Light composite connecting skirt and forming method thereof

Abstract

The invention discloses a light composite connecting skirt and a forming method thereof. The connecting skirt comprises a connecting area on the upper portion, a force bearing area in the middle and a bonding area on the lower portion, and connecting holes are formed in the connecting area in the circumferential direction at intervals. An outer glass fiber layer is integrally laid on the outer surfaces of the connecting area, the force bearing area and the bonding area, and an outer skin is integrally laid on the inner surface of the outer glass fiber layer; ribs in grid arrangement are arranged on the inner surface of the outer skin corresponding to the bearing area; reinforcing blocks are arranged on the inner surface, corresponding to the connecting area, of the outer skin, the reinforcing blocks are embedded in gaps of the ribs arranged in a grid mode, and hollow cylindrical inserts are embedded in the positions, corresponding to the connecting holes, in the reinforcing blocks; filling blocks are arranged on the inner surface, corresponding to the bonding area, of the outer skin, and the filling blocks are embedded in gaps of the ribs arranged in a grid mode. On the basis of ensuring the overall structural strength and the load transmission coherence, not only is the mounting convenient, but also the maximum weight reduction is realized.

Description

Technical Field

[0001] The invention relates to the technical field of composite material paving and molding, in particular to a lightweight composite connecting skirt and a molding method thereof. Background Art

[0002] Since composite materials themselves are designable, the mechanical properties in different directions can be allocated according to the load requirements of the product's use environment, thereby giving full play to the characteristics of composite materials such as low density, high specific modulus and specific strength. Therefore, they are widely used in the aerospace field.

[0003] The solid rocket motor casing connecting skirt is an important load-bearing component in rocket components, as the connecting component between the solid rocket motor and the interstage. It needs to withstand the combined effects of multiple loads such as axial pressure and bending moment during the rocket flight. Early connecting skirts were generally made of metal materials such as aluminum alloy and titanium alloy, but with the development of technology, the rocket's demand for high thrust and lightweight has become more urgent, and the pursuit of lighter and more efficient connecting skirts has become the current goal.

[0004] The composite connecting skirt in the prior art has the following problems:

[0005] First, only the material replacement and size adjustment were performed on the basis of the metal connecting skirt, which failed to give full play to the designable mechanical properties of composite materials in all directions;

[0006] Second, the connecting skirt is usually made of carbon fiber prepreg alone, and the sandwich and grid weight reduction structure are not introduced, so the maximum weight reduction cannot be achieved. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention proposes a lightweight composite connecting skirt and a forming method thereof, which is not only easy to install but also achieves maximum weight reduction while ensuring the overall structural strength and load transfer continuity.

[0008] To achieve the above-mentioned purpose, the lightweight composite connecting skirt designed by the present invention is characterized in that it comprises an upper connecting area, a middle load-bearing area, and a lower bonding area, wherein the connecting area is provided with connecting holes arranged circumferentially and at intervals;

[0009] The outer surfaces of the connection area, the load-bearing area and the bonding area are entirely paved with an outer glass fiber layer, and the inner surface of the outer glass fiber layer is entirely paved with an outer skin;

[0010] The inner surface of the outer skin corresponding to the load-bearing area is provided with ribs arranged in a grid, and the two ends of the ribs extend to the connection area and the bonding area respectively;

[0011] A reinforcement block is provided on the inner surface of the outer skin corresponding to the connection area, and the reinforcement block is embedded in the gap of the grid-arranged ribs, the inner surface of the reinforcement block is flush with the inner surface of the ribs, and a hollow cylindrical insert is embedded in the position corresponding to the connection hole inside the reinforcement block, and the outer shape of the hollow cylindrical insert is arranged in an inverted T shape; the inner surface of the ribs and the reinforcement block is paved with an inner skin, and the inner surface of the inner skin is paved with an inner glass fiber layer;

[0012] The inner surface of the outer skin corresponding to the bonding area is provided with a filling block, and the filling block is embedded in the gap of the ribs arranged in a grid, the inner surface of the filling block is flush with the inner surface of the ribs, the inner surface of the ribs and the filling block is paved with an inner skin, and the inner surface of the inner skin is paved with an inner glass fiber layer;

[0013] The inner surface of the rib in the load-bearing area is flush with the inner surface of the glass fiber layer in the connecting area and the inner surface of the glass fiber layer in the bonding area.

