KR100887832B1 - Jointing method between composition and steel - Google Patents

Abstract

The present invention utilizes the extra resin flowing out during the curing of the composite material as an adhesive when joining a flat plate carbon fiber-epoxy composite material and steel material, co-cured single lap joint (co-cured single lap joint) The present invention relates to a method of simultaneously hardening joints between carbon fiber-epoxy composites and steel materials to improve the joint strength and to be useful for the design of composite parts used in automobiles.

To this end, the present invention comprises the steps of polishing the surface of the steel material with sandpaper and then wiped with acetone; Stacking the uncured composite material in size and thickness; Pre-bonding the joint surface of the composite material and the steel material with a finger to pre-bond the joint surface; Covering the upper and lower surfaces of the temporarily bonded composite material and the steel material with a Teflon film, and simultaneously placing a resin blocking Teflon dam at a rim position; Vacuum packing the composite material and the steel material in a state where a Teflon film and a resin blocking Teflon dam are disposed; Putting a vacuum-packed composite material and steel material together with a Teflon film and resin blocking Teflon dam into an autoclave, connecting it to a pressure hose for pressurization, applying a predetermined pressure, and performing a curing process according to a temperature cycle; ; The resin contained in the composite material is bonded to the surface of the steel material by hardening, and thus the composite material and the steel material is bonded to provide a co-cured bonding method between the carbon fiber-epoxy composite material and the steel material. do.

Composite materials, steel materials, simultaneous hardening method, resin, orientation angle, surface roughness, outer surface overlap, joint strength,

Description

Joining method between composition and steel}

1 is a schematic diagram illustrating a method of co-curing bonding between a carbon fiber-epoxy composite material and a steel material according to the present invention;

2 is a plan view and a side view showing a specimen manufactured by a method of co-curing bonding between a carbon fiber-epoxy composite material and a steel material according to the present invention;

Figure 3 is a graph showing the relationship between the sandpaper mesh and the average surface roughness polishing the steel material joint surface according to the present invention,

4 is a graph showing the bonding strength according to the surface roughness of the steel material according to the present invention,

5 is a graph showing the bonding strength according to the bet pressure applied to the carbon fiber-epoxy composite material and the steel material according to the present invention;

6 is a graph showing the bond strength according to the change of the fiber orientation angle of the carbon fiber-epoxy composite according to the present invention.

The present invention relates to a method of simultaneous hardening bonding between carbon fiber-epoxy composite material and steel material, wherein when the flat carbon fiber-epoxy composite material and steel material are joined, the extra resin flowing out during curing of the composite material is used as an adhesive. Carbon fiber-epoxy composites and steels to improve the joint strength of co-cured single lap joints, such as surface overlap, and to be useful in the design of composite parts used in automobiles. A method of simultaneous hardening bonding between materials.

At present, even though there are scattered parts that require a combination of composite and steel materials in the aircraft or automobile field, research on direct bonding technology between composite materials such as carbon fiber and steel materials is currently unknown.

Since steel materials are used the most in various industrial structures including automobiles, many structural forms that need to join steel materials with composite materials with excellent mechanical performance will be generated. There is an urgent need for development of ways to improve.

Accordingly, there are increasing cases of using carbon fiber-epoxy composite materials for aircraft and automobile parts as well as excellent mechanical properties including non-rigidity and specific strength.

In spite of many advantages of the composite material, in order to bond the composite material to steel materials which are widely used in automobile structures and to utilize them as automobile structures or parts, a complete formulation of the bonding technology process is required.

In general, the bonding method of the composite material includes a mechanical bonding method and a bonding method using an adhesive, but in the case of the composite material, the bonding strength using a gluing agent is widely used because the mechanical strength is greatly reduced.

However, the conventional bonding method using the adhesive does not exhibit the inherent characteristics of the composite material as it contains another adhesive component, and the bonding manufacturing process using the adhesive is actually difficult to be utilized due to the complexity.

