KR20090051628A - Reverse vacuum system for minimizing thickness variation of vartm process - Google Patents

Abstract

The present invention additionally installs a tube and a valve for applying a vacuum pressure at a point other than the outlet without the need for additional facility equipment, and applies a reverse vacuum at any point, thereby inducing the distribution of the even liquid polymer. As compared to the prior art, it relates to a reverse vacuum system VARTM composite material manufacturing process minimizing the thickness change to ensure the improvement of thickness uniformity while maintaining the impregnation speed. The reverse vacuum system VARTM composite material manufacturing process minimizing the change in thickness is a reverse vacuum system VARTM (Vacuum Assist Resin Transfer) in which the thickness change is minimized in VARTM, which is the method most recently used most often among the methods for manufacturing polymer composite materials. Molding) A composite material manufacturing process, wherein the reverse vacuum system VARTM composite material manufacturing process minimizing the thickness variation of the present invention is a vacuum pressure at a point other than an outlet in manufacturing a polymer composite material using the VARTM method. It is characterized in that the tube and the valve to apply the additional installation by applying a reverse vacuum (reverse vacuum), the pressure of the liquid polymer is maintained at normal pressure.

Description

Reverse vacuum system for minimizing thickness variation of VARTM process

The present invention relates to a process for manufacturing a vacuum assisted vacuum transfer system (VARTM) which minimizes a change in thickness. In detail, the present invention relates to a process for manufacturing a polymer composite material, which is produced in VARTM, which is the most frequently used method. The present invention relates to a process for producing a polymer fiber reinforced composite material using a reverse vacuum system VARTM method that minimizes the change in thickness by solving a problem that the thickness of a product is not constant.

In general, polymer fiber-reinforced composite material is very excellent in specific strength and non-rigidity has recently been applied in many fields as a substitute material for metal materials. Although a variety of process methods for manufacturing polymer fiber-reinforced composite materials having such characteristics have been proposed, VARTM is most widely used as a process method with low process cost and quality and mass production. The VARTM is subjected to a process of curing the polymer after impregnating all the fibers by infiltrating the liquid polymer into the vacuum-packed reinforcing fibers as shown in FIG. At this time, the penetration of the liquid polymer uses the pressure difference between the vacuum pressure on the outlet side and the atmospheric pressure liquid polymer on the inlet side, which affects the thickness uniformity of the product. That is, the greater the difference in the pressure distribution during fixing, there was a disadvantage that the thickness uniformity of the produced product is significantly reduced.

Therefore, methods have been proposed to solve the thickness nonuniformity, which is a major problem of using the conventional VARTM method for producing polymer fiber reinforced composite materials. In detail, various methods have been proposed and used to compensate for the above-mentioned thickness non-uniformity. Firstly, it is proposed by Boeing, which is "controlled" in International Patent Application Publication No. WO 03/101708 A1. Controlled atmospheric pressure infusion process, which reduces the pressure difference by reducing the pressure difference between inlet and outlet by reducing the pressure of liquid polymer from normal to low Discloses the technology. However, this method has a disadvantage in that the flow rate of the liquid polymer is slow due to the low air pressure difference, and thus a long process time is required.

Next, U.S. Patent Application No. 2007/0141334, entitled "Rotational vacuum assisted resin transfer molding," rotates the product to improve the thickness uniformity of the VARTM product. Although a method of deriving a distribution is proposed, there is a disadvantage in that thickness uniformity improvement cannot be obtained satisfactorily by this method.

In addition, as a membrane-based VARTM process, a method of improving thickness uniformity by inserting a porous membrane in vacuum packaging to apply the same pressure to all product surfaces has been proposed. However, this method has the disadvantage that the membrane is very expensive and the range of membranes and liquid polymers available is very small.

In addition, the document "Effects of processing conditions on vacuum assisted resin transfer molding process (Elis J. Rigas, Army Research Laboratory ARL-TR-2480)" includes a process of double vacuum bag packaging to improve thickness uniformity. Although a thickness uniformity of about 6% is secured, there is still a disadvantage that a satisfactory thickness uniformity improvement cannot be obtained.

