KR20220103311A - Enhancement structure of the interfacial strength between carbon fiber and epoxy resin composites and manufacturing methode of the same - Google Patents

Abstract

The present invention relates to a structure for improving the interfacial strength between carbon fibers and an epoxy resin, comprising: carbon fibers; MXene surface-modified with organic silane bonded to the carbon fibers; and an epoxy resin combined with MXene. The present invention modifies the surface of MXene (Ti_2C), a novel 2D material, with 3-aminopropyl triethoxysilane, and then grafts the ame onto the surface of carbon fiber to effectively improve the interfacial properties such as IFSS and ILSS of carbon fibers.

Description

Structure for improving the interfacial strength between carbon fiber and epoxy resin and manufacturing method thereof

The present invention relates to a structure for improving the interfacial strength between carbon fibers and an epoxy resin, and a method for manufacturing the same, and more particularly, to a structure in which maxin whose surface is modified with organic silane is bonded to carbon fibers and then bonded to an epoxy resin. .

Carbon fiber (CF) is a material that has recently been attracting attention, and is a popular material for urban air mobility and/or personal flying vehicles that require light weight, design flexibility, corrosion resistance and excellent mechanical properties in the automobile industry as well as unmanned aerial vehicles and drones. . However, the realization of excellent interfacial strength between CF and polymer matrix is still under investigation. In general, it is known that the interfacial strength is quite weak due to the poor wettability and interaction by the surface of the chemically inert CF with hydrophobicity. Therefore, grafting is under development to improve the interfacial properties of CF.

In particular, nanomaterials such as carbon nanotubes, nanofibers, and graphene oxide (GO) are often used to size CF. Electrophoretic deposition, chemical vapor deposition, to enhance the properties of the interface to satisfy the high mechanical strength, wide interface, and stress transfer capability between the CF and the polymer matrix. And methods such as chemical grafting have been used.

MXene, which has a structure similar to graphene, is a newly developed material as a 2D nanosheet material synthesized on MAX. One of these two-dimensional materials, MXene, is a two-dimensional material obtained from MAX having a three-dimensional crystal structure consisting of an M layer, an A layer, and an X layer, where M is a transition metal and A is a group 13 or group 14 element. , X is carbon or nitrogen. Such MAX is a crystalline substance in which A, which is a metal element different from MX or M of ceramic characteristics, is combined, and has excellent physical properties such as electrical conductivity, oxidation resistance and machinability. Theoretically, thousands or hundreds of types may exist, but it is known that about 300 types of MAX have been synthesized so far. For example, M ₂ X Maxine has better mechanical properties than M ₃ X ₂ and M ₄ X. Moreover, similar to other carbon-based 2D nanosheet materials, Maxine has a high specific surface area (603 m ² /g for Ti ₂ C), a hydrophilic surface, and superior mechanical strength (~0.2 TPa) than that of GO (~ 0.2 TPa) for Ti ₂ C. 0.33±0.07 TPa) can be provided. In addition, the effective flexural strength of Ti ₂ C (D = 5.21 eV) is greater than that of graphene (D = 2.3 eV) because the monolayer thickness of maxine is three times thicker than that of graphene. Therefore, it is expected that Maxine will be newly used as a CF compound in various ways.

One object of the present invention is to provide a structure for strengthening the interfacial bond between carbon fibers and an epoxy resin by bonding the maxine surface-modified with an organosilane with the carbon fiber and then bonding the maxine with an epoxy resin.

The structure for improving the interfacial strength between the carbon fiber and the epoxy resin for one purpose of the present invention includes a carbon fiber, a maxine surface-modified with an organosilane coupled to the carbon fiber (Mxene), and an epoxy resin coupled to the maxine do.

In one embodiment, the organosilane is preferably 3-aminopropyl triethoxysilane (APTES).

