Aramid fiber honeycomb core glass fiber reinforced interlayer cargo hold lining plate and manufacturing method

Abstract

The invention discloses an aramid honeycomb core glass fiber reinforced interlayer cargo hold lining plate and a manufacturing method, the cargo hold lining plate comprises an upper skin layer, a glue film layer, an aramid honeycomb core layer, a glue film layer and a lower skin layer which are laminated in sequence, and the upper skin layer and the lower skin layer are each composed of two layers of satin fabric phenolic aldehyde glass fiber prepreg and an outer polyvinyl fluoride film; the prepreg paving angles of the upper and lower skin layers are perpendicular to each other and are parallel or perpendicular to the directions of the honeycomb core strip grooves; all the layers are integrally formed through co-curing. By optimizing the laying angle design and adopting the polyvinyl fluoride film to replace a traditional TADLAR film, an adaptive adhesive film and prepreg, the problems that an existing lining plate is poor in mechanical balance, not firm in interface bonding and prone to failure of a surface layer are solved, and the composite lining plate has excellent mechanical property, flame-retardant safety and environment-resistant stability and is suitable for the field of aviation.

Description

Technical Field

[0001] This invention relates to an aramid honeycomb core glass fiber reinforced sandwich cargo hold liner. Background Technology

[0002] As a core non-metallic structural component in the aviation field, aircraft cargo hold liners must meet multiple technical requirements, including mechanical load-bearing capacity, flame retardancy, safety, and environmental stability. In existing technologies, the typical structure of mainstream cargo hold liners is as follows: a medium-density meta-aramid honeycomb core layer, with glass fiber reinforced phenolic prepreg applied to the upper and lower surfaces, and a TADLAR film laminated to the surface. The molding process often employs a "layer curing + secondary bonding" method.

[0003] The layup structure design failed to optimize fiber orientation for the service stress characteristics of the liner, and the reinforcing potential of the glass fiber was not fully utilized, resulting in poor uniformity of the mechanical properties of the liner under composite loads. Furthermore, the interfacial wetting effect between the adhesive system and the aramid honeycomb core and glass fiber reinforced phenolic skin layer was limited, and the curing parameters of the core layer and skin layer in the secondary adhesive bonding process were difficult to precisely coordinate, easily leading to residual micropores or stress concentrations at the interface, reducing interlaminar shear strength and delamination resistance.

[0004] Furthermore, TADLAR membranes are difficult to procure, which can easily affect the product's production steps and cycle time. Inferior TADLAR membranes, under the temperature cycling conditions of the aerospace environment, are prone to interfacial stress due to mismatched coefficients of thermal expansion, leading to membrane warping and cracking, affecting the wear resistance and corrosion resistance of the liner. Moreover, the compatibility between flame retardants and phenolic resin matrices in existing solutions is poor; while improving flame retardancy, it can easily lead to a decrease in resin toughness. Additionally, the control of smoke generation rate and toxic gas components is not precise enough, failing to achieve the optimal balance between flame retardancy, mechanical properties, and environmental safety. Therefore, a better technical solution is urgently needed through structural optimization, material adaptation, and process improvement. Summary of the Invention

[0005] This invention aims to solve the problems of poor mechanical balance, easy surface failure, weak interface bonding, and low process efficiency of existing cargo hold liners. It provides a structurally optimized, materially compatible, and process-controllable aramid honeycomb core glass fiber reinforced sandwich cargo hold liner and its manufacturing method. The specific technical solution is as follows:

[0006] An aramid honeycomb core glass fiber reinforced sandwich cargo hold liner, comprising an upper skin layer, an aramid honeycomb core layer and a lower skin layer stacked in sequence;

[0007] Both the upper and lower skin layers consist of several layers of phenolic fiberglass prepreg and a polyvinyl fluoride film on the outermost layer.

[0008] The phenolic fiberglass prepreg surface layer is a satin phenolic fiberglass prepreg, and the laying angle is parallel or perpendicular to the groove direction of the aramid honeycomb core layer. The laying angle of the phenolic fiberglass prepreg surface layer between the upper and lower skin layers is perpendicular to each other.

[0009] The aramid honeycomb core layer is a medium-density aramid paper honeycomb, with dimensions consistent with the upper and lower skins; both the upper and lower surfaces of the aramid honeycomb core layer are provided with an adhesive film layer;

[0010] The upper and lower skin layers, the adhesive film layer, and the aramid honeycomb core layer are co-cured and integrally formed.

