U.S. patent application number 10/516617 was filed with the patent office on 2006-05-11 for extremely fine shape memory alloy wire, composite material thereof and process for producing the same.
Invention is credited to Yoshio Akimune, Teruo Kishi, Kazuhiro Otsuka, Nobuyuki Toyama, Ya Xu.
Application Number | 20060099418 10/516617 |
Document ID | / |
Family ID | 30431065 |
Filed Date | 2006-05-11 |
United States Patent
Application |
20060099418 |
Kind Code |
A1 |
Xu; Ya ; et al. |
May 11, 2006 |
Extremely fine shape memory alloy wire, composite material thereof
and process for producing the same
Abstract
Disclosed is a shape memory alloy wire subjected to a cold
drawing work, which comprises a shape memory alloy in a martensitic
phase which assumes an austenitic phase or a martensitic phase
through phase transformation temperatures, has a diameter of 60
.mu.m or less, and has a reverse transformation termination
temperature of at least 250.degree. C. By using the alloy wire, a
composite material having the alloy wire embedded in a resin having
a molding temperature as high as 180.degree. C., such as a glass
fiber reinforced resin or a carbon fire reinforced resin, without
fixing of both wire ends.
Inventors: |
Xu; Ya; (Ibaraki, JP)
; Otsuka; Kazuhiro; (Ibaraki, JP) ; Toyama;
Nobuyuki; (Ibaraki, JP) ; Akimune; Yoshio;
(Ibaraki, JP) ; Kishi; Teruo; (Ibaraki,
JP) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Family ID: |
30431065 |
Appl. No.: |
10/516617 |
Filed: |
June 4, 2003 |
PCT Filed: |
June 4, 2003 |
PCT NO: |
PCT/JP03/07084 |
371 Date: |
August 29, 2005 |
Current U.S.
Class: |
428/375 ;
148/402; 148/563 |
Current CPC
Class: |
Y10T 428/2933 20150115;
G01C 3/08 20130101 |
Class at
Publication: |
428/375 ;
148/402; 148/563 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2002 |
JP |
2002162286 |
Claims
1. A shape memory alloy wire subjected to a cold drawing work,
which comprises a shape memory alloy in a martensitic phase which
assumes an austenitic phase or a martensitic phase through phase
transformation temperatures, has a diameter of 60 .mu.m or less,
and has a reverse transformation termination temperature of at
least 250.degree. C.
2. The shape memory alloy wire according to claim 1, which has a
cold drawing rate of at least 20%.
3. The shape memory alloy wire according to claim 1 or 2, wherein
the shape memory alloy is a Ti--Ni alloy.
4. A composite material which comprises a fibrous material and a
resin, wherein the fibrous material comprises the shape memory
alloy wire according to any one of claims 1 to 3.
5. A composite material which comprises a fibrous material and a
resin, wherein the fibrous material comprises the shape memory
alloy wire according to any one of claims 1 to 3 and at least one
fiber selected from a glass fiber and a carbon fiber.
6. The composite material according to claim 4 or 5, wherein the
resin comprises a thermosetting resin or a thermoplastic resin.
7. The composite material according to claim 4 or 5, wherein the
resin comprises a precured material of a thermosetting resin.
8. The composite material according to claim 4 or 5, wherein the
resin comprises a thermoset product of a thermosetting resin.
9. The composite material according to any one of claims 4 to 8,
wherein the thermosetting resin comprises an epoxy resin.
10. A composite material which comprises a cured resin comprising
the shape memory alloy wire according to any one of claims 1 to 3,
wherein the shape memory alloy wire is heated to a temperature of a
reverse transformation termination temperature thereof or higher to
generate a contractive force.
11. The composite material according to claim 10, which comprises
at least one fiber selected from a glass fiber and a carbon fiber
together with the shape memory alloy wire.
12. The composite material according to claim 10 or 11, wherein
said heating of the shape memory alloy wire is carried out by
application of electric current to the wire.
13. A process for producing a composite material, which comprises
heat-curing a thermosetting resin or a precured material thereof
comprising the shape memory alloy wire according to any one of
claims 1 to 3 at a temperature which is a reverse transformation
starting temperature of the shape memory alloy wire or higher and
is lower than the reverse transformation termination temperature;
and then heating at least a part of the shape memory alloy wire to
a temperature of its reverse transformation final temperature or
higher.
14. The process according to claim 13, wherein the thermosetting
resin or the precured material thereof comprises at least one fiber
selected from a glass fiber and a carbon fiber.
15. The process according to claim 13 or 14, wherein said heating
of the shape memory alloy wire is carried out by application of
electric current to the wire.
Description
TECHNICAL FIELD
[0001] The present invention relates to an extremely fine shape
memory alloy wire, a composite material using the same, and a
process for producing the same.
BACKGROUND ART
[0002] It has been confirmed that products having a
vibration-controlling function and exhibiting a retarded fatigue
crack-developing rate can be obtained by embedding pre-strained
shape memory alloy wires in a matrix of a carbon fiber reinforced
plastic (CFRP), a glass fiber reinforced plastic (GFRP), aluminum
(Al), or the like. These products utilize an effect that an
elongation strain imparted to the wires beforehand in a low
temperature martensitic phase state remains after only removal of
the stress and that the wires are reverse-transformed into an
austenitic phase by heating after molding so that the wires can
restore the original shapes.
[0003] We have proposed a shape memory alloy wherein, by elevating
the reverse transformation temperature of a TiNi wire having a
diameter of 0.4 mm to the curing temperature (about 130.degree. C.)
of a matrix material such as an epoxy resin by a cold drawing work,
the TiNi wire can be easily embedded in a resin without causing any
reverse transformation and any shrinkage of the TiNi wire during
the curing even when the TiNi wire is not fixed at the both ends
(WO 02/097149 A1).
[0004] However, this technique can be applied to only composite
materials which cure at 130.degree. C. Namely, the technique cannot
be applied to heat-resistant CFRP and GFRP to be molded at about
180.degree. C., which are the most important in aviation and space
industries.
DISCLOSURE OF THE INVENTION
[0005] An object of the present invention is to provide a wire
comprising a shape memory alloy in a martensitic phase which
assumes an austenitic phase or a martensitic phase through phase
transformation temperatures, which is capable of conjuncting with a
resin at a high molding temperature of about 180.degree. C., a
composite material which comprises a resin comprising the wire, and
a process for producing the same.
[0006] As a result of extensive studies for solving the above
problems, the present inventors have found that an extremely fine
wire having a diameter of 60 .mu.m or less, which is formed by a
cold drawing work of a wire of the above shape memory alloy, is
capable of easily conjuncting with a resin even at a high molding
temperature of 180.degree. C. or higher. Based on this finding,
they have accomplished the present invention.
[0007] Namely, according to the present invention, the following
shape memory alloy wires, composite materials, and processes for
producing the composite materials are provided.
[0008] (1) A shape memory alloy wire subjected to a cold drawing
work, which comprises a shape memory alloy in a martensitic phase
which assumes an austenitic phase or a martensitic phase through
phase transformation temperatures, has a diameter of 60 .mu.m or
less, and has a reverse transformation termination temperature of
at least 250.degree. C.
(2) The shape memory alloy wire according to the above (1), which
has a cold drawing rate of at least 20%.
(3) The shape memory alloy wire according to the above (1) or (2),
wherein the shape memory alloy is a Ti--Ni alloy.
(4) A composite material which comprises a fibrous material and a
resin, wherein the fibrous material comprises the shape memory
alloy wire according to any one of the above (1) to (3).
[0009] (5) A composite material which comprises a fibrous material
and a resin, wherein the fibrous material comprises the shape
memory alloy wire according to any one of the above (1) to (3) and
at least one fiber selected from a glass fiber and a carbon
fiber.
(6) The composite material according to the above (4) or (5),
wherein the resin comprises a thermosetting resin or a
thermoplastic resin.
(7) The composite material according to the above (4) or (5),
wherein the resin comprises a precured material of a thermosetting
resin.
(8) The composite material according to the above (4) or (5),
wherein the resin comprises a thermoset product of a thermosetting
resin.
(9) The composite material according to any one of the above (4) to
(8), wherein the thermosetting resin comprises an epoxy resin.
[0010] (10) A composite material which comprises a cured resin
comprising the shape memory alloy wire according to any one of the
above (1) to (3), wherein the shape memory alloy wire is heated to
a temperature of a reverse transformation termination temperature
thereof or higher to generate a contractive force.
(11) The composite material according to the above (10), which
comprises at least one fiber selected from a glass fiber and a
carbon fiber together with the shape memory alloy wire.
(12) The composite material according to (10) or (11), wherein said
heating of the shape memory alloy wire is carried out by
application of electric current to the wire.
[0011] (13) A process for producing a composite material, which
comprises heat-curing a thermosetting resin or a precured material
thereof comprising the shape memory alloy wire according to any one
of the above (1) to (3) at a temperature which is a reverse
transformation starting temperature of the shape memory alloy wire
or higher and is lower than the reverse transformation termination
temperature; and then heating at least a part of the shape memory
alloy wire to a temperature of its reverse transformation final
temperature or higher.
(14) The process according to the above (13), wherein the
thermosetting resin or the precured material thereof comprises at
least one fiber selected from a glass fiber and a carbon fiber.
(15) The process according to the above (13) or (14), wherein said
heating of the shape memory alloy wire is carried out by
application of electric current to the wire.
BEST MODE FOR CARRYING OUT THE INVENTION
[0012] The shape memory alloy (hereinafter also simply referred to
as "alloy") for use in the present invention is an alloy in a
martensitic phase which assume an austenitic phase or a martensitic
phase through phase transformation temperatures. Such an alloy
includes a TiNi alloy. In the TiNi alloy, the Ni content thereof is
from 49 to 52% by atom (at %).
[0013] The shape memory alloy wire of the present invention is
characterized in that the alloy-wire is an extremely fine alloy
wire having a diameter of 60 .mu.m, which is formed by a cold
drawing work of a wire of the above alloy, and the reverse
transformation temperature thereof is at least 250.degree. C.
[0014] In the extremely fine alloy wire, the diameter (thickness)
is usually 60 .mu.m or less, preferably 50 .mu.m or less, and the
lower limit is not particularly limited but is usually about 5
.mu.m.
[0015] The reverse transformation starting temperature (As) of the
alloy wire is usually 130.degree. C. or higher, preferably
132.degree. C. or higher, and the upper limit is usually about
140.degree. C.
[0016] The reverse transformation termination temperature (Af) of
the alloy wire is usually 250.degree. C. or higher, preferably
260.degree. C. or higher, and the upper limit is usually about
300.degree. C.
[0017] The alloy wire of the present invention is one which has
been subjected to a cold drawing work. In this case, the cold
drawing work means that an alloy wire is drawn at a temperature of
0 to 30.degree. C., preferably 0 to 20.degree. C.
[0018] The cold drawing rate in the present specification means a
cross-sectional area reduced rate of a drawn wire obtained by cold
drawing of an alloy wire and is defined by the following equation:
R (%)=(S.sup.1-S.sup.2)/S.sup.1.times.100
[0019] R: cold drawing rate
[0020] S.sup.1: cross-sectional area of alloy wire before the cold
drawing work
[0021] S.sup.2: cross-sectional area of alloy wire after the cold
drawing work
[0022] In the alloy wire of the present invention, the cold drawing
rate is at least 20%, preferably 30% or more, and more preferably
35% or more. The upper limit is usually about 50%. The As and Af of
the alloy wire of the present invention can be controlled by the
cold drawing rate, and the As and Af are also elevated according to
increase of the cold drawing rate.
[0023] The alloy wire which has been subjected to a cold drawing
work according to the present invention retains a substantial
amount of shrinking strain (pre-strain). The shrinking strain is 2%
or more, preferably 2.5% or more, and more preferably 3.5% or more,
and the upper limit is usually about 4%. The shrinking strain can
be controlled by the drawing rate at the cold drawing of the alloy
wire.
[0024] Since the alloy wire of the present invention has been
subjected to a cold drawing work, the yield stress thereof is very
large. Therefore, it affords a resin/wire composite material having
enhanced strength and rigidity at a low temperature.
[0025] The alloy wire in a martensitic phase of the present
invention does not shrink substantially when heated at a
temperature lower than the reverse transformation starting
temperature (As) thereof but a phase change occurs when heated at a
temperature of the reverse transformation termination temperature
(Af) thereof or higher, so that the alloy wire is transformed to an
alloy wire in an austenitic phase and shrinkage occurs. The alloy
wire in an austenitic phase is again changed to a martensitic phase
by cooling the wire to a low temperature. The As' and Af' in the
alloy wire converted to the low-temperature martensitic phase is
substantially the same as the As and Af in the alloy wire before
the cold drawing work. Namely, in the alloy wire converted from the
austenitic phase to the martensitic phase, the As' is about 20 to
about 70.degree. C. and the Af' is about 30 to about 100.degree. C.
When the alloy wire in the low-temperature martensitic phase is
heated at a temperature of the Af or higher, shrinkage occurs. The
shrinkage in this case is nearly equal to that observed in a usual
alloy wire in a martensitic phase.
[0026] In the alloy wire of the present invention, the temperature
difference between the As and Af thereof is broad and the
temperature difference is 130.degree. C., preferably 150.degree.
C., and the upper limit is usually about 200.degree. C. In the
present invention, at the production of the composite material
where the alloy wire of the present invention is arranged in a
cured resin through conjunction of the alloy wire with a resin, a
temperature between the As temperature and Af temperature of the
alloy wire is adopted as a molding temperature (a temperature for
conjunction). In the present invention, particularly, it is
advantage to adopt a temperature which is 30 to 100.degree. C.,
preferably 40 to 80.degree. C., and more preferably 50 to
60.degree. C., higher than the As temperature. Such a molding
temperature is a temperature lower than the Af temperature of the
alloy wire and the alloy wire is in an intermediate state between a
martensitic phase and an austenitic phase, and hence the shrinking
rate thereof is low. Therefore, a deformation ratio of the
composite obtained by conjunction of the alloy wire with a resin is
very small and thus does not particularly hinder usefulness of the
composite.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIGS. 1 and 2 are drawings showing measured results of a
shrinking strain change involved in reverse transformation of a
Ti-50 at % Ni wire with a cold drawing rate of 35%.
[0028] FIG. 1: wire having a diameter of 50 .mu.m
[0029] FIG. 2: wire having a diameter of 40 .mu.m
[0030] FIG. 3 is a drawing showing measured results of a shrinking
strain change involved in reverse transformation of a Ti-50 at % Ni
wire (diameter of 50 .mu.m) which is subjected to thermal treatment
at 130.degree. C. for 2 hours and has a cold drawing rate of
35%.
[0031] FIG. 4 is a drawing showing measured results of a shrinking
strain change involved in reverse transformation of a Ti-50 at % Ni
wire (diameter of 50 .mu.m) which is subjected to thermal treatment
at 180.degree. C. for 2 hours and has a cold drawing rate of
35%.
[0032] FIGS. 5 and 6 are experimental results of a
crack-suppressing effect detected when the alloy wire arranged in a
composite material is heated by application of electric
current.
[0033] FIG. 5 shows a shrinking strain change of the sample surface
when an electric current is applied, and FIG. 6 shows a temperature
change of the sample surface when an electric current is
applied.
[0034] Specific meanings of the symbols in FIGS. 1 to 4 are as
follows: [0035] As: a reverse transformation starting temperature
from a martensitic phase to an austenitic phase formed when an
alloy wire is heated in the direction of the arrow a. [0036] Af: a
reverse transformation termination temperature from a martensitic
phase to an austenitic phase formed when an alloy wire is heated in
the direction of the arrow a. [0037] Ms: a reverse transformation
starting temperature from an austenitic phase to a martensitic
phase formed when an alloy wire is cooled in the direction of the
arrow a. [0038] Mf: a reverse transformation termination
temperature from an austenitic phase to a martensitic phase formed
when an alloy wire is cooled in the direction of the arrow a.
[0039] As': a reverse transformation starting temperature from a
martensitic phase to an austenitic phase formed when an alloy wire
is heated in the direction of the arrow b. [0040] Af': a reverse
transformation termination temperature from a martensitic phase to
an austenitic phase formed when an alloy wire is heated in the
direction of the arrow b.
