JP2002292772A - Manufacturing method for curved-surface sandwich structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and precisely manufacture a curved-surface-shaped sandwich structure having a uniform thickness and high accuracy, a curved-surface sandwich structure having a small curvature in particular and also a sandwich structure having a complicated shape. SOLUTION: In the present manufacturing method of the curved-surface sandwich structure, one side of a block of a polyether imide resin foamed material is machined to be formed into a three-dimensional curved surface, and then a face plate made of FRP and molded in the same curved-surface shape is adhered to the above curved surface, or a face plate of an uncured fiber-reinforced resin prepreg is disposed thereat and joined thereto by heat curing molding. Next, the other side of the block is so machined along the above three-dimensional curved surface as to have a required thickness and to be formed into a three-dimensional curved surface, so that a core be formed. The face plate made of the FRP and molded in the same curved-surface shape is adhered thereafter to the three-dimensional curved surface inside the core of the polyether imide resin foamed material having the required thickness, or the face plate of the uncured fiber-reinforced resin prepreg is disposed thereat and joined thereto by heat curing molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a curved sandwich structure used for an aircraft.

[0002]

2. Description of the Related Art Conventionally, as an aircraft structural material,
Generally, as shown in FIG. 8, 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 is not pressurized except for the cell walls of the honeycomb being formed in the autoclave,
As shown in FIG. 9 which is an enlarged view of a portion A in FIG.
The strength of the air bubbles 34 remaining in 1 is low, and minute cracks 36 often occur 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, there is a serious problem that the structural strength is reduced and the flight safety is impaired. Therefore, because the composite sandwich structure is lightweight and highly rigid,
Although it has been widely used as a fuselage structural material in conventional aircraft,
At present, it is gradually being 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. 10, the polyetherimide foam material has not only a small amount of moisture absorption as compared to the polymethacrylimide foam material, but also has no characteristic deterioration due to moisture absorption. No work is required. 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. 11 of the 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. Also, using this polyetherimide foam,
For example, it has been impossible to form a bag-shaped part having a small curvature, such as a wing tip of an aircraft.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems with a conventional method for producing a sandwich structure comprising a polyetherimide foam core and an FRP face plate. It is an object of the present invention to improve a method of processing a core and to provide a method for accurately manufacturing a sandwich structure having a curved shape, which cannot be realized by a conventional manufacturing method.

[0008]

One of the methods for manufacturing a curved sandwich structure according to the present invention for solving the above-mentioned problems is to form a core by processing a polyetherimide resin foam material into a curved plate and forming the core. FR molded on the same curved surface on both sides
The method is characterized in that a P-made face plate is bonded or an uncured fiber reinforced resin prepreg face plate is arranged, heat-cured, and joined.

In the above-mentioned method for manufacturing a curved sandwich structure, one of the processes of forming the curved surface of the core is to form a flat plate of a polyetherimide resin foam material having a required thickness from 170 ° C. to 210 ° C.
It is to form a three-dimensional curved surface with the pressure of vacuum suction in a temperature range of ° C.
First, a block of a polyetherimide resin foam is machined into a three-dimensional curved plate having a required thickness.

Another method of manufacturing a curved sandwich structure according to the present invention is to machine one side of a block of a polyetherimide resin foam material to form a three-dimensional curved surface, and then apply the curved surface to the curved surface. Adhering a FRP face plate molded into the same curved shape, or disposing an uncured fiber reinforced resin prepreg face plate, heat-curing molding and joining, then the other side of the polyetherimide resin foam material block, A three-dimensional curved surface is machined to the required thickness along the three-dimensional curved surface to form a three-dimensional curved surface to form a core, and then the three-dimensional curved surface inside the polyetherimide resin foam core having the required thickness. Then, an FRP face plate formed into the same curved shape is bonded thereto, or an uncured fiber reinforced resin prepreg face plate is disposed, and then heat-cured and joined.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a curved sandwich structure according to the present invention will be described. First, one of them will be described with reference to the drawings. As shown in FIG. 1A, a polyetherimide resin foam material is processed into a curved plate to form a core 1, and then both sides of the core 1 are shown in FIG. FRP face plates 2 and 2 'molded to the same curved surface as described above, respectively, or uncured fiber reinforced resin prepreg face plates 3 and 3' as shown in FIG. Are heat-cured and joined to obtain a curved sandwich structure 4.

