KR20220001413A - Forming method of carbon fiber reinforced plastic - Google Patents

Abstract

A carbon fiber reinforced plastic shaping method according to one embodiment of the present invention comprises: a step of laminating two or more prepreg sheets to form a prepreg laminate; a step of disposing a mold, a prepreg laminate, and a shaping pad in a shaping device; a heat treatment step of applying heat to the prepreg laminate; a step of forming a sub-vacuum state in the shaping device to attach the prepreg laminate to the mold; and a step of curing the prepreg laminate to produce a shaped article, wherein tension having a predetermined magnitude is formed at the shaping pad. According to the present invention, productivity of the shaped article can be improved.

Description

Carbon fiber reinforced plastic molding method {FORMING METHOD OF CARBON FIBER REINFORCED PLASTIC}

A carbon fiber reinforced plastic molding method is provided.

Carbon Fiber Reinforced Plastic (CFRP) using carbon fiber has more than 5 times superior strength than steel, lightweight properties lighter than silicon, and durability that can be maintained up to about 1300 °C without being easily oxidized in the external environment , and is a material attracting attention due to its excellent elasticity.

Molded articles made of CFRP are often manufactured by molding and then curing prepreg (Preimpregnated Materials: Prepreg).

Here, the prepreg is a sheet-shaped product in which a resin is pre-impregnated into a reinforced fiber and can be viewed as a kind of intermediate material. Prepregs are widely used in many other industries, such as aircraft, automobile parts, sports, leisure equipment, and boats, where high strength and strong elasticity are required.

The manufacturing method of a general CFRP molded article may be made, for example, by a carbon fiber infusion method or a prepreg hand layer method.

The CFRP molded product manufacturing method by the carbon fiber infusion method includes the steps of cutting the carbon fiber fabric according to a predetermined shape, and forming one (or one layer) or more cut carbon fiber fabric into a mold of a predetermined shape. ), a step of placing a resin film on the carbon fiber fabric, an infusion step of impregnating the carbon fiber fabric as the resin film melts and descends while forming a vacuum state of a predetermined condition, through heating and curing to form a molded article, demolding the molded article, and the like. Here, in order to perform the infusion step, steps such as a breather arrangement, a fill fly arrangement, a vacuum bag installation, and an infusion line installation may be performed.

The CFRP molded product manufacturing method by the prepreg hand layer method comprises the steps of cutting a carbon fiber prepreg sheet according to a predetermined shape, and cutting one (or one layer) or more prepreg sheets with a predetermined shape into a mold (mold), the step of pressing the resin and carbon fiber contained in the prepreg while forming a vacuum state of a predetermined condition, the step of curing through heating to form a molded article, the step of demolding the molded article, etc. include Here, in order to perform vacuum curing, steps such as a breather arrangement, a peel fly arrangement, a vacuum bag installation, and an infusion line installation may be performed.

In the case of these existing CFRP molded product manufacturing methods, they are used in close contact with a breather, carbon fiber fabric laminate or prepreg sheet laminate that absorbs resin flowing out due to heating and vacuum formation or flows out through a hole. Subsidiary materials such as peel ply must be used, and these subsidiary materials are used and disposed of once, thereby greatly increasing the manufacturing cost of the molded product and generating a large amount of waste. In addition, the existing methods require a long time of 6 hours or more to manufacture a molded article, and have a high dependence on manual labor, so that the molded article production time is long, mass production is difficult, and the manufacturing cost may increase. In addition, in the case of the existing CFRP molded product manufacturing methods, since the CFRP sheet must be cut according to the mold shape corresponding to the shape (form) of the molded product (finished product), the cutting takes a very long time, and the manufacturing cost may increase can

Carbon fiber reinforced plastic molding method according to an embodiment of the present invention is to improve the productivity of the molded product.

Carbon fiber-reinforced plastic molding method according to an embodiment of the present invention is to shorten the production time of the molded article.

Carbon fiber reinforced plastic molding method according to an embodiment of the present invention is to reduce the dependence on manual work.

Carbon fiber reinforced plastic molding method according to an embodiment of the present invention is to reduce the cost of manufacturing a molded article.

Carbon fiber reinforced plastic molding method according to an embodiment of the present invention is for mass production of molded articles.

Carbon fiber reinforced plastic molding method according to an embodiment of the present invention is to improve the high strength characteristics and light weight characteristics of the molded article.

