JP4590803B2 - RTM molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an RTM molding method suitable for a relatively large FRP molding which can prevent the generation of an unimpregnated part, voids, etc., and secure good molding quality. SOLUTION: In the RTM molding method, a reinforcing fiber base material is arranged in a cavity, and a liquid resin is injected into the cavity and cured after the base material is impregnated with the resin. A plurality of openings for injecting the resin into the cavity are formed, and a detection part for detecting the presence of the injected resin is set in the cavity. The time of starting resin injection from each opening is controlled by a signal from the detection sensor of the detection part.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an RTM (resin transfer molding) molding method for molding an FRP (fiber reinforced plastic) structure, and more specifically, a plurality of resins when molding a relatively large FRP molded body. The present invention relates to an RTM molding method that provides an effective resin injection control method in which the timing of resin injection from each injection port is effectively achieved and an unimpregnated portion of resin is not generated.
[0002]
[Prior art]
Since FRP is lightweight and can exhibit high mechanical properties, FRP has begun to be studied as a constituent material for large planar bodies and structures.
[0003]
In general, when FRP is molded by an RTM molding method, a liquid resin is press-fitted into a reinforcing fiber base disposed in a cavity and impregnated and cured.
[0004]
In order to RTM-mold a large planar body or structure as described above, it is necessary to confirm that the press-fitted liquid resin has flowed through the reinforcing fiber base and reached a predetermined position. This is very important for efficiently forming a molded body without voids.
[0005]
When molding a large planar body or structure, the molding part can be decompressed through a plurality of vacuum suction ports, and a resin can be injected from the plurality of resin injection ports. The timing of resin injection start from a plurality of resin injection ports can be shifted, and the resins can be sequentially injected with a time difference.
[0006]
That is, the resin flow becomes nonlinearly slow as the flow resistance increases as the distance from the resin injection port increases. Therefore, by using a plurality of injection ports and starting a new resin injection, it is possible to sufficiently cope with a large molded article having a large area and a long length, and the resin can be impregnated in a relatively short time. It can be expected to ensure a good molding state without causing voids or the like due to resin impregnation leakage at each part.
[0007]
In addition, by appropriately arranging a plurality of vacuum suction ports and a plurality of resin injection ports, for example, a skin structure body having ribs locally even for a molded body having a relatively complicated shape or structure. Further, it is possible to appropriately cope with a skin structure having an opening portion (a perforated portion) in a part of the rib, a sandwich structure having a skin structure around the sandwich structure portion, and the like. Therefore, when RTM molding a large structure in particular, it is necessary to provide a plurality of resin injection ports and control the timing of resin injection from each injection port in a timely manner. It is extremely important to know.
[0008]
Conventionally, when molding a large molded body that requires a plurality of injection ports, a reinforcing fiber base material is placed in a lower mold, the cavity is covered with a transparent bagging film, and then the inside of the cavity is formed. Resin was sequentially injected from each injection port by vacuum suction. At that time, resin injection from each injection port was performed by properly seeing the flow of the flowing resin through the transparent bagging film. I went with the timing. However, in such observation of the resin flow state by human eyes, when the molded body is large, a place that is difficult to see occurs, or the position of the tip of the resin flow portion is misplaced, and the timing of resin injection is There is a problem that it may not be properly planned. Furthermore, in order to heat the entire mold with high-temperature hot air, as in the case of manufacturing a large molded body with high heat resistance using the above lower mold and bagging film, humans stay around the mold and cause resin flow. The problem is that the timing of resin injection from multiple ports cannot be achieved because the person cannot observe the resin flow state from the outside of the mold as in the case where it is not possible to confirm or when molding a relatively small molded body with a double-sided mold. is there. In such cases, the resin flow rate has been assumed so far, and the injection timing from each injection port has been attempted based on the feeling of human experience and the amount of resin prepared. However, such a method has a problem that the productivity is low because there is no certainty and the mass productivity is poor.
[0009]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to infer the flow state of the liquid resin by estimating the resin flow state from each injection port by inferring the flow state of the resin by human observation or experience. Thus, there is a need to provide an RTM molding method in which molding is performed so that an unimpregnated portion and voids are not formed on a base material by achieving an appropriate resin injection timing from each injection port.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention employs the following configuration. That is,
In an RTM molding method in which a reinforced fiber base material is disposed in a cavity, a liquid resin is injected into the cavity, and the resin flows and is impregnated into the reinforced fiber base material, the resin is placed in the cavity. A plurality of injection ports for injecting resin, and a detection unit for detecting the presence of the resin injected into the cavity are provided, and injection of resin from each injection port is started by a signal from the detection sensor of the resin detection unit It comprises an RTM molding method characterized in that the timing is controlled.