[0014] Furthermore, the T-shaped large end surface of the hollow cylindrical insert is flush with the inner surface of the reinforcement block, and the T-shaped small end surface is flush with the outer surface of the outer skin.

[0015] Furthermore, the reinforcement block and the hollow cylindrical insert are connected by bonding and curing.

[0016] Furthermore, the reinforcement block is T700 carbon fiber, and the hollow cylindrical insert is titanium alloy.

[0017] Furthermore, the outer skin is carbon fiber prepreg, and the inner skin is carbon fiber prepreg.

[0018] Furthermore, the ribs are strip-shaped carbon fiber prepregs, and one end of the strip-shaped carbon fiber prepregs extends to the end of the bonding area, and the length of the strip-shaped carbon fiber prepregs decreases layer by layer in the laying direction from inside to outside.

[0019] Furthermore, the filling block is one or both of foam and plastic.

[0020] The present invention also provides a method for forming a lightweight composite connecting skirt, which is applicable to the above-mentioned lightweight composite connecting skirt, and the method is particularly characterized in that it comprises the following steps:

[0021] S1) a cylindrical sand core mold of a lightweight composite connecting skirt is provided, wherein the outer surface of the sand core mold corresponding to the load-bearing area of ​​the connecting skirt is provided with a boss and a groove, and the outer surface corresponding to the connecting area and the bonding area of ​​the connecting skirt is flush with the groove;

[0022] S2) laying several layers of inner glass fiber layers at positions corresponding to the connection skirt connection area and the bonding area on the outer surface of the sand core mold, and then laying an inner skin of corresponding size on the outer surface of the inner glass fiber layer, and pre-pressing it to a set height, and the set height after pre-pressing is lower than the outer surface of the boss in the load-bearing area;

[0023] S3) Filling ribs layer by layer inside the groove of the load-bearing area, and the two ends of the ribs extend to the upper surface of the inner skin of the connection area and the upper surface of the inner skin of the bonding area respectively, and the outer surface of the ribs is flush with the outer surface of the boss of the load-bearing area;

[0024] S4) pre-bonding and curing the reinforcement block and the hollow cylindrical insert, then filling the reinforcement block into the gap between the ribs in the connection area and the remaining area, cutting the outer surface of the reinforcement block so that the outer surface of the reinforcement block is flush with the outer surface of the rib; filling the filling block into the gap between the ribs in the bonding area and the remaining area, cutting the outer surface of the filling block so that the outer surface of the filling block is flush with the outer surface of the rib;

[0025] S5) laying the outer skin on the outer surfaces of the reinforcement blocks and ribs in the connection area, the outer surfaces of the bosses and ribs in the load-bearing area, and the outer surfaces of the filling blocks and ribs in the bonding area;

[0026] S6) laying an outer glass fiber layer on the outer surface of the outer skin as a whole;

[0027] S7) flushing the sand core mold with hot water to obtain a lightweight composite connecting skirt.

[0028] Furthermore, the method further comprises step S8), machining an outer glass fiber layer and an inner glass fiber layer to ensure the outer and inner surface dimensions of the lightweight composite connecting skirt.