Carbon fiber reinforced plastic molding method according to an embodiment of the present invention is to improve the corner formability of the molded article.

In addition to the above problems, the embodiment according to the present invention may be used to achieve other problems not specifically mentioned.

The carbon fiber reinforced plastic molding method according to an embodiment of the present invention comprises the steps of laminating two or more prepreg sheets to form a prepreg laminate, disposing a mold, a prepreg laminate and a molding pad in a molding apparatus , a heat treatment step of applying heat to the prepreg laminate, forming a sub-vacuum state in a molding apparatus to attach the prepreg laminate to a mold, and curing the prepreg laminate to produce a molded article, comprising the steps of: A tension having a predetermined magnitude is formed on the pad.

In the step of forming the prepreg laminate, the two or more prepreg sheets may include a first prepreg sheet and a second prepreg sheet adjacent to each other, and one surface of the first prepreg sheet is a second prepreg sheet may be in contact with a surface facing one surface of the first prepreg sheet.

Each of the two or more prepreg sheets may include a thermosetting resin, and the two or more prepreg sheets may be compressed and adhered with a force of 40 to 60 kgf.

The molding pad may include silicon (Si), and the thickness of the molding pad may be 1 to 5 mm.

The tensile strength of the forming pad may be at least ^{50 kf/cm 2 at 25°C.}

As the magnitude of the tension of the molding pad increases, the edge bending strength of the molded article may increase.

As the magnitude of the tension of the molding pad increases, the magnitude of the surface roughness may decrease.

The forming pad may include a hole having a diameter of 0.2 cm or less in the central region.

The heat treatment step may be performed at 120 to 140 °C for 5 to 30 minutes.

In the heat treatment step, the value of the tensile strength/tensile modulus of the prepreg laminate may become small, and the value of the flexural strength/flexural modulus of the prepreg laminate may become small.

In the step of attaching the prepreg laminate to the mold, the pressure in the sub-vacuum state is 0.05 to 0.08 MPa, and pressing may be performed for 30 minutes to 1 hour.

The carbon fiber reinforced plastic molding method according to an embodiment of the present invention can improve molded product productivity, shorten molded product production time, reduce dependence on manual labor, reduce molded product manufacturing cost, and It can be mass-produced, can improve the high strength and light weight properties of the molded article, and can improve the corner formability of the molded article.

1 is a view schematically illustrating a carbon fiber reinforced plastic molding method according to an embodiment.
2A to 2C are views schematically illustrating a carbon fiber reinforced plastic molding method according to an embodiment.
3 is a graph showing the relationship between the tensile strength of the molding pad and the edge formability of the molded article according to the thickness of the molding pad.
4 is a graph showing the relationship between the tensile strength of the molding pad and the edge bending strength of the molded article according to the thickness of the molding pad.
5 is a graph showing the relationship between the tensile strength of the forming pad and the number of reuses according to the thickness of the forming pad.

With reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are used for the same or similar components throughout the specification. In addition, in the case of a well-known known technology, a detailed description thereof will be omitted.

In order to clearly express various layers and regions in the drawings, the thicknesses are enlarged. When a part, such as a layer, film, region, plate, etc., is “on” another part, it includes not only cases where it is “directly on” another part, but also cases where there is another part in between. On the other hand, when a part is said to be "just above" another part, it means that there is no other part in the middle. Conversely, when a part, such as a layer, film, region, or plate, is “under” another part, it includes not only cases where it is “directly under” another part, but also cases where there is another part in between. On the other hand, when a part is said to be "just below" another part, it means that there is no other part in the middle.

Throughout the specification, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

1 is a view schematically illustrating a carbon fiber reinforced plastic (CFRP) molding method according to an embodiment, and FIGS. 2A to 2C are views schematically illustrating a carbon fiber reinforced plastic molding method according to an embodiment.

1 and 2A to 2C, the carbon fiber reinforced plastic molding method is largely a prepreg cutting step (S110), forming a prepreg laminate (S120), arranging step (S130), heat treatment step (S140) ), attaching the prepreg laminate to the mold (S150), and manufacturing a molded article (S160).

Here, the molded article means a structure having a specific shape or form made of carbon fiber reinforced plastic.

First, the prepreg cutting step (S110) is performed.