[0011]
Further, it is preferable to reduce the pressure in the cavity before starting the resin injection in order to suppress the generation of voids.
[0012]
In addition, the mold can be formed only by the lower mold, and the cavity can be formed by the lower mold and the bag material, so that a relatively large molded product can be easily manufactured. The resin is preferably a thermosetting resin. Furthermore, when the thermosetting resin is a polyamine curable epoxy resin, the moldability is good and the effect speed is fast.
[0013]
In addition, as the resin detection sensor, a first optical fiber having an emission surface for emitting light at or near the tip, and an incident surface for receiving light emitted from the first optical fiber as the tip or near the tip By using the liquid detection sensor comprising the second optical fiber, the resin can be detected in a pinpoint manner.
[0014]
Further, when a liquid detection sensor comprising a flexible dielectric circuit board that detects a change in dielectric constant is used as the resin detection sensor, the resin can be efficiently detected in a planar shape.
[0015]
In this RTM molding method for FRP large planar bodies and structures, a sheet-shaped resin diffusion passage forming member or a core material in which resin passage grooves are formed can be used, or both of them can be used. You can also.
[0016]
Thus, if a reinforcing fiber substrate and a sheet-like resin diffusion medium are used, a large planar body having an FRP skin structure can be formed, and if a core material having a resin passage groove is used, a so-called core material is formed. A large planar body or structure having an FRP sandwich structure can be formed.
[0017]
In the present invention, the effect can be obtained particularly when a sheet having a maximum length of 5 m or more is required, or when a sheet having a maximum width of 2 m or more is formed. This is the case. In addition, the area is particularly suitable when applied to the molding of FRP planar bodies of, for example, about 30 to 50 m ² .
[0018]
The reinforcing fiber substrate preferably includes a carbon fiber fabric. In particular, 90% or more is preferably a carbon fiber fabric. When it is in the form of a woven fabric, it is easy to handle even if it is a wide area and long, and high mechanical properties can be easily obtained by using a carbon fiber substrate. Carbon fiber fabrics include unidirectional fabrics (glass fibers and synthetic fiber yarns may be used for weft yarns), plain fabrics (including flat yarn fabrics), twill fabrics, knitted fabrics, multiaxial fabrics, tertiary Original fabric, 3D braid, etc. can be used.
[0019]
A plurality of the reinforcing fiber bases may be laminated. In this case, if the reinforcing fiber bases are partially fixed to each other, it is possible to perform shaping on the mold without causing a shift even in a wide area or a long one. For example, it is possible to arrange the laminated reinforcing fiber base material on the mold surface in a state of being fixed in at least one place in the thickness direction. As a fixing method, heat fusion or thermosetting using a stitch or a fixing agent (thermoplastic particles, synthetic fibers, thermosetting resin spray, etc.) may be employed.
[0020]
As the thermosetting resin used as the matrix resin, a high heat resistant resin having a glass transition temperature of 100 ° C. or higher is preferably used. In order to obtain good diffusion and impregnation properties, it is preferable to use a thermosetting resin having a viscosity at the mold temperature of molding of 5 poises or less. As such a high heat resistance resin, for example, a high heat resistance thermosetting resin such as an epoxy resin, a bismaleimide resin, a curable polyimide resin or a phenol resin can be used.
[0021]
Moreover, when using a core material, it is preferable to use the heat resistant core material whose shrinkage rate is 5% or less when a vacuum pressure acts in a 100 degreeC heating state, for example. As such a core material, for example, a heat-resistant core material such as a foam core or a balsa core made of vinyl chloride or polymethacrylimide can be used.
[0022]
It is also possible to employ a condition (step cure) in which the resin injection, impregnation temperature and resin curing temperature are separated by 20 ° C. or more. In order to ensure good diffusion and impregnation properties, it is preferable to use a thermosetting resin having a viscosity of 300 cp or less at the mold temperature when the matrix resin is injected.
[0023]
Further, the resin can be injected while raising the temperature of the mold with hot air, and the molding cycle can be shortened to perform more efficient molding for mass production.
