Aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material and preparation method thereof

Abstract

The invention discloses an aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material and a preparation method thereof. According to the invention, a fiber metal laminate (FMLs) structure is utilized for the first time, the biological epoxy resin is adopted, and a VARTM process is combined, so that the biological epoxy resin is uniformly distributed in fibers, good interface adhesion is provided between a metal layer and a fiber fabric, and the composite material shows excellent performance; in addition, the sisal fibers and the pineapple leaf fibers are applied to the composite material to replace a part of carbon fibers, so that wastes are effectively reduced, and the material cost is reduced; results show that the composite material not only has excellent mechanical properties, but also improves environmental friendliness; the environment-friendly requirement is met, good balance between performance and cost is achieved, and a new direction is provided for future material development.

Description

Technical Field

[0001] The present invention belongs to the technical field of automotive materials, and particularly relates to a composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber and a preparation method thereof. Background Art

[0002] In order to achieve sustainable development, automobile manufacturers are actively innovating new materials to replace traditional metals. These materials can not only improve fuel efficiency but also reduce manufacturing costs without sacrificing safety. Currently, materials widely used in the automotive industry include aluminum alloys and carbon fiber composites. These materials are favored for their lightweight and high-strength characteristics. Aluminum alloys are widely used due to their excellent corrosion resistance and workability, while carbon fiber composites are an ideal choice for high-performance automobiles because of their excellent strength-to-weight ratio. Although existing aluminum alloys and carbon fiber composites perform well in many aspects, there are still deficiencies in terms of cost, environmental impact, and performance balance. The high cost of carbon fiber limits its large-scale application, while the production process of aluminum alloys is accompanied by high energy consumption and carbon emissions. In addition, the sustainability of existing composite materials is poor and it is difficult to meet the increasing environmental protection requirements.

[0003] With the remarkable development of materials science and the improvement of environmental protection awareness, the demand for more environmentally friendly materials, known as "eco-composites", is increasing. Therefore, researchers are committed to the research and development of bio-fiber metal laminates (Bio-FMLs), especially using natural fibers from natural resources. Sisal fiber (KF) is a natural fiber extracted from the sisal plant and is known for its high strength and lightweight characteristics. Due to its renewability and biodegradability, sisal fiber is considered an environmentally friendly material suitable for enhancing the strength and sustainability of composite materials. At the same time, the amount of pineapple leaf waste as agricultural waste is huge, and the utilization of pineapple leaves is very limited. If the pineapple leaf waste in agricultural waste can be converted into pineapple leaf fiber and applied to engineering composite materials, it can not only effectively reduce agricultural waste but also improve the environmental friendliness and sustainability of the materials.

[0004] Vacuum-assisted resin transfer molding (VARTM) is a single-sided rigid mold composite material production technology; this process first coats the mold surface with a release agent and a gel coat. Subsequently, the metal layer and dry fiber fabric are arranged on the mold and covered with a flexible bag film; then, a vacuum is generated in the mold cavity to guide the resin into the mold. Once the cavity is filled with resin, the material will cure and form a composite material. The VARTM process has many advantages in manufacturing fiber metal laminates (FMLs), and can produce composite components with high fiber content, low void ratio, and excellent wetting of the reinforcement material. In addition, this process is cost-effective and time-saving, while maintaining a harmonious balance among performance, precision, and cost. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this purpose, the main object of the present invention is to provide a composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber. By applying sisal fiber and pineapple leaf fiber to the composite material to replace a part of carbon fiber, not only can waste be effectively reduced, but also excellent mechanical properties and environmental benefits can be provided for the material.

[0006] The present invention also provides a preparation method of the composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A preparation method of a composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber includes the following steps:

[0009] 1) Pretreat the selected aluminum alloy;

[0010] 2) Modify the pineapple leaf fiber / sisal fiber composite woven fabric;

[0011] 3) Modify the bio-epoxy resin;

[0012] 4) Synthesize the composite material by vacuum-assisted resin transfer molding process.

[0013] In some specific embodiments, the pretreatment in step 1) includes: sequentially drilling, grinding, etching, and anodizing the aluminum alloy.

[0014] In some specific embodiments, the pineapple leaf fiber / sisal fiber composite woven fabric in step 2).

[0015] In some specific embodiments, the modification treatment in step 2) is specifically: impregnate the pineapple leaf fiber / sisal fiber composite woven fabric with sodium hydroxide solution, then wash it to neutral and dry it to obtain the modified pineapple leaf fiber / sisal fiber composite woven fabric.

[0016] In some specific embodiments, the modification treatment in step 3) is specifically: add carbon nanotubes to the epoxy resin and mix evenly to obtain the bio-epoxy resin.

[0017] In some specific embodiments, the carbon nanotubes are 30 - 50 μm in length, 6 - 12 nm in outer diameter, and 2 - 4 nm in inner diameter.

[0018] In some specific embodiments, the mass ratio of the carbon nanofibers in the epoxy resin is 0.2 - 0.5 wt%.

