Repairing method, repairing structure and connecting structure of embedded optical fiber of composite material structure

A method of repairing an embedded optical fiber of a composite material structure including an embedded optical fiber embedded in a composite material, includes removing a portion of the composite material including a damaged portion of the embedded optical fiber to form an opening portion; polishing an end surface of the embedded optical fiber exposed in the opening portion and an end surface of the composite material exposed in the opening portion; and performing position adjustment such that a core of the polished embedded optical fiber and a core of a replacement optical fiber are aligned with each other, butting the end surface of the embedded optical fiber and an end surface of the replacement optical fiber with each other, and connecting the end surface of the embedded optical fiber and the end surface of the replacement optical fiber together.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of repairing a damaged portion of an optical fiber embedded in a structure made of a composite material, a repairing structure of the embedded optical fiber and a connecting structure of the embedded optical fiber.

2. Description of the Related Art

In recent years, composite material structures have been used in various fields. Since composite materials are smaller in weight and higher in strength and stiffness than metal materials, structures incorporating the composite materials can be reduced in weight. Therefore, for example, the use of the composite materials in structures of aircraft and the like has been expanding.

There may be a chance that an internal damage is generated in the composite material structure due to, for example, a collision of foreign objects against the composite material structure, or the like. Therefore, it becomes necessary to perform a design (dame tolerance design) which allows a damage which is unable to be found out in an inspection or a design (fail safe design) which prevents a damage from becoming fatal before a next inspection is conducted. A damage which is not allowable in design must be found out in inspection and repaired. Therefore, a visual inspection or a non-destructive inspection must be conducted from an inner surface side of fuselage as well as an outer surface of the fuselage. For some composite material structures having a complex shape or a complex curved surface, non-destructive inspection cannot be conducted. Accordingly, as a method of inspecting and diagnosing structural health, for example, the presence/absence of the damage in the composite material structure, for contributing to reduction of structure weight generated in the damage tolerance design and the fail safe design, reduction of cost/reduction of period/prevention of error/easiness of the visual inspection or the non-destructive inspection, there is proposed a damage detection system for detecting the damage or the like by using an optical fiber sensor embedded in the composite material.

As this type of prior art, for example, there is a dame detection device (in the embodiment, including a damage detection device which performs comparison of FBG (Fiber Bragg Grating) sensor measurement values of strains occurred by impact applied to the composite material and analysis values and uses a difference of strain response arrival time), in which a plurality of sensors (strain measurement FBG sensors, etc.) for reflecting optical signals with different frequencies are provided to be spaced apart from each other, in an optical path structure constructed using an optical fiber, such as a composite material structure embedded with the optical fiber, and the presence/absence, level or location of the damage are determined based on the presence/absence and intensities of the optical signals reflected in the sensors (optical intensity measurement), etc. (e.g., see Patent Literature 1: Japanese Laid-Open Patent Application Publication No. 2005-321223).

In the case of using the damage detection method as described above, if a damage occurs in the optical fiber embedded in the composite material, the damaged portion must be repaired. For example, as a repair method of an optical fiber as a single member, there is a method in which the damaged portion is cut, a replacement optical fiber is placed in a portion where the damaged portion is cut, and the replacement optical fiber is connected to the optical fiber by fusion splicing or in a state in which the end surface of the optical fiber and the end surface of the replacement optical fiber are butted with each other. However, the above repair method is unable to repair the optical fiber embedded in composite material structures.

Accordingly, as a repair method in the case where a damage occurs in the optical fiber embedded in the composite material, there is a method shown inFIGS. 14A to 14C. This method is as follows. If a damage200occurs in an embedded optical fiber110embedded in a composite material102of a composite material structure101(FIG. 14A), a replacement optical fiber120is bonded to the surface of a damaged portion of the composite material102by adhesive121(FIGS. 14B,14C), to connect the replacement optical fiber120to the embedded optical fiber110in a position apart from the damaged position.

As a repairing method in the case where a damage occurs in the optical fiber embedded in the composite material structure, there is a method in which the surface layer of the composite material is scraped out and removed, and the end portion of another optical fiber is joined to the end portion of the optical fiber, which corresponds to the removed portion of the composite material, by fusion-splicing etc. (see e.g., Patent Literature 2: Translated PCT Application Publication No. 2009-517680).

