A process for preparing a honeycomb preform

Abstract

This invention relates to the field of composite material preparation technology, specifically disclosing a preparation process for a honeycomb preform, comprising the following steps: Step S1: Preparing two honeycomb preforms of different thicknesses, namely honeycomb preform one and honeycomb preform two, both of which are three-layer composite structures, consisting of a core layer, an adhesive layer, and a reinforcing layer from the inside out; Step S2: Bonding honeycomb preform one and honeycomb preform two together with an adhesive film to obtain a double preform assembly; Step S3: Applying a skin to the outer layer of the double preform assembly, and after overall curing, trimming, and testing, obtaining a complete honeycomb preform. The core layer of the honeycomb preform uses aerospace-grade aramid paper honeycomb with a regular hexagonal cell shape, a cell side length of 3-5 mm, a thickness of 10 mm, and a density of 30-50 kg / m³, to solve the problems of high processing loss, inaccurate dimensions, and poor dimensional stability of finished products in existing processes.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology, and in particular to a process for preparing a honeycomb preform. Background Technology

[0002] Honeycomb preforms, as a lightweight, high-strength, and structurally stable core material for composite structural components, are widely used in high-end manufacturing fields such as aerospace, high-end rail transportation, precision instruments, and new energy equipment due to their excellent comprehensive properties, including weight reduction, load-bearing capacity, impact resistance, and corrosion resistance. These applications place stringent requirements on the structural precision, interlayer bonding reliability, mechanical property consistency, and lightweighting level of honeycomb preforms. Especially in the aerospace field, the quality of the preform directly determines the service safety and lifespan of the final structural component, making the scientific and rational fabrication process a key factor restricting product performance improvement.

[0003] Currently, existing honeycomb prefabrication processes are mostly based on a single-thickness honeycomb core, formed by laying single or multiple reinforcing layers and skins. This approach faces numerous technical bottlenecks and application limitations. On the one hand, a single-thickness honeycomb core cannot meet the personalized requirements of high-end equipment for structural functional layering and thickness adaptation. In some complex working conditions, it is necessary to achieve thickness adjustment by splicing multiple single-thickness prefabricated sections. However, stress concentration and weak bonding are prone to occur at the splicing points, leading to a decrease in the overall load-bearing capacity of the structure. Furthermore, the splicing process is cumbersome, significantly reducing manufacturing efficiency and increasing production costs.

[0004] On the other hand, existing precast structures often use ordinary epoxy adhesives or carrier-free adhesive films for interlayer bonding. It's difficult to balance the solids content, bond strength, and high-temperature resistance of these adhesive films, leading to defects such as interlayer delamination, voids, and bubbles. The bonding reliability between the core layer and the reinforcing layer, and at the joints of the precast structures, is particularly insufficient, severely impacting the overall structural stability and mechanical properties of the precast structure. Furthermore, the current process often involves separate, independent operations for laying the core layer, reinforcing layer, and skin, resulting in poor coordination between these steps and difficulty in controlling laying accuracy. This easily leads to problems such as interlayer misalignment, skin wrinkles, and excessive dimensional deviations, resulting in a low finished product yield.

[0005] In addition, the reinforcement layers of existing honeycomb prefabricated structures mostly use randomly laid or unidirectional ordinary fiber materials, which have insufficient precision in controlling the fiber volume fraction, making it difficult to effectively improve the overall stiffness, tensile strength and deformation resistance of the prefabricated structure; the combination method between the outer skin and the main body of the prefabricated structure is not reasonable enough, and problems such as loose adhesion and poor surface flatness are prone to occur after the skin is laid, which cannot give full play to the protective and reinforcing role of the skin and limit the adaptability of the prefabricated structure in high-end scenarios.