[0019] In some specific embodiments, the vacuum-assisted resin transfer molding process described in step 4) is specifically as follows:

[0020] 1) Stack aluminum alloy, carbon fiber, pineapple leaf fiber / sisal fiber composite woven fabric, carbon fiber and aluminum alloy, release cloth, and impregnation mesh in sequence, then cover the entire stack with a polyethylene vacuum bag and fix it on a glass mold;

[0021] 2) Mix bio-epoxy resin with a curing agent, perform degassing treatment, then transfer it to a feed storage tank, and turn on the vacuum pump to allow the resin to fully impregnate the composite material.

[0022] As the same inventive concept, the present invention also provides a composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber prepared by the described preparation method, which includes a pineapple leaf fiber / sisal fiber composite woven fabric, and carbon fiber and aluminum alloy are sequentially arranged on the upper and lower surfaces of the pineapple leaf fiber / sisal fiber composite woven fabric, and bio-epoxy resin containing carbon nanotubes is filled between the aluminum alloy, carbon fiber, pineapple leaf fiber / sisal fiber composite woven fabric, carbon fiber and aluminum alloy.

[0023] In some specific embodiments, the thickness of the aluminum alloy is 0.2 - 0.6 mm, the thickness of the carbon fiber is 0.2 - 0.4 mm, and the thickness of the pineapple leaf fiber / sisal fiber composite woven fabric is 0.6 - 1.0 mm.

[0024] Compared with the prior art, the present invention has at least the following advantages:

[0025] 1) The composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber provided by the present invention not only has mechanical properties equivalent to those of existing aluminum alloy carbon fiber composite materials, but also improves environmental friendliness. For example, it has 1) lightweight: while maintaining structural strength, it reduces the vehicle body weight and improves fuel efficiency; 2) cost reduction: using renewable pineapple leaf fiber and sisal fiber to replace part of the carbon fiber material reduces the material cost; 3) environmental protection: by using natural fibers and bio-epoxy resin, it reduces the environmental impact and conforms to the trend of green manufacturing; replacing part of the carbon fiber reduces the cost and conforms to the development direction of future automotive green materials. Therefore, this new composite material provides more possibilities for automotive design, has high practical value in automobiles, and promotes the sustainable development of the industry.

[0026] 2) The preparation method of the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material provided by the present invention firstly utilizes the fiber metal laminate (FMLs) structure, adopts a bio-epoxy resin, and synthesizes a new type of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber green composite material through VARTM. At the same time, the interfacial bonding force is enhanced by modifying natural fibers and bio-epoxy resins, further optimizing the performance of the composite material. The results show that the new material combines the advantages of metals and fiber-reinforced plastics and overcomes the disadvantages of both. At the same time, due to the reduction of void formation during the VARTM process, in the new material prepared by this method, the bio-epoxy resin is evenly distributed in the fibers and provides good interfacial adhesion between the metal layer and the fiber fabric, making the composite material exhibit excellent performance; by applying sisal fibers and pineapple leaf fibers to the composite material to replace part of the carbon fibers, the present invention can not only effectively reduce waste, but also provide excellent mechanical properties and environmental benefits for the material. This innovative method not only responds to environmental protection requirements but also achieves a good balance between performance and cost, providing a new direction for future material development. Brief Description of the Drawings

[0027] In order to more clearly illustrate the specific embodiments of the present invention, the drawings required for use in the specific embodiments or the description of the prior art will be briefly introduced below.

[0028] Figure 1 It is a schematic structural diagram of the aluminum / carbon fiber / pineapple leaf fiber / sisal leaf fiber composite material in the present invention;

[0029] Figure 2 It is a schematic process diagram of synthesizing the composite material by using the vacuum-assisted resin transfer molding process in the preparation method of the present invention. Specific Embodiments

[0030] The present invention will be further described in detail below in conjunction with the drawings and embodiments. The following embodiments are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0031] When expressing a certain quantity, concentration or other value or parameter in the form of a range, a preferred range, or a preferred upper limit and lower limit of a value, it should be understood that any range is equivalently disclosed by combining any pair of upper limits of the range or preferred values with any lower limit of the range or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values listed herein include the endpoints of the range and all integers and fractions within the range.

[0032] Unless otherwise stated, all percentages, parts, ratios, etc. in this article are by weight.

[0033] The materials, methods, and examples in this article are all exemplary and should not be construed as restrictive unless otherwise specified.

[0034] In the following examples, the carbon nanotubes have a length of 30 - 50 μm, an outer diameter of 6 - 12 nm, and an inner diameter of 2 - 4 nm;

[0035] The pineapple leaf fiber / sisal fiber composite woven fabric is purchased from MSEB Company with an average thickness of 0.8 mm; among which the mixing and weaving direction of pineapple leaf fiber and sisal fiber is (+45°, -45°), and pineapple leaf fiber and sisal fiber are mixed and woven in a ratio of 1:1; and the carbon fiber is purchased from MSEB Company, the weaving direction of the carbon fiber is (+90°, -90°), and the thickness is 0.28 mm.

[0036] Among them, the epoxy resin is the bio - epoxy resin SR GreenPoxy 28 and the curing agent SD3304 selected from Sicomin Company, where the density of the bio - epoxy resin is 1.17 g / cm 3 , the tensile strength is 67 MPa, and the tensile modulus is 3.3 GPa.

