KR20220058130A - Polyamide-based carbon fiber reinforced composite material with enhanced bonding strength by light source and the method for producing the same - Google Patents

Abstract

In the present specification, provided is a carbon fiber reinforced composite material which comprises a plurality of laminated carbon fiber reinforced sheets including carbon fibers and polyamide-based polymers, wherein -NH- and CH_2- functional groups are present on a surface of the matrix of the polyamide-based polymer.

Description

Polyamide-based carbon fiber-reinforced composite material with improved adhesive strength by light source and manufacturing method thereof

The present specification relates to an improvement in the adhesive strength of a polyamide-based carbon fiber-reinforced composite material by a light source and a method for manufacturing the same.

Thermoplastic composite materials have better impact resistance and environmental resistance compared to thermoset composite materials, and are particularly characterized as eco-friendly lightweight materials because they can be recycled. Composite materials with strong brittleness are assembled and fastened through bonding rather than fastening through bolts and rivets through hole processing. Structural adhesives are mostly thermosetting polymer-based materials and have a problem of low adhesive strength with thermoplastic composite materials.

Mechanical surface treatment methods such as sanding or sand blasting, which are widely used in the past to improve adhesive strength, damage the fibers on the surface of the composite material and have a problem of lowering physical properties, and also acid surface treatment (acid surface treatment) Chemical surface treatment methods such as surface treatment) or private coating have also been pointed out as difficult to apply to thermoplastic composite materials.

On the other hand, plasma surface treatment, which has been recently studied, is effective, but it is difficult to treat a large area and is a relatively expensive process, so it is difficult to apply to a general structure.

Therefore, there is a demand for the development of a technology for effectively increasing the adhesive strength by treating a large area of the surface of a thermoplastic composite material at a low price.

In order to solve this problem, the embodiments according to the present invention introduce a surface treatment method using a light source to treat a large area of a thermoplastic composite material at a low price to improve adhesion.

In addition, by improving the adhesive strength of polyamide-based composite materials through surface treatment, it is intended to make it possible to substitute and utilize thermosetting composite materials for various lightweight moving objects (bus, passenger car, aircraft, etc.) and structures.

In addition, in the conventional mechanical bonding method, in the process of making an opening for bonding, damage to the surface and fibers is caused to solve the problem of deterioration of physical properties.

In one embodiment according to the present invention to achieve the above object, a plurality of laminated carbon fiber reinforced sheets comprising carbon fibers and a polyamide-based polymer is included, and on the surface of the matrix of the polyamide-based polymer Provided is a carbon fiber-reinforced composite material in which -NH- and CH ₂ - functional groups exist.

In one embodiment, -NH- and CH ₂ - functional groups derived from the amide bond (CONH ₂ ) of the polyamide-based polymer may be present on the surface of the matrix of the polyamide-based polymer.

In one embodiment, the surface of the carbon fiber-reinforced composite material may have an NH stretching peak and a -CH ₂ stretching peak according to FTIR measurement.

In one embodiment, the adhesive layer comprising a thermosetting adhesive; may further include.

In one embodiment, the -NH- and CH ₂ - functional groups may form a chemical bond with the OH- functional group of the thermosetting adhesive.

In another embodiment according to the present invention, preparing a carbon fiber reinforced composite; and surface-treating by irradiating a light source on the carbon fiber-reinforced composite.

In one embodiment, in the surface treatment step, an amide bond (CONH ₂ ) on the surface of the carbon fiber-reinforced composite material may be photo-scissed by a light source.

In one embodiment, in the surface treatment step, the matrix of the polyamide-based polymer may not be oxidized, carbonized, or chemically decomposed.

In one embodiment, the light source may have a power density of less than 1.4 J/mm ² .

In one embodiment, an adhesive layer including a thermosetting adhesive may be formed on the surface-treated carbon fiber-reinforced composite.

The carbon fiber-reinforced composite material according to embodiments of the present invention has a large area without this limitation, unlike conventional mechanical surface treatment methods or chemical surface treatment methods that damage the reinforcing fibers on the surface or are difficult to apply to thermoplastic polymers. Surface treatment is possible on the surface of the thermoplastic composite material to improve adhesion.

