Buckling Load Maximization of Curvilinearly Stiffened Tow-Steered Laminates

Abstract

Under certain loading conditions, curvilinearly stiffened panels are seen to have better structural performance while being lighter in mass when compared to panels with straight stiffeners. A curvilinearly stiffened tow-steered composite laminate could be manufactured by fastening or bonding metallic curvilinear stiffeners to the composite panel. In this paper, such panels are computationally evaluated for their benefit in improving the panel buckling load. Initially, a parallel processing-based optimization framework to design tow-steered composite laminates with metallic curvilinear stiffeners is presented, where the objective is to maximize the buckling load with only a structural mass constraint and no stress constraint. The results show that the curvilinear stiffeners and curvilinear fiber paths in the composite laminated skin can lead to more than a 75% increase in the panel buckling load as compared to the use of equidistant straight stiffeners and straight fibers. Subsequently, a multiobjective optimization is conducted with the objectives to maximize the buckling load while minimizing the mass of the panels. It is seen that the improvement in the buckling load, by using curvilinear stiffeners and curvilinear fibers over equidistant straight stiffeners and straight fibers, depends upon the prescribed structural mass constraint.