composite material skirt and skirt hole reinforcing ring of the present invention.

[0025] The attached figures are labeled as follows: 1. Composite material skirt; 2. Skirt hole reinforcing ring; 3. Connected compartment; 4. Connector; 5. Female mold; 6. Skirt hole reinforcing ring blank; 7. Male mold; 8. Composite material skirt blank. Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0028] Figure 1 This invention provides a connection structure for a composite material skirt of a solid rocket motor. The connection structure includes a composite material skirt 1, a skirt hole reinforcing ring 2, a connected section 3, and a connector 4. The composite material skirt 1 and the skirt hole reinforcing ring 2 are integrally formed. The rear ends of the composite material skirt 1 and the skirt hole reinforcing ring 2 are connected to the connected section 3 via the connector 4. The connected section 3 has an L-shaped nested overlapping structure, serving as a docking limit and load-bearing function. The front thickness transition section of the composite material skirt 1 is connected to the fiber-wound structure layer of the combustion chamber shell.

[0029] The thickness H of the composite material skirt 1 is ≥ k*(2π*R / (2π*Rn*d))*T / (2π*R*σ). C ), where k is the design safety factor, k≥2; T is the circumferential tensile force or axial tensile force; R is the outer diameter of the composite skirt; n is the number of circumferential openings; d is the hole diameter, d is 0.5H~1.5H, σ C σ is the axial tensile strength of the composite skirt φ Or circumferential tensile strength σ θ The thickness h of the skirt hole reinforcing ring is 0.15H to 0.35H; the distance e from the hole to the end face is ≥ T / (2*(Hh)*τ). c The arc length w between the openings is greater than or equal to d + [T / (σ)]. θ *(Hh))];The overlapping length of the skirt hole reinforcing ring l≥2e;The axial stiffness E φ Circumferential stiffness E θ In-plane shear stiffness G, axial tensile strength σ φ Circumferential tensile strength σ θ In-plane shear strength τ c Based on the equivalent stiffness theory of composite materials, it is calculated that the skirt hole reinforcing ring is staggered with two rows of holes under severe loads, where the row spacing B ≥ 2d.

[0030] When the connector 4 is a load-bearing structural pin, the connecting hole of the connected compartment 3 is a standard hole with a 1-2mm margin at the bottom for positioning; when the connector 4 is a countersunk screw, pan head screw, or pan head screw, the connecting hole of the connected compartment 3 is a threaded through hole. In this embodiment, a countersunk screw is selected as the connecting structure, and the corresponding connecting hole of the connecting compartment is an M8 threaded through hole.

[0031] The connection method between the front thickness transition section of the composite skirt 1 and the fiber-wound structure layer of the combustion chamber shell is as follows: S1, apply a nitrile rubber-based adhesive interface to the inner surface of the mating position, and then connect the front thickness transition section of the composite skirt 1 and the fiber-wound structure layer of the combustion chamber shell, wherein the adhesive layer thickness is greater than or equal to 0.3 mm; S2, apply a nitrile rubber-based adhesive interface to the upper surface of the mating position, and then perform the fixing layer winding of the composite skirt 1. The fixing layer consists of circumferentially wound fibers and an axially reinforcing layer, and the proportion of the axially reinforcing layer is adjusted according to the axial load requirements.

[0032] In this embodiment, the adhesive layer thickness is 0.3 mm, the skirt fixing layer is composed of circumferentially wound fibers and axially reinforcing layers, the circumferential single layer thickness is 0.2 mm, and a 0.4 mm thick carbon fiber axially reinforcing cloth is sandwiched between every two circumferentially wound layers, with a total thickness of 2.4 mm.

[0033] like Figure 2 The schematic diagram shows the fabrication process of a composite material skirt for a solid rocket motor, consisting of a composite material skirt with a metal skirt hole reinforcement ring. In this embodiment, the specific design methods for the layup, thickness, and openings of the composite material skirt 1 are as follows:

[0034] The skirt material is made of T800 grade carbon fiber prepreg with a fiber direction tensile strength of 2600MPa. The layup is designed according to the blanket curve method, with a layup ratio of less than 55% at ±45°, less than 30% at 0°, and less than 15% at 90°. The layup sequence is [90 / ±45 / 0 / ±45 / 0]n.

