JP3482525B2 - Method of manufacturing curved sandwich structure - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a curved sandwich structure used for an aircraft. 2. Description of the Related Art Conventionally, as an aircraft structural material,
Generally, as shown in FIG. 6 , Nomex, aluminum, GF
A sandwich structure 33 is used in which a honeycomb core 30 made of RP or the like is sandwiched between two composite material face plates 31 and bonded together with a film adhesive 32 interposed therebetween. In some cases, a sandwich structure having a polymethacrylimide foam material as a core is also used. These sandwich structures are mainly used for rotor blades (auxiliary wings, flaps, elevators, spoilers, etc.), doors, inspection door covers, radomes, etc., which require a thick wall, and occupy the weight of the body structure. Although the ratio is not large, it accounts for a large proportion of the aircraft surface area. A sandwich structure using a conventional honeycomb core has a number of problems described below.
Since the sandwich structure, the portion other than the cell walls of the honeycomb in the molding in an autoclave is not pressurized, Figure
As shown in FIG . 7 , which is an enlarged view of a portion A of FIG.
Air bubbles 34 remain inside and the strength is low, and a fine crack 36 often occurs in the resin layer 35 during repeated use of the aircraft. As the aircraft makes round trips between the ground and the stratosphere, it undergoes large atmospheric pressure and temperature fluctuations (1 atm, plus 40 ° C to 1/10 atm, minus 54 ° C), and the outside air passes through the cracks 36 formed in the composite material face plate 31 and the honeycomb It goes in and out of the core 30. Moisture contained in the atmosphere that has entered the inside of the honeycomb core 30 from outside is condensed inside the honeycomb core 30 due to changes in air pressure and temperature due to the rise of the aircraft, and remains as water droplets 37. By repeating this process, moisture is gradually accumulated inside the honeycomb core 30, and the body structure weight increases. It is said that the weight increase will reach several hundred kilograms in a large Boeing 747 class passenger aircraft. Moisture inside the honeycomb core 30 freezes in the high sky, and its volume expansion breaks the adhesive bonding between the honeycomb core 30 and the composite material face plate 31 to peel the composite material face plate 31. As a result, the structural strength decreases,
A major problem arises in that flight safety is impaired.
Therefore, composite sandwich structures have been frequently used as fuselage structural materials in conventional aircraft because of their light weight and high rigidity, but are currently being gradually replaced by metal structures. In order to solve such a problem, a sandwich structure in which the honeycomb core is replaced with a foamed plastic has been proposed. In this case, if a foamed core containing closed cells is employed, there is an advantage that it is possible to prevent moisture from entering the inside of the core which is a problem in the honeycomb core. This was an attractive proposal to improve the conventional honeycomb core sandwich structure. In this case, since the molding of the composite material face plate and the sandwiching of the core are performed in the same step, a core that can withstand the temperature and pressure is required. Therefore, a polymethacrylimide foam material was used as the core. However, this polymethacrylimide foam core also has the following problems. Strength is greatly reduced by moisture absorption. Deformation and volume shrinkage due to moisture absorption during operation occurred, and peeling from the area based on these occurred.
The bonding strength with the face plate is weak, and the face plate is peeled off by the impact due to the drop of the tool or the collision with the hail. Even when left at room temperature and in the air, it absorbs a large amount of moisture quickly, so that severe storage conditions are required and a drying treatment before use is required, so that handling is expensive and troublesome.
Deformation performance at room temperature is extremely low, so that it cannot be conformed to a mold for forming a part shape, and it is necessary to perform molding after holding the mold and the core at a high temperature. This requires special jigs / equipment and labor, and since it follows the mold at a high temperature in the equipment, it is basically impossible to check whether the mold has been accurately followed. In some cases, inconveniences occur, which is a factor that increases the molding cost of the core. Further, in order to improve the drawbacks of the sandwich structure having the polymethacrylimide foam as a core, a polyetherimide foam has been studied. As shown in FIG. 8 , the polyetherimide foam has a small amount of moisture absorption as compared with the polymethacrylimide foam,
Since there is no characteristic deterioration due to moisture absorption, strict management of storage conditions and work such as dehumidification are not required at all. In addition, the polyetherimide foam material is composed of closed cells, and has no water intrusion as the core of the sandwich structure, and the weight and strength characteristics are almost the same as those of the polymethacrylimide foam material. It is considered to be suitable as a body core. As described above, the polyetherimide foamed material having many advantages, however, has the following problems in the manufacturing process shown in FIG. 9 of a sandwich structure using this as a core. The polyetherimide resin itself is thermoplastic, and can be permanently deformed by applying a load at a temperature near 200 ° C. However, since the polyetherimide foam material to be used this time contains a large amount of voids (foaming) to reduce the density, the compression strength is originally low. In particular, at around 200 ° C. necessary for molding the core, the compressive strength is further reduced. Therefore, conventionally, it has been necessary to perform the core molding using special equipment capable of controlling the temperature and pressure in multiple stages. Further, even if this polyetherimide foam material is used, it is impossible to form a bag-like part having a small curvature such as a wing tip of an aircraft. [0007] The present invention To solve the above problems the present invention, a method for manufacturing the conventional polyetherimide foam core and an FRP faceplate and more made sandwich structure to solve the above problems, especially molding method Improved polyether
An object of the present invention is to provide a method capable of accurately manufacturing a bag-shaped sandwich structure having a small curvature, which cannot be realized by a conventional manufacturing method, using an imide foam core . [0008] A method for manufacturing a curved sandwich structure according to the present invention for solving the above-mentioned problems is required.
