A method for preparing a gradient perfusion-based biomimetic porous carbon fiber composite material

Abstract

This application provides a method for preparing biomimetic porous carbon fiber composite materials based on gradient infusion, belonging to the field of additive manufacturing and high-performance composite materials. This method achieves precise distribution and strong interfacial bonding of carbon fibers in a three-dimensional biomimetic interconnected network through a synergistic process of "programmable sacrificial template - gradient pore construction - homologous secondary infusion". First, based on the sea urchin spine structure, a biomimetic sacrificial template is prepared using 3D printing water-soluble photosensitive resin. Second, epoxy resin is vacuum-infused and cured, and the template is removed via a constant-temperature circulating deionized water bath to obtain a three-dimensional interconnected, gradient-controllable pure resin porous skeleton. Finally, homologous epoxy resin slurry containing short-cut carbon fibers is vacuum-infused into the skeleton a second time, and after step-curing, an integrated composite material is formed. This invention solves the common problems of random pores, fiber agglomeration, and weak interfacial bonding by first precisely creating pores and then uniformly fixing fibers, significantly improving the stiffness, strength, and toughness of the composite material.

Description

Technical Field

[0001] This application belongs to the field of additive manufacturing and high-performance composite materials, specifically relating to a method for preparing biomimetic porous carbon fiber composite materials based on gradient infusion process. Background Technology

[0002] In existing technologies, the preparation of biomimetic porous carbon fiber composites mainly employs foaming or pore-forming agent methods. However, the porous structures formed by these methods exhibit random pore morphology and poor connectivity, failing to simulate the gradient pore size characteristics from the core to the surface in natural biomaterials. During load-bearing, stress is transferred to the porous framework through the matrix. Due to the disordered pore distribution, local stress concentration is easily triggered, leading to early failure modes such as framework buckling, matrix cracking, or interlaminar delamination, significantly reducing the material's compressive strength, flexural modulus, and energy absorption efficiency. Under long-term cyclic loading, stress concentration areas also accelerate fatigue crack propagation, severely limiting the service life and reliability of the composite material, making it difficult to meet the stringent mechanical performance requirements for lightweight, high-strength materials in aerospace, biomedical, and other fields.

[0003] To address these issues, researchers have attempted to composite carbon fibers with commercial open-cell foams (such as polyurethane) or construct porous structures using removable templates such as salt particles and polymer microspheres. However, the former suffers from a coarse-grained structure and poor mechanical properties due to the foam template itself, and the weak interfacial bonding between the carbon fibers and the foam matrix prevents the full realization of the fiber's reinforcing potential. The latter, due to the difficulty in precisely controlling the template shape, size, and stacking method, fails to construct a highly interconnected, gradient-variable multi-level biomimetic network structure, resulting in the material still being prone to localized failure under compression and bending loads. None of these methods fundamentally achieve the fabrication of a biomimetic gradient-connected topology, leading to composite materials with compressive strength, flexural strength, and impact resistance far inferior to the biological prototype. Therefore, developing a novel carbon fiber composite material preparation method capable of precisely constructing a gradient-connected porous structure, achieving uniform distribution of the reinforcing phase, and conforming to biomimetic mechanical characteristics is not only of significant engineering importance but also effectively improves the material's compressive strength, flexural modulus, and anti-delamination properties, meeting the urgent demand for lightweight, high-strength materials in high-end fields. Summary of the Invention

[0004] In view of this, this application provides a method for preparing biomimetic porous carbon fiber composite materials based on gradient infusion, in order to solve the technical problem that the existing technology cannot accurately construct high-precision three-dimensional interconnected porous structures, resulting in limited mechanical properties of the materials.

[0005] Specifically, this application is implemented through the following scheme: A method for preparing biomimetic porous carbon fiber composite materials based on gradient infusion, comprising the following steps: Step 1: Using 3D modeling software, construct a cylindrical digital model that mimics the internal structure of sea urchin spines. The cylindrical digital model contains a three-dimensional interconnected network structure; the pore size decreases gradually from the center to the surface, with a porosity of 65%–80%. This gradient design allows the large central pores to absorb energy, while the small surface pores resist impact, reducing the stress concentration factor by more than 30%.