1 shows a schematic diagram of a step in which an amide bond (CONH ₂ ) on the surface of a carbon fiber-reinforced composite material is irradiated with a laser light source to the surface of the carbon fiber-reinforced composite material in an embodiment of the present invention is photo-scission.
Figure 2a shows the FTIR measurement result of the carbon fiber-reinforced composite material surface-treated by irradiating a laser light source to the surface of the carbon fiber-reinforced composite in an embodiment of the present invention.
Figure 2b shows the FTIR measurement results of the carbon fiber-reinforced composite material surface-treated by irradiating the surface of the carbon fiber-reinforced composite with a UV light source having λ=365 mm in the embodiment of the present invention.
Figure 2c shows the FTIR measurement results of the carbon fiber-reinforced composite material surface-treated by irradiating the surface of the carbon fiber-reinforced composite by varying the power of the laser light source in the embodiment of the present invention.
Figure 3a shows the result of comparing the adhesive strength of the carbon fiber-reinforced composite material surface-treated by irradiating a laser light source to the surface of the carbon fiber-reinforced composite in an embodiment of the present invention.
Figure 3b shows the result of comparing the adhesive strength of the carbon fiber reinforced composite material surface-treated by irradiating the surface of the carbon fiber reinforced composite with a UV light source having λ = 365 mm in the embodiment of the present invention.
Figure 4a shows the surface of the adhesive body destroyed after the adhesion test of the carbon fiber-reinforced composite not surface-treated with a light source.
Figure 4b shows the surface of the adhesive body destroyed after the adhesion test of the carbon fiber-reinforced composite surface-treated with a laser light source.
Figure 4c shows the surface of the adhesive body destroyed after the adhesion test of the carbon fiber-reinforced composite surface-treated with a UV light source of λ = 365 mm.
5 is a cross-sectional view of a carbon fiber-reinforced composite surface-treated with a laser light source, showing the thickness of the matrix (resin) burned by the laser light source.
6 shows a comparison result of the adhesive strength of the carbon fiber-reinforced composite surface-treated by varying the output of the laser light source.

Hereinafter, embodiments of the present invention will be described in more detail.

The embodiments of the present invention disclosed in the text are illustrated for the purpose of explanation only, and the embodiments of the present invention may be embodied in various forms and should not be construed as being limited to the embodiments described in the text. .

The present invention can make various changes and can have various forms, and the embodiments are not intended to limit the present invention to a specific disclosed form, and all changes, equivalents or substitutes included in the spirit and scope of the present invention should be understood as including

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, number, step, operation, component, part, or a combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Carbon Fiber Reinforced Composite Material

In one embodiment according to the present invention to achieve the above object, a plurality of laminated carbon fiber reinforced sheets comprising carbon fibers and a polyamide-based polymer is included, and on the surface of the matrix of the polyamide-based polymer Provided is a carbon fiber-reinforced composite material in which -NH- and CH ₂ - functional groups exist.

In one embodiment, -NH- and CH ₂ - functional groups derived from the amide bond (CONH ₂ ) of the polyamide-based polymer may be present on the surface of the matrix of the polyamide-based polymer. For example, the polyamide-based polymer includes polyamide 6 (PA6, nylon 6), polyamide 66 (PA 66, nylon 66), or polyamide 12 (PA 12, nylon 12) depending on the molecular structure of the polymer. It can be, and if it includes an amide bond (CONH ₂ ) in the polymer, it is not limited thereto. Preferably, the polyamide-based polymer may be polyamide 6 or polyamide 66, and when applied to a structural composite material, it may have excellent strength and rigidity.

In one embodiment, the carbon fibers may be arranged in one direction on the matrix of the polyamide-based polymer. Meanwhile, adjacent reinforcing fiber sheets may have the same or different arrangement directions of reinforcing fibers. For example, one laminated carbon fiber reinforced sheet may have weak lateral stiffness when the other laminated carbon fiber reinforced sheet and the carbon fibers are arranged in the same direction, that is, when arranged in a unidirectional (UD) direction. can have excellent strength characteristics.