[0006] Therefore, a new process for preparing honeycomb preforms is proposed to solve the problems of high processing loss, inaccurate dimensions, and poor dimensional stability of finished products in existing processes. Summary of the Invention

[0007] The purpose of this invention is to provide a process for preparing a honeycomb preform to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A process for preparing a honeycomb preform includes the following steps: Step S1: Prepare two honeycomb prefabricated panels with different thicknesses, namely honeycomb prefabricated body one and honeycomb prefabricated body two. Both honeycomb prefabricated body one and honeycomb prefabricated body two are three-layer composite structures, consisting of a core layer, an adhesive layer and a reinforcing layer from the inside out. Step S2: Adhesive film is used to bond the first honeycomb preform and the second honeycomb preform to obtain a double preform assembly; Step S3: A skin is laid on the outer layer of the entire double prefabricated assembly. After overall curing, trimming and testing, a complete honeycomb prefabricated body is obtained.

[0009] Preferably, the core layer of the honeycomb preform is made of aerospace-grade aramid paper honeycomb with a regular hexagonal cell shape, a cell side length of 3-5 mm, a thickness of 10 mm, and a density of 30-50 kg / m³.

[0010] Preferably, the core layer of the second honeycomb prefabricated body is made of aerospace-grade aramid paper honeycomb with a regular hexagonal cell shape, a cell side length of 3-5mm, a thickness of 6.2mm, a density of 30-50kg / m³, and the same material as the core layer.

[0011] Preferably, both the first adhesive layer of the honeycomb preform and the second adhesive layer of the honeycomb preform are epoxy films with a carrier, the carrier being a polyester film, the film thickness being 0.1 mm, the solid content being ≥98%, and the adhesive strength being ≥15 MPa.

[0012] Preferably, the first reinforcing layer of the first honeycomb preform and the second reinforcing layer of the second honeycomb preform are both unidirectional carbon fiber strips laid in the 0° direction, with a carbon fiber volume fraction of 60%-70% and a thickness of 0.1mm. The laying surface has uniform density and is free of wrinkles and damage.

[0013] Preferably, in step S2, the adhesive film is a high-temperature resistant epoxy film with a thickness of 0.15-0.25 mm, a solid content of ≥98%, an adhesive strength of ≥18 MPa, a high temperature resistance of ≥120℃, and is compatible with the materials of adhesive layer 102 and adhesive layer 202.

[0014] Preferably, in step S3, the outer skin is made of plain weave bidirectional carbon fiber fabric with a carbon fiber volume fraction of 65%-75%, a thickness of 0.3-0.6 mm, uniform surface density, and no damage, skipped stitches, or wrinkles.

[0015] Preferably, in the preparation process of both the first and second honeycomb preforms, a layer-by-layer laying, vacuum sealing, and gradient curing method is adopted. The gradient curing procedure is as follows: first, the temperature is raised to 80℃ and held for 1 hour, and then raised to 100℃ at a rate of 5-10℃ / h and held for 2 hours. During the curing process, the temperature fluctuation error is ≤±2℃, and the vacuum degree is maintained at -0.08~-0.10MPa.

[0016] Preferably, in step S2, the curing procedure after the two preforms are bonded is as follows: heat to 90°C and hold for 1.5 hours, then heat to 110°C and hold for 2.5 hours. During the curing process, the vacuum degree is maintained at -0.08~-0.10MPa, and the temperature and vacuum degree are monitored in real time.

[0017] Preferably, in step S3, the overall curing procedure after the outer skin is laid is as follows: first, the temperature is raised to 85℃ and kept at that temperature for 1 hour, then raised to 105℃ at a rate of 5℃ / h and kept at that temperature for 2 hours, and finally raised to 120℃ and kept at that temperature for 3 hours. During the curing process, the temperature fluctuation error is ≤±2℃, and the vacuum degree is maintained at -0.08~-0.10MPa. When the finished product is inspected, the dimensional accuracy error is ≤±0.5mm, and there is no peeling or gaps between the layers.

