A method of forming a large cell belt curvature honeycomb sandwich composite article

Abstract

The application discloses a forming method of a large-cell honeycomb sandwich composite material part, and belongs to the technical field of composite material forming. The method comprises the following steps: fixing a honeycomb core on a solidified outer skin by pre-gluing; closing the cell by laying and stacking a plate core adhesive film on the inner surface of the side of the honeycomb core facing the inner skin; using pressure-sensitive adhesive tape and a peelable layer to tightly hold the plate core adhesive film; pre-solidifying the combined part after laying and stacking the plate core adhesive film under low pressure and low vacuum; adding a layer of soft film before pre-solidification to ensure the flatness of the plate core adhesive film after solidification; laying a plate adhesive film between the pre-solidified plate core adhesive film and the un-solidified inner skin; and finally co-gluing and solidifying to obtain the honeycomb sandwich composite material part. The method solves the problems of rebound deformation, displacement and overall shrinkage of the large-curvature honeycomb core, and the problem of the depression of the inner skin and the adhesive film at the large-cell cavity.

Description

Technical Field

[0001] This invention relates to the field of composite material molding and manufacturing technology, specifically to a molding method for a large-core curved honeycomb sandwich composite material part. Background Technology

[0002] Honeycomb sandwich composite components are widely used in military and civilian aircraft, especially in structures such as fuselage doors, hatches, and the leading and trailing edges of wings. They achieve both structural weight reduction and the required load-bearing capacity. In recent years, low-density honeycomb cores with large cores (≥5mm in side length) have begun to be used, further enabling weight reduction and noise reduction in aircraft. To ensure the strength of the aerodynamic skin, honeycomb sandwich structures extensively use a pre-cured outer skin co-bonded with the honeycomb core and uncured inner skin. However, due to the lack of support from the large cores for the uncured inner skin and adhesive film during the bonding process, issues such as… Figure 1 The problem shown is that the inner skin and film sink in the core cavity, causing the inner skin fibers to bend, which affects the structural load-bearing capacity and surface quality.

[0003] Existing research indicates that pre-curing a layer of adhesive film on the outer surface of the honeycomb core before co-curing, co-bonding, or secondary bonding with the inner and outer skins can address surface quality issues to some extent. However, these methods are more suitable for planar honeycomb sandwich structures. Due to the aerodynamic requirements of aircraft, honeycomb sandwich composite parts are often designed with curved structures such as C-shapes, V-shapes, and annular shapes. Curved honeycomb cores experience significant stress after bending. Pre-curing a layer of adhesive film on the honeycomb core surface greatly increases stiffness but also makes it prone to springback deformation. This makes positioning on the outer skin difficult during bonding, and deformation can easily lead to core detachment from the skin. Furthermore, secondary bonding processes increase manufacturing costs and time, as well as the difficulty of bonding various sub-components, hindering mass production.

[0004] In the prior art, patent CN113601878B discloses a high-curvature, irregularly shaped, high-height honeycomb co-cured sandwich structure composite material and its molding method. The technical solution is as follows: a high-curvature, irregularly shaped, high-height honeycomb co-cured sandwich structure composite material and its molding method are provided. Pre-impregnated semi-cured aramid paper honeycomb is shaped and cured on a male mold to obtain a honeycomb core blank. The honeycomb core blank is placed on a female mold, and foaming adhesive is filled into the range of three to five honeycomb cells inward according to the net size outline of the honeycomb core. After the foaming adhesive is pre-cured, a stiffness-pre-reinforced honeycomb core blank is obtained and processed to the theoretical size. The outer skin, reinforcing block, and inner skin pre-impregnated pre-impregnated material are prepared by hot melt pre-impregnation, and assembled and cured with the honeycomb core and embedded parts to obtain the honeycomb co-cured sandwich structure composite material.

[0005] The above-mentioned solution employs co-curing technology, where both the inner and outer skins are in an uncured state and co-cured with the honeycomb core to prepare a sandwich structure. This primarily addresses the issues of lateral slippage and shrinkage deformation of the honeycomb core caused by insufficient lateral stiffness. However, this solution cannot solve the problems of the impact of excessively large core cell size on the surface quality of the skin, as well as the overall springback deformation and shrinkage issues of honeycomb cores with large curvature. Summary of the Invention

[0006] This invention aims to solve the problem that in the existing technology of forming large-core curved honeycomb sandwich composite materials using vacuum bag-autoclave method and co-bonding process, the uncured inner skin sinks in the core cavity during bonding, which does not meet the strength and surface quality requirements. The invention proposes a forming method for large-core curved honeycomb sandwich composite material parts.