On the other hand, when one laminated carbon fiber reinforced sheet and the other laminated carbon fiber reinforced sheet have different alignment directions of carbon fibers, physical properties may be improved. For example, adjacent reinforcing fiber sheets may be laminated with the reinforcing fiber arrangement direction of 0°, 45°, or 90°, and preferably, adjacent reinforcing fiber sheets are laminated with the reinforcing fiber arrangement direction of 90°. can be

In one embodiment, the thickness of the plurality of reinforcing fiber sheets may vary in the number of layers depending on the applied thickness. For example, the plurality of reinforcing fiber sheets may be laminated in two or more layers. When the reinforcing fiber sheet is laminated in less than two layers, the reinforcing fibers arranged in one direction in the reinforcing fiber sheet cannot be laminated because adjacent sheets have different arrangement directions, so it may be difficult to improve properties.

In one embodiment, the carbon fiber reinforced sheet may include carbon fibers, and the carbon fibers may be woven or non-woven reinforced fibers. Specifically, the woven carbon fiber may include a woven carbon fiber such as a unidirectional (UD) fabric, an NCF, a plain weave, a twill weave, a silk weave, and a basket structure.

In one embodiment, the matrix thickness of one portion and the other portion in which -NH- and CH ₂ - functional groups are present on the surface of the matrix of the polyamide-based polymer may be substantially the same. Specifically, in the case of optical separation of the surface of the polyamide-based polymer matrix in the carbon fiber-reinforced composite material, the polymer on the surface of the polymer matrix may be removed together by oxidation, carbonization, decomposition, etc. by a light source. In this case, the surface of the polyamide-based polymer matrix having -NH- and CH ₂ - functional groups formed by light separation is partially removed, so that a portion of the carbon fiber may be exposed on the surface. When the carbon fiber is exposed to the surface of the polymer matrix, it can have a higher adhesion to the thermosetting adhesive compared to the matrix material. However, in this case, as in the mechanical surface treatment method, the physical properties of the composite material itself may be reduced, and if the power of the light source to remove the polymer matrix becomes larger, the carbon fiber or the interface between the carbon fiber and the polymer resin is damaged and the fiber is pulled out. It may be damaged, such as cracking or breaking, and the adhesive strength may become smaller.

In one embodiment, the surface of the carbon fiber-reinforced composite material may have NH stretching peaks and -CH ₂ stretching peaks according to FTIR measurement, and the NH stretching peaks and -CH ₂ stretching peaks are the polyamide-based polymer matrix. The amide bond (CONH ₂ ) on the surface may not exist before photo-cleavage.

In one embodiment, based on the total volume of the carbon fiber-reinforced composite material, 50 to 70% by volume of carbon fibers may be included. When the content of the carbon fiber is less than 50% by volume, the reinforcing effect of the carbon fiber may be small, and when it is more than 70% by volume, the -NH- and CH ₂ - formed by light separation may have little improvement in adhesion due to the absence of functional groups there is.

In one embodiment, the adhesive layer comprising a thermosetting adhesive; may further include. The thermosetting adhesive has excellent adhesion compared to a thermoplastic adhesive such as a heat-sealing film or a heat-sealing adhesive. In particular, these thermoplastic adhesives have very poor adhesiveness, so that they cannot be used in structures such as automobiles. In addition, for thermal fusion, the thermoplastic adhesive must be heated to a high enough temperature to completely melt. In this process, the composite material to be bonded is damaged, and therefore, it is used only for bonding metal materials. On the other hand, the adhesive layer including the thermosetting adhesive may have excellent adhesive strength by bonding on the surface of the carbon fiber-reinforced composite material without this problem.

It is possible to bond the carbon fiber-reinforced composite material and the member to be applied through the adhesive layer, but an opening is not required for mechanical bonding with the member, and the fiber is not mechanically damaged in the process of forming the opening, and excellent Mechanical properties can be maintained. That is, the carbon fiber-reinforced composite material may not include a structure such as an opening for mechanical bonding.

In one embodiment, the -NH- and CH ₂ - functional groups may form a chemical bond with the OH- functional group of the thermosetting adhesive. For example, the chemical bond may be a hydrogen bond. It is possible to improve the adhesive strength through the formation of such a chemical bond, and by improving the adhesive strength, it can be used to replace or apply conventional thermosetting composite materials in various lightweight moving objects (bus, passenger car, aircraft, etc.) and structures.

