Forming method of thin-wall cavity type composite material workpiece with honeycomb sandwich structure

Abstract

The invention discloses a forming method of a thin-wall cavity type composite material part with a honeycomb sandwich structure, which comprises the following steps: paving an inner skin prepreg of the thin-wall cavity type composite material part on the outer surface of a forming die and curing, paving flanging prepregs on the outer wall surface of the periphery of the inner skin layer by layer, a positioning ring for installing a forming die is arranged at the bottom of the circumferential ring of the flanging prepreg in a sleeving mode, flanging treatment is conducted on the flanging area of the flanging prepreg through the positioning ring, a honeycomb core is laid on the glue film on the outer surface of the inner skin, and the bottom of the circumferential ring of the laid honeycomb core is pressed on the glue film on the top face of the groove-shaped flanging; and the adhesive film and the outer skin prepreg are sequentially laid on the honeycomb core for curing forming, and therefore the thin-wall cavity type composite material part is formed. According to the forming method provided by the invention, the problems that the product surface quality and the cementing quality of a thin-wall cavity type composite material part are poor, and the molded surface precision is poor due to the fact that the inner skin, the outer skin and the honeycomb core are assembled inharmoniously are solved.

Description

Technical Field

[0001] The present invention relates to, but is not limited to, the field of composite material forming and manufacturing, and particularly refers to a forming method for a thin-walled cavity composite material part with a honeycomb core structure. Background Art

[0002] In recent years, with the continuous progress of science and technology, material technology has developed rapidly. As a new type of material, composite materials have many excellent properties, such as: light weight, high specific strength, high specific modulus, good fatigue resistance and shock absorption performance; flexible forming process, and their structure and performance have strong designability; good chemical corrosion resistance and good insulation performance; good thermal stability, etc. They have been widely used in the fields of aviation, aerospace, automotive, weapons, electronics, construction, medical, etc. After aluminum, steel, and titanium, advanced composite materials have rapidly developed into one of the four major structural materials, and their usage has become one of the indicators of the advancement of aerospace structures.

[0003] Lightweight and high precision are the current development directions in the fields of aviation, aerospace, etc., and the selection of composite materials is an effective way to achieve lightweight. With the rapid development of manufacturing technology, the precision requirements for cavity composite material parts are getting higher and higher. For the traditional one-time curing forming scheme, the surface accuracy of the cavity type surface is poor after curing. Especially for cavity composite material parts with a honeycomb core structure, the surface accuracy of the type surface far cannot meet the design requirements; moreover, most cavity parts are cylindrical or conical structures, and the bonding degree between the honeycomb core and the skin during the forming process is poor. After curing, there will be large internal stresses in the cavity type surface. During subsequent use, the release of internal stresses will cause large changes in the surface accuracy of the type surface, affecting the product performance. In addition, in order to reduce weight during the design of cavity parts, most of them use thin skin and honeycomb core sandwich structures, and the thickness of most cavity skins does not exceed 0.5 mm; for such thin-walled cavity composite material parts, if the traditional one-time curing forming method is used, obvious honeycomb core imprints will appear on the surface of the part after curing, affecting the surface quality of the product; if the secondary bonding process is used, that is, the inner and outer skins are first cured and formed separately, and then bonded to the honeycomb core through a film adhesive, in addition to the relatively cumbersome manufacturing process, there are also problems of inconsistent assembly between the inner and outer skins and the honeycomb core, resulting in poor surface accuracy of the type surface. Especially for thin-walled cavity composite material parts with a honeycomb core structure with a grooved flange, the bonding quality of the final product cannot be guaranteed. Summary of the Invention

[0004] The object of the present invention is to provide a forming method for a thin-walled cavity composite material part with a honeycomb core structure to solve the problems of poor product surface quality and bonding quality of the existing thin-walled cavity composite material part with a honeycomb core structure, and poor surface accuracy of the type surface caused by inconsistent assembly between the inner and outer skins and the honeycomb core.

