Twisting-Induced Instabilities in Double-Helix Chiral Rods

Elastic rods exhibit complex, nonlinear mechanical behaviors, especially under combined axial tension and twisting. Our study focuses on the nonlinear response of double-helix chiral rods, structures that combine a cylindrical core with helically coiled reinforcements. Through experiments, analytical modeling, and finite element simulations, we reveal that twisting induces mechanical instabilities, leading to complex deformation patterns. These instabilities are heavily influenced by the interplay between the core and the helical reinforcements, with the resulting deformations showing strong sensitivity to geometric and material characteristics. The findings enhance our understanding of chiral rods, with potential applications in soft robotics and tunable optical devices.