A lightweight carbon fiber composite kayak body material and a preparation method thereof

Abstract

The application relates to the technical field of carbon fiber composite materials, in particular to a lightweight carbon fiber composite kayak body material for kayaks and a preparation method thereof. A terpolymer is obtained by copolymerization of dicyclopentadiene, isobornyl acrylate and styrene, and then the terpolymer is compounded with a diphenyl epoxy resin and 4,4'-diamino diphenyl sulfone to form a modified resin matrix. Then, the modified resin matrix is made into a resin film, and the resin film and a carbon fiber reinforcement are made into a prepreg through a hot melting method. Finally, the composite kayak body material is prepared through layering, adding a sandwich layer and adopting a hot press tank curing forming. The kayak body material prepared by the application has the characteristics of heat-resistant stability, reduced water absorption, improved fracture toughness and the like, can effectively transfer and disperse loads, reduce stress concentration, improve bending stiffness and weight efficiency, and inhibit crack propagation.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber composite materials technology, and in particular to a lightweight carbon fiber composite hull material for kayaks and its preparation method. Background Technology

[0002] Carbon fiber composite material is a high-performance material with carbon fiber as the reinforcement and resin as the matrix. As a water sport that combines competitive and recreational aspects, the performance of the hull material directly determines the sport's performance and user experience in kayaking. With the popularization of the sport and the improvement of competitive levels, the market demand for lightweight, high-strength, and corrosion-resistant hulls is becoming increasingly urgent. Early kayak hulls mostly used natural materials such as hollowed-out solid wood and spliced ​​planks covered with leather, which could not meet the performance requirements of modern kayaks. While the application of synthetic materials such as plastics and fiberglass has improved the situation, limitations such as excessive weight and insufficient strength still exist. The low-density characteristics of carbon fiber composite material can effectively reduce the weight of the hull, improve paddling speed and maneuverability, while its high strength and fatigue resistance ensure structural stability in complex water conditions, and its corrosion resistance is more suitable for long-term use on the water.

[0003] The invention patent with publication number CN114197201A discloses a magnetic graphene oxide modified carbon fiber, its preparation method and uses. The modified carbon fiber is obtained by sizing the carbon fiber with a magnetic graphene oxide solution containing a film-forming agent. It can significantly improve the interfacial properties of carbon fiber reinforced composite materials and can be applied to the preparation of parts in aerospace, ship and submarine, energy equipment and other fields.

[0004] In existing technologies, due to the inherent rigidity of carbon fiber, the overall stiffness is too high when combined with a resin matrix, lacking sufficient buffering deformation capacity. This results in no obvious deformation warning when the hull encounters a collision, making it prone to sudden fracture. Furthermore, its puncture resistance and lateral impact resistance are poor. When navigating in shallow waters, if it accidentally runs aground, rubs against underwater rocks, or is struck by sharp debris, it is highly susceptible to hull damage and delamination between carbon fiber layers, severely affecting the kayak's lifespan and safety. In addition, the impact of water currents under wave action and the repeated bending and compression caused by the hull's undulations generate minute shear stresses at the interface between the carbon fiber bundles and the resin matrix, as well as between different fiber layers. Under continuous complex wave loads, the carbon fiber composite hull is highly susceptible to progressive micro-fatigue damage, creating long-term safety hazards. Summary of the Invention

[0005] To address the problems mentioned in the background section, this invention provides a lightweight carbon fiber composite hull material for kayaks and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a lightweight carbon fiber composite hull material for kayaks includes the following steps: S1. Dicyclopentadiene (CAS No.: 77-73-6), isobornyl acrylate (CAS No.: 5888-33-5), and styrene (CAS No.: 100-42-5) are mixed and copolymerized under the action of an initiator to obtain a terpolymer. The terpolymer is then mixed with biphenyl epoxy resin and 4,4'-diaminodiphenyl sulfone (CAS No.: 80-08-0). The mixing process is carried out at room temperature (25±5℃) and stirring speed (150-250 r / min) for 20-40 min to obtain a modified resin matrix. S2. The modified resin matrix is ​​made into a resin film, and then combined with the carbon fiber reinforcement by hot melt method to obtain carbon fiber prepreg; S3. The carbon fiber prepreg is laid up according to the ply structure, and a core layer is added. After encapsulation, it is cured by autoclave process to obtain composite hull material.

[0007] Furthermore, the copolymerization reaction in step S1 is specifically as follows: Dicyclopentadiene, isobornyl acrylate, and styrene were added to a reactor, followed by N-methylpyrrolidone. The mixture was stirred thoroughly and heated in a constant-temperature water bath under nitrogen protection. The initiator solution was added dropwise while stirring. After the addition was complete, dodecanethiol was added, and the temperature was maintained to initiate the polymerization reaction for 10-24 hours. After the reaction was completed, the mixture was cooled to room temperature, and hydroquinone ethanol solution was added to the reaction system to terminate the reaction. The product was separated and purified to obtain a white solid powder terpolymer.

[0008] Further, in step S1, the mass ratio of the terpolymer, biphenyl epoxy resin and 4,4'-diaminodiphenyl sulfone is (20-40):(50-80):(5-20), preferably (25-35):(60-70):(10-15). During mixing, high-speed stirring is used, with a stirring rate of 300-400 r / min, a stirring time of 30-60 min, and a stirring temperature of 40-50℃.

