阅读说明：本技术 一种修复改性碳纤维表界面的方法及其用途 (Method for repairing surface interface of modified carbon fiber and application thereof ) 是由 邹华维 邱宝伟 周生态 梁梅 于 2020-08-12 设计创作，主要内容包括：本发明提供了一种修复改性碳纤维表界面的方法及其用途,属于复合材料领域。具体提供了一种以浓度为0.01～0.5wt％的纤维素溶液作为上浆剂,对碳纤维进行上浆改性,制备得到的改性碳纤维。本发明利用纤维素对碳纤维进行改性,可以使得改性后的碳纤维拉伸强度显著提高；同时利用改性后的碳纤维制备的碳纤维增强树脂复合材料,其界面性能显著增强,力学强度显著提高。本发明改性方法具有不破坏碳纤维强度和工艺环保的优点,实现利用天然纤维素改善碳纤维及其与基体的界面性能。本发明改性碳纤维增强树脂复合材料可应用于航空航天、车辆工程、运动器械等领域制件的制备,具有广泛的应用前景。(The invention provides a method for repairing a surface interface of a modified carbon fiber and application thereof, belonging to the field of composite materials. Specifically, a modified carbon fiber is prepared by taking a cellulose solution with the concentration of 0.01-0.5 wt% as a sizing agent and carrying out sizing modification on the carbon fiber. According to the invention, the carbon fiber is modified by using the cellulose, so that the tensile strength of the modified carbon fiber is obviously improved; meanwhile, the carbon fiber reinforced resin composite material prepared by using the modified carbon fibers has the advantages of obviously enhanced interface performance and obviously improved mechanical strength. The modification method has the advantages of not damaging the strength of the carbon fiber and being environment-friendly in process, and the natural cellulose is utilized to improve the carbon fiber and the interface performance of the carbon fiber and a matrix. The modified carbon fiber reinforced resin composite material can be applied to the preparation of workpieces in the fields of aerospace, vehicle engineering, sports equipment and the like, and has wide application prospect.)

1. A modified carbon fiber for repair, which is characterized in that: the modified carbon fiber is prepared by taking a cellulose solution with the concentration of 0.01-0.5 wt% as a sizing agent and carrying out sizing modification on the carbon fiber.

2. The repair modified carbon fiber according to claim 1, characterized in that: the sizing method comprises coating, dipping, soaking or spraying;

alternatively, the sizing method comprises intermittent sizing or continuous sizing.

3. The repair modified carbon fiber according to claim 1, characterized in that: the diameter of the carbon fiber is 6.5-7.5 μm;

preferably, the carbon fiber is polyacrylonitrile carbon fiber, viscose-based carbon fiber or pitch-based carbon fiber;

more preferably, the carbon fibers are polyacrylonitrile carbon fibers;

further preferably, the carbon fiber is polyacrylonitrile carbon fiber containing no sizing agent.

4. The repair modified carbon fiber according to claim 1, characterized in that: the concentration of the cellulose solution is 0.02-0.1 wt%;

preferably, the concentration of the cellulose solution is 0.025-0.075 wt%;

more preferably, the concentration of the cellulose solution is 0.050 to 0.075 wt%;

more preferably, the concentration of the cellulose solution is 0.075 wt%;

further preferably, the cellulose solution is a cellulose aqueous solution;

still more preferably, the cellulose solution is prepared by the following method: adding cellulose into deionized water, and uniformly dispersing to obtain the cellulose-containing material;

still more preferably, the cellulose solution is prepared by the following method: and adding the cellulose into deionized water, stirring for 2-4 hours, and uniformly dispersing.

5. The repair modified carbon fiber according to claim 1, characterized in that: the cellulose is selected from any one or more of polymeric cellulose, carboxymethyl cellulose, cellulose ether, methyl cellulose and hydroxypropyl methyl cellulose;

preferably, the cellulose is selected from carboxymethyl cellulose;

more preferably, the carboxymethyl cellulose has a viscosity of 50 to 100MPa · s.