As described above, in the conventionally presented methods, the above-mentioned problems are inherent, and therefore, a method of solving the above problems is more economical and practically applicable, and a satisfactory thickness uniformity improvement is urgently required. It's happening.

Accordingly, it is an object of the present invention to provide a reverse vacuum system VARTM composite material manufacturing process that minimizes the change in thickness that can improve the thickness uniformity while maintaining the liquid polymer injection pressure at atmospheric pressure and maintaining the impregnation rate.

Another object of the present invention is to provide an inverse vacuum system VARTM composite material manufacturing process that economically minimizes the thickness change by inducing evenly divided liquid polymers without the need for additional facilities.

Another object of the present invention is to provide a reverse vacuum system VARTM composite material manufacturing process that solves all the problems of the prior art described above.

The reverse vacuum system VARTM composite material manufacturing process minimizing the thickness change of the present invention for achieving the above object, in the production of the polymer composite material using the VARTM method, uniform in all positions of the vacuum bag laminated the reinforcing fibers in the mold It is characterized by producing a polymer fiber reinforced composite material by applying a vacuum pressure.

Here, the uniform vacuum pressure of the vacuum bag in which the reinforcing fibers are laminated in the mold is obtained by additionally installing a reverse vacuum by installing a tube and a valve for applying vacuum pressure at a point other than an outlet. This is preferred.

In addition, the tube for applying a vacuum pressure to a point other than the outlet (outlet) is preferably installed on the inlet (inlet) side.

In addition, the valve for applying the reverse vacuum is preferably installed between the tube installed on the inlet side, the tube connecting the outlet side and the vacuum (outlet) side.

In addition, the pressure of the liquid polymer in the process is preferably maintained at atmospheric pressure.

In addition, the reverse vacuum (reverse vacuum) is preferably applied after the complete impregnation of the liquid polymer.

On the other hand, it is preferable to provide the polymer fiber reinforced composite material obtained by the above-mentioned process.

As described above, the VARTM method, which has been widely used for manufacturing large structures from polymer fiber-reinforced composite materials, has been widely used between the inlet and the outlet, particularly when the size of the product is increased. There is a risk that the difference in thickness due to the pressure difference is very large, and the difference in thickness of the product brings about a change in physical properties and adversely affects the reliability of the structure. In order to apply the reverse vacuum by additionally installing tubes and valves that apply vacuum pressure at points other than the outlet, the thickness difference of the products produced during the manufacture of the used polymer fiber reinforced composite material is applied. While reducing the deviation by 50%, the filling time of the liquid polymer is comparable to conventional VARTM. W was to ensure the same charging time.

The reverse vacuum system VARTM composite material manufacturing process of the present invention configured as described above is additionally provided with a tube and a valve for applying a vacuum pressure at a point other than the outlet without the need for additional facility equipment, and any desired point after the impregnation is completed. Reverse vacuum is applied everywhere, thereby inducing the distribution of evenly distributed liquid polymers, thereby ensuring an improvement in thickness uniformity while maintaining the impregnation rate unlike the prior art. In particular, the reverse vacuum system VARTM composite material manufacturing process of the present invention reduces the thickness variation of the conventional VARTM process method by more than 50%, and the impregnation rate of the liquid polymer is faster than the improved methods of the conventional VARTM process method described above. Low cost processes are possible.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

First, FIG. 1 is a schematic cross-sectional view schematically showing a conventional general VARTM process, and FIG. 2 is a schematic cross-sectional view schematically showing a reverse vacuum system VARTM composite material manufacturing process with a minimum thickness change according to the present invention.

Unlike the conventional VARTM process system of FIG. 1, the VARTM process system according to the present invention further includes a tube 5 and a valve 4 between the inlet 1 and the vacuum 3. Lose.

The reinforcing fibers are laminated to a mold and packaged in a vacuum bag to produce a polymer composite using the VARTM process system of the present invention shown in FIG. The valve 4 of the tube 5 going from the inlet 1 to the vacuum 3 is kept closed, and the valve on the liquid resin side is subjected to vacuum pressure in the open state.

The liquid polymer then impregnates the fibers and converts the valve on the liquid resin side into the closed state to prevent further resin inflow. Subsequently, the valve 4 at the inlet 1 and the vacuum 3 side is converted to open so that a vacuum pressure is applied to both the inlet 1 and the outlet 2 and maintained until the liquid polymer is cured. Complete the manufacture of the polymer composite material.