In one embodiment, the increase rate of interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the carbon fiber combined with the modified maxine is not sized (unsized) carbon fiber (Carbon Fiber) ; CF) by 75 to 80% and 25 to 30%, respectively, and preferably by 78% and 28%, respectively.

A manufacturing method for improving the interfacial strength of carbon fibers for one purpose of the present invention comprises the steps of mixing an organic silane and maxine to prepare a maxine solution whose surface is modified with organic silane, and maxine surface-modified with the organic silane A surface modification reaction step of mixing the solution and carbon fibers is included.

In one embodiment, the organosilane preferably comprises 3-aminopropyl triethoxysilane.

In one embodiment, the surface modification reaction step mixes a mixed solution of carbon fiber and modified maxine 2 to 8 mg, HATU 3 to 7 mg, and DMF 28 to 32 ml, preferably the modified maxine is 6 mg , 5 mg of HATU, and 30 ml of DMF.

In one embodiment, the surface modification reaction step is reacted at 85 ~ 95 ℃ for 3 to 5 hours, preferably at 90 ℃ for 4 hours.

A method of manufacturing a structure for improving the interfacial strength between carbon fibers and an epoxy resin for one purpose of the present invention comprises the steps of mixing an organic silane and a maxine to prepare a maxine solution whose surface is modified with organic silane, the surface with the organic silane It includes; mixing the modified maxine solution and carbon fiber, and combining the maxine and carbon fiber mixture with an epoxy resin.

In one embodiment, the organosilane preferably comprises 3-aminopropyl triethoxysilane.

In one embodiment, the surface modification reaction step mixes a mixed solution of carbon fiber and modified maxine 2 to 8 mg, HATU 3 to 7 mg, and DMF 28 to 32 ml, preferably the modified maxine is 6 mg , 5 mg of HATU, and 30 ml of DMF.

In one embodiment, the surface modification reaction step is reacted at 85 ~ 95 ℃ for 3 to 5 hours, preferably at 90 ℃ for 4 hours.

The structure for improving the interfacial strength between the carbon fiber and the epoxy resin for one purpose of the present invention is preferably formed by the above-described manufacturing method.

In one embodiment, the increase rate of interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the carbon fiber combined with the modified maxine is not sized (unsized) carbon fiber (Carbon Fiber) ; CF) by 75 to 80% and 25 to 30%, respectively, and preferably by 78% and 28%, respectively.

The present invention modifies the surface of maxine (Ti ₂ C), a novel 2D material, with 3-aminopropyl triethoxysilane, and grafts it on the surface of carbon fibers, such as IFSS and ILSS of carbon fibers. can be effectively improved.

In addition, bonding of the carbon fiber grafted with the modified maxine to the epoxy resin provides increased bonding strength, which can provide lightweight rigid bonding strength in places requiring high reliability, such as aircraft, ships, and vehicles. have.

1 is an image (a) showing the modified Ti ₂ C of the present invention and an image (b) showing the CF surface grafted with NH ₂ -Ti ₂ C.
2 is a wide scan XPS spectrum graph of the present invention (a), Ti ₂ C O1s high-resolution XPS spectrum graph (b), NH ₂ -Ti ₂ C O1s high-resolution XPS spectrum graph (c), C1s of unsized CF High-resolution XPS spectrum graph (d), C1s high-resolution XPS spectrum graph of ACF (d), C1s high-resolution XPS spectrum graph of NH ₂ -Ti ₂ C-CF (f), N1s high-resolution XPS spectrum graph of NH ₂ -Ti ₂ C ( f).
3 is a high-resolution image of the CF structure of the present invention (a), a high-resolution image of a non-sized CF structure (b), a high-resolution image of an ACF structure (c), a high-resolution image of NH ₂ -Ti ₂ C-CF structure ( d) and contact angle graphs of various carbon fibers (f), and surface energy graphs of various carbon fibers (g).
4 is a birefringence pattern image (a) of a single fiber fragment experiment of a non-sized CF compound (a), a birefringence pattern image of a single fiber fragment experiment of an NH ₂ -Ti ₂ C-CF compound (b) and a non-sized CF A cross-sectional structure image of the compound (c), and a cross-sectional structure image of the NH ₂ -Ti ₂ C-CF compound (d).
Figure 5 is a non-sized peak frequency (peak frequency) graph according to the strain (strain) of the CF compound (a), NH ₂ -Ti ₂ C-CF compound according to the deformation of the peak frequency graph (b) and the non-sized CF A graph (c) showing the signal accumulation in different cases according to the modification of the compound, and a graph (d) showing the signal accumulation in other cases according to the modification of the NH ₂ -Ti ₂ C-CF compound.
6 is an image showing three failures (fiber breakage, bond failure, matrix breakage) of the unsized CF compound (a), and an image showing three failures of the NH ₂ -Ti ₂ C-CF compound (b) and an image (c) showing the chemical reaction of NH ₂ -Ti ₂ C-CF between ACF and epoxy.