6. A method for preparing a repair modified carbon fiber according to any one of claims 1 to 5, characterized in that: it comprises the following steps:

the carbon fiber sizing agent is prepared by taking a cellulose solution as a sizing agent and carrying out sizing modification on carbon fibers;

preferably, the sizing method comprises coating, dipping, soaking or spraying;

and/or the sizing method comprises intermittent sizing or continuous sizing;

more preferably, the soaking and sizing time is 10-30 minutes;

further preferably, the soaking and sizing are followed by drying;

more preferably, the drying is carried out at 40-60 ℃ for 24-48 h.

7. Use of the repair modified carbon fiber of any one of claims 1 to 5 in the preparation of a carbon fiber reinforced polymer composite;

preferably, the carbon fiber reinforced polymer composite material is a carbon fiber reinforced resin composite material;

more preferably, the resin is selected from thermosetting resins or thermoplastic resins;

further preferably, the thermosetting resin is selected from epoxy resin, phenol resin, urea resin, bismaleimide resin, polyimide resin, silicone or polyurethane; and/or, the thermoplastic resin is selected from polyethylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polypropylene or nylon;

still more preferably, the resin is a bisphenol a type epoxy resin.

8. A repair modified carbon fiber reinforced polymer composite material is characterized in that: the repair modified carbon fiber is obtained by coating a resin mixture on the repair modified carbon fiber according to any one of claims 1 to 5 and then curing and molding the resin mixture; the resin mixture consists of resin and a curing agent, and the mass ratio of the resin to the curing agent is 100: (10-30);

preferably, the resin is selected from thermosetting resins or thermoplastic resins;

and/or the curing agent is Moca curing agent;

and/or the mass ratio of the resin to the curing agent is 100: (24-28);

more preferably, the thermosetting resin is selected from epoxy, phenolic, urea-formaldehyde, bismaleimide, polyimide, silicone or polyurethane;

and/or, the thermoplastic resin is selected from polyethylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polypropylene or nylon;

further preferably, the resin is a bisphenol a type epoxy resin;

and/or the curing agent is 4,4' -diaminodiphenylmethane;

and/or the mass ratio of the resin to the curing agent is 100: 26.

9. a method of preparing the carbon fiber reinforced polymer composite material of claim 8, wherein: it comprises the following steps:

(1) mixing and stirring the resin and the curing agent uniformly to obtain a resin mixture;

(2) coating the resin mixture on the repair modified carbon fiber according to any one of claims 1 to 5, and curing and molding to obtain the repair modified carbon fiber.

10. Use of the carbon fiber reinforced polymer composite material according to claim 8 for the preparation of articles in the field of aerospace, vehicle engineering, sports machinery.

Technical Field

The invention belongs to the field of composite materials, and particularly relates to a method for repairing a surface interface of a modified carbon fiber and application thereof.

Background

Carbon fiber reinforced polymer Composites (CFRPs) have excellent mechanical properties and weight ratio, are high-grade composites, and are widely applied to the mechanical engineering aerospace and automobile industries. Generally, the interface between Carbon Fibers (CFs) and the resin is critical to the mechanical properties of the CFRP, as loads are transferred from the resin to the carbon fibers, thereby reducing stress concentrations at the interface. Better interfacial properties can generally provide better mechanical properties to the composite. However, the number of polar groups on the untreated CF surface is small, resulting in weak interfacial interactions with the resin matrix. In addition, carbon fiber is a rigid material, and when CFRPs are subjected to stress, it is easy to cause stress concentration at the interface due to the presence of surface defects, resulting in degradation of material properties. These problems limit further improvements in CFRPs performance and have become a key issue in the development of CFRPs that has been expected to be solved, but not solved. Therefore, it is very important to modify CFRPs to obtain an excellent interface and further improve the mechanical properties of CFRPs.

The interfacial properties are related to the chemical composition and morphology of the surfaces of the CFs. Carbon fibers inevitably cause a large number of defects with multifunctional groups during production, which can produce crack-tip effects and stress concentrations at the interface. Many researchers have focused on the modification of the inert surfaces of CFs to achieve better CFs/resin interface properties by introducing more chemical reaction sites and increasing the specific surface area for adhesion, such as sizing, grafting, chemical vapor deposition, electrochemical methods, plasma treatment, and the like. However, aggressive (chemical) treatments may damage the surface of the CFs, resulting in larger defects, thereby reducing their mechanical properties. Electrochemical and plasma treatment are limited by equipment and are difficult to popularize, and chemical vapor deposition grafting and other processes are complex and difficult to industrially popularize.

