KR102810167B1 - Manufacturing method of composite materials - Google Patents

Abstract

An invention is disclosed relating to a method for manufacturing a composite frame. The method for manufacturing a composite frame according to the present invention is characterized by including: a core laminating step in which composite parts are laminated on the lower and upper sides of a plastic foam, respectively; a pressing step in which air bubbles are removed between the plastic foam and the composite part; and a curing step in which the pressed plastic foam and the composite part are heated and then cured to form a frame part mounted on a side sill of a vehicle body.

Description

MANUFACTURING METHOD OF COMPOSITE MATERIALS

The present invention relates to a method for manufacturing a composite frame, and more specifically, to a method for manufacturing a composite frame capable of reducing the weight of a frame, such as a battery case for an electric vehicle, by using a composite.

Recently, the electric vehicle market has been growing rapidly due to emission and fuel efficiency regulations and mandatory sales of zero-emission vehicles in each country.

While electric vehicles require weight reduction to improve driving efficiency,

Battery deformation and fires due to crashes have led to reduced passenger safety and calls for expensive battery replacement.

The battery case frame is a battery case side component and is a key structural safety component that protects the battery cell from the external environment and physical impact. The existing battery case frame is mainly made of high-strength steel and high-strength aluminum, but there is a limit to simultaneously implementing the conflicting performances required for electric vehicles, such as weight reduction and collision safety. Therefore, there is a need to improve this.

The background technology of the present invention is disclosed in Korean Patent Publication No. 10-2022-0068646 (published on May 26, 2022, title of the invention: Manufacturing method of battery case for electric vehicle).

The present invention was created to solve the above problems, and the purpose of the present invention is to provide a method for manufacturing a composite frame that can reduce the weight of a frame such as a battery case of an electric vehicle by using a composite material.

A method for manufacturing a composite frame according to the present invention comprises: a core lamination step in which composite parts are laminated on the lower and upper sides of a plastic foam, respectively; a pressing step in which air bubbles are removed between the plastic foam and the composite part; and a curing step in which the pressed plastic foam and the composite part are heated and then cured to form a frame part to be mounted on a side sill of a vehicle body.

In the curing step of the present invention, the plastic foam and the composite part are placed between the lower mold and the upper mold and pressurized at a set pressure to form the frame part.

In the present invention, the curing step includes a first curing step of heating the plastic foam and the composite part arranged between the lower mold and the upper mold at a set temperature and a set time of a first condition; and a second curing step of heating the plastic foam and the composite part at a set temperature and a set time of a second condition.

In the first curing step of the present invention, the plastic foam and the composite part are heated at a first condition set temperature of 80°C and a first condition set time of 20 minutes.

In the second curing step of the present invention, the plastic foam and the composite part are heated at a temperature set to 120°C for a time set to 90 minutes under the second condition.

In the present invention, the lower mold and the upper mold press-process the plastic foam and the composite part at a set pressure of 4 bar.

In the present invention, the pressing step places the plastic foam and the composite part in a vacuum bag, and vacuums the vacuum bag to remove air bubbles between the plastic foam and the composite part.

In the present invention, the composite part is formed of carbon fiber reinforced plastic (CFRP).

In the present invention, the plastic foam is formed by including one of polyvinyl chloride (PVC), styrene acrylonitrile copolymer (SAN), and polyethylene terephthalate (PET).

According to the method for manufacturing a composite frame according to the present invention, a battery case frame part of an electric vehicle can be manufactured using a plastic foam and a composite part, thereby realizing weight reduction and collision stability of the vehicle.

In addition, according to the present invention, mass production is possible through simplification of the manufacturing process, and price competitiveness can be improved.