[0009] Further, in step S2, the thickness of the resin film is 0.05-0.20 mm, and the carbon fiber reinforcement is a unidirectional fabric, plain weave fabric, or twill weave fabric woven from high-strength carbon fibers of T700 grade and above; during hot-melt lamination, the temperature of the lamination roller is controlled at 80-90℃, the pressure is 0.3-0.8 MPa, and the lamination linear speed is 0.5-2.0 m / min, resulting in a carbon fiber prepreg with a resin mass content of 35-45%; the resin film is prepared by casting, with a casting temperature of 100-120℃ and a casting rate of 0.3-0.6 m / min; the areal density of the carbon fiber reinforcement is 150-300 g / m³. 2The fiber diameter is 5-8μm; before hot melt lamination, the carbon fiber reinforcement needs to be preheated at 110-130℃ for 10-20min to remove surface moisture, and then cooled to 60-70℃ before lamination; the resin mass content is preferably 38-42%.

[0010] Furthermore, in step S3, the layup structure is symmetrically distributed, with carbon fiber prepreg laid symmetrically above and below the core layer; the total number of layups is 8-20 layers, of which 4-10 layers of carbon fiber prepreg are laid above the core layer and 4-10 layers of carbon fiber prepreg are laid below the core layer, with the number of layers in the upper and lower layers being the same and the structure being symmetrical, and the fiber orientation angle between adjacent layers of carbon fiber prepreg being 30°-90°; the layup is carried out manually or mechanically, and a pre-pressure of 0.1-0.2MPa is applied during layup to ensure that the prepreg is tightly bonded without bubbles or wrinkles; the fiber orientation angle between adjacent layers is preferably 45°-90°, and the total number of layups is preferably 12-16 layers, with 6-8 layers laid on each side; the laying environment temperature is controlled at 20-25℃ and the relative humidity is 40-60%.

[0011] Furthermore, in step S3, the core layer is made of a lightweight closed-cell foam material, selected from polyvinyl chloride foam, polyimide foam, or polyurethane foam. The thickness of the core layer is 5-20 mm, and the areal density is 30-80 g / m³. 2 The core layer has a porosity of 80-90%, a compressive strength ≥0.3MPa, and a tensile strength ≥0.5MPa. The surface of the core layer needs to be polished to a roughness Ra of 1.6-3.2μm. After polishing, it should be wiped clean with anhydrous ethanol to remove surface impurities. The core layer thickness is preferably 8-15mm, and the areal density is preferably 40-60g / m³. 2 .

[0012] Furthermore, in the ply structure, the outermost layer (outer surface layer of the hull) and the innermost layer (inner surface layer of the hull) are covered with plain weave or twill fabric, while the intermediate layer between the outer layer and the core layer is covered with unidirectional fabric. The total ply thickness of the surface layers (outer and inner surface layers) accounts for 20%-30% of the total ply thickness, ensuring that the inner and outer surfaces of the hull are smooth and have good impact and wear resistance. The intermediate layer ensures the overall rigidity and tensile strength of the hull, adapting to the stress requirements during kayaking. During the plying process, a small amount of modified resin matrix is ​​applied as an adhesive between the carbon fiber prepregs and between the carbon fiber prepregs and the core layer. The amount of adhesive is 1-3% of the prepreg mass, ensuring that the layers are tightly bonded without gaps.

[0013] Further, the autoclave curing process parameters in step S3 are as follows: curing temperature 120-160℃, heating rate 2-5℃ / min, curing pressure 0.5-1.2MPa, and constant temperature curing time 2-4h; vacuum treatment is required before autoclave curing, with a vacuum degree ≤-0.095MPa and a vacuuming time of 30-60min; after constant temperature curing, the temperature is cooled to room temperature at a cooling rate of 1-3℃ / min, and the curing pressure is maintained until the temperature drops below 80℃ before depressurization; the preferred curing temperature is 130-150℃, the preferred heating rate is 3-4℃ / min, the preferred curing pressure is 0.8-1.0MPa, and the preferred constant temperature curing time is 2.5-3.5h.

[0014] Further, the mass ratio of dicyclopentadiene, isobornyl acrylate, and styrene is (18.8-21.2):(44.3-55.7):(36.9-43.1), the initiator is selected from benzoyl peroxide and azobisisobutyronitrile, and the amount of initiator added is 0.3-0.8% of the total mass of dicyclopentadiene, isobornyl acrylate, and styrene; the amount of dodecyl mercaptan added is 0.01-0.03% of the total mass of dicyclopentadiene, isobornyl acrylate, and styrene; the preferred mass ratio of dicyclopentadiene, isobornyl acrylate, and styrene is 18.8:44.3:36.9; the preferred initiator is azobisisobutyronitrile, and the preferred amount added is 0.5-0.6%; the preferred amount of dodecyl mercaptan added is 0.02-0.025%.

[0015] Furthermore, the constant temperature water bath is heated to 75-85℃, and the stirring rate is controlled at 200-350 r / min; the initiator solution is prepared using N-methylpyrrolidone as the solvent, with a mass ratio of initiator to N-methylpyrrolidone of (1-3):10, a dropping rate of 1-3 drops / second, and a dropping time controlled at 15-30 min; the preferred temperature of the constant temperature water bath is 80-82℃, and the preferred stirring rate is 250-300 r / min; the initiator and N-methylpyrrolidone... The preferred mass ratio of N-methylpyrrolidone is 2:10; the amount of N-methylpyrrolidone added is 30-50% of the total mass of dicyclopentadiene, isobornyl acrylate, and styrene; the mass concentration of hydroquinone ethanol solution is 5-10%, and the amount added is 0.5-1.5% of the total mass of the reaction system; the separation and purification are carried out by vacuum filtration, washing, and vacuum drying steps, with a vacuum drying temperature of 60-80℃ and a drying time of 8-12h, and the particle size of the dried product is 50-100μm.

