Stiffness tailoring of elliptical composite cylinders for axial buckling performance

Automated fiber placement (AFP) machines have made it possible to tailor the material stiffness properties in a laminated composite structure by fiber steering. The so-called variable stiffness (VS) laminate can be designed to improve the structural performance of a composite component. Herein, using a metamodeling based design optimization (MBDO) method, elliptical composite cylinders with VS laminate are designed and optimized for maximum axial buckling capacity. The effect of cross-sectional aspect ratio of the elliptical cylinders on the potential improvement of the buckling capacity is also investigated. As the baseline for comparison, for each cross-sectional aspect ratio, the buckling capacity of elliptical cylinders with quasi-isotropic (QI) and optimum constant stiffness (CS) laminates are also calculated. It is found that the buckling capacity of an elliptical composite cylinder can be improved by fiber steering up to 118% compared with its best CS counterpart.