Thick polyetherimide resin foam flat plate at 170 ° C
Vacuum suction for several hours to several minutes in the temperature range of ~ 210 ° C
Of the core formed into a three-dimensional curved plate with the pressure of
Place an uncured fiber reinforced resin prepreg face plate on the surface and heat it
It is characterized by being cured and joined. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a curved sandwich structure according to the present invention will be described with reference to the drawings. As shown in FIG. 1A, a polyetherimide resin foam material is formed into a curved plate . on both sides of the core 1, as shown in b of FIG. 1
Disposing an uncured fiber reinforced resin prepreg faceplate 3,3 ', joined this heat curing molding to obtain a curved sandwich structure 4 shown in c of FIG. In the method of manufacturing the curved sandwich structure 4, the core 1 of the molded curved plate is formed by applying a temperature and a pressure to the polyetherimide resin foam material . That is, as shown in FIG. 2, a flat plate 7 made of a polyetherimide resin foam material having a required thickness is placed on a mold surface 6 of a mold jig 5 for forming a three-dimensional curved surface, and a deformable resin film 8 is covered thereon. , Substrate 9 of curved surface forming jig 5
Sealed and placed in a sealing material 10 attached to the above, in a method of loading the temperature and pressure in the resin film 8 the previously explained
Was. In this method, the pressure for sucking the inside of the resin film 8 from the base 11 provided on the resin film 8 by a vacuum pump or the like, which is not shown, is applied to the flat plate 7 made of polyetherimide resin foam without special control of the pressure. In a state where the flat plate 7 of the polyetherimide resin foam material is somewhat along the mold surface 6 of the mold jig 5 for curved surface molding, the temperature of 170 ° C. to 210 ° C. shown in FIG. It takes several minutes on the high side and several hours on the low side to give permanent deformation along the mold surface 6 to the flat plate 7 made of a polyetherimide foamed thermoplastic material as shown in FIG. The core 1 of the original curved plate was formed . The temperature measurement in this molding process is performed by a plurality of thermocouples 12 installed on the front and back of the flat plate 7 made of a polyetherimide resin foam material as shown in FIG. The reason why the temperature range is set to 170 ° C. to 210 ° C. in the molding of the core 1 of the curved plate is that the polyetherimide resin has a deflection temperature under load of 1 at high temperature bending.
It is 74 ° C., the glass transition temperature is 217 ° C., and it is determined from the molding temperature and the molding result in the actual curved surface molding of the core 1 from the necessity of molding in a temperature range near them. That is, at a molding temperature of less than 170 ° C. under vacuum suction, a spring bag occurred as shown in FIG. 5A, and the core 1 could not be given a predetermined curved shape. Further, at a molding temperature exceeding 210 ° C., b in FIG.
As shown in (1), the core 1 could not withstand the stress and plastic deformation occurred, and the surface became uneven, resulting in a very rough molded article. However, 170 ℃ ～ 2
At a molding temperature of 10 ° C., as shown in FIG. 5C, the core 1 could be formed into a predetermined curved surface shape and a predetermined plate thickness. In the molding of the core 1 of the curved plate, the heat source is not only an oven but also a heat blanket, a mold jig-installed heater, and a heat gun (because it is thermoplastic, it can be partially deformed and formed. ) Can be selected. Also, since pressure is given by a vacuum pump,
The molding operation of the core 1 can be performed not only in the factory but also in any place. As can be seen from the above description, according to the method for producing a curved sandwich structure of the present invention, a flat plate of a polyetherimide resin foam is formed into a three-dimensional curved plate.
On both sides of the core, distribution uncured fiber-reinforced resin prepreg faceplate
And heat-curing molding and joining, so that it has a uniform thickness, highly accurate bag-shaped
A structure can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 a, b, c is a process diagram of manufacturing how curved sandwich structure of the present invention. FIG. 2 is a cross-sectional view illustrating a method of manufacturing the curved sandwich structure shown in FIG.
It is a figure showing the method of forming . FIG. 3 is a diagram showing conditions for molding a polyetherimide resin foam material into a core of a curved plate. 4 is a view showing a state in which a core of a curved plate is formed by the forming method of FIG. 2 and the forming conditions of FIG. 3; FIG. 5 shows a temperature range of 170 ° C. to 2 in the molding conditions of FIG.
Explanatory drawing of the reason why the temperature is limited to 10 ° C., a is a molded state at less than 170 ° C., b is a molded state at a temperature exceeding 210 ° C., c
Indicates an appropriate molding state at 170 ° C to 210 ° C. FIG. 6 is an outline of a conventional honeycomb core sandwich structure.
FIG. FIG. 7 is an enlarged sectional view of a portion A in FIG . 6; FIG. 8: Polyetherimide foam and polymethacrylic
It is a figure which shows the moisture absorption characteristic of a mid foam. FIG. 9: Sand with polyetherimide foam as core
It is a flowchart which shows the manufacturing process of a switch structure. [Description of Signs] 1 core 3, 3 ′ uncured fiber reinforced resin prepreg face plate 4 curved surface sandwich structure 5 curved surface forming mold jig 6 mold surface 7 flat plate of polyetherimide resin foam material 8 resin film 9 curved surface molding die Jig substrate 10 sealing material 11 base 12 thermocouple

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-229046 (JP, A) JP-A-62-50128 (JP, A) JP-A-55-11847 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (1)

(57) [Claims] [Claim 1] Polyetherimide resin foam of required thickness
A plate for several hours at a temperature range of 170 ° C. to 210 ° C.
It takes several minutes to form a three-dimensional curved plate with the pressure of vacuum suction.
An uncured fiber reinforced resin pre-press is applied to both sides of the shaped core.
A method for producing a curved sandwich structure , comprising arranging heat-cured face plates and joining them by heat-curing molding.