However, in the repairing method shown inFIG. 14, the embedded optical fiber itself is not repaired, and other healthy portion which cannot attain necessary transmitted light due to the damaged portion, as well as the damaged portion, cannot be used and is left. The optical fiber for use as the above stated optical fiber sensor has a core diameter of about 5 μm to 10 μm, and a cladding diameter of about 40 μm to 130 μm, for example. In the configuration in which the replacement optical fiber is bonded to the surface of the composite material and the end portion of the replacement optical fiber is connected to the optical fiber embedded in the composite material, problems associated with durability and reliability of the optical fiber bonded to the surface may sometimes arise. Especially, in the case of a smaller diameter optical fiber, a severe problem associated with durability and reliability might arise. Furthermore, in a certain composite material structure, the optical fiber cannot be placed in the surface. In that case, the above stated method cannot be applied.

In addition, as compared to the case where an optical fiber is embedded, in some cases, it becomes difficult to detect a damage accurately based on the presence/absence, intensity, or the like of an optical signal reflected by the optical fiber sensor.

In the repairing method disclosed in Patent Literature 2, the above stated embedded optical fiber having the damaged portion might be further damaged when the corresponding portion of the composite material is scraped out and removed from the surface layer. Thus, it is difficult to draw out the embedded optical fiber in a healthy state. Because of this, it is difficult to repair the optical fiber sensor to a state in which it is capable of detecting a damage and others accurately again or to repair the optical fiber to a state in which it is capable of attaining necessary transmitted light again.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide an embedded optical fiber repairing method, a repairing structure, and a connecting structure of a composite material structure, which can repair an entire embedded optical fiber by replacing a damaged portion of the embedded optical fiber by a replacement optical fiber when the embedded optical fiber embedded in a composite material is damaged.

To achieve the above object, according to the present invention, there is provided a method of repairing an embedded optical fiber of a composite material structure including an embedded optical fiber embedded in a composite material, comprising: removing a portion of the composite material including a damaged portion of the embedded optical fiber to form an opening portion; polishing an end surface of the embedded optical fiber exposed in the opening portion and an end surface of the composite material exposed in the opening portion; and performing position adjustment such that a core of the polished embedded optical fiber and a core of a replacement optical fiber are aligned with each other, butting the end surface of the embedded optical fiber and an end surface of the replacement optical fiber with each other, and connecting the end surface of the embedded optical fiber and the end surface of the replacement optical fiber together. In specification and claims, the term “embedded optical fiber” is defined as an optical fiber embedded in the composite material, and the term “replacement optical fiber” is defined as an optical fiber placed in the damaged portion to replace the portion of the embedded optical fiber removed from the composite material. In accordance with this configuration, even when the embedded optical fiber embedded in the composite material is damaged, the embedded optical fiber can be repaired in such a manner that the damaged portion of the embedded optical fiber is removed together with the composite material, and then is replaced by the replacement optical fiber within a range of a plate thickness.

The replacement optical fiber may have an optical fiber array at an end portion thereof, and an end surface of the optical fiber array and the end surface of the embedded optical fiber may be connected together by bonding. In accordance with this configuration, the position of the embedded optical fiber after polishing is detected, and the optical fiber array of the replacement optical fiber can be bonded to the polished embedded optical fiber by means of adhesive. Thus, the optical fiber array and the embedded optical fiber can be joined together easily.

The method may comprise, after polishing the end surface of the embedded optical fiber and the end surface of the composite material, emitting a light from a light source into the embedded optical fiber, the light source being provided at an end portion of the embedded optical fiber which is at an opposite side of the damaged portion; detecting the light of the light source at the end surface of the embedded optical fiber exposed in the opening portion; and determining that a position at which an intensity of the light is highest is a position of the core of the embedded optical fiber, aligning the core of the replacement optical fiber with the core of the embedded optical fiber, and connecting the end surface of the embedded optical fiber and the end surface of the replacement optical fiber together. In accordance with this configuration, since the intensity of the light is detected at the damaged portion of the embedded optical fiber, the position of the core of the embedded optical fiber can be detected accurately and quickly. This makes it possible to quickly align the core of the replacement optical fiber with the core of the embedded optical fiber.

The embedded optical fiber may include a light reflection device, and the method comprise after polishing the end surface of the embedded optical fiber and the end surface of the composite material, applying an incident light through the polished end surface of the embedded optical fiber; and detecting the light reflected by the light reflection device, determining that a position at which an intensity of the light is highest is a position of the core of the embedded optical fiber, aligning the core of the replacement optical fiber with the core of the embedded optical fiber, and connecting the end surface of the embedded optical fiber and the end surface of the replacement optical fiber together. In accordance with this configuration, the embedded optical fiber including the light reflection device such as an FBG sensor, is capable of quickly detecting the core position of the embedded optical fiber by utilizing the light reflected by the light reflection device, which makes it possible to quickly align the core of the replacement optical fiber with the core of the embedded optical fiber.

