Shape change structure

Abstract

An expandable structure comprising: a first shape memory (SM) portion which is in a strain-induced state; and a second portion which resists expansion of said structure due to said first portion, over a plurality of different expansion states of said first portion. Optionally, wherein said SM portion resists contraction of said structure due to forces applied by said second portion. Optionally or alternatively, said strain induced state is characterized by a SM portion expanding force decreasing as a function of strain of said SM portion, so as to have a difference of at least 10% in force between two strain states said structure is usable at.

What is claimed is: 
     
         1 . A tubular expandable structure comprising:
 a plurality of rigid struts orientated axially along the structure and each having an initial length;   a plurality of flexible members;   wherein each rigid strut is coupled to another two rigid struts;   wherein coupling one rigid strut to another is by at least two flexibly bent members, such that rigid struts coupled by flexibly bent members form at least one circumferential segment of the tubular structure;   wherein upon a radial expanding force said flexible members unbend to expand a diameter of each said circumferential segment;   wherein upon a radial contracting force said flexible members bend to contract a diameter of each said circumferential segment; and   wherein said rigid struts substantially maintain said initial lengths thereof.