KR102337320B1 - Manufacturing method of lightweight stiffener with cfrtpc insert injection molding - Google Patents

Abstract

The present invention relates to a lightweight stiffener in which CFRTPC is insert injection molded. More specifically, the continuous fiber composite is disposed along the side portion where the collision is made in the mold cavity, and the long fiber composite is foamed and injected so that it is disposed inside the continuous fiber composite disposed on the side in the mold cavity. Accordingly, it is possible to reduce the weight of the stiffener, reduce production cost, and shorten the production process.

Description

CFRTPC insert injection molded lightweight stiffener manufacturing method {MANUFACTURING METHOD OF LIGHTWEIGHT STIFFENER WITH CFRTPC INSERT INJECTION MOLDING}

The present invention relates to a lightweight stiffener in which CFRTPC is insert injection molded. More specifically, the continuous fiber composite is disposed along the side portion where the collision is made in the mold cavity, and the long fiber composite is foamed and injected so that it is disposed inside the continuous fiber composite disposed on the side in the mold cavity. Accordingly, it is possible to reduce the weight of the stiffener, reduce production cost, and shorten the production process.

Recently, as regulations on environment and fuel efficiency are getting stricter around the world, weight reduction, which improves fuel efficiency by reducing the weight of a vehicle, has become a major topic in the automobile industry.

The minimum fuel efficiency regulation level for automobiles in major countries including the United States and Europe is expected to be strengthened from 14.5 to 18.1 km per liter in 2015 to 19.9 to 26.5 km per liter in 2020. It has become the biggest challenge for companies to solve.

The stiffener installed at the bottom of the bumper, which is one of the parts that requires weight reduction to reduce the weight of automobiles, increases the weight and cost rapidly when the strength is increased. becomes impossible

Recycled resin products and thermoplastic resin injection were mainly used as light-weighting technologies for replacing metals in the past, but these have a problem in that they lack strength and rigidity.

The field that was developed later was SFT (Short-Fiber Reinforced Thermoplastic), which is a compound material in which reinforcing materials such as glass fiber or carbon fiber are dispersed in a resin in the form of short fibers. Glass Mat Thermoplastic) was mainly used, but it is difficult to substitute metal for these materials.

As a solution to this problem, a thermoplastic composite material reinforced with long fibers or continuous fibers is being used.

Long-fiber reinforced thermoplastic composites are LFT (Long Fiber Thermoplastics), which are attracting attention recently due to their superior structural strength, impact strength, and flexural modulus compared to GMT, which is a conventional short-fiber reinforced composite material.

The LFT manufacturing method includes the LFT-G (Long Fiber Thermoplastic-Granules) method of manufacturing pellets impregnated with resin and fibers, followed by injection and press molding, and the LFT-G (Long Fiber Thermoplastic-Granules) method, which directly chops carbon fibers to the desired length, and impregnates them with resin. There is the LFT-D (Long Fiber Thermoplastic-Direct) method for compounding.

In addition, CFRTPC (Continuous-Fiber Reinforced Thermoplastic) is a representative thermoplastic composite material reinforced with continuous fibers.

As a CFRTPC manufacturing method, there is a DBP (Double-Belt Pressing) molding method in which a preform impregnated with a thermoplastic resin is laminated and pressed.

In the case of a thermoplastic resin product, it is advantageous for product molding because it uses an injection process with high design freedom, but it does not satisfy the physical properties.

Accordingly, there is a need to develop a process method and continuous fiber composite material that can satisfy weight reduction while reinforcing the required strength.

KR 10-1470174 B1

It is an object of the present invention to reduce the weight of the stiffener, reduce production cost, and shorten the production process. To this end, the continuous fiber composite material is disposed along the side portion where the collision is made in the mold cavity, and the long fiber composite material is foamed and injected so as to be disposed inside the continuous fiber composite material disposed on the side side in the mold cavity.

In order to achieve the above object, the step of inserting the continuous fiber composite material (CFRTPC) according to the present invention as a preform into the mold cavity, the long fiber composite material (LFT) in the form of a fillet is put into the hopper of the injection molding machine to foam injection into the mold and welding and molding the continuous fiber composite material and the long fiber composite material.

According to the present invention, the continuous fiber composite material is composed of glass fiber (Glass Fiber) of 60wt% content.

According to the present invention, the long fiber composite material is obtained with glass fibers in an amount of 20 wt%.

According to the present invention, in the foam injection step, a foaming agent having a content of 3 wt% is added to the hopper.

According to the present invention, foam injection is performed with a foaming agent in the form of microcapsules.