Carbon Fiber Reinforced Composite Material Manufacturing Method

In another embodiment according to the present invention, preparing a carbon fiber reinforced composite; and surface-treating by irradiating a light source on the carbon fiber-reinforced composite.

In the carbon fiber-reinforced composite material manufacturing method through surface treatment according to such light source irradiation, mechanical surface treatment methods such as sanding or sandblasting, which have been widely used in the prior art, damage the fibers on the surface of the composite material and reduce the physical properties, acid treatment or Unlike a chemical surface treatment method such as primer coating, which is difficult to apply to a thermoplastic composite material, it can be applied to various materials including a thermoplastic polymer while maintaining excellent physical properties.

First, a carbon fiber-reinforced composite may be prepared. The carbon fiber and polyamide-based polymer used may be the same as those described above.

In one embodiment, the carbon fiber reinforced composite may be manufactured by laminating a reinforcing fiber sheet that is a prepreg, and specifically, the prepreg includes a plurality of carbon fiber reinforced sheets including a plurality of reinforcing fibers arranged in one direction. It may be formed by laminating it in layers, and the reinforcing fiber may be impregnated with a polymer resin.

Next, it can be surface-treated by irradiating a light source on the prepared carbon fiber-reinforced composite.

In one embodiment, in the surface treatment step, an amide bond (CONH ₂ ) on the surface of the carbon fiber-reinforced composite material may be photo-scissed by a light source. The photo-isolated surface may include a plurality of -NH- and CH ₂ - functional groups, through which adhesive strength may be improved.

Accordingly, through the surface treatment, the surface of the carbon fiber-reinforced composite material may have an NH stretching peak and a -CH ₂ stretching peak according to FTIR measurement. Here, the NH stretching peak may be located in ^the vicinity of ³²⁹⁰ cm ^-1 , ^and the -CH ₂ stretching peak may be located in the vicinity of 2860 cm ^-1 and 2930 cm -1. The NH stretching peak and -CH ₂ stretching peak do not exist before the amide bond (CONH ₂ ) on the surface of the polyamide-based polymer matrix is photo-separated, and the photo-separated surface is -NH- and CH ₂ - functional groups indicates that it contains many.

In one embodiment, in the surface treatment step, the matrix of the polyamide-based polymer may not be oxidized, carbonized, or chemically decomposed. Therefore, the thickness of the matrix of the polyamide-based polymer before/after the surface treatment step can be maintained. Specifically, the polymer on the surface of the polymer matrix may be removed by oxidation, carbonization, decomposition, etc. by the light source, and a portion of the carbon fiber may be exposed in the portion where the polymer matrix is partially removed. As described above, the carbon fiber When exposed to the surface of the polymer matrix, it may have higher adhesion to the thermosetting adhesive compared to the matrix material, but if the light source output is too large, the adhesion may be rather small due to damage to the carbon fiber.

On the other hand, when the surface roughness increases as the polymer matrix is removed and the carbon fibers are exposed to the surface of the polymer matrix, the adhesion may increase due to the effect of physical surface treatment.

In one embodiment, the light source may include a laser or UV light source, and may include, without limitation, any light source capable of photolysis of an amide bond to form -NH- and/or CH ₂ - functional groups.

In one embodiment, the light source may have a power density of less than 1.4 J/mm ² . When the power density of the light source is greater than 1.4 J/mm ² , the polymer matrix itself can be removed by burning, oxidizing, and decomposing the polymer itself beyond the separation of the photoamide bond, and the photolysis effect is not obtained and the carbon fiber is heated The peripheral thermoplastic resin may be melted, causing interfacial delamination between the resin and the fiber.

In one embodiment, an adhesive layer including a thermosetting adhesive may be formed on the surface-treated carbon fiber-reinforced composite.

Example

Hereinafter, the configuration and effect of the present invention will be described in more detail by way of examples. However, these examples are provided only for the purpose of illustration to help the understanding of the present invention, and the scope and scope of the present invention are not limited by the following examples.