[0029] The advantages of the present invention are:

[0030] 1. The present invention sets the entire outer layer of the connection skirt as a glass fiber layer + outer skin structure, and then divides the bottom end surface of the outer skin structure into three sections: a connection area, a load-bearing area, and a bonding area. A grid structure rib is set on the lower end surface of the load-bearing area as the main load-bearing structure, which is used to withstand various load conditions and ensure the stability of the overall structure; and the two free ends of the rib are extended to the connection area and the bonding area to ensure that the load transfer acting on the grid skirt has continuity and improve the overall load-bearing efficiency; then fill the rib gaps in the connection area with lightweight reinforcement blocks, and fill the rib gaps in the bonding area with lightweight filling blocks, and finally lay the inner skin + inner glass fiber layer on the inner layer of the connection area and the inner layer of the bonding area. Compared with the connection skirt without a grid structure that is simply laid with carbon fiber prepreg, the sandwich structure of the present invention not only ensures structural strength, but also achieves maximum weight reduction;

[0031] 2. The present invention arranges a hollow cylindrical insert around the connection hole of the reinforcement block in the connection area to enhance the local strength around the connection hole, and arranges the shape of the insert to be an inverted T-shaped structure to prevent the insert from being pulled out during loading;

[0032] The lightweight composite connecting skirt and the forming method thereof of the present invention adopt a partition setting in the length direction and a grid structure and a sandwich structure design in the thickness direction. On the basis of ensuring the overall structural strength and load transfer continuity, it is not only easy to install but also achieves maximum weight reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of a lightweight composite connecting skirt forming mold of the present invention;

[0034] Figure 2 It is a schematic diagram of the three-dimensional structure of the lightweight composite connecting skirt of the present invention;

[0035] Figure 3 It is a schematic diagram of the longitudinal section structure of the lightweight composite connecting skirt of the present invention;

[0036] Figure 4 for Figure 3 AA structural diagram in FIG.

[0037] Figure 5 for Figure 3 Schematic diagram of the BB structure;

[0038] Figure 6 for Figure 3 Schematic diagram of the bonding structure of the hollow cylindrical insert and the reinforcement block;

[0039] In the figure: outer glass fiber layer 1, outer skin 2, ribs 3, reinforcement blocks 4, hollow cylindrical inserts 5, inner skin 6, inner glass fiber layer 7, filling blocks 8. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0041] In the description of the present invention, it is necessary to understand that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention.

[0042] The invention discloses a light composite connecting skirt, comprising an upper connecting area, a middle load-bearing area and a lower bonding area, wherein the connecting area is provided with connecting holes which are arranged circumferentially and at intervals.

[0043] The outer surfaces of the connection area, the load-bearing area and the bonding area are entirely paved with an outer glass fiber layer 1, and the inner surface of the outer glass fiber layer 1 is entirely paved with an outer skin 2.

[0044] Specifically, the outer skin 2 is carbon fiber prepreg, which is used to obtain a flat mating surface.

[0045] The inner surface of the outer skin 2 corresponding to the load-bearing area is provided with ribs 3 arranged in a grid, and both ends of the ribs 3 extend to the connection area and the bonding area respectively. The load-bearing area serves as the main load-bearing structure.

[0046] Specifically, the ribs 3 are strip-shaped carbon fiber prepregs, and one end of the strip-shaped carbon fiber prepregs extends to the end of the bonding area. The strip-shaped carbon fiber prepregs decrease layer by layer in the laying length direction from the inside to the outside, ensuring that the load transfer acting on the mesh skirt is continuous and improving the overall load-bearing efficiency.

[0047] A reinforcement block 4 is provided on the inner surface of the outer skin 2 corresponding to the connection area, and the reinforcement block 4 is embedded in the gaps of the grid-arranged ribs 3. The inner surface of the reinforcement block 4 is flush with the inner surface of the ribs 3. A hollow cylindrical insert 5 is embedded in the reinforcement block 4 at the position corresponding to the connection hole, and the outer shape of the hollow cylindrical insert 5 is arranged in an inverted T shape; the inner surfaces of the ribs 3 and the reinforcement block 4 are paved with an inner skin 6, and the inner surface of the inner skin 6 is paved with an inner glass fiber layer 7.

[0048] Specifically, the inner skin 6 is carbon fiber prepreg.

[0049] Specifically, the reinforcement block 4 is made of T700 carbon fiber, and the hollow cylindrical insert 5 is made of titanium alloy.