[0037] In the following examples, the average length of the carbon nanotubes is 40 μm, the average outer diameter is 8 nm, and the average inner diameter is 3 nm.

[0038] The test methods adopted in the following examples include:

[0039] By separately testing the main properties of each test sample, the inter - layer bonding force performance of the product is reflected; the main properties tested in this application include shear strength, etc.

[0040] 1) Inter - layer bonding force test;

[0041] Equipment: Instron 5967 universal testing machine. The test method is carried out according to the ASTM D2344 standard; sample size: 40 mm × 12 mm. Keep an overhead speed of 1 mm / min throughout the test. The ratio of length to thickness is always kept at 4:1 to reduce tensile and compressive stresses and cause shear failure.

[0042] 2) Mechanical mechanical property test

[0043] Among them, for tensile test: Instron 3382 equipment is used, and the test method is carried out according to the ASTM D3039 standard; for bending test: Instron 5567 equipment is used, and the test method is carried out according to the ASTM°D790 standard; for impact test: Imatek IM10 equipment is used, and the test method is carried out according to the ASTM D7136 standard.

[0044] Example 1

[0045] This embodiment provides a method for preparing a composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber, which comprises the following steps:

[0046] 1) Pretreat the selected aluminum alloy;

[0047] Select an Aluminum 6061-T6 aluminum plate with a specification model of 0.4×300×300 mm, and drill round holes with a diameter of 1 mm on the aluminum plate at a spacing of 75 mm through water jet cutting to enhance the resin penetration during the vacuum assisted resin transfer molding (VARTM) process; then mechanically abrade the aluminum plate with 180-grit sandpaper, and then perform NaOH alkaline etching and sulfuric acid anodic oxidation (specifically: the process parameters of NaOH alkaline etching are: NaOH concentration: 5%; temperature: 60°C; treatment time: 50 seconds; immediately rinse with deionized water after completion and dry naturally; the process parameters of sulfuric acid anodic oxidation are: sulfuric acid concentration: 15%, current density: 1.2 - 1.5 A / dm 2 , voltage: 15 V (DC), temperature: 20±2°C, time: 30 minutes, oxide layer thickness: about 10 - 15 μm (corresponding roughness ~2 μm); rinse with deionized water after completion and dry naturally), to increase the surface roughness (its roughness is 2 μm), thereby enhancing the adhesion between the aluminum sheet and the fiber reinforced plastic layer.

[0048] 2) Modify the pineapple leaf fiber / sisal fiber composite fabric;

[0049] Immerse the dried pineapple leaf fiber / sisal fiber composite fabric (where the ratio of pineapple leaf fiber to sisal fiber is 1:1) in 1000 ml of a sodium hydroxide (NaOH) solution with a weight percentage of 3% at room temperature for 30 - 60 min; the weight ratio of the NaOH solution to the pineapple leaf fiber / sisal fiber composite fabric is fixed at 20:1; then wash the impregnated pineapple leaf fiber / sisal fiber composite fabric with distilled water multiple times until the pH value is neutral, and then dry the washed pineapple leaf fiber / sisal fiber composite fabric in a drying oven at 70°C for 5 hours and place it at room temperature for 3 days to obtain the modified pineapple leaf fiber / sisal fiber composite fabric.

[0050] 3) Prepare the composite epoxy resin;

[0051] Add carbon nanotubes (CNTs) with a weight percentage of 0.2 wt% of the epoxy resin to the epoxy resin using a magnetic stirrer and mix for 10 minutes, and then disperse it with an ultrasonic disperser to obtain the composite epoxy resin;

[0052] 4) Synthesize the composite material by vacuum assisted resin transfer molding process (as Figure 2 shown);

[0053] a) Clean the surface of the glass mold with acetone to remove impurities and dirt, then apply three layers of wax on the glass mold and let it harden for 20 minutes for easy removal, and then wipe off the wax; then stack the materials, and the stacking order of each material is: stack a metal / fiber composite preform (where the metal / fiber composite preform includes aluminum alloy, carbon fiber, pineapple leaf fiber / sisal fiber composite woven fabric, carbon fiber, and aluminum alloy stacked in sequence) on the glass mold, one layer of release cloth, one layer of impregnation net, then cover the entire stack with a polyethylene vacuum bag and fix it on the glass mold with sealing tape; connect the feed pipe to the resin storage tank and the outlet pipe to the vacuum pump;

[0054] b) Mix the composite epoxy resin and the curing agent with a mass ratio of 100:24 evenly, and then quickly perform a 5-minute degassing treatment using an ultrasonic device to obtain the impregnating epoxy resin;

[0055] c) Transfer the impregnating epoxy resin to the resin storage tank through the feed pipe, and inject the impregnating epoxy resin under a pressure of 60 kPa by the vacuum pump. During the impregnation process, when the impregnating epoxy resin is distributed to the middle of the layers of the metal / fiber composite preform, the pressure is increased to 100 kPa; when the impregnating epoxy resin completely wets the metal / fiber composite preform, turn off the vacuum pump to obtain the impregnated composite material;

[0056] d) Let it stand for 24 hours, cool the impregnated composite material to room temperature to ensure that the impregnated composite material is completely cured. Finally, remove the vacuum bag and the release cloth to obtain the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material (the structure is as Figure 1 shown).

