Integrated Buckling Analysis and Manufacturable Design of Variable Stiffness Composite Panels for High-Performance Structures

Abstract

Variable stiffness composite panels, including tow-steered laminates and functionally graded materials (FGMs), offer significant advantages over traditional uniform plates by enabling localized load path redistribution and extreme environment multi-functionality. Integrating curvilinear stiffeners into these panels further enhances structural stability against buckling with minimal weight penalties. These highly tailored structural components are vital for advanced aerospace applications like wingboxes and fuselages. However, the design and analysis of these complex high-performance structures remain computationally challenging, particularly when ensuring the manufacturability of the final design. To address these challenges, this research first presents a mesh-independent buckling analysis solver for curvilinearly stiffened FGM plates utilizing the Ritz method with orthogonal Jacobi polynomials. This approach eliminates the need for computationally expensive re-meshing during shape and layout optimization studies. Building on this, the study introduces a comprehensive integrated optimization framework for curvilinearly stiffened tow-steered panels. This framework simultaneously designs tow paths and stiffener layouts while rigorously enforcing physical manufacturing constraints, including fiber curvature, and gaps, and overlaps. Finally, two distinct methodologies for tow-steered laminate optimization are evaluated and compared: (1) direct fiber angle parameterization using Simulia/Isight and Abaqus/Standard, which facilitates the explicit enforcement of ply-level strength and manufacturing limits, and (2) a bi-level lamination parameter approach with analytical gradients, using an open source parallel finite-element code Toolkit for the Analysis of Composite Structures (TACS) and an open-source high-performance computing platform for multidisciplinary optimization OpenMDAO, that convexifies the design space for highly efficient computational evaluations. Furthermore, the bi-level framework is extended to perform simultaneous structural topology and variable angle tow-path optimization, concurrently generating the optimal macroscopic material layout and the localized variable stiffness distribution. Ultimately, this work provides a scalable, robust methodology for designing lightweight, easy to manufacture, and highly tailored aerospace composite structures.