[0006] Step two: Using commercially available water-soluble photosensitive resin as raw material, a physical sacrificial template with the same geometry as the cylindrical digital model is printed using a 3D printer.

[0007] Step 3: Using a two-component epoxy resin system as raw material, a mixed resin is obtained through vacuum degassing. This mixed resin is then poured into a mold containing a template at a pressure of -0.09 to -0.1 MPa and cured in stages at 40 to 65°C to obtain a template-containing resin body. Low viscosity and vacuum ensure complete filling of micropores.

[0008] Step 4: Immerse the resin body in a constant temperature circulating deionized water bath at 45-55℃ to completely dissolve the sacrificial template and carry it out with the water flow, forming a precise negative three-dimensional interconnected pore with a connectivity rate close to 100%.

[0009] Step 5: After ultrasonic cleaning, the component is vacuum dried at 55-65℃ for 10-14 hours to obtain a pure resin porous skeleton with precise three-dimensional connectivity and controllable gradient pore size.

[0010] Step six: Place the pure resin porous skeleton in a silicone mold, and perform a second vacuum infusion of a homologous epoxy resin slurry containing 1-5% short-cut carbon fibers. After holding under pressure for 5-10 minutes, perform a second step-curing process. The resin slurry and the skeleton are homologous, and the interface chemically co-crosslinks during the second curing process. The interfacial shear strength is ≥25MPa, and the carbon fibers form a three-dimensional continuous reinforcing network, resulting in a biomimetic porous carbon fiber composite material.

[0011] The above scheme achieves high-precision design and simultaneous improvement of mechanical properties of biomimetic porous structures by combining high-precision physical sacrificial templates with secondary injection.

[0012] Furthermore, as a preferred option: In step one, the aperture of the three-dimensional connected mesh structure is 50–150 μm, and decreases gradually from the center of the cylindrical digital model towards the surface. More preferably, the aperture at the center is 120–150 μm, and the aperture at the surface is 50–80 μm.

[0013] The porosity of the cylindrical digital model is 65-80%, preferably 70-78%, and more preferably 75%.

[0014] In step three, The two-component epoxy resin system includes epoxy resin and modified amine curing agent, and the mass ratio of epoxy resin to modified amine curing agent is 100:20 to 40, preferably 100:30.

[0015] The viscosity of the resin obtained after vacuum degassing is 300–500 MPa•s.

[0016] The vacuum level of the vacuum infusion is -0.09 to -0.1 MPa.

[0017] The curing temperature is 40–65°C. More preferably, the curing is divided into two stages: the first stage is cured at 40–45°C for 3–4 hours, and the second stage is cured at 50–65°C for 2–3 hours.

[0018] In step four, the temperature of the constant-temperature circulating deionized water bath is 45–55℃, and the immersion time is 20–28 hours.

[0019] In step five, the drying temperature is 55–65°C.

[0020] In step six, The homologous epoxy resin slurry containing 1-5% short-cut carbon fibers includes short-cut carbon fibers and a two-component epoxy resin system consistent with that in step three. The mass percentage of the short-cut carbon fibers in the slurry is 1-5%, preferably 2.5%-3.5%. The two-component epoxy resin system includes epoxy resin and a modified amine curing agent. The mass ratio of epoxy resin to modified amine curing agent is 100:20-40, preferably 100:30.

[0021] The vacuum level of the vacuum infusion is -0.08 to -0.95 MPa.

[0022] The temperature for the second-stage curing is 80–120°C. More preferably, the second-stage curing is divided into two stages: the first stage is cured at 80–95°C for 2–3 hours, and the second stage is cured at 100–120°C for 3–4 hours. For example, the second-stage curing can be completed by using 80°C / 2 hours + 120°C / 3 hours.

