Sand core mold and method suitable for small-diameter large-length-diameter-ratio composite shell

Abstract

According to the sand core mold suitable for the composite material shell with the small diameter and the large length-diameter ratio, aiming at the stress characteristics of a core shaft when the composite material shell with the small diameter is formed in the prior art, a split type core mold structure is improved, and an integrated structure of the core shaft, the end socket sand core and the cylinder section sand core is adopted; through structural optimization, the sand core mold can smoothly finish winding forming of a small-diameter composite material shell. During mold pulling, the sand core mold does not need to be directly pulled out of the composite material shell, hot water only needs to be injected into the mandrel through the pipe connecting nozzle, the end socket sand core and the cylinder section sand core can be gradually dissolved, and the end socket sand core and the cylinder section sand core are directly dissolved into mortar to flow out of the composite material shell. By means of the structure, the mold pulling efficiency is greatly improved, damage to the composite material shell is avoided, the mold pulling device is suitable for forming of the composite material shell with the small diameter and the large length-diameter ratio, the applicability and the working efficiency are improved, and the mold pulling device is suitable for industrial large-scale use and popularization.

Description

Technical Field

[0001] The invention belongs to the field of solid rocket engine manufacturing, and particularly relates to a sand core mold and a method suitable for a small-diameter and large-aspect-ratio composite material casing. Background Art

[0002] At present, composite materials are widely used in making the shells of solid rocket engines, and sand core molds are needed to make composite material shells. Existing sand core molds mostly adopt a split-flap structure. For small-diameter composite material shells, the split-flap sand core mold further loses its advantage. The reason is that the core shaft, one of the components of the sand core mold, has to bear the weight of the entire core mold during the use of the core mold, thereby causing flexural deformation. If the flexural deformation is large and accompanied by the rotational motion of the winding, the entire core mold will vibrate, resulting in the inability to carry out winding.

[0003] Therefore, the core shaft of the sand core mold must have a certain diameter to ensure sufficient rigidity. For a small-diameter composite shell, the diameter is equivalent to the diameter required for the core shaft of the sand core mold to ensure sufficient rigidity. The sand core will completely fill the space between the composite shell and the core shaft, resulting in an increase in the contact area, which makes it very difficult to pull out the core shaft. In general, the applicability of the existing split-flap sand core mold to a small-diameter composite shell becomes poor. Summary of the invention

[0004] The purpose of the present invention is to provide a sand core mold and a molding method suitable for a small-diameter and large-aspect-ratio composite material shell, so as to solve the problem that the sand core mold in the prior art has poor applicability and is difficult to pull out the core shaft when applied to a small-diameter composite material shell.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0006] A sand core mold suitable for a composite material shell with a small diameter and a large aspect ratio, comprising a barrel sand core, both ends of the barrel sand core are fixedly connected to a head sand core, a core shaft is penetrated into the barrel sand core, a plurality of barrel sand core longitudinal ribs extending along the length direction are evenly distributed on the inner wall of the barrel sand core; the inner wall of the head sand core is provided with head sand core longitudinal ribs corresponding to the barrel sand core longitudinal ribs one by one;

[0007] Both left and right ends of the mandrel extend out of the barrel sand core, and the mandrel is provided with sand consolidation grooves in the same number as the longitudinal ribs of the barrel sand core along the length direction, and the specifications of the sand consolidation grooves match the longitudinal ribs of the barrel sand core; a plurality of through holes are evenly provided between two adjacent sand consolidation grooves in the middle of the mandrel along the length direction;

[0008] The mandrel is a hollow structure, and both ends of the mandrel are connected with clamping parts that can be connected to an external clamping device; the clamping part has a water injection channel in the interior thereof that is connected to the interior of the mandrel;

[0009] The end surface of the clamping part is also connected with a connecting nozzle which is in sealing communication with the water injection channel.

[0010] The present invention also has the following features:

[0011] Furthermore, it also includes two fixing screw sleeves; the left and right ends of the mandrel extending out of the barrel sand core serve as connecting parts;

[0012] The fixing screw sleeve is provided with an internal thread, and the connecting part of the core shaft is provided with an external thread matching the internal thread of the fixing screw sleeve.