The present invention simplifies the bonding process required to utilize the carbon fiber-epoxy composite material having excellent mechanical properties in various mechanical structures, and flows during curing of the composite material when joining the carbon fiber-epoxy composite material and steel material into a flat plate. By using the excess resin as adhesive, it improves the bonding strength of co-cured single lap joints such as surface overlap and makes it useful for designing composite parts used in automobiles. The object is to provide a method of co-curing bonding between fiber-epoxy composites and steel materials.

That is, the present invention is a method of using the excess resin flowing out during the curing process of the composite material as an adhesive, the surface treatment of the bonding surface of the composite material and the bonding process using the adhesive that is essential if a separate adhesive is conventionally used Since this is not necessary, the objective is to provide a method of co-curing bonding between carbon fiber-epoxy composites and steel materials in which the entire bonding process is very simple.

The present invention for achieving the above object is the step of polishing with acetone after polishing the surface of the steel material with sandpaper; Stacking the uncured composite material in size and thickness; Pre-bonding the joint surface of the composite material and the steel material with a finger to pre-bond the joint surface; Covering the upper and lower surfaces of the temporarily bonded composite material and the steel material with a Teflon film, and simultaneously placing a resin blocking Teflon dam at a rim position; Vacuum packing the composite material and the steel material in a state where a Teflon film and a resin blocking Teflon dam are disposed; Putting a vacuum-packed composite material and steel material together with a Teflon film and resin blocking Teflon dam into an autoclave, connecting it to a pressure hose for pressurization, applying a predetermined pressure, and performing a curing process according to a temperature cycle; ; The resin contained in the composite material is bonded to the surface of the steel material by hardening, and thus the composite material and the steel material is bonded to provide a co-cured bonding method between the carbon fiber-epoxy composite material and the steel material. do.

In a preferred embodiment, after the joining process, the step of reducing the stress concentration by processing the sharp edge of the joint surface is characterized in that the further progress.

Preferably, the surface of the steel material is characterized in that the surface roughness is polished to 0.2 ~ 1.7㎛.

In addition, the pressure applied to the composite material and the steel material is preferably 0.4 to 1.0 Mpa.

In addition, the orientation angle of the fibers contained in the composite material is preferably 20 to 60 degrees in the plane parallel to the steel material.

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

First, the terms used below are defined as follows.

1) The term 'simultaneous curing' means that when the composite material is cured, the bonding process with the steel material is simultaneously performed using the resin in the composite material.

2) The term 'overlap' is used when two or more materials are joined together when there is one joint surface, and when there are two joint surfaces, the term 'overlap on both sides' is used.

3) The term 'orientation angle' refers to the orientation direction of the fibers contained in the composite material, and indicates the angle of inclination with respect to the reference coordinate and the angle of inclination in the plane parallel to the steel material.

1 is a schematic diagram illustrating a co-cured bonding method between a carbon fiber-epoxy composite material and a steel material according to the present invention, and FIG. 2 is a co-cured bonding method between a carbon fiber-epoxy composite material and a steel material according to the present invention. A plan view and a side view showing a specimen fabricated with.

As a first step in the method of co-curing bonding between the carbon fiber-epoxy composite material and the steel material according to the present invention, the surface of the steel material is sanded with sandpaper, and the surface of the steel material is polished to a surface roughness of 0.2 to 1.7 mu m.

The polishing of the steel material is a surface treatment process using sandpaper. After polishing with sandpaper, the steel material is polished with various chemicals such as acetone.

In other words, after polishing with sandpaper, the bonding strength can be improved by wiping the bonding surface with acetone.

As a second step, the uncured composite material is laminated according to size and thickness, and the orientation direction of the fibers in the composite material is determined and laminated.

At this time, the orientation angle of the fibers contained in the preferred composite material is 20 to 60 degrees.

As a third step, by pressing the joint surface of the composite material and the steel material with a finger to pre-bonding (pre-bonding) to position the joint surface in advance.

In other words, when pre-bonding the joint surface of composite material with steel material, care should be taken not to contaminate the joint surface and care should be taken to prevent the moisture in the air from affecting the joint surface as soon as possible. .

In addition, after the temporary bonding of the composite material and the steel material by applying a finger pressure (Finger pressure) in the vertical direction to the joint surface is pressed so as not to fall.

