Method and mold for manufacturing fiber-reinforced plastic structure

In the manufacturing method of the present invention, as preparation for providing a mold 30 with protrusions 31 and 32 to be printed on an FRP material of a skin 1 in co-bold molding, which requires resetting of the skin 1 to the mold 30, a long protrusion 32A and a short protrusion 32B are interchangeable as one protrusion 32. The long protrusion 32A is printed to form a second recessed part 12 in the skin 1, and before the skin 1 is reset, the long protrusion 32A is replaced with the short protrusion 32B. In this way, as the short protrusion 32B is housed in the second recessed part 12 formed during elongation of the mold 30, the skin 1 can be reset in the state of being positioned relative to the mold 30 by the first protrusion 31 and the short protrusion 32B.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a method for manufacturing a fiber-reinforced plastic structure and a mold used for manufacturing a fiber-reinforced plastic structure.

Description of the Related Art

Being lightweight and excellent in mechanical strength, fiber-reinforced plastics (FRPs) are used for structural members of an aircraft and the like.

For example, a skin of an aircraft and a stringer reinforcing the skin are also formed of FRPs.

Here, as shown in Mitsubishi Heavy Industries Technical Review, Vol. 42, No. 5 (December 2005), “Research in the Application of the VaRTM Technique to the Fabrication of Primary Aircraft Composite Structures,” co-bond molding is performed in which a fiber base material as the FRP material of the stringer is disposed in a pre-molded skin, and a resin which is impregnated in the fiber base material is heated and cured. When the resin has cured to a predetermined hardness, the stringer is molded, and at the same time, the stringer is integrally bonded to the skin through an adhesive. Thus, a fiber-reinforced plastic structure is manufactured.

In the co-bond molding of the skin and the stringer, first, the skin is molded by using a mold. The molded skin is then removed from the mold and inspected with ultrasound. Thereafter, the skin is returned (reset) to the mold before the stringer is molded. Then, the stringer is molded while the FRP material of the stringer disposed on the skin is being pressed by a mandrel which is positioned relative to the mold.

In the above-described co-bond molding of the skin and the stringer, unless the skin is returned to the mold at the same position as where the skin was molded, the stringer ends up being molded at a position off a defined position. This makes it difficult to fit the stringer to its mating part.

In order that the skin can be reliably disposed at its original position in the mold, protrusions are formed at positions in the mold corresponding to two points in the skin which are apart from each other, and recessed parts are formed in the skin by printing the protrusions of the mold on the skin during molding of the skin. When returning the skin to the mold, fitting the protrusions of the mold respectively into the recessed parts of the skin allows the skin to be positioned relative to the mold.

However, accurate positioning by the printing approach as described above requires the mold to be made of Invar with a low thermal expansion coefficient, which drives up the material cost of the mold.

If the mold is made of a material with a high thermal expansion coefficient, the protrusions of the mold are printed on the skin while the mold is elongated due to the heat applied during molding, so that, once a normal temperature is reached, the pitch of the protrusions of the mold has become smaller than the pitch of the recessed parts of the skin. As a result, the skin cannot be reset in the state of being positioned relative to the mold.

The object of the present invention based on the above problem is to provide a method and mold for manufacturing a fiber-reinforced plastic structure which allow a demolded fiber-reinforced plastic member to be reset in the state of being positioned relative to the mold, while keeping the material cost of the mold low.

SUMMARY OF THE INVENTION

A method for manufacturing a fiber-reinforced plastic structure of the present invention is a method, including: as preparation for positioning a first fiber-reinforced plastic member relative to a mold at places apart from each other in a predetermined direction, providing the mold with a first printing part at a reference one of the places, and detachably providing the mold with a second printing part, for which a near printing part and a far printing part at different distances from the first printing part in the predetermined direction are interchangeably arranged; a molding step of molding the first fiber-reinforced plastic member by using the mold; a resetting step of returning the first fiber-reinforced plastic member, which has been removed from the mold, to the mold; and an integrating step of integrating a second fiber-reinforced plastic member into the first fiber-reinforced plastic member.

The molding step includes: a near printing part installing step of providing the mold with the near printing part; and a heating and printing step of heating the material of the first fiber-reinforced plastic member, and printing the first printing part on the material to form a first printed part while printing the near printing part on the material to form a second printed part.

The resetting step includes: a far printing part installing step of providing the mold with the far printing part; and a positioning and resetting step of setting the fiber-reinforced plastic member in a state of being positioned relative to the mold, by using the first printing part, which is housed in the first printed part, and the far printing part, which is located in a region of the near printing part after its elongation during the heating and printing step with reference to the first printing part and housed in the second printed part.

Then, a fiber-reinforced plastic structure integrated with the first fiber-reinforced plastic member and the second fiber-reinforced plastic member is obtained by the integrating step.

Here, a protrusion, a recessed part, a step, or the like can be adopted as the form of the first printing part and the second printing part. The first printing part and the second printing part may have the same form or different forms. The forms of the first printed part and the second printed part are determined according to the forms of the first printing part and the second printing part. For example, if the first printing part and the second printing part are protrusions, then the first printed part and the second printed part are recessed parts. Or, if the first printing part and the second printing part are recessed parts, then the first printed part and the second printed part are protrusions.