[0024]
With respect to the injection temperature and the curing temperature, for example, it is possible to adopt a form in which the resin injection is started when the temperature of the mold is 100 ° C. or lower and the resin is cured at 100 ° C. or higher.
[0025]
By properly controlling the timing of resin injection from a plurality of resin injection ports while vacuuming and reducing the pressure inside the cavity, the injection resin can be reliably distributed over a wide area while ensuring good diffusion and impregnation. As a result, it is possible to obtain a high-quality large-sized molded product having a void generation rate of the molded body of 0.2% or less.
[0026]
The method of heating a large mold is lower in capital investment and more efficient in heating energy than the conventional method of heating a mold through a heating medium such as hot water or steam in a pipe provided in the mold. Is.
[0027]
For the heating by the hot air, a hot air circulation type heating oven, a local exhaust type hot air generator (air blow by a blower), or the like can be used. The temperature variation of the hot air is preferably within ± 5 ° C.
[0028]
In addition, from shaping to demolding can be performed at the same place, and heating to a predetermined temperature can be performed quickly using hot air to heat the entire mold and molded part, so the molding cycle is shortened and extremely high molding efficiency is achieved. Can be achieved. Therefore, excellent mass productivity is achieved at the same time.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with preferred embodiments with reference to the drawings. FIG. 1 shows a method for manufacturing an FRP large planar body according to an embodiment of the present invention. It is the top view which looked down at the shaping | molding die from upper direction.
[0030]
The reinforcing fiber base 2 was disposed on the molding surface of the mold 1 and a plurality of resin injection lines A1 to A4 were disposed at predetermined intervals. A vacuum suction line B is disposed at the end of the substrate facing the first resin injection line A1, and the entire reinforcing fiber substrate 2 including the resin injection lines A1 to A4 and the vacuum suction line B is covered with the bag material 3. Covered. Resin detection sensors C1 to C4 that detect the resin flow are disposed on the upper surface of the reinforcing fiber base at the tip of the resin injection line other than the first resin injection line Al.
[0031]
Furthermore, in order to increase the fluidity of the resin, a resin diffusion medium having a resin flow resistance of 1/10 or less than that of the reinforcing fiber base is inserted through the release woven fabric, including the resin detection sensor C, and the reinforcing fiber base. It is disposed on the upper surface (the resin diffusion medium and the release fabric are not shown).
[0032]
And it bagged with the bag material 3 so that the whole might be covered from the top. The bag 3 and the mold 1 are sealed with an adhesive double-sided sealing tape (not shown). This double-sided seal tape communicates with the resin injection line Al and the vacuum suction line B, and is also used for sealing the tube 1 extending to the outside of the bag material 3 and the molding die 1 of the codes of the resin detection sensors C1 to C4.
[0033]
As described above, various materials are arranged in a mold, and the bag material 3 is bagged, and then the entire bag is vacuum-sucked by the vacuum pump 5 through the vacuum trap 4 communicating with the vacuum line B. Of course, in that case, all the valves (D1 to D4) provided in the middle of the tubes communicating from the resin injection lines A1 to A4 are kept closed.
[0034]
Thereafter, hot air for heating is generated by an oven (not shown), and the entire mold is heated to a predetermined temperature. Each surface temperature is always clearly detected by a temperature sensor (not shown) installed on the mold surface or the reinforcing fiber base surface.
[0035]
When the temperature reaches a predetermined temperature, the first valve D1 is first opened to inject a predetermined resin from the resin tank E1 into the first resin injection line Al. Thereafter, the resin flowing out from the first resin injection line Al flows in the resin diffusion medium toward the vacuum suction line B located at a position opposite to the first resin injection line Al. The resin flowing on the surface of the reinforcing fiber base with the resin diffusion medium eventually flows into the reinforcing fiber base and is impregnated. However, the resin flows toward the second resin injection line A2, but since the resin flows in the already-impregnated resin diffusion medium and the reinforcing fiber base, the resin flow resistance gradually increases and the flow rate becomes nonlinear. It will drop to.
[0036]
Therefore, before reaching the time of the pot life of the resin, the resin does not pass through the impregnated portion and the resin flow resistance is not yet high, that is, here, a new resin injection is performed from the second resin injection line A2. There will be a need to start.
