Manufacturing method for composite materials

Abstract

OoA molding is performed with a simple configuration. [Solution] A method for molding a composite material comprises: a first placement step of covering a composite material placed in a mold with a first bag; a second placement step of placing a jig that locally contacts the composite material on the composite material via the first bag, and covering the first bag and the jig with a flexible second bag; a depressurization step of reducing the pressure in a first region covered by the first bag and a second region between the first bag and the second bag; a heating step of heating the composite material after the depressurization step; a first opening step of opening the depressurized second region to the atmosphere after the heating step; and a second opening step of lowering the temperature of the composite material and opening the first region to the atmosphere after the first opening step.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for producing a composite material.

BACKGROUND ART

[0002] As a composite material production technique, OoA (Out of Autoclave) molding that does not use an autoclave is known (see, for example, Patent Document 1). In general, while OoA molding has higher productivity than autoclave molding, it tends to have higher porosity and relatively lower molding quality.

[0003] As a type of OoA molding, there is a molding method called DVD (Double Vacuum Debulking) that enables high-quality molding. In the DVD method, a laminate (molded article) is covered with a double vacuum bag, so that the laminate is placed in a reduced pressure environment without being excessively pressed. Therefore, a degassing circuit for discharging trapped air and water vapor in the laminate to the outside is maintained. As a result, when the outer bag is opened to the atmosphere, voids in the laminate are crushed by the inner bag. As a result, the DVD method enables high-quality molding even though it is OoA molding.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] However, in the DVD method, the outer bag needs to be able to maintain the internal reduced pressure space so as not to press the laminate. Therefore, when molding a relatively large product, a heavy and robust outer bag that can withstand the internal and external pressure difference is required. This invention has been made in view of the above circumstances, and aims to perform OoA molding with a simple configuration. [Means for solving the problem]

[0006] To achieve the above objective, one embodiment of the present invention is a method for manufacturing a composite material, The first placement step involves covering the composite material placed in the mold with a first bag, A second arrangement step involves placing a jig that makes local contact with the composite material on the composite material via the first bag, and covering the first bag and the jig with a flexible second bag. A depressurization step of reducing the pressure in the first region covered by the first bag and the second region between the first bag and the second bag, After the depressurization step, a heating step is performed to heat the composite material, After the heating step, a first opening step is performed to open the depressurized second region to the atmosphere, After the first opening step, a second opening step is performed to lower the temperature of the composite material and open the first region to the atmosphere, It is equipped with. [Effects of the Invention]

[0007] According to the present invention, the composite material is heated while being locally pressed by a jig. Therefore, the composite material can be pressed while maintaining a degassing circuit that releases expanded trap air, water vapor, and other gases to the outside. In other words, it is possible to suitably discharge gases to the outside while maintaining the degassing circuit without the need to use a heavy outer bag that retains the internal space. Thus, OoA molding can be suitably achieved with a simpler configuration compared to conventional methods. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a molding apparatus according to an embodiment. [Figure 2] This is a perspective view showing a pressing jig according to an embodiment. [Figure 3] This is a flowchart showing the flow of the molding method according to the embodiment. [Figure 4] This is a diagram illustrating the molding method according to the embodiment. [Figure 5] This is a diagram illustrating the molding method according to the embodiment. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings.

[0010] [Configuration of the molding machine] Figure 1 shows a molding apparatus 1 according to this embodiment. Note that only the left half of the molding apparatus 1 is shown in Figure 1. The molding apparatus 1 is used for a molding method called DVD (Double Vacuum Debulking), which is an Out of Autoclave (OoA) molding method that does not use an autoclave and uses a double vacuum bag. Specifically, as shown in Figure 1, the molding apparatus 1 molds (shapes) the composite material 20 to be molded into the desired shape by heating and pressurizing the composite material 20 to be molded in a heating device 50 (e.g., an oven) and curing it.

[0011] The composite material 20 in this embodiment is a laminate formed by stacking sheet-like prepregs 21. The prepreg 21 is a fibrous base material that has been pre-impregnated with an uncured resin. Note that in Figure 1, the release film, breather, etc., are omitted from the illustration.

[0012] The composite material 20 is placed on the mold 31. The portion of the upper surface of the mold 31 on which the composite material 20 is placed becomes a molded surface 31a formed into a desired molded shape. The composite material 20 placed on the mold 31 is double-covered by a flexible inner bag 32 and an outer bag 33.

[0013] The inner bag 32 is the first bag according to the present invention, and directly covers the composite material 20 and auxiliary materials required for lamination (such as release film, breather, etc.). The inner bag 32 is brought into close contact with the molding die 31 via the first seal 35 (for example, a sealant tape) on the outer peripheral side of the composite material 20. Thereby, the inner bag 32 defines an inner region R1 which is a sealed space between the inner bag 32, the first seal 35 and the molding die 31, and hermetically encloses the composite material 20 inside the inner region R1.