[0023] The final composite material has an overall porosity of 30% to 50%, a compressive strength of ≥120MPa, and a flexural strength of ≥180MPa, which are 40% and 35% higher than those of the traditional foaming method, respectively.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the pore structure is transformed from random and disordered to precisely designed. Traditional foaming or pore-forming methods result in porous structures with random pore morphology and poor connectivity, making it impossible to pre-define pore size gradients and connectivity paths. This invention, based on 3D printing sacrificial template technology, can accurately reproduce the geometric and topological features of biomimetic models, allowing pore size, spatial distribution, and connectivity to be fully defined by digital design, thus eliminating stress concentration and performance dispersion caused by pore disorder at the source.

[0025] Second, the distribution of the reinforcing phase transforms from localized agglomeration to a three-dimensional uniform network, and the interfacial bonding mechanism changes from physical adhesion to chemical co-crosslinking. In traditional blending processes, short-cut carbon fibers are prone to localized agglomeration, leading to stress concentration and early failure. This invention uses a three-dimensional interconnected pure resin skeleton as the infusion channel, and through secondary vacuum infusion, the carbon fiber slurry uniformly fills every pore, forming a continuous reinforcing network that runs through the structure. At the same time, the slurry resin and the skeleton resin are homologous systems, and a chemical co-crosslinking reaction occurs at the interface during the secondary curing process. The interfacial shear strength is ≥25 MPa, and the load transfer efficiency is significantly improved, thereby simultaneously enhancing the stiffness, strength, and fracture toughness of the composite material.

[0026] Third, the process is optimized to achieve a balance between high-precision biomimetic configuration and excellent mechanical properties. This invention combines design freedom and molding density in a step-by-step manner, first creating pores and then reinforcing them. The process is clear and controllable, and the resulting composite material has a compressive strength ≥120MPa and a flexural strength ≥180MPa, which are more than 40% and 35% higher than those of the traditional foaming method, respectively. This solves the technical problem of balancing high precision and high performance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application.

[0028] Figure 1 This is a schematic diagram of the preparation process of this application.

[0029] The labels in the figure are as follows: 1. Water-soluble photosensitive resin; 2. Physical sacrificial template; 3. Low viscosity mixed resin; 31. Component A; 32. Component B; 4. Resin cured body containing sacrificial template; 41. Resin cured body; 5. Ultrasonic cleaner; 6. Resin slurry containing chopped carbon fibers; 7. Bionic porous carbon fiber composite material; 71. Pure resin porous skeleton with fixed carbon fibers. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit the technical solutions of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application.

[0031] This embodiment provides a method for preparing biomimetic porous carbon fiber composite materials based on gradient infusion, combined with... Figure 1 The steps are as follows: Step 1: Using the 3D modeling software SolidWorks, construct a cylindrical digital model that mimics the internal structure of sea urchin spines. The cylindrical digital model has a diameter of 20mm and a height of 30mm. It contains a three-dimensional connected network structure with an overall porosity of 75%. The pore size decreases gradually from the center of the cylindrical digital model towards the surface. Specifically, the pore size at the center of the cylindrical digital model is between 120 and 150μm, while the pore size at the surface is between 50 and 80μm.

[0032] Step 2: Using commercial water-soluble photosensitive resin 1 as raw material, a digital light processing 3D printer with a 365nm wavelength light source is used to inject the commercial water-soluble photosensitive resin into the printer's feed tank, import the cylindrical digital model constructed in Step 1, and set the layer thickness to 25μm. Printing is started to print a physical sacrificial template 2. The physical sacrificial template 2 has the same geometry as the cylindrical digital model and contains a three-dimensional connected network structure inside. After printing, the residual resin on the template surface is rinsed with anhydrous ethanol and dried with compressed air for later use.

[0033] Step 3: Using epoxy resin as component A 31 and modified amine curing agent as component B 32, mix them at a mass ratio of component A 31: component B 32 = 100:30 to obtain a two-component epoxy resin system. Stir and degas under vacuum to obtain a low-viscosity mixed resin 3 with a viscosity of about 400 MPa•s.