[0013] A barrel segment sand core forming mold, the barrel segment sand core forming mold is used to form the barrel segment sand core, comprising a barrel segment sand core female mold and an inner liner;

[0014] The inner sleeve includes a first connecting sleeve and a plurality of cover plates, wherein the first connecting sleeve can be fixedly sleeved on the connecting portion on the left side of the mandrel; the shape of the cover plate matches the shape of the area between two adjacent sand consolidation grooves on the mandrel, and the plurality of cover plates correspond one by one to seal and cover the area between two adjacent sand consolidation grooves on the mandrel;

[0015] The barrel section sand core female mold is cylindrical, the inner diameter of the barrel section sand core female mold matches the outer diameter of the barrel section sand core, and the length of the barrel section sand core female mold is equal to the barrel section sand core;

[0016] The first connecting sleeve of the inner sleeve is sleeved with a second connecting sleeve, the barrel section sand core female mold is sleeved on the mandrel through the second connecting sleeve, and the shape of the area formed between the barrel section sand core female mold and the mandrel is the same as the shape of the barrel section sand core.

[0017] Furthermore, it also includes a first sealing cover plate, a first sealing pressure ring and a second sealing cover plate;

[0018] The first sealing cover plate is detachably mounted on the clamping portion on the left side of the mandrel, and is used to seal the gap between the left side of the barrel sand core female mold and the mandrel;

[0019] The first sealing pressure ring and the second sealing cover plate are detachably mounted on the right connecting portion of the core shaft in sequence, and are used to seal the gap between the right side of the barrel section sand core female mold and the core shaft.

[0020] A head sand core forming mold, the head sand core forming mold is used to form the head sand core, characterized in that it includes a head sand core male mold and a head sand core female mold;

[0021] The shape of the area formed between the male mold of the sealing head sand core and the female mold of the sealing head sand core is the same as that of the sealing head sand core.

[0022] Furthermore, it also includes a second sealing pressure ring and a third sealing cover plate;

[0023] The head sand core positive mold is a cylindrical structure, and a plurality of grooves for forming longitudinal ribs of the head sand core are provided on the head sand core positive mold for forming the head sand core; a connector is coaxially connected to the front of the head sand core positive mold;

[0024] The female mold of the end cap sand core comprises a forming part and a connecting part, and the plug-in piece of the male mold of the end cap sand core can be plugged into the connecting part of the female mold of the end cap sand core in a sealing manner; the shape of the area formed between the inner wall of the forming part of the female mold of the end cap sand core and the male mold of the end cap sand core is the same as that of the end cap sand core;

[0025] The second sealing pressure ring and the third sealing cover plate are detachably mounted on the head sand core positive mold from the rear of the head sand core positive mold in sequence; the second sealing pressure ring is used to seal the gap between the head sand core positive mold and the sealing head sand core female mold.

[0026] A method for forming a sand core mold suitable for a composite material shell with a small diameter and a large aspect ratio, the method is based on the above-mentioned barrel sand core forming mold and head sand core forming mold, and comprises the following steps:

[0027] Step 1: Apply a release agent to the parts where the male and female molds of the end cap sand core are in contact with the mortar, and inject the mortar into the area between the male and female molds of the end cap sand core and compact it;

[0028] Step 2: Install and fix the second sealing pressure ring and the third sealing cover plate, and after the mortar is cured, remove the second sealing pressure ring, the third sealing cover plate, the male mold of the end cap sand core, and the female mold of the end cap sand core to form the end cap sand core;

[0029] Repeat the above operation to make two head sand cores;

[0030] Step 3, applying a release agent to the portion where the barrel section sand core female mold contacts the mortar, and installing the inner liner, the second connecting sleeve, the barrel section sand core female mold and the first sealing cover plate on the mandrel in sequence;

[0031] Step 4, inject mortar into the area between the barrel section sand core female mold and the mandrel and tamp it, then install the first sealing pressure ring and the second sealing cover plate, and after the mortar is cured, remove the second sealing cover plate, the first sealing pressure ring, the first sealing cover plate, the barrel section sand core female mold, the second connecting sleeve and the inner liner;

[0032] Forming an integrated structure of the core shaft and the barrel sand core;

[0033] Step 5, installing the two end sand cores to the corresponding positions of the integrated structure in step 4, and fixing them respectively with fixing screw sleeves to form a sand core mold suitable for a small-diameter and large-aspect-ratio composite material shell.

