JP2004301517A - Damage detecting sensor using inorganic composite material having conductive particles dispersed therein and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a damage detecting sensor constituted so as to enable sensing of high sensitivity in a low strain region. <P>SOLUTION: The damage detecting sensor 1 is constituted so as to be equipped with a fragile matrix 4, a conductive route comprising conductive particles 14 dispersed in the fragile materix 4 and fibers 24 arranged in the fragile matrix 4 to reinforce the fragile matrix 4. By using the fragile destructive behavior of the fragile matrix 4, the highly sensitive sensing of a damage can be performed in the low strain region. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention aims to apply the soundness of a social infrastructure structure to a diagnosis (health monitoring) technique. In particular, by combining conductive particles with an inorganic material, the use as a self-diagnosis function material is improved. The present invention relates to a damage detection sensor using an inorganic composite material provided.
[0002]
[Prior art]
In recent years, expectations for technologies for diagnosing the soundness of social infrastructure structures have increased. For example, rapid deterioration of concrete structures has become a social problem, and there is a need for a technology for diagnosing damage to concrete members.
In structural materials and building structures, it is known that an optical fiber is used for detecting deformation, distortion, and damage generated inside the material (sensor function) (Patent Document 1). When an optical fiber is used, its assembly cost and detection system cost are high. Also, the optical fiber itself is susceptible to damage and may be damaged inside the material. In this case, it is impossible to detect deformation, strain, and damage. Further, a strain gauge can be attached to the surface of the structure to detect deformation or the like. However, the gauge can detect only the state of the structure surface, and cannot detect the internal state.
[0003]
Further, a self-diagnosis material has been disclosed which forms a phase of conductive particles in a structure or a molded body provided to the structure, and detects deformation or the like in the structure as a change in conductivity (Patent Document 2). It is also disclosed that a glass fiber bundle impregnated with carbon powder or reinforced plastic containing carbon fiber is used as a self-diagnosis material (Patent Document 3). With these materials, damage detection can be performed by using a change in electrical resistance of the material itself due to a structural change in the conductive particle phase or the like. However, when diagnosing damage to building structures, these materials exhibited sensitive sensing in the low strain region (0.2%) and change properties of electrical resistance insufficient to diagnose cumulative damage.
[0004]
[Patent Document 1]
JP 2001-249035 A
[Patent Document 2]
JP-A-9-100356
[Patent Document 3]
JP 2001-41774 A
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a damage sensor that can perform high-sensitivity sensing in a low strain region.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the present inventors have focused on a matrix having a brittle fracture behavior intentionally, instead of a matrix having elastic deformation and toughness conventionally used to hold conductive paths. By dispersing conductive particles in a brittle matrix and combining fibers with the matrix, it has been found that a highly sensitive damage sensor can be constructed over a wide range from a low strain region.
According to these findings, the following means are provided.
[0007]
(1) a damage detection sensor,
A brittle matrix;
A conductive path by conductive particles dispersed in the brittle matrix,
A reinforcing material disposed in the brittle matrix to strengthen the matrix,
A sensor comprising:
(2) The sensor according to (1), wherein the reinforcing material is a fiber arranged in the brittle matrix two-dimensionally or three-dimensionally with a predetermined direction.
(3) The sensor according to (1), wherein the reinforcing material is a fiber arranged in the brittle matrix in a non-directionally dispersed state.
(4) The sensor according to any one of (1) to (3), wherein the conductive particles are contained in an amount of 20 wt% or more and 50 wt% or less based on the total weight of the brittle matrix and the conductive particles.
(5) The sensor according to any one of (1) to (4), wherein the brittle matrix is glassy.
(6) The vitreous matrix has the following composition;
PbO ₂ 10 wt% or more and 45 wt% or less,
B ₂ O ₃ 15 wt% or more and 30 wt% or less,
SiO ₂ 20 wt% or more and 40 wt% or less and
Al ₂ O ₃ 5 wt% or more and 10 wt% or less
The sensor according to (5), which is a glass having:
(7) The conductive particles are RuO ₂ , IrO ₂ , RhO ₂ , Bi ₂ Ru ₂ O ₇ , Pb ₂ Ru ₂ O ₇ , Pb ₂ Ru ₂ O _6.5 And In ₂ O-SnO ₂ The sensor according to any one of (1) to (6), wherein the sensor is at least one member selected from the group consisting of:
(8) The sensor according to any one of (1) to (7), wherein the reinforcing material is contained in an amount of 5 to 50 vol% based on a total volume of the matrix and the conductive particles.