According to the present invention, in the molding of the fiber-reinforced plastic structure which requires resetting of the first fiber-reinforced plastic member to the mold, as preparation for providing the mold with the positioning protrusions to be printed on the FRP material of the first fiber-reinforced plastic member, the near printing part and the far printing part at different distances from the first printing part are interchangeable as the second printing part, which is apart from the first printing part disposed at a reference place.

Then, the first printing part and the near printing part are printed on the first fiber-reinforced plastic member to form the first printed part and the second printed part in the first fiber-reinforced plastic member, and before the first fiber-reinforced plastic member is reset, the near printing part is replaced with the far printing part.

At this time, as the mold is in a normal temperature range, the pitch between the place where the first printing part is provided and the place where the second printing part is provided has decreased from the pitch at the time of molding of the first fiber-reinforced plastic member. Accordingly, the pitch between the place where the first printing part is provided and the place where the second printing part is provided is narrow compared to the pitch between the first printed part and the second printed part which is equal to the pitch between the first printing part and the second printing part (near printing part) during molding of the first fiber-reinforced plastic member.

Nevertheless, the far printing part is housed in the second printed part which is printed by the near printing part when the mold is elongated, since the far printing part is located in a region of the near printing part after its elongation during molding of the first fiber-reinforced plastic member with reference to the first printing part.

Thus, the first fiber-reinforced plastic member can be reset in the state of being positioned relative to the mold by the far printing part to be housed in the second printed part and the first printing part to be housed in the first printed part.

According to the present invention, a positional shift occurring between the recessed parts printed on the FRP material and the protrusions of the mold at a normal temperature, which is attributable to elongation of the mold due to thermal expansion, can be dealt with by the alternate use of the near printing part and the far printing part. Therefore, an inexpensive material even with a higher thermal expansion coefficient than that of the FRP can be used for the mold, so that the molding cost can be reduced.

According to the present invention, a high positioning accuracy required for resetting the fiber-reinforced plastic member can be achieved by simply providing the mold with the printing parts such as protrusions and recessed parts. Thus, the present invention provides wide-ranging options for the mold material, and materials with a low heat capacity and high thermal conductivity become available regardless of the linear expansion coefficient. This makes it possible to reduce the cycle time for curing the fiber-reinforced plastic member by heating and to save energy.

In the integrating step, which is performed after the first fiber-reinforced plastic member is reset, a second fiber-reinforced plastic member can be molded from the material of the second fiber-reinforced plastic member by an arbitrary method.

In the method for manufacturing a fiber-reinforced plastic structure of the present invention, it is preferable that a long protrusion and a short protrusion with different lengths in the predetermined direction are interchangeably arranged as the second printing part, the long protrusion serving as the near printing part and the short protrusion serving as the far printing part, and that, in the positioning and resetting step, the short protrusion is located within a range of overlap between regions of the long protrusion before and after its elongation during the heating and printing step with reference to the first printing part.

This configuration is effective when the second fiber-reinforced plastic member is molded after the material of the second fiber-reinforced plastic member is heated. In this case, the mold undergoes thermal expansion as the material of the second fiber-reinforced plastic member is heated.

Here, the short protrusion is located not only in the region of the long protrusion after its elongation but also in the region of the long protrusion before its elongation. As the mold is elongated due to thermal expansion, the short protrusion inside the second printed part shifts relative to the first fiber-reinforced plastic member. At this time, since the short protrusion is located in the region of the long protrusion before its elongation, even if the mold is elongated to a dimension equal to its dimension during the molding step, the short protrusion moves only to the end of the second printed part with elongation of the mold, and does not come over the second printed part.

Thus, the short protrusion remains inside the second printed part, and thereby the first fiber-reinforced plastic member is maintained in the state of being positioned relative to the mold, so that the second fiber-reinforced plastic member can be molded at a predetermined position in the first fiber-reinforced plastic member.

In the method for manufacturing a fiber-reinforced plastic structure of the present invention, it is preferable that the near printing part and the far printing part are formed in equal widths and maintained in a direction along the predetermined direction, and the length of the far printing part is longer than its width.

In this way, the far printing part is prevented from rotating relative to the second printed part which is formed in a width corresponding to the width of the near printing part. Thus, the first fiber-reinforced plastic member is positioned along the far printing part in a direction along the predetermined direction, without rotating relative to the mold in the in-plane direction.

Accordingly, even a slight positional shift caused by rotation of the first fiber-reinforced plastic member at the position of the far printing part can be prevented, so that the first fiber-reinforced plastic member can be more accurately positioned relative to the mold.

The method for manufacturing a fiber-reinforced plastic structure of the present invention can be used for molding a fiber-reinforced plastic structure which integrates multiple members used for an aircraft.

In particular, the present invention can be suitably used for the co-bond molding of a skin which is the first fiber-reinforced plastic member and a stringer which is a second fiber-reinforced plastic member.

The present invention can also be developed into a mold which is used for molding a fiber-reinforced plastic structure.

