Stress Induced Colour Changing Polymers


I need some advice.

I have been told that there are polymers in existance that change colour when put under stress. I cant find any reference to them on the net, as all search results tend to return temperature or UV sensitive colour changing platsics.

Does anyone know where i might find some more information about such a material, a product that uses them, or a company that manufactures it?

Thanks for your help