The method may comprise holding the replacement optical fiber connected to the embedded optical fiber on the composite material structure by one of surfaces of the composite material structure and closing the opening portion by the other surface of the composite material structure. In accordance with this configuration, it becomes possible to repair the embedded optical fiber while suppressing reduction of a strength of the composite material structure which would be caused by removing the portion of the composite material including the damaged portion of the embedded optical fiber.

The method may comprise bonding and stacking composite material thin plates together in the opening portion, and embedding the replacement optical fiber connected to the embedded optical fiber between the composite material thin plates to close the opening portion. The “composite material thin plates” include both of cured hard plates and uncured soft plates (prepreg). In accordance with this configuration, since the opening portion formed by removing the damaged portion of the embedded optical fiber together with the portion of the composite material is filled with the stacked composite material thin plates, reduction of a strength of the composite material structure can be suppressed. In this case, by forming the opening portion with a conical shape, a good bonding strength is attained between the stacked composite material thin plates and the composite material structure in the vicinity thereof. As a result, highly reliable repair is realized.

According to the present invention, there is provided a repairing structure of an embedded optical fiber of a composite material structure, which is repaired by any of the above stated embedded optical fiber repairing methods, in which the replacement optical fiber connected to the end surface of the damaged portion of the embedded optical fiber is held by a replacement optical fiber holding member provided on one of surfaces of the composite material structure, and a reinforcement member for closing the opening portion is provided on the other surface of the composite material structure provided with the replacement optical fiber holding member. The reinforcement member may be a composite material or metal such as titanium alloy. This reinforcement member is attached by means of boding or fastening using a fastener member such as bolts. In accordance with this configuration, after the damaged portion of the embedded optical fiber embedded in the composite material structure is replaced by the replacement optical fiber within a range of the plate thickness, the replacement optical fiber can be held in the repaired portion, and reduction of a strength of the composite material structure corresponding to the repaired portion, can be suppressed. Thus, repair is performed to attain the highly reliable optical fiber.

According to the present invention, there is provided a connecting structure of an embedded optical fiber for connecting an optical fiber array to an embedded optical fiber embedded in a composite material structure, wherein the embedded optical fiber has a polished surface in a portion corresponding to an end surface of the composite material structure; and the optical fiber array is connected to the end surface of the embedded optical fiber by bonding in a state in which position adjustment is performed in such a manner that a core of the embedded optical fiber and a core of an optical fiber provided with the optical fiber array are aligned with each other at the polished surface of the embedded optical surface. In accordance with this configuration, even when a peripheral portion of the composite material structure embedded with the embedded optical fiber is cut, the optical fiber array is connected to the embedded optical fiber corresponding to the cut surface to form a continuous optical fiber, which can be performed easily.

The above and further objects, and features of the invention will more fully be apparent from the following detailed description with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments described below, for example, aircraft (fuselage, wings, rudder, etc.) will be described as a specific example of a structure incorporating a composite material structure. Hereinafter, as a composite material2forming a composite material structure1, for example, a material in which prepreg sheets made of a matrix of polymer resin such as epoxy resin are stacked together in a plate thickness direction and cured, is used. The prepreg (abbreviation of pre-impregnated materials) sheets are an intermediate base material for molding in which the matrix resin is pre-impregnated with a fiber-reinforced base material. Hereinafter, as an example of an embedded optical fiber10and a replacement optical fiber20, a description will be given of an example in which an optical fiber having a smaller diameter is used in view of embedding into the composite material structure1, as will be described later.

It is supposed that a damage is generated in the embedded optical fiber10embedded in the composite material structure1, along with damage to the composite material structure1. It is also supposed that the presence/absence and position of the damage are measured by the above stated transmitted light intensity measurement or FBG sensor strain measurement, and identified accurately by non-destructive inspection or the like.

Initially, a description will be given of an overall procedure of a repairing method in a case where a damage200is generated in the embedded optical fiber10embedded in the composite material structure1, with reference toFIGS. 1 to 3.

As shown inFIG. 1A, when the damage200is generated in the embedded optical fiber10embedded in the composite material structure1made of the composite material2, a portion of the composite material2including a damaged portion is removed together as shown inFIG. 1B. The portion of the composite material2is removed by forming a circular opening portion (through-hole)3having a diameter of about 30 mm. Then, an end surface10aof the embedded optical fiber10which is exposed in the opening portion3is polished together with an end surface2aof the composite material2.

Then, as shown inFIG. 2, an embedded optical fiber repairing device30detects the position of the polished end surface10aof the embedded optical fiber10, and the end surface of the replacement optical fiber20is moved to and butted with the polished end surface10aof the embedded optical fiber10, and they are bonded and joined together by adhesive. The embedded optical fiber repairing device30ofFIG. 2is capable of detecting the position of the polished end surface10aof the embedded optical fiber10, moving the replacement optical fiber20to that position, and butting the end surface of the replacement optical fiber20with the end surface10aof the embedded optical fiber10, which occurs automatically. The detail will be described later.