[0005] The technical solution of the present invention is as follows: The present invention provides a forming method for a thin-walled cavity composite part with a honeycomb sandwich structure, including: Step 1, lay the inner skin 4 prepreg on the working surface of the forming die, place a tear layer on the outer surface of the inner skin prepreg and then make a bag, and cure and form in an autoclave according to the curing parameters of the prepreg to form an inner skin 4 that is consistent with the working surface of the forming die; the working surface of the forming die includes the upper end surface of the forming die and the circumferential outer wall surface; Step 2, remove the tear layer on the outer surface of the cured inner skin 4, lay a film adhesive 5 on the outer surface of the inner skin 4, and lay the flanging prepreg layer by layer on the circumferential outer wall surface of the inner skin 4; during the flanging laying process, the area above the preset height area at the bottom of the circumferentially laid flanging prepreg is used as the flanging area, and an isolation film is placed between each layer of flanging prepreg in the flanging area. After the laying is completed, install the positioning ring 8 of the forming die at the circumferential bottom of the flanging prepreg, so as to sleeved the positioning ring 8 on the preset height area at the bottom of the flanging prepreg, and perform flanging treatment on the flanging prepreg in the flanging area based on the top end surface and the outer circumferential wall surface of the positioning ring 8; the laid flanging prepreg is used to form a channel-shaped flange 3 after curing. Step 3, lay a film adhesive 5 on the top surface and the outer ring surface of the flanging prepreg, lay a honeycomb core 6 on the film adhesive 5 on the outer surface of the inner skin 4, and press the circumferential bottom of the laid honeycomb core 6 against the film adhesive 5 on the top surface of the flanging prepreg, and sequentially lay a film adhesive 5 and an outer skin 7 prepreg on the honeycomb core 6; Step 4, lay a uniform pressure plate on the top surface and the circumferential outer wall surface of the outer skin prepreg, make a bag after the uniform pressure plate is laid, and cure and form in an autoclave according to the curing parameters of the prepreg to form a thin-walled cavity composite part with a honeycomb sandwich structure through a co-bonding process.

[0006] Optionally, in a forming method for a thin-walled cavity composite part with a honeycomb sandwich structure as described above, During the laying process of the inner skin prepreg in Step 1 and during the laying process of the flanging prepreg in Step 2, vacuum compaction is performed on each layer of the inner skin prepreg; and during the laying process, the number of layers and the laying angle sequence of the prepreg are laid according to the design requirements; During the process of laying the film adhesive 5, laying the honeycomb core 6, and laying the outer skin prepreg in Step 3, vacuum compaction is performed on each layer, and the number of layers and the laying angle sequence of the prepreg are laid according to the design requirements.

[0007] Optionally, in a forming method for a thin-walled cavity composite part with a honeycomb sandwich structure as described above, In step 3, the honeycomb core 6 is laid in a block-by-block splicing manner, and the splicing joints are bonded with foam glue. The filling glue is used to fill and strengthen the honeycomb core 6 at the corner positions during laying.

[0008] Optionally, in a forming method of a thin-walled cavity composite part with a honeycomb sandwich structure as described above, The forming die material used is steel or ductile iron; the die body of the forming die is set as a columnar structure, and the forming die further includes: a positioning ring 8 sleeved on the periphery of the bottom of the columnar structure; wherein, the cross-section of the die body of the columnar structure includes but is not limited to circular, oval, and square, and the die body of the columnar structure is of equal cross-section or unequal cross-section.

[0009] Optionally, in a forming method of a thin-walled cavity composite part with a honeycomb sandwich structure as described above, The positioning ring 8 is a segmented structure in the circumferential direction, and the bottom of the positioning ring 8 is fixedly connected to the die body of the forming die through positioning bolts.

[0010] Optionally, in a forming method of a thin-walled cavity composite part with a honeycomb sandwich structure as described above, the thin-walled cavity composite part to be formed has embedded parts; During the process of laying the honeycomb core 6 in step 3, the installation position of the embedded part 2 is reserved. After the laying of the honeycomb core 6 is completed, the embedded part is placed at the installation position of the embedded part 2, and foam glue is filled between the embedded part 2 and the honeycomb core 6 for strengthening according to the specified glue filling range; and a positioning hole for positioning the embedded part 2 is provided on the top end surface of the die body of the forming die; When laying the adhesive film 5 and the prepreg of the outer skin 7, an opening area for avoiding the embedded part 2 is provided on the laid adhesive film 5 and the prepreg of the outer skin 7, so that the top of the embedded part 2 protrudes from the adhesive film 5 and the prepreg of the outer skin.