[0007] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0008] A method for molding a large-core honeycomb sandwich composite material part with curvature, characterized in that it includes:

[0009] S1. The honeycomb core is pre-bonded to the cured outer skin for fixation;

[0010] S2. Lay a core film on the inner surface of the honeycomb core facing the inner skin to seal the core cells; and use pressure-sensitive tape and a peelable layer to firmly hold the core film.

[0011] S3. Pre-curing of the assembly after the core adhesive film is laid under low pressure and low vacuum conditions. Before pre-curing, a layer of soft film is laid to ensure the flatness of the core adhesive film after curing.

[0012] S4. Lay a sheet adhesive film between the pre-cured core film and the uncured inner skin, and then complete the co-bonding and curing to obtain a honeycomb sandwich composite material part with satisfactory surface quality.

[0013] Specifically, in one embodiment, the process of pre-bonding the honeycomb core to the cured outer skin includes the following steps:

[0014] S11. Prepare the molding mold and position the cured outer skin with the adhesive surface treated onto the molding mold.

[0015] S12. Lay the core film on the outer skin; place the prepared honeycomb core in the designated position;

[0016] S13. Vacuuming and pre-compacting are performed to bond the honeycomb core to the outer skin at room temperature. After sealing the bag, it is sent to an autoclave for pre-bonding and curing.

[0017] Specifically, in one embodiment, the pre-curing of the assembly after the core adhesive film is laid under low pressure and low vacuum conditions, and the addition of a soft film before pre-curing to ensure the flatness of the core adhesive film after curing, includes:

[0018] S31. Lay the core adhesive film and peelable cloth in sequence on the adhesive side of the inner skin of the honeycomb core, and then place another layer of soft film on the surface.

[0019] S32. Vacuuming is performed for pre-compaction, so that the honeycomb core is bonded to the core film and peelable fabric at room temperature;

[0020] S33. Place a soft film on the surface of the assembled part obtained in step S32;

[0021] S34. After sealing the bag and vacuuming it, send it into a hot autoclave for curing the honeycomb core board core film.

[0022] Specifically, in one embodiment, the process of laying a sheet-to-sheet adhesive film between the pre-cured core film and the uncured inner skin, followed by co-bonding and curing to obtain a honeycomb sandwich composite material part with satisfactory surface quality includes:

[0023] S41. Remove the bag and all auxiliary materials from the surface of the honeycomb core. Lay a layer of board-to-board adhesive film on the pre-cured board core adhesive film on the adhesive side of the inner skin of the honeycomb core.

[0024] S42. Lay the inner skin on the sheet film;

[0025] S43. Lay a layer of peelable fabric on the outer surface of the inner skin;

[0026] S44, seal the bag, and send it into a thermostatic jar for co-bonding and curing;

[0027] S45. Demolding: Remove auxiliary materials to obtain a honeycomb sandwich composite material part with satisfactory surface quality. The peelable layer can be removed before the surface coating of the composite material part is sprayed.

[0028] Specifically, in one embodiment, the outer skin, inner skin, sheet adhesive film, and core adhesive film are all made of the same resin system.

[0029] Specifically, in one embodiment, the honeycomb core is a honeycomb, aluminum alloy honeycomb, or titanium alloy honeycomb formed by impregnating para- or meta-aramid paper with phenolic resin, epoxy resin, cyanate ester resin, bismaleimide resin, polyimide resin, or modified resin thereof.

[0030] Specifically, in one embodiment, the honeycomb core is pre-bent and shaped as a whole according to the shape and size of the digital model and then milled, or it is cut into several pieces, spliced ​​together with foam adhesive into a predetermined shape, and then milled into the shape required by the digital model.

[0031] Specifically, in one embodiment, in step S13, the vacuum pressure is controlled between -0.28 bar and -0.40 bar; the autoclave pressure is between 1 and 1.8 bar; the pre-curing temperature of the adhesive film should be 25-40°C lower than the curing temperature of the adhesive film itself; and the constant temperature time is 60-100 minutes.