[0037]
The problem here is when the valve D2 for injecting the resin into the second resin injection line A2 is opened. In order to accurately control the timing, the resin detection sensor C2 accurately recognizes when the resin flows at a predetermined position. When the sensor C2 recognizes the timing of injecting the resin into the second resin injection line A2, the second valve D2 is opened to inject new resin from that position. Then, the injection of the resin from the first resin inflow line A1 is stopped by closing the valve A1 there. Eventually, the resin injected from the second resin injection line A2 flows toward the next third resin injection line A3. Thereafter, this is repeated. When the resin finally reaches the vacuum suction line B, the resin flowing out to the last resin injection line is stopped by closing the valve there.
[0038]
When all the reinforcing fiber bases are impregnated with the resin, the resin is cured at a predetermined temperature and time. After that, all auxiliary materials such as the resin material used for the resin diffusion medium and the resin injection line are removed from the molded product surface together with the bag material 3 and the release woven fabric, and finally the molded product is removed from the mold surface. To do.
[0039]
The obtained molded product is after-cured at a predetermined temperature and time as required.
[0040]
In the present invention, the cavity is a molding portion where a molding substrate is disposed. For example, FIG. 1 shows the inside of the bag material 3, and FIG. 4 shows a space portion formed by the upper mold and the lower mold in which the core 44 and the base material 43 are arranged.
[0041]
The valve opening / closing operation may be any of mechanical, electrical, and manual. Usually, it is performed manually, but it can be mechanically operated by receiving an electrical signal during mass production.
[0042]
【Example】
[Example 1]
The mold 1 shown in FIG. 1 is a FRP mold having a length of 21 m and a width of 2.5 m. Although not shown in the figure, the entire mold is in a simple molding chamber (length 25 m, width 3, 5 m, height 2 m) formed entirely by a heat insulating material, and a hot air generator provided outside the molding chamber More hot air can heat the entire mold. The hot air is circulated so that it returns. The reinforcing fiber base material used here is a carbon fiber fabric “Torayca” T700 plain weave (200 g / m ² basis weight) manufactured by Toray Industries, Inc., and a total of 16 PLY is arranged.
[0043]
The resin is Toray Industries, Inc. polyamine curable epoxy resin: TR-C32, and the viscosity characteristics are as shown in Table 1. The graph shown in FIG. 2 is obtained by measuring changes in viscosity at 70 ° C. and 80 ° C. using an E-type viscometer manufactured by Toki Sangyo Co., Ltd .: TVE-30 type.
[0044]
A polyethylene mesh fabric (# 200 mesh) having a resin flow resistance of 1/10 or more lower than that of the reinforcing fiber base is disposed on the reinforcing fiber base 2 through a nylon woven fabric for release. And used as a resin diffusion medium. A resin detection sensor was fixed at a predetermined position above it. Further, the whole of the reinforcing fiber base material and auxiliary materials was covered with a bagging film. The bagging film and the mold surface were sealed with a synthetic rubber and a highly adhesive seal tape.
[0045]
As shown in the figure, four resin injection lines are provided, and the pitch is 5 m. And the resin detection sensor which detects resin flow is arrange | positioned in the vicinity of about 100 mm from this resin injection line. It is also installed at two locations in the width direction in order to reduce the error of resin flow detection in the width direction.
[0046]
The resin detection sensor applied there is a plastic optical fiber sensor described in Japanese Patent Application Laid-Open No. 2001-27678. In the sensor, the first optical fiber and the second optical fiber are adjacent to each other, the exit surface of the first optical fiber and the incident surface of the second optical fiber are inclined, and the inclined surface is provided. It is possible to determine the presence or absence of liquid by having a configuration in which they face each other.
[0047]
In this optical fiber, the coated portion is fused and formed into a saddle shape to make it twin. Further, two single optical fibers may be bonded using an adhesive and adjacent to each other. Further, a single optical fiber may be arranged in parallel without being bonded, but a mechanism that does not rotate the fiber tip is required.
[0048]
By detecting the presence or absence of the liquid material from the change in the emitted light or scattered light at the two adjacent optical fiber tips, there is no need for a fixture for the optical fiber or the swelling material. There is no hindrance.
[0049]
As the resin detection sensor, various sensors other than the optical fiber can be applied. As one of them, a dielectric sensor 30 as shown in FIG. 3 can be applied. This sensor is a circuit in which a comb-like circuit 32 made of conductive silver paste (dortite) is faced on a flexible base substrate 31 (for example, a polyimide thin plate; 0.2 to 0.4 mm). When the resin flows in and is immersed, the electrostatic capacity (capacitance) changes according to the immersion area, so that the resin immersion position can be read.
