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 μm or less, and has a reverse transformation termination temperature of at least 250° 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° C., such as a glass fiber reinforced resin or a carbon fire reinforced resin, without fixing of both wire ends.

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 μm or less, and has a reverse transformation termination temperature of at least 250° 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.