[0032] Specifically, in one embodiment, in step S13, before sealing the bag, edge blocks are placed at the chamfered corners of the honeycomb core as needed to prevent the honeycomb core from shrinking and collapsing laterally.

[0033] Specifically, in one embodiment, the core adhesive film and the board-to-board adhesive film should be perforated before being laid. The hole diameter should not exceed 1 mm, and the hole spacing should be controlled within the range of 10-30 mm. In step S2, the core adhesive film should extend 2-5 mm beyond the edge of the honeycomb core outline during laying. The peelable fabric should extend beyond the core adhesive film and be overlapped and fixed to the outer skin using a pressure-sensitive adhesive tape. The pressure-sensitive adhesive tape and the peelable fabric should overlap by at least 25 mm.

[0034] Specifically, in one embodiment, the PVC membrane is made by vulcanizing rubber and fabric prepreg or by curing glass cloth prepreg, with a thickness not exceeding 1.5 mm, and the PVC membrane profile matches the honeycomb core profile.

[0035] Specifically, in one embodiment, the vacuum pressure in step S32 is controlled between -0.1 bar and -0.15 bar; the autoclave pressure in step S34 should be controlled between 0.7 and 1 bar.

[0036] Specifically, in one embodiment, the adhesive film on the board completely covers the outer skin and the honeycomb core.

[0037] Specifically, in one embodiment, in step S43, the peelable layer should extend beyond the inner skin and be overlapped and fixed to the molding die using pressure-sensitive adhesive tape, with the pressure-sensitive adhesive tape and the peelable fabric overlapping by at least 25mm.

[0038] Specifically, in one embodiment, the co-bonding curing parameters in step S44 are executed according to the inner skin curing parameters.

[0039] In summary, the present invention has the following advantages:

[0040] 1. In this invention, the outer skin is first cured to ensure that the outer skin has a good aerodynamic shape. Then, the large curvature honeycomb core is pre-bonded to the cured outer skin on the side facing the outer skin for fixation, which prevents the curved honeycomb core from shifting, rebounding and shrinking in the future.

[0041] 2. This invention addresses the characteristics of large-cell curved honeycomb sandwich composite parts. First, the honeycomb core is pre-bonded to the cured outer skin for fixation, preventing subsequent springback and shrinkage deformation of the curved honeycomb core. Second, a core film is laid on the inner surface of the honeycomb core under low pressure and low vacuum conditions to seal the core. Pressure-sensitive tape and a peelable layer are used to hold the film in place. The soft film ensures the curing flatness of the core film and prevents it from sinking in the core cavity. The cured core film provides support for the core film and inner skin during subsequent bonding, solving the problem of sinking of the core film and inner skin in the large-cell cavity.

[0042] 3. In this invention, both the core of the honeycomb core inner skin adhesive side panel and the adhesive film of the panels are perforated. During curing, internal quality problems such as interlayer dispersion or delamination caused by insufficient air conduction between adhesive films can be avoided.

[0043] 4. In this invention, the inner skin is also treated with peelable fabric and pressure-sensitive tape during the curing process, which can further reduce the slippage and shrinkage of the inner skin on the honeycomb core. In addition, due to the presence of peelable fabric, the imprints of auxiliary materials such as release film and breathable felt will not appear on the surface of the large core cell honeycomb sandwich composite material after demolding, thus improving the surface quality. Furthermore, the peelable layer has a surface treatment function, and after the peelable layer is removed, no grinding treatment is required before coating spraying. Attached Figure Description

[0044] Figure 1 Schematic diagram of the inner skin of a large-core honeycomb sandwich composite component sinking in the core cavity;

[0045] Figure 2 Schematic diagram of a large-core honeycomb core with curvature pre-bonded onto the outer skin;

[0046] Figure 3 Schematic diagram of peelable cloth used to hold the adhesive film of the inner skin of the large core cell with curved honeycomb core with side bonding of the panel core.

[0047] Figure 4 Schematic diagram of the placement of the soft membrane on the inner skin side of the large-core honeycomb core with curvature;

[0048] Figure 5 Schematic diagram of the lamination of adhesive film and inner skin of large core lattice honeycomb core composite component;

[0049] Figure 6 Schematic diagram of peelable fabric used to hold the inner skin of a large-core honeycomb core composite component with curvature.