A mold used for molding a fiber-reinforced plastic structure of the present invention is a mold, which allows a first fiber-reinforced plastic member to be positioned at places apart from one another in a predetermined direction, wherein a first printing part is provided at a reference one of the places, and a second printing part, for which a near printing part and a far printing part at different distances from the first printing part in the predetermined direction are interchangeably arranged, is detachably provided.

When the material of the first fiber-reinforced plastic member is heated to mold the first fiber-reinforced plastic member, the first printing part is printed on the material to form a first printed part in the first fiber-reinforced plastic member, while the near printing part is printed on the material to form a second printed part in the first fiber-reinforced plastic member.

After the first fiber-reinforced plastic member is demolded, the far printing part is provided in the mold in place of the near printing part.

When the first fiber-reinforced plastic member is returned to the mold, the first fiber-reinforced plastic member is positioned by the first printing part, which is housed in the first printed part, and the far printing part, which is housed in the second printed part.

Then, a fiber-reinforced plastic structure is obtained by integrating a second fiber-reinforced plastic member into the first fiber-reinforced plastic member.

A method for positioning a fiber-reinforced plastic member of the present invention is a method including: as preparation for positioning a fiber-reinforced plastic member relative to a mold at places apart from one another in a predetermined direction, providing the mold with a first printing part at a reference one of the places, and detachably providing the mold with a second printing part, for which a near printing part and a far printing part at different distances from the first printing part in the predetermined direction are interchangeably arranged; a molding step of molding the fiber-reinforced plastic member by using the mold; and a resetting step of returning the fiber-reinforced plastic member, which has been removed from the mold, to the mold.

In the present invention, the molding step includes: a step of providing the mold with the near printing part, which is closer to the first printing part, as the second printing part; and a heating and printing step of heating the material of the fiber-reinforced plastic member, and printing the first printing part on the material to form a first printed part while printing the near printing part on the material to form a second printed part, and the resetting step includes: a far printing part installing step of providing the mold with the far printing part; and a positioning step of positioning the fiber-reinforced plastic member relative to the mold, by using the first printing part, which is housed in the first printed part, and the far printing part, which is located in a region of the near printing part after its elongation during the heating and printing step with reference to the first printing part and which is housed in the second printed part.

In the method for manufacturing a fiber-reinforced plastic structure and the method for positioning a fiber-reinforced plastic member described above, it is preferable that a protrusion projecting from the mold is used as the second printing part, and that, as preparation for heating the material of the first fiber-reinforced plastic member and printing the first printing part and the second printing part on the material in the molding step, an end portion of a fiber base material, which constitutes the material and is disposed on the near printing part, on a side away from the first printing part is cut off to expose the near printing part from the fiber base material.

In this way, when the mold is elongated during the heating and printing step, the protrusion (near printing part) disposed in the mold comes out of the fiber base material, so that the fiber base material is not pulled by the protrusion. Thus, wrinkling of the fiber base material can be avoided and the molding quality of the first fiber-reinforced plastic member can be improved.

According to the present invention, the demolded fiber-reinforced plastic member can be reset in the state of being positioned relative to the mold even when the mold has a high thermal expansion coefficient, which makes it possible to reduce the molding cost by using an inexpensive material for the mold.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The fiber-reinforced plastic structure10includes a skin1and a stringer2provided on the back surface of the skin1.

The skin1which forms a surface skin of an aircraft wing is assembled with a spar (not shown) into a box shape. The skin1is formed in a curved surface shape. The width of the skin1gradually narrows from a root side to a tip side of the wing.

The skin1is formed with an extra portion101which is eventually cut off.

The multiple stringers2reinforce the skin1by being provided parallel to one another on the back surface of the skin1. The stringer2is integrally bonded to the back surface of the skin1. While the stringer2has a T-shaped cross-section, the stringer may be formed in another shape.

The fiber-reinforced plastic (FRP) which forms the skin1and the stringer2is constituted of a fiber base material and a resin.

The fiber base material is formed in a sheet shape, and a required number of the sheets are stacked according to the thickness of the skin1or the stringer2. Any fiber such as carbon fiber or glass fiber can be used as the fiber base material.

A thermosetting resin which cures by being heated, for example, epoxy, vinyl ester, unsaturated polyester, phenol, and bismaleimide, etc, can be used as the resin impregnating the fiber base material. A thermoplastic resin which is solidified by being heated, for example, nylon, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), and polycarbonate can also be used.

In this embodiment, the vacuum assisted resin transfer molding (VaRTM) is performed to mold the fiber-reinforced plastic. That is, an enclosed space is depressurized to a predetermined degree of vacuum by evacuating the air to thereby assist the resin injection, and the fiber base material and the resin are compressed by the differential pressure between the pressure inside the depressurized space and the atmospheric pressure.

Next, the configurations of a mold30, a mandrel20, and an alignment jig40used for molding the skin1and the stringer2will be described with reference also toFIG. 2.

The mold30molds the skin1together with a plate-like molding jig (not shown) which presses the FRP material of the skin1against the mold30.

