Capturing the helical to spiral transitions in thin ribbons of nematic   elastomers
  We provide a quantitative description of the helicoid--to--spiral transition in thin ribbons of nematic elastomers using an elementary calculation based on a Koiter-type plate with incompatible reference configuration. Our calculation confirms that such transition is ruled by the competition between stretching energy and bending energy. 
Giuseppe Tomassetti, Valerio Varano
cond-mat.soft cond-mat.mtrl-sci