[0011] Optionally, in a forming method of a thin-walled cavity composite part with a honeycomb sandwich structure as described above, the leveling plate laid in step 4 is a combined leveling plate, and the combined leveling plate includes a backing plate 9 and a thin aluminum plate. Step 4 specifically includes: Place a backing plate 9 with the same thickness as the protruding height of the embedded part 2 on the top surface of the outer skin prepreg, so that the top surface of the backing plate 9 is flush with the top of the embedded part 2. The backing plate 9 can control the protruding height of the embedded part 2 while playing a role in uniform pressure; place a positioning template 10 on the top surfaces of the backing plate 9 and the embedded part 2, and use a positioning pin 11 to fix the positioning template 10 and the embedded part 2 on the forming die; after laying a thin aluminum plate on the outer circumferential wall surface of the outer skin 7 prepreg to make a bag, cure and form in an autoclave according to the curing parameters of the prepreg to form a thin-walled cavity composite part with the embedded part 2. In this step, by placing the backing plate 9 and the positioning template 10 on the top surface of the outer skin 7 prepreg, the protruding height of the embedded part 2 and the positional tolerance of the center hole of the embedded part are ensured.

[0012] Optionally, in the forming method of a thin-walled cavity composite part with a honeycomb core structure as described above, in step 4, The thin aluminum plate is laid in a segmented splicing manner, and the splicing position is fixed with pressure-sensitive tape; and the aluminum plate laid on the outer circumferential wall surface of the outer skin prepreg is a thin aluminum plate with a thickness of 0.3 mm to 0.5 mm to ensure good adhesion between the thin aluminum plate and the outer surface of the outer skin 7 prepreg.

[0013] The beneficial effects of the present invention are as follows: The present invention provides a forming method for a thin-walled cavity composite part with a honeycomb core structure. First, lay the inner skin 4 prepreg of the thin-walled cavity composite part on the outer surface of the forming die and cure it to form the inner skin 4. Lay a glue film 5 on the inner skin 4, layer by layer lay the flanging prepreg on the outer circumferential wall surface of the inner skin 4, and set and install the positioning ring 8 of the forming die at the bottom of the circumference of the flanging prepreg to flang the flanging area of the flanging prepreg through the positioning ring 8, and lay the glue film 5 on the top surface and the outer ring surface of the flanged flanging prepreg; then, lay the honeycomb core 6 on the glue film 5 on the outer surface of the inner skin 4, so that the bottom of the circumference of the laid honeycomb core 6 is pressed on the glue film 5 on the top surface of the groove-shaped flange 3; lay the glue film 5 and the outer skin 7 prepreg on the honeycomb core 6 in sequence and cure and form, so as to form a thin-walled cavity composite part through the above co-bonding process. Further, for a thin-walled cavity composite part with an embedded part 2, during the process of laying the honeycomb core 6 as described above, it is necessary to reserve the installation position of the embedded part 2. After completing the laying of the honeycomb core 6, place the embedded part at the installation position of the embedded part 2; and by placing a backing plate 9 with the same thickness as the protruding height of the embedded part 2 on its top surface after laying the outer skin 7 prepreg, it plays a role in uniform pressure and controls the protruding height of the embedded part 2. The technical solution provided by the present invention specifically has the following beneficial effects: 1) The present invention adopts a co-bonding forming process. After the inner skin 4 is cured separately, it is co-bonded with the honeycomb core 6 and the outer skin 7, solving the problems of poor flatness of the working surface of the composite part after forming and deep honeycomb core imprint in the honeycomb core sandwich structure, and effectively ensuring the surface quality and surface accuracy of the working surface of the part. 2) The present invention adopts a co-bonding forming process, solving the problem of inconsistent coordination between the thin-walled cavity of the honeycomb core sandwich structure and the flanged edge of the groove, and effectively ensuring the bonding quality of the final part. 3) In the part forming method provided by the present invention, the honeycomb core 6 is spliced in blocks using foam adhesive, effectively avoiding the risk of large internal stress in the part after curing caused by the non-conformance between the honeycomb core and the inner and outer skins when using a whole honeycomb core for assembly; at the corner position, filling adhesive is used for filling and strengthening, avoiding the risk of surface depression of the part after curing due to insufficient strength at this position. 4) In the part forming method provided by the present invention, for the part with the embedded part 2, by placing a spacer 9 with the same thickness as the protruding height of the embedded part 2 on the top surface of the prepreg of the outer skin 7 and placing a positioning template 10 on the spacer 9 for positioning, while ensuring the installation position of the embedded part 2, it can ensure that the protruding height of the embedded part 2 meets the design requirements. 5) In the technical solution provided by the present invention, a combined uniform pressure plate is adopted, which can ensure good adhesion between the uniform pressure plate and the outer surface of the prepreg of the outer skin 7, and ensure that the surface quality of the final part 7 meets the design requirements. Description of the Drawings

[0014] The drawings are used to provide a further understanding of the technical solution of the present invention, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention, and do not constitute a limitation to the technical solution of the present invention.