The mold30includes a molding part301for molding a surface of the skin1, and a peripheral part302which is a portion surrounding the molding part301.

The mold30of this embodiment is formed of steel. The mold30can also be formed of any other metal material such as aluminum, nickel, or titanium.

The mandrel20is a mold for molding the stringer2by pressing the FRP material against the back surface of the skin1. The mandrel20can be formed of Invar or an FRP. The mandrels20with length and shape corresponding to the respective stringers2are separately prepared.

The material of the fiber-reinforced plastic is disposed inside the mandrel20. An injection passage for injecting a liquid resin to the inside is formed in the mandrel20.

The alignment jig40presses the multiple mandrels20, which are aligned on the back surface of the skin1, so as not to shift from the predetermined positions. It is preferable that the alignment jig40is formed of Invar. The alignment jig40spans the mold30in the width direction and engages with each mandrel20.

The multiple alignment jigs40are provided at intervals in the length direction of the skin1.

In this embodiment, the fiber-reinforced plastic structure10is manufactured by the co-bond molding of the skin1and the stringer2.

In the co-bond molding, the skin1is pre-molded by using the mold30. The skin1is temporarily removed from the mold30for inspection, and then is returned (reset) to the mold30when the stringer2is molded. At this time, a first protrusion31and a second protrusion32provided in the mold30are printed on the skin1during molding of the skin1so that the skin1can be reliably disposed at its original position in the mold30. Then, the skin1is positioned relative to the mold30at two places by the recessed parts printed on the skin1and the protrusions31and32of the mold30.

In the following, the configuration of the first protrusion31and the second protrusion32provided in the mold30will be described.

The first protrusion31and the second protrusion32are apart from each other in a wing length direction D (predetermined direction). The first protrusion31is located on the wing root side. The second protrusion32is located on the wing tip side.

The wing root side requires a higher positional accuracy than the wing tip side, for fitting the stringer2, which is integrated into the skin1, to its mating part (e.g., auxiliary spar). For this reason, the first protrusion31is provided as a positioning reference on the wing root side, while the second protrusion32is provided on the wing tip side.

Whether the first protrusion31or the second protrusion32is provided on the wing root side or the tip side is determined on the basis of factors such as presence of a mating part, a degree of impact of a positional error of the stringer2on the strength of the wing.

The first protrusion31and the second protrusion32are both provided at a position in the molding part301corresponding to the extra portion101of the skin1so as to project from the surface of the mold30.

The first protrusion31is integrally formed in the mold30. A first recessed part11is formed in the extra portion101of the skin1by the first protrusion31being printed on the skin1.

As shown inFIG. 3Ain cross-section, the first protrusion31is formed in a semispherical shape.

This embodiment features the configuration of the second protrusion32in the mold30.

The second protrusion32is detachably provided in the mold30.

Two types of protrusions, a long protrusion32A (FIG. 3B) and a short protrusion32B (FIG. 3C), are interchangeably arranged as the second protrusion32.

A length L1of the long protrusion32A in the wing length direction D is longer than a length L2of the short protrusion32B.

The long protrusion32A is provided in the mold30during molding of the skin1and used for printing on the skin1. A second recessed part12having a long hole shape is formed in the extra portion101of the skin1by the long protrusion32A being printed on the skin1. Thereafter, the short protrusion32B is provided in the mold30in place of the long protrusion32A.

The long protrusion32A and the short protrusion32B are formed in an equal width W (FIGS. 4A and 4D), and have an elongated circular shape in planar view with the lengths L1and L2longer than the width W.

A spherical head pin35with the tip of its head portion351formed in a semispherical shape is used as the first protrusion31.

The long protrusion32A has a structure such that a block36can be put over the head portions351and351of the two spherical head pins35and35mounted on the mold30.

The short protrusion32B likewise has a structure such that a block37can be put over the head portions351and351of the two spherical head pins35and35mounted on the mold30.

The spherical head pin35includes the head portion351and a shaft portion352which is formed integrally with the head portion351. The spherical head pin35is fixed to the mold30by its shaft portion352being fitted with clearance into a hole320which is formed in the mold30. The head portion351has a semispherical tip351A, and the tip351A projects from the surface of the mold30.

In this embodiment, since the spherical head pin35is provided in the hole320of the mold30, the resin used for molding the skin1is prevented from flowing into the hole320. Thus, the resin is easily wiped off the mold30.

The blocks36and37are both disposed on the surface of the mold30and include housing portions360, which have a semispherical shape conforming to the shape of the tip351A of the head portion351, at positions corresponding to the two spherical head pins35and35. The blocks36and37are fixed to the mold30by being put over the spherical head pins35so that the tip351A is inserted into the housing portion360. The clearance between the housing portion360and the tip351A is set to a narrow dimension to prevent inflow of the resin.

The length L1of the block36of the long protrusion32A is longer than the length L2of the block37of the short protrusion32B.

The blocks36and37have a semicircular transverse cross-section perpendicular to the direction of the lengths L1and L2. In addition, the blocks36and37have a chamfered curved surface at both ends in the length direction.