[0014] The outer bag 33 is the second bag according to the present invention, is arranged to cover the entire inner bag 32, and has flexibility. The outer bag 33 is brought into close contact with the molding die 31 via the second seal 36 (for example, a sealant tape) on the outer peripheral side of the inner bag 32. Thereby, the outer bag 33 defines an outer region R2 which is a sealed space between the inner bag 32, the second seal 36 and the molding die 31. Note that the contact position between the outer bag 33 and the molding die 31 is not limited to a position on the outer peripheral side of the inner bag 32. For example, a sealant tape may be placed on the inner bag 32, and the outer bag 33 may be brought into close contact with the inner bag 32 on that position.

[0015] The inner region R1 and the outer region R2 are connected to a vacuum pump so that vacuuming (pressure reduction) can be performed individually. Specifically, the inner region R1 is connected to the vacuum pump P1 via a valve V1 by a pipe. The outer region R2 is connected to the vacuum pump P2 via a valve V2 by a pipe. Thereby, the inner region R1 and the outer region R2 are configured such that vacuuming (pressure reduction) to a desired degree of vacuum and venting to the atmosphere can be performed individually. Note that the vacuum pumps P1 and P2 may be shared for the inner region R1 and the outer region R2.

[0016] A pressing jig 40 that presses the composite material 20 is arranged in the outer region R2. As shown in FIG. 2, the pressing jig 40 is arranged on the composite material 22 with the inner bag 32 (not shown) interposed therebetween. The pressing jig 40 of the present embodiment is a so-called expanded mesh (expanded metal), and is formed into a three-dimensional rhombic mesh shape by making staggered cuts in a metal material and stretching the material. In the pressing jig 40, each vertex 41 of the plurality of rhombuses comes into point-to-point contact with the composite material 20 via the inner bag 32 at multiple points. It should be noted that the pressing jig 40 only needs to be in local contact with the composite material 20 via the inner bag 32 in a reduced pressure environment (in a vacuum). In other words, as will be described later, the pressing jig 40 may be in contact with the composite material 20 such that portions of the composite material 20 that do not contact the pressing jig 40 form a deaeration circuit that allows internal gas to escape to the outside (outer peripheral portion). However, the deaeration circuit is preferably formed comprehensively over the entire surface of the composite material 20. Further, in the example of Fig. 2, the pressing jig 40 is not arranged on the peripheral edge of the upper surface of the composite material 20, but the range of the pressing jig 40 arranged on the composite material 20 is not particularly limited. The pressing jig 40 may be arranged over the entire surface of the composite material 20.

[0017] [Molding Method] Fig. 3 is a flowchart showing the flow of the molding method for the composite material 20 using the molding apparatus 1, and Figs. 4 and 5 are diagrams for explaining this molding method. In Figs. 4 and 5, the composite material 20 in a plan view is shown on the upper side, and the composite material 20 and the like in a side view are shown on the lower side.

[0018] As shown in Fig. 3, first, in the heating device 50, the worker places the composite material 20 on the molding die 31, and covers the composite material 20 with the inner bag 32 (Step S1: first placement step). The worker brings the inner bag 32 and the molding die 31 into close contact with each other around the composite material 20 by the first seal 35, and seals the inner side. Next, the worker places a pressing jig 40 that makes local contact with the composite material 20 on the composite material 20 via the inner bag 32, and covers the inner bag 32 and the pressing jig 40 with the outer bag 33 (Step S2: Second placement step). The worker then uses the second seal 36 to tightly seal the outer bag 33 and the mold 31 on the outer circumference side of the first seal 35, sealing the inside. As a result, the composite material 20 is double-covered by the inner bag 32 and the outer bag 33. Alternatively, the composite material 20 on the mold 31 may be covered with the inner bag 32 and outer bag 33 outside the heating device 50, and then placed inside the heating device 50.

[0019] Next, the operator drives vacuum pumps P1 and P2 to evacuate (reduce pressure) the inner region R1 covered by the inner bag 32 and the outer region R2 between the inner bag 32 and the outer bag 33 to a predetermined vacuum level (step S3: depressurization step). At this time, the pressing jig 40 in the outer region R2 presses the composite material 20 at multiple points with multiple vertices 41 via the inner bag 32.

[0020] Next, the operator drives the heating device 50 to heat the composite material 20 (Step S4: Heating step). Here, the composite material 20 is heated to, for example, over 100 degrees Celsius. At this time, as the temperature of the composite material 20 rises, the trapped air and water vapor (moisture-absorbing water) inside the composite material 20 expand. However, as shown in Figure 4, the pressing jig 40 that presses the composite material 20 locally presses the composite material 20 at multiple vertices 41. Therefore, the parts of the composite material 20 that correspond to the parts other than the vertices 41 of the pressing jig 40 function as a degassing circuit that releases the expanded water vapor and other gases G to the outside, as illustrated by the arrows in Figure 4. This allows the gases G to be suitably discharged to the outside.

