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EP-4039437-B1 - METHOD FOR PRODUCING FIBER-REINFORCED PLASTIC JOINED BODY FROM PREPREG

EP4039437B1EP 4039437 B1EP4039437 B1EP 4039437B1EP-4039437-B1

Inventors

  • HIRAMATSU, MIKIO
  • JYUNISHO, TADASHI

Dates

Publication Date
20260506
Application Date
20200917

Claims (7)

  1. A method for producing a fiber-reinforced plastic combined body from a prepreg (1), comprising: heating the prepreg (1) in an atmosphere above a room temperature and lower than a curing temperature of the prepreg (1); provisionally combining pre-products (20, 30) obtained by the heating together or with another component; and retaining and curing the combined pre-products (20, 30) at the curing temperature or higher, the method characterized by comprising: before the heating, putting the prepreg (1) between porous films (3), further putting the prepreg (1) with the films (3) between gas-permeable bodies (5), and enclosing the prepreg (1) along with the gas-permeable bodies (5) and the films (3) with a gas-impermeable bag (9); depressurizing an interior of the bag (9), whereby depressurizing the atmosphere below the atmospheric pressure.
  2. The method of claim 1, wherein the prepreg (1) includes any of polyimide resins.
  3. The method of claim 1, wherein the prepreg (1) includes N-methyl-2-pyrrolidone.
  4. The method of claim 1, wherein, in the heating, the prepreg (1) is set along a mold (17, 19) for molding, whereby the prepreg is given a complementary shape to the mold (17, 19).
  5. The method of any of claims 1 through 4, wherein the heating includes executing a first heating to retain the prepreg (1) in a first atmosphere, a temperature of the first atmosphere being above a room temperature and not higher than 100 degrees C, and, after executing a second heating to retain the prepreg (1) in a second atmosphere, a temperature of the second atmosphere being not lower than 150 degrees C and lower than a curing temperature of the prepreg (1).
  6. The method of claim 5, wherein the first heating and the second heating are executed in series.
  7. The method of claim 5, wherein, in the first heating, the prepreg (1) is retained in the first atmosphere for 30 minutes or longer and 24 hours or shorter.

Description

TECHNICAL FIELD The disclosure herein relates to a method for producing a fiber-reinforced plastic combined body from a prepreg and in particular relates to a method for sufficiently removing solvents including poorly volatile solvents in particular from a prepreg to produce pre-products and then combine the pre-products together to produce a combined body. BACKGROUND ART In various technical fields, many trials have been persistently conducted to use lighter materials for the purposes of energy saving and improvement in various properties. In the aerospace field for example, aluminum alloys are being replaced by fiber reinforced plastics (FRPs) and other trials are also under way to replace nickel-based superalloys with ceramic matrix composites (CMCs). In the aerospace field, thermal resistance is of course an essential characteristic and thus materials are chosen individually on the basis of applied temperature ranges. FRPs are, as containing constitutional resins generally having glass transition temperatures lower than 300 degrees C, generally used in the low temperature range above the room temperature and not higher than 250 degrees C. In addition, as any welding technic such as welding or brazing is unavailable to FRPs unlike metals and as well bonding by adhesives is inferior in both strength and thermal resistance, FRPs are not suitable for producing a structured body such as a combined body of a disk and a blade. Specifically, because there are few options in the middle temperature range above 300 degrees C aside from few exceptions such as titanium alloys and fiber-reinforced metals (FRMs), means for weight reduction have been still limited. The patent literatures 1 - 3 disclose related arts, in which, PTL 3 relates to a method for bonding composite substrates includes coupling a first co-cure prepreg layer having a first off-set amine to epoxide molar ratio onto a surface of a first composite substrate and coupling a second co-cure prepreg layer having a second off-set amine to epoxide molar ratio onto a surface of a second composite substrate. The first and second composite substrates are cured to the first and second co-cure prepreg layers, respectively, using a first cure cycle (including B-stage and cure temperatures) to form a first and a second co-cure prepreg layer portion. The method further includes coupling the first co-cure prepreg layer portion to the second co-cure prepreg layer portion and applying a second cure cycle to cure the first co-cure prepreg layer portion of the first composite substrate to the second co-cure prepreg layer portion of the second composite substrate to form a monolithic covalently bonded composite structure. Citation List Patent Literature PTL 1: Japanese Patent Application Laid-open No. 2010-150685PTL 2: Japanese Patent Application Laid-open No. 2012-187730PTL 3: American patent Application Laid-open No. 2017-368812 A1 SUMMARY PROBLEMS TO BE SOLVED Since polyimide resins could have transition temperatures above 300 degrees C or even close to 400 degrees C, they raise expectations for application to FRPs usable in the middle temperature range above 300 degrees C. As the polyimide resins are solid even before curing (hardening by heating), generally resins are supported in solvents such as N-methyl-2-pyrrolidone (NMP) for example before forming a matrix with reinforcing fibers. But this solvent is known to be poorly volatile. According to studies by the present inventors, it is found that the glass transition temperature is measurably affected by residual NMP remaining in the preform and change of the NMP content in the order of several per mille in weight permillage to the total weight of the preform and control of the NMP content would be insufficient given that removal thereof were left solely in evaporation at the time of curing. On the other hand, as the polyimide resins without solvents do not have sufficient fluidity, any other bonding means such as adhesion are required to combine plural components. The present inventors have further conducted earnest studies in light of these problems and have found that methods described below successfully control the remaining NMP content in the order of several per mille in weight permillage and also combine plural components together without any adhesion. MEANS FOR SOLVING PROBLEMS According to an aspect, a method for producing a fiber-reinforced plastic combined body from a prepreg, includes the features of independent claim 1. ADVANTAGEOUS EFFECTS A method for producing a fiber-reinforced plastic combined body is provided, which can control the remaining NMP content in the order of several per mille in weight permillage and can also combine plural components together. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a flowchart schematically describing a method for producing a fiber-reinforced plastic combined body from a prepreg according to an embodiment.FIG. 2 is a schematic sectional elevational view of the prepre