Hereinafter, although an Example and a comparative example demonstrate this invention in detail with reference to an accompanying drawing, of course, this invention is not limited to this.

Example

Reinforcing fibers were laminated to a mold and packaged in a vacuum bag to produce a polymer composite using the VARTM process system shown in FIG. 2. Thereafter, the valve 4 of the tube 5 going from the inlet 1 to the vacuum 3 was kept in the closed state, and the valve on the liquid resin side was subjected to vacuum pressure in the open state, and then the liquid polymer was After all the fibers are impregnated, the valve on the liquid resin side is closed to prevent further resin inflow, and then the inlet (1) and the valve (4) on the vacuum (3) side are opened to convert the inlet (1) and Vacuum pressure was applied to both sides of the outlet 2 and maintained until the liquid polymer was cured to complete the manufacture of the polymer composite material. The thickness of each prepared polymer composite material was measured and shown in FIG. 3 and Table 1. FIG.

Comparative example

Reinforcing fibers were laminated to a mold and packaged in a vacuum bag to produce a polymer composite using the conventional VARTM process system shown in FIG. 1. The valve on the liquid resin side was applied with vacuum pressure in the open state. Then, after the liquid polymer impregnated all the fibers, the valve on the liquid resin side was converted to the closed state to prevent further resin inflow, and then maintained until the liquid polymer was cured to complete the manufacture of the polymer composite material. The thickness of each prepared polymer composite material was measured and shown in FIG. 3 and Table 1. FIG.

Distance (cm) Comparative example Example 0 6.424 6.290 5 6.466 6.300 10 6.358 6.318 15 6.386 6.338 20 6.414 6.322 30 6.436 6.370 35 6.352 6.298 40 6.324 6.308 Average 6.395 6.318 Standard Deviation 0.048202 0.025989

As can be seen in Table 1 and FIG. 3, the polymer composite material produced by the embodiment according to the present invention has almost no thickness variation compared to the polymer composite material prepared according to the comparative example, which is a conventional method. Was improved.

The present invention is not limited to the above embodiments, and various changes can be made by any person having ordinary knowledge in the field of the present invention without departing from the gist of the present invention as claimed in the following claims. It will be said that there is a technical spirit of the present invention to the extent.

1 is a schematic cross-sectional view schematically showing a conventional general VARTM process,

2 is a schematic cross-sectional view schematically showing a process of manufacturing a reverse vacuum system VARTM composite material with a minimum thickness change according to the present invention;

Figure 3 is a graph showing the thickness data for each distance of the composite material prepared according to the reverse vacuum system VARTM composite material manufacturing process and the conventional VARTM composite material manufacturing process of the present invention.

* Brief description of major symbols in the drawings

1 --- Inlet 2 --- Outlet

3 --- vacuum 4 --- valve

5 --- tube

Claims (7)

In manufacturing the polymer composite material using the VARTM method, Inverse vacuum system VARTM composite material manufacturing process minimizing the thickness change characterized by producing a polymer fiber reinforced composite material by applying a uniform vacuum pressure to all positions of the vacuum bag laminated the reinforcing fibers in the mold. The method of claim 1, wherein the uniform vacuum pressure of the vacuum bag in which the reinforcing fiber is laminated in the mold is further provided with a reverse vacuum by installing a tube and a valve for applying a vacuum pressure at a point other than the outlet. Process for manufacturing VARTM composites with a reverse vacuum system with minimal thickness change, obtained by application. The reverse vacuum system of claim 1 or 2, wherein the tube for applying a vacuum pressure to a point other than the outlet is installed at the inlet side. fair. The valve for applying the reverse vacuum is installed between the tube installed on the inlet side and the tube connecting the outlet side and the vacuum. Reverse vacuum system with minimal change in thickness VARTM composite material manufacturing process. The process of claim 1 or 2, wherein the pressure of the liquid polymer in the process is maintained at normal pressure. The process of claim 1 or 2, wherein the reverse vacuum is applied after complete impregnation of the liquid polymer. The polymeric fiber reinforced composite material obtained by any one of Claims 1-6.

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