[0034] Compared with the prior art, the present invention has the following technical effects:

[0035] The sand core mold suitable for small-diameter and large-aspect-ratio composite material shells of the present invention improves the petal-type core mold structure in view of the stress characteristics of the core shaft when molding small-diameter composite material shells in the prior art, and adopts an integrated structure of the core shaft, head sand core and barrel section sand core. Through structural optimization, the sand core mold can successfully complete the winding molding of small-diameter composite material shells.

[0036] In addition, the sand core mold for the composite material shell with a small diameter and a large aspect ratio of the present invention has multiple through holes on the mandrel. When demolding, it is no longer necessary to directly pull the sand core mold out of the composite material shell. It is only necessary to inject hot water into the mandrel through the nozzle to gradually dissolve the head sand core and the barrel sand core, so that the head sand core and the barrel sand core are directly dissolved into mortar and flow out of the composite material shell. This structure not only greatly improves the efficiency of demolding, but also does not cause damage to the composite material shell. It is suitable for the molding of composite material shells with small diameters and large aspect ratios, improves applicability and work efficiency, and is suitable for large-scale use and promotion in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the overall structure of a sand core mold suitable for a composite material shell with a small diameter and a large aspect ratio according to the present invention;

[0038] Figure 2 It is a schematic diagram of the core shaft structure in the present invention;

[0039] Figure 3 It is a schematic diagram of the longitudinal section structure of the mandrel in the present invention;

[0040] Figure 4 It is a schematic diagram of the cross-sectional structure of the mandrel in the present invention;

[0041] Figure 5 It is a schematic diagram of the longitudinal section structure of the barrel sand core in the present invention;

[0042] Figure 6 It is a schematic diagram of the sand core structure of the head in the present invention;

[0043] Figure 7 It is a cross-sectional structural schematic diagram of the connection between the barrel sand core and the core shaft in the present invention;

[0044] Figure 8 It is a schematic diagram of the connection structure between the barrel section sand core forming mold and the core shaft in the present invention;

[0045] Fig. 9 It is a cross-sectional structural diagram of the connection between the barrel-segment sand core forming mold and the core shaft in the present invention;

[0046] Fig.10 It is a schematic diagram of the cross-sectional structure of the head sand core forming mold in the present invention;

[0047] Fig.11 It is a schematic structural diagram of a head sand core male mold and a head sand core female mold in the present invention.

[0048] The meaning of the symbols in the figure is:

[0049] 1. Sand core of barrel section; 2. Mandrel; 3. Longitudinal ribs of sand core of barrel section; 4. Sand core of sealing head; 5. Longitudinal ribs of sand core of sealing head; 6. Sand consolidation groove; 7. Through hole; 8. Clamping part; 9. Water injection channel; 10. Connection nozzle; 11. Fixing screw sleeve; 12. Female mold of sand core of barrel section; 13. Inner liner; 14. First sealing cover plate; 15. First sealing pressure ring; 16. Second sealing cover plate; 17. Male mold of sand core of sealing head; 18. Female mold of sand core of sealing head; 19. Second sealing pressure ring; 20. Third sealing cover plate; 21. Rib groove. DETAILED DESCRIPTION

[0050] It should be noted that, unless otherwise specified, all components in the present invention are components known in the prior art.