The terms used in the present application are used only to describe specific embodiments and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, step, operation, component, part, or combination thereof described in the specification is present, and includes one or more other features or steps. , it should be understood that it does not preclude the possibility of the existence or addition of , operation, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

The structure for improving the interfacial strength between the carbon fiber and the epoxy resin according to the present invention includes a carbon fiber (CF), a maxine surface-modified with an organosilane bonded to the carbon fiber (MXene), and an epoxy resin bonded to the maxine do.

The organosilane is 3-aminopropyl triethoxysilane (APTES), γ-aminopropyl triethoxysilane (γ-Aminopropyl triethoxysilane), and N- [3- (diethoxymethylsilyl) propyl] It may include one of ethylenediamine (N-[3-(diethoxymethylsilyl)propyl]ethylenediamine).

In this case, maxine is an interphase material between CF and an epoxy resin, and Ti ₂ C is preferable among maxine. The modified maxine is bonded to the surface of the CF through chemical grafting, whereby the adhesion between the CF and the epoxy matrix can be significantly improved.

Specifically, FIG. 1 shows the chemical structure of maxine surface-modified with APTES (NH ₂ -Ti ₂ C) and CF (NH ₂ -Ti ₂ C-CF) combined with the modified maxine.

Here, the increase rate of the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the carbon fiber combined with the modified maxine is not sized (unsized) carbon fiber (Carbon Fiber; CF) compared to 75 to 80% and 25 to 30%, respectively, preferably IFSS by 78% and ILSS by 28%.

On the other hand, the manufacturing method for improving the interfacial strength of carbon fibers of the present invention comprises the steps of mixing an organosilane and maxine to prepare a maxine solution whose surface is modified with organosilane, and a maxine solution whose surface is modified with the organosilane and It includes a surface modification reaction step of mixing carbon fibers.

First, the maxine was prepared by synthesizing a Ti ₂ C sheet from Ti ₂ AlC.

In this case, the organic silane may include 3-aminopropyl triethoxysilane (APTES). By utilizing APTES on the prepared Ti ₂ C sheet, modified NH ₂ -Ti ₂ C is formed, and the modified NH ₂ -Ti ₂ C is used as a sizing agent.

Next, a commercially available CF sizing agent is removed to form unsized CF (unsized CF), followed by oxidation treatment. At this time, the produced carbon fiber is referred to as ACF. ACF is synthesized NH ₂ -Ti ₂ C-CF by the surface modification reaction proceeds in the solution containing NH ₂ -Ti ₂ C prepared above. In this process, the reaction between the carboxyl group of ACF and the amino group of NH ₂ -Ti ₂ C proceeds using HATU as a condensing agent. Thereby, NH ₂ -Ti ₂ C is uniformly grafted onto the surface of CF by a covalent bond (-C=O-NH-), and not only increases the CF surface roughness but also increases the surface energy of CF, resulting in a large number of polar functional groups is formed

The mixed solution in the surface modification reaction step is a mixture of 2 to 8 mg of modified maxin, 3 to 7 mg of HATU, and 28 to 32 ml of DMF, preferably the modified maxin is 6 mg, HATU 5 mg, and DMF 30 ml to prepare a mixed solution.