[0050] Figure 7 Schematic diagram of a large-core honeycomb core composite component with curvature;

[0051] in,

[0052] 1. Outer skin, 2. Inner skin, 3. Honeycomb core, 4. Core film, 5. Molding mold, 6. Honeycomb core edge stop, 7. Peelable fabric, 8. Pressure-sensitive tape, 9. Soft mold, 10. Board film. Detailed Implementation

[0053] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention. The terms "first," "second," etc., used in the specification, claims, and accompanying drawings are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, or apparatuses.

[0054] Example 1

[0055] This invention provides a molding method for a large-core curved honeycomb sandwich composite material part. The method involves pre-bonding the large-curvature honeycomb core 3 to a cured outer skin 1, achieving single-sided fixation and solving the problems of springback deformation, displacement, and overall shrinkage of the large-curvature honeycomb core 3. Then, a pre-cured core film 4 is applied to the inner surface of the honeycomb core 3 to achieve core cell sealing and overall surface stiffening, providing support for the subsequent core film 10 and inner skin 2, thus solving the problem of sagging of the inner skin 2 and film at the large-core cavities. The method includes the following steps:

[0056] S1. The honeycomb core 3 is pre-bonded onto the cured outer skin 1 for fixation;

[0057] S2. Lay a core film 4 on the inner surface of the honeycomb core 3 facing the inner skin 2 to seal the core cell; and use pressure-sensitive tape 8 and a peelable layer to tighten the core film 4.

[0058] S3. Pre-curing of the assembly after laying the core adhesive film 4 under low pressure and low vacuum conditions. Before pre-curing, a layer of soft film is added to ensure the flatness of the core adhesive film 4 after curing.

[0059] S4. Lay a board adhesive film 10 between the pre-cured core adhesive film 4 and the uncured inner skin 2, and then complete the co-bonding and curing to obtain a honeycomb sandwich composite material part with satisfactory surface quality.

[0060] In the above molding process, curing the outer skin 1 first can ensure that the outer skin 1 has a good aerodynamic shape. Then, the large curvature honeycomb core 3 is pre-bonded to the cured outer skin 1 on the side facing the outer skin 1 for fixation, which prevents the curved honeycomb core 3 from shifting, rebounding and shrinking in the future.

[0061] On the pre-bonded assembly of the large curvature honeycomb core 3 and the outer skin 1, two layers of adhesive film are laid on the inner surface of the large core honeycomb core 3 facing the inner skin 2: the first layer is the core adhesive film 4, and the second layer is the board adhesive film 10.

[0062] The first layer of core adhesive film 4 is secured using pressure-sensitive adhesive tape 8 and a peelable layer. This core adhesive film 4 is pre-cured under low pressure and low vacuum conditions. Before pre-curing, a soft film is laid to ensure flatness after curing, achieving the effects of increasing the rigidity of the inner surface of the honeycomb core 3 and sealing the core cells. It also supports the uncured second layer of core adhesive film 10 and the inner skin 2, thus solving the problem of sagging of the core adhesive film 10 and the inner skin 2 in the large core cell cavities. The second layer of core adhesive film 10 serves to bond the first pre-cured core adhesive film 4 and the uncured inner skin 2 to the inner surface of the honeycomb core 3.

[0063] Example 2

[0064] As a preferred embodiment of the present invention, based on Embodiment 1, the operation of pre-bonding the honeycomb core 3 to the cured outer skin 1 for fixation specifically includes:

[0065] Step 1: Prepare molding mold 5 and position the cured outer skin 1 with the adhesive surface treated onto molding mold 5;

[0066] Step 2: Mill or manually process the honeycomb core 3 according to the design model and perform dehumidification treatment.

[0067] The honeycomb core 3 should be pre-bent and shaped as a whole according to the shape and size of the digital model before milling, or cut into several pieces, spliced ​​together with foam adhesive into a predetermined shape, and then milled into the shape required by the digital model.