[0018] The beneficial effects of this invention are: By pre-curing the honeycomb core layer and composite layer, the hardness of the honeycomb structure is effectively enhanced, avoiding problems such as honeycomb collapse and damage during subsequent processing, greatly improving the machinability of the honeycomb prefabricated panel, and reducing processing difficulty and processing loss. Meanwhile, by adopting a process of secondary carbon fiber composite and batch curing, the precast panel preparation and overall curing are carried out in separate steps, which effectively releases the internal stress generated by each layer of material during the curing process, reduces the amount of deformation of the precast panel during the curing process, ensures the accuracy of the precast body size, further improves the dimensional stability of the finished product, and reduces the rework problem caused by dimensional deviation. Attached Figure Description

[0019] Figure 1 This is a front view of a prefabricated honeycomb structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal structure of a prefabricated honeycomb structure according to an embodiment of the present invention; Figure 3 This is a front view of the prefabricated honeycomb structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the internal structure of the prefabricated honeycomb body II according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the complete honeycomb prefabricated structure according to an embodiment of the present invention.

[0020] In the figure: 1. Honeycomb prefabricated body one; 101. Core layer one; 102. Adhesive layer one; 103. Reinforcing layer one; 2. Honeycomb prefabricated body two; 201. Core layer two; 202. Adhesive layer two; 203. Reinforcing layer two. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Reference Figures 1-5 A process for preparing a honeycomb prefabricated structure is disclosed. This process requires first preparing two honeycomb prefabricated panels of different thicknesses, denoted as honeycomb prefabricated structure 1 and honeycomb prefabricated structure 2, respectively. Both honeycomb prefabricated panels are three-layer composite structures, consisting of a core layer, an adhesive layer, and a reinforcing layer from the inside out, with each layer working synergistically. Subsequently, the two prefabricated panels are bonded together, and a skin is applied to the outer layer to form a complete honeycomb prefabricated structure. Details are as follows: The honeycomb prefabricated body-1 is a three-layer composite structure, consisting of a core layer-101, an adhesive layer-102, and a reinforcing layer-103 from the inside out, serving as the first functional layer of the overall structure, wherein: The core layer 101 is made of aerospace-grade aramid paper honeycomb with regular hexagonal cell shape, a cell side length of 3-5mm, a thickness of 10mm, and a density of 30-50kg / m³. It has excellent lightweight, high strength, impact resistance, and corrosion resistance properties. As the core load-bearing and weight-reducing base layer of the precast structure, it can effectively reduce the overall structural weight while ensuring structural stability.

[0023] The adhesive layer 102 is made of a carrier epoxy film, the carrier being a polyester film. The film thickness is 0.1 mm, the solid content is ≥98%, and the adhesive strength is ≥15 MPa (tested at room temperature of 25℃). It is uniformly adhered between the core layer 101 and the reinforcing layer 103. Its function is to achieve a tight and stable bond between the core layer 101 and the reinforcing layer 103, prevent interlayer delamination, and improve the overall bonding performance of the honeycomb preform 1.

[0024] The reinforcing layer 103 is made of unidirectional carbon fiber tape laid in the 0° direction. The carbon fiber volume fraction is 60%-70%, the thickness is 0.1mm, the laying surface has uniform density, no wrinkles, and no damage. It is used to significantly improve the overall stiffness, tensile strength and deformation resistance of the honeycomb prefabricated body 1.

[0025] The second honeycomb prefabricated body 2 has the same structure as the first honeycomb prefabricated body 1, including a second core layer 201, a second adhesive layer 202, and a second reinforcing layer 203, differing only in the thickness of the core layer. It serves as the second functional layer of the overall structure, wherein: The second core layer 201 uses aerospace-grade aramid paper honeycomb of the same specifications as the first core layer 101. The honeycomb cell shape is regular hexagonal, the cell side length is 3-5mm, the thickness is 6.2mm, and the density is 30-50kg / m³. This ensures that the material is consistent with the honeycomb prefabricated body 1 and the performance is matched. At the same time, the thickness difference realizes the functional layering or thickness adaptation requirements of the overall structure.