[0015] Figure 1 It is a schematic structural diagram of a thin-walled cavity composite part with a honeycomb sandwich structure in an embodiment of the present invention; Figure 2 It is a schematic diagram of the paving structure of each layer of a thin-walled cavity composite part with a honeycomb sandwich structure in the forming method provided by the present invention; Figure 3 It is Figure 2 A specific structural diagram of the flanged edge of the groove in the thin-walled cavity composite part provided by the shown embodiment; Figure 4 It is a schematic structural diagram of the embedded part, the spacer 9, and the positioning template 10 in the forming method provided by the present invention.

[0016] Description of the Reference Numerals: 1-Outer surface of the workpiece; 2-Embedded part; 3-Grooved flanging; 4-Inner skin; 5-Adhesive film; 6-Honeycomb core; 7-Outer skin; 8-Locating ring; 9-Backing plate; 10-Locating template; 11-Locating pin. Specific embodiments To make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily.

[0018] As already described in the above background art, for thin-walled cavity composite parts with honeycomb core sandwich structures, using traditional one-time curing forming methods or secondary bonding process methods have corresponding process problems respectively.

[0019] To solve the problems existing in the existing preparation schemes for thin-walled cavity composite parts, the present invention provides a forming method for thin-walled cavity composite parts with honeycomb sandwich structures.

[0020] The present invention provides the following specific embodiments that can be combined with each other. For the same or similar concepts or processes, they may not be repeated in some embodiments.

[0021] Embodiment 1 Embodiment 1 of the present invention provides a forming method for thin-walled cavity composite parts with honeycomb sandwich structures, including the following steps: Step 1, lay the inner skin 4 prepreg on the working surface of the forming mold, place a bag after laying a peeling layer on the outer surface of the inner skin prepreg, and perform curing and forming in a autoclave according to the curing parameters of the prepreg to form an inner skin 4 that is consistent with the working surface of the forming mold; wherein, the working surface of the forming mold includes the upper end surface and the circumferential outer wall surface of the forming mold; Step 2, remove the peeling layer on the outer surface of the cured inner skin 4, lay an adhesive film 5 on the outer surface of the inner skin 4, and lay flanging prepreg layer by layer on the circumferential outer wall surface of the inner skin 4; during the flanging laying process, the area above the preset height area at the bottom of the circumferential laid flanging prepreg is used as the flanging area, and an isolation film is placed between each layer of flanging prepreg in the flanging area. After laying, install the locating ring 8 of the forming mold at the circumferential bottom of the flanging prepreg, so as to sleeved the locating ring 8 on the preset height area at the bottom of the flanging prepreg, and perform flanging treatment on the flanging prepreg in the flanging area based on the top end surface and the outer circumferential wall surface of the locating ring 8; wherein, the laid flanging prepreg forms a grooved flanging 3 after subsequent curing and forming; Step 3: Lay the adhesive film 5 on the top surface and the outer ring surface of the flanging prepreg, lay the honeycomb core 6 on the adhesive film 5 on the outer surface of the inner skin 4, and press the bottom of the circumferential circle of the laid honeycomb core 6 onto the adhesive film 5 on the top surface of the flanging prepreg. Then, lay the adhesive film 5 and the outer skin 7 prepreg on the honeycomb core 6 in sequence; Step 4: Lay the uniform pressure plate on the top surface and the circumferential outer wall surface of the outer skin prepreg. After laying the uniform pressure plate, make a bag. Then, carry out curing and forming in an autoclave according to the curing parameters of the prepreg. The uniform pressure plate in this step can be made of thin aluminum plate.

[0022] In an implementation manner of the embodiment of the present invention, during the laying process of the inner skin prepreg in the above step 1 and during the laying process of the flanging prepreg in step 2, vacuum compaction is carried out on each layer of the inner skin prepreg; and during the laying process, the number of layers and the laying angle sequence of the prepreg are laid according to the design requirements. Similarly, during the process of laying the adhesive film 5, laying the honeycomb core 6, and laying the outer skin prepreg in step 3, vacuum compaction is carried out on each layer, and the number of layers and the laying angle sequence of the prepreg are laid according to the design requirements.

[0023] In an implementation manner of the embodiment of the present invention, in the above step 3, when laying the honeycomb core 6, a piece-by-piece splicing laying method is adopted. The splicing seam position is bonded with foam glue, and the filling glue is used for filling and strengthening at the corner position of the laid honeycomb core 6.