[0068] Step 3: Lay the core adhesive film 4 on the outer skin 1 according to the laser projection;

[0069] Step 4: Place the honeycomb core 3 from Step 2 into the designated position according to the laser projection;

[0070] Step 5: Pre-compact the honeycomb core 3 with the outer skin 1 by drawing a vacuum, so that the honeycomb core 3 and the outer skin 1 are bonded together at room temperature; the vacuum pressure should be controlled between -0.28 bar and -0.40 bar.

[0071] Step 6: Seal the bag and send it into a hot autoclave for pre-bonding and curing. Before sealing the bag, edge blocks can be placed at the chamfered corners of the honeycomb core 3 as needed to prevent the honeycomb core 3 from shrinking and collapsing laterally. The blocks are bolted to the molding mold 5.

[0072] In this step, the initial vacuum pressure should be controlled between -0.28 bar and -0.40 bar, the autoclave pressure should be between 1 and 1.8 bar, the pre-curing temperature of the adhesive film should be 25-40°C lower than the curing temperature of the adhesive film itself, and the constant temperature time should be 60-100 minutes.

[0073] Example 3

[0074] As a preferred embodiment of the present invention, based on embodiment 1, this embodiment further includes perforation treatment on the first layer of pre-cured core adhesive film 4 and board adhesive film 10 on the adhesive side of the inner skin 2 of the honeycomb core 3. This can avoid internal quality problems such as interlayer diffusion or delamination caused by insufficient air conduction between adhesive films during curing.

[0075] Before laying the core adhesive film 4 and the board adhesive film 10, they should be perforated. The hole diameter should not exceed 1mm and the hole spacing should be controlled within the range of 10-30mm. When laying, the core adhesive film 4 should extend 2-5mm beyond the outline edge of the honeycomb core 3. The peelable fabric 7 should extend beyond the core adhesive film 4 and should be overlapped and fixed to the outer skin 1 using a pressure-sensitive adhesive tape 8. The pressure-sensitive adhesive tape 8 and the peelable fabric 7 should overlap by at least 25mm.

[0076] Example 4

[0077] As a preferred embodiment of the present invention, based on Embodiment 1, the assembly after the core adhesive film 4 is laid is further pre-cured under low pressure and low vacuum conditions. Before pre-curing, a soft film is laid to ensure the flatness of the core adhesive film 4 after curing, including the following steps:

[0078] Step 1: Lay the honeycomb core 3 upper core adhesive film 4 and peelable fabric 7 sequentially on the adhesive side of the inner skin 2 of the honeycomb core 3;

[0079] Step 2: Pre-compact the honeycomb core 3 by drawing a vacuum, so that the core film 4 and the peelable fabric 7 are bonded together at room temperature; the vacuum pressure should be controlled between -0.1 bar and -0.15 bar.

[0080] Step 3: Place a soft film on the surface of the assembled part obtained in Step 2; the soft film can be made of rubber + fabric prepreg vulcanized or glass cloth prepreg cured, and the thickness should not exceed 1.5mm. The shape of the soft film should match the shape of the honeycomb core 3.

[0081] Step 4: Seal the bag, vacuum and compact it, then send it into an autoclave for the curing of the honeycomb core 3 and the core film 4. The vacuum pressure should be controlled between -0.1 bar and -0.15 bar, the autoclave pressure should be controlled between 0.7 and 1 bar, and the film should be fully cured according to its curing temperature.

[0082] Example 5

[0083] As a preferred embodiment of the present invention, based on Embodiment 1, a plate-to-plate adhesive film 10 is further laid between the pre-cured core adhesive film 4 and the uncured inner skin 2, and then co-bonding and curing are completed to obtain a honeycomb sandwich composite material part with satisfactory surface quality. The specific operation steps are as follows:

[0084] Step 1: Remove the bag and all auxiliary materials from the surface of the honeycomb core 3. Lay a layer of board-to-board adhesive film 10 on the pre-cured core adhesive film 4 on the adhesive side of the inner skin 2 of the honeycomb core 3. The board-to-board adhesive film 10 should completely cover the outer skin 1 and the honeycomb core 3.

[0085] Step 2: Lay the inner skin 2 on the liner film 10 according to the number and angle of the digital model;

[0086] Step 3: Lay a layer of peelable fabric 7 on the outer surface of the inner skin 2; the peelable fabric 7 should extend beyond the inner skin 2 and be overlapped and fixed to the molding mold 5 using pressure-sensitive tape 8, with the pressure-sensitive tape 8 and the peelable fabric 7 overlapping by at least 25mm.