[0026] The second adhesive layer 202 has the same specifications as the first adhesive layer 102. It is made of epoxy film with a carrier, the carrier is a polyester film, the film thickness is 0.1mm, the solid content is ≥98%, and the adhesive strength is ≥15MPa (tested at room temperature of 25℃). It is used to achieve tight bonding between the second core layer 201 and the second reinforcement layer 203.

[0027] The second reinforcement layer 203 is identical in specifications to the first reinforcement layer 103. It uses unidirectional carbon fiber tape laid in the 0° direction, with a carbon fiber volume fraction of 60%-70% and a thickness of 0.1mm. The laying surface has uniform density, no wrinkles, and no damage, which improves the overall stiffness and strength of the second honeycomb prefabricated body 2.

[0028] After the honeycomb preform 1 and the honeycomb preform 2 are processed, adhesive layer 102 and adhesive layer 202 are bonded together. A high-temperature resistant epoxy film is selected, which is compatible with the material of adhesive layer 102 and adhesive layer 202. The film thickness is 0.15-0.25mm, the solid content is ≥98%, the bonding strength is ≥18MPa (tested at room temperature of 25℃), and the high temperature resistance is ≥120℃. This is used to achieve a tight bond between the honeycomb preform 1 and the honeycomb preform 2, ensuring that the honeycomb preform 1 and the honeycomb preform 2 are firmly bonded, without interlayer peeling or gaps, thus ensuring the integrity and load-bearing performance of the overall structure.

[0029] The outer skin is made of plain-weave bidirectional carbon fiber fabric with a carbon fiber volume fraction of 65%-75% and a thickness of 0.3-0.6mm. It has a uniform surface density, no damage, no skipped stitches, and no wrinkles. After installation, it can significantly improve the surface flatness, impact resistance, and overall protective performance of the overall honeycomb prefabrication, while further enhancing the structural rigidity and tensile strength, making it suitable for the surface quality and structural requirements of high-end scenarios.

[0030] A method for preparing a honeycomb preform is provided based on the above preparation steps. This fabrication process involves first preparing a double-thickness honeycomb prefabricated panel → bonding the double prefabricated panels → then applying the outer skin layer. The entire process employs layer-by-layer application, vacuum sealing, and gradient curing to ensure tight bonding, no air bubbles, and no defects in each layer. The specific steps are as follows: (a) Preparation for tiling: 1. Prepare a flat, clean tempered glass plate. The glass size should be 10-15cm larger than the final precast body size. The surface should be free of scratches, stains, and protrusions to ensure that the laying base is flat. 2. Wipe the surface of the glass plate with anhydrous ethanol to remove dust, oil and impurities. After air drying, evenly lay a layer of high-temperature resistant release cloth on the glass plate. The release cloth should be laid flat, without wrinkles or deviation, and completely cover the glass plate laying area to ensure easy demolding after curing without damaging the surface of the precast body. 3. Cut the core layer 101, core layer 201, adhesive layer 102, adhesive layer 202, reinforcement layer 103, reinforcement layer 203, adhesive film, and outer skin precisely according to the design dimensions. The cutting accuracy error should be ≤ ±0.5mm to ensure that the dimensions of each layer match. After cutting, remove burrs and excess corners from the material edges.

[0031] Existing honeycomb prefabricated panels are mostly double-layer structures of honeycomb core and skin, without an independent reinforcing layer. This invention, however, designs a core layer, an adhesive layer and a reinforcing layer for each honeycomb prefabricated panel. The reinforcing layer uses unidirectional carbon fiber tape in the 0° direction, which gives the prefabricated panel itself high rigidity and high tensile strength, breaking the conventional concept that the skin alone bears the strength.