Example 1: Preparation of polyamide-based carbon fiber-reinforced composite material (CFRTP)

Carbon fiber/PA6 prepreg (Kolon Plastics, Korea) was used to prepare a carbon fiber reinforced composite with the lamination order [0 ₈ /90 ₈ /0 ₈ ], and then autoclave vacuum bag at 250℃ 7 bar condition. CFRTP was prepared by degassing (autoclave vacuum bag degassing method).

Here, the prepreg was contained in an amount of 60% by volume based on the total volume of CFRTP using T300 carbon fiber (Toray, Japan). The thickness of the specimen was about 3.5 mm, and it was prepared by cutting with a water jet cutter (SUPERJET T500-3015, TOPS, Korea).

Example 2: Preparation of laser surface-treated carbon fiber-reinforced composite material

CFRTP of Example 1 was surface-treated with a laser light source. The CFRTP surface was processed using a Gaussian beam using a CO ₂ laser source and a pulse wave (PW) mode laser scanning device (ILS 12.75, Universal Laser Systems, USA). The laser head was controlled by an automated CNC (Computerized Numerical Control) system and processed by moving along the fiber direction with a 0.2 mm hatch distance and 1,000 mm/s scanning speed.

A laser beam with a wavelength of 10.6 μm was used, and an 18 mm diameter lens was used to focus at a focal length of 50.8 mm and a spot diameter of 0.13 mm.

Then, an adhesive layer was formed on the surface-treated adhesive surface using an epoxy film adhesive (Shinsung Composite Material, Korea). The thickness was adjusted to 0.32 mm using a PTFE thickness gauge (Tool tech, Air-tech, USA), and the formed adhesive layer was cured by autoclave vacuum bag degassing at 120° C. and 1 bar conditions for 2 hours.

Example 3: UV surface-treated carbon fiber reinforced composite material preparation

A carbon fiber-reinforced composite material was prepared in the same manner as in Example 2, except that the surface was treated with a UV light source having λ=365 mm instead of a laser light source.

Experimental Example 1: Surface structure analysis (FTIR) according to the light separation reaction

The properties of the CFRTP surface treated with a light source were analyzed by Fourier transform infrared spectroscopy (FTIR). FTIR was measured with an ATR device equipped with a diamond crystal (6600FV, Jasco, Japan). The measured spectral range was 750 ~ 4000 cm ^-1 , and it was measured by performing 32 scans at 4 cm ^-1 resolution.

Figure 2a shows the FTIR measurement result of the carbon fiber-reinforced composite material surface-treated by irradiating a laser light source to the surface of the carbon fiber-reinforced composite in an embodiment of the present invention. After laser treatment on the surface of the carbon fiber reinforced composite material, it was confirmed that the peak intensity was significantly changed at 3290 cm ^-1 , 2925 cm ^-1 and 2856 cm ^-1 . Here, it is widely known that the peak located at 3290 cm ^-1 corresponds to the NH stretching vibration, and the peak located at 2860 cm ^-1 and 2930 cm ^-1 corresponds to the symmetric and asymmetric -CH ₂ stretching vibration, respectively.

In addition, it was confirmed that the intensity of the peak changed significantly at 3290 cm ^-1 , 2925 cm ^-1 and 2856 cm ^-1 also in FIG. 2b using a UV light source with λ = 365 mm as the irradiation light source, and it was confirmed that the light separation phenomenon was observed even if the light source type was changed. can

Meanwhile, FIG. 2C shows the result of surface treatment by varying the power of the light source.

NH and -CH ₂ -stretching oscillation peak intensity increased after 1.4 J/mm ² power laser treatment. In this case, it can be seen that the enemy requires at least 1.4 J/mm ² power for the photo-separation reaction.

Through the light separation reaction, the carbonyl group (C=O) was vaporized in the form of carbon monoxide (C≡O), thereby increasing free NH (not hydrogen bonding) and -CH ₂ - elongation on the CFRTP surface. The newly formed NH stretching may improve the OH and hydrogen bonding of the epoxy adhesive, thereby increasing the interfacial bonding strength. On the other hand, the NH stretching originally present in PA 6 cannot form hydrogen bonds with the epoxy adhesive because it has already formed hydrogen bonds with C=O in PA 6 .