The embedded optical fiber repairing device30of the present embodiment is provided with a vacuum chuck31suctioned to the outer surface of the composite material structure1. For example, as shown inFIG. 4, the vacuum chuck31is suctioned and fastened to the outer surface of an aircraft80. Although in the present embodiment, the embedded optical fiber repairing device30is suctioned to and supported on the outer surface of the aircraft80by using the vacuum chuck, the embedded optical fiber repairing device30may be installed on a foothold assembled on a floor surface. If the aircraft80is shaking, it becomes relatively easy to perform automatic alignment of the core of the replacement optical fiber20, by suctioning the embedded optical fiber repairing device30onto the outer surface of the aircraft80and supporting it thereon, because the embedded optical fiber repairing device30is shaking as well. The embedded optical fiber repairing device30may be supported by a method adapted to an object to be repaired, a repair position, etc. The method is not limited to the present embodiment.

As shown inFIG. 2, the embedded optical fiber repairing device30includes an optical fiber moving section32at an upper portion thereof. The replacement optical fiber20in this example is provided with an optical fiber array (connecting device for joining an optical waveguide element to optical fiber)21at an end portion thereof. Therefore, the optical fiber moving section32is an optical fiber array moving section32(assigned with the same reference symbol as the optical fiber moving section) for performing position adjustment such that the optical fiber array21and the embedded optical fiber10are connected together. The optical fiber array moving section32has an automatic core alignment function for adjusting the position of the optical fiber array21held with 6 degrees of freedom (six axes). The 6 degrees of freedom means that the optical fiber array21is capable of being displaced along X-axis, Y-axis and Z-axis and being rotated around X-axis, Y-axis and Z-axis as indicated by arrows ofFIG. 2.

As described above, the optical fiber array moving section32is capable of automatically aligning the optical fiber array21which is the end portion of the replacement optical fiber20, with the position of the embedded optical fiber10, within the opening portion3, with 6 degrees of freedom. The optical fiber array moving section (optical fiber moving section)32preferably has 5 to 6 degrees of freedom, or may have degrees of freedom which are less than 5 to 6 degrees.

Then, as shown inFIG. 3, the replacement optical fiber20with the optical fiber arrays21at both ends connected to the embedded optical fiber10is held by a replacement optical fiber holding member4provided on an inner surface side of the composite material structure1. A reinforcement member5is bonded to or fastened by a fastener member to the outer surface of the repaired portion of the composite material structure1such that the reinforcement member5closes the opening portion3from the outer surface. The reinforcement member5supports a load applied to the repaired portion and renders a strength of the composite material structure1in a portion corresponding to the opening portion3equal to or higher than that before repair. The reinforcement member5may be a composite material2or metal such as titanium alloy. This makes it possible to replace the damaged embedded optical fiber10with the replacement optical fiber20within a range of its plate thickness, and repair the optical fiber embedded in the composite material structure1.

As shown inFIG. 5, the opening portion3may have a conical shape, and may be closed in such a manner that composite material thin plates6are stacked together and filled therein, and the replacement optical fiber20joined to the embedded optical fiber10is embedded therein. The composite material thin plates6may be desired plates which are cured hard plates or uncured soft plates. In this case, the composite material thin plates6may be stacked from a direction of one surface of the composite material structure at an opposite side where the embedded optical fiber repairing device30is disposed, and when they reach the position of the embedded optical fiber10, the replacement optical fiber20is connected to the position of the embedded optical fiber10, and then the composite material thin plates6may be stacked up to the other surface of the composite material structure.

In the above described configuration, since the opening portion3having the conical shape is filled with the stacked composite material thin plates6, a good bonding strength is attained between the stacked composite material thin plates6and the composite material structure1in the vicinity thereof, which can achieve repair with high reliability. Note that the shape of the opening portion3filled with the composite material thin plates6is not limited to the conical shape.

Then, with reference toFIGS. 6 and 7, the flow of the repair of the embedded optical fiber10by the embedded optical fiber repairing device30ofFIG. 2will be described more specifically. Hereinafter, a description will be given of a work which occurs such that after a damaged portion is generated in the embedded optical fiber10, along with damage to the composite material structure1and the damaged position is identified accurately by a non-destructive inspection or the like, a portion of the composite material2including the damaged portion of the embedded optical fiber10is cut, the exposed surface of the embedded optical fiber10, which corresponds to the cut portion, is polished, and then the optical fiber array21provided at the end portion of the replacement optical fiber20is connected to the end surface10aof the embedded optical fiber10left in the composite material2.