[0034] Step four: Place the physical sacrificial template 2 in a cylindrical silicone mold with a release agent coated on the inner wall. Seal the mold system with sealing tape and a vacuum bag, and connect it to a vacuum pump. Maintain the system vacuum at -0.095 MPa. Introduce the low-viscosity mixed resin 3 into the silicone mold through a dispensing tube until the low-viscosity mixed resin 3 completely immerses the physical sacrificial template 2. Transfer the resin-filled mold system to an oven for stepped curing: first, cure at 40°C for 4 hours, then cure at 60°C for 2 hours. Upon completion, a resin-cured body 4 containing the undissolved template is obtained, where 41 is the resin-cured body.

[0035] Step 5: Remove the resin cured body 4 containing the sacrificial template from the silicone mold and immerse it in a 50°C constant temperature circulating deionized water bath for 24 hours. During this process, the water-soluble sacrificial template is completely dissolved and carried out by the water flow, leaving a negative-shaped cavity in the resin cured body 4 containing the sacrificial template, until the physical sacrificial template 2 is completely dissolved and carried out with the circulating deionized water.

[0036] Step Six: Transfer the component obtained in Step Five into an ultrasonic cleaner 5 and clean it three times with fresh deionized water at a frequency of 40 kHz for 10 minutes each time to thoroughly remove any residue in the pores. Place the cleaned component in a vacuum drying oven and dry it at 60°C for 12 hours until constant weight, to obtain a pure resin porous skeleton with precise three-dimensional interconnected pores; Step 7, prepare carbon fiber resin slurry 6: Weigh short-cut carbon fibers and add them to the two-component epoxy resin system (obtained in step 3, component A 31: component B 32 = 100:30). The amount of short-cut carbon fibers (fiber length varies from about 50 to 80 mm and fiber diameter varies from about 7 to 8 μm) added is 3% of the total mass. First, mechanically stir at a speed of 2000 rpm for 5 minutes, and then ultrasonically disperse for 30 minutes to obtain a uniform carbon fiber resin slurry 6.

[0037] Step 8: Place the pure resin porous skeleton in a dry silicone mold, evacuate to -0.09 MPa and maintain the vacuum. Under vacuum conditions, inject the carbon fiber resin slurry 6 prepared in Step 7 into the silicone mold, completely immersing the skeleton, and maintain the vacuum for 15 minutes to ensure that the carbon fiber resin slurry 6 fully penetrates all pores of the three-dimensional interconnected network structure of the pure resin porous skeleton.

[0038] Step nine: Transfer the mold back to the oven for final curing: cure at 80℃ for 2 hours, then at 120℃ for 3 hours. After curing, the resin in the slurry fuses and cross-links with the skeleton, and the chopped carbon fibers are fixed inside the pores, forming the final three-dimensional interpenetrating reinforced biomimetic porous carbon fiber composite material 7. Its flexural strength is 182.6±8.3MPa, flexural modulus is 4.12±0.21GPa, compressive strength is 128.4±6.7MPa, compressive elastic modulus is 3.85±0.18GPa, and impact strength is 28.6±1.9kJ / m². 2 The specific strength is 135.2 MPa / (g / cm). -3 The specific energy absorbed (SEA) is 46.1.