[0011] Furthermore, the surface layer of the phenolic fiberglass fabric prepreg is a phenolic fiberglass fabric prepreg with a dry resin content of 38±3%, a single-layer cured thickness of 0.250±0.02mm, and a glass transition temperature E′>80℃.

[0012] The dry resin content of 38±3% balances the bonding ability and the glass fiber reinforcement effect, avoiding weak interlayer bonding due to insufficient resin and excessive masking of the mechanical effect of glass fiber; the single-layer curing thickness accuracy of 0.250±0.02mm ensures uniform skin layer thickness after multi-layer laying and prevents uneven stress; the glass transition temperature of E′>80℃ ensures that the prepreg maintains rigidity and does not soften or deform at the design operating temperature of the liner (up to 82℃).

[0013] Furthermore, the polyvinyl fluoride film has a minimum average tensile strength ≥62.1 MPa, an average longitudinal and transverse shrinkage percentage ≤5%, and a matte gloss of 12~22 at 60°. The minimum average tensile strength ≥62.1 MPa resists cargo friction and impact, reducing surface damage; the average longitudinal and transverse shrinkage percentage ≤5% matches the curing shrinkage of prepregs, preventing film warping and cracking; and the matte gloss of 12~22 prevents strong light reflection from interfering with visibility and facilitates daily cleaning, meeting the requirements for use in aviation cargo holds.

[0014] A method for manufacturing an aramid honeycomb core glass fiber reinforced sandwich cargo hold liner includes the following steps:

[0015] S1. Honeycomb core preparation: Select medium-density aramid paper honeycomb, cut it to the size that matches the upper and lower skins, clean the honeycomb core surface and eliminate static electricity;

[0016] S2. Honeycomb Drying: The adhesive surface of the cleaned honeycomb core is dehumidified and dried.

[0017] S3. Raw material cutting: Cut satin fabric phenolic fiberglass prepreg as the substrate for the skin layer;

[0018] S4. Preparation before layup: Build a layup platform and lay protective and release materials, and move it to a clean environment for later use;

[0019] S5. Laying and Pre-compacting: Lay out the release cloth, lower skin layer, film layer, honeycomb core, film layer, upper skin layer and release cloth in the preset order. During the process, comb the material and vacuum compact it once every n layers of material. The value of n is 1-6.

[0020] S6. Curing: The precast body that has been laid up and pre-compacted is transferred to the molding equipment and cured as a whole by heating;

[0021] S7. Post-processing: After curing, the finished cargo hold liner is obtained through demolding and edge treatment.

[0022] Furthermore, the cleaning method for the honeycomb core bonding surface in step S1 is vacuuming or blowing with dry, filtered compressed air, with static electricity elimination throughout the entire cleaning process. This operation ensures the cleanliness of the bonding surface: vacuuming or dry compressed air can effectively remove dust and debris, preventing contaminants from affecting the bonding; static electricity elimination throughout the process can prevent the adsorption of foreign impurities, laying the foundation for the subsequent tight bonding between the honeycomb core and the adhesive film layer.

[0023] Furthermore, the layup platform mentioned in step S4 is a wheeled workbench. A flat plate is placed on the platform, and release paper is laid on it before it is moved to the clean room. The flat plate is used to support the prepreg and honeycomb core, preventing displacement or twisting during layup and transfer. The wheeled workbench facilitates transfer, the flat plate prevents material displacement and twisting, the release paper prevents surface contamination, and the clean room environment reduces the introduction of impurities, ensuring layup quality.

[0024] Furthermore, the layup sequence in step S5 is as follows:

[0025] Release paper → KZ / 234TFNP release cloth → polyvinyl fluoride film → PL01 → PL02 → adhesive film layer → honeycomb core → adhesive film layer → PL03 → PL04 ​​→ polyvinyl fluoride film → KZ / 234TFNP release cloth;

[0026] During the layup process, a horn-shaped scraper is used to comb the fabric along the warp direction to prevent air entrapment and fiber wrinkling. The angle tolerance of the layup and honeycomb is controlled at ±8°. PL01, PL02, PL03, and PL04 ​​are all phenolic fiberglass prepreg layers. A fixed sequence ensures functional compatibility of each layer, warp combing prevents air bubbles and wrinkling, and the ±8° tolerance ensures accurate layup direction, fully leveraging the mechanical reinforcement effect of the prepreg.