In the method of manufacturing the curved sandwich structure 4, there are two methods for processing the core 1 of the curved plate. One of them is molding. The molding of the core 1
This is performed by applying temperature and pressure to the polyetherimide resin foam. Therefore, although the molding can be performed by a matched die method of the upper and lower dies, since the cost of the die can be reduced, the required thickness of the polyetherimide resin foam material is formed on the mold surface 6 of the three-dimensional curved surface molding jig 5 as shown in FIG. A flat plate 7 is placed, a deformable resin film 8 is covered therefrom, and the resin film 8 is sealed with a sealing material 10 mounted on a substrate 9 of a curved surface forming jig 5. A method of applying pressure is preferred. In this method, the pressure for sucking the inside of the resin film 8 from the base 11 mounted 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 made 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.
By taking several minutes on the high temperature side and several hours on the low temperature side, permanent deformation along the mold surface 6 is given to the flat plate 7 of the polyetherimide foam material which is a thermoplastic material as shown in FIG. The core 1 can be formed into a three-dimensional curved plate core.
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 above-mentioned forming process 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.

In the above-mentioned forming process of the core 1 of the curved plate, the heat source is not only an oven but also a heat blanket, a mold jig installation 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.

Another method of processing the core 1 of the curved plate is as follows.
Machine processing. In this machining, the upper surface of the polyetherimide resin foam block 13 shown in FIG. 6A is machined to form a three-dimensional curved surface 14 as shown in FIG. The lower surface of the block 13 of the polyetherimide resin foam material is machined so as to have a required thickness along with a three-dimensional curved surface 15 as shown in FIG. The core 1 is obtained.

Next, another method for manufacturing a curved sandwich structure of the present invention will be described. The method for manufacturing a curved sandwich structure according to the present invention described above is suitable for manufacturing a curved sandwich structure having a relatively large curvature. By the way, a curved sandwich structure with a small curvature, such as an aircraft wing tip, cannot be molded at present because the core is a bag-like shape. However, it is very troublesome and expensive. In addition, the FRP
It is also very difficult to bond the face plate, which makes it difficult to produce a curved sandwich structure having a small curvature. Therefore, the present invention has focused on the excellent machinability of the polyetherimide resin foam material, and has found a method of forming a curved surface of a core by machining and bonding a face plate to the curved surface to form a curved sandwich structure. . That is, another method of manufacturing a curved sandwich structure of the present invention is to first machine one side of a block 16 of a polyetherimide resin foam material as shown in FIG.
A three-dimensional curved surface 17 having a small curvature is formed as shown in FIG.
Next, an FRP face plate 18 molded into the same curved shape as shown in FIG. 7C is adhered to the curved surface 17 or an uncured fiber reinforced resin prepreg face plate is arranged, heat-cured and joined, and then The other side of the block 16 of the polyetherimide resin foam material is machined to a required thickness along the three-dimensional curved surface 17 to form a three-dimensional curved surface 19 as shown in FIG. 7 is formed on the three-dimensional curved surface 19 inside the core 20 which has been formed into a core 20 and then has a required thickness.
As shown in (e), the FRP face plate 21 formed into the same curved shape is adhered, or an uncured fiber reinforced resin prepreg face plate is arranged, heat-cured and joined to obtain a curved sandwich structure 22. .

As described above, another method of manufacturing a curved sandwich structure according to the present invention is to form a curved surface 17 having a small curvature on one side of a block 16 of a polyetherimide resin foam material by machining. The polyetherimide resin foam is not deformed by machining, and a reference hole can be formed by opening a pilot hole in an excess portion. Also, when bonding the FRP face plate 18 molded into the same curved shape to the curved surface 17 having a small curvature, or when arranging an uncured fiber reinforced resin prepreg face plate and joining by heating and curing,
Since the curved surface 17 is a hard surface, the face plate 18 can be stably and accurately integrated with the polyetherimide resin foam material instead of a jig. Further, with the face plate 18 adhered to one curved surface 17, the other side of the block 16 of the polyetherimide resin foam is machined so as to have a required thickness along the curved surface 17 to form the curved surface 19. The core 20 having a uniform thickness and high precision can be formed without displacement or distortion. Then, an FRP face plate 21 formed into the same curved shape is bonded to the curved surface 19 on the other side of the core 20 with high accuracy,
Alternatively, since an uncured fiber reinforced resin prepreg face plate is provided, heat-cured molding and joining are performed, the face plate 21 can be integrated with the core 20 stably and accurately. Thus, not only the sandwich structure 22 having a small curvature, which cannot be realized by the conventional manufacturing method, but also the sandwich structure having a complicated shape can be easily and accurately manufactured.

[0018]

As can be seen from the above description, according to one of the methods for manufacturing a curved sandwich structure of the present invention, a core of a polyetherimide resin foam material is formed by heating or vacuum pressure forming or machining. Since it is a curved plate, it is easy to manufacture a highly accurate core, no special temperature / pressure control device is required, and no special equipment is required. Therefore, the curved sandwich structure obtained by bonding the uncured fiber reinforced resin prepreg face plate to the core of the curved plate, bonding the uncured fiber reinforced resin prepreg face plate to the core of the same curved surface, and bonding by heat-curing molding has a uniform thickness, A highly accurate curved surface shape is obtained.