[0057] Example 2

[0058] This example provides a method for preparing an aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material, which includes the following steps:

[0059] 1) Pretreat the selected aluminum alloy;

[0060] Select an Aluminum 6061-T6 aluminum plate with a specification of 0.4×300×300 mm. Drill round holes with a diameter of 1 mm on the aluminum plate at a spacing of 75 mm through water jet cutting to enhance the resin penetration during the vacuum-assisted resin transfer molding (VARTM) process; then mechanically abrade the aluminum plate with 180-grit sandpaper, and then use NaOH alkaline etching and sulfuric acid anodizing (specifically: the process parameters of NaOH alkaline etching are: NaOH concentration: 5%; temperature: 60°C; treatment time: 50 seconds; immediately rinse with deionized water after completion and dry naturally; the process parameters of sulfuric acid anodizing are: sulfuric acid concentration: 15%, current density: 1.2 - 1.5 A / dm 2 , voltage: 15 V (DC), temperature: 20±2°C, time: 30 minutes, oxide layer thickness: about 10 - 15 μm (corresponding roughness ~2 μm); rinse with deionized water after completion and dry naturally), to increase the surface roughness (its roughness is 2 μm), thereby enhancing the adhesion between the aluminum sheet and the fiber-reinforced plastic layer,

[0061] 2) Modify the pineapple leaf fiber / sisal fiber composite woven fabric;

[0062] Immerse the dry pineapple leaf fiber / sisal fiber composite woven fabric (where the ratio of pineapple leaf fiber to sisal fiber is 1:1) in 1000 ml of sodium hydroxide (NaOH) solution with a weight percentage of 3% respectively, and the immersion time is 30 - 60 min at room temperature; the weight ratio of the NaOH solution to the pineapple leaf fiber / sisal fiber composite woven fabric is fixed at 20:1; then wash the impregnated pineapple leaf fiber / sisal fiber composite woven fabric with distilled water multiple times until the pH value is neutral, and then dry the washed pineapple leaf fiber / sisal fiber composite woven fabric in an oven at 70°C for 5 hours and place it at room temperature for 3 days to obtain the modified pineapple leaf fiber / sisal fiber composite woven fabric.

[0063] 3) Prepare the composite epoxy resin;

[0064] Add carbon nanotubes (CNTs) with a weight percentage of 0.3 wt% of the epoxy resin to the epoxy resin using a magnetic stirrer and mix for 10 minutes, and then disperse it with an ultrasonic disperser to obtain the composite epoxy resin;

[0065] 4) Synthesize the composite material using the vacuum-assisted resin transfer molding process;

[0066] a) Clean the surface of the glass mold with acetone to remove impurities and dirt, then apply three layers of wax on the glass mold and let it harden for 20 minutes for easy removal, and then wipe off the wax; then stack the materials, and the stacking order of each material is: stack a metal / fiber composite preform on the glass mold in sequence (where the metal / fiber composite preform includes aluminum alloy, carbon fiber, pineapple leaf fiber / sisal fiber composite woven fabric, carbon fiber, and aluminum alloy stacked in sequence), a layer of release cloth, a layer of impregnation mesh, then cover the entire stack with a polyethylene vacuum bag and fix it on the glass mold with sealing tape; connect the feed pipe to the resin storage tank and the outlet pipe to the vacuum pump;

[0067] b) Mix the composite epoxy resin and the curing agent with a mass ratio of 100:24 evenly, and then quickly perform a 5-minute degassing treatment using an ultrasonic device to obtain the impregnating epoxy resin;

[0068] c) Transfer the impregnating epoxy resin to the resin storage tank through the feed pipe, and inject the impregnating epoxy resin with a pressure of 60 kPa through the vacuum pump. During the impregnation process, when the impregnating epoxy resin is distributed to the middle of the layers of the metal / fiber composite preform, the pressure is increased to 100 kPa; when the impregnating epoxy resin completely wets the metal / fiber composite preform, turn off the vacuum pump to obtain the impregnated composite material;

[0069] d) Let it stand for 24 hours, cool the impregnated composite material to room temperature to ensure that the impregnated composite material is completely cured. Finally, remove the vacuum bag and the release cloth to obtain the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material.