Firstly, as shown inFIG. 6, the embedded optical fiber repairing device30includes an optical fiber position detecting section34for detecting the position of the embedded optical fiber10embedded in the cut portion of the composite material2. The optical fiber position detecting section34is capable of detecting a core position of the embedded optical fiber10by light emitted from a light source35provided at the other end of the embedded optical fiber10.

The optical fiber moving section32is provided at an upper portion thereof with the optical fiber array holding section41for holding the optical fiber array21provided at the end portion of the replacement optical fiber20. The optical fiber moving section32is capable of adjusting the position of the optical fiber array21held, with 6 degrees of freedom. The 6 degrees of freedom is controlled by drivingly controlling the position of the optical fiber moving section32, by using a stepping motor33. Further, as adhesive for connecting the optical fiber array21to the embedded optical fiber10as will be described later, in the present embodiment, ultraviolet cured resin is used, and an ultraviolet ray radiation device37is provided to cure the ultraviolet cured resin.

The replacement optical fiber20provided at one end with the optical fiber array21is connected at the other end to a light detector36to detect the light emitted from the light source35. In the present embodiment, the optical fiber array21is connected to the light detector36by means of an optical fiber44provided at one end with an adapter43connectable to the optical fiber array21. The adapter43conforms in shape to the optical fiber array21and is capable of connecting the optical fiber44. In this example, a general FC optical fiber connector45is provided at an intermediate portion of the optical fiber44connecting the adapter43to the light detector36. In this way, a connecting work is made easier by simply connecting the optical fiber44by means of the connector.

The optical fiber array moving section32, the optical fiber position detecting section34and the light detector36are connected to a control personal computer38. Various signals such as position information and light detection information are stored in the control personal computer38. The control personal computer38is configured to control the respective sections. The control personal computer38causes the optical fiber array moving section32to automatically align the core of the optical fiber array21with respect to the core of the embedded optical fiber10.

In accordance with this configuration, in the embedded optical fiber repairing device30, the optical fiber array21can be connected to the end surface of the embedded optical fiber10embedded in the composite material structure1, in a state in which a light loss is least.

Next, connection of the replacement optical fiber20by the embedded optical fiber repairing device30will be described with reference toFIG. 7. Hereinafter, a description will be given of a procedure performed after the damaged portion of the embedded optical fiber10is cut together with the portion of the composite material2. The portion of the composite material2is cut in such a manner that the opening portion (through-hole)3having a predetermined diameter is formed in the composite material structure1. The size of the opening portion3is determined by a spacing of the embedded optical fiber10, the size of the optical fiber moving section32of the repairing device, a movable range thereof, a damage range of the composite material structure1, etc.

(1) [Preprocessing of Repaired Portion: Polish End Surface of Embedded Optical Fiber]

Firstly, the end surface of the embedded optical fiber10which faces the opening portion3formed in the composite material structure1is polished. This polishing is performed in such a manner that the end surface of the embedded optical fiber10and the cut surface of the composite material2are polished together.

(2) [Device Connection: Connection of Optical Fiber to Device]

Then, the optical fiber position detecting section34of the embedded optical fiber repairing device30is placed in the opening portion3, and one end of the embedded optical fiber10embedded in the composite material2is connected to the light source35. Also, the opposite end portion of the replacement optical fiber20provided with the optical fiber array21is connected to the light detector36.

(3) [Detection of Position of Optical Fiber]

Then, the optical fiber position detecting section34of the embedded optical fiber repairing device30detects the core position of the embedded optical fiber10based on the transmitted light emitted from the light source35. The optical fiber position detecting section34detects that the position at which the intensity of the light emitted from the light source35is highest is the core position of the embedded optical fiber10. In this example, with this operation, the core position of the embedded optical fiber10is stored in the control personal computer38included in the embedded optical fiber repairing device30.

(4) [Replacement Between Optical Fiber Position Detecting Section and Optical Fiber Array]

Then, at the core position of the embedded optical fiber10stored in the control personal computer38, replacement between the optical fiber position detecting section34and the optical fiber array21is performed. This position adjustment is performed accurately by the position control by the optical fiber array moving section32having an automatic core alignment function. If the embedded optical fiber10is detected by the optical fiber position detecting section34from a location deviated from the core position rather than a location which is straight in front of the embedded optical fiber10, replacement between the optical fiber position detecting section34and optical fiber array21may be omitted.

Next, the optical fiber array moving section32performs position control of the optical fiber array21to cause the optical fiber array21to perform scan, and the light detector36probes the position at which the intensity of the light emitted from the light source35is highest.