In addition, in the surface modification reaction step, the reaction is performed at 85 to 95° C. for 3 to 5 hours, preferably at 90° C. for 4 hours.

On the other hand, the method of manufacturing a structure for improving the interfacial strength between carbon fibers and an epoxy resin comprises the steps of mixing an organic silane and maxine to prepare a maxine solution whose surface is modified with organic silane, a maxine solution having a surface modified with the organic silane and mixing the carbon fiber, and combining the maxine and the carbon fiber mixture with the epoxy resin.

The NH ₂ -Ti ₂ C-CF synthesized by the manufacturing method for improving the interfacial strength of the carbon fibers described above and the epoxy resin are combined. Thereby, a structure with improved interfacial strength between carbon fibers and epoxy is manufactured.

At this time, the case where the bond at the interface is broken by the NH ₂ -Ti ₂ C-CF mixture is reduced, which affects more micro-golds in the matrix. This means that stronger adhesion and better load carrying capacity are formed between the fibers and the matrix.

As a result, the interfacial strength of compound-reinforced CF was significantly increased, and the excellent mechanical properties of CF were effectively and efficiently controlled for application in various compound structures.

Hereinafter, a structure for improving the interfacial strength between the carbon fiber and the epoxy resin of the present invention and a manufacturing method thereof will be described in more detail through specific examples.

Example: Materials used

Unidirectional carbon fibers (Carbon Multifilament Continuous Tow: 12K, tensile strength: 696-725 KSI) were purchased from Fiber Glast Developments Corporation, USA (see Table 1).

CF Types Critical Length l _c (μm) Gauge Length l ₀
(mm) Fiber Strength σ _f,l0 (GPa) W.
shape
β Diameter
d
(μm) Fiber
Critical
Strength σ _f,lc (GPa) IFSS
τ
(MPa) ILSS
(MPa) Sized CF 587.7 5.134±0.11 4.86±0.45 4.01 5.93±0.03 8.3441 42.38±2.5 36.01±1.8 Unsized CF 592.6 5.128±0.20 4.77±0.51 3.66 5.59±0.09 8.6016 40.57±1.8 34.63±2.0 ACF 539.5 5.198±0.15 4.53±0.34 3.28 5.58±0.08 9.0375 46.73±3.0 38.92±2.1 NH ₂ -Ti ₂ C-CF 386.5 5.213±0.13 4.59±0.55 3.30 5.97±0.71 9.3445 72.17±1.0 44.24±1.1

Ti ₂ AlC (≤400 mesh, 99.5 %) was purchased from Famouschem Technology (Shanghai) Co., Ltd, and epoxy resin (YD-128) was purchased from KUKOO chemical Co., Ltd. In addition, other diethylenetriamine, nitric acid, 3-aminopropyl triethoxysilane (APTES), sulfuric acid, hydrofluoric acid, HATU ( 2-(7-Azabenzotriazol-1-yl) -N,N,N',N'-tetramethyluronium hexafluorophosphate), acetone, dimethyl sulfoxide, and DMF (N,N-dimethylformamide) are Sigma - Purchased from Aldrich.

Example: CF surface grafting process

First, a Ti ₂ C sheet synthesized from Ti ₂ AlC was reacted with 3-aminopropyl triethoxysilane to form NH ₂ -Ti ₂ C, and the chemical reaction is shown in FIG. 1A .

Thereafter, the purchased CF (sized CF) was refluxed in acetone solution at 70° C. for 48 hours to remove the sizing agent, which is called 'unsized CF'.

The unsized CF was oxidized in a mixed solution of HNO ₃ and H ₂ SO ₄ (1:3) at 80° C. for 4 hours to form an acid carbon fiber (ACF), a carbon fiber.