The prepreg cutting step ( S110 ) is a step of cutting a prepreg sheet into a predetermined shape. The cutting shape may be different according to the shape of the final molded product.

The prepreg sheet may refer to a sheet-shaped intermediate product in which a thermosetting resin is pre-impregnated into carbon fiber, which is a reinforced fiber.

In the case of the cutting method according to the conventional CFRP molding method (carbon fiber infusion method or prepreg hand layer method), the cut size and shape are different depending on the mold. Difficulty is required and can take a relatively long time to work. In addition, when cutting using CNC, if there are bends or a specific shape depending on the mold, it may not be easy to cut several sheets by overlapping, cutting may require a long time, and relatively high costs are incurred. .

On the other hand, according to the CFRP molding method according to the embodiment, it is possible to collectively cut to a specific size (size), for example, the prepreg can be cut in a rectangular shape of a specific size. Here, the specific size is about 10 in all directions of the plane except the thickness direction (thickness direction of the prepreg sheet) rather than the size when the CFRP molded product (product) to be produced is spread flat (if the molded product is flat, it is the size of the flat plate). cm to about 20 cm tall.

If the difference between the size of the CFRP molded product when it is flattened and the size of the prepreg sheet is less than 10 cm, when the prepreg is subsequently attached to the mold through a vacuum pump, movement of the prepreg may occur, which may cause the prepreg to adhere to the mold Unfinished sides may exist, and problems may arise in the quality of the products produced. If the difference between the size of the CFRP molded product and the size of the prepreg seat when flattened is greater than about 20 cm, the prepreg seat may be sucked into the vacuum valve or perforation, causing damage to equipment and equipment failure.

In the cutting method according to the embodiment, one prepreg sheet is cut with a cutting equipment, or two or more prepreg sheets are laminated, and then the cutting time can be greatly reduced, and the manufacturing cost can be reduced because it is possible to collectively cut with the cutting equipment. can be reduced Accordingly, if the cutting method according to the embodiment is used, production efficiency may be greatly increased when mass production and automation are performed. As can be seen in Table 1 below, the cutting time of one prepreg sheet can be reduced to about 2 minutes or less through the molding method according to the embodiment, and the cutting time of the six prepreg laminated body can be shortened to about 3 minutes or less. can

For example, the cutting equipment may be a computer numerical control (CNC) equipment.

Conventional molding method Molding method according to the embodiment
(CNC) prepreg
Chapter 1 Cutting Time up to 5 minutes up to 2 minutes prepreg
Chapter 6 Cutting Time up to 30 minutes up to 3 minutes

The RPM of the cutting equipment may be about 5000 to 9000. If the RPM of the cutting equipment is less than about 5000, the cutting may not be sufficiently performed, and if the RPM of the cutting equipment is more than about 9000, the fibers included in the prepreg may become tangled during cutting.

Next, forming the prepreg laminate 130 by laminating two or more prepreg sheets (S120) is performed.

At this stage, no separate adhesive is inserted between the prepreg sheets. For example, the two or more prepreg sheets include a first prepreg sheet and a second prepreg sheet adjacent to each other, and one side of the first prepreg sheet is one side of the first prepreg sheet in the second prepreg sheet It is in contact with the surface facing the , and a separate adhesive material may not be inserted between the first prepreg sheet and the second prepreg sheet. As the prepreg sheet is laminated and compressed, the thermosetting resin contained in the prepreg sheet may perform the function of an adhesive.

After laminating two or more prepreg sheets, the prepreg laminate 130 is formed by compressing and adhering the laminated prepreg sheets using a roller. At this time, the material of the roller may include stainless steel (stainless steel) to which the thermosetting resin does not stick.

Two or more sheets of prepreg may be adhered by compression, for example, with a force of about 30 kgf to about 50 kgf. When the compressive force is less than about 30 kgf, spaces may occur between the prepreg laminates, which may deteriorate the quality of the molded article. If the compressive force exceeds about 50 kgf, entanglement of the carbon fibers contained in the prepreg sheet may occur, resulting in deterioration of the quality of the molded product, and the carbon fibers contained in the prepreg sheet may be damaged. .

Next, a disposing step (S130) of disposing the mold 120, the prepreg laminate 130, and the molding pad 140 in the molding apparatus is performed.

Here, the forming apparatus may be a vacuum platform capable of forming a vacuum state.