[0035] The axial stiffness E φ Circumferential stiffness E θ In-plane shear stiffness G, axial tensile strength σ φ Circumferential tensile strength σ θ In-plane shear strength τ c Calculated based on the equivalent stiffness theory of composite materials;

[0036] Skirt thickness H≥k*(2π*R / (2π*Rn*d))*T / (2π*R*σ) CGiven n=24, d=8mm, k=2, R=250mm, T=500kN, based on the axial tensile load calculation results and considering the process conditions, the skirt thickness H is taken as 4mm; the thickness h of the skirt hole reinforcing ring 2 is 1mm; the distance e from the hole to the end face is ≥T / (2n*(Hh)*τ). c When n is 16mm, the arc length w between openings is satisfied when n is 24, which satisfies the condition w ≥ d + [T / (n*σ). θ *(Hh))], the overlap length of the skirt hole reinforcement ring is l=30mm.

[0037] like Figure 3 A schematic diagram of the integrated molding method for a solid rocket motor composite material skirt and skirt hole reinforcing ring is shown. This invention also provides a molding method for a solid rocket motor composite material skirt connection structure, wherein the method involves the integrated molding of a composite material skirt 1 and a skirt hole reinforcing ring 2. The specific steps are as follows:

[0038] Take the male mold 7 and female mold 5, and lay fiber layers layer by layer on the surface of the male mold 7, with smooth transition surfaces, stacking from the first layer (lay1) to the nth layer (layn). A thickness transition layer is sandwiched between the two continuous lay-up parts. After laying, assemble the skirt hole reinforcing ring blank 6. After assembly, assemble with the female mold 5 to close the mold, and then perform high-temperature curing and compression molding to obtain an integrally formed composite material skirt blank 8 and skirt hole reinforcing ring blank 6. In this embodiment, the mold material is selected as glass fiber / epoxy resin composite material.

[0039] The integrally formed composite material skirt blank 8 and skirt hole reinforcing ring blank 6 are further machined to obtain an integrally formed composite material skirt 1 and skirt hole reinforcing ring 2.

[0040] The thermal expansion coefficients of the male mold 7 and female mold 5 are matched with those of the composite skirt 1; the thermal expansion coefficient of the skirt hole reinforcing ring blank 6 is higher than that of the composite skirt blank 8. After high-temperature curing, the two achieve an interference fit during the cooling process to room temperature, which is used to improve the connection reliability between the two.

[0041] The skirt-hole reinforcing ring blank 6 is made of alloy steel or titanium alloy. Before assembly, the mating surfaces of the skirt-hole reinforcing ring blank 6 are sandblasted and coated with interface adhesive with a thickness of ≥0.2mm. During assembly, it is heat-treated at 60℃. In this embodiment, the skirt-hole reinforcing ring uses a TC4 titanium forged ring, and the interface adhesive thickness is 0.2mm.

[0042] The female mold 5 comprises 3 to 6 circumferential segments to achieve uniform pressure distribution during the curing process. In this embodiment, the female mold consists of 4 circumferential segments.

[0043] The contents not described in detail in this specification are prior art known to those skilled in the art. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A composite material skirt connection structure for a solid rocket motor, characterized in that, The connecting structure includes a composite material skirt (1), a skirt hole reinforcing ring (2), a connected compartment (3), and a connector (4); wherein, The composite material skirt (1) and the skirt hole reinforcing ring (2) are integrally formed; The rear end of the composite material skirt (1) and the skirt hole reinforcing ring (2) is connected to the connected compartment (3) via a connector (4); The connected compartment (3) is an L-shaped nested overlapping structure, which serves as a docking limit and load-bearing function; The front thickness transition section of the composite skirt (1) is connected to the fiber-wound structure layer of the combustion chamber shell. The thickness H of the composite skirt (1) is greater than or equal to k*(2π*R / (2π*Rn*d))*T / (2π*R*σ). C ), where k is the design safety factor, k≥2; T is the circumferential tensile force or axial tensile force; R is the outer diameter of the composite skirt; n is the number of circumferential openings; d is the hole diameter, d is 0.5H~1.5H, σ C σ is the axial tensile strength of the composite skirt φ Or circumferential tensile strength σ θ The thickness h of the skirt hole reinforcing ring (2) is 0.15H to 0.35H.

