Material that can be bent repetitively without fatique?

[nomisme]

I am looking for a material that I can bend easily into different desired shape frequently without breaking or losing strength. The material can either be elastic or not elastic. I know sheet spring can do but if I bend it like 70 to 80 degrees will it permanently deformed or become fatique?

Will you recommend a few material composite that allow me to do that? or any examples of this usage?

thanks

 

[MartK]

Some thoughts:
If it doesn't need to stay by itself in the shape that it's forced into, perhaps a amorphous polymer that is in it's rubbery plateau region in the operating temperature would be suitable. For an example (at the room temperature) cross-poly(butadiene-stat-styrene) that is used in rubber bands. If it needs to be a composite material, maybe a particle reinforced polymer matrix where the matrix material is in that same rubbery plateau state. Though there might be problems with adhesion between the particles and the matrix if the composite is being bent a lot.
The first thing that came into my mind when reading your post was the silicone cupcake moulds that can be turned inside out. Now I think I need to visit a bakery...

 

[K_Mitchell]

Would this be useful?

http://en.wikipedia.org/wiki/Nickel_titanium

 

[Doug Huffman]

Silly putty

 

[Blackberg]

Socks

 

[NascentOxygen]

I seem to recall that lead metal (Pb) self-anneals at room temperature. So given time it heals after being bent, then can be bent again, and this way never exhibits fatigue.