FIG. 1 is a flow chart schematically showing a method for manufacturing a composite frame according to one embodiment of the present invention.
FIG. 2 is a flow chart specifically showing a curing step in a method for manufacturing a composite frame according to one embodiment of the present invention.
FIG. 3 is a perspective view schematically showing a composite part being laminated on the upper and lower sides of a plastic foam in a method for manufacturing a composite frame according to one embodiment of the present invention.
FIG. 4 is a perspective view schematically illustrating compression of a plastic foam and a composite part in a method for manufacturing a composite frame according to one embodiment of the present invention.
FIG. 5 is a perspective view schematically illustrating the curing of a plastic foam and a composite part in a method for manufacturing a composite frame according to one embodiment of the present invention.
Figure 6 is a cross-sectional view schematically showing AA of Figure 5.
FIG. 7 is an exploded perspective view schematically illustrating the curing of a plastic foam and a composite part in a method for manufacturing a composite frame according to one embodiment of the present invention.
Fig. 8 is a cross-sectional view schematically showing BB of Fig. 7.
FIG. 9 is a graph comparing the weight of a frame part manufactured by a composite frame manufacturing method according to one embodiment of the present invention and steel.
Figure 10 is a graph comparing the rigidity of a frame part manufactured by a composite frame manufacturing method according to one embodiment of the present invention and CFRP.
FIG. 11 is a graph comparing the maximum stiffness test results of a frame part manufactured by a composite frame manufacturing method according to one embodiment of the present invention and CFRP.
FIG. 12 is a graph comparing the cost of a frame part manufactured by a composite frame manufacturing method according to one embodiment of the present invention and CFRP.

Hereinafter, an embodiment of a method for manufacturing a composite frame according to the present invention will be described with reference to the attached drawings. In this process, the thickness of lines and the size of components illustrated in the drawings may be exaggerated for the sake of clarity and convenience of explanation.

In addition, the terms described below are terms defined in consideration of their functions in the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, the definitions of these terms should be made based on the contents throughout this specification.

FIG. 1 is a flow chart schematically showing a method for manufacturing a composite frame according to an embodiment of the present invention, FIG. 2 is a flow chart specifically showing a curing step in a method for manufacturing a composite frame according to an embodiment of the present invention, FIG. 3 is a perspective view schematically showing that a composite part is laminated on the upper and lower sides of a plastic foam in a method for manufacturing a composite frame according to an embodiment of the present invention, FIG. 4 is a perspective view schematically showing compression of a plastic foam and a composite part in a method for manufacturing a composite frame according to an embodiment of the present invention, FIG. 5 is a perspective view schematically showing curing of a plastic foam and a composite part in a method for manufacturing a composite frame according to an embodiment of the present invention, FIG. 6 is a cross-sectional view schematically showing A-A of FIG. 5, FIG. 7 is an exploded perspective view schematically showing curing of a plastic foam and a composite part in a method for manufacturing a composite frame according to an embodiment of the present invention, FIG. 8 is a cross-sectional view schematically showing B-B of FIG. 7, FIG. 9 is a graph comparing the weight of a frame part and steel manufactured by a method for manufacturing a composite frame according to an embodiment of the present invention, and FIG. 10 is a graph comparing the stiffness of a frame part manufactured by a composite frame manufacturing method according to one embodiment of the present invention with CFRP, FIG. 11 is a graph comparing the maximum stiffness test of a frame part manufactured by a composite frame manufacturing method according to one embodiment of the present invention with CFRP, and FIG. 12 is a graph comparing the cost of a frame part manufactured by a composite frame manufacturing method according to one embodiment of the present invention with CFRP.

Referring to FIGS. 1 and 2, a method for manufacturing a composite frame according to one embodiment of the present invention includes a core lamination step (S10), a pressing step (S20), and a curing step (S30).

Referring to FIG. 3, in the core lamination step (S10), a composite part (200) is laminated on the lower and upper sides of the plastic foam (100), respectively. The plastic foam (100) and the composite part (200) are joined by bonding.

The plastic foam (100) is made of at least one of polyvinyl chloride (PVC), styrene acrylonitrile copolymer (SAN), and polyethylene terephthalate (PET).

Polyvinyl chloride (PVC) is a type of thermoplastic plastic with vinyl chloride as its main component, and has excellent durability. Styrene acrylic nitrile (SAN) is a copolymer made by polymerizing styrene, an aromatic hydrocarbon, and acrylonitrile, an unsaturated nitrile, and has excellent transparency, heat deformation, chemical resistance, and gloss. Polyethylene terephthalate (PET) is a saturated polyester obtained by condensation polymerization of terephthalic acid and ethylene glycol, and has excellent heat resistance, rigidity, electrical properties, and oil resistance.

The plastic foam (100) composed of the above-described composition has the properties of high chemical resistance and high productivity, and can absorb external impacts as well as high tensile strength.

