Design optimization of stiffened composite panels with buckling and damage tolerance constraints

Abstract

The design of stiffened, composite wing panels must satisfy a range of requirements related to performance, economy and safety. In particular, the design must be damage tolerant to satisfy a number of different performance requirements for various states of damage. To obtain an optimum configuration that satisfies these requirements simultaneously, optimization code PANOPT was extended with a multi-model capability. First, the effect of damage tolerance constraints on postbuckled optimum design was established for blade-I-and hat-stiffened panels with stiffener flanges embedded in the skin. The "classical" order of efficiency for optimized panels designed for buckling alone (hats, I's, blades) was no longer valid, as the masses of the three panel types were approximately equal. To obtain realistic damage models, the failure mechanismms and damage tolerance of the panel concept with embedded stiffeners were determined in an experimental programme. Finally, the multi-model capability of PANOPT was demonstrated with the simultaneous optimization of an undamaged panel carrying design ultimate load, the same panel with a separated stiffener carrying design limit load, and the panel with a cut stiffener carrying seventy percent of the design limit load. An optimum design was found with an additional mass of only five percent compared to a panel optimized for the undamged case alone.

Design optimization of stiffened composite panels for damage resistance

“…A previous study 3 carried out at NLR was aimed at the design of damage tolerant stiffened, composite panels by numerical optimization, for which a multimodel capability was developed, and incorporated in computer code PANOPT. This capability allows the design optimization process to consider several configurations simultaneously, configurations which represent the panel in an undamaged state, as well as in several representative damage states, each for different strength criteria, depending on the severity of the damage.…”

Impact identification of stiffened composite panels: I. System development

“…Aircraft structural design, with metals or composites [17], often incorporates stiffened panels, which consist of skins reinforced with discrete stiffeners. It is important to study impacts near stiffeners, as debonding of the skin and stiffener may occur, leading to catastrophic loss in structural performance [18].…”

Pre-Programmed Failure Behavior Using Biology-Inspired Structures

“…47 Other research has sought component shapes or structural configurations that optimize failure response with elastoplastic materials 44 , or in the presence of nonlinear geometric behavior. 66 Composite panels have been extensively studied for optimization of stiffener dimensions and spacing for elastic performance 22 , resistance to buckling 63 , and ability to withstand impact damage. 64 Lightweight truss core panels have been subjected to optimization of truss element and facesheet dimensions.…”