Then, ACF was dispersed in a well-mixed solution of NH ₂ -Ti ₂ C 6 mg, HATU 5 mg, and DMF 30 ml, and then mixed at 90 ° C. for 4 hours to proceed with a chemical reaction for the grafting process, NH ₂ -Ti ₂ C-CF was synthesized. The chemical reaction for the overall grafting process is, as shown in FIG. 1b, the reaction between the carboxyl group of ACF and the amino group of NH ₂ -Ti ₂ C-CF is carried out using HATU as a condensing agent.

Experimental Example 1: IFSS and ILSS experiments

For IFSS testing, single-fiber piece specimens are prepared according to ASTM D638. ILSS analysis was measured using a short beam strength test. Compound monolayer samples were prepared by hand layup method, and each experiment was repeated 10 times.

Experimental Example 2: Characteristic Analysis Experiment

To analyze the chemical elements grafted on the CF surface, X-ray photoelectron spectroscopy (XPS; K-Alpha, Thermo Fisher Scientific Inc., USA) was used. The surface structure of CF and failure at the interface were measured using a scanning electron microscope (SEM; JSM-7500F, JEOL, USA). The dynamic contact angle between CF and the experimental solution was measured using a dynamic contact angle meter (DCAT21, Data Physics Instruments, Germany), where deionized water ( γ ^d = 21.8 mJ/m ² , γ = 72.8 mJ/m ² ) and iodide Methylene (diiodomethane, γ ^d = 50.8 mJ/m ² , γ = 50.8 mJ/m ² , purity 99%, Alfa Aesar, USA) was used as an experimental solution. The dispersion degree and polarity of the elements were calculated using Equation 1 below.

Formula 1

The γ ₁ represents the surface tension, γ _l ^p represents the polar component, and γ _l ^d represents the degree of dispersion.

The single fiber tensile test was measured using an Instron 3343 universal testing machine, and a total of 50 samples were tested. Fiber fragments were observed using a metallographic microscope (OLYMPUS BX51, Guangzhou).

For single-fiber piece testing, the specimen was loaded onto a uniaxial tensile load using an Instron E3000 Universal testing machine, followed by a crosshead speed of 2 mm/min. measured.

IFSS was calculated through the following Equation 2 Kelly-Tyson equation (Kelly-Tyson equation).

Formula 2

)에서 결정하였다(수식 3 참조).where d is the fiber diameter, and σ _f at critical fragmentation length ( l _c ) is the fiber durability, which is the average fiber fragment length at saturation (

) was determined (see Equation 3).

Formula 3

Since direct measurement of fiber strength at the critical piece length is very difficult at present, σ _f is mainly calculated through an empirical formula using a single fiber tensile strength test (see Equation 4).

Formula 4

Where l ₀ is the length of the initial single carbon fiber, σ ₀ is the fiber tensile stress, and β is a Weibull shape parameter obtained by linear fitting.

During single fiber fragmentation experiments, acoustic emission (AE) experiments were run concurrently to evaluate the cleavage process between CF and epoxy resin. The AE signal is measured using a wideband AE sensor (Physical Acoustic Corp.,; PAC).

A beam shear test is used to determine the ILSS properties of unidirectional CF blend laminates according to ASTM D2344. The size of the measured sample is 12.48 mm × 4.16 mm × 2.08 mm. The above properties were measured in a universal testing machine (DTU-M series, Dae Kyung Tech, KR) at a crosshead speed of 1 mm/min. ILSS was calculated using Equation 5 below.

Formula 5

Where P is the maximum value obtained during the experiment, and b and h are the width and thickness of the specimen, respectively.

Experimental Example Result 1: Chemical compound and CF surface structure

The surface of Ti ₂ C before/after APTES modification was measured using XPS. Referring to FIG. 2b, the peak of O1s of Ti ₂ C is shown by two peaks of Ti-O (530.4 eV) and CO (532.3 eV). Figure 2c is measured after additional APTES treatment, it can be confirmed that a new Si-O-Ti (533.3 eV) peak was detected in the O1s spectrum of NH ₂ -Ti ₂ C. Here, the Si-O-Ti bond means that Ti ₂ C and the grafting APTES successfully covalently bond.