[0024] In an implementation manner of the embodiment of the present invention, the forming die material used for the forming process of the present invention is steel or ductile iron. The die body of the forming die is set as a columnar structure. The forming die further includes: a positioning ring 8 sleeved on the circumferential circle at the bottom of the columnar structure; wherein, the cross-section of the columnar die body includes, but is not limited to, a circular shape, an oval shape, and a square shape, and the columnar structure of the forming die is of equal cross-section or unequal cross-section.

[0025] The positioning ring 8 in this implementation manner can be set as a segmented structure in the circumferential direction, and the bottom of the positioning ring 8 is fixedly connected to the die body of the forming die through positioning bolts.

[0026] It should be noted that the above embodiments provide a co-bonding process forming scheme for thin-walled cavity composite parts with a honeycomb sandwich structure. For the forming method of a thin-walled cavity composite part with embedded parts inside, its specific forming method is proposed through the following embodiments.

[0027] Embodiment 2 The embodiment 2 of the present invention provides a forming method for a thin-walled cavity composite part with a honeycomb sandwich structure. The steps 1 and 2 of this embodiment 2 are the same as those of the above embodiment 1, and the differences are as follows: During the process of laying the honeycomb core 6 in step 3 of the above-mentioned Embodiment 1, a mounting position for the embedded part 2 is reserved. After the honeycomb core 6 is laid, the embedded part is placed at the mounting position of the embedded part 2. The embedded part 2 is positioned through the positioning holes on the forming die, and foam glue is filled between the embedded part 2 and the honeycomb core 6 according to the specified glue filling range for strengthening. For the forming die of the workpiece in this Embodiment 2, positioning holes for positioning the embedded part 2 are provided on the top surface of the die body.

[0028] When laying the adhesive film 5 and the prepreg of the outer skin 7, an opening area for avoiding the embedded part 2 is provided on the laid adhesive film 5 and the prepreg of the outer skin 7, so that the top of the embedded part 2 protrudes from the adhesive film 5 and the prepreg of the outer skin.

[0029] The pressing plate laid in step 4 of this Embodiment 2 is a combined uniform pressing plate, and the combined uniform pressing plate includes a backing plate 9 and a thin aluminum plate. Step 4 of this Embodiment 2 specifically includes: Place a backing plate 9 with the same thickness as the protruding height of the embedded part 2 on the top surface of the prepreg of the outer skin, so that the backing plate 9 and the top of the embedded part 2 are flush. The backing plate 9 can control the protruding height of the embedded part 2 while playing a role in uniform pressing; place a positioning template 10 on the top surfaces of the backing plate 9 and the embedded part 2, and use a positioning pin 11 to fix the positioning template 10 and the embedded part 2 on the forming die; after laying a thin aluminum plate on the outer circumferential wall surface of the prepreg of the outer skin 7 to form a bag, the thickness of the thin aluminum plate is 0.3 mm to 0.5 mm, and it is cured and formed in a autoclave according to the curing parameters of the prepreg to form a thin-walled cavity composite workpiece with an embedded part 2.

[0030] It should be noted that in step 4 of this Embodiment 2, by placing the backing plate 9 and the positioning template 10 on the top surface of the prepreg of the outer skin 7, the protruding height of the embedded part 2 and the positional tolerance of the central hole of the embedded part are ensured. The outer surface 1 of the workpiece formed by the forming method of the thin-walled cavity composite workpiece with a honeycomb sandwich structure provided in this Embodiment 2 is as Figure 1 shown.

[0031] In one implementation manner of the embodiment of the present invention, in step 4, the thin aluminum plate is laid in a segmented splicing manner, and the splicing position is fixed with a pressure-sensitive tape; and the aluminum plate laid on the outer circumferential wall surface of the prepreg of the outer skin is a thin aluminum plate with a thickness of 0.3 mm to 0.5 mm to ensure good adhesion between the aluminum plate and the outer surface of the prepreg of the outer skin 7.