[0032] (II) Preparation of double-thickness honeycomb prefabricated panels: honeycomb prefabricated body 1 and honeycomb prefabricated body 2 are prepared respectively; 1. Preparation of the honeycomb preform 1: Using the release cloth on the glass plate as the base layer, first lay the core layer 101, ensuring that the core layer 101 is laid flat, without deviation or damage, and the surface is free of dust; evenly lay the adhesive layer 102 on the upper surface of the core layer 101, the adhesive layer 102 completely covers the surface of the core layer 101, without omissions or overlaps, and is tightly bonded; lay the reinforcing layer 103 on the upper surface of the adhesive layer 102, the reinforcing layer 103 is precisely laid in the 0° direction, and during the laying process, use a special roller to gently roll it to remove the air between the layers, ensuring that the reinforcing layer 103 and the adhesive layer 102 are tightly bonded, without bubbles or wrinkles; after the laying is completed, cover the outermost layer of the reinforcing layer 103 with a release film.

[0033] 2. Preparation of the second honeycomb prefabricated body: The same laying process as the first honeycomb prefabricated body is adopted, except that the first core layer 101 is replaced with the second core layer 201 with a thickness of 6.2mm. The laying requirements and operation specifications of the other layers are the same as those of the prefabricated body 1. After laying, the isolation film is covered.

[0034] 3. Simultaneous Curing of Two Preforms: The laid honeycomb preform 1 and honeycomb preform 2 are respectively sealed with high-temperature resistant vacuum bags (sealing method is the same as in subsequent steps), and simultaneously sent into the oven for curing according to the preset gradient curing program: first, the temperature is raised to 80℃ and held for 1 hour (preheating stage, to ensure that the adhesive film is uniformly softened and initially bonded); then, the temperature is slowly raised to 100℃ at a rate of 5-10℃ / h and held for 2 hours (main curing stage, to ensure that the epoxy adhesive film is completely cured); during the curing process, the temperature and vacuum degree inside the oven are monitored in real time, the temperature fluctuation error is ≤±2℃, the vacuum degree is maintained at -0.08~-0.10MPa, and there must be no air leakage or pressure drop.

[0035] 4. Cooling and Demolding: After curing, turn off the oven heating switch and keep the vacuum pump running for 30 minutes. Then turn off the vacuum pump and leave the honeycomb preform 1 and the honeycomb preform 2 in the oven to cool naturally to room temperature (25±5℃). After cooling, remove the vacuum bag film and the isolation film, and gently pry the edge of the preform with a special tool to complete the demolding. After demolding, clean the residual adhesive residue and dust on the surface of the preform, and check the surface and edges. Only after there are no scratches, damages, delamination and other defects can the next process be carried out.

[0036] Existing technologies mostly use single-thickness honeycomb cores or honeycomb cores of different materials spliced ​​together. This invention uses a combination of double-honeycomb prefabricated panels of the same material but different thicknesses. The thickness difference achieves stiffness gradient and functional layering, while ensuring thermal expansion matching due to the same material, avoiding interlayer internal stress and debonding problems.

[0037] (III) Bonding of Double-Honeycomb Prefabricated Panels 1. Adhesion preparation: Place the qualified honeycomb preform 1 and the honeycomb preform 2 on a clean laying platform, remove dust and impurities from the surface of the reinforcing layers of both, and gently wipe the bonding surfaces (the reinforcing layers of the honeycomb preform 1 and the honeycomb preform 2) with anhydrous ethanol, and let them air dry naturally to ensure that the bonding surfaces are clean and free of oil stains, so as to avoid affecting the bonding effect.

[0038] 2. Adhesive film laying: The adhesive film is evenly laid on the surface of the reinforcing layer of the honeycomb prefabrication 1. The adhesive film completely covers the adhesive surface, with no omissions, no overlaps, no air bubbles, and a tight fit. If there are wrinkles in the adhesive film, use a special roller to gently roll and smooth it out to remove the air from the wrinkles.