Thus, the tip351A of the head portion351of the first protrusion31, the block36of the long protrusion32A, and the block37of the short protrusion32B are all rounded in every direction on their outer periphery. For this reason, as will be described later, when the first protrusion31is housed in the first recessed part11and the short protrusion32B is housed in the second recessed part12printed by the long protrusion32A, these protrusions are smoothly housed in the recessed parts without catching on the mold30.

Also in the relation between the blocks36and37and the spherical head pin35, the semispherical shapes of the housing portions360of the blocks36and37and the tip351A of the spherical head pin35allow the long protrusion32A and the short protrusion32B to be smoothly put over the spherical head pin35without catching on the spherical head pin35.

The two spherical head pins35supporting the blocks36and37are held inside the holes320and320which are formed in the mold30at a predetermined interval in the wing length direction D.

The holes320and320are located nearly at the center in the length direction of the second recessed part12formed by the long protrusion32A. However, it is not necessary that the holes320and320are located at the center, and the holes may be located closer to the wing tip than at the center.

The long protrusion32A and the short protrusion32B are both held on the mold30at two points by the two spherical head pins35. Thus, the long protrusion32A and the short protrusion32B are both held in the direction along the wing length direction D while their rotation around the axis of the spherical head pin35is restricted.

As will be described later, at a normal temperature, the short protrusion32B is located within a range of overlap between regions of the long protrusion32A before and after its elongation during molding of the skin1with reference to the first protrusion31.

The respective lengths L1and L2and the relative positions in the wing length direction D of the long protrusion32A and the short protrusion32B are set on the basis of calculations and tests according to the thermal expansion coefficient of the mold30and the heating temperature of the resin.

Next, a method for manufacturing the fiber-reinforced plastic structure10will be described with reference toFIGS. 4A to 4DandFIG. 5.

First, the skin1is molded (skin molding step S1). At this time, as shown inFIG. 4A, the long protrusion32A is provided in the mold30as the second protrusion (long protrusion installing step S1).

Then, a fiber base material which is the FRP material used for the skin1is disposed on the mold30and pressed by a plate-like molding jig (not shown).

Here, as shown inFIG. 3B, it is preferable that an end portion on the wing tip side of the fiber base material, which is disposed on the long protrusion32A, is cut off in advance along a line CL indicated by the two-dot chain line. It is only necessary to dispose a fiber base material main body F1, which has been separated from a fiber base material wing end portion F2, on the mold30. As will be described later, the long protrusion32A is exposed from the fiber base material by cutting off the end portion of the fiber base material along the line CL on the side away from the first protrusion31so that the fiber base material main body F1is not pulled by the long protrusion32A when the mold30is elongated. The line CL is set closer to the wing root side than an end portion361on the wing end side of the block36of the long protrusion32A.

Next, a bag film is put over the molding jig, and the fiber base material and the molding jig are sealed between the bag film and the mold30. Then, the enclosed space created between the bag film and the mold30is depressurized by evacuation of the air. Thus, the resin injection is assisted and the fiber base material and the resin are compressed (evacuating step S12).

Concurrently with evacuation of the air, the resin is heated by using a given heat source. The mold30is also heated by the heat produced from the heat source. An oven, a heater mat, a heat gun, etc. can be used as the heat source.

When heated, the mold30is elongated due to thermal expansion. InFIG. 4A, the outlined arrow indicates the elongation of the mold30in the wing length direction D. InFIGS. 4A to 4D, the molds30are aligned with reference to the position of the first protrusion31. This is the same inFIGS. 6A to 6Das well as inFIGS. 9A to 9D.

When the mold30shown inFIG. 4Ais elongated, a pitch P1between the first protrusion31and the long protrusion32A of the mold30is widened to a pitch P2as shown inFIG. 4B.

Here, as the FRP material of the skin1is pressed against the surface of the mold30by the molding jig and the differential pressure between the pressure inside the enclosed space and the atmospheric pressure, the first protrusion31and the long protrusion32A are printed on the FRP material (heating and long protrusion printing step S13).

When the resin has cured to a predetermined hardness and the fiber base material and the resin are integrated, the skin1is molded. Since the printed shapes are remaining on the skin1, the first recessed part11conforming to the first protrusion31and the second recessed part12conforming to the long protrusion32A are formed.

The molded skin1is demolded for inspection with ultrasound, for example (skin demolding step S14).

When the mold30is elongated during the above-described heating and long protrusion printing step S13, the wing end side of the long protrusion32A provided in the mold30comes out of the fiber base material main body F1. That is, the fiber base material main body F1is not pulled by the long protrusion32A while the long protrusion32A is moving to the right which is the wing end side inFIG. 3B. Thus, wrinkling of the fiber base material can be avoided and the molding quality of the skin1can be improved.

Thereafter, the skin1is reset on the mold30(resetting step S2) before the stringer2is molded on the skin1which is determined as a non-defective product by the inspection.

Since the mold30at this time is in a normal temperature range, it has returned to a dimension equal to its dimension before molding of the skin1(FIG. 4A). At this time, the pitch P1between the first protrusion31and the long protrusion32A is narrower than the pitch between the first recessed part11and the second recessed part12on the skin1which is equal to the pitch P2after elongation of the mold30. As such, the skin1cannot be reset in the state of being positioned relative to the mold30.