[0032] The present invention provides a forming method for a thin-walled cavity composite part with a honeycomb sandwich structure. First, the inner skin 4 prepreg of the thin-walled cavity composite part is laid on the outer surface of the forming die and cured to form the inner skin 4. A film adhesive 5 is laid on the inner skin 4. The flanging prepreg is laid layer by layer on the outer circumferential wall surface of the inner skin 4. By sleeving and installing the positioning ring 8 of the forming die at the bottom of the circumference of the flanging prepreg, the flanging area of the flanging prepreg is flanged, and a film adhesive 5 is laid on the top surface and the outer ring surface of the flanged flanging prepreg. Subsequently, a honeycomb core 6 is laid on the film adhesive 5 on the outer surface of the inner skin 4, so that the bottom of the circumference of the laid honeycomb core 6 is pressed against the film adhesive 5 on the top surface of the grooved flange 3. A film adhesive 5 and an outer skin 7 prepreg are sequentially laid on the honeycomb core 6 and cured and formed, so as to form a thin-walled cavity composite part through the above co-bonding process. Further, for a thin-walled cavity composite part with an embedded part 2, during the process of laying the honeycomb core 6 as described above, a mounting position for the embedded part 2 needs to be reserved. After the laying of the honeycomb core 6 is completed, the embedded part is placed at the mounting position of the embedded part 2; and by placing a spacer 9 with the same thickness as the protruding height of the embedded part 2 on the top surface after laying the outer skin 7 prepreg, a uniform pressing effect is achieved and the protruding height of the embedded part 2 is controlled. The technical solution provided by the present invention specifically has the following beneficial effects: 1) The present invention adopts a co-bonding forming process. After the inner skin 4 is cured separately, it is co-bonded with the honeycomb core 6 and the outer skin 7, solving the problems of poor flatness of the working surface of the thin-walled cavity composite part with a honeycomb sandwich structure and relatively deep honeycomb core imprint after forming, and effectively ensuring the surface quality and surface accuracy of the working surface of the part; 2) The present invention adopts a co-bonding forming process, solving the problem of inconsistent coordination between the thin-walled cavity with a honeycomb sandwich structure and the grooved flange, and effectively ensuring the bonding quality of the final part; 3) In the part forming method provided by the present invention, the honeycomb core 6 is spliced in blocks using foam adhesive, effectively avoiding the risk that when using a whole honeycomb core for assembly, the honeycomb core does not fit well with the inner and outer skins, resulting in large internal stresses in the cured part; at the corner positions, a filling adhesive is used for filling and strengthening, avoiding the risk of insufficient strength at this position and surface depression of the cured part; 4) In the part forming method provided by the present invention, for a part with an embedded part 2, by placing a spacer 9 with the same thickness as the protruding height of the embedded part 2 on the top surface of the outer skin 7 prepreg and placing a positioning template 10 on the spacer 9 for positioning, while ensuring the installation position of the embedded part 2, the protruding height of the embedded part 2 can be ensured to meet the design requirements; 5) In the technical solution provided by the present invention, a combined uniform pressing plate is adopted, which can ensure good fit between the uniform pressing plate and the outer surface of the outer skin 7 prepreg, and ensure that the surface quality of the final part 7 meets the design requirements.

[0033] The following is a schematic illustration of an implementation example of the method for forming a thin-walled cavity composite material product having a honeycomb sandwich structure provided by the present invention.

[0034] Implementation example: Main materials: carbon fiber fabric prepreg 5222A / G803, adhesive film Redux 319L, honeycomb core BC1.8-3 / 8P-11, foam adhesive Redux 208-5 / NA, filling adhesive: Epocast 1629A / B; Figure 1 The structure of the thin-walled cavity composite material product with a honeycomb sandwich structure to be manufactured is provided with an embedded part 2 on the top of the product.

[0035] 1) Inner skin 4 molding The inner skin 4 prepreg is laid on the working surface of the forming mold, with 2 layers laid and the angles symmetrical at [0° / 90°]. During the laying process, each layer of the inner skin 4 prepreg must be vacuum compacted. After the inner skin 4 prepreg is laid, a tear-off layer is laid on the outer surface. After the laying is completed, the bag is made and cured in an autoclave according to the curing parameter requirements of the prepreg. After curing, the inner skin 4 is formed to be consistent with the working surface of the forming mold.

[0036] It should be noted that the working surface of the forming die used in this implementation example includes the upper end surface of the forming die and the outer wall surface of the circumference.

[0037] 2) Paving groove flange The torn-off layer on the outer surface of the inner skin 4 that has been cured and formed in step 1 is removed, the adhesive film 5 is laid on the outer surface of the inner skin 4, and the flange prepreg is laid layer by layer on the outer wall surface of the circumference of the inner skin 4.

[0038] The specific method of laying the flanged prepreg in this step is: laying the flanged prepreg layer by layer on the outer wall surface of the circumference of the inner skin 4, the number of laying layers is 4, and the laying angles are symmetrical at [0° / +45° / -45° / 90°]. During the laying and flanging process, the area above the bottom preset height area of the flanged prepreg laid around the circumference is used as the flanging area, and an isolation film is placed between each layer of flanged prepreg in the flanging area. After the laying is completed, a positioning ring 8 of the forming mold is installed at the bottom of the circumference of the flanged prepreg, so that the positioning ring 8 is sleeved on the bottom preset height area of the flanged prepreg, and the flanged prepreg in the flanging area is flanging-processed based on the top end face of the positioning ring 8 and the outer wall surface to form a groove-shaped flange 3; during the laying process of the flanged prepreg, each layer of the flanged prepreg is vacuum compacted.