In the molding apparatus, the mold 120 , the prepreg laminate 130 , and the molding pad 140 may be disposed in order from the bottom, and the upper surface of the mold 120 and the lower surface of the prepreg laminate 130 . may be in contact with each other, and the upper surface of the prepreg laminate 130 may be in contact with the lower surface of the forming pad 140 . The prepreg stack 130 may cover the upper surface of the mold 120 , and the forming pad 140 may cover the prepreg stack 130 .

The mold 120 is installed on a vacuum bed 110 . The shape of the mold shown in FIGS. 2A and 2B is exemplary, and the shape or shape of the mold 120 is not limited thereto and may vary.

The prepreg laminate 130 and the molding pad 140 may be in contact with each other before being put into the molding apparatus and then put into the molding apparatus.

The size of the forming pad 140 may be larger than the size of the prepreg laminate 130 . In other words, the forming pad can be larger than the CFRP laminate in all directions of the plane except the thickness direction.

The molding pad 140 may include an elastic material, for example, a silicon (Si) material.

A predetermined magnitude of tension may be formed on the forming pad 140 . Here, the direction in which the tension is formed may be any direction in a plane perpendicular to the thickness direction of the forming pad 140 . To form this tension, a portion of the end of the forming pad may be fixed to the forming apparatus so that the forming pad 140 can be pulled in one direction away from the central region of the forming pad.

The forming process proceeds in a state in which the prepreg laminate 130 and the mold 120 are in close contact with the lower portion of the forming pad 140 in which the tension is formed. Due to the tension characteristic of the molding pad, the corner portion of the molded article may be formed more smoothly, and the surface roughness of the molded article may be lowered, thereby improving the surface characteristics of the molded article.

The tensile strength of the forming pad 140 may be greater than or equal ^{to about 50 kf/cm 2 at about 25°C.} In this range, sufficient tension may be formed in the molding pad 140 , and edge formability and surface properties of the molded article may be improved.

A predetermined amount of tension is formed on the forming pad 140 . As the magnitude of the tension formed on the molding pad 140 increases, edge bending strength of the molded article increases, thereby further improving edge formability. In addition, as the magnitude of the tension formed on the molding pad 140 increases, the magnitude of the surface roughness decreases, so that the surface characteristics of the molded article may be improved.

The molding pad 140 may include one or more holes formed in the thickness direction. For example, the forming pad 140 may include one hole in the central region. Afterwards, in the heat treatment step and the molded article forming step, a portion of the resin included in the prepreg may flow out through the hole. In this way, the forming pad 140 may perform the function of a conventional breather.

The diameter of the hole formed in the forming pad 140 may be about 0.2 cm or less. If the diameter of the hole is greater than about 0.2 cm, the forming pad may tear during the forming process.

The thickness of the forming pad 140 may be about 1 mm to about 5 mm. If the thickness of the forming pad is less than about 1 mm, there is a risk of tearing the forming pad in a sub-vacuum state, which will be described below. The laminate may not adhere properly to the mold.

Referring to FIGS. 3 and 4 , when the thickness of the forming pad 140 is about 1 to 5 mm, it can be seen that as the thickness increases, the tensile strength is lowered, so that the corner formability and the corner bending strength are also lowered. As described above, when the thickness is greater than about 5 mm, the tensile strength is not sufficient. 3 and 4, T means mm.

The fiber form of the prepreg laminate used for the measurement in FIGS. 3 and 4 is twill weave, the number of steps is 3K, it has a four-layer structure, and the resin content is about 34%. Here, K means the thickness of the fiber bundle, and the closer the fibers are, the smaller the K value.

The forming pad 140 may be reused, for example, may be reused 5 or more times. For this reason, it is possible to significantly reduce the manufacturing cost of the molded article by not using a one-time auxiliary material.

Referring to FIG. 5 , as the thickness of the forming pad 140 increases, the number of times of reuse may be reduced. In FIG. 5, T means mm. The fiber form of the prepreg laminate used in the measurement in FIG. 5 is twill weave, the number of steps is 3K, and it has a four-layer structure, and the resin content is about 34%.

Due to the molding pad 140 , it is possible to manufacture a molded article having desired physical properties without a separate auxiliary material such as a conventional breather or peel fly, thereby significantly reducing manufacturing cost compared to the related art.