Researchers adopt hydroxypropyl methyl cellulose as a dispersing agent to modify carbon fibers so as to improve the dispersibility of the carbon fibers and further improve the mechanical property of the epoxy composite material, and particularly, the epoxy composite material is obtained by uniformly mixing unmodified carbon fibers, the dispersing agent, a curing agent and resin, then carrying out vacuum degassing and then curing. However, in this method, hydroxypropyl methylcellulose only adsorbs the surface of carbon fibers, and does not emulsify the surface of carbon fibers, and thus the interfacial properties between carbon fibers and epoxy resin cannot be effectively improved. Meanwhile, the dispersion mechanism of the hydroxypropyl methyl cellulose is physical dispersion, the carbon fibers are dispersed by utilizing adsorption of macromolecules and winding and blocking effects of molecular chains, the internal defects of the carbon fibers filled with micromolecular slurry are avoided, and observation through an electron microscope shows that the hydroxypropyl methyl cellulose cannot be effectively and uniformly attached to the carbon fibers to easily form stress concentration points and cause unstable mechanical properties of the composite material. The enhancement effect of using hydroxypropylmethylcellulose as a dispersant for enhancing the mechanical properties of epoxy groups is very limited.

In order to make the carbon fiber reinforced polymer composite material be better applied to various industries, the performance of the carbon fiber reinforced polymer composite material needs to be further improved, and particularly the mechanical property and the stability need to be further improved.

Disclosure of Invention

The invention aims to provide a method for repairing a modified carbon fiber surface interface and application thereof.

The invention provides a repair modified carbon fiber, which is prepared by taking a cellulose solution with the concentration of 0.01-0.5 wt% as a sizing agent and carrying out sizing modification on the carbon fiber.

Further, the sizing method comprises coating, dipping, soaking or spraying;

alternatively, the sizing method comprises intermittent sizing or continuous sizing.

Further, the diameter of the carbon fiber is 6.5-7.5 μm;

preferably, the carbon fiber is polyacrylonitrile carbon fiber, viscose-based carbon fiber or pitch-based carbon fiber;

more preferably, the carbon fibers are polyacrylonitrile carbon fibers;

further preferably, the carbon fiber is polyacrylonitrile carbon fiber containing no sizing agent.

Further, the concentration of the cellulose solution is 0.02-0.1 wt%;

preferably, the concentration of the cellulose solution is 0.025-0.075 wt%;

more preferably, the concentration of the cellulose solution is 0.050 to 0.075 wt%;

more preferably, the concentration of the cellulose solution is 0.075 wt%;

further preferably, the cellulose solution is a cellulose aqueous solution;

still more preferably, the cellulose solution is prepared by the following method: adding cellulose into deionized water, and uniformly dispersing to obtain the cellulose-containing material;

still more preferably, the cellulose solution is prepared by the following method: and adding the cellulose into deionized water, stirring for 2-4 hours, and uniformly dispersing.

Further, the cellulose is selected from any one or more of multi-polymer cellulose, carboxymethyl cellulose, cellulose ether, methyl cellulose and hydroxypropyl methyl cellulose;

preferably, the cellulose is selected from carboxymethyl cellulose;

more preferably, the carboxymethyl cellulose has a viscosity of 50 to 100MPa · s.

The invention also provides a preparation method of the repaired and modified carbon fiber, which comprises the following steps:

the carbon fiber sizing agent is prepared by taking a cellulose solution as a sizing agent and carrying out sizing modification on carbon fibers;

preferably, the sizing method comprises coating, dipping, soaking or spraying;

and/or the sizing method comprises intermittent sizing or continuous sizing;

more preferably, the soaking and sizing time is 10-30 minutes;

further preferably, the soaking and sizing are followed by drying;

more preferably, the drying is carried out at 40-60 ℃ for 24-48 h.