[0039] The above-described embodiments are merely illustrative of several feasible implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention, nor are the embodiments intended to limit the scope of protection in the claims of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention. All equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. A method for preparing biomimetic porous carbon fiber composite materials based on gradient infusion, characterized in that, The steps are as follows: Step 1, Bionic Modeling and Gradient Pore Design: Based on the three-dimensional interconnected network structure inside the sea urchin spines, a cylindrical digital model is constructed using three-dimensional modeling software; the overall porosity of the cylindrical digital model is 65% to 80%, the internal pore diameter is 50 to 150 μm, and the pore diameter decreases continuously from the center to the surface. Step 2, Preparation of digital physical sacrificial template: Using water-soluble photosensitive resin as raw material, a physical sacrificial template with the same geometry as the cylindrical digital model is printed using a 3D printer; Step 3, Vacuum Infusion and Matrix Curing: After vacuum degassing, the two-component epoxy resin system is infused into a mold containing a physical sacrificial template under a vacuum of -0.09 to -0.1 MPa, so that the resin fully wets the microporous structure of the template; then it is cured in stages at 40 to 65°C to obtain a resin cured body containing a physical sacrificial template. Step 4, selective dissolution of the template to create pores: The resin cured body containing the physical sacrificial template obtained in Step 3 is immersed in a constant temperature circulating deionized water bath at 45-55℃. By utilizing the solubility properties of the water-soluble photosensitive resin, the sacrificial template is completely dissolved and carried out with the circulating water flow, forming a precise negative three-dimensional interconnected pore in the resin body. Step 5, Cleaning: Using deionized water as the cleaning medium, the component obtained in Step 4 is cleaned to thoroughly remove the residual template dissolution products in the pores; then vacuum dried to constant weight to obtain a pure resin porous skeleton with precise three-dimensional connectivity and controllable pore size gradient. Step 6, Secondary Vacuum Infusion and Matrix Curing: Place the pure resin porous skeleton in a silicone mold, evacuate to -0.08 to -0.095 MPa, and perform secondary vacuum infusion of homologous epoxy resin slurry containing short-cut carbon fibers until the skeleton is completely submerged. Maintain pressure to ensure full penetration. Then, perform step curing again to uniformly anchor the short-cut carbon fibers in the pores and chemically co-crosslink them with the skeleton resin to obtain an integrated biomimetic porous carbon fiber composite material.

2. The method according to claim 1, characterized in that: In step one, the diameter of the pore at the center of the cylindrical digital model is 120-150 μm, and the diameter of the pore on the surface is 50-80 μm.

3. The method for preparing a biomimetic porous carbon fiber composite material based on gradient infusion according to claim 1, characterized in that: In step one, the porosity of the cylindrical digital model is 70% to 78%.

4. The method for preparing a biomimetic porous carbon fiber composite material based on gradient infusion according to claim 1, characterized in that: In step three, the two-component epoxy resin system is composed of epoxy resin and modified amine curing agent in a mass ratio of 100:20 to 40; after vacuum degassing, the viscosity of the mixed resin at 25°C is 200 to 500 mPa·s.

5. The method for preparing a biomimetic porous carbon fiber composite material based on gradient infusion according to claim 1, characterized in that: In step three, the stepped curing adopts a two-stage heating process. The first stage is a constant temperature curing at 40-45℃ for 3-4 hours, and the second stage is a constant temperature curing at 50-65℃ for 2-3 hours.

6. The method for preparing a biomimetic porous carbon fiber composite material based on gradient infusion according to claim 1, characterized in that: In step four, the temperature of the constant temperature circulating deionized water bath is 48–52°C, the soaking time is 20–28 h, and the water bath circulation flow rate is 1–3 L / min.

7. The method for preparing a biomimetic porous carbon fiber composite material based on gradient infusion according to claim 1, characterized in that: In step five, vacuum drying refers to drying in a vacuum drying oven at 55–65°C for 10–14 hours until constant weight.

8. The method for preparing a biomimetic porous carbon fiber composite material based on gradient infusion according to claim 1, characterized in that: In step six, the mass percentage of the short-cut carbon fiber in the homologous epoxy resin slurry containing short-cut carbon fibers is 1% to 5%, the fiber length is 50 to 80 μm, and the diameter is 7 to 8 μm; the homologous epoxy resin refers to the epoxy resin system with the same composition as the two-component epoxy resin system in step three.

9. The method for preparing a biomimetic porous carbon fiber composite material based on gradient infusion according to claim 1, characterized in that: In step six, the second-stage curing adopts a two-stage heating process: the first stage is to cure at a constant temperature of 80-95℃ for 2-3 hours, and the second stage is to heat up to 100-120℃ and cure at a constant temperature for 3-4 hours.

10. The method for preparing a biomimetic porous carbon fiber composite material based on gradient infusion according to claim 1, characterized in that: The overall porosity of the biomimetic porous carbon fiber composite material is 30% to 50%, the compressive strength is ≥120 MPa, and the flexural strength is ≥180 MPa.

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