According to the present invention, it is to foam and inject a foaming agent in a physical form into which Gas (supercritical fluid) is injected.

According to the present invention, foam injection is performed with a chemical type foaming agent, which is an additive composed of a thermally decomposed organic compound.

According to the present invention, the continuous fiber composite material is insert-injected into the long fiber composite material, and the long fiber composite material is foam-molded.

According to the present invention, during foam molding of the long fiber composite material, a foaming agent in an amount of 3 wt% is injected.

According to the present invention, the continuous fiber composite material is composed of 60% glass fiber (Glass Fiber).

According to the present invention, the long fiber composite material is composed of glass fibers in a content of 20%.

According to the present invention, foam injection is performed with a foaming agent in the form of microcapsules.

According to the present invention, it is to foam and inject a foaming agent in a physical form into which Gas (supercritical fluid) is injected.

According to the present invention, foam injection is performed with a chemical type foaming agent, which is an additive composed of a thermally decomposed organic compound.

According to the lightweight stiffener in which the CFRTPC of the present invention is insert injection-molded, the continuous fiber composite is disposed along the side portion where the collision occurs in the mold cavity, and the long fiber composite is disposed inside the continuous fiber composite disposed on the side in the mold cavity. While satisfying the high-speed impact performance, there is an effect that the weight of parts can be realized at the same time.

In addition, in the process of inserting the continuous fiber composite material, the preform is formed by using the filament of a 3D printer to solve the manufacturing cost problem caused by the conventional mold manufacturing, and the loss rate that occurred during the trimming process in the mold can be reduced, and the defect rate has the effect of reducing

In addition, since the process of inserting through the conventional mold is omitted, there is an effect that industrial waste is reduced due to the reduction of the film residue by the trimming process of the conventional mold.

In addition, it is possible to see the effect of weight reduction and cost reduction while having a positive effect on the maximum displacement value by foaming and injection molding the long fiber composite material in the form of a pellet so that the foaming agent content is 3 wt%.

1 is a perspective view of a stiffener composed of a continuous fiber composite material and a long fiber composite material according to the present invention.
2 is a view showing a position where the continuous fiber composite material and the long fiber composite material are disposed in the mold cavity according to the present invention.
3 is a flowchart illustrating a process in which a stiffener composed of a continuous fiber composite material and a long fiber composite material according to the present invention is manufactured.
4 is a view showing a state before the static load and maximum displacement of the stiffener according to the present invention is tested.
5 shows a state in which a fracture surface is generated after testing the static load and maximum displacement of the stiffener according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

The terminology used herein is for the purpose of describing the embodiments, and thus is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, "comprise" and/or "comprising" refers to the presence of one or more other components, steps, operations and/or elements mentioned. or addition is not excluded.

The lightweight stiffener in which CFRTPC is insert injection-molded according to the present invention includes a continuous fiber composite material 100 and a long fiber composite material 200 .

Here, the continuous fiber composite material 100 is composed of a thermoplastic resin, and may be made of one or a combination of two or more of PP, PA6, PA66, TPU, PET, HDPE, PPS, and PEEK. One or a combination of two or more of fiber (GF: Glass Fiber), carbon fiber, and aramid fiber may be used.

In particular, the continuous fiber composite material 100 is preferably CFRTPC (Continuous-Fiber Reinforced Thermoplastic) configured to be dispersed in a state in which a content of 60 wt% of glass fiber in the form of continuous fiber is impregnated in polypropylene resin (PP Resin).

In addition, the long fiber composite material 200 is provided with PP-LFT (Long Fiber Thermoplastic) configured to be dispersed in a state in which a content of 20 wt% of glass fiber in the form of long fiber is impregnated in polypropylene resin.

The stiffener according to the present invention is manufactured with the configuration of the continuous fiber composite material 100 and the long fiber composite material 200 as described above, and is implemented in the shape shown in FIG. 1 .

In detail, referring to FIG. 1 , the continuous fiber composite 100 is a part where a collision occurs in the event of an accident at the front of the vehicle in order to be manufactured as a stiffener, and is disposed along the side part within the mold cavity 14, The fiber composite material 200 is preferably disposed inside the continuous fiber composite material 100 disposed on the inner side of the mold cavity 14 .

This arrangement was created to solve various problems in the prior art, and while satisfying high-speed collision performance, it is possible to realize weight reduction of parts at the same time.

That is, it is possible to reduce the weight of the parts by injecting the long fiber composite material 200 into the portion where rigidity is not particularly required except for the side where strength is essential in the form of the stiffener.

