A multilevel framework for optimization of an aircraft wing incorporating postbuckling effects

Abstract

The optimization of aerospace structures is a very complex problem, owing to the hundreds of design variables a multidisciplinary optimization may contain, so that multilevel optimization is required. This paper presents recent developments to the optimization software VICONOPT MLO, a multilevel optimization interface between the analysis and design software packages VICONOPT and MSC/NASTRAN. The software developed, VICONOPT MLOP (Multilevel Optimization with Postbuckling) incorporates postbuckling behaviour, allowing individual panels to buckle before the design load is reached, while carrying load at a reduced stiffness. By combining two iterative cycles the first of which (known as the analysis cycle) calculates these reduced postbuckling stiffnesses at an individual panel level in order to converge on an appropriate load distribution at a whole structure or system level and the second of which (known as the design cycle) optimizes individual panels based on this load redistribution to converge on an optimized mass for the whole structure. The paper provides a detailed overview of the functionality of the software and a case study is conducted into the optimization of a composite aircraft wing. The results of the case study show substantial mass savings, proving the software's capabilities when dealing with such problems. The time taken for this multilevel optimization also demonstrates the efficiency of the software.

A novel parallel method for layup optimization of composite structures with ply drop-offs

“…For the first stage optimization, the multilevel optimization framework VICONOPT MLO [24,45,46] is used to conduct mass minimization. During the iterative optimization process, FEA is utilized for the static analysis of the whole structure to obtain the load distributions at the start of each design cycle, using stiffness matrices generated based on lamination parameters and laminate thicknesses.…”

“…In the first stage, the highly efficient software VICONOPT [41,42] based on exact strip analysis and the Wittrick-Williams algorithm [43,44] was used to optimize the lamination parameters and laminate thicknesses with a logic-based layerwise branch and bound method (LBB) employed in the second stage to optimize the layup based on these optimized lamination parameters. This two-stage method was then extended to blending optimization [24], where the lamination parameters and laminate thicknesses of component panels were optimized using the multilevel optimization framework VICONOPT MLO [45,46] in the first stage, and blended stacking sequences were then obtained based on a logical search using the dummy layerwise branch and bound method (DLBB) in the second stage.…”

Buckling optimization of blended composite structures using lamination parameters

“…VICONOPT MLO [42,43] is a software package providing a multilevel optimization framework based on the optimization features of VICONOPT for each component panel and FEA for the whole structure. A static analysis of the whole structure (system) is first performed by FEA.…”