JP3474342B2 - Composite material with fracture progress prevention function and fracture progress prevention system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a crack generated in a material itself by an external force such as vibration and generates a compressive stress inside the material or a member to improve the rigidity strength of the material itself, thereby promoting the progress of fracture. The present invention relates to a composite material having a function of preventing the occurrence of damage and a fracture progress prevention system using the composite material.

[0002]

2. Description of the Related Art With respect to building structures and the like, laws and regulations stipulate the strength design of building materials used in consideration of unexpected external forces such as shock, vibration and earthquake. On the other hand, in order to reduce the load applied to the body of a building, a building material that is as lightweight as possible is required. Various materials have been developed so far as having both strength and lightness. For example,
Fiber-reinforced synthetic resin, aluminum-based composite materials, etc. are available.

[0003]

However, in the conventional composite material, in order to obtain the target strength, it is necessary to mix a large amount of fibers or metal filaments which are the reinforcing material, which makes the manufacturing difficult. As a result, the weight of the obtained product is increased. There is also a limit to the strength that can be achieved. Therefore, there are restrictions on applicable targets. The present invention is
It was devised to solve such problems. 2
A composite material that utilizes the characteristics of shape memory alloys that take various shapes and exerts a compressive stress on the material itself when an external force such as shock or vibration is applied to increase the strength of the material itself and prevent the progress of fracture. It is also an object of the present invention to provide a destruction progress prevention system.

[0004]

In order to achieve the object of the composite material of the present invention, one or more shape memory alloy wires or fibers are exposed on the composite material surface at both ends connected to a heating power source. It is characterized in that it is compounded in a matrix in a state. As the matrix, light resin such as synthetic resin, concrete, Al, Mg, Ti or alloys thereof is used. As a shape memory alloy, TiN
i, NiAl, CuZn, FeNiTiCo, TiN
b, MnCu, FeCrNi (stainless steel), etc. are used. A fracture progress prevention system using this composite material includes a composite material containing one or more shape memory alloy wires or fibers, and an acoustic elastic wave sensor or a thin film piezoelectric sensor attached to the surface of the composite material. The heated shape includes an arithmetic unit that outputs a control signal based on a signal input from the sensor, and an energization mechanism that supplies a heating current to the wire of the shape memory alloy based on the control signal. It is characterized in that the rigid body strength of the composite material is increased by improving the compressive force and the rigidity generated when the wire of the memory alloy undergoes the crystal phase transformation to return to the original length.

[0005]

The shape memory alloy memorizes the first shape by heat treatment in the high temperature austenite phase region above the reverse transformation point Af. Then, it is quenched at room temperature near the low temperature side martensitic transformation start point Ms to give a tensile prestrain to give a second shape. This shape memory alloy is
When heated to a temperature of point f or higher, the shape returns to the first shape, and its rigidity and strength are also improved by 2 to 3 times. In the present invention,
Taking advantage of this feature of the shape memory alloy, the shape memory alloy is heated to be deformed into the first shape when vibration or shock is applied, thereby exerting a compressive force on the composite material and improving rigidity. Specifically, as shown in FIG. 1, a shape memory alloy wire or fiber is compounded into a matrix. As the matrix, various synthetic resins, Al,
Light metals such as Ti, concrete, and building materials such as particle boards are used. A shape memory alloy wire or fiber is incorporated into the matrix (a), and heat treatment for shape memory is performed in this state (b). Next, tension is applied to give a pre-strain, and a shape in a room temperature state is formed (c). A composite material of this shape is incorporated into a device or structure as a building material, parts, etc., and the shape memory alloy is heated when vibration or impact is applied. When the heating temperature exceeds the Af point, the shape memory alloy becomes first
When the composite material tries to shrink into the shape (d), a compressive force acts on the composite material, and the rigidity is improved.

As a means for heating the shape memory alloy in response to applied vibration or shock, the structure shown in FIG. 2 is adopted. That is, the acoustic elastic wave sensor (A
E sensor) is attached, and the vibration and impact applied to the composite material are detected by the AE sensor. Alternatively, vibration or impact can be detected by a thinned piezoelectric sensor. The detected value is amplified by the amplifier (AE amplifier) and input to the oscilloscope and the calculator. The calculator analyzes the input acoustic elastic wave and determines whether or not a defect such as a crack has occurred in the composite material. When it is determined that a defect has occurred, a control signal is output from the arithmetic unit to the heating device, and a predetermined heating heat source is supplied to the shape memory alloy wire via the digital voltmeter. As the heat source for heating, steam, hot water, direct current resistance heating method, etc. are adopted. For example, a system using the direct current resistance heating method will be described. The shape memory alloy heated to a temperature of Af or higher by electric heating shrinks due to martensitic transformation, and a compressive force is applied to the composite material. As a result, the defects such as cracks generated inside the composite material are suppressed from propagating to the surroundings, and the progress of the destruction is prevented.