[0070] Example 3

[0071] This example provides a method for preparing an aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material, which includes the following steps:

[0072] 1) Pretreat the selected aluminum alloy;

[0073] Select an Aluminum 6061-T6 aluminum plate with a specification model of 0.4×300×300 mm, drill round holes with a diameter of 1 mm on the aluminum plate at a spacing of 75 mm through water jet cutting to enhance the penetration of the resin during the vacuum-assisted resin transfer molding (VARTM) process; then mechanically abrade the aluminum plate with 180-grit sandpaper, and then use NaOH alkaline etching and sulfuric acid anodizing (specifically: the process parameters of NaOH alkaline etching are: NaOH concentration: 5%; temperature: 60°C; treatment time: 50 seconds; immediately rinse with deionized water after completion and dry naturally; the process parameters of sulfuric acid anodizing are: sulfuric acid concentration: 15%, current density: 1.2 - 1.5 A / dm 2, Voltage: 15V (DC), Temperature: 20 ± 2 °C, Time: 30 minutes, Oxide layer thickness: approximately 10 - 15 μm (corresponding roughness ~2 μm); After completion, rinse with deionized water and dry naturally), to increase the surface roughness (its roughness is 2 μm), thereby enhancing the adhesion between the aluminum sheet and the fiber-reinforced plastic layer,

[0074] 2) Modify the pineapple leaf fiber / sisal fiber composite fabric;

[0075] Immerse the dried pineapple leaf fiber / sisal fiber composite fabric (where the ratio of pineapple leaf fiber to sisal fiber is 1:1) in 1000 ml of sodium hydroxide (NaOH) solution with a weight percentage of 3% respectively, and the immersion time is 30 - 60 min at room temperature; The weight ratio of the NaOH solution to the pineapple leaf fiber / sisal fiber composite fabric is fixed at 20:1; Subsequently, wash the impregnated pineapple leaf fiber / sisal fiber composite fabric with distilled water multiple times until the pH value is neutral, and then dry the washed pineapple leaf fiber / sisal fiber composite fabric in a drying oven at 70 °C for 5 hours and place it at room temperature for 3 days to obtain the modified pineapple leaf fiber / sisal fiber composite fabric.

[0076] 3) Prepare the composite epoxy resin;

[0077] Add carbon nanotubes (CNTs) with a weight percentage of 0.4 wt% of the epoxy resin to the epoxy resin using a magnetic stirrer and mix for 10 minutes, and then disperse it with an ultrasonic disperser to obtain the composite epoxy resin;

[0078] 4) Synthesize the composite material using the vacuum-assisted resin transfer molding process;

[0079] a) Clean the surface of the glass mold with acetone to remove impurities and dirt, then apply three layers of wax on the glass mold and let it harden for 20 minutes for easy removal, and then wipe off the wax; Then stack the materials, and the stacking order of each material is: Stack the metal / fiber composite preform (where the metal fiber composite preform includes aluminum alloy, carbon fiber, pineapple leaf fiber / sisal fiber composite fabric, carbon fiber, and aluminum alloy stacked in sequence) on the glass mold in turn, one layer of release cloth, one layer of impregnation mesh, then cover the entire stack with a polyethylene vacuum bag and fix it on the glass mold with sealing tape; Connect the feed pipe to the resin storage tank and the outlet pipe to the vacuum pump;

[0080] b) Mix the composite epoxy resin and the curing agent evenly at a mass ratio of 100:24, and then quickly perform a 5-minute degassing treatment using an ultrasonic device to obtain the impregnated epoxy resin;

[0081] c) Transfer the impregnated epoxy resin to the resin storage tank through the feed pipe, and inject the impregnated epoxy resin under a pressure of 60 kPa by a vacuum pump. During the impregnation process, when the impregnated epoxy resin is distributed between the layers of the metal / fiber composite preform, the pressure is increased to 100 kPa; when the impregnated epoxy resin completely wets the metal / fiber composite preform, turn off the vacuum pump to obtain the impregnated composite material;

[0082] d) Let it stand for 24 hours, cool the impregnated composite material to room temperature to ensure complete curing of the impregnated composite material. Finally, remove the vacuum bag and the release cloth to obtain the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material.

[0083] Example 4

[0084] This example provides a method for preparing an aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material, which includes the following steps:

[0085] 1) Pretreat the selected aluminum alloy;

[0086] Select an Aluminum 6061-T6 aluminum plate with a specification of 0.4×300×300 mm, and drill round holes with a diameter of 1 mm on the aluminum plate at a spacing of 75 mm through water jet cutting to enhance the resin penetration during the vacuum-assisted resin transfer molding (VARTM) process; then mechanically abrade the aluminum plate with 180-grit sandpaper, and then perform NaOH alkaline etching and sulfuric acid anodizing (specifically: the process parameters of NaOH alkaline etching are: NaOH concentration: 5%; temperature: 60°C; treatment time: 50 seconds; immediately rinse with deionized water after completion and dry naturally; the process parameters of sulfuric acid anodizing are: sulfuric acid concentration: 15%, current density: 1.2 - 1.5 A / dm 2 , voltage: 15 V (DC), temperature: 20±2°C, time: 30 minutes, oxide layer thickness: about 10 - 15 μm (corresponding roughness ~ 2 μm); rinse with deionized water after completion and dry naturally), to increase the surface roughness (its roughness is 2 μm), thereby enhancing the adhesion between the aluminum sheet and the fiber-reinforced plastic layer,

[0087] 2) Modify the pineapple leaf fiber / sisal fiber composite woven fabric;

[0088] Soak the dry pineapple leaf fiber / sisal fiber composite woven fabric (where the ratio of pineapple leaf fiber to sisal fiber is 1:1) in 1000 ml of sodium hydroxide (NaOH) solution with a weight percentage of 3% respectively, and the soaking time is 30 - 60 min at room temperature; the weight ratio of the NaOH solution to the pineapple leaf fiber / sisal fiber composite woven fabric is fixed at 20:1; then wash the soaked pineapple leaf fiber / sisal fiber composite woven fabric with distilled water multiple times until the pH value is neutral, and then dry the washed pineapple leaf fiber / sisal fiber composite woven fabric in an oven at 70 °C for 5 hours and place it at room temperature for 3 days to obtain the modified pineapple leaf fiber / sisal fiber composite woven fabric.

