Residual twist in a double-layer strand and its correlation with bending fatigue

Abstract

We propose a method to characterize an undeformed double-layer strand with residual stress by considering the deviation from the self-equilibrium configuration where torque is balanced without any external forces. We first derive the residual twist defined as the deviation of internal twisting moment in the strand from the self-equilibrium configuration. The residual twist gives a measure of the effective torsional rigidity of the strand, determined by the geometrical, material, and mechanical parameters from the microstructural viewpoint. Then, we correlate the residual twist with the fatigue life of (3+8)-glass strands embedded in a rubber matrix under cyclic bending. We show that the residual twist correlates with the number of cycles to failure for specific (3+8)-glass strands having the identical twist direction.

A minimal model of elastic instabilities in biological filament bundles

“…Such models range from isolated filaments [7][8][9], to exact geometrical models [10][11][12][13] and multi-scale continuum approaches [14][15][16][17]. Their applications are diverse, including actin filaments [18], microtubules [19,20], collagen bundles [21], optic nerves [22,23], muscle fibres [14], fabric composites [24], carbon fibres [25] and mechanical ropes [26].…”