Post-buckling analysis of square film under in-plane torsion: experiment and simulation comparisons

Thin-film structures are widely used in industry due to their advantages in lightweight, flexibility and deployability. This paper investigates the wrinkling deformation pattern of square film subjected to in-plane torsion through the post-buckling theory of shell, with the geometric nonlinear behavior derived by energy principle and analyzed with finite element method. An equal-sized experimental verification platform is designed and fabricated, and the wrinkling surface of polyimide film driven by rotary motor is reconstructed by 3D-digital image correlation measurement and verified with finite element simulation comparisons. Wrinkling region within the film expands continuously as the torsion proceeds, accompanied by multiple wrinkling configuration transitions throughout the complete evolutionary process. Due to the non-axial symmetry between structure and loading, significant discrepancies arise in amplitude, span and wavelength between different stripes, effects of thickness, torsion radius and pre-stretch on wrinkling pattern configuration are further discussed. This study can provide valuable references for understanding the wrinkling mechanism of hard film under complex torsion loading.