[0089] 3) Prepare the composite epoxy resin;

[0090] Add carbon nanotubes (CNTs) with a weight percentage of 0.5 wt% of the epoxy resin to the epoxy resin using a magnetic stirrer and mix for 10 minutes, and then disperse it with an ultrasonic disperser to obtain the composite epoxy resin;

[0091] 4) Synthesize the composite material using the vacuum-assisted resin transfer molding process;

[0092] a) Clean the surface of the glass mold with acetone to remove impurities and dirt, then apply three layers of wax on the glass mold and let it harden for 20 minutes for easy removal, and then wipe off the wax; then stack the materials, and the stacking order of each material is: stack the metal / fiber composite preform (where the metal / fiber composite preform includes aluminum alloy, carbon fiber, pineapple leaf fiber / sisal fiber composite woven fabric, carbon fiber, and aluminum alloy) on the glass mold in sequence, one layer of release cloth, one layer of impregnation mesh, then cover the entire stack with a polyethylene vacuum bag and fix it on the glass mold with a sealing tape; connect the feed pipe to the resin storage tank and the outlet pipe to the vacuum pump;

[0093] b) Mix the composite epoxy resin and the curing agent evenly at a mass ratio of 100:24, and then quickly perform a 5-minute degassing treatment using an ultrasonic device to obtain the impregnated epoxy resin;

[0094] c) Transfer the impregnated epoxy resin to the resin storage tank through the feed pipe, and inject the impregnated epoxy resin with a pressure of 60 kPa through the vacuum pump. During the impregnation process, when the impregnated epoxy resin is distributed in the middle of the layers of the metal / fiber composite preform, the pressure is increased to 100 kPa; when the impregnated epoxy resin completely wets the metal / fiber composite preform, turn off the vacuum pump to obtain the impregnated composite material;

[0095] d) Leave it standing for 24 hours, cool the impregnated composite material to room temperature to ensure complete curing of the impregnated composite material. Finally, remove the vacuum bag and release cloth to obtain the composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber.

[0096] Comparative Example 1

[0097] This comparative example provides a preparation method of a composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber, which is basically the same as that of Example 2, except that in step 1), only 180 - grit sandpaper is used for mechanical abrasion of the aluminum plate, without using NaOH alkaline etching and sulfuric acid anodizing; specifically:

[0098] Select an Aluminum 6061 - T6 aluminum plate with a specification of 0.4×300×300 mm, and use a water jet cutter to drill round holes with a diameter of 1 mm on the aluminum plate at a spacing of 75 mm to enhance the resin penetration during the vacuum - assisted resin transfer molding (VARTM) process; then use 180 - grit sandpaper to mechanically abrade the aluminum plate to enhance the adhesion between the aluminum sheet and the fiber - reinforced plastic layer;

[0099] The remaining steps 2), 3) and step 4) are the same as those in Example 2.

[0100] Comparative Example 2

[0101] This comparative example provides a preparation method of a composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber, which is basically the same as that of Example 2, except that the surface modification of the pineapple leaf fiber / sisal fiber composite fabric is not carried out, that is, the modification treatment step of the pineapple leaf fiber / sisal fiber composite fabric is omitted, and the remaining steps 1), 3) and 4) are the same as those in Example 2.

[0102] Comparative Example 3

[0103] This comparative example provides a preparation method of a composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber, which is basically the same as that of Example 2, except that in step 4), the lamination order of each material is changed. Specifically, the original order of carbon fiber / pineapple leaf fiber mixed with sisal fiber / carbon fiber is changed to pineapple leaf fiber mixed with sisal fiber / carbon fiber / pineapple leaf fiber mixed with sisal fiber, specifically:

[0104] 4) Use the vacuum - assisted resin transfer molding process to synthesize the composite material;

[0105] a) Clean the surface of the glass mold with acetone to remove impurities and dirt. Then apply three layers of wax on the glass mold and let it harden for 20 minutes for easy removal, and then wipe off the wax. Then stack the materials. The stacking order of each material is: stack a metal / fiber composite preform (where the metal / fiber composite preform includes successively stacked aluminum alloy, pineapple leaf fiber / sisal fiber composite woven fabric, carbon fiber, pineapple leaf fiber / sisal fiber composite woven fabric, and aluminum alloy) on the glass mold, one layer of release cloth, one layer of impregnation mesh, then cover the entire stack with a polyethylene vacuum bag and fix it to the glass mold with sealing tape. Connect the feed pipe to the resin storage tank and the outlet pipe to the vacuum pump.