(9) The sensor according to any one of (1) to (8), wherein the surface includes a coating phase containing a resin.
(10) By measuring a change in the electric resistance value of the conductive path, it is possible to detect at least one of a strain amount, a deformation amount, and a damage degree of the building to which the sensor is mounted. (1) to (9) The sensor according to any one of the above).
(11) The sensor according to any one of (1) to (9), wherein by measuring a change in electric resistance and a residual electric resistance of the conductive path, it is possible to detect a cumulative damage of a structure equipped with the sensor. .
(12) A method for detecting damage to a structure,
A method comprising the step of measuring the conductivity of said conductive path of a sensor according to any of (1) to (11) provided inside or on a surface of a construct.
[0008]
Since the sensor of the present invention includes the brittle matrix, the conductive particles, and the fibers, it is possible to perform high-sensitivity sensing in a low strain region of the building, and further, it is possible to predict the damage history and the life of the building.
The advanced sensing of the sensor of the present invention can be explained by, for example, the following mechanism. FIG. 1 shows one form of the composite phase 2 having the fibers 24 arranged so as to have directionality. In the composite phase 2 having the brittle matrix 4 and the conductive particles 14, the brittle matrix 4, fine cracks 34 are likely to occur even in the low strain region. The fine cracks 34 reduce the contact between the conductive particles 14. As the fracture further progresses, the number of the fine cracks 14 increases, and the contact of the conductive particles 14 further decreases, and the fine cracks 34 also occur in the particles 14. On the other hand, according to the composite form of the present invention, since the matrix 4 is reinforced by the fibers 24, even if the fine cracks 34 occur and increase, the existence of the cracks 34 is allowed to maintain the present composite phase 2. Can be. The sensor of the present invention enables highly sensitive sensing in a low strain region by such a mechanism.
Further, since the sensor of the present invention maintains the fine cracks in the composite phase 2, it is possible to maintain the changed conductivity. Therefore, the present sensor can store the damage history.
From the above, it can be said that the present sensor utilizes the brittle fracture behavior of the composite phase 2 having the brittle matrix 4.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIG. 2 showing one embodiment of the sensor 1 of the present invention. The embodiment shown in FIG. 2 is a preferred embodiment of the present sensor, but the present sensor is not limited to the exemplified sensor.
The present sensor 1 has a composite phase 2 including a conductive particle 14, a brittle matrix 4, and a reinforcing material 24 such as a fiber. As shown in FIG. First, the microcracks 34 are generated in the brittle matrix 4, and the fracture behavior is taken such that the microcracks 34 in the matrix 4 increase and / or increase due to an increase in stress. Further, the reinforcing material 24 itself having high strength is It is preferable that the matrix 4 in a region where the reinforcing material 24 is densely present without being damaged has a breaking behavior such that the matrix 4 is greatly damaged. That is, it is desirable to adopt a form that enables high-sensitivity sensing using the brittle fracture behavior of the brittle matrix 4 and that can delay the progress of fracture by reinforcing the brittle matrix 4 with the reinforcing material 24.
[0010]
The conductive path in the present sensor 1 has a continuous contact form of conductive particles 14 (hereinafter, also referred to as a percolation structure) as shown in FIG.
The form of the conductive path itself is not particularly limited. For example, it can take a linear, planar, tubular, or designed two-dimensional or three-dimensional shape. Further, a form in which the conductive paths of these forms are stacked may be included.
It can be appropriately selected according to the type and direction of the stress to be detected or possibly generated.
The conductive particles 14 constituting the conductive path can be used without particular limitation as long as they are particles 14 having conductivity. For example, conductive ceramics such as carbon, conductive metal oxides and metal nitrides, metals, and conductive plastics can be used. As the conductive material, the electric resistance (ρ) (Ωcm) at 300 K is 2.3 × 10 ^-2 The following is preferred. More preferably, 1.5 × 10 ^-3 It is as follows.
[0011]
For example, as the conductive ceramics, titanium nitride and the like can be mentioned, but preferably, RuO is used. ₂ , IrO ₂ , RhO ₂ , Bi ₂ Ru ₂ O ₇ , Pb ₂ Ru ₂ O ₇ , Pb ₂ Ru ₂ O _6.5 And In ₂ O-SnO ₂ It is. This is because the conductive particles 14 made of these ceramics are susceptible to a small stress when subjected to a stress, so that the particles themselves have a sensitive change in electric resistance to a low stress. Preferably, RuO ₂ And more preferably RuO ₂ It is also possible to use only. In addition, as the conductive particles 14, one kind or a combination of two or more kinds can be used.