On the other hand, the FTIR intensity of CFRTP treated with laser power higher than 2.8 J/mm ² showed the same FTIR spectral result as that of untreated CFRTP. As can be seen in FIG. 2c, as a result of irradiating a laser beam having an output of 2.8 J/mm ² or more, PA6 was burned and removed as NOx and CH ₄ . That is, NH stretching and the epoxy adhesive cannot form hydrogen bonds when laser treatment with a power of 2.8 J/mm ² or higher, and when surface treatment with a power laser of 1.4 J/mm ² forms a strong interface, the maximum with the epoxy adhesive It can be confirmed that the adhesive bond strength is formed.

Experimental Example 2: Adhesive strength measurement

The adhesive strength according to the laser and UV light source surface treatment was compared by measuring the lap shear strength. The shear strength test was performed according to ASTM D3163-01, and the crosshead speed was 2 mm/min.

First, Figure 3a compares the adhesive strength of the carbon fiber-reinforced composite material surface-treated by irradiating a laser light source to the surface of the carbon fiber-reinforced composite in an embodiment of the present invention. It can be seen that the adhesive strength without laser treatment was 10.3 MPa, whereas it was increased by about 150% to 25.5 MPa with laser irradiation.

On the other hand, referring to Figure 3b, when the surface treatment with a UV light source, the adhesive strength after treatment is improved to 17.7 MPa compared to the adhesive strength before laser treatment of 10.3 MPa, compared to the surface treatment with a laser light source, the increase in adhesive strength is smaller can be checked

Experimental Example 3: Surface morphology analysis after adhesive strength measurement experiment

1) FIGS. 4a to 4c show images of the adhesive surface that was broken after lap shear test of the laser surface-treated CFRTP surface ( FIG. 4b ) and the UV light source surface-treated CFRTP surface ( FIG. 4c ). Images were observed using a digital optical microscope (VHX-900F, Keyence Corporation, Japan).

Figure 4a shows the surface of the adhesive agent destroyed after the adhesion test of the carbon fiber-reinforced composite not subjected to surface treatment with a light source, and it can be confirmed that peeling occurs easily between the surface of the composite material and the adhesive and has a neat adhesive surface after destruction.

4b and 4c show the surface of the destroyed adhesive after the adhesion test of the carbon fiber-reinforced composite surface-treated with a laser light source and a UV light source having λ = 365 mm, respectively. When the surface treatment is performed with a laser and a UV light source, the surface treatment is performed Compared with the sample without (Fig. 4a), it can be seen that the polymer resin-rich portion of the adhesive surface subjected to the adhesion test is completely removed and the carbon fibers are exposed on the surface.

In particular, FIG. 4b shows a fracture cross-section in which the fiber is pulled out from the surface of the destroyed adhesive after the shear strength test in the carbon fiber reinforced composite surface-treated with a laser light source, which is that the carbon fiber is heated by the light source and the surrounding thermoplastic resin is melted. This is the result of interfacial delamination between the resin and the fiber. In this case, the carbon fiber is easily pulled out from the polymer resin, and the adhesive force is rather reduced.

Figure 4c shows the surface of the adhesive fractured after the shear strength test in the carbon fiber-reinforced composite surface-treated with a UV light source of λ = 365 mm, and the polyamide resin on the surface of the composite material fell off due to strong adhesion with the polyamide and the adhesive. You can check what came out.

2) Meanwhile, FIG. 5 shows a cross-sectional image of the CFRTP surface according to the laser surface treatment and the thickness of the burned polymer resin according to the output power of the laser. Here, for comparison, a sample ('PA 6 Block') prepared in the same manner as in Example 1 using a PA6 prepreg without carbon fiber reinforcement was applied.

As a result, it was confirmed that both CFRTP (Example 1) and PA 6 Block increased in proportion to the surface treatment depth as the laser output increased at a low output power of about 4.3 J/mm ² or less. However, when the surface was treated with a laser with an output of about 1.4 J/mm ² or less, the surface shape of both samples was hardly affected.