[0027] Furthermore, the pre-compaction process meets the following requirements: vacuum compaction is performed after the first layer on the mold, the first layer of prepreg on the core material, and after every 1-6 layers, with a vacuum degree not lower than -0.06 MPa and a holding time not less than 5 minutes; vacuum compaction is performed after honeycomb positioning, with a vacuum degree not exceeding -0.034 MPa. These process parameters balance effectiveness and protection. High vacuum can expel interlayer air and prevent porosity, while the holding time ensures sufficient air removal. Low vacuum after honeycomb positioning prevents honeycomb slippage and improves interlayer bonding.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] In terms of mechanical properties, to address the problem of insufficient mechanical balance caused by existing non-directional lay-up, a design is adopted in which "the laying angle of phenolic glass fiber prepreg is parallel or perpendicular to the groove of aramid honeycomb core, and the angles of the upper and lower skin layers prepreg are perpendicular to each other". This design is adapted to the composite load during the service of the liner, giving full play to the reinforcing effect of glass fiber, so that the bending strength of the liner is ≥380MPa and the interlaminar shear strength is ≥30MPa, thus improving the uneven mechanical properties.

[0030] For surface protection, polyvinyl fluoride film is chosen instead of TADLAR film. This not only meets the wear resistance requirements but also adapts to the curing shrinkage characteristics of prepregs, effectively preventing film cracking under temperature cycling. Simultaneously, epoxy-modified adhesives are used in conjunction with a co-curing system and a staged pre-compaction process to reduce interfacial porosity caused by secondary bonding, improve interlayer adhesion, and eliminate the need for post-curing bonding of individual parts, simplifying the production process and improving efficiency. Attached Figure Description

[0031] Figure 1 This is a picture of the actual cargo hold lining.

[0032] Figure 2 This is a structural schematic diagram of the cargo hold liner;

[0033] Figure 3 This is a schematic diagram of the bonding between the prepreg and the honeycomb core;

[0034] Figure 4 This is a flowchart of the manufacturing process for this type of cargo hold liner.

[0035] Figure 5 These are the physical property parameters of ML7038 / 301F prepreg;

[0036] Figure 6 These are the mechanical property parameters of the ML7038 / 301F prepreg laminate;

[0037] Figure 7 This refers to the formaldehyde emission of the ML7038 / 301F prepreg laminate.

[0038] Figure 8 These are the flame retardant performance parameters of ML7038 / 301F prepreg laminate;

[0039] Figure 9 These are the performance parameters of MF9200 structural adhesive film;

[0040] Figure 10 These are the room temperature mechanical properties parameters of medium-density aramid paper honeycomb (SD-NH-1.83-64);

[0041] Figure 11 These are the physical property parameters of polyvinyl fluoride film;

[0042] Figure 12 This refers to the shrinkage performance parameter of polyvinyl fluoride film;

[0043] Figure 13 These are the specular gloss performance parameters of polyvinyl fluoride films;

[0044] In the figure: 1. Upper polyvinyl chloride film, 2. PL04, 3. PL03, 4. Aramid honeycomb core layer, 5. PL02, 6. PL01, 7. Lower polyvinyl chloride film, 8. Flat plate. Detailed Implementation

[0045] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0046] Example 1: As Figure 1-3 As shown, an aramid honeycomb core glass fiber reinforced sandwich cargo hold liner includes an upper skin layer, an aramid honeycomb core layer 4 and a lower skin layer stacked in sequence; both the upper and lower surfaces of the aramid honeycomb core layer 4 are provided with an adhesive film layer.

[0047] Both the upper and lower skin layers consist of several layers of phenolic fiberglass prepreg and a polyvinyl fluoride film on the outermost layer.

[0048] The phenolic fiberglass prepreg surface layer is a satin-weave phenolic fiberglass prepreg, wherein the upper skin is laid at an angle perpendicular to the groove direction of the aramid honeycomb core layer, forming the warp side. The lower skin is laid at an angle parallel to the groove direction of the aramid honeycomb core layer, forming the weft side. The upper and lower skin layers, the adhesive film layer, and the aramid honeycomb core layer are co-cured and integrally formed.