Hereinafter, a method for manufacturing a lightweight stiffener in which CFRTPC is insert injection-molded will be described with reference to FIG. 3 .

In the method for manufacturing a lightweight stiffener in which CFRTPC is insert injection-molded according to the present invention, a continuous fiber composite (CFRTPC, 100) is inserted into the mold cavity 14 as a preform (S100), and a long fiber composite (LFT, 200) is pelletized. In the form of input into the hopper 11 of the injection molding machine, foam injection into the mold (S200) and the continuous fiber composite material 100 and the long fiber composite material 200 are welded and molded (S300). .

First, the step (S100) of inserting the continuous fiber composite material (CFRTPC, 100) into the mold cavity 14 as a preform will be described.

Referring to FIG. 2 in the step (S100) of inserting the continuous fiber composite material (CFRTPC, 100) into the mold cavity 14 as a preform, the continuous fiber composite material 100 is disposed along the edge (side) of the mold cavity 14 will become

The continuous fiber composite material 100 is composed of a thermoplastic resin, and may be made of one or a combination of two or more of PP, PA6, PA66, TPU, PET, HDPE, PPS, and PEEK. (GF: Glass Fiber), one or two or more of carbon fiber and aramid fiber may be used in combination.

In particular, the continuous fiber composite material 100 is preferably CFRTPC (Continuous-Fiber Reinforced Thermoplastic) configured to be dispersed in a state in which a content of 60 wt% of glass fiber in the form of continuous fiber is impregnated in polypropylene resin (PP Resin).

This is a part that requires strength in the shape of the stiffener, and by arranging the continuous fiber composite material (CFRTPC, 100) with high rigidity, it is possible to satisfy the high rigidity and strength reliability of the stiffener.

In addition, when the continuous fiber composite material 100 is disposed along the side surface in the mold cavity 14, as shown in FIG. 2, it is not limited to have a rectangular hollow part, but along the side surface of the mold cavity 14 It can be deployed in various ways as long as it has sufficient strength in the event of an accidental collision in front of the vehicle.

At this time, it is preferable to form the preform by using the filament of the 3D printer, which not only solves the manufacturing cost problem due to the conventional mold manufacturing, but also reduces the loss rate that occurred during the trimming process in the mold, and the defect rate has the effect of reducing

Therefore, it is possible to reduce the number of preform manufacturing steps that require the conventional thermoplastic tape to be cut to the required length, preheated, and the preheating process of putting the thermoplastic tape into the mold after a certain period of time and the shaping process (two steps), It can also reduce costs related to this.

As described above, by utilizing the delta method of the trigonometric concept of the multiple degree of freedom robot system and the method in which the output is stably fixed to the floor, it is possible to respond to the production of various types of small-volume products, and the conventional rod And sheet insertion, compared to insert injection, design freedom, weight reduction, and productivity improvement are generated.

Insert injection including a preform configuration in which the described continuous fiber composite material 100 is inserted into the mold cavity 14 is an injection molding method that integrates heterogeneous or heterogeneous plastics or parts other than plastics in the mold. The process of integration with the composite material 200 is achieved, and the occurrence of cracks due to the difference in thermal expansion index between the metal mold and the resin in the plastic part adjacent to the insert of the conventional mold can be eliminated.

Next, the long fiber composite material (LFT, 200) in the form of pellets is put into the hopper 11 of the injection molding machine and foamed and injected into the mold (S200), and the continuous fiber composite material 100 in the mold cavity 14 ) in the inserted state, the long fiber composite material 200 is input in the form of pellets into the hopper 11 of the injection molding machine.

In detail, the long fiber composite material 200 is in the form of a pellet, a plurality of them are put into the hopper 11, melted by the cylinder 12, and passed through the nozzle 13 to be transported toward the mold cavity 14. have. Here, the cylinder 12 may be in the form of a cylinder and an injection screw, which are known mold parts, and may promote injection of the long fiber composite material 200 by limiting certain values in rotation speed, pressure, and temperature (FIG. 2). Reference).

The cylinder 12 can be melted by compressing the long fiber composite material 200 in the form of pellets put into the hopper 11 and generating heat through friction and pressure.

Accordingly, there is an effect of reducing the weight of the parts by injecting the long fiber composite material 200 into a portion where rigidity is not particularly required except for the side where strength is essential in the form of the stiffener.

By using the continuous fiber composite material 100 and the long fiber composite material 200 as described above, not only the structural strength, impact strength, flexural modulus, etc. are excellent compared to the conventional GMT, but also the molding time is short and the effect of easy recycling is achieved. occurs In addition, a reduction in the number of processes can result in a reduction in manufacturing cost.