As a fourth and fifth step, covering the temporarily bonded composite material and steel material with the Teflon film on the upper and lower surfaces, and placing the resin blocking Teflon dam at the four edges, and the Teflon film and the Teflon blocking resin. Vacuum packing the composite and steel materials in a state where the dam is disposed.

The reason why the Teflon film is covered on the top and bottom of the composite material and steel material is to allow the resin in the composite material to flow well between the valleys and valleys of the joint surface without leaving the flow out, and to serve as an adhesive. .

In addition, the side of the composite material and steel material is because the dam is installed to prevent the flow of resin, the material to be used as a dam Teflon block in order to prevent the joint is made by the joint hardening joint structure and resin It is good to use

Finally, the vacuum-packed composite and steel materials, together with the Teflon film and resin blocking Teflon dam, are placed in an autoclave and connected to a pressure hose for pressurization to apply a predetermined pressure and perform a curing process according to the temperature cycle. do.

Simultaneous hardening The process of bonding the composite and steel materials vacuum-packed together with the Teflon film and resin blocking Teflon dam in an autoclave according to the cycle, and setting the curing cycle according to the composite material manufacturing process. The pressure (pressure applied to the composite material and the steel material) is preferably 0.4 to 1.0 Mpa.

Thus, the resin contained in the composite material is bonded to the surface of the steel material by hardening, so that the composite material and the steel material are easily bonded.

Preferably, after the bonding process as described above, the step of reducing the stress concentration by processing the sharp edge of the bonding surface is further progressed.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The following examples are only intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited to the examples.

Examples and Experimental Examples

The components and manufacturing methods of the fibers and resins constituting the composite material used in the present invention are as follows.

-Manufacturer: SK Chemicals

-Product Name: USN150BX Prepreg (Thickness-0.144mm, Mass 224g / m ² )

Composition ratio: 150 g / m ² (fiber), 33 g / m ² (resin)

-Type of fiber: carbon fiber

-Type of resin: epoxy resin (Bisphenol A)

The MTS (Materials Testing Systems) of up to 10ton capacity was used to measure the joint strength of the overlapping joint hardening joint between the composite material and the steel material, and manufactured by Rank Taylor-Hobson Limited to measure the surface roughness of the steel material. Surtronic 3+, a surface-contact surface roughness measuring instrument, was used.

Using the surface roughness measuring instrument, not only the average surface roughness of the steel material was obtained, but also the highest surface roughness was measured to confirm whether the surface roughness of the steel material was properly measured.

In addition, the test method for measuring the joint strength of the co-curing joint has not yet been determined. Therefore, the tensile tester was made by making a test specimen according to ASTM D3165, which is a regulation on the joint test specimen manufactured by the bonding method using an adhesive. Using, joint strength was measured. (Bond strength [Pa] = maximum load [N] / cross-sectional area of the joint joint [m ² ])

As an embodiment of the present invention, a method for improving the bonding strength of a co-cured joint using a carbon fiber-epoxy composite material and a steel material, comprising: (A) a method of determining the surface roughness of the joint surface of steel materials, (B) Consider the method of determining the internal pressure, and (C) the method of determining the orientation angle of the fibers contained in the composite material.

Surface roughness of the joining surface of the steel material (A) can be determined as follows.

Since the co-curing joint has the surface roughness of the steel material due to the manufacturing process, the surface roughness of the steel material becomes the surface roughness of the composite material and at the same time determines the interface contact area between the two materials.

It is known that the bonding strength increases as the contact area increases, so that the surface roughness of 0.2 μm, 0.3 μm, 0.7 μm, 1.2 μm, 1.7 μm and the surface roughness can be evaluated to be very high. Seven specimens were fabricated up to the knurled surface.

At this time, the surface of the steel material can be polished using sandpaper, the relationship between the type of sandpaper selected for the surface treatment and the surface roughness of the steel material has a dense mesh as shown in the graph of FIG. Sandpaper can obtain smoother surface finish.

Bonding strength test results of the co-cured joint manufactured according to the surface roughness of the steel material as shown in the graph of FIG.