In addition, when a molded article is manufactured using the molding pad 140, the number of steps is reduced, and the molded article can be completed in much less time than the time for manufacturing a conventional CFRP molded article.

The forming pad 140 may be reused, for example, may be reused 5 or more times. For this reason, it is possible to significantly reduce the manufacturing cost of the molded article by not using a one-time auxiliary material.

On the other hand, as a perforation is made in the forming pad 140, a sub-vacuum state rather than a complete vacuum state is formed in a later step, so that the size of the pressure can be minutely reduced, but this can be compensated for through the tension characteristic of the forming pad have.

Next, a heat treatment step (S140) of applying heat to the prepreg laminate 130 through a heating device (not shown) is performed.

When the prepreg laminate 130 is heated, melting occurs in some thermosetting resins, and the prepreg laminate may be densified while being compressed, thereby realizing high strength characteristics and excellent durability of a molded article in the future.

In the heat treatment step, the tensile strength/tensile modulus value, which is the ratio of the tensile strength to the tensile modulus of the prepreg laminate 130 , may be decreased, and the ratio of the bending strength to the bending modulus of the prepreg laminate 130 is The flexural strength/bending modulus value may also be small.

As the tensile strength/tensile modulus value and the flexural strength/bending modulus value of the prepreg laminate 130 decrease, the strength of the thermosetting resin decreases, thereby improving moldability and rapid molding.

Here, the tensile strength means the maximum stress that the prepreg laminate 130 can withstand during the tensile test, and the tensile coefficient means the slope of the elastic section of the stress-strain diagram obtained by the tensile test. In this specification, the tensile strength is a tensile strength testing equipment, Instron Corporation H10KS equipment was used. Bending strength means the stress just before yielding when a bending moment is applied in the bending test, and the bending coefficient means the slope of the elastic section of the stress-strain diagram obtained from the bending test.

The heat treatment step may be performed at about 120 °C to about 140 °C for about 5 minutes to about 30 minutes. When the heat treatment temperature is less than about 120 °C or the heat treatment time is less than about 5 minutes, the prepreg laminate may not be sufficiently compressed, and when the heat treatment temperature is greater than about 140 °C or the heat treatment time is more than about 30 minutes, the prepreg laminate The thermosetting resin of the sieve may be melted too much and the moldability may be deteriorated.

When the prepreg laminate 130 is heated to about 120° C., the changes in tensile strength, tensile modulus, bending strength, and bending modulus of the prepreg laminate are shown in Table 1 below. As the thermosetting resin, an epoxy resin was used. The fiber form of the prepreg laminate used for the measurement is twill weave, the number of stages is 3K, it has a four-layer structure, and the resin content is about 34%.

Temperature The tensile strength
(MPa) tensile modulus
(GPa) bending strength
(MPa) bending modulus
(GPa) 25 ℃ (room temperature) 2610 136 1650 124 120 ℃ 74 10.9 48 10.1

From Table 2, it can be seen that the tensile strength/tensile modulus value of the prepreg laminate is greatly reduced and the flexural strength/flexural modulus value is greatly reduced through the heat treatment.

When this heat treatment step is performed, the time required for attaching the prepreg laminate 130 to the mold 120 thereafter is reduced, thereby increasing the production speed of the molded article (see Table 3 below).

Sample From room temperature to the appropriate level for molding
time required to reach Time to attach to the mold A Average 30 minutes average 5 minutes B Average 30 minutes average 3 minutes C Average 30 minutes average of 10 minutes

In Table 3, Sample A has a tensile strength of 74, a tensile modulus of 10.9, a flexural strength of 48, and a flexural modulus of 10.1 (3K, twill), and Sample B has a tensile strength of 70, a tensile modulus of 9.2, a bending strength of 42, a flexural modulus of 8.9 (3K, twill), sample C tensile strength 81, tensile modulus 13.9, bending strength 55, bending modulus 14.1 (1K, twill). The fiber form of the prepreg laminate used for the measurement of samples A to C is twill weave, the number of steps is 3K, it has a four-layer structure, the resin content is about 34%, and the average time is measured through 50 repeated experiments. did.

Next, a step (S150) of attaching the prepreg laminate 130 to the mold 120 by forming a sub-vacuum state in the molding apparatus is performed.