[0012]
The form of the conductive particles 14 is not particularly limited. The particles 14 can be spherical, flake-like (flake-like), whisker-like, fiber-like, rod-like, or the like. As the conductive particles, particles having such a form can be used alone or in combination of two or more.
The size of the conductive particles is not particularly limited, but is preferably 10 nm to 0.5 μm.
[0013]
The conductive particles 14 are preferably contained in a range of 20 wt% or more and 50 wt% with respect to the total weight of a brittle matrix described later and the conductive particles. If it is less than 20 wt%, it becomes difficult to form a percolation structure, and the conductivity becomes too low, so that the function as a sensor is hardly exhibited. On the other hand, when the content exceeds 50 wt%, the conductivity is good, but the conductive particles are aggregated in the matrix to form a non-uniform dispersion state, and the proportion of the brittle phase is relatively reduced. Brittle fracture occurs, and it becomes difficult to exhibit the brittle fracture behavior to be obtained in the present invention.
[0014]
The conductive path of the conductive particles 14 by the percolation structure is used as a damage detection sensor while being held by the brittle matrix 4. More preferably, the brittle matrix 4 is further coated with a coating phase 44 described later.
Here, the matrix 4 means a medium that directly holds the conductive particles 14. If the conductive paths are held in the matrix 4, the conductive paths will be present in the brittle matrix 4 as a conductive phase.
[0015]
The matrix 4 needs to have low conductivity so that a change in electric resistance in the conductive path can be detected. It is preferable that the conductive particles 14 have substantially no conductivity or are insulative as compared with the conductive particles 14. In particular, the use of an insulating material is important for ensuring the accuracy of the conductive path.
In addition, from the viewpoint of ensuring the ability to detect damage by the conductive path, it is preferable that the matrix 4 has a non-permeable component, particularly a conductive component such as water, which affects conductivity. In particular, when the present sensor is installed in a cement-based material portion such as concrete or mortar of a structure, a conductive path is embedded in a matrix 4 such as a water-impermeable resin, or a conductive path is provided. Alternatively, or in combination therewith, the conductive paths can be coated with a water-impermeable material.
[0016]
The brittle matrix 4 is made of a material that allows the retained conductive paths to function as the structural damage sensor 1.
In the present invention, the term “brittle” refers to a property of a material having a poor deforming ability until a fracture is caused by the action of an external force. Therefore, the material constituting the brittle matrix is usually a vitreous material or a ceramic material.
In the present invention, the brittle matrix 4 is preferably glassy. Since the firing temperature can be easily controlled by adjusting the composition and composition of the glass, and it can be fired at a low temperature, there is almost no thermal stress at the interface between the conductive particles and the glass. This is because it is also possible to adjust the electric resistance and lower the temperature coefficient of resistance (for example, close to zero). In addition, by making the temperature coefficient of resistance close to zero, the effect of temperature can be eliminated when applying the present sensor 1 to a building. Further, glass has an advantage in production and a composite form that glass has high wettability to ceramic fibers and conductive particles during firing.
[0017]
The vitreous material is not particularly limited, but preferably has a composition that can be fired at 1000 ° C. or lower. If the temperature exceeds 1000 ° C., the possibility of deterioration of the ceramic fibers due to oxidation increases. From this viewpoint, PbO-B is preferably used. ₂ O ₃ -SiO ₂ A system glass can be used. Further, more preferably, PbO ₂ 10 wt% or more and 45 wt% or less, B ₂ O ₃ 15 wt% or more and 30 wt% or less, SiO ₂ 20 wt% or more and 40 wt% or less and Al ₂ O ₃ It is preferable that the composition be 5 wt% or more and 10 wt% or less. This is because the glass formation temperature exceeds 1000 ° C. outside the composition range. In particular, PbO ₂ Is less than 10 wt%, RuO ₂ This is because the dispersibility of is reduced.
[0018]
The present composite phase 2 contains, in addition to the brittle matrix 4 and the conductive particles 14, a reinforcing material 24 that can reinforce the matrix 4 or the composite phase 2.
The material is glass, ceramics, plastic, or the like, but it is necessary that the material does not hinder the electrical characteristics of the conductive path, the compounding ratio and the compounding form. Preferably, glass and ceramic insulating materials are used. For example, alumina or mullite fibers can be used.