According to another method of manufacturing a curved sandwich structure of the present invention, a block of a polyetherimide resin foam is machined to sequentially form curved surfaces having small curvatures on the outside and inside. Since there is no deformation due to mechanical processing, and when bonding a FRP face plate molded to the same curved surface immediately after forming a curved surface with a small curvature, or when disposing an uncured fiber reinforced resin prepreg and joining by heat curing molding Since the curved surface of the polyetherimide resin foam material serving as the core is a hard surface, the face plate can be stably and accurately integrated with the core instead of a jig. Therefore, not only a sandwich structure having a small curvature which cannot be realized by a conventional manufacturing method but also a sandwich structure having a complicated shape can be easily and accurately manufactured.

[Brief description of the drawings]

FIGS. 1a, 1b and 1c are process diagrams showing one method of manufacturing a curved sandwich structure of the present invention.

FIG. 2 is a view showing a molding method which is one of methods for processing a polyetherimide resin foam material into a core of a curved plate in the method of manufacturing the curved sandwich structure of FIG.

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.

FIGS. 6A, 6B and 6C show steps of a machining method which is another method of processing a polyetherimide resin foam material into a core of a curved plate in the method of manufacturing the curved sandwich structure of FIG. FIG.

7A to 7E are process diagrams showing another method of manufacturing a curved sandwich structure of the present invention.

FIG. 8 is a diagram showing an outline of a conventional honeycomb core sandwich structure.

FIG. 9 is an enlarged sectional view of a portion A in FIG.

FIG. 10 is a diagram showing the moisture absorption characteristics of a polyetherimide foam and a polymethacrylimide foam.

FIG. 11 is a flowchart showing a manufacturing process of a sandwich structure having a polyetherimide foam as a core.

[Explanation of symbols]

 1,20 core 2,2 ', 18,21 FRP face plate 3,3' uncured fiber reinforced resin prepreg face plate 4,22 Curved sandwich structure 5 Curved mold die 6 Mold surface 7 Polyetherimide resin foam 8 Plate of resin 8 Resin film 9 Substrate of mold jig for curved surface forming 10 Sealing material 11 Cap 12 Thermocouple 13,16 Block of polyetherimide resin foam material 14,15,17,19 Three-dimensional curved surface

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) // B29K 79:00 B29K 79:00 (72) Inventor Sayaka Shimizu 1 Kawasaki-cho, Kakamigahara-shi, Gifu Prefecture Kawasaki Heavy Industries F-term in Gifu Plant Co., Ltd. (Reference) 4F100 AK49A AK49K BA03 BA06 BA10B BA10C BA13 CB00 DH01B DH01C DH02B DH02C DJ01A EC052 EC182 EJ082 EJ281 EJ422 GB31 JL02 4F201 AA32 AA40 AD05 AD16 AD17 AD20 AMB0320 AD17 AD20 AG03 AG20 TA03 TA13 TC06 TD11 TH02 TH18 TN44 4F213 AA32 AA40 AD05 AD16 AD17 AD20 AG03 AG20 WA08 WA09 WA15 WA43 WA52 WA53 WA72 WA74 WA87 WB01

Claims (4)

[Claims] 1. A polyetherimide resin foam material is processed into a curved surface plate to form a core, and an FRP surface plate formed into the same curved surface is adhered to both surfaces of the core, or an uncured fiber reinforced resin prepreg face plate is provided. A method for producing a curved sandwich structure, comprising: heat-curing molding; and joining. 2. The method for manufacturing a curved sandwich structure according to claim 1, wherein the processing of the curved surface of the core comprises the step of forming a flat plate of a polyetherimide resin foam material having a required thickness from 170 ° C. to 2 ° C.
A method for producing a curved sandwich structure, wherein a three-dimensional curved surface is formed by a pressure of vacuum suction in a temperature range of 10 ° C. 3. The method for manufacturing a curved sandwich structure according to claim 1, wherein the curved surface of the core is formed by machining a block of a polyetherimide resin foam into a three-dimensional curved plate having a required thickness. A method for producing a curved sandwich structure. 4. One side of the block of the polyetherimide resin foam is machined to form a three-dimensional curved surface, and then an FRP face plate molded into the same curved shape is bonded to the curved surface, or Alternatively, an uncured fiber reinforced resin prepreg face plate is arranged, heat-cured and bonded, and then machined on the other side of the polyetherimide resin foam material so as to have a required thickness along the three-dimensional curved surface. A three-dimensional curved surface is formed to form a core, and an FRP face plate molded into the same curved shape is bonded to the three-dimensional curved surface inside the polyetherimide resin foam material core having a required thickness. Or a method of manufacturing a curved sandwich structure, comprising arranging an uncured fiber reinforced resin prepreg face plate, heat-curing molding, and joining.