Related Experiment Video
Updated: Oct 10, 2025

Cutting Procedures, Tensile Testing, and Ageing of Flexible Unidirectional Composite Laminates
Published on: April 27, 2019
Writhing and hockling instabilities in twisted elastic fibers
Adam Fortais1, Elsie Loukiantchenko1, Kari Dalnoki-Veress2,3
1Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1, Canada.
Abstract:
The buckling and twisting of slender, elastic fibers is a deep and well-studied field. A slender elastic rod that is twisted with respect to a fixed end will spontaneously form a loop, or hockle, to relieve the torsional stress that builds. Further twisting results in the formation of plectonemes-a helical excursion in the fiber that extends with additional twisting. Here we use an idealized, micron-scale experiment to investigate the energy stored, and subsequently released, by hockles and plectonemes as they are pulled apart, in analogy with force spectroscopy studies of DNA and protein folding. Hysteresis loops in the snapping and unsnapping inform the stored energy in the twisted fiber structures.
Related Concept Videos
Members Made of Elastoplastic Material
As the bending moment...
Angle of Twist - Elastic Range
Residual Stresses in Circular Shafts
Elastic Strain Energy for Shearing Stresses
Residual Stresses in Bending
Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity

