Buckling Robustness to Imperfections in Tow-Steered Compared With Quasi-Isotropic Composite Cylinders

The study investigates the imperfection sensitivity of two types of composite cylindrical shells under axial compression - a traditional quasi-isotropic laminate and a novel rapid tow-sheared variable-stiffness laminate. Through an experimental buckling investigation, the research demonstrates that the rapid tow-sheared cylinder exhibited higher buckling load and greater tolerance to geometric imperfections compared to the quasi-isotropic shell. A comparative reliability analysis, employing statistical knockdown factors, quantified the reduction in strength due to imperfections for each design. The imperfection characteristics of the shells were analyzed and correlated with their buckling performance. Finite element (FE) simulations, incorporating the measured imperfection fields, closely replicated the experimental results and provided additional insight into the buckling behavior. The findings indicate that fiber-steered variable-stiffness designs can significantly mitigate the imperfection sensitivity of composite shells, thereby improving their buckling performance and reliability compared to conventional quasi-isotropic constructions.