[0050] Preferably, the T-shaped large end surface of the hollow cylindrical insert 5 is flush with the inner surface of the reinforcement block 4 , and the T-shaped small end surface is flush with the outer surface of the outer skin 2 .

[0051] The outer shape of the hollow cylindrical insert 5 is arranged in an inverted T shape to prevent the hollow cylindrical insert 5 from being pulled out during the loading process.

[0052] Preferably, the reinforcing block 4 and the hollow cylindrical insert 5 are connected by bonding and curing. During use, the reinforcing block 4 and the hollow cylindrical insert 5 are used together. The reinforcing block 4 and the hollow cylindrical insert 5 are bonded and cured in advance, and then the reinforcing block 4 is filled into the gap between the grid ribs 3 for connection with external components by bolts or the like.

[0053] A filling block 8 is provided on the inner surface of the outer skin 2 corresponding to the bonding area, and the filling block 8 is embedded in the gap between the ribs 3 arranged in a grid. The inner surface of the filling block 8 is flush with the inner surface of the rib 3. The inner surfaces of the ribs 3 and the filling block 8 are paved with an inner skin 6, and the inner surface of the inner skin 6 is paved with an inner glass fiber layer 7.

[0054] Specifically, the filling block 8 is made of one or both of foam and plastic.

[0055] The inner surface of the rib 3 in the load-bearing area is flush with the inner surface of the glass fiber layer 7 in the connecting area and the inner surface of the glass fiber layer 7 in the bonding area.

[0056] The present invention sets the entire outer layer of the connecting skirt as a glass fiber layer + outer skin structure, and then divides the bottom end surface of the outer skin structure into three sections: a connecting area, a load-bearing area, and a bonding area. A grid structured rib is set on the lower end surface of the load-bearing area as the main load-bearing structure for bearing various load conditions and ensuring the stability of the overall structure; and the two free ends of the rib are extended to the connecting area and the bonding area to ensure that the load transfer acting on the grid skirt is continuous and improve the overall load-bearing efficiency; and then the rib gaps in the connecting area are filled with lightweight reinforcement blocks, and the rib gaps in the bonding area are filled with lightweight filling blocks. Finally, an inner skin + an inner glass fiber layer are laid on the inner layer of the connecting area and the inner layer of the bonding area. Compared with a connecting skirt without a grid structure that is simply laid with carbon fiber prepreg, the sandwich structure of the present invention not only ensures structural strength, but also achieves maximum weight reduction.

[0057] In addition, the present invention arranges a hollow cylindrical insert around the connection hole of the connection zone reinforcement block to enhance the local strength around the connection hole, and arranges the insert shape to an inverted T-shaped structure to prevent the insert from being pulled out during loading.

[0058] The present invention also provides a method for forming a lightweight composite connecting skirt, which is applicable to the above-mentioned lightweight composite connecting skirt, and comprises the following steps:

[0059] S1) A cylindrical sand core mold of a lightweight composite connecting skirt is provided, wherein the outer surface of the sand core mold corresponding to the load-bearing area of ​​the connecting skirt is provided with a boss and a groove, and the outer surface corresponding to the connecting area and the bonding area of ​​the connecting skirt is flush with the groove.

[0060] S2) laying several layers of inner glass fiber layers 7 at positions corresponding to the connection skirt connection area and the bonding area on the outer surface of the sand core mold, and then laying an inner skin 6 of corresponding size on the outer surface of the inner glass fiber layer 7, and pre-pressing it to a set height, and the set height after pre-pressing is lower than the outer surface of the boss in the load-bearing area.

[0061] The inner surface of the inner glass fiber layer 7 is ensured to be smooth, which is convenient for subsequent assembly with other components. The inner glass fiber layer 7 laid at the same time can act as a sacrificial layer to ensure the inner surface size of the lightweight composite connecting skirt and protect the inner skin 6 of the inner layer.