In this step, the sub-vacuum pressure is about 0.05 to about 0.08 MPa, and pressurization may be performed at about 120° C. to about 140° C. for 30 minutes to 1 hour. When the pressure is less than about 0.05 MPa, the heated laminate 130 and the mold 120 may not be properly attached, and when the pressure is higher than 0.08 MPa, the tensile strength/modulus and the flexural strength/modulus are lowered in the prepreg Problems such as twisting of the fibers or the generation of spaces between fibers may occur.

A sub-vacuum state may be formed by inhaling air from the lower side of the prepreg laminate 130 using a vacuum pump. This sub-vacuum state may mean a state in which a complete vacuum state is not achieved due to the perforation of the forming pad 140 . A complete vacuum cannot be achieved in the vicinity of the hall because it is ventilated to the outside.

In the case of the conventional molding method, a lot of manual work is required in the process of attaching the unheated prepreg to the mold, and it may take a lot of time.

On the other hand, in the case of the molding method according to the embodiment, by attaching the mold in a sub-vacuum state, the laminate 130 made of a plurality of prepreg sheets can be easily and quickly adhered to and attached to the mold 120 .

In this step, the compactness of the laminate 130 may be further improved due to the tension characteristics of the forming pad 140 , and the corner formability may be greatly improved. In addition, by enabling the completion of the molded product using the molding pad 140, it is possible to greatly shorten the production time, productivity can be greatly improved.

Next, the step ( S160 ) of manufacturing the molded article 130 ′ by curing the prepreg laminate 130 is performed.

Curing can be carried out slowly at room temperature by opening the molding apparatus. Through such an annealing curing method, the compactness of the molded article 130 ′ may be improved, and the surface properties may also be improved.

After the curing process, the molded article 130 ′ may be manufactured by demolding (see FIG. 2C ).

The molded article manufactured by the carbon fiber reinforced plastic molding method according to the embodiment has high strength and light weight characteristics, and may have various shapes or shapes as needed. In addition, the manufactured molded article may be applied to various furniture such as a table, a dining table, and a chair, and may be applied to various camping equipment.

Hereinafter, analysis results will be described through a number of experiments.

For 31 samples, the results of measuring the items of fiber type, number of layers, number of layers, resin content, heat treatment temperature, heat treatment time, vacuum strength, molding temperature, molding time, weight of molded article, and maximum load of molded article are shown in Table 4 below. it was

Epoxy resin was used as the resin, the prepreg having a plain weave fiber form was purchased from SK Chemicals, and the prepreg having a twill fiber form was purchased from Tibcarbon.

Sample
# fiber
shape singular
(K) Layer
Count Suzy
content
(%) heat treatment
Temperature
(℃) heat treatment
hour
(minute) vacuum
robbery
(MPa) plastic surgery
Temperature
(℃) plastic surgery
hour
(minute) molded product
weight
(g) molded product
Maximum load (Kg) One plain weave One One 40 100 30 0.03 140 60 22 5 2 plain weave One One 40 120 30 0.03 140 60 22 5 3 plain weave One One 40 140 30 0.03 150 60 22 5 4 plain weave One 2 40 100 20 0.03 140 40 38 15 5 plain weave One 2 40 120 30 0.03 140 60 38 15 6 plain weave One 2 40 140 30 0.03 150 30 38 15 7 plain weave One 3 40 100 25 0.03 130 40 47 35 8 plain weave One 3 40 120 30 0.03 130 50 47 35 9 plain weave One 3 40 140 30 0.03 140 60 47 35 10 plain weave One 4 40 120 20 0.03 130 60 59 90 11 plain weave One 4 40 140 20 0.03 140 60 59 90 12 plain weave One 5 40 100 20 0.03 140 60 68 200 13 plain weave One 5 40 140 20 0.03 140 60 68 200 14 plain weave 3 One 40 120 20 0.03 140 60 18 5 15 plain weave 3 2 40 120 20 0.03 140 60 33 10 16 plain weave 3 3 40 120 20 0.03 140 60 42 30 17 plain weave 3 4 40 120 20 0.03 140 60 54 75 18 plain weave 3 5 40 120 20 0.03 140 60 60 170 19 plain weave 1+3 1(1K)+1(3K) 40 120 25 0.03 140 40 35 15 20 plain weave 1+3 2(1K)+1(3K) 40 120 25 0.03 140 45 40 35 21 plain weave 1+3 2(1K)+2(3K) 40 120 20 0.03 140 60 55 80 22 plain weave 1+3 3(1K)+2(3K) 40 120 30 0.03 140 60 72 185 23 twill 3 One 42 130 20 0.03 140 50 13 5 24 twill 3 2 42 130 20 0.03 140 50 28 10 25 twill 3 3 42 130 20 0.03 140 40 34 20 26 twill 3 4 42 140 20 0.03 140 40 47 65 27 twill 3 5 42 140 20 0.03 140 50 56 155 28 twill 3 3 30 100 20 0.04 140 20 29 20 29 twill 3 4 30 100 20 0.03 140 20 43 60 30 twill 3 1 (30%)+1 (42%) 30%+42% 100℃+
120℃ 10 minutes+
20 minutes 0.03 140 30 - - 31 twill 3 2(30%)+2(42%) 30%+42% 100℃+
120℃ 10 minutes+
20 minutes 0.03 140 50 50 60