[0087] During the stacking process of steps one to three above, vacuuming can be performed for pre-compaction according to the actual situation. The vacuum pressure should be controlled between -0.28 bar and -0.40 bar.

[0088] Step 4: Seal the bag and send it into an autoclave for co-bonding and curing; the co-bonding and curing parameters shall be the same as those for the inner skin 2.

[0089] Step 5: Demolding, removing auxiliary materials, and obtaining a honeycomb sandwich composite material part with satisfactory surface quality. The peelable fabric 7 can be retained until the surface coating of the composite part is sprayed before removal.

[0090] Example 6

[0091] This embodiment is based on any one of the above embodiments one to five.

[0092] In this implementation plan, the outer skin 1, inner skin 2, sheet, and core film 4 should be made of the same resin system.

[0093] The honeycomb core 3 is formed by impregnating para- or meta-aramid paper with phenolic resin, epoxy resin, cyanate ester resin, bismaleimide resin, polyimide resin, or modified resin during the molding of honeycomb sandwich composite parts. It can be a honeycomb, aluminum alloy honeycomb, or titanium alloy honeycomb, and its structure has a certain curvature. This method is applicable to non-planar honeycomb cores 3, with the maximum curvature reaching the bending limit of the honeycomb core 3. In the examples, the side length of the large core cells is between 3-5.5 mm.

[0094] Example 7

[0095] The following practical process will fully illustrate the molding method of a large-core curved honeycomb sandwich composite material part according to the present invention.

[0096] In this embodiment, both the skin and the film resin system are cured at 180±5℃, and the Nomex aramid paper honeycomb has a core cell side length of 5.5.

[0097] Step 1: After curing, inspecting, and roughening the surface of the outer skin 1, position it onto the molding mold 5;

[0098] Step 2: After dehumidifying the honeycomb core blank, process it to the product outline using CNC milling or manual cutting and polishing according to the digital model;

[0099] Step 3: Use a laser projector to project the outline of the core adhesive film 4 (such as FM300K) and then lay it up;

[0100] Step 4: After projecting the outline of the honeycomb core 3 onto the outer skin 1 using a laser projector, place the honeycomb core 3 into position;

[0101] Step 5: Seal the bag at room temperature using a non-porous release film, breathable felt, and vacuum bag, and apply a vacuum pressure of -0.33 bar for pre-compactment for ≥10 min;

[0102] Step 6: Place in an autoclave for curing. Curing parameters: initial vacuum setting -0.33 bar, autoclave pressure setting 1.5 bar, heating and cooling rate setting 1-3℃ / min, pre-bonding curing temperature 145℃, constant temperature for 90 min, and remove from the autoclave after the temperature drops to 60℃.

[0103] Step 7: Remove the bag and all auxiliary materials;

[0104] Step 8: Use a punching machine to punch holes in the core film 4 of the honeycomb core 3, with a hole diameter of 1mm and a hole spacing of 20mm.

[0105] Step 9: Lay the core adhesive film 4 described in Step 8 onto the honeycomb core 3, extending 2-5mm beyond the edge of the honeycomb core 3;

[0106] Step 10: Lay a layer of peelable fabric 7 (brand name such as Diatex 1500, etc.) on top of Step 9, and use pressure-sensitive tape 8 to stick and fix the peelable fabric 7 to the outer skin 1. The pressure-sensitive tape 8 and the peelable fabric 7 should overlap by at least 25mm.

[0107] Step 11: After placing the baffle on the side of the honeycomb core 3, seal the combined component of the honeycomb and outer skin 1 at room temperature using a non-porous isolation membrane, breathable felt and vacuum bag, and apply a vacuum pressure of -0.1 bar for pre-compactment for ≥10 min;

[0108] Step 12: Unpack the bag and place the soft film prepared from vulcanized rubber and fabric onto the honeycomb core 3 with the core film 4 and the peelable layer. Seal the bag at room temperature using a non-porous isolation film, breathable felt and vacuum bag, and apply a vacuum pressure of -0.15 bar for pre-compactment for ≥10 min.