The composite part (200) is laminated on the lower and upper sides of the plastic foam (100), respectively. The composite part (200) is made of carbon fiber reinforced plastic (CFRP).

Carbon fiber reinforced plastic (CFRP) is a plastic composite material that uses carbon fiber (CF) as a reinforcing material. Carbon fiber reinforced plastic has a specific strength that is six times that of steel and twice that of GFRP (glass fiber reinforced plastic), and a specific elastic modulus that is three times that of steel and four times that of GFRP. In addition, carbon fiber reinforced plastic has excellent fatigue properties as well as static strength, and has excellent friction and wear resistance.

In the present invention, the frame part (300) is composed of a plastic foam (100) and a composite part (200) having the above-described configuration. The frame part (300) is mounted on a side sill of a vehicle body. The side sill is a beam-shaped member installed in the longitudinal direction of the vehicle body at the lower side of the vehicle body. The frame part (300) according to the present invention is mounted on a side sill of a vehicle body and is used as a side structure of a battery case of an electric vehicle.

The frame part (300) is made of plastic foam (100) and a composite part (200), and has lower density and higher bending rigidity than steel or CFRP of the same mass, so it can safely protect the battery of an electric vehicle.

The pressing step (S20) removes air bubbles between the plastic foam (100) and the composite part (200). Referring to FIG. 4, the pressing step (S20) places the laminated plastic foam (100) and the composite part (200) into a vacuum bag (10). As the vacuum device (15) sucks in the internal air of the vacuum bag (10), the interior of the vacuum bag (10) is vacuumed to remove air bubbles between the plastic foam (100) and the composite part (200). The vacuum device (15) discharges the internal air of the vacuum bag (10) to the outside of the vacuum bag (10). In this process, the adhesion between the plastic foam (100) and the composite part (200) is improved.

Referring to FIGS. 5 to 8, the curing step (S30) heats and then cures the compressed plastic foam (100) and composite part (200) to form a frame part (300).

In the curing step (S30), the plastic foam (100) and the composite part (200) are placed between the lower mold (20) and the upper mold (30) and pressurized at a set pressure to form a frame part (300).

In the curing step (S30), the plastic foam (100) and the composite part (200) may be placed between the lower mold (20) and the upper mold (30) while being inserted into the vacuum bag (10). Alternatively, in the curing step (S30), the plastic foam (100) and the composite part (200) may be placed between the lower mold (20) and the upper mold (30) while being discharged from the vacuum bag (10).

The curing step (S30) includes a first curing step (S31) and a second curing step (S33). The first curing step (S31) heats the plastic foam (100) and the composite part (200) placed between the lower mold (20) and the upper mold (30) at a set temperature and a set time of the first condition, and pressurizes them at a set pressure. The first curing step (S31) heats the plastic foam (100) and the composite part (200) at a set temperature of the first condition of 80°C and a set time of the first condition of 20 minutes.

The second curing step (S33) heats the plastic foam (100) and the composite part (200) to the set temperature and time of the second condition, and pressurizes them to the set pressure. The second curing step (S33) heats the plastic foam (100) and the composite part (200) to the set temperature of the second condition at 120°C and the set time of the second condition at 90 minutes.

A heater (not shown) capable of heating the plastic foam (100) and the composite part (200) to the above-described set temperature is installed in at least one of the lower mold (20) and the upper mold (30). A plurality of heaters are installed in the lower mold (20) or the upper mold (30) so as to heat the entirety of the plastic foam (100) and the composite part (200).

In the present invention, the curing step (S30) is composed of a two-step process of a first curing step (S31) under a first condition and a second curing step (S33) under a second condition. Since the plastic foam (100) made of polyvinyl chloride or the like has a property of having the lowest viscosity at 80°C, the curing step (S30) with different temperatures and times is composed of a two-step process of a first curing step (S31) and a second curing step (S33), thereby improving the adhesion between the plastic foam (100) and the composite part (200).

In the hardening step (S30), the lower mold (20) and the upper mold (30) press-process the plastic foam (100) and the composite part (200) at a set pressure of 4 bar. The lower mold (20) and the upper mold (30) press-process the plastic foam (100) and the composite part (200) at the set pressure under the above conditions of temperature and time to form an integrated frame part (300).