[0039] It should be noted that the flange prepreg in the above-mentioned bottom preset height area is used to form the flange inner area and the R angle area connected between the flange inner annular surface and the flange top surface.

[0040] 3) Laying the honeycomb core 6 and the embedded part 2 Lay the adhesive film 5 on the top surface and the outer ring surface of the flanged prepreg, and lay the honeycomb core 6 on the outer surface of the inner skin 4 located above the flanged prepreg, and press the bottom of the laid honeycomb core 6 around the perimeter on the adhesive film 5 on the top surface of the flanged prepreg. The honeycomb core 6 is divided into 3 pieces and spliced according to the curvature of the cavity. The splicing seam position is spliced using the foam adhesive Redux 208-5 / NA, and the corner position is filled and strengthened using the filling adhesive Epocast 1629A / B.

[0041] In this embodiment, since the part has the embedded part 2, the installation position of the embedded part 2 is reserved when laying the honeycomb core 6. After laying the honeycomb core 6, place the embedded part 2, and use the foam adhesive Redux 208-5 / NA to fill and strengthen the honeycomb cells within a range of 10 mm to 30 mm around the installation position of the embedded part 2.

[0042] 4) Laying the prepreg of the outer skin 7 Through the treatment of the above steps 1 to 3, the outer surface of the laid honeycomb core 6 is used as the surface to be bonded. On this surface to be bonded, lay the adhesive film 5 and the prepreg of the outer skin 7 in sequence. The number of laying layers is 2 layers, and the angles are symmetric according to [90° / 0°].

[0043] It should be noted that during the laying process, an opening area for avoiding the embedded part 2 is opened on the adhesive film 5 and the prepreg of the outer skin 7, so that the top of the embedded part 2 protrudes from the adhesive film 5 and the prepreg of the outer skin. In addition, during the laying process, it is required that each layer must be vacuum compacted. After laying, place the backing plate 9 and the positioning template 10 on the top surface of the prepreg of the outer skin 7 in sequence, and use the positioning pin 11 to fix the positioning template 10 and the embedded part 2 on the forming die. The thickness of the backing plate 9 is equal to the protruding height of the embedded part 2, which can control the protruding height of the embedded part 2 while playing a role in uniform pressure. Place a 0.5 mm thick thin aluminum plate in other areas (i.e., the outer circumferential wall surface of the prepreg of the outer skin 7), and fix the thin aluminum plate with pressure-sensitive tape; then make a bag and cure and form in a autoclave according to the curing parameter requirements of the prepreg.

[0044] It has been verified that the final product formed by using the forming method of the thin-walled cavity composite part with a honeycomb sandwich structure provided by the present invention is qualified and meets the design requirements.

[0045] Although the disclosed embodiments of the present invention are as above, the content is only the embodiments adopted for the convenience of understanding the present invention, and is not used to limit the present invention. Any person skilled in the art within the scope of the present invention can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A forming method for a thin-walled cavity composite part with a honeycomb sandwich structure, characterized in that, Including: Step 1: Lay the inner skin (4) prepreg on the working surface of the forming die. After laying the release layer on the outer surface of the inner skin prepreg, make a bag. Cure and form in an autoclave according to the curing parameters of the prepreg to form an inner skin (4) that is consistent with the working surface of the forming die. The working surface of the forming die includes the upper end surface and the circumferential outer wall surface of the forming die. Step 2: Remove the release layer on the outer surface of the cured inner skin (4). Lay the adhesive film (5) on the outer surface of the inner skin (4), and lay the flanging prepreg layer by layer on the circumferential outer wall surface of the inner skin (4). During the flanging laying process, the area above the preset height area at the bottom of the circumferential flanging prepreg is used as the flanging area. An isolation film is placed between each layer of flanging prepreg in the flanging area. After laying, install the positioning ring (8) of the forming die at the circumferential bottom of the flanging prepreg, so that the positioning ring (8) is sleeved on the preset height area at the bottom of the flanging prepreg, and the flanging prepreg in the flanging area is flanged based on the top end surface and the outer circumferential wall surface of the positioning ring (8). The laid flanging prepreg is used to form a channel-shaped flange (3) after curing. Step 3: Lay the adhesive film (5) on the top surface and the outer circumferential surface of the flanging prepreg, lay the honeycomb core (6) on the adhesive film (5) on the outer surface of the inner skin (4), and press the circumferential bottom of the laid honeycomb core (6) against the adhesive film (5) on the top surface of the flanging prepreg. Lay the adhesive film (5) and the outer skin (7) prepreg on the honeycomb core (6) in sequence. Step 4: Lay the uniform pressure plate on the top surface and the circumferential outer wall surface of the outer skin prepreg. After laying the uniform pressure plate, make a bag. Cure and form in an autoclave according to the curing parameters of the prepreg to form a thin-walled cavity composite part with a honeycomb sandwich structure through a co-bonding process.

