L-Shaped Stringer Tailoring to Enhance Axial Buckling of FGM Elliptical Cylindrical Shells

A review of the literature indicates that buckling of longitudinal stiffeners is one of the primary challenges faced by stiffened cylindrical shells under axial compressive loads. In this study, conventional longitudinal stiffeners with rectangular cross-sections were replaced by innovative L-shaped stiffeners, aiming to enhance the structural stability of stiffened composite cylindrical shells. To demonstrate this concept, a functionally graded material (FGM) shell, an advanced form of composite with continuously varying properties, was modeled using the semi-analytical finite strip method in the FORTRAN environment. The results from the developed model were compared with those obtained from the finite element method to assess the model’s accuracy. Through a comprehensive parametric study, the effects of shell geometry, L-shaped stiffener configuration, and the FGM power index on the axial buckling performance of the stiffened shell were investigated. The findings revealed that, for certain combinations of the investigated parameters, the axial buckling load of shells with L-shaped stiffeners can be approximately 40-70% higher than that of shells with conventional rectangular stiffeners, despite using the same material and stiffener cross-sectional area. This demonstrates that adopting alternative stiffener geometries provides a practical and effective strategy for enhancing the buckling resistance of composite structural shells in construction engineering applications.