[0051] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0052] like Figure 1-7 As shown, a sand core mold suitable for a composite material shell with a small diameter and a large aspect ratio is characterized in that it includes a barrel sand core 1, both ends of the barrel sand core 1 are fixedly connected to a head sand core 4, a core shaft 2 is penetrated into the barrel sand core 1, and a plurality of barrel sand core longitudinal ribs 3 extending along the length direction are evenly distributed on the inner wall of the barrel sand core 1; the inner wall of the head sand core 4 is provided with head sand core longitudinal ribs 5 corresponding to the barrel sand core longitudinal ribs 3 one by one;

[0053] Both left and right ends of the mandrel 2 extend out of the barrel sand core 1. The mandrel 2 is provided with sand consolidation grooves 6 along the length direction, the same number as the barrel sand core longitudinal ribs 3. The specifications of the sand consolidation grooves 6 match the barrel sand core longitudinal ribs 3. Multiple through holes 7 are evenly provided between two adjacent sand consolidation grooves 6 in the middle of the mandrel 2 along the length direction.

[0054] The core shaft 2 is a hollow structure, and the two ends of the core shaft 2 are connected with a clamping part 8 that can be connected to an external clamping device; the clamping part 8 has a water injection channel 9 in communication with the interior of the core shaft 2;

[0055] The end surface of the clamping portion 8 is also connected to a pipe nozzle 10 which is in sealed communication with the water injection channel 9 .

[0056] The sand core mold suitable for small-diameter and large-aspect-ratio composite material shells of the present invention improves the petal-type core mold structure in view of the stress characteristics of the core shaft 2 when molding small-diameter composite material shells in the prior art, and adopts an integrated structure of the core shaft 2, the head sand core 4 and the barrel section sand core 1. Through structural optimization, the sand core mold can successfully complete the winding molding of small-diameter composite material shells.

[0057] Among them, the mandrel 2 is used to install and fix the barrel sand core 1. When performing the winding operation of the composite shell with a small diameter and a large aspect ratio, the external clamping device can clamp the mandrel 2 through the clamping parts 8 at both ends; when demolding, it is no longer necessary to directly pull the sand core mold out of the composite shell. It is only necessary to inject hot water into the mandrel 2 through the nozzle 10 to gradually dissolve the head sand core 4 and the barrel sand core 1, so that the head sand core 4 and the barrel sand core 1 are directly dissolved into mortar and flow out of the composite shell. This structure not only greatly increases the efficiency of demolding, but also does not cause damage to the composite shell. It is suitable for the molding of composite shells with small diameters and large aspect ratios, improves applicability and work efficiency, and is suitable for large-scale use and promotion in industry.

[0058] As a preferred solution, it also includes two fixing screw sleeves 11; the left and right ends of the core shaft 2 extending outside the barrel sand core 1 serve as the left connecting part and the right connecting part respectively;

[0059] The fixing screw sleeve 11 is provided with an internal thread, and the left connecting part and the right connecting part of the core shaft 2 are provided with external threads matching the internal thread of the fixing screw sleeve 11;

[0060] The fixing screw sleeve 11 can be screwed to the core shaft 2 to fix and compress the corresponding head sand core 4 .

[0061] like Figure 8 , 9 As shown, a barrel segment sand core forming mold is used to form the above-mentioned sand core mold suitable for a small-diameter and large-aspect-ratio composite material shell, including a barrel segment sand core female mold 12 and an inner liner 13;

[0062] The inner sleeve 13 includes a first connecting sleeve and a plurality of cover plates. The first connecting sleeve can be fixedly sleeved on the left connecting portion of the core shaft 2. The shape of the cover plate matches the shape of the area between two adjacent sand consolidation grooves 6 on the core shaft 2. The plurality of cover plates seal and cover the area between two adjacent sand consolidation grooves 6 on the core shaft 2 in a one-to-one correspondence.

[0063] The barrel section sand core female mold 12 is cylindrical, the inner diameter of the barrel section sand core female mold 12 matches the outer diameter of the barrel section sand core 1, and the length of the barrel section sand core female mold 12 is equal to that of the barrel section sand core 1;

[0064] The first connecting sleeve of the inner sleeve 13 is sleeved with a second connecting sleeve, and the barrel section sand core female mold 12 is sleeved on the mandrel 2 through the second connecting sleeve. The shape of the area formed between the barrel section sand core female mold 12 and the mandrel 2 is the same as that of the barrel section sand core 1.