[0039] 3. Alignment and bonding: The reinforcing layer of the second honeycomb preform 2 is precisely aligned with the adhesive film surface of the first honeycomb preform 1, ensuring that the edges of both are flush and without offset (offset ≤ ±0.3mm); after alignment, a special roller is used to slowly press from the center to the periphery to remove interlayer air, ensuring that the first honeycomb preform 1 and the second honeycomb preform 2 are tightly bonded to the adhesive film without gaps or air bubbles.

[0040] 4. Adhesion and Curing: Cover the bonded double preform assembly entirely with a high-temperature resistant vacuum bag film, and seal the edges with sealing strips. Connect a vacuum pump to evacuate (first evacuate at a low vacuum of -0.02~-0.03MPa for 5-10 minutes, then increase to -0.08~-0.10MPa and continue evacuating for 30-40 minutes); while maintaining the vacuum state, place the assembly into an oven and cure according to the gradient curing program: raise the temperature to 90℃ and hold for 1.5 hours, then raise the temperature to 110℃ and hold for 2.5 hours to ensure that the adhesive film is completely cured and that the double preforms are firmly bonded; monitor the temperature and vacuum level in real time during the curing process to ensure that there are no abnormalities.

[0041] 5. Cooling and cleaning: After curing, turn off the oven heating switch, keep the vacuum pump running for 30 minutes, then turn off the vacuum pump and let it cool naturally to room temperature; remove the vacuum bag film and sealing strip, clean the residual adhesive stains and dust on the surface of the components, and check the bonding surface. It is qualified if there is no interlayer peeling, no gaps, and no cracks.

[0042] Existing honeycomb panel bonding technologies mostly involve core-to-core or skin-to-skin bonding. This invention, however, adopts a reinforcing layer-to-reinforcing layer bonding method, which forms a high-rigidity sandwich layer between the reinforcing layers of the two prefabricated panels, significantly improving the overall bending and peel resistance.

[0043] (iv) Outer skin laying and overall curing This step employs a pre-applied skinning process, where a bottom layer of skin is pre-applied to the mold surface, then the bonded double prefabricated components are placed on and precisely aligned, and finally the top layer of skin is applied to form the basic structure of the product. The specific steps are as follows: 1. Mold pretreatment: Prepare a special mold that meets the product size requirements, clean the inner surface of the mold to remove dust, oil and residual glue stains, and ensure that the mold surface is flat, clean and free of scratches; wipe the inner surface of the mold with anhydrous ethanol, let it air dry naturally, and then evenly lay a layer of high temperature resistant release cloth. The release cloth should be tightly attached, without wrinkles or displacement, and completely cover the mold laying area to facilitate subsequent demolding and protect the surface quality of the skin.

[0044] 2. Pre-laying of the bottom layer skin: Lay the cut outer skin (bottom layer) flat on the surface of the mold release cloth as the bottom layer skin. The skin laying direction is 45° with the direction of the reinforcement layer. During the laying process, use a special roller to slowly roll from the center to the periphery to remove the air between the skin and the mold and the release cloth, ensuring that the bottom layer skin is tightly attached, without wrinkles, air bubbles, or deviation. The edge of the skin extends 2-3cm beyond the edge of the mold, and will be trimmed and adjusted later.

[0045] 3. Prefabricated component alignment and placement: Place the properly bonded double prefabricated components smoothly on the surface of the bottom skin, accurately aligning them with the mold positioning marks to ensure that the center of the component coincides with the center of the mold and the edges are parallel to the edges of the mold. The bottom surface of the component (the bottom surface of the core layer of the honeycomb prefabricated component 1) should be tightly fitted with the bottom skin without gaps or offset (offset ≤ ±0.3mm). Handle with care during placement to avoid damaging the bottom skin and the surface of the prefabricated components.

[0046] 4. Top layer skin installation: Lay another properly cut outer skin (top layer) flat on the top surface of the double prefabricated component (the top surface of the reinforcing layer of the honeycomb prefabricated component 2), with the installation direction consistent with the bottom layer skin; similarly, use a special roller to slowly roll from the center to the periphery to remove the air between the top layer skin and the prefabricated component, ensuring that the top layer skin is tightly bonded, without wrinkles, bubbles, or damage, and that the edges of the top layer skin are aligned with the edges of the bottom layer skin, both extending 2-3 cm beyond the edge of the mold.