As shown in Figure 4, in order to improve the bonding strength of the outer overlap co-curing joint using a carbon fiber-epoxy composite material and a steel material, the surface roughness of the steel material can be determined by experimenting with the test specimen from low to high, but In general, it was found that the best bonding strength was shown at around 1.2㎛ surface roughness.

Therefore, the surface of the steel material is preferably polished to a surface roughness of 0.2 to 1.7 mu m, preferably to 1.2 mu m.

The method of determining the internal pressure in the (B) bonding step is as follows.

The test specimen was fabricated by applying 0.7MPa of pressure suggested for the curing process of the composite material, and the bond strength was measured. The results are as shown in the graph of FIG.

As shown in Figure 5, as the betting pressure increases, the bonding strength is improved, but the increase is generally reduced.

Therefore, it is better to increase the internal pressure to improve the joint strength of the external overlapping joint hardening joint using carbon fiber-epoxy composite and steel material, but it can be manufactured only at higher than the internal pressure given by the curing condition of the composite material. As shown, the bet pressure applied to the composite material and the steel material is limited to the range of 0.4 to 1.0 Mpa, but is preferably applied at a pressure of 0.7 MPa.

The method of determining the orientation angle of the fibers contained in the (C) composite material is as follows.

Since steel is an isotropic material, physical properties are already determined at the material selection stage. However, in the case of composite materials, physical properties vary depending on the orientation method of fibers included in the composite material.

Therefore, by controlling the stacking angle of the composite material it is possible to control the difference in physical properties with the steel material.

In particular, since the difference in stiffness between materials is an important factor in determining the bonding strength, the determination of the orientation angle of the fibers contained in the composite material is very important, and the experimental results for the orientation angle are shown in the graph of FIG. 6.

If the fiber orientation angle in the composite material is more than 60 degrees, the in-plane strength of the composite material is very low, resulting in lower results than the bonding strength. Therefore, the fiber orientation angle should be adjusted within 45 degrees to prevent in-plane fracture of the composite material. .

Once within 45 degrees, the bond strength increases as the orientation angle increases, but the increase decreases. Therefore, it is contained in the composite material to improve the bond strength of the overlapping joint hardening joint using carbon fiber-epoxy composite material and steel material. By determining the angle at which in-plane breakage occurs by adjusting the orientation angle of the fibers, and determining below that, the best bonding strength can be obtained.

Therefore, the orientation angle of the fibers contained in the composite material is preferably 20 to 60 degrees, more preferably 45 degrees.

On the other hand, the method according to the present invention can be used even if the material is different in the co-cure joint using a fiber-reinforced plastic composite material and a metal material, for example, a co-cured joint using a glass fiber-epoxy composite material and an aluminum material Even in the case of designing, according to the above-described method, excellent bonding strength can be obtained.

As described above, according to the simultaneous hardened bonding method between the carbon fiber-epoxy composite material and the steel material according to the present invention, an adhesive joint using an existing adhesive using a carbon fiber-epoxy composite material and a steel material having excellent mechanical performance By presenting a design method to improve the joint strength of the joint hardening joint structure by using the simultaneous hardening method, which is simpler in manufacturing process, the application possibility of the composite material using carbon fiber, which is increasing in the application to automobile structures It can provide a magnified effect.

In addition, on the basis of the present invention it can provide a condition to further develop a co-cured bonding method of a composite material other than a carbon fiber reinforced composite material and a metal material including an aluminum material.

In addition, it is possible to improve the bonding strength of the joint joint produced by the co-cured joint method of the present invention by reducing the manufacturing process time and manufacturing cost by making the existing joint process of the structure using the composite material much simpler.