[0106] b) Mix the composite epoxy resin and the curing agent with a mass ratio of 100:24 evenly, and then quickly perform a 5-minute degassing treatment using an ultrasonic device to obtain the impregnating epoxy resin.

[0107] c) Transfer the impregnating epoxy resin to the resin storage tank through the feed pipe and inject the impregnating epoxy resin with a pressure of 60 kPa through the vacuum pump. During the impregnation process, when the impregnating epoxy resin is distributed between the layers of the metal / fiber composite preform, the pressure is increased to 100 kPa. When the impregnating epoxy resin completely wets the metal / fiber composite preform, turn off the vacuum pump to obtain the impregnated composite material.

[0108] d) Let it stand for 24 hours, cool the impregnated composite material to room temperature to ensure complete curing of the impregnated composite material. Finally, remove the vacuum bag and the release cloth to obtain the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material.

[0109] Comparative Example 4

[0110] This comparative example provides a method for preparing an aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material, which is basically the same as Example 2, except that carbon nanotubes are not added to the epoxy resin, that is, step 3) is omitted. Specifically:

[0111] Adopt the vacuum-assisted resin transfer molding process to synthesize the composite material.

[0112] a) Clean the surface of the glass mold with acetone to remove impurities and dirt. Then apply three layers of wax on the glass mold and let it harden for 20 minutes for easy removal, and then wipe off the wax. Then stack the materials, and the stacking order of each material is as follows: stack a metal / fiber composite preform on the glass mold in sequence (where the metal / fiber composite preform includes aluminum alloy, carbon fiber, pineapple leaf fiber / sisal fiber composite woven fabric, carbon fiber, and aluminum alloy stacked in sequence), a layer of release cloth, a layer of impregnation mesh, then cover the entire stack with a polyethylene vacuum bag and fix it on the glass mold with sealing tape. Connect the feed pipe to the resin storage tank and the outlet pipe to the vacuum pump.

[0113] b) Mix epoxy resin and curing agent with a mass ratio of 100:24 evenly, and then quickly perform degassing treatment with an ultrasonic device for 5 minutes to obtain impregnated epoxy resin.

[0114] c) Transfer the impregnated epoxy resin to the resin storage tank through the feed pipe, and inject the impregnated epoxy resin with a pressure of 60 kPa through the vacuum pump. During the impregnation process, when the impregnated epoxy resin is distributed between the layers of the metal / fiber composite preform, the pressure is increased to 100 kPa. When the impregnated epoxy resin completely wets the metal / fiber composite preform, turn off the vacuum pump to obtain the impregnated composite material.

[0115] d) Let it stand for 24 hours, cool the impregnated composite material to room temperature to ensure complete curing of the impregnated composite material. Finally, remove the vacuum bag and release cloth to obtain the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material.

[0116] The remaining steps 1) and 2) are the same as those in Example 2.

[0117] Performance test:

[0118] This application conducts performance tests on the composite materials prepared in Examples 1-4 and Comparative Examples 1-4. Specifically:

[0119] 1) Interlaminar bonding force

[0120] This test detects the interlaminar bonding force of the composite material through interlaminar shear strength test (ILSS). The results are shown in Table 1:

[0121] Table 1 Interlaminar bonding force of the composite materials in each example and comparative example

[0122] Serial number Interlayer bonding strength (Mpa) Example 1 23.89 Example 2 26.08 Example 3 30.04 Example 4 25.17 Comparative example 1 18.45 Comparative example 2 20.98 Comparative example 3 19.70 Comparative example 4 19.04

[0123] From the data in the table, it can be seen that from the interlaminar bonding force data of Examples 1 - 3, as the addition amount of carbon nanotubes (CNTs) increases (from 0.2 wt% to 0.4 wt%), the interlaminar bonding force of the composite material increases significantly (from 23.89 MPa to 30.04 MPa). This indicates that the addition of CNTs effectively enhances the mechanical properties of the resin matrix and improves the adhesion between the fiber and the resin through interface strengthening.

[0124] Among them, Example 3 (0.4 wt% CNTs) has the best performance, indicating that the dispersion and content of CNTs within a reasonable range have a positive impact on the properties of the composite material. However, it should be noted that excessive addition (such as 0.5 wt% in Example 4) may lead to agglomeration, resulting in a slight decrease in the bonding force to 25.17 MPa. Therefore, the addition amount of CNTs needs to be controlled within the optimal range.

[0125] Next, from the comparison data between Example 2 and Comparative Examples 1 / 2 / 3 / 4, it can be seen that: Comparative Example 1 (without NaOH alkaline etching and sulfuric acid anodic oxidation): The interlaminar bonding force (18.45 MPa) is significantly lower than that of Example 2 (26.08 MPa), indicating that the surface roughness of the aluminum plate (2 μm) and chemical treatment are crucial for enhancing the adhesion of the aluminum - fiber interface.

[0126] Comparative Example 2 (untreated natural fiber): The bonding force (20.98 MPa) is lower than that of Example 2, indicating that the treatment with NaOH solution can effectively remove the impurities and hydroxyl groups on the surface of pineapple leaf / sisal fibers and improve their compatibility with the resin.