[0062] S3) Fill the inner groove of the load-bearing area with ribs 3 layer by layer, and the two ends of the ribs 3 extend to the upper surface of the inner skin 6 in the connection area and the upper surface of the inner skin 6 in the bonding area respectively, and the outer surface of the ribs 3 is flush with the outer surface of the boss in the load-bearing area.

[0063] The laid strip ribs 3 serve as the main bearing structure, and are used to withstand various complex load conditions and ensure the stability of the overall structure.

[0064] S4) Pre-bond and cure the reinforcing block 4 and the hollow cylindrical insert 5, then fill the reinforcing block 4 into the gap between the ribs 3 in the connection area and the remaining area, cut the outer surface of the reinforcing block 4 so that the outer surface of the reinforcing block 4 is flush with the outer surface of the rib 3; fill the filling block 8 into the gap between the ribs 3 in the bonding area and the remaining area, cut the outer surface of the filling block 8 so that the outer surface of the filling block 8 is flush with the outer surface of the rib 3.

[0065] The gaps between the mesh ribs 3 are filled with filling blocks 8 to ensure that the outer skin 2 laid subsequently has a smooth appearance.

[0066] The reinforcing block 4 and the hollow cylindrical insert 5 are used together to fill the gaps in the mesh ribs 3, making it convenient to connect the connecting skirt to other components by means of bolts or the like, thereby enhancing the local strength of the structure.

[0067] S5) The outer skin 2 is integrally laid on the outer surfaces of the reinforcement blocks 4 and the ribs 3 in the connection area, the bosses and the ribs 3 in the load-bearing area, and the filling blocks 8 and the ribs 3 in the bonding area.

[0068] Specifically, the outer skin 2 is laid with carbon fiber prepreg, and the entire structure forms a sandwich-like core structure.

[0069] S6) Laying the outer glass fiber layer 1 on the outer surface of the outer skin 2 as a whole.

[0070] S7) flushing the sand core mold with hot water to obtain a lightweight composite connecting skirt.

[0071] Preferably, the method further comprises step S8), machining the outer glass fiber layer 1 and the inner glass fiber layer 7 to ensure the outer and inner surface dimensions of the lightweight composite connecting skirt.

[0072] The lightweight composite connecting skirt and the forming method thereof of the present invention adopt a partition setting in the length direction and a grid structure and a sandwich structure design in the thickness direction. On the basis of ensuring the overall structural strength and load transfer continuity, it is not only easy to install but also achieves maximum weight reduction.

[0073] The above are preferred implementation modes of the invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A lightweight composite connecting skirt, characterized in that: It comprises an upper connection area, a middle load-bearing area, and a lower bonding area, wherein the connection area is provided with connection holes arranged circumferentially and at intervals; The outer surfaces of the connection area, the load-bearing area and the bonding area are entirely paved with an outer glass fiber layer (1), and the inner surface of the outer glass fiber layer (1) is entirely paved with an outer skin (2); The inner surface of the outer skin (2) corresponding to the load-bearing area is provided with ribs (3) arranged in a grid, and the two ends of the ribs (3) extend to the connection area and the bonding area respectively; A reinforcing block (4) is arranged on the inner surface of the outer skin (2) corresponding to the connection area, and the reinforcing block (4) is embedded in the gap between the ribs (3) arranged in a grid, the inner surface of the reinforcing block (4) is flush with the inner surface of the ribs (3), and a hollow cylindrical insert (5) is embedded in the position corresponding to the connection hole inside the reinforcing block (4), and the outer shape of the hollow cylindrical insert (5) is arranged in an inverted T shape; the inner surfaces of the ribs (3) and the reinforcing block (4) are paved with an inner skin (6), and the inner surface of the inner skin (6) is paved with an inner glass fiber layer (7); A filling block (8) is provided on the inner surface of the outer skin (2) corresponding to the bonding area, and the filling block (8) is embedded in the gap between the ribs (3) arranged in a grid, and the inner surface of the filling block (8) is flush with the inner surface of the ribs (3), the inner surfaces of the ribs (3) and the filling block (8) are paved with an inner skin (6), and the inner surface of the inner skin (6) is paved with an inner glass fiber layer (7); The inner surface of the rib (3) in the load-bearing area is flush with the inner surface of the glass fiber layer (7) in the connection area and the inner surface of the glass fiber layer (7) in the bonding area.