[0016] According to another aspect of the present invention, a lightweight carbon fiber composite hull material for kayaks prepared by the above-described method is provided, comprising an inner skin layer, a core layer, and an outer skin layer arranged sequentially from the inside to the outside, wherein both the inner skin layer and the outer skin layer are formed by curing carbon fiber prepreg, and the thickness of both the inner skin layer and the outer skin layer is 1.5-4.0 mm, preferably 2.0-3.0 mm; the surface roughness Ra of the inner skin layer is ≤0.8 μm, and the surface of the outer skin layer is polished.

[0017] The beneficial effects of this invention are: 1. Through the copolymerization of dicyclopentadiene, isobornyl acrylate, and styrene, both rigid structural units and flexible hydrophobic side chains are introduced into the copolymer molecular chain. The incorporation of rigid structural units helps maintain and enhance the overall modulus and thermal stability of the resin matrix, providing a foundation for the material's load-bearing capacity. The introduction of flexible hydrophobic side chains creates more free volume within the polymer network, which is beneficial for absorbing and dissipating external impact energy, thereby improving the fracture toughness of the matrix and alleviating the brittleness problem of traditional epoxy resins. Furthermore, the presence of hydrophobic groups reduces the overall polarity of the resin, helping to slow down the penetration and diffusion rate of water molecules. The modified resin matrix obtained in this way forms a polymer network with rigidity, toughness, and low water absorption after curing.

[0018] 2. A stable "sandwich" composite structure is constructed by employing a symmetrical layup combined with a multi-angle fiber orientation, along with the introduction of a lightweight closed-cell foam core layer. This structure effectively transfers and disperses in-plane loads through fiber layers in different directions, helping to reduce stress concentration. The presence of the core layer not only significantly improves the overall structural bending stiffness and weight efficiency but also absorbs some energy through the compression deformation of the core material during localized impacts, providing support for the skin layer. The toughened resin matrix absorbs impact energy through microscopic plastic deformation, and the multi-angle layup and sandwich structure help convert localized point impact loads into larger-area in-plane stresses, thereby inhibiting rapid crack propagation and penetrating damage. This reduces the risk of catastrophic brittle fracture of the hull upon collision or scraping.

[0019] 3. The fatigue resistance and long-term reliability of the hull material produced by this invention will be enhanced. The strengthened resin-fiber interface bonding and balanced layup structure help suppress the initiation of microcracks at the interface and between layers under alternating loads. The tough matrix has a blunting effect on the microcrack tips, while the symmetrical structural design helps reduce internal residual stress, which is beneficial to slowing down the accumulation rate of fatigue damage under dynamic loads such as repeated wave impacts, and extending the service life of the product.

[0020] 4. The hull material produced by this invention achieves lightweighting while maintaining high stiffness, strength, and good toughness. Foam sandwich structures are an effective way to achieve high specific stiffness. Furthermore, copolymer modification improves the toughness of the matrix while maintaining relatively controllable effects on its stiffness and strength, allowing the final composite material to have its mechanical properties adjusted within a wider range. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] A method for preparing a lightweight carbon fiber composite hull material for kayaks includes the following steps: S1. Weigh 18.8g of dicyclopentadiene, 44.3g of isobornyl acrylate, and 36.9g of styrene, add them to the reactor, add 30g of N-methylpyrrolidone, and mix thoroughly. Under nitrogen protection, heat the mixture to 75℃ in a constant temperature water bath, control the stirring rate at 200r / min, and add the initiator solution dropwise at a rate of 1 drop / second while stirring. The initiator used is 0.3g of benzoyl peroxide, and the amount added is 0.3% of the total mass of the three monomers. Use 3g of [unclear text - possibly a specific ingredient or ingredient] to [unclear text - possibly a specific ingredient or ingredient]. N-methylpyrrolidone was dissolved and added dropwise over a time of 15 min. After the addition was complete, 0.01 g of dodecanethiol was added, and the polymerization reaction was carried out at 75 °C for 10 h. After the reaction was completed, the mixture was cooled to room temperature, and 0.775 g of a 5% hydroquinone ethanol solution (0.5% of the total mass of the reaction system 133.31 g) was added to the reaction system to terminate the reaction. The product was filtered, washed, and then vacuum dried at 60 °C for 8 h to obtain a white solid powder terpolymer. 20 g of the terpolymer, 80 g of biphenyl epoxy resin, and 5 g of 4,4'-diaminodiphenyl sulfone were weighed and stirred at 20 °C and 150 r / min for 20 min until homogeneous to obtain the modified resin matrix. S2. A resin film with a thickness of 0.05 mm is formed from the modified resin matrix using a casting method at a casting temperature of 100℃ and a casting rate of 0.3 m / min. A unidirectional fabric woven from T700 grade high-strength carbon fiber with an areal density of 150 g / m² is selected. 2 The fiber diameter is 5μm. As a carbon fiber reinforcement, it is preheated at 110℃ for 10min and cooled to 60℃. Then, it is laminated with a resin film by hot melt method. The temperature of the lamination roller is controlled at 80℃, the pressure is 0.3MPa, and the lamination line speed is 0.5m / min to obtain carbon fiber prepreg. S3. Under an environment of 20℃ and 40% relative humidity, lay up the carbon fiber prepreg in a symmetrical layered structure, using a thickness of 5mm and a surface density of 30g / m³. 2 A polyvinyl chloride closed-cell foam with a porosity of 80% was used as the core layer. The total number of layers was 8. With the core layer as the center, 4 layers of carbon fiber prepreg were laid on the top and bottom. The fiber direction angle between two adjacent carbon fiber prepreg layers was 30°. A pre-pressure of 0.1MPa was applied during the laying process. After the laying was completed, the material was sealed and placed in an autoclave. The pressure was first evacuated to -0.095MPa and maintained for 30 minutes. Then, the temperature was increased to 120°C at a heating rate of 2°C / min, and a curing pressure of 0.5MPa was applied. The material was then cured at a constant temperature for 2 hours. After curing, the material was cooled to below 80°C at a cooling rate of 1°C / min. After depressurization, the material was cooled to room temperature to obtain the composite hull material.