[0047] 5. Auxiliary fixation: Cover the surface of the top layer skin with a layer of release film to prevent the vacuum bag film from sticking to the top layer skin during subsequent sealing; the release film is laid flat and without wrinkles, completely covering the surface of the top layer skin, with its edges aligned with the skin edges.

[0048] 6. Overall sealing and vacuuming: Cover the entire skin-preform assembly inside the mold with a high-temperature resistant vacuum bag film, and press and seal the edges with sealing strips to ensure that the vacuum bag film fits tightly with the mold and there are no air leaks; connect the vacuum pump to evacuate the vacuum. First, pre-evacuate at a low vacuum degree of -0.02~-0.03MPa for 5-10 minutes to remove residual air inside the vacuum bag film and between each layer, and then gradually increase to a high vacuum degree of -0.08~-0.10MPa and continue evacuating the vacuum for 40-50 minutes to ensure that the bottom skin, preform assembly and top skin fit tightly together without any gaps or air bubbles.

[0049] 7. Overall Curing: Maintain continuous vacuum pump operation, smoothly place the sealed mold into the oven, and perform final curing according to the preset gradient curing program to ensure a firm bond between the skin and the prefabricated components, while further enhancing the adhesion of each layer; Curing program: First, raise the temperature to 85℃ and hold for 1 hour; then raise the temperature to 105℃ at a rate of 5℃ / h and hold for 2 hours; then raise the temperature to 120℃ and hold for 3 hours; During the curing process, monitor the temperature inside the oven in real time (fluctuation error ≤ ±2℃) and the vacuum level to ensure no air leakage, no pressure loss, and complete curing of the adhesive film.

[0050] Existing technologies mostly employ one-time or simple two-time curing, while this invention addresses industry challenges such as air bubbles, voids, and internal stress concentration in thick-section honeycomb structures by using prefabricated panel curing, inter-panel bonding curing, and overall skin curing, combined with low-vacuum pre-venting, high-vacuum compaction, and natural slow cooling control methods.

[0051] (v) Finished product finishing and testing 1. Cooling and demolding: After the overall curing is completed, turn off the oven heating switch, keep the vacuum pump running for 30 minutes, then turn off the vacuum pump and leave the components in the oven to cool naturally to room temperature (25±5℃) to avoid rapid cooling that could generate thermal stress, causing the preform to crack or delaminate between layers.

[0052] 2. Surface finishing: Remove the vacuum bag film, isolation film and sealing strip, use special cutting tools to trim the edges of the prefabricated body, remove excess skin corners, so that the finished product dimensions meet the design requirements, and the edges are flat and burr-free; clean the surface of the finished product of any residual glue stains and dust, and ensure that the surface is clean, scratch-free and undamaged.

[0053] 3. Finished Product Inspection: A comprehensive inspection is conducted on the repaired honeycomb prefabrication, including dimensional accuracy (error ≤ ±0.5mm), interlayer bonding performance (no peeling, no voids), surface quality (no wrinkles, no damage, no scratches), density, and mechanical properties (tensile strength and bonding strength meet design requirements). Qualified finished products are sent to the next process, while unqualified products need to be analyzed for causes and reworked.

[0054] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for preparing a honeycomb preform, characterized in that, Includes the following steps: Step S1: Prepare two honeycomb prefabricated panels with different thicknesses, namely honeycomb prefabricated body one (1) and honeycomb prefabricated body two (2). Both honeycomb prefabricated body one (1) and honeycomb prefabricated body two (2) are three-layer composite structures, consisting of a core layer, an adhesive layer and a reinforcing layer from the inside out. Step S2: Use adhesive film to bond the first honeycomb preform (1) and the second honeycomb preform (2) to obtain a double preform assembly; Step S3: A skin is laid on the outer layer of the entire double prefabricated assembly. After overall curing, trimming and testing, a complete honeycomb prefabricated body is obtained.