[0041] With regard to the alloy wire having a diameter of 50 .mu.m,
in the case of the first heating-cooling cycle shown by the arrow
a, the shrinking strain is 3.5%, As is 133.degree. C., and Af is
267.degree. C. (FIG. 1).
[0042] On the other hand, with regard to the alloy wire having a
diameter of 400 .mu.m, in the case of the first heating-cooling
cycle shown by the arrow a, the shrinking strain is 2.3%, As is
130.degree. C., and Af is 210.degree. C. (FIG. 2).
[0043] From the above results, in the case of the extremely fine
alloy wire (FIG. 1), at the same cold drawing rate of 35%, it is
revealed that the shrinking strain increases to 3.5% and the
reverse transformation temperature range becomes very broad and
shifts to a high-temperature side.
[0044] On the other hand, in the second heating shown by the arrow
b, in the case of the extremely fine alloy wire (FIG. 1), As'
becomes 29.degree. C., Af' becomes 67.degree. C., and thus the
reverse transformation temperature range returned to the same level
as in the case of a usual thermally treated alloy wire.
[0045] Furthermore, a change of the shrinking strain involved in
reverse transformation was investigated by measuring thermal
expansion on the extremely fine alloy wires after thermal treatment
at 130.degree. C. and 180.degree. C. each for 2 hours. The results
are shown in FIGS. 3 and 4, respectively. In the wire thermally
treated at 130.degree. C. for 2 hours, it is revealed that the
shrinking strain becomes about 3.0% and the reverse transformation
temperature range becomes in the range of 160 to 264.degree. C.
(FIG. 3).
[0046] On the other hand, in the wire thermally treated at
180.degree. C. for 2 hours, it is revealed that the shrinking
strain becomes about 2.5% and the reverse transformation
temperature range becomes in the range of 197 to 271.degree. C.
(FIG. 4). From the results, in the alloy wire/resin composite
material formed at 180.degree. C., a shrinking strain of 2.5% still
remains in the extremely fine wire. Thereby, it is considered that
a restoring stress of 250 MPa or more is obtained.
[0047] Various alloy wire/resin composite materials can be obtained
by the use of the alloy wire of the present invention.
[0048] The resin in this case includes a thermosetting resin and a
thermoplastic resin. Examples of the thermosetting resin include an
epoxy resin, a phenol resin, a polyimide resin, a vinyl ester
resin, an unsaturated polyester resin, a polyurethane resin, a
precured material of a thermosetting resin (thermosetting
prepolymers), and the like. Examples of the thermoplastic resin
include a polyolefin resin, a fluorine-containing resin, a
polyamide resin, a thermoplastic polyimide resin, a polyester
resin, a polycarbonate resin, and the like.
[0049] The alloy wire for use in the composite material of the
present invention can be used in combination with a conventionally
known fibrous material, e.g., a glass fiber or a carbon fiber.
[0050] The composite material of the present invention can be a
thermosetting material (pre-impregnation material) comprising the
alloy wire and a thermosetting resin or a precured material thereof
(prepolymer). The composite material can be any of various shapes
such as sheet, thread, columnar, rope, and block shapes.
[0051] By heating the thermosetting composite material at a
temperature lower than the Af of the alloy wire incorporated
therein, usually a temperature of 185.degree. C. or lower to cure
the resin, the material can be converted into a composite material
comprising the alloy wire in the cured resin. In this case, the
heating temperature is a temperature lower than the Af of the alloy
wire, so that a large shrinkage of the alloy wire does not occur.
Therefore, when the alloy wire of the present invention is used, it
is actually not necessary to use both ends fixing apparatus which
has been employed for retaining pre-strain of the wire in the cases
of conventional alloy wires.
[0052] The composite material comprising the alloy wire of the
present invention in the cured resin can express a shrinking force
through phase change from a martensitic phase to an austenitic
phase by heating at least a part of the alloy wire to a high
temperature of the Af thereof or higher.