2. The composite material skirt connection structure for a solid rocket motor according to claim 1, characterized in that, The connector (4) is any one of countersunk screws, pan head screws, pan head screws and load-bearing structure pins.

3. The composite material skirt connection structure for a solid rocket motor according to claim 2, characterized in that, When the connector (4) is a load-bearing structure pin, the connection hole of the connected compartment is a normal hole and the bottom is reserved with 1-2mm for limiting; when the connector (4) is a countersunk screw, pan head screw or pan head screw, the connection hole of the connected compartment is a threaded through hole.

4. The composite material skirt connection structure for a solid rocket motor according to claim 1, characterized in that, The front thickness transition section of the composite skirt (1) and the fiber-wound structure layer of the combustion chamber shell are obtained by the following connection method: S1. Apply nitrile rubber-based adhesive interface glue to the inner surface of the docking position, and then connect the front thickness transition section of the composite skirt (1) to the fiber winding structure layer of the combustion chamber shell, wherein the thickness of the adhesive layer is greater than or equal to 0.3 mm. S2. Apply nitrile rubber-based adhesive interface glue to the upper surface of the docking position and wrap the fixing layer of the composite skirt (1).

5. The composite material skirt connection structure for a solid rocket motor according to claim 4, characterized in that, The fixing layer is composed of circumferentially wound fibers and an axially reinforcing layer, the proportion of which is adjusted according to the axial load requirements.

6. The composite material skirt connection structure for a solid rocket motor according to claim 1, characterized in that, The composite skirt (1) is laid up according to the blanket curve method, and the layup ratio of ±45° is not less than 50%; the skirt hole reinforcing ring (2) is staggered with double rows of holes when the load is severe.

7. The molding method for a composite material skirt connection structure of a solid rocket motor according to claim 1, characterized in that, It is integrally formed with a composite material skirt (1) and a skirt hole reinforcing ring (2), including the following steps: Take the male mold (7) and female mold (5), and lay fiber layers on the surface of the male mold (7) one by one. The transition position is smooth. Stack from the first layer to the nth layer, where n is an integer greater than or equal to 2. A thickness transition layer is sandwiched between the two continuous lay-up parts. After laying, assemble the skirt hole reinforcing ring blank (6). After assembly, cooperate with the female mold (5) to close the mold. High temperature curing molding is used to obtain the integrally formed composite material skirt blank (8) and skirt hole reinforcing ring blank (6).

8. The method for forming a composite material skirt connection structure for a solid rocket motor according to claim 7, characterized in that, The integrally formed composite material skirt blank (8) and skirt hole reinforcing ring blank (6) are further machined to obtain an integrally formed composite material skirt (1) and skirt hole reinforcing ring (2).

9. A method for forming a composite material skirt connection structure for a solid rocket motor according to claim 8, characterized in that, The thermal expansion coefficients of the male mold (7) and female mold (5) are matched with the thermal expansion coefficient of the composite skirt (1); the thermal expansion coefficient of the skirt hole reinforcing ring blank (6) is higher than that of the composite skirt blank (8), and the two achieve an interference fit during the process of high temperature curing and cooling to room temperature.

10. A method for forming a composite material skirt connection structure for a solid rocket motor according to claim 7, characterized in that, The skirt hole reinforcing ring blank (6) is made of alloy steel or titanium alloy. Before assembly, the mating surfaces of the skirt hole reinforcing ring blank (6) are sandblasted and coated with interface adhesive. The thickness of the interface adhesive is greater than or equal to 0.2 mm. During assembly, it is heat-insulated at 60°C. The female mold (5) includes 3 to 6 circumferential petals to achieve uniform pressure distribution during the curing process.

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