Then, the embedded optical fiber repairing device30connects the optical fiber array21to the end surface of the embedded optical fiber10by means of the adhesive. As the adhesive, for example, ultraviolet cured resin is used, and the ultraviolet ray radiation device37radiates an ultraviolet ray to cure the ultraviolet cured resin. This allows the optical fiber array21of the optical fiber20to be connected to the end surface of the embedded optical fiber10to form a continuous optical fiber. Thus, the embedded optical fiber10is repaired. Although in the present example, the optical fiber array21is connected to the embedded optical fiber10by means of the ultraviolet cured resin, they may be connected together by means of another adhesive. As the ultraviolet cured resin or another adhesive, an ultraviolet cured resin or adhesive having a refractive index substantially equal to that of the optical fibers10,20to be connected together is used.

Through the above steps, a work for connecting the optical fiber array21provided at one end of the replacement optical fiber20to the end surface10aof the embedded optical fiber10at one side, is completed.

Then, the optical fiber array21provided et the other end of the replacement optical fiber20is connected to end surface10aof the other embedded optical fiber10. When the other end of the replacement optical fiber20is connected, the light source35is connected to the end of the other embedded optical fiber10, and the light detector36is connected to the end of the embedded optical fiber10to which the light source35was connected when the replacement optical fiber20was connected to the embedded optical fiber10previously.

Then, the light detector36detects the light emitted from the light source35. Automatic core alignment is performed assuming that the position at which the light intensity is highest is the core position of the embedded optical fiber10. The optical fiber array21provided at the other end is connected to the end surface10aof the embedded optical fiber10by means of the adhesive.

Through this step, a work for connecting the optical fiber arrays21provided at the both ends of the replacement optical fiber20to the both end surfaces10aof the embedded optical fiber10exposed in the opening portion3, is completed. Thus, a work for repairing the embedded optical fiber10is completed.

Next, a description will be given of examples of configurations different from that of the embedded optical fiber repairing device30, and procedures for connecting the replacement optical fiber20using the embedded optical fiber repairing devices, with reference toFIGS. 8 to 10. In the examples described below, the optical fiber arrays21are provided at the end portions of the replacement optical fiber20and the optical fiber array moving section32for moving the optical fiber arrays21is included in the device. As described above, the optical fiber array moving section32is configured to linearly move and rotate the optical fiber array21with 6 degrees of freedom (linear movement along X-axis, Y-axis and Z-axis and rotation around X-axis, Y-axis and Z-axis), to perform automatic core alignment. In these examples, the light detector36detects the light emitted from the light source35, and the position at which the light intensity is highest is stored as the core position of the embedded optical fiber10in the control personal computer38(FIG. 6). The control personal computer38and the like will not be described in repetition.

An embedded optical fiber repairing device40of Embodiment 2 ofFIG. 8is an embodiment in which the optical fiber array21is moved to the core position of the embedded optical fiber10and its core is automatically aligned with the core of the embedded optical fiber10without using the optical fiber position detecting section34of Embodiment 1. The same components as those inFIG. 6are identified by the same reference symbols and will not be described.

In accordance with the embedded optical fiber repairing device40, the end surface10aof the embedded optical fiber10facing the opening portion3is polished, the optical fiber array21is moved to the end surface10aof the embedded optical fiber10, and the light detector36detects the light emitted from the light source35. It is supposed that the position at which the light intensity is highest is the core position of the embedded optical fiber10, and the control personal computer38can automatically align the core of the optical fiber array21. Therefore, in accordance with the embedded optical fiber repairing device40of the present embodiment, alignment of the core of the optical fiber array21with respect to the core of the embedded optical fiber10can be performed quickly, and repair of the embedded optical fiber10can be performed quickly. In addition, the optical fiber array holding section41of the optical fiber array moving section32can be reduced in size, and can be easily put into the opening portion3provided in the repaired portion of the composite material structure1.

The adapter43facilitates a connecting work of the replacement optical fiber20or the optical fiber44connected to the light detector36, which makes it possible to quickly and efficiently repair the embedded optical fiber of the composite material structure1.

Because of the above, the embedded optical fiber repairing device40of the present embodiment can quickly repair, for example, the fuselage and the like of the aircraft, and provide a repairing method with high reliability which can quickly repair the composite material structure1which is limited in repair time.

Next, Embodiment 3 ofFIG. 9will be described. In the present embodiment, the embedded optical fiber10has an FBG sensor11, and the core alignment is performed by using a reflected light intensity of the FBG sensor11. In the present embodiment, the same components as those inFIG. 6are identified by the same reference symbols and will not be described.