The invention also provides the application of the repaired and modified carbon fiber in preparing the carbon fiber reinforced polymer composite material;

preferably, the carbon fiber reinforced polymer composite material is a carbon fiber reinforced resin composite material;

more preferably, the resin is selected from thermosetting resins or thermoplastic resins;

further preferably, the thermosetting resin is selected from epoxy resin, phenol resin, urea resin, bismaleimide resin, polyimide resin, silicone or polyurethane; and/or, the thermoplastic resin is selected from polyethylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polypropylene or nylon;

still more preferably, the resin is a bisphenol a type epoxy resin.

The invention also provides a repair modified carbon fiber reinforced polymer composite material, which is obtained by coating the resin mixture on the repair modified carbon fiber and then curing and molding; the resin mixture consists of resin and a curing agent, and the mass ratio of the resin to the curing agent is 100: (10-30);

preferably, the resin is selected from thermosetting resins or thermoplastic resins;

and/or the curing agent is Moca curing agent;

and/or the mass ratio of the resin to the curing agent is 100: (24-28);

more preferably, the thermosetting resin is selected from epoxy, phenolic, urea-formaldehyde, bismaleimide, polyimide, silicone or polyurethane;

and/or, the thermoplastic resin is selected from polyethylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polypropylene or nylon;

further preferably, the resin is a bisphenol a type epoxy resin;

and/or the curing agent is 4,4' -diaminodiphenylmethane;

and/or the mass ratio of the resin to the curing agent is 100: 26.

the invention also provides a preparation method of the carbon fiber reinforced polymer composite material, which comprises the following steps:

(1) mixing and stirring the resin and the curing agent uniformly to obtain a resin mixture;

(2) and coating a resin mixture on the repair modified carbon fiber, and curing and forming to obtain the repair modified carbon fiber.

The invention also provides application of the carbon fiber reinforced polymer composite material in preparing workpieces in the fields of aerospace, vehicle engineering and sports equipment.

In the invention, the repair modification means that carboxymethyl cellulose in the modified carbon fiber spontaneously reaches the position of a carbon fiber surface defect through a polar functional group, so that stress concentration is reduced, the strength of the carbon fiber is improved, and the repair modification of the carbon fiber is realized.

According to the invention, the carbon fiber is modified by using the cellulose, so that the tensile strength of the modified carbon fiber is obviously improved; meanwhile, the carbon fiber reinforced resin composite material prepared by using the modified carbon fibers has the advantages of obviously enhanced interface performance and obviously improved mechanical strength. The modification method has the advantages of not damaging the strength of the carbon fiber and being environment-friendly in process, and the natural cellulose is utilized to improve the carbon fiber and the interface performance of the carbon fiber and a matrix. The modified carbon fiber reinforced resin composite material can be applied to the preparation of workpieces in the fields of aerospace, vehicle engineering, sports equipment and the like, and has wide application prospect.

Obviously, many modifications, substitutions, and variations are possible in light of the above teachings of the invention, without departing from the basic technical spirit of the invention, as defined by the following claims.

The present invention will be described in further detail with reference to the following examples. This should not be understood as limiting the scope of the above-described subject matter of the present invention to the following examples. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention.

Drawings

Fig. 1 is a schematic view of a preparation of a modified carbon fiber and a schematic view of a composite material structure: a is a preparation schematic diagram of modified carbon fiber; b is a schematic structural diagram of the composite material.

FIG. 2 shows a process for preparing a composite material.

Fig. 3 is an infrared spectrum of carboxymethyl cellulose, unmodified Carbon Fiber (CF), and modified carbon fiber.

Fig. 4 is a raman spectrum and curve fit of all samples: (a) the Raman spectrum full spectrogram of each sample is obtained; (b) curve fitting for unmodified Carbon Fiber (CF); (c) curve fitting for CF/0.025g CMC; (d) curve fitting for CF/0.050 gCMC; (e) curve fitting for CF/0.075 gCMC; (f) is a curve fit of CF/0.100g CMC.