Referring to Figure 2a, the surface of the unsized CF is mainly composed of carbon and oxygen (C = 87.93%, O = 12.07%), CC (284.7 eV), CO (285.4 eV), and C = O (289.9) eV) binding. After acid treatment, the concentration of carbon was moderately reduced, but the oxygen increased significantly up to 19.81%. Perhaps this is due to the formation of -COOH groups in CF. Newly formed elements such as F, Ti, and Si appeared, and after grafting NH ₂ -Ti ₂ C onto CF, the peak related to the content of N increased, which indicates that NH ₂ -Ti ₂ C was means to exist. Moreover, referring to the peak of C1s in FIG. 2f, a new peak at 287.9 eV could be identified, which means a newly created -NC=O bond. The bond appears to be formed by the carboxyl group of ACF and the amino group of NH ₂ -Ti ₂ C. In addition, the chemical bond also appears in the N1s spectrum of FIG. 2g, and the amide (-NC=O) peak can be confirmed at 400.1 eV. These results indicate that NH ₂ -Ti ₂ C and ACF are covalently bonded by chemical grafting.

After surface modification with NH ₂ -Ti ₂ C, the surface structure of CF was observed through SEM characteristics, which is shown in FIG. 3 . Referring to FIG. 3b , after removing the existing sizing, the surface of the CF became smooth, and it can be seen that the diameter was slightly reduced. However, referring to FIG. 3C , narrow and flat plate-shaped grooves were formed on the fiber surface after acid treatment, which appears to be due to oxidation treatment and etching. Referring to Figure 3d, e, compared with the smooth surface of the non-sized CF, after grafting with NH ₂ -Ti ₂ C Numerous NH ₂ -Ti ₂ C sheets can be confirmed on the surface of the newly sized CF. there was. Through SEM characteristics, covalently grafted and abundantly dispersed NH ₂ -Ti ₂ C sheets were identified along the length of the fiber surface. This is shown to provide efficient and effective interfacial property control between the CF and the matrix having a larger interfacial area, and also means providing a strong interfacial bond by mechanical interlocking between the CF and the matrix.

Experimental Example Result 2: Surface Energy of CF

The surface energy of each CF during the grafting process was investigated by measuring the contact angle in two types of liquids: deionized water and methylene iodide (see FIG. 3f ). Referring to FIG. 3G , the surface energy was 38.8 mJ/m ² in the unsized CF but increased to 33.9 mJ/m ² in the sized CF. After oxidation process with acid, the surface energy of ACF increased to 56.0 mJ/m ² . On the other hand, it was confirmed that the polar component and the dispersive component increased. Moreover, with the grafting of NH ₂ -Ti ₂ C sheets, the polar component in NH ₂ -Ti ₂ C-CF was 20.1 mJ/m ² _{, and the} dispersive component was as high as 46.6 mJ/m ² . As a result, the overall surface energy increased by 66.7 mJ/m ² , which contributed to the increase in the polar component of the polarized group generated from the grafted NH ₂ —Ti ₂ C. In addition, the increase of the dispersive component by NH ₂ -Ti ₂ C bonding increases the roughness. As such, the hydrophilicity and wettability enhancement of NH ₂ -Ti ₂ C-CF improves the interfacial strength between the fibers and the polymer matrix in the compound.