Referring to FIG. 9, the weight of a frame part (300) manufactured by a composite frame manufacturing method according to one embodiment of the present invention is compared with that of a steel material.

In the present invention, the frame part (300) formed by the plastic foam (100) and the composite part (200) is about 59% lighter in weight than steel of the same length. Therefore, since the frame part (300) manufactured by the present invention is lighter than steel material, it is possible to provide a lightweight material to a vehicle, thereby improving fuel efficiency by reducing the weight of the vehicle.

Referring to FIGS. 10 and 11, the stiffness of a frame part (300) manufactured by a composite frame manufacturing method according to one embodiment of the present invention is compared with that of a CFRP material. In FIG. 11, (a) shows the stiffness of CFRP, and (b) shows the stiffness of the frame part (300).

In the present invention, the frame part (300) formed by the plastic foam (100) and the composite part (200) has a rigidity improved by about 87% compared to CFRP material of the same length and weight. When comparing the maximum rigidity, the maximum rigidity of CFRP is 2391.8N, while the maximum rigidity of the frame part (300) is 19561N.

Therefore, since the frame part (300) manufactured by the present invention has superior rigidity compared to CFRP material, it can secure stability by protecting the battery placed in the vehicle from side collisions, etc.

Referring to FIG. 12, the cost of a frame manufactured by a composite frame manufacturing method according to one embodiment of the present invention is compared with that of CFRP.

In the present invention, the frame part (300) formed by the plastic foam (100) and the composite part (200) has a cost and rigidity reduced by about 41% compared to CFRP material of the same length and weight. Therefore, the frame part (300) manufactured by the present invention can have a reduced production cost compared to CFRP material, thereby improving productivity.

According to the method for manufacturing a composite frame according to the present invention, a battery case frame part (300) of an electric vehicle can be manufactured using a plastic foam (100) and a composite part (200), thereby realizing weight reduction and collision stability of the vehicle.

In addition, according to the present invention, mass production is possible through simplification of the manufacturing process, and price competitiveness can be improved.

Although the present invention has been described with reference to one embodiment illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the claims below.

10: Vacuum bag 15: Vacuum machine
20: Lower mold 30: Upper mold
100: Plastic Foam 200: Composite Material
300: Frame section

Claims (9)

A core lamination step in which composite parts are laminated on the lower and upper sides of the plastic foam respectively;
A pressing step for removing air bubbles between the plastic foam and the composite part; and
It includes a curing step of heating the compressed plastic foam and the composite part and then curing them to form a frame part to be mounted on the side sill of the vehicle body.
The above curing step is performed by placing the plastic foam and the composite part between the lower mold and the upper mold and pressurizing them at a set pressure to form them into the frame part.
The above hardening step is,
A first curing step of heating the plastic foam and the composite part placed between the lower mold and the upper mold at a set temperature and set time of the first condition; and
Including a second curing step of heating the plastic foam and the composite part at a set temperature and set time of a second condition,
The above first curing step heats the plastic foam and the composite part by setting the temperature of the first condition to 80°C and setting the time of the first condition to 20 minutes.
The second curing step heats the plastic foam and the composite part by setting the temperature of the second condition to 120°C and the time of the second condition to 90 minutes.
A heater is installed in at least one of the lower mold and the upper mold to heat the plastic foam and the composite part to a set temperature of the first condition and a set temperature of the second condition.
A method for manufacturing a composite frame, characterized in that a plurality of heaters are installed in the lower mold or the upper mold.
delete delete delete delete In the first paragraph,
A method for manufacturing a composite frame, characterized in that the lower mold and the upper mold perform press processing of the plastic foam and the composite part at a set pressure of 4 bar.
In the first paragraph,
A method for manufacturing a composite frame, characterized in that the pressing step includes placing the plastic foam and the composite part in a vacuum bag and vacuuming the vacuum bag to remove air bubbles between the plastic foam and the composite part.
In the first paragraph,
A method for manufacturing a composite frame, characterized in that the composite part comprises carbon fiber reinforced plastic (CFRP).
In the first paragraph,
A method for manufacturing a composite frame, characterized in that the plastic foam comprises one of polyvinyl chloride (PVC), styrene acrylonitrile copolymer (SAN), and polyethylene terephthalate (PET).

Images