In the present embodiment, also, the optical fiber array21is connected to the light detector36by means of the optical fiber44provided at one end with the adapter43conforming in shape to the optical fiber array21and connectable to the optical fiber array21. The optical fiber44is connected by means of the general FC optical fiber connector45. The optical fiber connector45of this example is configured to allow an incident light of the light source35and the reflected light of the FBG sensor11to pass therethrough.

The optical fiber44connected by means of the optical fiber connector45is connected to the light source35and to the light detector36via a circulator51. The circulator51sends an incident light52from the light source35to the optical fiber array21via the optical fiber connector45, and send reflected light53from the FBG sensor11to the light detector36. In the present embodiment, also, connection of the optical fiber44is easily performed by using the optical fiber connector45.

In accordance with the embedded optical fiber repairing device50, the optical fiber array holding section41of the optical fiber array moving section32can be reduced in size, and can be easily put into the opening portion3provided in the repaired portion of the composite material structure1.

In addition, the core alignment of the optical fiber array21is performed based on the reflected light intensity of the FBG sensor11, and thus accurate connection of the optical fiber array21is attained. Furthermore, the adapter43and the optical fiber connector45facilitate a connecting work of the replacement optical fiber20or the optical fiber44connected to the light detector36, which makes it possible to quickly and efficiently repair the embedded optical fiber of the composite material structure1.

Because of the above, the present embodiment can quickly repair, for example, the fuselage and the like of the aircraft, and provide a repairing method with high reliability which can quickly repair the composite material structure1which is limited in repair time.

In Embodiment 3, the embedded optical fiber10has the FGB sensor11. In the case of the embedded optical fiber10which does not include the FGB sensor11, a light reflection device similar to the FGB sensor may be attached at an opposite side of the end surface10aof the embedded optical fiber10, in the opening portion3. By doing so, the light refection device reflects the incident light52like the FGB sensor11, the light detector36detects the intensity of the reflected light53, the core alignment of the optical fiber array21is performed, and accurate connection of the optical fiber array21is performed.

Next, Embodiment 4 ofFIG. 10will be described. In the present embodiment, as shown inFIG. 8, an embedded optical fiber repairing device60includes two optical fiber array holding sections41for holding two optical fiber array21are disposed above two optical fiber array moving sections32, respectively, and the optical fiber arrays21held by the optical fiber array holding sections41are oriented outwardly in opposite directions. The detailed configuration is identical to that ofFIG. 8and will not be illustrated and described.

In accordance with this example, the optical fiber array holding sections41hold the optical fiber arrays21provided at both ends of the replacement optical fiber20, respectively, and the light detector36detects the light emitted from the light source35to connect the optical fiber array21of the replacement optical fiber20to the end surface10aof the embedded optical fiber10ofFIG. 8, and the core alignment of the optical fiber arrays21is performed, for each of both ends of the replacement optical fiber20. This makes it possible to automatically align the cores of the two optical fiber arrays21provided at both ends of the replacement optical fiber20to the cores of the embedded optical fiber10almost at the same time.

In the case of the embedded optical fiber repairing device60, it is preferable that the optical fiber array holding sections41of the optical fiber array moving sections32are reduced in size so that they are easily put into the opening portion3provided in the repaired portion of the composite material structure1.

By the work similar to that ofFIG. 8, it becomes possible to connect the optical fiber arrays21provided at both ends of the replacement optical fiber20to the two portions of the embedded optical fiber10facing the opening portion3, almost at the same time. Thus, the embedded optical fiber of the composite material structure1can be repaired quickly and efficiently.

Because of the above, the present embodiment can quickly repair, for example, the fuselage and the like of the aircraft, and provide a repairing method with high reliability which can quickly repair the composite material structure1which is limited in repair time.

As shown inFIGS. 11 and 12, in a connecting structure for connecting the embedded optical fiber10embedded in the composite material structure1to the optical fiber arrays21, an end surface angle may be 90 degrees or may be inclined (e.g., 45 degrees). The end surface of the optical fiber array21may be decided according to conditions of the repaired portion, the core diameter of the optical fiber, the cladding diameter of the optical fiber, etc.

A connecting structure70ofFIG. 11is an example in which the end surface angle of the composite material structure1provided with the embedded optical fiber10is 90 degrees. In this case, the end surface angle of the optical fiber array21connected to the embedded optical fiber10is also 90 degrees.

A connecting structure71ofFIG. 12is an example in which the end surface angle of the composite material structure1provided with the embedded optical fiber10is 45 degrees. In this case, the end surface angle of the optical fiber array21connected to the embedded optical fiber10is also 45 degrees.

The embedded optical fiber10of the composite material structure1and the optical fiber array21which are connected together by means of the above stated connecting structure are aligned with respect to each other such that cores of the optical fibers conform to each other, and bonded together by means of ultraviolet cured resin.