Therefore, as shown inFIG. 4C, in the resetting step S2, the short protrusion32B is provided in the mold30in place of the long protrusion32A (short protrusion installing step S21).

At this time, the short protrusion32B is located within a range Lp of overlap between a region R1of the long protrusion32A before its elongation during molding of the skin1and a region R2of the long protrusion32A after its elongation with reference to the first protrusion31.

Therefore, the short protrusion32B is located in the region R2of the long protrusion32A after its elongation as well as in the region R1of the long protrusion32A before its elongation with reference to the first protrusion31. Resetting the skin1requires the short protrusion32B to be located in the region R2of the long protrusion32A after its elongation. It is effective in a co-bond molding step S3, in which the material of the stringer2is heated and cured, that the short protrusion32B is located in the region R1of the long protrusion32A before its elongation.

As shown inFIG. 4D, when the skin1is set on the mold30, the first protrusion31is housed in the first recessed part11, while the short protrusion32B is housed in the second recessed part12which reflects the position of the long protrusion32A during elongation of the mold30since the short protrusion32B is located in the region R2of the long protrusion32A after its elongation.

Thus, the skin1is held on the mold30at the two places of the first protrusion31and the short protrusion32B, and thereby the skin1is reset on the mold30in the state of being positioned relative to the mold30in the planar direction (positioning and resetting step S22).

Here, the second recessed part12is formed along the wing length direction D by the long protrusion32A. The short protrusion32B housed in this second recessed part12is also along the wing length direction D, and the length L2of the short protrusion32B is longer than its width W. Therefore, rotation of the short protrusion32B relative to the second recessed part12, which is formed in a width corresponding to the width W of the long protrusion32A, is restricted. This allows the skin1to be positioned along the short protrusion32B in the direction along the wing length direction D, without the skin1rotating relative to the mold30in the in-plane direction.

Thus, even a slight positional shift due to rotation of the skin1at the position of the short protrusion32B can be prevented, so that the skin1can be more accurately positioned relative to the mold30.

Thereafter, the stringer2is molded on the skin1by the co-bond molding (co-bond molding step S3). For this purpose, the fiber base material as the FRP material is disposed on the back surface of the skin1, and the FRP material is pressed by the mandrel20. A thermosetting adhesive formed in a film shape is interposed between the fiber base material and the skin1.

Then, the mandrel20is sealed between the bag film and the mold30, before the mandrel20is pressed by the alignment jig40fixed to the mold30.

Subsequently, the resin is injected and the fiber base material and the resin are pressurized by the VaRTM method in the same manner as molding of the skin1. Concurrently, the resin is heated by a given heat source.

The mold30undergoes thermal expansion by the heat produced from the heat source during this process. The short protrusion32B, which is located near an end E1on the wing root side of the second recessed part12at a normal temperature, shifts toward an end E2on the wing tip side of the second recessed part12when the mold30is elongated as indicated by the arrow inFIG. 4D.

At this time, as described above, since the short protrusion32B is also located in the region R1of the long protrusion32A before its elongation, even when the mold30is elongated to a dimension equal to its dimension during the skin molding step S1, the short protrusion32B moves only to the end E2of the second recessed part12with elongation of the mold30. The dimension to which the mold30is elongated by the heat applied during molding of the stringer2is equal to or less than the dimension to which the mold30is elongated due to the heat applied during molding of the skin1. Therefore, the short protrusion32B does not come over the end E1of the second recessed part12and remains inside the second recessed part12. Thus, the skin1is maintained in the state of being positioned relative to the mold30.

Accordingly, when the resin has cured to a predetermined hardness, the stringer2is bonded at a predetermined position on the skin1.

Thereafter, secondary curing treatment and finishing treatment are performed as necessary to complete the manufacture of the fiber-reinforced plastic structure10integrated with the skin1and the stringer2.

As has been described above, in this embodiment, as preparation for providing the mold30with the positioning protrusions31and32to be printed on the FRP material of the skin1in the co-bond molding which requires resetting of the skin1to the mold30, the long protrusion32A and the short protrusion32B are interchangeable as the one protrusion32.

Then, the long protrusion32A is printed to form the second recessed part12in the skin1, and before the skin1is reset, the long protrusion32A is replaced with the short protrusion32B. In this way, even when the pitch (P2) between the first recessed part11and the second recessed part12is different from the pitch (P1) between the first protrusion31and the second protrusion32, the skin1can be reset in the state of being positioned relative to the mold30by the first protrusion31and the short protrusion32B.

According to this embodiment, a positional shift occurring between the recessed parts11and12printed on the FRP material and the protrusions31and32of the mold30at a normal temperature, which is attributable to elongation of the mold30due to thermal expansion, can be dealt with by the alternate use of the long protrusion32A and the short protrusion32B. Thus, an inexpensive material even with a higher thermal expansion coefficient than the FRP can be used for the mold30. Since the mold30requires a larger amount of material than the mandrel20or the alignment jig40, using an inexpensive material for the mold30allows a significant reduction in the molding cost.