Experimental Example Result 3: Interfacial property evaluation

The interfacial strength of the NH ₂ -Ti ₂ C sheets was measured using IFSS and ILSS. Referring to Table 1, when the sizing of commercially available fibers was removed, the IFSS was reduced from 42.38 MPa to 40.57 MPa. After oxidation, the IFSS was slightly increased to 46.73 MPa by the -COOH group formed on the CF surface, which is believed to be due to the chemical bonding of the hydroxyl group and the oxirane group of the epoxy resin. After grafting the NH ₂ -Ti ₂ C sheet, the IFSS was significantly increased by 77.9% from 40.57 MPa to 72.17 MPa. The tensile strength was slightly decreased by 3.8% compared to the unsized CF. Very similar to the IFSS evaluation result of the compound, the ILSS value of the NH ₂ -Ti ₂ C-CF laminate was 44.24 MPa, which was high, and 27.8 compared to the non-sized CF laminate (34.63 MPa). % increased. As such, the improved interfacial properties mean that NH ₂ -Ti ₂ C is bonded. Since the epoxy monomer inter-diffuses through the NH ₂ -Ti ₂ C sheet and chemically bonds with the amine group of NH ₂ -Ti ₂ C, NH ₂ -Ti ₂ C in CF The grafting creates strong chemical covalent bonds between them as well as mechanical and chemical interlocking between the CF and the epoxy resin. Therefore, it means that greater strength will be required to pull the NH ₂ -Ti ₂ C terminus of the resin. When comparing the grafting method similar to the IFSS result and the values of related previous literature, Ti ₂ C showed improved interfacial properties compared to other nanomaterial compounds.

Additionally, the average length of fragmentation of unsized CF was about 592.6 μm, and after grafting NH ₂ -Ti ₂ C-CF on the surface, it was measured to be 386.5 μm (see Table 1). A shorter fragment length of NH ₂ -Ti ₂ C-CF was observed due to the combination of higher IFSS and small fiber strength. The formation of small fragments in the NH ₂ -Ti ₂ C-CF compound can also be confirmed through a birefringence pattern (see FIG. 4 ). Referring to FIG. 4b , the NH ₂ -Ti ₂ C-CF compound is gathered in one place and exhibits a smaller birefringence pattern, which means strong adhesion. Figure 4a relates to an unsized CF compound, and large break gaps and clearly debonded interfaces can be identified. This means relatively weak interfacial bond strength and stress transfer efficiency. Therefore, referring to Fig. 4c, which shows an unsized CF, a debond phenomenon often occurs at the interface. Conversely, referring to FIG. 4d showing the NH ₂ -Ti ₂ C-CF compound, it can be seen that the bond between the NH ₂ -Ti ₂ C-CF and the epoxy matrix is strengthened, and the apparently unbonded and protruding sideways are did not appear A similar phenomenon was also found in NH ₂ -Ti ₂ C-CF laminates.

Experimental Example Result 4: Unbound (failure) CF mixture mechanism

To investigate the observation of unbound mechanism response in CF reinforced polymer composition, AE experiment and SFFT (Single Fiber Fragmentation Test) were measured. In all cases observed during the tensile experiments, the AE signals were analyzed by means of a maximum frequency check. The maximum frequency was used to identify the failure mode in the subsequently reinforced fiber compound. Three distinct frequency ranges were clearly identified for both unsized CF and NH ₂ -Ti ₂ C-CF compounds, and the three identified failure modes were matrix cracking (50-120 kHz) and interface failure. ; 120-300 kHz), and fiber breakage (>300 kHz). Compared with the unsized compound, first, the most fiber breakage occurred in the NH ₂ -Ti ₂ C-CF compound, and the second most frequent case was the matrix breakage of the NH ₂ -Ti ₂ C-CF compound. . Finally, the occurrence of binding failure in NH ₂ -Ti ₂ C-CF compounds was shown to be low. And, also, NH ₂ -Ti ₂ Referring to Figure 5d about the C-CF compound, bonding initiation (Interface onset; a time point at which bonding failure occurs) 'fiber onset (Fiber onset; a time point at which fiber breakage occurs)' occurred almost simultaneously with On the other hand, referring to Figure 5c for the unsized CF compound, 'binding initiation' occurs first, and 'fiber initiation' occurs later in the CF compound. In both compounds, 'fiber initiation' occurs at approximately the same strain.