[0024] Example 2

[0025] A method for preparing a lightweight carbon fiber composite hull material for kayaks includes the following steps: S1. Weigh 20.0g of dicyclopentadiene, 50.0g of isobornyl acrylate, and 40.0g of styrene, add them to the reactor, add 44g of N-methylpyrrolidone, and stir thoroughly. Under nitrogen protection, heat the mixture to 80℃ in a constant temperature water bath, control the stirring rate at 280r / min, and add the initiator solution dropwise at a rate of 2 drops / second while stirring. The initiator used is 0.55g of azobisisobutyronitrile (AIBN), and the amount added is 0.5% of the total mass of the three monomers, using 2.75g. N-methylpyrrolidone was dissolved and added dropwise over a time of 22 min. After the addition was complete, 0.022 g of dodecanethiol was added, and the polymerization reaction was carried out at 80 °C for 18 h. After the reaction was completed, the mixture was cooled to room temperature, and 1.623 g of 8% hydroquinone ethanol solution (1.0% of the total mass of the reaction system 162.322 g) was added to the reaction system to terminate the reaction. The product was filtered, washed, and then vacuum dried at 70 °C for 10 h to obtain a white solid powder terpolymer. 30 g of the terpolymer, 65 g of biphenyl epoxy resin, and 12 g of 4,4'-diaminodiphenyl sulfone were weighed and stirred at 25 °C and 350 r / min for 45 min until homogeneous to obtain the modified resin matrix. S2. A resin film with a thickness of 0.12 mm was formed from the modified resin matrix using a casting method at a casting temperature of 110℃ and a casting rate of 0.45 m / min. Plain weave fabric woven from T800 grade high-strength carbon fiber with a surface density of 220 g / m² was selected. 2 The fiber diameter is 6.5μm. As a carbon fiber reinforcement, it is preheated at 120℃ for 15min, cooled to 65℃, and then laminated with a resin film by hot melt method. The temperature of the lamination roller is controlled at 85℃, the pressure is 0.5MPa, and the lamination line speed is 1.2m / min to obtain carbon fiber prepreg. S3. Under an environment of 23℃ and 50% relative humidity, lay up the carbon fiber prepreg in a symmetrical layered structure, using a thickness of 12mm and a surface density of 50g / m³. 2 A polyimide closed-cell foam with a porosity of 85% was used as the core layer. The total number of layers was 14. With the core layer as the center, 7 layers of carbon fiber prepreg were laid on the top and bottom. The fiber direction angle between two adjacent carbon fiber prepreg layers was 60°. A pre-pressure of 0.15MPa was applied during the laying process. After the laying was completed, the material was sealed and placed in an autoclave. The pressure was first evacuated to -0.098MPa and maintained for 45 minutes. Then, the temperature was increased to 140°C at a heating rate of 3.5°C / min, and a curing pressure of 0.9MPa was applied. The material was cured at a constant temperature for 3 hours. After curing, the temperature was cooled to below 80°C at a cooling rate of 2°C / min. After depressurization, the material was cooled to room temperature to obtain the composite hull material.

[0026] Example 3

[0027] A method for preparing a lightweight carbon fiber composite hull material for kayaks includes the following steps: S1. Weigh 21.2g of dicyclopentadiene, 55.7g of isobornyl acrylate, and 43.1g of styrene, add them to the reactor, add 60g of N-methylpyrrolidone, and stir thoroughly. Under nitrogen protection, heat the mixture to 85℃ in a constant temperature water bath, control the stirring rate at 350r / min, and add the initiator solution dropwise at a rate of 3 drops / second while stirring. The initiator used is 0.96g of azobisisobutyronitrile (AIBN), which is 0.8% of the total mass of the three monomers, using 3.2g of [agent name missing]. N-methylpyrrolidone was dissolved and added dropwise over a time of 30 min. After the addition was complete, 0.036 g of dodecanethiol was added, and the polymerization reaction was carried out at 85 °C for 24 h. After the reaction was completed, the mixture was cooled to room temperature, and 2.76 g of a 10% hydroquinone ethanol solution (1.5% of the total mass of the reaction system 184.196 g) was added to the reaction system to terminate the reaction. The product was filtered, washed, and then vacuum dried at 80 °C for 12 h to obtain a white solid powder terpolymer. 40 g of the terpolymer, 50 g of biphenyl epoxy resin, and 20 g of 4,4'-diaminodiphenyl sulfone were weighed and stirred at 30 °C and 250 r / min for 40 min until homogeneous to obtain the modified resin matrix. S2. A resin film with a thickness of 0.20 mm is formed from the modified resin matrix using a casting method at a casting temperature of 120℃ and a casting rate of 0.6 m / min; twill fabric woven from T1100 grade high-strength carbon fiber with an areal density of 300 g / m² is selected. 2The fiber diameter is 8μm. As a carbon fiber reinforcement, it is preheated at 130℃ for 20min, cooled to 70℃, and then laminated with a resin film by hot melt method. The temperature of the lamination roller is controlled at 90℃, the pressure is 0.8MPa, and the lamination line speed is 2.0m / min to obtain carbon fiber prepreg. S3. Under an environment of 25℃ and 60% relative humidity, lay up the carbon fiber prepreg in a symmetrical layered structure, using a thickness of 20mm and a surface density of 80g / m³. 2 A polyurethane closed-cell foam with a porosity of 90% was used as the core layer. The total number of layers was 20. With the core layer as the center, 10 layers of carbon fiber prepreg were laid on the top and bottom. The fiber direction angle between two adjacent carbon fiber prepreg layers was 90°. A pre-pressure of 0.2MPa was applied during the laying process. After the laying was completed, the material was sealed and placed in an autoclave. The pressure was first evacuated to -0.100MPa and maintained for 60 minutes. Then, the temperature was increased to 160°C at a heating rate of 5°C / min, and a curing pressure of 1.2MPa was applied. The material was then cured at a constant temperature for 4 hours. After curing, the material was cooled to below 80°C at a cooling rate of 3°C / min. After depressurization, the material was cooled to room temperature to obtain the composite hull material.