2. The process for preparing a honeycomb preform according to claim 1, characterized in that, The core layer (101) of the honeycomb prefabricated body (1) is made of aerospace grade aramid paper honeycomb, the honeycomb cell shape is regular hexagonal, the cell side length is 3-5mm, the thickness is 10mm, and the density is 30-50kg / m³.

3. The process for preparing a honeycomb preform according to claim 1, characterized in that, The core layer 2 (201) of the honeycomb prefabricated body 2 (2) is made of aerospace grade aramid paper honeycomb, the honeycomb cell shape is regular hexagonal, the cell side length is 3-5mm, the thickness is 6.2mm, the density is 30-50kg / m³, and the material is the same as that of the core layer (101).

4. The process for preparing a honeycomb preform according to claim 1, characterized in that, The adhesive layer 1 (102) of the honeycomb preform 1 (1) and the adhesive layer 2 (202) of the honeycomb preform 2 (2) are both epoxy films with a carrier. The carrier is a polyester film with a film thickness of 0.1 mm, a solid content of ≥98%, and an adhesive strength of ≥15 MPa.

5. The process for preparing a honeycomb preform according to claim 1, characterized in that, The first reinforcing layer (103) of the honeycomb prefabricated body one (1) and the second reinforcing layer (203) of the honeycomb prefabricated body two (2) are both carbon fiber unidirectional strips laid in the 0° direction. The carbon fiber volume fraction is 60%-70%, the thickness is 0.1mm, and the laying surface has uniform density and no wrinkles or damage.

6. The process for preparing a honeycomb preform according to claim 1, characterized in that, In step S2, the adhesive film is a high-temperature resistant epoxy film with a thickness of 0.15-0.25mm, a solid content of ≥98%, an adhesive strength of ≥18MPa, a high temperature resistance of ≥120℃, and is compatible with the materials of adhesive layer 102 and adhesive layer 202.

7. The process for preparing a honeycomb preform according to claim 1, characterized in that, In step S3, the outer skin is made of plain weave bidirectional carbon fiber fabric with a carbon fiber volume fraction of 65%-75%, a thickness of 0.3-0.6mm, uniform surface density, and no damage, skipped stitches, or wrinkles.

8. The process for preparing a honeycomb preform according to claim 1, characterized in that, In the preparation process of the first (1) and the second (2) of the honeycomb preform, the method of layer-by-layer laying, vacuum sealing and gradient curing is adopted. The gradient curing procedure is as follows: first heat up to 80℃ and keep warm for 1 hour, then heat up to 100℃ at a rate of 5-10℃ / h and keep warm for 2 hours. The temperature fluctuation error during the curing process is ≤±2℃, and the vacuum degree is maintained at -0.08~-0.10MPa.

9. The process for preparing a honeycomb preform according to claim 1, characterized in that, In step S2, the curing procedure after the two preforms are bonded is as follows: heat up to 90℃ and hold for 1.5 hours, then heat up to 110℃ and hold for 2.5 hours. During the curing process, the vacuum degree is maintained at -0.08~-0.10MPa, and the temperature and vacuum degree are monitored in real time.

10. The process for preparing a honeycomb preform according to claim 1, characterized in that, In step S3, the overall curing procedure after the outer skin is laid is as follows: first, heat to 85℃ and hold for 1 hour, then heat to 105℃ at a rate of 5℃ / h and hold for 2 hours, and finally heat to 120℃ and hold for 3 hours. During the curing process, the temperature fluctuation error is ≤±2℃, and the vacuum degree is maintained at -0.08~-0.10MPa. When the finished product is inspected, the dimensional accuracy error is ≤±0.5mm, and there is no peeling or gaps between the layers.

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