At this time, the long fiber composite material 200 is preferably foamed and injected, and the foaming method includes a microcapsule injection method, a foaming agent by physical foaming and chemical foaming.

First, in the foaming by microcapsules, the method of inserting the microcapsules is a hollow capsule wrapped with a polymer, the internal pores expand by the molding temperature, and is a foaming agent having a structure that can be foamed by stretching the polymer, and physical foaming. is a foaming method that utilizes supercritical fluid, and is a foaming agent that forcibly injects gas (supercritical fluid) into the injection machine nozzle to form uniform pores inside the mold during injection. Chemical foaming is an additive composed of pyrolytic organic compounds It is a foaming agent that decomposes components by heat during the molding process and forms pores inside the product with the gas generated in the process. In the present invention, microcapsules are most recommended, but the present invention is not limited thereto, and there is no limitation on the type and shape of the foaming agent for forming pores.

At this time, the continuous fiber composite material 100 is composed of GF 60wt%, the long fiber composite material 200 is 20wt% glass fiber, and the foaming content is 3wt%.

Hereinafter, the effect improved according to the added foaming content is to be proved through the following experiments.

Product performance evaluation methods include static load evaluation to determine the maximum load value until failure by applying a static load to the upper part of the stiffener, maximum displacement evaluation to measure the deformation distance (displacement) when the product bends when pressurized, and total product It proceeds to weight evaluation to determine the degree of weight reduction by measuring the weight.

Here, the foaming is made by the injection of the foaming agent in the form of microcapsules, and will be described based on this. At this time, the foaming agent in the form of chemical and physical foaming also exhibits the same effect, but will be omitted to avoid overlapping description.

First, with reference to Table 1 below, the effect of the content of glass fibers impregnated in the continuous fiber composite material and the long fiber composite material is compared.

division Insert
(Continuous fiber composite material GF60%, 8Φ) Weight
(g) dead load
(kgf) Maximum displacement (mm) (a) Long Fiber Composite (GF30wt%) X 510 123 32.0 (b) Long Fiber Composite (GF20wt%) O 493 127 17.1 (c) Long fiber composite (GF20wt%) foaming agent 1wt% O 463 124 19.5

Referring to Table 1, in sample (a), 30 wt% of glass fiber is contained in the long fiber composite material 200, and the weight, static load and maximum of the stiffener manufactured by injection molding without the insert process of the continuous fiber composite material 100 Displacement is measured, and sample (b) contains 20 wt% of glass fiber in the long fiber composite 200 and the weight, static load, and maximum displacement of the stiffener manufactured by injection molding in which the continuous fiber composite 100 is inserted. is measured, and in the sample (c), 20 wt% of glass fiber is contained in the long fiber composite 200 in the same way as in the sample (b), and the inserting process of the continuous fiber composite 100 is performed, but additionally 1 wt% of a foaming agent Weight, static load, and maximum displacement of stiffeners manufactured by injection molding with additional content are measured.

As described above, the stiffeners of samples (a) to (c) manufactured differently were tested in the form shown in FIGS. 4 and 5 (product performance evaluation).

4 shows the pressure driving device positioned on the upper part of the stiffener (made of samples (a) to (c)) just before pressing, and FIG. 5 is the stiffener receiving the maximum load from the pressure driving device to breakage. In this case, it is shown that the fracture surface (A) is generated.

As can be seen from Table 1, the static loads of samples (a) to (c) (the load endured when the product is pressed on the upper part of the stiffener) are small and there is no significant difference, but it can be confirmed that there is a difference in weight and maximum displacement. have.

That is, when insert injection molding is not performed, the stiffener in which the continuous fiber composite 100 containing 60 wt% of glass fiber is insert injection-molded has a lighter weight, and the product is deformed when pressurized with a static load, which is the maximum distance pushed back It can be seen that the displacement is short.

Therefore, it can be understood that the stiffener in which the continuous fiber composite material 100 containing 60wt% of glass fiber is insert injection-molded into the long fiber composite material 200 is a molding process that meets the purpose of the present invention in which weight reduction can be practiced.

However, rather than insert injection molding the continuous fiber composite material 100 into the long fiber composite material 200, the stiffener of the sample (c) in which the content of 1 wt% of the foaming agent is additionally composed together with the long fiber composite material 200 is 463 g. This is the best way to achieve weight reduction. In addition, since the maximum displacement of the sample (c) is 19.5 mm, which does not show a significant difference when compared with the sample (b), which is 17.1 mm, when the weight reduction of the stiffener, which is the object of the present invention, is in mind, the sample (c) having a relatively light weight ), it can be seen that the molding process is excellent.