[0028] Example 4

[0029] A method for preparing a lightweight carbon fiber composite hull material for kayaks includes the following steps: S1. Weigh 19.5g of dicyclopentadiene, 48.0g of isobornyl acrylate, and 38.5g of styrene, add them to the reactor, add 36.04g of N-methylpyrrolidone, and mix thoroughly. Under nitrogen protection, heat the mixture to 78℃ in a constant temperature water bath, control the stirring rate at 250r / min, and add the initiator solution dropwise at a rate of 2 drops / second while stirring. The initiator used is 0.424g of benzoyl peroxide, and the amount added is 0.4% of the total mass of the three monomers, using 4.24g. N-methylpyrrolidone was dissolved and added dropwise over a time of 20 min. After the addition was complete, 0.0159 g of dodecanethiol was added, and the polymerization reaction was carried out at 78 °C for 14 h. After the reaction was completed, the mixture was cooled to room temperature, and 1.09 g of a 6% hydroquinone ethanol solution (0.75% of the total mass of the reaction system, 146.6799 g) was added to the reaction system to terminate the reaction. The product was filtered, washed, and then vacuum dried at 65 °C for 9 h to obtain a white solid powder terpolymer. 28 g of the terpolymer, 72 g of biphenyl epoxy resin, and 8 g of 4,4'-diaminodiphenyl sulfone were weighed and stirred at 22 °C and 200 r / min for 30 min until homogeneous to obtain the modified resin matrix. S2. A resin film with a thickness of 0.09 mm was formed from the modified resin matrix using a casting method at a casting temperature of 105℃ and a casting rate of 0.4 m / min. Twill fabric woven from T700 grade high-strength carbon fiber with an areal density of 180 g / m² was selected.2 The fiber diameter is 5.5 μm. As a carbon fiber reinforcement, it is preheated at 115℃ for 12 min, cooled to 62℃, and then laminated with a resin film by hot melt method. The temperature of the laminating roller is controlled at 82℃, the pressure is 0.5 MPa, and the laminating linear speed is 0.9 m / min to obtain carbon fiber prepreg. S3. Under an environment of 21℃ and 45% relative humidity, carbon fiber prepreg is laid in a symmetrical layered structure, using a thickness of 9mm and a surface density of 45g / m³. 2 A polyvinyl chloride closed-cell foam with a porosity of 82% was used as the core layer. The total number of layers was 10. With the core layer as the center, 5 layers of carbon fiber prepreg were laid on the top and bottom. The fiber direction angle between two adjacent carbon fiber prepreg layers was 45°. A pre-pressure of 0.12MPa was applied during the laying process. After the laying was completed, the material was sealed and placed in an autoclave. The pressure was first evacuated to -0.096MPa and maintained for 38 minutes. Then, the temperature was increased to 130°C at a heating rate of 3°C / min, and a curing pressure of 0.7MPa was applied. The material was then cured at a constant temperature for 2.5 hours. After curing, the material was cooled to below 80°C at a cooling rate of 1.5°C / min. After depressurization, the material was cooled to room temperature to obtain the composite hull material.

[0030] Comparative Example 1 The difference between this comparative example and Example 1 is that dicyclopentadiene is not added in step S1, while the remaining steps and parameters are completely consistent with those of Example 1.

[0031] Comparative Example 2 The difference between this comparative example and Example 2 is that isobornyl acrylate is not added in step S1, while the remaining steps and parameters are completely consistent with Example 2.

[0032] Comparative Example 3 The difference between this comparative example and Example 3 is that styrene is not added in step S1, while the remaining steps and parameters are completely consistent with Example 3.

[0033] Comparative Example 4 The difference between this comparative example and Example 4 is that biphenyl epoxy resin is not added in step S1, while the remaining steps and parameters are completely consistent with Example 4.

[0034] Comparative Example 5 The difference between this comparative example and Example 1 is that 4,4'-diaminodiphenyl sulfone is not added in step S1, while the remaining steps and parameters are completely consistent with those of Example 1.

[0035] Comparative Example 6 The difference between this comparative example and Example 2 is that no carbon fiber reinforcement is added in step S1, while the remaining steps and parameters are completely consistent with Example 2.

[0036] Composite material plates were prepared according to the preparation methods of Examples 1-4 and Comparative Examples 1-6. At least 5 standard plates (not less than 300mm × 300mm) were prepared for each group, and after curing, they were uniformly conditioned for 24 hours in an environment with a temperature of 23±2℃ and a relative humidity of 50±5%. Samples of corresponding sizes were cut from each plate according to the test standards, and at least 5 parallel samples were taken for each test item in each group.