In the above embodiment, the stringer2is molded on the skin1which has been reset on the mold30, and at the same time, the stringer2is bonded to the skin1; however, the pre-molded stringer2may be bonded to the skin1which has been reset on the mold30.

In the above embodiment, the skin is positioned at two places of the one reference place where the first protrusion31is provided and the other place where the second protrusion32is provided apart from the reference place. However, if the skin1is longer, three or more places are sometimes used for positioning the skin. When positioning the skin at three places, the second protrusion32is provided at each of the two places other than the reference place. The long protrusion32A and the short protrusion32B are interchangeably arranged for one of the second protrusions32at the two places, and the long protrusion32A and the short protrusion32B are also interchangeably arranged for the other second protrusion32. Each of the long protrusions32A and the short protrusions32B at the two places are set to a length corresponding to the distance from the first protrusion31.

In view of resetting the skin1on the mold30, it is only necessary that the short protrusion32B is located in the region R2of the long protrusion32A after its elongation with reference to the first protrusion31. That is, even when the short protrusion32B is located in the region R2of the long protrusion32A after its elongation, closer to the wing tip side than the range Lp of overlap with the region R1, the skin1can be set in the state of being positioned relative to the mold30as the short protrusion32B is housed in the second recessed part12.

Also in view of resetting the skin1on the mold30, as shown inFIGS. 6A to 6D, a near protrusion33A and a far protrusion33B of the same length may be arranged as the second protrusion32.

A distance D1from the first protrusion31to the near protrusion33A in the wing length direction D is smaller than a distance D2from the first protrusion31to the far protrusion33B. The distance between the near protrusion33A and the far protrusion33B is set so that the far protrusion33B is located in the region of the near protrusion33A after its elongation during molding of the skin1. The distances D1and D2correspond to the pitches P1and P2described above.

In the configuration shown inFIGS. 6A to 6D, the near protrusion33A is used for printing on the skin1, and before resetting the skin1, the near protrusion33A is replaced with the far protrusion33B. Then, due to the positional relation between the near protrusion33A and the far protrusion33B, the far protrusion33B is housed in the second recessed part12which is printed by the near protrusion33A.

Thus, the skin1can be reset on the mold30in the positioned state by the first protrusion31and the far protrusion33B.

The long protrusion32A in the above embodiment is equivalent to the near protrusion33A in that it is closer to the first protrusion31. The short protrusion32B is equivalent to the far protrusion33B in that it is farther from the first protrusion31.

FIGS. 7A to 7Cshows forms of the first protrusion31and the second protrusion32which are different from the above embodiment.

The first protrusion31is formed in a semispherical shape integrally with the mold30.

The second protrusion32is detachably provided in the mold30.

Two types of protrusions, a long protrusion42A (FIG. 7B) and a short protrusion42B (FIG. 7C), are interchangeably arranged as the second protrusion32.

Each of the long protrusion42A and the short protrusion42B includes a protrusion body421which projects from the surface of the mold30and a holding portion422which is held on the mold30.

The long protrusion42A includes two holding portions422, while the short protrusion42B includes one holding portion422. Each holding portion422is formed in a columnar shape with its axis along the direction of projection of the protrusion body421.

Holes420and420, into which the two holding portions422of the long protrusion42A are inserted, are formed in the mold30at positions apart from each other in the wing length direction D. Of the holes420and420, the holding portion422of the short protrusion42B is inserted into the hole420on the wing root side.

The long protrusion42A is held on the mold30located at two points by the two holding portions422. The short protrusion42B is engaged with a key groove (not shown) on the inner wall of the hole420by a key422A which is formed on the outer periphery of the holding portion422. Thus, the long protrusion42A and the short protrusion42B are both maintained in the direction along the wing length direction D while their rotation around the axis of the holding portion422is restricted.

Instead of forming the key422A and the key groove, the holding portion422may be formed in a rectangular columnar shape or an elliptical shape and the hole420may be formed in a corresponding shape.

Any number of the holding portions422may be provided at any position. The holding portion422of the short protrusion42B may be inserted into a hole which is separately formed from the hole420into which the holding portion422of the long protrusion42A is inserted.

Or, the long protrusion42A may be held on the mold30by only one holding portion422. In this case, rotation around the axis can be restricted, for example, by forming the key422A in the holding portion422.

The structure for holding the long protrusion42A and the short protrusion42B on the mold30is not limited to the above-described holding portion422, and may be arbitrarily configured.

The first protrusion31may also be formed separately from the mold30and held on the mold30, as with the long protrusion42A and the short protrusion42B.

The first protrusion31, the long protrusion42A, and the short protrusion42B can be formed in any shape as long as they serve the purpose of positioning.

For example, the protrusion body421of the short protrusion42B may be formed in a semispherical shape as with the first protrusion31. Also in this case, the skin1can be positioned as well in the two-dimensional direction at the two positions of the first protrusion31and the short protrusion42B, so that the skin can be reset as with the above-described embodiment.

It is also possible to form the first protrusion31as well as the protrusion body421of the short protrusion42B in a columnar shape.