[0049] The manufacturing process includes the following steps:

[0050] The first step is to prepare the honeycomb core. One honeycomb core is needed, with dimensions matching the top and bottom skins. It is made of medium-density aramid paper honeycomb (SD-NH-1.83-64), and its shape matches the part's shape. For the honeycomb core with the prepared blank dimensions, the following cleaning procedures should be followed:

[0051] a) The adhesive surfaces of the honeycomb core, the formed or processed honeycomb parts, and the adhesive honeycomb assemblies shall be clean and free from visually visible contaminants, impurities, dust, or processing debris.

[0052] b) Use a vacuum cleaner or dry, filtered compressed air to remove any visible dust from the honeycomb core. (During processing and cleaning, static electricity should be eliminated to prevent foreign matter from adhering to the honeycomb core surface and affecting the subsequent bonding performance of the honeycomb core and skin).

[0053] The second step is honeycomb drying. The honeycomb core drying program is invoked to dehumidify and dry it.

[0054] The third step involves cutting the raw materials for the skin layer and the adhesive film (MF9200) layer. The skin layer uses satin-weave phenolic fiberglass prepreg ML7038 / 301F as the reinforcing material, with a cutting angle of 0° in the length direction (warp direction) × 90° in the width direction (weft direction), totaling four layers. The sheet numbers are PL01, PL02, PL03, and PL04. The adhesive film layer uses an epoxy-modified adhesive as a carrier for bonding the skin layer and the core layer, enhancing the overall peel strength, flexural strength, and shear strength of the cured cargo hold liner.

[0055] Step 4: Preparation before layup. Prepare a wheeled workbench with a flat plate on it. The flat plate is used to support the uncured cargo hold liner products and prevent the prepreg and honeycomb core from shifting or twisting during placement and transportation. Lay a layer of release paper on the flat plate (to protect the surface of the honeycomb panel products from contamination and for subsequent demolding). Move it into the clean room.

[0056] Step 5: Produce the cargo hold liner product according to the structural diagram of the cargo hold liner, the diagram of the bonding of the prepreg and the honeycomb core, and the precautions.

[0057] Precautions during the layup process: When laying up, first lay one layer of KZ / 234TFNP release cloth on the release paper for demolding and ventilation, and then lay up the other layers.

[0058] Special care should be taken to prevent any residual protective film or backing paper from getting into the parts; avoid air trapping and fiber wrinkling during the application process. To achieve this, a controlled plastic / horn scraper can be used to comb the fabric along the warp direction.

[0059] Cargo hold liner pre-compaction: When laying out the parts, the first layer on the mold, the first layer of prepreg on the core material, and every 1 to 6 layers are vacuum compacted. During vacuum compaction, a breathable felt is placed under the vacuum bag, and a non-porous isolation membrane is placed under the breathable felt. The vacuum level during compaction is not lower than -0.06 MPa, and the time is not less than 5 minutes.

[0060] For cellular sandwich components, once the cellular structure is positioned, the vacuum level during subsequent vacuum pressing should not exceed -0.034 MPa to prevent cellular slippage.

[0061] Finally, lay one layer of release fabric to cover the release paper; Prepreg splicing requirements: overlap: 12mm-19mm; Adhesive film splicing requirements: maximum overlap 6mm, maximum gap 1.5mm, adhesive film extends to the edge of the core material or exceeds the edge of the core material by a maximum of 13mm; If the surface layer needs to be spliced, the overlap seams of the two lower layers of prepreg and the two upper layers of prepreg must be staggered by at least 100mm to ensure that the mechanical strength of the entire cargo hold liner will not be reduced after molding.

[0062] Step 6: Cargo hold liner curing. Transfer the laid cargo hold liner prefabricated body to the hot press workbench and use a curing regime suitable for the satin fabric phenolic fiberglass prepreg used in the skin layer to cure the cargo hold liner honeycomb panel.