[0037] (I) Mechanical property testing: Referring to GB / T 1447-2005 "Test Method for Tensile Properties of Fiber Reinforced Plastics", dumbbell-shaped or straight-bar-shaped specimens are used, with a thickness of 2±0.2 mm (controlled by ply layup), a width of 15 mm, a length of 250 mm, and a gauge length of 100 mm. Reinforcing sheets (aluminum sheets or glass fiber reinforcing sheets) are attached to both ends, and the reinforcing sheet material is bonded to the specimen with epoxy adhesive.

[0038] Measure the actual width and thickness of each group of specimens to an accuracy of 0.02 mm and 0.01 mm, respectively. Clamp both ends of the specimen in the universal testing machine fixture, adjust the fixture pressure to prevent slippage, and ensure that the specimen axis is aligned with the loading direction. Set the loading rate to 2 mm / min, start the testing machine, and continuously load until the specimen breaks. Record the maximum load, breaking load, and corresponding displacement. Collect the deformation within the gauge length using an extensometer (100 mm gauge length). Calculate the tensile strength (MPa) and tensile modulus (GPa) of each group of specimens, and take the average value. The formula is as follows: Where σt is the tensile strength in MPa; F is the maximum failure load in N; b is the specimen width in mm; and h is the specimen thickness in mm. Et is the tensile modulus, in MPa; ΔF is the load increment corresponding to the initial linear segment, in N; Δε is the strain increment (dimensionless) corresponding to ΔF, calculated by dividing the deformation ΔL measured by an extensometer (gauge length 100 mm) by the gauge length L0, i.e., Δε = ΔL / L0; b and h are the same as above.

[0039] Referring to GB / T 1449-2005 "Test Method for Bending Properties of Fiber Reinforced Plastics", the specimen dimensions are 80 mm in length, 15 mm in width, and 4 ± 0.2 mm in thickness (controlled by the core layer and layup). The span is set at a thickness ratio of 16:1, i.e., a span of 64 mm. The actual width and thickness of each group of specimens are measured. The specimens are placed on the three-point bending fixture of a universal testing machine, with the loading head parallel to the support axis, the specimen width direction perpendicular to the loading direction, and the core layer centered. The loading rate is set to 5 mm / min. The testing machine is started, and the loading head continuously applies load until the specimen breaks or the maximum deflection reaches 1.5 times the span. The maximum load and corresponding deflection are recorded. The bending strength (MPa) and bending modulus (GPa) of each group of specimens are calculated, and the average value is taken. The formula is as follows: Where σf is the bending strength in MPa; F is the maximum failure load in N; L is the span in mm, which was set to 64 mm in this test; b is the specimen width in mm; and h is the specimen thickness in mm. Ef is the bending modulus, in megapascals (MPa); ΔF is the load increment corresponding to the initial linear segment, in kilometres (N); Δs is the mid-span deflection increment corresponding to ΔF, in mm; L, b, and h are the same as above.

[0040] Referring to GB / T 30969-2014 "Test Method for Shear Strength of Short Beams of Polymer-Based Composite Materials", the specimen dimensions were 24 mm in length, 8 mm in width, and 4 ± 0.2 mm in thickness. The span was set to 4 times the thickness, i.e., 16 mm. The actual thickness and width of each group of specimens (except for Comparative Example 6) were measured. The specimens were placed in the three-point bending fixture of the universal testing machine (indenter and support radius 3 mm), with the core layer near the neutral layer, and the loading indenter aligned with the center of the specimen. The loading rate was set to 1 mm / min, and the testing machine was started. The indenter was applied until interlaminar shear failure occurred (significant delamination or a sudden drop in load). The maximum failure load was recorded. The interlaminar shear strength (MPa) was calculated, and the average value was taken. The formula is as follows: Where Fsbs is the short beam shear strength (i.e., interlaminar shear strength), in MPa; P is the maximum failure load, in N; b is the specimen width, in mm; and h is the specimen thickness, in millimeters (mm).

[0041] The results are shown in Table 1:

[0042] (II) Glass transition temperature test: Referring to GB / T 19466.2-2004 "Differential Scanning Calorimetry (DSC) for Plastics - Part 2: Determination of Glass Transition Temperature", samples were taken from the resin-rich area (fiber-free region) or from resin powder after grinding to remove fibers in each group of samples. 10 mg of sample was weighed and placed in an aluminum crucible, sealed, and then punctured. The sample crucible and an empty reference crucible were placed in the furnace of the differential scanning calorimeter. The heating program was set as follows: heating from room temperature to 200 °C at 10 °C / min, holding at that temperature for 5 min to eliminate thermal history; then cooling to room temperature at 20 °C / min; finally, heating again at 10 °C / min to 250 °C. The heat flow curve during the second heating process was recorded. The midpoint temperature of the curve step was taken as the glass transition temperature (Tg). Three parallel samples were tested in each group, and the average value was taken. The results are shown in Table 2.

[0043] (III) Water absorption rate test: Referring to GB / T 1034-2008 "Determination of Water Absorption of Plastics", the sample size is a square sample with a side length of 50±1 mm and a thickness equal to the actual thickness of the composite material plate. Each group of samples was dried in a 50℃ oven for 24 h until constant weight, and the dried mass m0 (accurate to 0.1 mg) was measured. The sample was then completely immersed in distilled water at 23±2℃ for 24 h. The sample was removed, and surface moisture was absorbed with clean filter paper. Within 1 minute of removal, the mass m1 (accurate to 0.1 mg) after immersion was measured. The water absorption rate was calculated, with 5 parallel samples tested per group, and the average value was taken. The formula is as follows: The results are shown in Table 3:

[0044]

[0045] Table 1 shows that the tensile strength, tensile modulus, flexural strength, flexural modulus, and interlaminar shear strength of Examples 1-4 are significantly higher than those of Comparative Examples 1-6. This indicates that the present invention effectively improves the mechanical properties of the composite material through specific raw material combinations and preparation processes.