In the PA 6 Block, the surface treatment depth increased in proportion to the laser output in the output range of 2.8 J/mm ² ~ 7 J/mm ² , but in the case of CFRTP, the surface treatment depth converged to about 20 μm, which was about 3 layers of carbon fiber. corresponding to the thickness. At this time, a thickness of about 20 μm corresponds to the thickness of the resin rich area on the CFRTP surface, and carbon fibers existing in a thickness greater than that are not removed by the laser. Accordingly, a significant portion of the polymer resin matrix on the surface of CFRTP may be removed to expose carbon fibers.

If the laser output power is too high, the carbon fiber is heated by the laser and the surrounding thermosetting resin is melted, causing delamination of the interface between the resin and the fiber, which causes the carbon fiber to be easily pulled out and the adhesive force is rather reduced. will do

Therefore, the carbon fiber of CFRTP may be damaged, and in this case, the mechanical properties of the composite material may be deteriorated. Therefore, it is necessary to minimize the damage to the carbon fiber by adjusting the laser power.

3) Accordingly, the output value of the light source having high shear strength while minimizing damage to the carbon fiber was confirmed. To this end, the shear strength of the samples prepared by varying the laser output power in Example 2 was measured, and the results are shown in FIG. 6 .

Referring to FIG. 6 , it can be confirmed that the resin on the surface is not removed or melted by the laser, but has the maximum adhesion at a power of 1.4 J/mm ² where only photolysis occurs. In other words, with laser treatment of 1.4 J/mm ² power, -NH- and CH ₂ - functional groups are created through photolysis of the surface amide resin to improve adhesion. It can be seen that this is because it is decomposed and consequently the adhesive force is rather reduced.

On the other hand, at an output of 2.1 J/mm ² or more, it can be seen that the adhesive force rises again as the output increases.

Therefore, it can be seen that the carbon fiber-reinforced composite material according to the present invention has excellent adhesion by light-separating the surface with -NH- and CH ₂ - functional groups while minimizing damage to the polymer resin.

The embodiments of the present invention described above should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and it is possible for those of ordinary skill in the art to improve and change the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the protection scope of the present invention as long as it is apparent to those of ordinary skill in the art.

Claims (11)

A plurality of laminated carbon fiber-reinforced sheets comprising carbon fibers and polyamide-based polymers;
A carbon fiber-reinforced composite material in which -NH- and CH ₂ - functional groups exist on the surface of the matrix of the polyamide-based polymer. According to claim 1,
A carbon fiber-reinforced composite material in which -NH- and CH ₂ - functional groups derived from the amide bond (CONH ₂ ) of the polyamide-based polymer exist on the surface of the polyamide-based polymer matrix. According to claim 1,
The surface of the carbon fiber-reinforced composite material has an NH stretching peak and a -CH ₂ stretching peak according to FTIR measurement, a carbon fiber-reinforced composite material. According to claim 1,
With respect to the total volume of the carbon fiber-reinforced composite material, the carbon fiber-reinforced composite material comprising 50-70% by volume of carbon fibers. According to claim 1,
An adhesive layer comprising a thermosetting adhesive; further comprising, a carbon fiber-reinforced composite material. 6. The method of claim 5,
The -NH- and CH ₂ - functional groups form a chemical bond with the OH- functional group of the thermosetting adhesive, carbon fiber reinforced composite material. Preparing a carbon fiber reinforced composite; and
A method for producing a carbon fiber-reinforced composite material, including; surface treatment by irradiating a light source on the carbon fiber-reinforced composite. 8. The method of claim 7,
In the surface treatment step, the amide bond (CONH ₂ ) on the surface of the carbon fiber-reinforced composite material by the light source is optically separated (photo scission), a carbon fiber-reinforced composite material manufacturing method. 8. The method of claim 7,
In the surface treatment step, the matrix of the polyamide-based polymer is not oxidized, carbonized, or chemically decomposed, carbon fiber-reinforced composite material manufacturing method. 8. The method of claim 7,
The light source has a power density of less than 1.4 J / mm ² , carbon fiber reinforced composite material manufacturing method. 8. The method of claim 7,
Forming an adhesive layer comprising a thermosetting adhesive on the surface-treated carbon fiber reinforced composite, carbon fiber reinforced composite material manufacturing method.

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