Such a reinforcing material 24 may be in an irregular shape, a spherical shape, on a flake, or in a particle shape such as a whisker, but is preferably a fibrous body such as a continuous fiber (unidirectional fiber), a long fiber, and a short fiber. More preferably, it is a continuous fiber having a length approximately equivalent to the size of the sensor.
[0019]
The form of the fiber may be a single fiber form, but may be a fiber bundle, a linear body, a fiber of an appropriate length may be entangled, or a woven or knitted sheet-like or It may be an elongated tape-like body. Further, a two-dimensional or three-dimensional net-like skeleton, entangled body, and woven fabric may be formed by a fiber bundle or a single fiber. In the case where the fiber has a two-dimensional or three-dimensional form due to compounding or the like, in such a form, the form of the detection material can be determined by itself. That is, the sensor 1 also has a function of giving a desired shape.
[0020]
The presence form of the reinforcing material 24 in the matrix 4 is not particularly limited, but may be uniformly present in the matrix 4 or localized in the matrix 4. Preferably, the fibrous material 24 is localized in the matrix 4. According to the localized form, when an external stress is applied, first, fine cracks 34 are generated in the brittle matrix 4, and the fine cracks 34 gradually increase due to an increase in the stress, and thereafter, the reinforcing material 24 or the density of the reinforcing material 24 is reduced. A fracture behavior in which the high matrix 4 region is damaged can be easily obtained. If the destruction behavior is obtained, highly sensitive damage sensing can be performed. Alternatively, it is considered that a destructive behavior in which the fine cracks 34 are simultaneously generated in the localized region and the non-existent region of the reinforcing material 24 in the matrix 4, and the sensing function is considered to be improved.
[0021]
Further, it is preferable that the reinforcing material 24 be present in the matrix 4 with a direction. Preferably, a continuous form of the reinforcing material is arranged in a direction approximately along the external stress. According to this embodiment, the brittle fracture behavior can be realized while imparting a certain resistance to external stress.
[0022]
As a preferred form of the reinforcing material 24, a form (for example, a continuous fibrous body) which is ultimately susceptible to external stress itself has a direction (for example, along the direction of stress), A mode in which they are arranged in the brittle matrix 4 can be given. That is, in the present sensor 1, one of the preferable forms of the reinforcing material 24 is a form in which the reinforcing material 24 is two-dimensionally or three-dimensionally arranged in the matrix 4 with a predetermined direction. Such an embodiment is illustrated in FIGS. In these embodiments, as the reinforcing material 24, a bundle of continuous fibers is linearly, that is, two-dimensionally, arranged in a matrix. The three-dimensionally arranged form includes a form in which such linear bodies are arranged in a three-dimensional network.
By arranging the fibers in such a direction, it becomes possible to detect a strain due to an external force along the direction with high sensitivity. As described later, when a structure in which a reinforcing material is arranged two-dimensionally or three-dimensionally is used, the composite phase 2 can be easily formed along with the fiber. Therefore, the conductive path and the present composite phase 2 which are two-dimensionally or tertiarily designed can be obtained depending on the arrangement state of the fibers.
[0023]
Another form of the reinforcing material 24 is a form in which a material that is less likely to be subjected to stress itself or is less likely to be damaged even when subjected to stress (for example, a short fibrous body) is present in a random orientation. The distribution of the reinforcing material 24 in the brittle matrix 4 is made different. That is, the high density part and the low density part of the reinforcing material 24 are formed in the matrix 4. Also in this mode, a preferable brittle fracture behavior mode in the present composite phase 2 can be formed.
[0024]
The sensor essentially has the fiber material 24 in the matrix 4, but as a result of the fiber material 24 being localized in the matrix 4, the reinforcing material 24 is not included, and the conductive particles 14 And a second phase 3 comprising a matrix 4. As described above, the sensing level and the like can be adjusted by the second phase 3.
For example, the second phase 3 is on the outer peripheral side of the fiber bundle in the sensor 1 of the embodiment shown in FIG. In such a case, the composite phase 2 of the present invention is present in the inner region of the outline of the fiber bundle 24 and the region near the outer periphery of the outline, and in the outer region separated from the outline, the second phase 3 is provided. Can be said.