[0109] Step 13: Place the product into an autoclave for curing. Curing parameters: initial vacuum setting -0.15 bar, autoclave pressure setting 0.8 bar, heating and cooling rate setting 1-3℃ / min, curing temperature 180℃, constant temperature for 150 min, and remove the product from the autoclave after the temperature drops to 60℃.

[0110] Step Fourteen: Remove from the can and remove auxiliary materials (including the soft film and peelable layer). Use a punching machine to punch holes in the adhesive film 10 of the upper plate of the honeycomb core 3 (such as FM300M), with a hole diameter of 1mm and a hole spacing of 20mm.

[0111] Step 15: Lay a layer of perforated board adhesive film 10 (such as FM300M) on the cured core film 4 of the honeycomb core 3, and pre-compact it at room temperature for ≥10 min under a vacuum pressure of -0.33 bar.

[0112] Step 16: Lay out the inner skin 2 (prepreg brand such as CYCOM 970 / PWC T300, etc.) and pre-compact it every 3-5 layers. The pre-compacting vacuum and time are the same as in Step 15.

[0113] Step 17: Lay a layer of peelable fabric 7 (such as Diatex 1500) on the surface of the inner skin 2, and use pressure-sensitive tape 8 to stick and fix the peelable fabric 7 to the molding mold 5. The pressure-sensitive tape 8 and the peelable fabric 7 should overlap by at least 25mm.

[0114] Step 18: Seal the bag and cure it in an autoclave. Curing parameters: initial vacuum setting -0.33 bar, can pressure setting 3 bar, heating and cooling rate setting 1-3℃ / min, curing temperature 180℃, constant temperature for 120 min, and remove from the can after the temperature drops to 60℃.

[0115] Step 19: Demolding, removing auxiliary materials, and removing the peelable layer before spraying the coating will yield a large-core curved honeycomb sandwich composite material part that meets the quality requirements.

[0116] Although specific embodiments of the present invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

[0117] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A molding method for a large-core curved honeycomb sandwich composite material part, characterized in that, include: S1. The honeycomb core (3) is pre-bonded to the cured outer skin (1) for fixation; S2. Lay a core film (4) on the inner surface of the honeycomb core (3) facing the inner skin (2) to seal the core cell; and use pressure-sensitive tape (8) and a peelable layer to tighten the core film (4); S3. Pre-curing of the assembly after the core adhesive film (4) is laid under low pressure and low vacuum conditions. Before pre-curing, a layer of soft film is laid to ensure the flatness of the core adhesive film (4) after curing. S4. Lay a board-board adhesive film (10) between the pre-cured core adhesive film (4) and the uncured inner skin (2), and then complete the co-bonding and curing to obtain a honeycomb sandwich composite material part with satisfactory surface quality.

2. The molding method for a large-core honeycomb sandwich composite material part with curvature according to claim 1, characterized in that, The process of pre-bonding the honeycomb core (3) to the cured outer skin (1) includes the following steps: S11. Prepare the molding mold (5) and position the cured and glued surface treated outer skin (1) onto the molding mold (5); S12. Lay the laminated core film (4) on the outer skin (1); place the prepared honeycomb core (3) in the designated position; S13. Vacuum and pre-compact the honeycomb core (3) and the outer skin (1) at room temperature, seal the bag and send it into the autoclave for pre-bonding and curing.

3. The molding method for a large-core curved honeycomb sandwich composite material part according to claim 1, characterized in that, The pre-curing of the assembly after the core adhesive film (4) is laid under low pressure and low vacuum conditions, and the addition of a soft film before pre-curing to ensure the flatness of the core adhesive film (4) after curing, includes: S31. Lay the laminated core adhesive film (4) and peelable cloth (7) sequentially on the adhesive side of the inner skin (2) of the honeycomb core (3), and then place another layer of soft film on the surface. S32. Vacuuming is performed for pre-compaction, so that the honeycomb core (3) is bonded to the core film (4) and the peelable fabric (7) at room temperature; S33. Place a soft film on the surface of the assembled part obtained in step S32; S34. After sealing the bag and vacuuming and compacting it, send it into the autoclave for the honeycomb core (3) and the core film (4) to be cured.