[0046] Compared to Example 1, Comparative Example 1 showed a significant decrease in all mechanical properties. This is because the participation of dicyclopentadiene in the copolymerization reaction introduces rigid structural units, which help maintain and enhance the overall modulus and thermal stability of the resin matrix, providing a foundation for the material's load-bearing capacity. The lack of dicyclopentadiene reduces the number of rigid structural units, leading to a decrease in the material's mechanical properties.

[0047] Compared to Example 2, Comparative Example 2 also showed a significant decrease in mechanical properties. The flexible hydrophobic side chains introduced by isobornyl acrylate can create more free volume in the polymer network, which is beneficial for absorbing and dissipating external impact energy, thereby improving the fracture toughness of the matrix. Without this component, the toughness of the material deteriorates, and the mechanical properties are affected.

[0048] Compared to Example 3, Comparative Example 3 showed a decrease in mechanical properties. Styrene plays an important role in the copolymerization reaction, acting together with dicyclopentadiene and isobornyl acrylate to form copolymers with specific properties. The absence of styrene alters the structure and properties of the copolymer, leading to a decrease in mechanical properties.

[0049] Compared to Example 4, Comparative Example 4 exhibits significantly worse mechanical properties. The modified resin matrix formed by mixing biphenyl epoxy resin with terpolymers, etc., makes a significant contribution to the mechanical properties of the material. The absence of biphenyl epoxy resin alters the properties of the modified resin matrix, thereby affecting the overall mechanical properties of the composite material.

[0050] Comparative Example 5 showed a significant decrease in all mechanical properties. 4,4'-Diaminodiphenyl sulfone may act as a curing agent or accelerator in the modified resin matrix, significantly influencing the resin's curing process and properties. The absence of this component resulted in poor resin curing and a significant decline in the material's mechanical properties.

[0051] Comparative Example 6 exhibits extremely low tensile strength, tensile modulus, flexural strength, and flexural modulus, and its interlaminar shear strength cannot be measured. Carbon fiber reinforcement is the primary load-bearing component of the composite material, and its high strength and high modulus play a decisive role in the composite's mechanical properties. Without carbon fiber reinforcement, the material cannot effectively withstand external forces, resulting in extremely poor mechanical properties.

[0052] As shown in Table 2, the glass transition temperatures (Tg) of Examples 1-4 are all higher than those of Comparative Examples 1-6. The higher Tg indicates that the materials have better heat resistance and can maintain better performance stability under high temperature environments.

[0053] Compared to the corresponding examples, Comparative Examples 1-3 showed a decrease in heat resistance (Tg). This is because the specific structures formed during the copolymerization reaction of dicyclopentadiene, isobornyl acrylate, and styrene contribute to the heat resistance of the material. The absence of any one of these components alters the structure of the copolymer, leading to a decrease in Tg.

[0054] The heat resistance (Tg) of Comparative Example 4 was significantly lower than that of Example 4. The addition of biphenyl epoxy resin plays an important role in improving the heat resistance of the material; the absence of this component significantly reduces the Tg. The Tg of Comparative Example 5 was also significantly reduced. 4,4'-Diaminodiphenyl sulfone has a significant impact on the curing process and properties of the resin; the absence of this component results in poor resin curing, leading to decreased heat resistance and a lower Tg.

[0055] Although the Tg value of Comparative Example 6 is close to that of some of the embodiments, the overall performance of the material is fundamentally different from that of the embodiments due to the absence of carbon fiber reinforcement. Carbon fiber reinforcement not only affects mechanical properties but may also have a synergistic effect on the material's heat resistance.

[0056] As shown in Table 3, the water absorption rates of Examples 1-4 are all lower than those of Comparative Examples 1-6. The lower water absorption rate indicates that the material has better waterproof performance and can maintain better performance stability in humid environments.

[0057] The water absorption rates of Comparative Examples 1-3 are higher than those of the corresponding examples. This is because in the copolymer formed by dicyclopentadiene, isobornyl acrylate, and styrene, the hydrophobic groups introduced by isobornyl acrylate can reduce the overall polarity of the resin, which helps to slow down the penetration and diffusion rate of water molecules. The absence of any of these components reduces the number of hydrophobic groups, thus increasing the water absorption rate of the material.

[0058] The water absorption rate of Comparative Example 4 was higher than that of Example 4. The structure and properties of the modified resin matrix formed by mixing biphenyl epoxy resin with terpolymers, etc., affect the water absorption rate of the material. The absence of biphenyl epoxy resin increased the water absorption rate of the material.

[0059] The water absorption rate of Comparative Example 5 was significantly higher than that of Example 1. 4,4'-Diaminodiphenyl sulfone has an important influence on the curing process and performance of the resin. Without this component, the curing effect of the resin is poor, which may lead to more pores or defects inside the material, making it easier for water to penetrate and significantly increasing the water absorption rate.

[0060] Comparative Example 6 showed a higher water absorption rate. The interfacial bonding between the carbon fiber reinforcement and the resin matrix also affects the material's water absorption rate. Without the carbon fiber reinforcement, the material's structure and properties change, potentially leading to an increase in water absorption.