Since the second phase 3 does not contain a reinforcing material, brittle fracture behavior is likely to occur. According to the combination with the composite phase 2 of the present invention, damage in a low strain region is caused by the presence of the second phase 3. And deformation can be detected at a higher level. That is, in the second phase 3, a sequential brittle fracture behavior such as a decrease in conductivity first and then a decrease in conductivity in the present composite phase may occur, or the second phase and the composite Since a brittle fracture behavior that is complex with the phase (including simultaneous cases) can also occur, it is considered that the sensing function is improved.
[0025]
In the present sensor 1, a directional reinforcing material existing form and a non-directional reinforcing material existing form can be used in combination.
It is preferable that the reinforcing material 24 is provided at 5 vol% or more and 40 vol% or less with respect to the total volume of the brittle matrix 4 and the conductive particles 14. If it is less than 5 vol%, it is difficult to exhibit the reinforcing properties of the brittle matrix. If it exceeds 40 vol%, the degree of dispersion of the conductive particles is reduced, and the brittleness is too high and the brittle fracture is stable in a low strain region. Is less likely to occur. Preferably, it is 10 vol% or more and 30 vol% or less.
[0026]
The form of the present sensor 1 is not particularly limited. If necessary, any three-dimensional shape other than a sheet shape, a bar shape, a fiber shape, an elongated tape shape, or the like can be used. The form of the detection material may be the external form of the matrix material itself. When the external form of the matrix material itself is used as the form of the present sensor, the form can be given to the matrix material by a molding method of the material. As described above, the form may be in accordance with the form of the structure constructed by the reinforcing material contained in the matrix 4.
[0027]
The size of the present sensor can be made to correspond to the construction to be applied or its application location. The length may correspond to the entire length or a part of the length of the structure to be applied in the standing direction.
[0028]
Such a sensor can be obtained by using various conventionally known molding methods according to the type of the brittle matrix material or the type or form of the fiber or the like contained in the matrix.
Usually, the present detection material can be obtained by molding a composition in which a brittle matrix material and conductive particles are blended. As a molding method, a conventionally known method for molding a brittle material can be employed. Further, the present sensor can be obtained by using a composite technique of a brittle material and another component.
[0029]
Further, in order to make the brittle matrix contain a reinforcing material such as a fiber, for example, in the case of non-directional arrangement, the brittle matrix can be uniformly mixed with a composition containing the matrix material and the conductive particles and molded. . In the case of continuous fibers or fiber structures having a two-dimensional or three-dimensional morphology, these fiber structures may be embedded in a matrix material composition, or these fiber structures may be combined with a matrix material and conductive particles. Can be imparted by dipping in a slurry of a composition containing According to such a method, the composition permeates between the fiber structure or the fiber material, and the present composite phase is formed near the fiber material.
In addition, by applying the matrix material composition along the directionally continuous fibers or fiber structure portions, a conductive path having directionality in the fiber direction or along the fiber structure portions can be formed.
When the brittle matrix material is vitreous or ceramics, the composite phase is finally obtained by firing. When the reinforcing material is a ceramic fiber, it is preferable to perform firing at 1000 ° C. or less in consideration of deterioration of the reinforcing material. When a vitreous material is used for the matrix, the firing temperature is preferably 700 ° C. or higher. If the temperature is lower than 700 ° C., it is difficult to obtain a sufficient fired state, and a glass material cannot be obtained.
When a vitreous matrix is adopted, a technique of dipping a fiber structure in a slurry of a glass composition is effective.
[0030]
When a ceramic material is used as the matrix material, the present sensor can be obtained by applying a conventionally known method of forming and processing various ceramics. Regarding the compounding of the conductive particles or the reinforcing material, a conventionally known method of compounding these materials can be applied.
[0031]
Note that the above-described manufacturing method is merely an example, and the manufacturing method of the present sensor is not limited to this. Depending on the type and form of these materials, one or more methods known to those skilled in the art may be used. It can be applied in combination.
[0032]
In order for this sensor to effectively perform the damage detection function in the structure to which it is applied, it protects the electrical characteristics of the conductive paths it contains so that it is not hindered by factors derived from the structure or other sources It is preferred that Such causes include water, alkali, acid and the like, but it is particularly preferable that intrusion of water is avoided. Further, when applied to a concrete structure, it is preferable that alkali resistance is secured.
Therefore, the present sensor preferably includes a carrier (also referred to as a coating phase) that protects the detection material from such various causes outside the matrix. The coating phase preferably has, for example, both insulating properties and / or impermeability to moisture. Most preferably, both of these are provided. Specifically, a vinyl ester resin, which is an insulating resin having excellent workability, and an epoxy resin, which is an insulating resin having excellent alkali resistance, can be given.