2. The forming method of a thin-walled cavity composite part with a honeycomb sandwich structure according to claim 1, characterized in that During the laying process of the inner skin prepreg in step 1 and during the laying process of the flanging prepreg in step 2, each layer of the inner skin prepreg is subjected to vacuum compaction; and during the laying process, the number of layers and the laying angle sequence of the prepreg are laid according to the design requirements. During the process of laying the adhesive film (5), laying the honeycomb core (6), and laying the outer skin prepreg in step 3, each layer is subjected to vacuum compaction, and the number of layers and the laying angle sequence of the prepreg are laid according to the design requirements.

3. The forming method of a thin-walled cavity composite part with a honeycomb sandwich structure according to claim 1, characterized in that In step 3, when laying the honeycomb core (6), a block-by-block splicing laying method is adopted. The splicing seam position is bonded with foam adhesive, and the corner position of the honeycomb core (6) during laying is filled and strengthened with filling adhesive.

4. The forming method of a thin-walled cavity composite part with a honeycomb sandwich structure according to claim 1, characterized in that The forming die material used is steel or ductile iron; the die body of the forming die is set as a columnar structure, and the forming die further includes: a positioning ring (8) for sleeving around the bottom circumference of the columnar structure; wherein, the cross-section of the die body of the columnar structure includes but is not limited to a circular shape, an elliptical shape, and a square shape, and the die body of the columnar structure is of equal cross-section or unequal cross-section.

5. The forming method of a thin-walled cavity composite part with a honeycomb core structure according to claim 4, characterized in that The positioning ring (8) is a segmented structure in the circumferential direction, and the bottom of the positioning ring (8) is fixedly connected to the die body of the forming die through positioning bolts.

6. A forming method of a thin-walled cavity composite part with a honeycomb sandwich structure according to any one of claims 1 to 5, characterized in that, There are embedded parts in the thin-walled cavity composite part to be formed. In the process of laying the honeycomb core (6) in step 3, the installation position of the embedded part (2) is reserved. After the laying of the honeycomb core (6) is completed, the embedded part is placed at the installation position of the embedded part (2), and foam glue is filled between the embedded part (2) and the honeycomb core (6) for strengthening according to the specified glue filling range; and a positioning hole for positioning the embedded part (2) is provided on the top surface of the die body of the forming die. When laying the adhesive film (5) and the prepreg of the outer skin (7), an opening area for avoiding the embedded part (2) is opened on the laid adhesive film (5) and the prepreg of the outer skin (7), so that the top of the embedded part (2) protrudes from the adhesive film (5) and the prepreg of the outer skin.

7. A forming method for a thin-walled cavity composite part with a honeycomb sandwich structure according to claim 6, characterized in that, The leveling plate laid in step 4 is a combined leveling plate, and the combined leveling plate includes a backing plate (9) and a thin aluminum plate. Step 4 specifically includes: Placing a backing plate (9) with the same thickness as the protruding height of the embedded part (2) on the top surface of the prepreg of the outer skin, placing a positioning template (10) on the top surface of the backing plate (9) and the embedded part (2), and fixing the positioning template (10) and the embedded part (2) on the forming die by using a positioning pin (11); after laying the thin aluminum plate on the outer circumferential wall surface of the prepreg of the outer skin (7) to make a bag, curing and forming in a autoclave according to the curing parameters of the prepreg to form a thin-walled cavity composite part with an embedded part (2).

8. A forming method for a thin-walled cavity composite part with a honeycomb sandwich structure according to claim 7, characterized in that In step 4, The thin aluminum plate is laid in a segmented splicing manner, and the splicing position is fixed with pressure-sensitive tape; and the aluminum plate laid on the outer circumferential wall surface of the prepreg of the outer skin is a thin aluminum plate with a thickness of 0.3 mm to 0.5 mm to ensure good adhesion between the thin aluminum plate and the outer surface of the prepreg of the outer skin (7).

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