[0050]
After the bagging is completed, the entire mold is covered with a heat insulating box (not shown in the figure) composed of a heat insulating panel, and hot air having a temperature of 80 ° C. is supplied from one side in the longitudinal direction with a hot air generator. A circulation system was used that sprayed inside and exhausted from the back to return to the original hot air generator. At the same time, the pressure in the bagged cavity was started to be reduced from the vacuum suction line B, and the pressure was reduced to 10 Torr or less before the mold temperature reached 80 ° C.
[0051]
Next, resin injection was started when the mold temperature almost reached 80 ° C. First, the valve D1 provided in the middle of the tube communicating with the first resin injection line A1 was opened, and the resin was injected from the resin container E1 into the first resin injection line A1 with vacuum pressure. The injected resin is impregnated in the reinforcing fiber base while flowing in the resin diffusion medium having low flow resistance. However, as the resin flow approached the second resin injection line A2, the flow rate decreased nonlinearly. This is because the flow resistance is gradually increased because the resin already immersed in the resin diffusion medium is boosted or sent in such a manner as to overtake the resin.
[0052]
Considering the resin gelation time, the time for the resin to flow at a high temperature is limited. Therefore, it is necessary to stop the injection of the resin decelerated extremely and to newly inject from a position with a low flow resistance. The position set in consideration of the limit time and position is the position of the second and subsequent resin injection lines.
[0053]
Therefore, when the resin injected from the first resin injection line A1 reaches the second resin injection line A2, the valve D2 is opened from the second resin injection line A2 to start injection. At this time, the resin detection sensor C2 installed 100 mm behind the second resin injection line A2 recognizes that the resin has reached the second resin injection line A2. Thus, the position where the resin detection sensor is installed is preferably near the new resin injection position, but there is no problem if it is just before the new resin injection position (for example, 50 to 100 mm).
[0054]
The resin injected from the second resin injection line A2 eventually reached the third resin injection line A3, but the subsequent treatment is exactly the same as the method for the second resin injection line A2.
[0055]
Finally, when the resin injected from the fourth resin injection line A4 reached the vacuum suction line B provided at the outermost end, the resin injection from the fourth resin injection line A4 was also stopped.
[0056]
Thereafter, vacuum suction was continued for about 30 minutes, and then the valve D5 of the suction part was closed. This time it was an epoxy resin that did not contain a solvent, but when using a thermosetting resin that contains a volatile solvent, it is preferable to continue vacuum suction after resin impregnation throughout the area in order to prevent voids. .
[0057]
[Example 2]
As another embodiment of the present invention, an example of RTM molding according to the present invention using a double-sided mold 40 in which the flow state of the resin cannot be seen at all will be described with reference to FIG. 4 (longitudinal sectional view of the mold).
[0058]
In FIG. 4, a reinforcing fiber base 43 (Toray Industries, Ltd. “TORAYCA” T300 × 200 g / m ² ) is formed around the entire circumference of the foam core 44 in a cavity formed in the center of a metal upper die 41 and a lower die 42. A fabric with a plain fabric with a weight of 2 ply) was installed. Among them, the foam core 44 is a heat-resistant hard polyurethane (expanding ratio is 20 times, size is 12 mm, length is 2.5 m, width is 1.2 m) and has a narrow groove (width 1) as a resin flow path in the longitudinal direction. 0.5 mm, depth 2.5 mm, and pitch 15 mm) are communicated on both sides and side surfaces. However, in the center of the upper surface, a wide groove (width 4 mm, depth 4 mm) in the width direction is processed into a line shape so as to communicate with the groove in the longitudinal direction.
[0059]
The resin injection port is provided with a central portion of the upper mold 41 and a linear groove 45 extending in the width direction on both sides in the longitudinal direction. However, the line-shaped grooves 45 extending in the width direction on both sides also serve as an initial vacuum suction line.
[0060]
In the resin detection sensor, the dielectric sensor 30 shown in FIG. 3 is provided on the surface of the lower mold 42 at three locations, the center portion and both end portions.
[0061]
The applied resin is the same Toray Co., Ltd. polyamine curable epoxy resin: TR-C32 as in Example 1.