[0007]

EXAMPLE In order to observe the propagation of defects generated inside the composite material, a highly transparent acrylic resin was used in the matrix of the composite material, and the fibers of the shape memory alloy were compounded. For the shape memory alloy, the martensitic transformation start temperature Ms = 3
A Ti-50.2 atom% Ni alloy having a temperature of 1 ° C., a martensite transformation end temperature Mf = 1 ° C., an austenite transformation start temperature As = 57 ° C., and an austenite transformation end temperature Af = 63 ° C. was used. The stress-strain curve of this shape memory alloy is
As shown in FIG. 3, it was different depending on the temperature. The composite material used in the test had a thickness of 6 mm and a width of 13 mm as shown in FIG.
6 mm, height 20 mm, and 0.4 mm diameter Ti inside
Three Ni fibers were compounded at intervals of 5 mm. And 0.3 mm in width and 3.0 m in depth in the widthwise central part of the composite material.
A notch with a tip angle of 60 degrees was made at m.

A load of 300 N was applied to this composite material, and the optical stripe pattern generated around the notch was observed at room temperature and 80 ° C. This optical stripe pattern shows the stress distribution inside the material, and its number (order) is an index showing the magnitude of stress. Therefore, the wider the spread, the wider the applied load is. , Cracks (destruction) starting from the notch are likely to progress. As can be seen in FIG. 5, which compares the observation results, it is 80% compared to the striped pattern (a) at room temperature.
The striped pattern (b) when the Ti-Ni alloy was heated to
It was obviously smaller. From this fact, Ti-Ni
It is understood that the contraction force due to the martensitic transformation of the alloy acts on the composite material to prevent the progress of cracks. Also, Ti
When the relationship between the prestrain applied to the —Ni alloy and the striped pattern was investigated, stress propagation was suppressed to a narrower range as the larger prestrain was applied as shown in FIG. This means that the greater the prestrain, the greater the shrinkage force of the Ti—Ni alloy heated above the Af point, and the more the crack propagation is suppressed.

The case where a transparent acrylic resin is used for the matrix has been described above in order to observe the state of stress propagation inside the composite material. However, the generation of shrinkage force due to the shape change of the shape memory alloy also works in a composite material using another matrix material. Actually 600N for polycarbonate and acrylic synthetic resin blocks
When the force was applied, the crack progressed and the block broke.
However, in a composite material in which a Ti-Ni alloy wire having a pre-strain of 5% is mixed with the same synthetic resin, even if a TiN-Ni alloy wire is heated to 80 ° C and a force of 1000 N is applied, the crack progresses. I didn't see any. Similarly, in the composite material using an aluminum alloy as a matrix, a block made of the aluminum alloy itself broke with a force of 3000 N, whereas cracking did not progress even when a force of 5000 N was applied. Similarly, in a composite material using concrete as a matrix, a block made of concrete itself broke with a force of 2500 N, whereas cracking did not progress even when a force of 3000 N was applied.

[0010]

As described above, the present invention applies the compressive force to the inside of the composite material by utilizing the fact that the shape memory alloy recovers and deforms to the original memory shape when the temperature rises, and simultaneously occurs. Due to the increase in hardness of the alloy, the rigidity of the composite material is temporarily increased, and defects such as cracks are prevented from occurring and sudden fracture is suppressed. Moreover, since the shape memory alloy changes to the second shape when it returns to the steady state at room temperature, no internal stress is generated in the composite material. Therefore, it exhibits a large proof stress when an unexpected vibration or shock is applied, and has a required strength in a steady state, so that it is used as a functional material in a wide range of fields such as building materials, mechanical parts, and electric parts.

[Brief description of drawings]

FIG. 1 illustrates that a composite material according to the present invention improves rigidity.

FIG. 2 is a fracture progress prevention system according to the present invention.

FIG. 3 Temperature dependence of stress-strain curve of Ti—Ni alloy used in Examples

FIG. 4 is a composite material in which a Ti-Ni alloy wire is composited with acrylic resin.

FIG. 5: Stripe pattern representing stress propagation in a composite material at room temperature (a) and 80 ° C. (b)

FIG. 6 Pre-strain 0% (a), 1% (b), 3%
(C), a striped pattern representing stress propagation generated in a composite material in which 5% (d) Ti-Ni alloy is composited

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-212018 (JP, A) JP-A-7-48637 (JP, A) JP-A-6-264161 (JP, A) JP-A-6- 79714 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 5/04-5/06 B28B 23/02 C22C 1/09 C22C 14/00 C22C 49/00

Claims (5)

(57) [Claims] 1. A function of preventing a fracture from progressing, characterized in that one or a plurality of shape memory alloy wires or fibers are compounded into a matrix with both ends connected to a heat source for heating exposed on the surface of the composite material. Composite material. 2. A composite material in which the matrix according to claim 1 is a synthetic resin. 3. A composite material in which the matrix according to claim 1 is concrete. 4. A composite material in which the matrix according to claim 1 is aluminum, titanium or an alloy thereof. 5. A composite material containing one or more shape memory alloy wires or fibers therein, an acoustic elastic wave sensor or a thin film piezoelectric sensor attached to the surface of the composite material, and an input from the sensor. When a computing unit that outputs a control signal based on a signal, and a heating mechanism that supplies a heat source to the shape memory alloy wire based on the control signal, and the heated shape memory alloy wire undergoes a crystalline phase transformation A fracture progress prevention system in which the rigid body strength of the composite material is enhanced by improving the compressive force and rigidity of the composite material.