As described above, it was confirmed that the configuration in which the foaming agent is added in the injection molding in which the foam molding for the manufacture of the stiffener is combined is suitable for reducing the weight of the stiffener. At this time, the content of the blowing agent is preferably 3wt%.

Blowing agent content (wt%) Weight(g) Static load (kgf) Maximum displacement (mm) (i) One 463 124 19.5 (j) 3 445 117 20.7 (k) 5 411 101 35.2

Table 2 shows the sample values produced by varying the content of the blowing agent in the process of foaming and injecting the long fiber composite material 200 in the form of pellets containing 20 wt% of glass fiber melted in the mold in which the continuous fiber composite material 100 is inserted. to be.

Referring to Table 2, 1wt% and 3wt% of the foaming agent content do not show a large difference in static load and maximum displacement, but show a large difference in weight of 463(g) and 445(g), respectively, so that the foaming agent content is 3wt% It can be seen that the phosphorus sample (j) can generate a stiffener weight reduction effect.

On the other hand, the sample (k) having a foaming agent content of 5 wt% can generate a weight reduction effect to a greater extent than the sample (j), but when the foaming agent content is 5 wt%, the static load, which is the maximum load value up to breakage, is 101 (kgf) ), which is 16 (kgf) lower than the foaming agent content of 3 wt%, and the deformation distance at which the bending phenomenon occurs during pressurization is 35.2 (mm), which is rather increased by 15 (mm) than the foaming agent content 3 wt%. For this reason, it is impossible to satisfy design specifications required during manufacturing.

Accordingly, when the blowing agent content is 3wt%, it is possible to minimize the risk of damage and secure the weight reduction effect at a level of 10%, so the content of the blowing agent is most preferably 3wt%.

Next, the step (S300) of welding and molding the continuous fiber composite material and the long fiber composite material is performed.

This process is a plasticizing process, holding pressure, and cooling step made in known injection molding, and the surface of the injection product is surface activated, and the long fiber composite material 200 and the foaming agent 300 are added to the continuous fiber composite material 100 of the present invention without an adhesive. can be attached. The step (S300) of welding and molding the continuous fiber composite material and the long fiber composite material as described above is performed while maintaining a strong pressure to completely fill the mold cavity 14 and a low pressure until it solidifies, and is a known technique. A detailed description will be omitted.

The stiffener manufactured through the described series of processes may be formed as a circular rod, and is not necessarily limited to a circular shape, and may be an ellipse as well as a polygonal shape having an angle.

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

11: hopper, 12: cylinder,
13: nozzle, 14: mold cavity,
100: continuous fiber composite material, 200: long fiber composite material.

Claims (14)

Upon completion of the stiffener, manufacturing a continuous fiber composite (CFRTPC) as a preform so as to be positioned at a portion where a collision occurs in the case of an accident at the stiffener, and placing it along the side in a mold cavity having the shape of the stiffener;
Long fiber composite material (LFT) having relatively lower rigidity and lower weight than the continuous fiber composite material is put into the hopper of the injection molding machine in the form of a fillet, so that the long fiber composite material (LFT) is located inside the continuous fiber composite material. Foam injection into the mold; and
Including; welding and molding the continuous fiber composite material and the long fiber composite material;
The preform is manufactured using a filament of a 3D printer, characterized in that
CFRTPC insert injection molded lightweight stiffener manufacturing method.
According to claim 1,
The continuous fiber composite material is composed of glass fiber (Glass Fiber) with a content of 60 wt%.
CFRTPC insert injection molded lightweight stiffener manufacturing method.
3. The method of claim 2,
The long fiber composite material is composed of glass fibers with a content of 20 wt%.
CFRTPC insert injection molded lightweight stiffener manufacturing method.
4. The method of claim 3,
In the foam injection step,
3wt% of the blowing agent is added to the hopper
CFRTPC insert injection molded lightweight stiffener manufacturing method.
5. The method of claim 4,
It is a foam injection with a foaming agent in the form of microcapsules.
CFRTPC insert injection molded lightweight stiffener manufacturing method.
5. The method of claim 4,
It is a foaming injection with a foaming agent in a physical form that injects gas (supercritical fluid).
CFRTPC insert injection molded lightweight stiffener manufacturing method.
5. The method of claim 4,
It is a foaming injection with a chemical type foaming agent, which is an additive composed of thermal decomposition organic compounds.
CFRTPC insert injection molded lightweight stiffener manufacturing method.
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