Claims (5)

delete Polishing the surface of the steel material with sandpaper and then wiping it with acetone; Stacking an uncured carbon fiber-epoxy composite on the steel material; Pre-bonding the joint surface of the carbon fiber-epoxy composite material with the steel material with a finger to pre-bond the joint surface; Covering the upper and lower surfaces of the temporarily bonded carbon fiber-epoxy composite material and steel material with a Teflon film and simultaneously placing a resin blocking Teflon dam at a rim position; Vacuum packing the carbon fiber-epoxy composite material and the steel material in a state where a teflon film and a resin blocking teflon dam are disposed; Placing the vacuum packed carbon fiber-epoxy composite and steel material together with the Teflon film and the Teflon dam for blocking the resin into an autoclave, and connecting the pressure hose to cure under pressure; Bonding the resin contained in the carbon fiber-epoxy composite material to the surface of the steel material by hardening, thereby bonding the carbon fiber-epoxy composite material and the steel material; In the co-cured bonding method between a carbon fiber-epoxy composite material and a steel material, After the bonding process, the step of reducing the stress concentration by processing the sharp edges of the joint surface is further progressed, the simultaneous curing bonding method between the carbon fiber-epoxy composite material and the steel material. Polishing the surface of the steel material with sandpaper and then wiping it with acetone; Stacking an uncured carbon fiber-epoxy composite on the steel material; Pre-bonding the joint surface of the carbon fiber-epoxy composite material with the steel material with a finger to pre-bond the joint surface; Covering the upper and lower surfaces of the temporarily bonded carbon fiber-epoxy composite material and steel material with a Teflon film and simultaneously placing a resin blocking Teflon dam at a rim position; Vacuum packing the carbon fiber-epoxy composite material and the steel material in a state where a teflon film and a resin blocking teflon dam are disposed; Placing the vacuum packed carbon fiber-epoxy composite and steel material together with the Teflon film and the Teflon dam for blocking the resin into an autoclave, and connecting the pressure hose to cure under pressure; Bonding the resin contained in the carbon fiber-epoxy composite material to the surface of the steel material by hardening, thereby bonding the carbon fiber-epoxy composite material and the steel material; In the co-cured bonding method between a carbon fiber-epoxy composite material and a steel material, And the surface of the steel material is polished to a surface roughness of 0.2 to 1.7 mu m. Polishing the surface of the steel material with sandpaper and then wiping it with acetone; Stacking an uncured carbon fiber-epoxy composite on the steel material; Pre-bonding the joint surface of the carbon fiber-epoxy composite material with the steel material with a finger to pre-bond the joint surface; Covering the upper and lower surfaces of the temporarily bonded carbon fiber-epoxy composite material and steel material with a Teflon film and simultaneously placing a resin blocking Teflon dam at a rim position; Vacuum packing the carbon fiber-epoxy composite material and the steel material in a state where a teflon film and a resin blocking teflon dam are disposed; Placing the vacuum packed carbon fiber-epoxy composite and steel material together with the Teflon film and the Teflon dam for blocking the resin into an autoclave, and connecting the pressure hose to cure under pressure; Bonding the resin contained in the carbon fiber-epoxy composite material to the surface of the steel material by hardening, thereby bonding the carbon fiber-epoxy composite material and the steel material; In the co-cured bonding method between a carbon fiber-epoxy composite material and a steel material, And the pressure applied to the carbon fiber-epoxy composite material and the steel material is 0.4 to 1.0 Mpa. Polishing the surface of the steel material with sandpaper and then wiping it with acetone; Stacking an uncured carbon fiber-epoxy composite on the steel material; Pre-bonding the joint surface of the carbon fiber-epoxy composite material with the steel material with a finger to pre-bond the joint surface; Covering the upper and lower surfaces of the temporarily bonded carbon fiber-epoxy composite material and steel material with a Teflon film and simultaneously placing a resin blocking Teflon dam at a rim position; Vacuum packing the carbon fiber-epoxy composite material and the steel material in a state where a teflon film and a resin blocking teflon dam are disposed; Placing the vacuum packed carbon fiber-epoxy composite and steel material together with the Teflon film and the Teflon dam for blocking the resin into an autoclave, and connecting the pressure hose to cure under pressure; Bonding the resin contained in the carbon fiber-epoxy composite material to the surface of the steel material by hardening, thereby bonding the carbon fiber-epoxy composite material and the steel material; In the co-cured bonding method between a carbon fiber-epoxy composite material and a steel material, The orientation angle of the fibers contained in the carbon fiber-epoxy composite material is 20 to 60 degrees in the plane parallel to the steel material, characterized in that the carbon fiber-epoxy composite material and the steel material co-cured bonding method.

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