Inspired by wrinkled surfaces such as earthworms in nature, the construction of wrinkled patterns on fiber surfaces provides a novel idea for high-performance functional fibers and fabrics. Recent theoretical and experimental studies focused on wrinkling patterns on compliant substrates, however, most industrial fibers are rigid. Based on previous experiments of wrinkling on rigid PET fiber from gradient shell, herein the wrinkling formation and evolution based on a novel gradient shell-rigid core (GSRC) system is studied via the nonlinear finite element method (FEM). The results demonstrate that wrinkling is formed due to the stress-induced mutagenesis generated from the gradient shell modulus. The higher gradient factor of shell modulus leads to smaller critical mismatched strain, i.e., easier formation of surface wrinkling. Then a post-buckling phenomenon in this system is studied, involving a successive bifurcation: smooth-wrinkle-ridge transition. Meanwhile, the evolution of topological patterns is significantly influenced by the shell-induced curvature. This study not only benefits the understanding of wrinkling gradient shell on rigid cylindrical substrate but also provides useful guilds for the fabrication of surface patterned functional fiber or fabrics.

In nature, many mysterious creatures are capable of defense and courtship via mimicry or color change. However, developing smart materials with integration of conformation and color/transparency change is an intriguing...