[0033]
The coating phase is preferably formed as one or two or more layered coating phases around the matrix, but the form is not limited to a layer. In addition, also in such a coating phase, a reinforcing material such as the above-mentioned glass long fiber which can be contained in the matrix can be blended. Thereby, the detection material and / or the structure can be reinforced.
[0034]
Further, when applied to a structure, a material having a function of being stably held at a predetermined position in the structure, not causing a slip upon deformation of the structure, and / or Alternatively, a fixing material having a form can be added. Such a fixing material is preferably a polymer material having an insulating property, and preferably contains an insulating fiber (continuous fiber, long fiber or short fiber) such as vinylon, aramid, or glass. As an example, a linear body made of a continuous fiber or a fiber bundle and an insulating resin such as vinyl ester can be provided on at least a part of the outer periphery of the detection material in a convex shape. For example, with respect to an elongated rod-shaped detection material, it is possible to prevent slippage at the interface with the concrete phase by winding such a linear body around the detection material in a helical manner.
[0035]
A terminal, a lead wire, or the like can be provided at an end of the conductive path of the present sensor. It becomes possible to detect a change in the electric resistance value or the like in the conductive path via such a terminal or a lead wire. The terminals and the like can be mounted after forming the matrix containing the conductive paths and before forming the covering phase.
The method of measuring the electric resistance value or the like can be used regardless of the type. As a method of measuring the electric resistance value, there are a constant current / voltage measurement method, a low voltage / current measurement method, a method using a bridge circuit, and the like, but the type is not limited in the present invention. Further, in diagnosing damage, continuous measurement and periodic measurement can be mentioned as a method of measuring the electric resistance value. In these measurements, the measurement time, interval, frequency, and the like can be arbitrarily selected according to the form and scale of the structure and the form and scale of the estimated damage.
[0036]
The structure to which the present sensor is applied is not particularly limited. It can be applied to various constructs. The present invention can also be applied to ground or water structures such as buildings, bridges, dams, and elevated structures, and various underground structures.
[0037]
In applying the present sensor to a structure, the sensor may be provided in at least a part of the structure. In the case of a concrete structure, it may be embedded or installed on the surface. Preferably, it is a part of a metal part (eg, metal bolt) of shotcrete, lining concrete, or reinforced concrete. It is also preferable to apply to a cement-based material application site (mortar portion and concrete portion) for repair or the like.
[0038]
When installed on a surface, for example, it can be installed on these surfaces with an organic adhesive such as an epoxy resin adhesive, or, instead of or together with the use of an adhesive, such as mortar or concrete. It can be installed on these surfaces by coating and fixing with a cement-based material. Further, the method of installing on these surfaces can be applied to a method of spraying a cement-based material.
In addition, the method of installing on the surface is a method mainly for an existing building.
[0039]
Also, when buried inside the concrete part or the site where the cement-based material is applied, for example, in order to fix the concrete, the surroundings of the detection material are made uneven, and fixed to a formwork etc. before concrete casting. Fixing and fixing by concrete hardening. This method is effective for new construction. Moreover, when repairing the concrete of the existing building, the concrete can be buried by the same method when re-casting the concrete.
Furthermore, in addition to repairing the concrete of an existing building, a linear groove is formed on the concrete surface, and a detecting material is installed in the groove, and then the groove is cemented or resin-based. It can also be installed by filling with.
The method of burying inside is mainly for new construction or existing construction that needs repair. A typical form of internal embedding is, for example, a form in which a detection material is buried as a continuum having a sufficient length in the traveling direction or arch direction of the tunnel structure as a dedicated shape. When a detection material containing a reinforcing material is applied, there is a feature that the effect is higher in a method of burying the inside in comparison with a method of installing the detection material on the surface.
[0040]
The arrangement position, the arrangement direction, the number of arrangements, and the arrangement interval of the present detection material in the structure can be freely designed and constructed, and the optimum design can be performed according to the form of the structure or the form of the estimated damage. .
[0041]
Since the present sensor has the above configuration, the conductivity (electric resistance) of the conductive path changes when external stress such as strain, deformation, or damage is applied. Since the magnitude of the external stress and the amount of change in the electric resistance have a fixed relationship, the amount of the external stress applied to the sensor can be known from the measured electric resistance.