[0127] Comparative Example 3 (changing the stacking order): The bonding force (19.70 MPa) decreases, indicating that carbon fiber as the outer layer (the structure of Example 2) can transfer the load more effectively, while placing natural fiber on the outer layer may lead to interfacial stress concentration.

[0128] Comparative Example 4 (without adding CNTs): The bonding force (19.04 MPa) is the lowest, verifying the reinforcing effect of CNTs on the resin matrix, which improves the mechanical properties and interfacial bonding force of the resin through the nano - effect.

[0129] In summary, through optimizing the surface treatment of the aluminum plate (roughness 2μm), modifying the natural fiber, adjusting the addition amount of CNTs (0.3 - 0.4wt%), and the lamination sequence (carbon fiber coating natural fiber), the composite material of this patent has achieved a significant improvement in the interfacial bonding strength (up to 30.04MPa). From the comparison with the data of the comparative examples, it can be seen that the absence or modification of any link (such as untreated aluminum plate, unmodified fiber, adjusted lamination sequence, or omitted CNTs) will lead to a decline in performance, indicating that the various technical solutions in this application, namely, the composite material of this patent through optimizing the surface treatment of the aluminum plate (roughness 2μm), modifying the natural fiber, adjusting the addition amount of CNTs (0.3 - 0.4wt%), and the lamination sequence (carbon fiber coating natural fiber), work synergistically.

[0130] 2) Mechanical properties

[0131] Taking Example 3 of this application as an example, the mechanical properties of the prepared aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material were tested. Specifically:

[0132] Table 2 Mechanical properties of the composite material in Example 3

[0133] Performance parameters Example 3 Tensile strength (Mpa) 458.52 Flexural strength (Mpa) 420.21 Impact energy (J) 20

[0134] From the data in Table 2, it can be seen that the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material provided in this application has significantly improved its mechanical properties by optimizing the preparation process and material combination. That is, the composite material in this application has excellent mechanical properties, improves environmental friendliness, reduces costs by replacing part of the carbon fiber, and conforms to the development direction of future automotive green materials. Therefore, the hybrid Al / CF / PALF composite material has high practical value in automobiles.

[0135] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A preparation method of an aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material, characterized in that, It includes the following steps: 1) Pretreat the selected aluminum alloy; 2) Modify the pineapple leaf fiber / sisal fiber composite fabric; 3) Modify the bio-epoxy resin; 4) Synthesize the composite material by vacuum-assisted resin transfer molding process.

2. The preparation method of the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material according to claim 1, wherein The pretreatment described in step 1) includes: sequentially drilling, grinding, etching, and anodizing the aluminum alloy.

3. The preparation method of the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material according to claim 1, characterized in that, The pineapple leaf fiber / sisal fiber composite fabric described in step 2).

4. The preparation method of the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material according to claim 1, characterized in that, The specific modification treatment in step 2) is: impregnate the pineapple leaf fiber / sisal fiber composite fabric with sodium hydroxide solution, then wash it to neutral and dry it to obtain the modified pineapple leaf fiber / sisal fiber composite fabric.

5. The preparation method of the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material according to claim 4, wherein, The specific modification treatment in step 3) is: add carbon nanotubes to the epoxy resin and mix evenly to obtain the bio-epoxy resin.

6. The preparation method of the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material according to claim 1, characterized in that, The carbon nanotubes are 30 - 50 μm in length, 6 - 12 nm in outer diameter, and 2 - 4 nm in inner diameter.

7. The preparation method of the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material according to claim 7, characterized in that, The mass ratio of the carbon nanofibers in the epoxy resin is 0.2 - 0.5 wt%.

8. The preparation method of the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material according to claim 4, characterized in that The specific vacuum-assisted resin transfer molding process in step 4) is: 1) Stack the aluminum alloy, carbon fiber, pineapple leaf fiber / sisal fiber composite fabric, carbon fiber and aluminum alloy, release cloth, and impregnation mesh in sequence, then cover the whole stack with a polyethylene vacuum bag and fix it on a glass mold; 2) Mix the bio-epoxy resin with the curing agent, perform degassing treatment, then transfer it to the feed storage tank, and turn on the vacuum pump to let the resin fully impregnate the composite material.

9. A composite material of aluminum / carbon fiber / pineapple leaf fiber / sisal fiber prepared by the preparation method according to any one of claims 1-8, characterized in that, It includes a pineapple leaf fiber / sisal fiber composite fabric, and carbon fibers and aluminum alloys are sequentially arranged on the upper and lower surfaces of the pineapple leaf fiber / sisal fiber composite fabric, and the bio-epoxy resin containing carbon nanotubes is filled between the aluminum alloy, carbon fiber, pineapple leaf fiber / sisal fiber composite fabric, carbon fiber and aluminum alloy.

10. The preparation method of the aluminum / carbon fiber / pineapple leaf fiber / sisal fiber composite material according to claim 7, characterized in that, The thickness of the aluminum alloy is 0.2 - 0.6 mm, the thickness of the carbon fiber is 0.2 - 0.4 mm, and the thickness of the pineapple leaf fiber / sisal fiber composite fabric is 0.6 - 1.0 mm.

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