Test results of the connecting portions of the optical fibers connected by the above stated connecting structures70,71will be described hereinafter. In this test, the optical fiber array21provided at the end portion of the optical fiber to be connected is connected to the embedded optical fiber10exposed at the end surface of the composite material structure1embedded with the embedded optical fiber10, and the intensity of the transmitted light is measured after the connecting. A test environment is such that a room temperature and a normal humidity.

The composite material structure1used in the test is made of a carbon fiber reinforced epoxy resin composite material cured at 180 degrees C. The embedded optical fiber10embedded in the composite material structure1is a polyimide coating small-diameter optical fiber (single mode), and has a core diameter of 8.5 μm, a cladding diameter of 40 μm, and a coating diameter of 48 μm.

A test was conducted for each of a case of connecting the embedded optical fiber10of the composite material structure1to the optical fiber array21with the end surface angle of 90 degrees and a case of connecting the embedded optical fiber10of the composite material structure1to the optical fiber array21with the end surface angle of 45 degrees.

When the optical fiber array21is connected to the end surface of the embedded optical fiber10, the core of the embedded optical fiber10and the core of the optical fiber array21are aligned with each other by using an automatic core alignment device. After the core alignment is completed, the embedded optical fiber10of the composite material structure1and the optical fiber array21are fastened together by means of the ultraviolet cured resin.

Then, the light intensity of each connecting portion of the embedded optical fiber10connected as described above was measured. In measurement of the light intensity, a single-mode optical fiber cord (attached with FC connector at one end; communication single mode quartz optical fiber) is fusion-bonded to an exposed portion of the small-diameter embedded optical fiber10embedded in the composite material structure1, by a fusion-splicing connecting device. The light source is connected to the optical fiber cord connector side, while the light detector is connected to the optical fiber array side, to measure the intensity of the light transmitted through the optical fiber cord, the small-diameter optical fiber, and the optical fiber array. The measurement was made in such a manner that a center wavelength of the light source was 1550 nm, and a wavelength range of the light detector was 0.75 to 1.7 μm.

FIG. 13is a table list showing results of measurement of light intensity in the test in the above example. Evaluation of the results of the test are as follows.

In evaluation of the results of test, comparison was made for the light intensities after the core alignment and connection, with respect to the light intensities of the light source. The light loss was 6.8 dB in the case of the end surface angle of 90 degrees and 8.1 dB in the case of the end surface angle of 45 degrees. As can be seen from the results, it may be determined that the light loss generated by connecting the optical fiber array21to the embedded optical fiber10is a level at which the optical fiber can be operated as the optical fiber sensor in a damage detection system provided in the composite material structure1. It may be presumed that each value of the light loss contains a light loss in a portion other than the connecting portion at which the optical fiber array21is connected to the embedded optical fiber10, and therefore a value of the light loss generated only in the connecting portion at which the optical fiber array21is connected to the embedded optical fiber10is much smaller than the each value.

Since it is necessary to connect the embedded optical fiber10embedded in the composite material structure1to a measurement instrument provided outside, it is necessary to take out the embedded optical fiber10from a peripheral portion of the composite material structure1, or to provide the connector connected to the embedded optical fiber10in the peripheral portion of the composite material structure1. However, it is required that the peripheral portion of the composite material structure1be trimmed in manufacture to allow the composite material structure1to have a predetermine dimension. Therefore, it is difficult to take out the embedded optical fiber10from the peripheral portion of the composite material structure1, or to provide the connector in the peripheral portion of the composite material structure1. As a solution to this, Japanese Laid-Open Patent Application Publication No. 2003-315601 discloses a manufacturing method of a structure. However, in accordance with the above stated connecting structures70,71, even when the peripheral portion of the composite material structure1is trimmed in manufacture of the composite material structure1embedded with the embedded optical fiber10, the optical fiber array21can be connected to the embedded optical fiber10by polishing the end surface of the embedded optical fiber10together with the end surface of the composite material structure1after the trimming. Therefore, the connecting structures70,71can be configured without a need for the use of a special connector to connect the embedded optical fiber10to the measurement instrument provided outside.

Although in the above embodiments, the composite material structure1of the aircraft has been exemplarily described, the damaged portion of the optical fiber10in composite material structures having other structures can be repaired. The present invention is in no way limited to the above embodiments.

The above embodiments are merely exemplary and can be changed in various ways without departing from the spirit of the present invention. The present invention is in no way limited to the above embodiments.

The embedded optical fiber repairing method of the present invention is utilized in composite material structures for which damage caused by an impact, or the like, are detected by using embedded optical fibers, like the aircraft.