Fig. 5 is an SEM picture of unmodified carbon fiber and modified carbon fiber: (a) a dimension chart of each carbon fiber; (b) SEM image of the unmodified carbon fiber surface; (c) SEM image of CF/0.025g CMC surface; (d) SEM image of CF/0.050g CMC surface; (e) SEM image of CF/0.075g CMC surface; (f) SEM image of CF/0.100g CMC surface.

Fig. 6 is an AFM picture of unmodified carbon fiber and modified carbon fiber: (a) AFM images of unmodified carbon fiber surfaces; (b) AFM plot for CF/0.025g CMC surface; (c) AFM images of CF/0.050gCMC surfaces; (d) AFM plot of CF/0.075g CMC surface; (e) AFM plot of CF/0.100g CMC surface; (f) and (4) obtaining a statistical diagram of the height and the peak number of the surface topography of each carbon fiber.

Fig. 7 is a linear fit plot of monofilament tensile strength and WEIBULL for unmodified carbon fiber and modified carbon fiber: (a) a linear fitting graph of the unmodified carbon fiber; (b) is a linear fit plot of CF/0.025g CMC; (c) is a linear fit plot of CF/0.050 gCMC; (d) is a linear fit plot of CF/0.075g CMC; (e) is a linear fit plot of CF/0.100g CMC; (f) the tensile strength of each carbon fiber filament.

Fig. 8 is a microscope image of unmodified and modified carbon fibers: (a) is unmodified carbon fiber; (b) CF/0.025g CMC; (c) CF/0.050g CMC; (d) CF/0.075g CMC; (e) is CF/0.100g CMC.

Fig. 9 is a contact angle of unmodified carbon fiber and modified carbon fiber: (a) is unmodified carbon fiber; (b) CF/0.025g CMC; (c) CF/0.050g CMC; (d) CF/0.075g CMC; (e) CF/0.100g CMC; (f) is a contact angle change graph.

Fig. 10 is an IFSS comparison of composites prepared from individual carbon fibers.

Fig. 11 is SEM pictures of the composite material in longitudinal section (parallel to the axis of the carbon fibers) and in cross section (perpendicular to the axis of the carbon fibers): (a) the carbon fiber is a longitudinal section of the composite material, and the added carbon fiber is unmodified carbon fiber; (b) the composite material is a longitudinal section of the composite material, and the added carbon fiber is CF/0.075g CMC; (c) the added carbon fiber is CF/0.100g CMC; (a') is the cross section of the composite material, and the added carbon fiber is unmodified carbon fiber; (b') is the cross section of the composite material, the added carbon fiber is CF/0.075g CMC; (c') is the cross section of the composite material, and the carbon fiber added is CF/0.100g CMC.

Fig. 12 is an SEM photograph and a carbon fiber distribution diagram of a cross section (direction perpendicular to the carbon fibers) of the composite material: (a) the carbon fiber added in the composite material is unmodified carbon fiber; (b) the carbon fiber added in the composite material is CF/0.075g CMC; (c) the carbon fiber added in the composite material is CF/0.100g CMC; (a') is a carbon fiber distribution diagram in the composite material, and the carbon fiber is unmodified carbon fiber; (b') is the carbon fiber distribution profile in the composite, the carbon fiber is CF/0.075g CMC; (c') is the carbon fiber distribution diagram in the composite material, the carbon fiber is CF/0.100g CMC; the length and width of each small rectangle in the carbon fiber profile were 15.9375 μm and 14.15 μm, respectively.

Detailed Description

The raw materials and equipment used in the embodiment of the present invention are known products and obtained by purchasing commercially available products. The main raw materials are as follows:

PAN-based carbon fiber (CF, average diameter 7 μm, density 1.78 g/cm) containing no sizing agent³Model number T300) was provided by hengxing industries limited (jiangsu province, china). Carboxymethyl cellulose (CMC, 50-100MPa · s, DS ═ 0.7) was purchased from alatin reagent industries, ltd (shanghai, china). The epoxy resin used was bisphenol A type epoxy resin (E51, epoxy value 0.49-0.54mol/100g) obtained from Decyclo epoxy technology industries, Inc. (Shandong, China). The curing agent is 4,4' -diaminodiphenylmethane (DDM) supplied by alatin reagent industries limited, shanghai, china. All reagents were used directly without purification.