Fiber/matrix interface separation is caused by fiber breakage in the compound. However, at the NH ₂ -Ti ₂ C-CF compound interface, it was confirmed that the NH ₂ -Ti ₂ C sheet acts as a bridge such as a strong connection through a chemical bond between the fiber and the matrix (see FIG. 6e). NH ₂ -Ti ₂ C allows much more transfer of stress in the sheet matrix and prevents gold transfer along the interface when single fibers break in multiple short fibers. As a result, due to the occurrence of numerous fiber breakages, it could be confirmed that fewer bonding failures at the interface were observed, and the influence of a large number of micro-golds in the matrix can be confirmed through FIG. 6b . In fact, the SEM characterization of the sculptural surface structure can be confirmed from the aforementioned observations. Partial bond separation between the fibers and the matrix was often observed in the NH ₂ -Ti ₂ C-CF compound, but it was confirmed that all fibers were separated in the non-sized compound.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that you can.

Claims (13)

carbon fiber;
Maxine surface-modified with organic silane bonded to the carbon fiber (MXene); and
an epoxy resin combined with the maxine;
A structure that improves the interfacial strength between carbon fibers and epoxy resins. The structure of claim 1, wherein the organosilane comprises 3-aminopropyl triethoxysilane (APTES). According to claim 1, wherein the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the carbon fiber bonded to the modified maxine is not sized (unsized) carbon fiber (Carbon Fiber; CF) ) compared to 75 ~ 80%, 25 ~ 30%, respectively, characterized in that, the structure to improve the interfacial strength between the carbon fiber and the epoxy resin. Mixing organic silane and maxine to prepare a maxine solution whose surface is modified with organic silane; and
A manufacturing method for improving the interfacial strength of carbon fibers, including; a surface modification reaction step of mixing the carbon fiber with the maxine solution whose surface is modified with the organic silane. The method according to claim 4, wherein the organosilane comprises 3-aminopropyl triethoxysilane. [Claim 5] The interface of carbon fiber according to claim 4, wherein the surface modification reaction step is characterized in that the carbon fiber and modified maxin 2 to 8 mg, HATU 3 to 7 mg, and DMF 28 to 32 ml are mixed in a mixed solution. A manufacturing method that improves strength. According to claim 4, wherein the surface modification step is characterized in that the reaction for 3 to 5 hours at 85 ~ 95 ℃, manufacturing method for improving the interfacial strength of carbon fibers. Mixing organic silane and maxine to prepare a maxine solution whose surface is modified with organic silane;
mixing the maxine solution with the surface-modified surface of the organic silane and carbon fibers; and
Combining the maxine, carbon fiber mixture, and an epoxy resin; including, a method of manufacturing a structure for improving interfacial strength between carbon fibers and an epoxy resin. The method according to claim 8, wherein the organosilane comprises 3-aminopropyl triethoxysilane. The method of claim 8, wherein the surface modification reaction step is characterized in that the carbon fiber and the modified maxin 2 ~ 8 mg, HATU 3 ~ 7 mg, and DMF 28 ~ 32 ml of mixing in a mixed solution, carbon fiber and epoxy A manufacturing method for improving the interfacial strength between resins. According to claim 8, wherein the surface modification step is characterized in that the reaction at 85 ~ 95 ℃ for 3 ~ 5 hours, the method for improving the interfacial strength between the carbon fiber and the epoxy resin. A structure for improving the interfacial strength between carbon fibers and an epoxy resin, manufactured according to the method of any one of claims 8 to 11. 13. The method of claim 12, wherein the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the carbon fiber bonded to the modified maxine is not sized (unsized) carbon fiber (Carbon Fiber; CF) ) compared to 75 ~ 80%, 25 ~ 30%, respectively, characterized in that, the structure to improve the interfacial strength between the carbon fiber and the epoxy resin.

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