[0062]
Both the upper and lower molds are heated to 70 ° C., and vacuum suction is started from the vacuum suction lines 45 on both sides. When the degree of vacuum falls below 5 torr, the vacuum suction line 45 is closed and resin injection is started from the central resin injection port 46. At this time, the discharge pressure of the resin is set at a relatively low pressure of 2 kg / cm ² so that the base material is not disturbed by the dynamic pressure of the resin. The injected resin flows into the groove in the width direction provided in the center of the upper surface of the core 44 through the reinforcing fiber base 43 and eventually flows in the direction of both ends while flowing into the narrow groove in the longitudinal direction. The resin impregnates the substrate while flowing through the narrow groove. Eventually, both ends turn and flow to the bottom side. Resin injection is started from the resin injection lines 45 on both sides when the inductive sensors (G1, G3) arranged near both ends on the lower surface side catch the fact that they have flowed to the lower surface. Eventually, when it is detected that the resin has reached the center of the lower surface, the pressure of the resin injected from the resin injection lines 45 on both sides is increased to 5 kg / cm ² and held until cured. In this way, when cured while applying a relatively high resin pressure, the surface pinholes and voids are filled with the applied pressure and eliminated, and the shrinkage due to resin curing shrinkage is improved, and a good design surface is obtained. It is done.
[0063]
In addition, the curing process can be monitored even after the resin injection is completed by the dielectric sensor. In particular, the time difference in curing between the center and both ends was read in detail.
[0064]
【The invention's effect】
As described above, according to the RTM molding method of the present invention, when a plurality of resin injection ports and lines are used, even if the resin flow state is not visible, by using a resin detection sensor arranged at a key point, It is possible to accurately recognize whether or not the resin flows at a key point, and to achieve the timing of resin injection from the resin injection portion. As a result, it is possible to obtain a high-quality FRP molded product without generation of unimpregnated portions and voids.
[0065]
Such an RTM molding method according to the present invention is suitable for manufacturing a relatively large molded product. For example, wing-like members (wind turbine wings) and railways such as automobile outer plate members and primary structural materials, primary structural materials (fuselage, main wing, tail wing) as aircraft members, secondary structural members (fairing and control surface) A vehicle structure or the like is preferable.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an RTM molding method according to Embodiment 1 of the present invention.
FIG. 2 is a viscosity characteristic diagram of an epoxy resin used in an example of the present invention. FIG. 3 is a schematic configuration diagram of a dielectric sensor used in Example 2.
FIG. 4 is a schematic configuration diagram showing an RTM molding method according to a second embodiment of the present invention.
[Explanation of symbols]
1: Mold 2, 43: Reinforcing fiber base material 3: Bag material 4: Vacuum trap 5: Vacuum pump A1-A4: Resin injection line B: Vacuum suction line C2-C4: Resin detection sensors D1-D5: F1-F3 , Valves E1 to E4: resin containers G1 to G3: induction sensor 30: induction sensor 31: base substrate 32: comb circuit 40: mold 41: upper mold 42: lower mold 44: foam core 45: vacuum suction line / resin Injection line 46: Resin injection port 47: O-ring for sealing

Claims (8)

In an RTM molding method in which a reinforced fiber base material is disposed in a cavity, a liquid resin is injected into the cavity, and the resin flows and is impregnated into the reinforced fiber base material, the resin is placed in the cavity. A plurality of injection ports for injecting the resin are provided, a detection unit for detecting the presence of the injected resin is provided in the cavity, and a resin from the detection sensor of the resin detection unit is used to inject the resin from each injection port. An RTM molding method characterized in that the start time is controlled. 2. The RTM molding method according to claim 1, wherein the pressure in the cavity is reduced before resin injection is started. The RTM molding method according to claim 1, wherein the cavity is formed of a lower mold and a bag material. The RTM molding method according to claim 1, wherein the injected resin is a thermosetting resin. The RTM molding method according to claim 4, wherein the thermosetting resin is a polyamine curable epoxy resin. 6. The RTM molding method according to claim 1, wherein the entire molding die including the cavity is heated to a predetermined temperature with hot air. The detection sensor of the resin detection unit includes a first optical fiber having an emission surface for emitting light at or near the tip, and an incident surface for receiving light emitted from the first optical fiber at the tip or tip. The RTM molding method according to any one of claims 1 to 6, wherein the RTM molding method is a detection sensor for liquid detection including a second optical fiber in the vicinity. The RTM molding method according to claim 1, wherein the detection sensor of the resin detection unit is a detection sensor for liquid detection including a flexible dielectric circuit board that detects a change in dielectric constant. .

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