4. The molding method for a large-core curved honeycomb sandwich composite material part according to claim 1, characterized in that, The process of laying a sheet adhesive film (10) between the pre-cured core adhesive film (4) and the uncured inner skin (2), and then completing co-bonding and curing to obtain a honeycomb sandwich composite material part with satisfactory surface quality includes: S41. Remove the bag and remove all auxiliary materials from the surface of the honeycomb core (3). Lay a layer of board film (10) on the pre-cured board core film (4) on the adhesive side of the inner skin (2) of the honeycomb core (3). S42. Lay the inner skin (2) on the sheet film (10). S43. Lay a layer of peelable fabric (7) on the outer surface of the inner skin (2); S44, seal the bag, and send it into a thermostatic jar for co-bonding and curing; S45. Demolding: Remove auxiliary materials to obtain a honeycomb sandwich composite material part with satisfactory surface quality. The peelable layer can be removed before the surface coating of the composite material part is sprayed.

5. The molding method for a large-core curved honeycomb sandwich composite material part according to claim 1, characterized in that, The outer skin (1), inner skin (2), sheet adhesive film (10), and core adhesive film (4) are all made of the same resin system.

6. A molding method for a large-core curved honeycomb sandwich composite material part according to claim 1 or 2, characterized in that, The honeycomb core (3) is a honeycomb, aluminum alloy honeycomb, or titanium alloy honeycomb formed by impregnating para- or meta-aramid paper with phenolic resin, epoxy resin, cyanate ester resin, bismaleimide resin, polyimide resin, and their modified resins.

7. A molding method for a large-core curved honeycomb sandwich composite material part according to claim 1 or 2, characterized in that, The honeycomb core (3) is pre-bent and shaped according to the shape and size of the digital model and then milled, or cut into several pieces and spliced ​​together with foam to form a predetermined shape before being milled into the shape required by the digital model.

8. The molding method for a large-core honeycomb sandwich composite material part with curvature according to claim 2, characterized in that, In step S13, the vacuum pressure is controlled between -0.28 bar and -0.40 bar; the autoclave pressure is between 1 and 1.8 bar; the pre-curing temperature of the adhesive film should be 25-40°C lower than the curing temperature of the adhesive film itself; and the constant temperature time is 60-100 min.

9. A molding method for a large-core honeycomb sandwich composite material part with curvature according to claim 2, characterized in that, In step S13, before sealing the bag, edge blocks are placed at the chamfer of the honeycomb core (3) as needed to prevent the honeycomb core (3) from shrinking and collapsing laterally.

10. The molding method for a large-core curved honeycomb sandwich composite material part according to claim 1, characterized in that, Before the core adhesive film (4) and the board adhesive film (10) are laid, they should be punched. The hole diameter should not exceed 1 mm and the hole spacing should be controlled within the range of 10-30 mm. In step S2, when laying, the core adhesive film (4) should extend 2-5 mm beyond the outline edge of the honeycomb core (3). The peelable fabric (7) should extend beyond the core adhesive film (4) and should be overlapped and fixed on the outer skin (1) using a pressure-sensitive adhesive tape (8). The pressure-sensitive adhesive tape (8) and the peelable fabric (7) should overlap by at least 25 mm.

11. The molding method for a large-core honeycomb sandwich composite material part with curvature according to claim 1, characterized in that, The soft membrane is made of rubber + fabric prepreg vulcanized or glass cloth prepreg cured, with a thickness not exceeding 1.5 mm. The soft membrane surface matches the honeycomb core (3) surface.

12. The molding method for a large-core honeycomb sandwich composite material part with curvature according to claim 3, characterized in that, The vacuum pressure in step S32 is controlled between -0.1 bar and -0.15 bar; the autoclave pressure in step S34 should be controlled between 0.7 and 1 bar.

13. The molding method for a large-core curved honeycomb sandwich composite material part according to claim 1, characterized in that, The liner film (10) completely covers the outer skin (1) and the honeycomb core (3).

14. The molding method for a large-core honeycomb sandwich composite material part with curvature according to claim 1, characterized in that, In step S43, the peelable layer should extend beyond the inner skin (2) and be fixed to the molding mold (5) by overlapping with pressure-sensitive tape (8). The pressure-sensitive tape (8) and the peelable fabric (7) should overlap by at least 25 mm.

15. The molding method for a large-core honeycomb sandwich composite material part with curvature according to claim 1, characterized in that, The co-bonding curing parameters in step S44 shall be executed according to the curing parameters of the inner skin (2).

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