In particular, the present sensor is capable of high-sensitivity sensing, for example, detecting deformation of a reinforcing bar, by providing a continuous contact form of conductive particles in a brittle matrix reinforced by a reinforcing material. % Sensing in a low strain region of less than or equal to%.
[0042]
Further, the present sensor can exhibit an irreversible change in that the change in the electric resistance value when the deformation acts is not restored to the initial value even after unloading and remains. From the evaluation of the residual resistance value, it is possible to diagnose the maximum deformation or damage history given in the past. As a result, in structures using this sensor, the maximum damage at the time of a disaster can be diagnosed based on the measurement of changes in electrical resistance after a disaster such as an earthquake, or the damage history can be diagnosed from the residual resistance. Thus, diagnosis can be performed by regular monitoring instead of constant monitoring. From this viewpoint, it can be said that the present sensor is a sensor that can store the damage history.
The monitoring can be performed using a communication line or the like. For example, by transmitting related information such as electric resistance value measured using the present detection material to an output device at a remote place via a communication means and outputting the same, damage can be easily detected even at a remote place. And monitoring becomes possible.
[0043]
According to the present invention, by applying the present sensor to a structure and measuring its electric resistance value, not only can the state of deterioration / deformation in the structure be diagnosed simply and quickly with high accuracy, but also two-dimensional detection of a plurality of detection materials can be performed. The arrangement enables the estimation of an abnormal part, and furthermore, the application of the irreversibility of the electric resistance change enables the diagnosis of the history of damage (including the maximum damage).
[0044]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to FIGS. These examples are intended to specifically explain the present invention, and do not limit the present invention in any way by these examples.
[0045]
(Example 1: Production of sensor)
In this example, a sensor having the form shown in FIG. 2 was manufactured. FIG. 3 shows a process of manufacturing the sensor.
RuO ₂ Powder (average particle size 0.02-0.1 µm) and 20 wt% PbO ₂ -40wt% B ₂ O ₃ -5wt% Al ₂ O ₃ -35wt% SiO ₂ Glass (Please tell me the specific glass composition) and an organic solvent such as terpineol ₂ A glass slurry having a weight ratio of 30 wt%: 40 wt%: 30 wt% of glass and resin was prepared.
Next, a fiber bundle of continuous alumina fibers having a length of 400 mm (filament diameter: 10 μm, bundle of about 1000 monofilaments) is prepared, and about 25 cm of the central portion of the continuous fiber bundle is immersed in the prepared slurry. Then, the slurry was infiltrated into the surface of the continuous fiber bundle and the inside of the bundle.
[0046]
The fiber bundle after dipping was dried at 100 ° C. and then baked at 900 ° C. for 40 minutes. Thereby, the composite phase of the present invention was formed in the dipping portion. The composite phase comprises a glassy matrix inside and around the fiber bundle and RuO dispersed in the matrix. ₂ Contains particles.
Further, electrode terminals for measuring electric resistance were attached to both ends of the fired body. After the electrode processing, the resultant was cut into a curable composition containing a vinyl ester resin material and glass fiber, and heated at 130 ° C. to form a vinyl ester resin coating phase on the sensor surface.
A ring for holding by a tester was provided at the end for evaluation by a tensile test.
[0047]
(Example 2: Tensile test)
Using the sensor manufactured in Example 1, a tensile test was performed.
In the tensile test, the load was gradually increased, and changes in stress and electric resistance until final fracture were detected. The result is shown in FIG.
FIG. 5 shows the measurement results of the change in electric resistance with respect to the time when a constant load of 500 N at which a strain of about 0.2% is applied 1,000 times repeatedly (one cycle 50 seconds). FIG. 6 shows the change in the residual electric resistance at this time.
[0048]
As shown in FIG. 4, the electrical resistance gradually increased as the load increased until the final failure. From FIG. 4, even in a low strain region of 0.13% or less, a large change in electric resistance of 600% or more was exhibited, and it was found that the sensor manufactured in Example 1 can perform high-sensitivity sensing. Also, a sharp increase in electrical resistance in the 0.1% strain region means that a brittle fracture in the matrix has caused significant damage that hinders contact of the conductive particles.
The above results support the development and increase of fine cracks in the composite phase. In particular, a large change in electrical resistance in the region of about 0.1% strain caused the fine cracks between the conductive particles to increase or increase at once. I support that.
[0049]
In addition, as shown in FIG. 5, the electric resistance gradually increases under a constant load (500 N). These facts suggest that the sensor manufactured in Example 1 may have a residual electric resistance phenomenon.
As shown in FIG. 6, the residual electric resistance increased with the number of cycles. From this result, it was found that the sensor manufactured in Example 1 can store the damage history using the residual electric resistance value. By using this phenomenon, information on the history of damages caused in the past may be stored using the residual electric resistance of this composite material. From such a change in the residual electric resistance, it is possible to monitor the fatigue phenomenon (cumulative damage and / or fatigue damage) of the structure and predict the life.
[0050]
Based on the above results, glass-based composite materials in which conductive particles of ruthenium oxide are dispersed utilize the phenomenon of increased electrical resistance due to brittle fracture characteristics. Thus, highly sensitive damage detection is possible in the lower strain range (less than 0.2%). Since it generates residual electrical resistance, it is used as a self-diagnosis material for monitoring fatigue phenomena of structures and predicting life. In other words, the present material can be used for the health diagnosis (health monitoring) technology of a social infrastructure structure.
[0051]
【The invention's effect】
According to the present invention, it is possible to provide a damage sensor capable of performing high-sensitivity sensing in a low strain region.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of the action of a composite phase in a sensor of the present invention.
FIG. 2 is a view showing an embodiment of the sensor of the present invention, FIG. 2 (a) is a cutaway view, and FIG. 2 (b) is a cross-sectional view taken along a plane orthogonal to the length direction. FIG. 2C is a cross-sectional view along the length direction.
FIG. 3 is a view schematically showing a manufacturing process of the sensor of the present invention.
FIG. 4 is a graph showing changes in electrical resistance and strain during a tensile test of the sensor manufactured in Example 1.
FIG. 5 is a graph showing a change in electric resistance and a strain when the sensor manufactured in Example 1 is repeatedly subjected to a load (500 N, 1 cycle: 50 seconds).
FIG. 6 is a graph showing a change in residual electric resistance when a repeated load is applied to the sensor manufactured in Example 1 (500 N, 1 cycle: 50 seconds).
[Explanation of symbols]
1 sensor
2 Composite phase
3 Second composite phase
4 Brittle matrix
14 conductive particles
24 Reinforcement materials
34 crack
44 Coating phase

Claims (12)

A damage detection sensor,
A brittle matrix;
A conductive path by conductive particles dispersed in the brittle matrix,
A reinforcing material disposed in the brittle matrix to strengthen the matrix,
A sensor comprising: The sensor according to claim 1, wherein the reinforcing material is a fiber arranged in the brittle matrix two-dimensionally or three-dimensionally with a predetermined direction. The sensor according to claim 1, wherein the reinforcing material is a fiber that is non-directionally dispersed in the brittle matrix. The sensor according to any one of claims 1 to 3, wherein the conductive particles are contained in an amount of 20 wt% or more and 50 wt% or less based on the total weight of the brittle matrix and the conductive particles. The sensor according to claim 1, wherein the brittle matrix is vitreous. The vitreous matrix has the following composition;
PbO ₂ 10 wt% or more and 45 wt% or less,
B ₂ O ₃ 15 wt% or more and 30 wt% or less,
A glass having a SiO ₂ 20 wt% or more 40 wt% or less and _Al 2 _O 3 5wt% or more to 10wt%, the sensor of claim 5, wherein. The conductive _particles are selected from _{RuO 2, IrO 2, RhO 2} , Bi 2 Ru 2 O 7, Pb 2 Ru 2 O 7, Pb 2 Ru 2 O 6.5 and _{In 2} O-SnO 2 the group consisting of The sensor according to any one of claims 1 to 6, wherein the sensor is one or more types. The sensor according to any one of claims 1 to 7, wherein the reinforcing material is contained in an amount of 5 to 50 vol% based on a total volume of the matrix and the conductive particles. The sensor according to any one of claims 1 to 8, wherein the surface includes a coating phase containing a resin. 10. The structure according to claim 1, wherein at least one of a strain amount, a deformation amount, and a degree of damage of the building equipped with the sensor can be detected by measuring a change in the electric resistance value of the conductive path. The sensor as described. The sensor according to any one of claims 1 to 9, wherein by measuring a change in electric resistance and a residual electric resistance of the conductive path, it is possible to detect a cumulative damage of a structure equipped with the sensor. A method for detecting damage to a structure,
A method comprising measuring the conductivity of the conductive phase of a sensor according to any of claims 1 to 11, which is provided inside or on a structure.

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