[0061] In summary, this invention introduces rigid structural units and flexible hydrophobic side chains into the copolymer molecular chain through the copolymerization reaction of dicyclopentadiene, isobornyl acrylate, and styrene. Simultaneously, it forms a modified resin matrix by combining biphenyl epoxy resin and 4,4'-diaminodiphenyl sulfone. The rigid structural units enhance the material's modulus and thermal stability, while the flexible hydrophobic side chains improve fracture toughness and reduce water absorption. A symmetrical layup combined with a multi-angle fiber orientation laminate design, along with a lightweight closed-cell foam core layer, constructs a "sandwich" composite structure that effectively transfers and disperses loads, reduces stress concentration, improves flexural stiffness and weight efficiency, and inhibits crack propagation.

[0062] In the description of this specification, the terms "preparation example," "example," "various examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that example or preparation example, which are included in at least one example or preparation example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same example or preparation example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more examples or preparation examples.

[0063] 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 method for preparing a lightweight carbon fiber composite hull material for kayaks, characterized in that, Includes the following steps: S1. Dicyclopentadiene, isobornyl acrylate, and styrene are mixed and copolymerized under the action of an initiator to obtain a terpolymer; the terpolymer is then mixed with biphenyl epoxy resin and 4,4'-diaminodiphenyl sulfone to obtain a modified resin matrix. S2. The modified resin matrix is ​​made into a resin film, and then combined with the carbon fiber reinforcement by hot melt method to obtain carbon fiber prepreg; S3. The carbon fiber prepreg is laid up according to the ply structure, and a core layer is added. After encapsulation, it is cured by autoclave process to obtain composite hull material.

2. The method for preparing a lightweight carbon fiber composite hull material for kayaks according to claim 1, characterized in that, The copolymerization reaction in step S1 is as follows: Dicyclopentadiene, isobornyl acrylate, and styrene were added to a reactor, followed by N-methylpyrrolidone. The mixture was stirred thoroughly and heated in a constant-temperature water bath under nitrogen protection. The initiator solution was added dropwise while stirring. After the addition was complete, dodecanethiol was added, and the temperature was maintained to initiate the polymerization reaction for 10-24 hours. After the reaction was completed, the mixture was cooled to room temperature, and hydroquinone ethanol solution was added to the reaction system to terminate the reaction. The product was separated and purified to obtain a white solid powder terpolymer.

3. The method for preparing a lightweight carbon fiber composite hull material for kayaks according to claim 1, characterized in that, In step S1, the mass ratio of the terpolymer, biphenyl epoxy resin and 4,4'-diaminodiphenyl sulfone is (20-40):(50-80):(5-20).

4. The method for preparing a lightweight carbon fiber composite hull material for kayaks according to claim 1, characterized in that, In step S2, the thickness of the resin film is 0.05-0.20 mm, and the carbon fiber reinforcement is a unidirectional fabric, plain weave fabric, or twill weave fabric woven from high-strength carbon fiber of T700 grade or above. During hot melt lamination, the temperature of the lamination roller is controlled at 80-90℃, the pressure is 0.3-0.8 MPa, and the lamination linear speed is 0.5-2.0 m / min, resulting in a carbon fiber prepreg with a resin mass content of 35-45%.

5. The method for preparing a lightweight carbon fiber composite hull material for kayaks according to claim 1, characterized in that, In step S3, the layup structure is symmetrically distributed, with the core layer as the center and carbon fiber prepreg laid symmetrically above and below. The total number of layups is 8-20 layers, with 4-10 layers of carbon fiber prepreg laid above the core layer and 4-10 layers of carbon fiber prepreg laid below the core layer. The number of layups in the upper and lower layers is the same and the structure is symmetrical. The fiber direction angle between two adjacent layers of carbon fiber prepreg is 30°-90°.

6. The method for preparing a lightweight carbon fiber composite hull material for kayaks according to claim 1, characterized in that, In step S3, the core layer is made of lightweight closed-cell foam material, selected from polyvinyl chloride foam, polyimide foam, or polyurethane foam. The thickness of the core layer is 5-20 mm, and the areal density is 30-80 g / m³. 2 .

7. The method for preparing a lightweight carbon fiber composite hull material for kayaks according to claim 1, characterized in that, The autoclave curing process parameters in step S3 are as follows: curing temperature 120-160℃, heating rate 2-5℃ / min, curing pressure 0.5-1.2MPa, and constant temperature curing time 2-4h.

8. The method for preparing a lightweight carbon fiber composite hull material for kayaks according to claim 2, characterized in that, The mass ratio of dicyclopentadiene, isobornyl acrylate, and styrene is (18.8-21.2):(44.3-55.7):(36.9-43.1). The initiator is selected from benzoyl peroxide and azobisisobutyronitrile. The amount of initiator added is 0.3-0.8% of the total mass of dicyclopentadiene, isobornyl acrylate, and styrene. The amount of dodecanethiol added is 0.01-0.03% of the total mass of dicyclopentadiene, isobornyl acrylate, and styrene.

9. The method for preparing a lightweight carbon fiber composite hull material for kayaks according to claim 2, characterized in that, The temperature is raised to 75-85℃ in a constant temperature water bath, and the stirring rate is controlled at 200-350r / min. The initiator solution is prepared using N-methylpyrrolidone as the solvent, with a mass ratio of initiator to N-methylpyrrolidone of (1-3):

10. The dropping rate is 1-3 drops / second, and the dropping time is controlled at 15-30min.

10. A lightweight carbon fiber composite hull material for kayaks prepared by the method according to any one of claims 1-9, characterized in that, It includes an inner skin layer, a core layer, and an outer skin layer arranged sequentially from the inside out. Both the inner skin layer and the outer skin layer are formed by curing carbon fiber prepreg.

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