[0065] As a preferred solution, it also includes a first sealing cover plate 14, a first sealing pressure ring 15 and a second sealing cover plate 16;

[0066] The first sealing cover plate 14 is detachably mounted on the clamping portion 8 on the left side of the core shaft 2, and is used to seal the gap between the left side of the barrel sand core female mold 12 and the core shaft 2;

[0067] The first sealing pressure ring 15 and the second sealing cover plate 16 are detachably mounted on the right connecting portion of the core shaft 2 in sequence to seal the gap between the right side of the barrel sand core female mold 12 and the core shaft 2 .

[0068] This arrangement can further achieve sealing after compacting the mortar, thereby ensuring the molding effect of the barrel section sand core 1.

[0069] like Fig.10 , 11 As shown, a head sand core forming mold, the head sand core forming mold is used to form the head sand core 4 of claim 4, characterized in that it includes a head sand core male mold 17 and a head sand core female mold 18;

[0070] The shape of the area formed between the end cap sand core male mold 17 and the end cap sand core female mold 18 is the same as that of the end cap sand core 4 .

[0071] As a preferred solution, it also includes a second sealing pressure ring 19 and a third sealing cover plate 20;

[0072] The head sand core male mold 17 is a cylindrical structure, and a plurality of rib grooves 21 for forming the head sand core longitudinal ribs 5 of the head sand core 4 are provided on the head sand core male mold 17; a connector is coaxially connected to the front of the head sand core male mold 17;

[0073] The female mold 18 of the end cap sand core includes a molding part and a connecting part. The plug-in piece of the male mold 17 of the end cap sand core can be plugged into the connecting part of the female mold 18 of the end cap sand core in a sealing manner. The shape of the area formed between the inner wall of the molding part of the female mold 18 of the end cap sand core and the male mold 17 of the end cap sand core is the same as that of the end cap sand core 4.

[0074] The second sealing pressure ring 19 and the third sealing cover plate 20 are detachably mounted on the head sand core positive mold 17 from the rear of the head sand core positive mold 17 in sequence; the second sealing pressure ring 19 is used to seal the gap between the head sand core positive mold 17 and the sealing head sand core female mold 18.

[0075] This arrangement can further achieve sealing after compacting the mortar, thereby ensuring the molding effect of the head sand core 4.

[0076] Before the solid rocket engine composite material shell is completed, the core mold 2 is assembled first. Specifically, the head sand core 4 is bonded to the integrated structure of the core shaft 2 and the barrel section sand core 1, and fixed with a fixing screw sleeve 11. Then, the outer dimensions of the core mold 2 are corrected by conventional methods such as grinding or machining to meet the requirements of the inner surface of the composite material shell. After completion, winding is carried out.

[0077] After the composite material shell of the solid rocket engine is wound and the curing process is completed, hot water is injected into the core shaft 2 through the connecting nozzle 10. The hot water enters through the connecting nozzle 10, flows through the water injection channel 9, enters the inner cavity of the core shaft 2, and then flows into the space formed by the inner surface of the barrel section sand core 1, the head sand core 4 and the outer surface of the core shaft 2 through the through holes 7 evenly distributed on the core shaft 2. Here, the sand core is fully in contact with the hot water, and the water-soluble components (adhesive) are dissolved in water. The entire sand core gradually loosens and collapses. The collapsed part flows out from the connecting nozzle 10 at the other end with the water, or partially stays in the space formed by the inner surface of the barrel section sand core 1 and the outer surface of the core shaft 2. When the entire sand core is basically completely collapsed, the core shaft 2 can be removed to complete the demoulding of the composite material shell.