[0063] Step 7: After the cargo hold liner has cured, demold it, cut off the flash and remove the burrs to obtain a complete cargo hold liner product.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An aramid honeycomb core glass fiber reinforced sandwich cargo hold liner, characterized in that, It includes an upper skin layer, an aramid honeycomb core layer, and a lower skin layer stacked in sequence; Both the upper and lower skin layers consist of several layers of phenolic fiberglass prepreg and an outermost polyvinyl fluoride film. The phenolic fiberglass prepreg surface layer is a satin phenolic fiberglass prepreg, and the laying angle is parallel or perpendicular to the groove direction of the aramid honeycomb core layer. The laying angle of the phenolic fiberglass prepreg surface layer between the upper and lower skin layers is perpendicular to each other. The aramid honeycomb core layer is a medium-density aramid paper honeycomb, with dimensions consistent with the upper and lower skins; both the upper and lower surfaces of the aramid honeycomb core layer are provided with an adhesive film layer; The upper and lower skin layers, the adhesive film layer, and the aramid honeycomb core layer are co-cured and integrally formed.

2. The aramid honeycomb core glass fiber reinforced sandwich cargo hold liner according to claim 1, characterized in that, The surface layer of the phenolic fiberglass fabric prepreg is a phenolic fiberglass fabric prepreg with a dry resin content of 38±3%, a single-layer cured thickness of 0.250±0.02mm, and a glass transition temperature E′>80℃.

3. The aramid honeycomb core glass fiber reinforced sandwich cargo hold liner according to claim 1, characterized in that, The polyvinyl fluoride film has a minimum average tensile strength ≥62.1MPa, an average longitudinal and transverse shrinkage percentage ≤5%, and a matte gloss of 12~22 at 60°.

4. A method for manufacturing an aramid honeycomb core glass fiber reinforced sandwich cargo hold liner, characterized in that, Includes the following steps: S1. Honeycomb core preparation: Select medium-density aramid paper honeycomb, cut it to the size that matches the upper and lower skins, clean the honeycomb core surface and eliminate static electricity; S2. Honeycomb Drying: The adhesive surface of the cleaned honeycomb core is dehumidified and dried. S3. Raw material cutting: Cut satin fabric phenolic fiberglass prepreg as the substrate for the skin layer; S4. Preparation before layup: Build a layup platform and lay protective and release materials, and move it to a clean environment for later use; S5. Laying and Pre-compacting: Lay out the release cloth, lower skin layer, film layer, honeycomb core, film layer, upper skin layer and release cloth in the preset order. During the process, comb the material and vacuum compact it once every n layers of material. The value of n is 1-6. S6. Curing: The precast body with completed layup and precompaction is transferred to the molding equipment and cured as a whole by heating; S7. Post-processing: After curing, the finished cargo hold liner is obtained by demolding and edge treatment.

5. The method for manufacturing an aramid honeycomb core glass fiber reinforced sandwich cargo hold liner according to claim 4, characterized in that, The cleaning method for the honeycomb core adhesive surface in step S1 is vacuuming or blowing with dry and filtered compressed air, and the static electricity elimination process is carried out throughout the cleaning process.

6. The method for manufacturing an aramid honeycomb core glass fiber reinforced sandwich cargo hold liner according to claim 4, characterized in that, The layup platform mentioned in step S4 is a wheeled workbench. A flat plate is placed on the platform and release paper is laid on it before it is moved to the clean room. The flat plate is used to support the prepreg and honeycomb core to prevent displacement or twisting during layup and transportation.

7. The method for manufacturing an aramid honeycomb core glass fiber reinforced sandwich cargo hold liner according to claim 4, characterized in that, The layup sequence in step S5 is as follows: Release paper → KZ / 234TFNP release cloth → polyvinyl fluoride film → PL01 → PL02 → adhesive film layer → honeycomb core → adhesive film layer → PL03 → PL04 ​​→ polyvinyl fluoride film → KZ / 234TFNP release cloth; During the layup process, a horn scraper is used to comb along the warp of the fabric to prevent air from getting in and fibers from wrinkling. The angle tolerance of the layup and honeycomb is controlled at ±8°. PL01, PL02, PL03 and PL04 ​​are all phenolic fiberglass fabric prepreg layers.

8. The method for manufacturing an aramid honeycomb core glass fiber reinforced sandwich cargo hold liner according to claim 7, characterized in that, The pre-compaction process must meet the following requirements: vacuum compaction must be performed after the first layer of the mold, the first layer of prepreg on the core material, and after every 1 to 6 layers, with a vacuum degree of not less than -0.06 MPa and a holding time of not less than 5 minutes; vacuum compaction must be performed after the honeycomb is positioned, with a vacuum degree of not more than -0.034 MPa.

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