[0053] With regard to the product thus obtained, the alloy in an
austenitic phase can be again converted into the alloy in a
martensitic phase by further cooling the product to a low
temperature. The product containing the alloy wire in a martensitic
phase can be used in various applications utilizing characteristics
of the alloy wire.
[0054] The composite material of the present invention can be a
material formed by embedding the alloy wire in a thermosetting
resin and heating it at a temperature lower than the Af to cure the
resin. In this case, the resin can be a liquid one or a powdery
one. Moreover, the resin can be one containing a fibrous material
such as a glass fiber or a carbon fiber.
[0055] The composite material of the present invention can be a
material formed by thermally melting a thermoplastic resin which
melts at a temperature lower than the Af of the alloy wire and
arranging the alloy wire therein, followed by cooling and
solidification.
[0056] In the alloy wire in a martensitic phase which has undergone
cold drawing and is incorporated in the composite material of the
present invention, the As and Af thereof is not returned to normal
ones unless the alloy is subjected to reverse transformation to an
austenitic phase. Therefore, in the composite material, in order to
obtain a shape-restoring power, it is necessary to heat the alloy
wire in the composite material once to a temperature of the Af
thereof or higher.
[0057] In the present invention, heating of the alloy wire
incorporated in the above composite material can be advantageously
carried out by passing an electric current through part or all of
the alloy wire for a short period and then shutting down the
application of electric current. In this case, the period of the
application of electric current is from 1 to 60 seconds, preferably
from 1 to about 20 seconds. Even when the alloy wire is heated to a
temperature of the Af or higher by passing an electric current for
such a short period, influence of the heat on the resin around the
alloy wire is small. This is because the temperature of the alloy
wire in the vicinity of the surface thereof is not immediately
elevated since the reverse transformation is an endothermic
reaction and the application of electric current is stopped while
the surface temperature of the alloy wire is low.
[0058] By heating the alloy wire incorporated in the composite
material to a temperature of the Af or higher and cooling it to a
low temperature, the alloy wire is converted into a low temperature
martensitic phase alloy wire, whose reverse transformation
temperature returns to the normal one, and a shape-restoring power
can be obtained by heating with a low current.
EXAMPLE
[0059] The present invention is described below in detail based on
Example.
Example 1
[0060] A Ti-50 at % Ni wire (diameter: 50 .mu.m) having a cold
drawing rate of 35% manufactured by a drawing work at a temperature
of 15.degree. C. was kept at 180.degree. C. for 2 hours and
embedded in a carbon fiber reinforced epoxy resin (CFRE) to prepare
a composite material having damage-suppressing and
vibration-controlling functions.
[0061] Since the molding conditions for CFRE in this case were at
180.degree. C. for 2 hours, the cold-drawn alloy wire was kept at
180.degree. C. for 2 hours and then, with regard to the resulting
wire, the shrinking strain and change of the reverse transformation
temperature were measured.
[0062] FIG. 4 shows the results. From FIG. 4, it was revealed that
the cold-drawn wire retained a shrinking strain of 2.5% even when
thermally treated at 180.degree. C. for 2 hours. According to this
shrinking strain of 2.5%, a shape-restoring stress of 250 MPa or
more can be obtained.
[0063] FIGS. 5 and 6 shows experimental results on a
crack-suppressing effect detected when the alloy wire in the
composite material manufactured is heated by application of
electric current. FIG. 5 shows a change of shrinking strain of the
sample surface when an electric current is applied, and FIG. 6
shows a temperature change of the sample surface when an electric
current is applied.
INDUSTRIAL APPLICABILITY
[0064] According to the present invention, there is provided a
shape memory alloy wire advantageously applied to a resin having a
high molding temperature of about 180.degree. C., particularly a
glass fiber reinforced resin and a carbon fiber reinforced resin.
When the alloy wire is used, an alloy wire/resin composite material
can be easily obtained without using a wire-both ends fixing
apparatus for retaining pre-strain.
[0065] Since the alloy wire of the present invention has a diameter
which is so extremely fine as 60 .mu.m or less, it can be handled
in a similar manner to conventional carbon fibers and glass fibers.
Therefore, according to the present invention, a prepreg composite
material wherein the alloy wire is incorporated in a thermosetting
resin can be obtained.
* * * * *