JPH0579208B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a method of heating and curing fiber-reinforced plastic as a resin-based composite material for, for example, an aircraft using microwaves. (Prior art) Resin-based composite materials are generally heat-cured in an autoclave (for example, Japanese Patent Laid-Open No. 58
-62018) may be performed by microwave irradiation instead of heating in an autoclave. (Problems to be Solved by the Invention) However, heating and curing due to heat generated by microwave irradiation tends to cause uneven burns on the composite material due to the electromagnetic nature of the microwave. Even if a turntable, mode stirrer, etc. are used to prevent this, it is difficult to uniformly heat the composite material. In cases where uniform heating and curing are required, such as resin-based composite materials, uneven tanning must be avoided at all costs. An object of the present invention is to provide a method that can uniformly heat and harden fiber-reinforced plastics using microwave irradiation. (Means for Solving the Problems) According to the method of heating and curing fiber-reinforced plastic using microwaves of the present invention, a fiber-reinforced plastic molded product is abutted and fixed in a formwork made of a material that generates heat with microwaves. Then, both the molded product and the mold are irradiated with microwaves, and the molded product is heated and cured while also generating heat in the mold. Further, in the present invention, in the above method, after irradiating the microwave for a predetermined time, the microwave irradiation is performed a plurality of times at intervals with a lower output. (Function) Microwave irradiation causes the fiber-reinforced plastic molded product to internally generate heat, while the formwork surrounding it also generates internal heat, and that heat is transferred from the outside to the molded product. Good heat transfer is achieved due to the contact between the mold and the molded product. In this way, the temperature of the molded product, which receives heat from the inside and outside, is raised uniformly by microwave irradiation, and uneven burns do not occur. (Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 3 shows a heart section stringer panel 1 for an aircraft component as an example of a fiber-reinforced plastic material treated by the heating and curing method of the present invention. This panel 1 is integrally formed from a flat plate part 2 and a raised strip part 3 with a trapezoidal cross section. Each raised strip 3 is hollow and has an internal space 4 . The panel 1 is made of, for example, Kevlar fiber-reinforced epoxy resin prepreg, silicon carbide fiber-reinforced epoxy resin prepreg, or the like. In order to heat and harden the panel 1 described above as an example, the panel is placed in a jig or formwork 6 and fixed as shown in FIG. The formwork 6 is
For example, it can be a split mold consisting of a lower mold 6a and an upper mold 6b. In the illustrated example, the lower die 6a is
As shown in FIG. 2, a support surface 7 on which the flat plate portion 2 of the panel 1 is placed and accommodated, and positioning protrusions 8 on both side edges;
It has a groove 9 for receiving the raised strip 3 of the panel 1. When the panel 1 is positioned and housed in the lower mold 6a as shown in FIG. 1, and the upper mold 6b is placed on the lower mold 6a, the panel 1 is fixed while coming into contact with the inner surface of the mold 6. Both the upper mold 6b and the lower mold 6a of the formwork 6 are made of substantially the same material as the panel 1 to be heated and cured. The formwork 6 can be made of, for example, Kevlar fiber-reinforced epoxy resin prepreg or silicon carbide fiber-reinforced epoxy resin prepreg. On the other hand, it is preferable that the internal space 4 of the raised strip 3 of the panel 1 is filled with a radio wave transmitting material 10 before the panel is set in the formwork 6 as shown in FIG. After setting the panel 1 in the formwork 6 in the state shown in FIG. 1, the panel is housed together with the formwork in a microwave irradiation device (microwave oven) and irradiated with microwaves. The microwave irradiation device may be of an oven type or a waveguide type. By microwave irradiation, the temperature of the fiber-reinforced plastic heart section stringer panel 1 increases due to internal heat generation. On the other hand, since the frame 6 housing the panel 1 is also made of the same material as the panel, it similarly generates internal heat and rises in temperature, and the heat is transferred to the panel. This results in
Since the panel 1 generates heat from the inside and is given heat from the outside, the temperature rises uniformly and there is no uneven burning. FIG. 4 shows an example of the temperature rise of the formwork 6 during microwave irradiation. Note that the parameter is the microwave irradiation output (kw). Microwave irradiation is performed so that the output changes with time as shown in FIG. That is, as shown in the figure, irradiation is performed continuously for, for example, the first 40 minutes, and then irradiation is performed intermittently for 10 minutes at a lower output than the first irradiation with a 2-minute pause. Due to such intermittent microwave irradiation, the panel exhibits temperature changes as shown in FIG. In the figure, K indicates the case of Kevlar fiber epoxy resin prepreg, and Si indicates the case of silicon carbide fiber reinforced epoxy resin prepreg. FIG. 7 shows the progress of curing by microwave irradiation, and FIG. 8 shows changes in the curing rate similarly to FIG. 7. The microwave output does not necessarily have to be changed as shown in FIG. A temperature sensor capable of measuring temperature even in an electromagnetic field is inserted into the microwave irradiation device, and the output of the microwave is changed in accordance with the detected value of the sensor. In any case, changing the microwave output or turning it on/off promotes the movement of heat generated by internal heat generation, equalizes the temperature rise, and maintains a uniform constant temperature. The following table shows a comparison between conventional autoclave molding and microwave irradiation molding. In addition,
In this table, SiCF/EPOXY refers to silicon carbide fiber reinforced epoxy resin prepreg, and KF/EPOXY refers to silicon carbide fiber reinforced epoxy resin prepreg.
EPOXY means Kevlar fiber reinforced epoxy resin prepreg.

【table】

〔Effect of the invention〕

According to the present invention, the molded product is fixed in contact with the mold and irradiated with microwaves, and the molded product is heated and hardened by internal heat generation, and the mold itself that is in contact with the outside of the molded product is heated. Since heat is generated internally and the heat is applied to the molded product, the temperature distribution becomes uniform and uneven burning can be prevented. Further, microwave irradiation enables heat curing with a small amount of energy compared to heat curing using an autoclave.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a molded product housed in a mold, Fig. 2 is a perspective view of a part of the mold shown in Fig. 1, and Fig. 3 is a perspective view of an example of a fiber-reinforced plastic molded product. Figure 4 is a graph showing the temperature rise of the formwork due to microwaves, Figure 5 is a graph showing one mode of microwave irradiation, Figure 6 is a graph showing the temperature change of the molded product, and Figure 7 is the graph showing the molding. FIG. 8 is a diagram showing the progress of hardening of a molded product, and is a diagram showing changes in the curing rate of a molded product. 1... Molded product (panel), 3... Raised strip, 4... Internal space, 6... Formwork, 6a... Lower mold, 6b... Upper mold, 9
...Groove, 10...Radio wave transparent material.

Claims (1)

[Claims] 1. A fiber-reinforced plastic molded product is fixed in contact with a mold made of a material that generates heat using microwaves,
A method for heating and curing fiber-reinforced plastics using microwaves, in which both the molded product and the mold are irradiated with microwaves, and the molded product is heated and cured while also generating heat in the mold. 2. The method of heating and curing fiber-reinforced plastic using microwaves according to claim 1, wherein after irradiating the microwave for a predetermined time, the microwave is irradiated a plurality of times at intervals with a lower output.