[0078] Specifically, the following steps are included:

[0079] Step 1: Apply a release agent to the parts where the head sand core male mold 17 and the head sand core female mold 18 are in contact with the mortar, and inject the mortar into the area between the head sand core male mold 17 and the head sand core female mold 18 and tamp it;

[0080] Step 2, install and fix the second sealing pressure ring 19 and the third sealing cover plate 20, and after the mortar is cured, remove the second sealing pressure ring 19, the third sealing cover plate 20, the head sand core male mold 17 and the head sand core female mold 18 to form the head sand core 4;

[0081] Repeat the above operation to make two head sand cores 4;

[0082] Step 3, applying a release agent to the portion where the barrel sand core female mold 12 contacts the mortar, and sequentially installing the inner liner 13, the second connecting sleeve, the barrel sand core female mold 12 and the first sealing cover plate 14 on the core shaft 2;

[0083] Step 4, inject mortar into the area between the barrel sand core female mold 12 and the core shaft 2 and tamp it, then install the first sealing pressure ring 15 and the second sealing cover plate 16, and after the mortar is cured, remove the second sealing cover plate 16, the first sealing pressure ring 15, the first sealing cover plate 14, the barrel sand core female mold 12, the second connecting sleeve and the inner liner 13;

[0084] An integrated structure of the core shaft 2 and the barrel sand core 1 is formed;

[0085] Step 5, installing the two end sand cores 4 to the corresponding positions of the integrated structure in step 4, and fixing them respectively with fixing screw sleeves 11 to form a sand core mold suitable for a composite material shell with a small diameter and a large aspect ratio.

Claims

1. A sand core mold suitable for a small-diameter and large-aspect-ratio composite material shell, characterized in that: It comprises a barrel section sand core (1), both ends of the barrel section sand core (1) are fixedly connected to a sealing head sand core (4), a core shaft (2) is inserted into the barrel section sand core (1), a plurality of barrel section sand core longitudinal ribs (3) extending along the length direction are evenly distributed on the inner wall of the barrel section sand core (1); and sealing head sand core longitudinal ribs (5) corresponding to the barrel section sand core longitudinal ribs (3) are arranged on the inner wall of the sealing head sand core (4); The left and right ends of the core shaft (2) extend out of the barrel sand core (1); the core shaft (2) is provided with sand consolidation grooves (6) in the same number as the barrel sand core longitudinal ribs (3) along the length direction; the specifications of the sand consolidation grooves (6) match the barrel sand core longitudinal ribs (3); a plurality of through holes (7) are evenly provided between two adjacent sand consolidation grooves (6) in the middle of the core shaft (2) along the length direction; The mandrel (2) is a hollow structure, and both ends of the mandrel (2) are connected to clamping parts (8) that can be connected to an external clamping device; the clamping part (8) is provided with a water injection channel (9) in communication with the interior of the mandrel (2); The end surface of the clamping portion (8) is also connected to a pipe connection nozzle (10) which is in sealed communication with the water injection channel (9).

2. The sand core mold suitable for a small-diameter and large-aspect-ratio composite material shell according to claim 1, characterized in that: It also includes two fixing screw sleeves (11); the left and right ends of the core shaft (2) extending outside the barrel sand core (1) serve as connecting parts; The fixing screw sleeve (11) is provided with an internal thread, and the connecting portion of the core shaft (2) is provided with an external thread matching the internal thread of the fixing screw sleeve (11).

3. A barrel segment sand core forming mold, the barrel segment sand core forming mold is used to form the barrel segment sand core (1) according to claim 2, characterized in that: It comprises a barrel section sand core female mold (12) and an inner liner (13); The inner sleeve (13) comprises a first connecting sleeve and a plurality of cover plates, wherein the first connecting sleeve can be fixedly sleeved on the connecting portion on the left side of the core shaft (2); the shape of the cover plate matches the shape of the area between two adjacent sand consolidation grooves (6) on the core shaft (2), and the plurality of cover plates seal and cover the area between two adjacent sand consolidation grooves (6) on the core shaft (2) in a one-to-one correspondence; The barrel section sand core female mold (12) is cylindrical, the inner diameter of the barrel section sand core female mold (12) matches the outer diameter of the barrel section sand core (1), and the length of the barrel section sand core female mold (12) is equal to that of the barrel section sand core (1); A second connecting sleeve is mounted on the first connecting sleeve of the inner sleeve (13); the barrel section sand core female mold (12) is mounted on the core shaft (2) through the second connecting sleeve; and the shape of the area formed between the barrel section sand core female mold (12) and the core shaft (2) is the same as the shape of the barrel section sand core (1).