Referring to Table 4, it can be seen that the heat treatment (melting) temperature and time, vacuum strength, and molding time do not affect weight and load.

Also, it can be seen that the maximum load increases with the number of layers.

In addition, when the number of stages is 3K, it is lighter than the case of 1K, but it can be seen that the maximum load that can be endured is relatively small.

In addition, when 1K and 3K were mixed, they were heavier than 3K and showed strong maximum load. From this, when manufacturing a panel stronger than 3K, it can be one way to lower the production cost.

In addition, compared to the case of plain weave when the fiber form is twill weave, it was found to have a characteristic of being stretched well when attaching a mold, and was found to be a feature that can be utilized to reduce fine wrinkles during product production.

In addition, as a result of mixing and using prepregs having different epoxy resin contents (Sample 30), a phenomenon occurred that the epoxy resin did not drain properly and the 42% prepreg did not cure properly.

Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

110: vacuum bed 120: mold
130: prepreg laminate 140: molding pad

Claims (11)

Laminating two or more prepreg sheets (Prepreg sheet) to form a prepreg laminate,
a disposing step of disposing a mold, the prepreg laminate and a forming pad in a forming apparatus;
a heat treatment step of applying heat to the prepreg laminate;
attaching the prepreg laminate to the mold by forming a sub-vacuum state in the molding apparatus; and
Preparing a molded article by curing the prepreg laminate
including,
A tension having a predetermined size is formed on the molding pad.
A method of forming carbon fiber reinforced plastics.
In claim 1,
In the step of forming the prepreg laminate,
The two or more prepreg sheets include a first prepreg sheet and a second prepreg sheet adjacent to each other, and one side of the first prepreg sheet is one side of the first prepreg sheet in the second prepreg sheet A method of molding carbon fiber reinforced plastic in contact with the surface facing the
In claim 2,
Each of the two or more prepreg sheets comprises a thermosetting resin,
A carbon fiber reinforced plastic molding method in which the two or more prepreg sheets are compressed and adhered with a force of 40 to 60 kgf.
In claim 1,
The molding pad includes silicon (Si),
The thickness of the molding pad is 1 to 5 mm carbon fiber reinforced plastic molding method.
In claim 4,
The tensile strength of the molding pad is 50 kf / cm ² or more carbon fiber reinforced plastic molding method at 25 ℃.
In claim 4,
As the size of the tension of the molding pad increases, the bending strength of the corner of the molded article increases.
In claim 4,
As the size of the tension of the molding pad increases, the size of the surface roughness of the molded article decreases.
In claim 4,
The molding pad is a carbon fiber reinforced plastic molding method comprising a hole (hole) having a diameter of 0.2 cm or less in the central region.
In claim 1,
The heat treatment step is a carbon fiber reinforced plastic molding method performed for 5 to 30 minutes at 120 to 140 ℃.
In claim 1,
In the heat treatment step,
The carbon fiber reinforced plastic molding method in which the value of the tensile strength/tensile modulus of the prepreg laminate becomes small, and the value of the flexural strength/flexural modulus of the prepreg laminate decreases.
In claim 1,
In the step of attaching the prepreg laminate to the mold,
The pressure in the sub-vacuum state is 0.05 to 0.08 MPa, and the carbon fiber reinforced plastic molding method is pressurized for 30 minutes to 1 hour.

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