The long protrusions32A and42A and the short protrusions32B and42B can be formed of any material such as metal, resin, or ceramics. The long protrusion32A which is held on the mold30by the two spherical head pins35and35is preferably formed of the same material as the mold30or a material with a thermal expansion coefficient near the thermal expansion coefficient of the material of the mold30so that the long protrusion32A does not lift from the mold30during thermal expansion. Similarly, the long protrusion42A held by the two holding portions422and422is preferably formed of the same material as the mold30or a material with a thermal expansion coefficient near the thermal expansion coefficient of the material of the mold30.

In the above-described embodiment, the skin1is positioned relative to the mold30by printing the first protrusion31and the second protrusion32, which are provided on the mold30, on the skin1; however, as shown inFIGS. 8A to 8C, similar advantages as obtained by providing the first protrusion31and the second protrusion32can be obtained by printing a first recessed part51and a second recessed part52, which are provided in the mold30, on the skin1.

The first recessed part51shown inFIG. 8Ais provided in place of the above-described first protrusion31. The first recessed part51is formed so as to be dented in a semispherical shape from the surface of the mold30.

The second recessed part52shown inFIG. 8Bis provided in place of the above-described second protrusion32. The second recessed part52is configured such that its length in the wing length direction can be changed between the lengths L1and L2of a short recessed part52A (FIG. 8B) and a long recessed part52B (FIG. 8C), respectively. The length L1of the long recessed part52B is longer than the length L2of the short recessed part52A. A space which is left inside the long recessed part52B when a part of the long recessed part52B, which is dented from the surface of the mold30, is filled with a member53corresponds to the short recessed part52A.

As shown inFIG. 9A, first, the short recessed part52A is provided as the second recessed part52in the mold30. Next, the material of the skin1is disposed on the mold30, and the material is heated and cured to mold the skin1. At this time, in the back surface of the skin1facing the mold30, a first protrusion15(FIG. 8A) is formed as mainly the resin flows into the first recessed part51, while a second protrusion16(FIG. 8B) is formed as mainly the resin flows into the short recessed part52A.

Here, as shown inFIG. 9B, the second protrusion16is printed by the short recessed part52A while the pitch P1between the first recessed part51and the second recessed part52has been enlarged to the pitch P2due to elongation of the mold30.

Thereafter, the skin1is removed from the mold30, and by the time the mold30is to be reset, the mold30has contracted to its original length as shown inFIG. 9C. When the member53filling a part of the long recessed part52B is removed, the space inside the short recessed part52A (indicated by the broken line) is extended toward the wing root side, and the long recessed part52B is formed.

As shown inFIG. 9D, in this state, when the first protrusion15(two-dot chain line) of the skin1is inserted into the first recessed part51and the second protrusion16(two-dot chain line) is inserted into the long recessed part52B, the skin1is positioned relative to the mold30.

Even when the mold30is subsequently elongated due to the heat applied during molding of the stringer2, the skin1is maintained in the positioned state as a relative shift of the second protrusion16inside the long recessed part52B is allowed.

It is also possible to provide, as the second recessed part52, a near recessed part and a far recessed part of the same length at the same positions as the near protrusion33A and the far protrusion33B shown inFIGS. 6A to 6D. In this case, the distance from the first recessed part51to the near recessed part in the wing length direction D is smaller than the distance from the first recessed part51to the far recessed part. The distance between the near recessed part and the far recessed part is set so that the far recessed part is located in a region of the near recessed part after its elongation during molding of the skin1. Thus, the second protrusion16can be inserted into the far recessed part when the skin1is reset on the mold30, so that the skin1is positioned at the two places of the first recessed part51and the far recessed part.

In the above-described embodiment, the stringer2is integrated into the skin1which has been reset on the mold30. However, the present invention is also adaptable to other uses which require resetting of a demolded fiber-reinforced plastic member on a mold, for other purposes than integrating one fiber-reinforced plastic member into the other fiber-reinforced plastic member. For example, the present invention can be applied for trimming the contour of the skin1by machining or boring a hole in the skin1after it is reset on the mold30. In addition, the present invention can also be applied for measuring the skin1by a three-dimensional measuring machine or a laser measuring machine while the skin1is reset on the mold30.

The present invention also encompasses a molding method in which the skin1and the stringer2are molded without involving evacuation of the air and only by the weight of the molding jig which presses the material of the skin1against the mold30or the weight of the mandrel20and the alignment jig40which press the material of the stringer2against the skin1.

Moreover, the present invention also encompasses the use of a pre-preg in place of the liquid resin and the fiber base material.

The present invention can be suitably used not only for the manufacture of the FRP structure with the skin and the stringer, but also for the manufacture of an FRP structure which includes a plate-like FRP member constituting various devices and structures and another FRP member reinforcing the plate-like FRP member.

In addition, the present invention can be widely used for manufacturing an FRP structure which integrates FRP members, regardless of the shape and the function of the FRP member.

The present invention is not limited to the above examples, but as long as within the scope of the present invention, it is possible to select some of the configurations described in the above embodiment, or to arbitrarily change some of the configurations into another configuration.