2. The lightweight composite connecting skirt according to claim 1, characterized in that: The T-shaped large end surface of the hollow cylindrical insert (5) is flush with the inner surface of the reinforcement block (4), and the T-shaped small end surface is flush with the outer surface of the outer skin (2).

3. The lightweight composite connecting skirt according to claim 2, characterized in that: The reinforcement block (4) and the hollow cylindrical insert (5) are connected by bonding and curing.

4. The lightweight composite connecting skirt according to claim 3, characterized in that: The reinforcing block (4) is made of T700 carbon fiber, and the hollow cylindrical insert (5) is made of titanium alloy.

5. The lightweight composite connecting skirt according to claim 1, characterized in that: The outer skin (2) is a carbon fiber prepreg, and the inner skin (6) is a carbon fiber prepreg.

6. The lightweight composite connecting skirt according to claim 5, characterized in that: The ribs (3) are strip-shaped carbon fiber prepregs, and one end of the strip-shaped carbon fiber prepregs extends to the end of the bonding area, and the length of the strip-shaped carbon fiber prepregs decreases layer by layer in the laying direction from the inside to the outside.

7. The lightweight composite connecting skirt according to claim 6, characterized in that: The filling block (8) is one or both of foam and plastic.

8. A method for forming a lightweight composite connecting skirt, applicable to the lightweight composite connecting skirt as claimed in any one of claims 1 to 7, characterized in that: The steps include: S1) a cylindrical sand core mold of a lightweight composite connecting skirt is provided, wherein the outer surface of the sand core mold corresponding to the load-bearing area of ​​the connecting skirt is provided with a boss and a groove, and the outer surface corresponding to the connecting area and the bonding area of ​​the connecting skirt is flush with the groove; S2) laying several layers of inner glass fiber layers (7) at positions corresponding to the connection skirt connection area and the bonding area on the outer surface of the sand core mold, and then laying an inner skin (6) of corresponding size on the outer surface of the inner glass fiber layer (7), and pre-pressing it to a set height, and the set height after pre-pressing is lower than the outer surface of the boss in the load-bearing area; S3) Filling ribs (3) layer by layer inside the groove of the load-bearing area, with the two ends of the ribs (3) respectively extending to the upper surface of the inner skin (6) of the connection area and the upper surface of the inner skin (6) of the bonding area, and the outer surface of the ribs (3) being flush with the outer surface of the boss of the load-bearing area; S4) pre-bonding and curing the reinforcing block (4) and the hollow cylindrical insert (5), then filling the reinforcing block (4) into the gap between the ribs (3) in the connection area and the remaining area, cutting the outer surface of the reinforcing block (4) so ​​that the outer surface of the reinforcing block (4) is flush with the outer surface of the ribs (3); filling the filling block (8) into the gap between the ribs (3) in the bonding area and the remaining area, cutting the outer surface of the filling block (8) so that the outer surface of the filling block (8) is flush with the outer surface of the ribs (3); S5) integrally laying the outer skin (2) on the outer surfaces of the reinforcement block (4) and the ribs (3) in the connection area, the outer surfaces of the boss and the ribs (3) in the load-bearing area, and the outer surfaces of the filling block (8) and the ribs (3) in the bonding area; S6) laying an outer glass fiber layer (1) on the outer surface of the outer skin (2); S7) flushing the sand core mold with hot water to obtain a lightweight composite connecting skirt.

9. The method for forming a lightweight composite connecting skirt according to claim 8, characterized in that: The method further comprises step S8), machining an outer glass fiber layer (1) and an inner glass fiber layer (7) to ensure the outer and inner surface dimensions of the lightweight composite connecting skirt.

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