4. The barrel section sand core forming mold according to claim 3, characterized in that: It also includes a first sealing cover plate (14), a first sealing pressure ring (15) and a second sealing cover plate (16); The first sealing cover plate (14) is detachably mounted on the clamping portion (8) on the left side of the core shaft (2) and is used to seal the gap between the left side of the barrel sand core female mold (12) and the core shaft (2); The first sealing pressure ring (15) and the second sealing cover plate (16) are detachably mounted on the right connecting portion of the core shaft (2) in sequence, and are used to seal the gap between the right side of the barrel section sand core female mold (12) and the core shaft (2).

5. A head sand core forming mold, the head sand core forming mold is used to form the head sand core (4) according to claim 4, characterized in that: It comprises a male mold (17) of the sealing head sand core and a female mold (18) of the sealing head sand core; The shape of the area formed between the sealing head sand core male mold (17) and the sealing head sand core female mold (18) is the same as that of the sealing head sand core (4).

6. The head sand core forming mold according to claim 5, characterized in that: It also includes a second sealing pressure ring (19) and a third sealing cover plate (20); The head sand core male mold (17) is a cylindrical structure, and a plurality of rib forming grooves (21) for forming the head sand core longitudinal ribs (5) of the head sand core (4) are provided on the head sand core male mold (17); a plug-in component is coaxially connected to the front of the head sand core male mold (17); The female mold (18) of the sealing head sand core comprises a molding part and a connecting part, and the plug-in component of the male mold (17) of the sealing head sand core can be plugged into the connecting part of the female mold (18) of the sealing head sand core in a sealing manner; the shape of the area formed between the inner wall of the molding part of the female mold (18) of the sealing head sand core and the male mold (17) of the sealing head sand core is the same as that of the sealing head sand core (4); The second sealing pressure ring (19) and the third sealing cover plate (20) are detachably mounted on the head sand core positive mold (17) from the rear of the head sand core positive mold (17) in sequence; the second sealing pressure ring (19) is used to seal the gap between the head sand core positive mold (17) and the sealing head sand core negative mold (18).

7. A method for forming a sand core mold suitable for a composite material shell with a small diameter and a large aspect ratio, the method being based on the barrel section sand core forming mold and the end cap sand core forming mold as claimed in claim 6, characterized in that: The following steps are involved: Step 1, applying a release agent to the parts of the head sand core male mold (17) and the head sand core female mold (18) that are in contact with the mortar, injecting the mortar into the area between the head sand core male mold (17) and the head sand core female mold (18) and compacting it; Step 2, installing and fixing the second sealing pressure ring (19) and the third sealing cover plate (20), and removing the second sealing pressure ring (19), the third sealing cover plate (20), the head sand core male mold (17) and the head sand core female mold (18) after the mortar is cured, to form the head sand core (4); Repeat the above operation to make two head sand cores (4); Step 3, applying a release agent to the portion of the barrel section sand core female mold (12) that contacts the mortar, and sequentially installing the inner liner (13), the second connecting sleeve, the barrel section sand core female mold (12) and the first sealing cover plate (14) on the core shaft (2); Step 4, injecting mortar into the area between the barrel section sand core female mold (12) and the core shaft (2) and compacting it, then installing the first sealing pressure ring (15) and the second sealing cover plate (16), and after the mortar is cured, removing the second sealing cover plate (16), the first sealing pressure ring (15), the first sealing cover plate (14), the barrel section sand core female mold (12), the second connecting sleeve and the inner liner (13); An integrated structure of the core shaft (2) and the barrel sand core (1) is formed; Step 5, installing the two end sand cores (4) to the corresponding positions of the integrated structure in step 4, and fixing them respectively with fixing screw sleeves (11), so as to form a sand core mold suitable for a composite material shell with a small diameter and a large aspect ratio.

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