[0021] Next, the operator operates the vacuum pump P2 and valve V2 to release the outer region R2 inside the outer bag 33, which had been depressurized, to the atmosphere (Step S5: First release step). As a result, as shown in Figure 5, the composite material 20 is pressed (pressurized) over its entire surface by the inner bag 32. Therefore, the voids remaining after the gas G is discharged in step S4 are compressed as a vacuum, and the composite material 20 hardens appropriately.

[0022] Next, the worker stops the heating device 50 to lower the temperature of the composite material 20, and operates the vacuum pump P1 and valve V1 to open the inner region R1 to the atmosphere (step S6: second opening step). Then, the worker removes the composite material 20 after the temperature has dropped sufficiently. Note that the timing of opening the inner bag 32 to the atmosphere depends on the material, so in this step, it is sufficient for the composite material 20 to be debugged (removed from the bag material) and removed after it has hardened. Thus, the molding (shaping) of the composite material 20 is completed.

[0023] [Technical effects of this embodiment] As described above, according to this embodiment, the composite material 20 is heated while being locally pressed by the pressing jig 40. Therefore, the composite material 20 can be pressed while maintaining a degassing circuit that releases expanded trap air, water vapor, and other gases G to the outside. In other words, it is possible to maintain the degassing circuit and expel gases G to the outside without the need to use a heavy outer bag that holds the internal space. Furthermore, since the burden on the molding jig, including the pressing jig 40, is reduced, the DVD method, which was previously used mainly as a repair method for small areas, can be suitably used for molding large parts as well. In addition, since the pressing jig 40 does not have resin adhering to it, it can be reused, and the cost of auxiliary materials can be reduced. Therefore, OoA molding can be suitably achieved with a simpler configuration compared to conventional methods.

[0024] Furthermore, according to this embodiment, the prepreg 21 used as the composite material 20 does not need to be for OoA molding. In other words, conventional OoA molding sometimes used prepregs for OoA molding that partially contained dry areas not impregnated with resin. More specifically, prepregs for OoA molding have internal cavities during lamination, but during molding, bagging creates a vacuum inside the cavities, and as the temperature rises during curing, the resin viscosity decreases, and the entire prepreg is impregnated with resin. In this type of prepreg for OoA molding, the resin impregnates the vacuum-sealed space, so no voids are left behind. In other words, the porosity does not increase even without pressurization. However, commercially available prepregs for OoA molding are limited in terms of fiber and resin combinations, and sometimes other properties had to be compromised when selecting one. In this embodiment, it is not necessary to use a prepreg for OoA molding as the composite material 20, and high-quality molding can be achieved using any material.

[0025] Furthermore, according to this embodiment, the pressing jig 40 makes multi-point contact with the composite material 20 via the inner bag 32. As a result, a degassing circuit that releases internal gas G to the outside during heating is comprehensively formed across the entire surface of the composite material 20. Consequently, the composite material 20 can be cured effectively across its entire surface.

[0026] [others] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. For example, in the molding method of the above embodiment, after opening the outer region R2 to the atmosphere in step S5, physical surface pressure may be applied to the composite material 20 by placing a roller on it. This can further crush voids and improve molding quality.

[0027] Furthermore, the molding method of the above embodiment can be performed in the same way as the conventional DVD method without using the pressing jig 40. Furthermore, details shown in the above embodiments can be modified as appropriate without departing from the spirit of the invention. [Explanation of Symbols]

[0028] 1 Molding equipment 20 Composite materials 21 Prepreg 31 Molding mold 32 Inner bag (first bag) 33. Outer bag (second bag) 40 Pressing jig 41 vertices 50 Heating device R1 Inner area (1st area) R2 outer area (second area)

Claims

1. The first placement step involves covering the composite material placed in the mold with a first bag, A second arrangement step involves placing a jig that makes local contact with the composite material on the composite material via the first bag, and covering the first bag and the jig with a flexible second bag. A depressurization step of reducing the pressure in the first region covered by the first bag and the second region between the first bag and the second bag, After the depressurization step, a heating step is performed to heat the composite material, After the heating step, a first opening step is performed to open the depressurized second region to the atmosphere, After the first opening step, a second opening step is performed to lower the temperature of the composite material and open the first region to the atmosphere, A method for manufacturing composite materials.

2. The jig makes multi-point contact with the composite material via the first bag. A method for producing a composite material according to claim 1.

3. The aforementioned composite material is a laminate formed by stacking sheet-like prepregs. A method for producing a composite material according to claim 1.

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