Bilevel Optimization and Postbuckling of Highly Strained Composite Stiffened Panels

The paper presents a bilevel strategy for the efficient optimum design of composite stiffened panels using VICONOPT, a fast-running optimization package based on linear eigenvalue buckling theory, and embracing practical composite design rules. Panel level optimization finds a minimum weight cross-sectional geometry based on a substitution of equivalent ortbotropic plates for laminated plates. Optimization at the laminate level finds stacking sequences satisfying laminate design rules. VICONOPT models are validated with ABAQUS finite element models, and with experimental compressive testing of two blade-stiffened panels. The buckling and postbuckling behavior of the two panels, with initial buckling in the stiffeners and skin, respectively, is investigated in a high load and high strain range. The bilevel strategy is evaluated by the design of a relatively short Z stiffened panel which has been manufactured and tested, and also by design of a long wing cover panel with combined loads. The weight saving from the wing cover panel is 13% compared with an existing datum design. This demonstrated that the strategy is efficient, reliable, and extendable into the long panel range.

[1]  Fred W. Williams,et al.  Optimum design using VICONOPT, a buckling and strength constraint program for prismatic assemblies of anisotropic plates , 1992 .

[2]  Michael Chun-Yung Niu,et al.  Composite airframe structures : practical design information and data , 1993 .

[3]  David Kennedy,et al.  Discrete optimum design of composite plates including longitudinal voids , 2004 .

[4]  David Kennedy,et al.  Analysis and testing of a postbuckled stiffened panel , 2002 .

[5]  Richard Butler,et al.  User manual for VICONOPT: An exact analysis and optimum design program covering the buckling and vibration of prismatic assemblies of flat in-plane loaded, anisotropic plates, with approximations for discrete supports, and transverse stiffeners , 1990 .

[6]  Raphael T. Haftka,et al.  Design of a blade-stiffened composite panel with a hole , 1991 .

[7]  Christos Kassapoglou,et al.  Simultaneous cost and weight minimization of composite-stiffened panels under compression and shear , 1997 .

[8]  Layne T. Watson,et al.  Improved Genetic Algorithm for the Design of Stiffened Composite Panels , 1994 .

[9]  László P. Kollár,et al.  Buckling of Unidirectionally Loaded Composite Plates with One Free and One Rotationally Restrained Unloaded Edge , 2002 .

[10]  Satchi Venkataraman,et al.  Optimization of Composite Panels - A Review , 1999 .

[11]  Paul M. Weaver,et al.  Designing composite structures: Lay-up selection , 2002 .

[12]  David Kennedy,et al.  Postbuckling of Stiffened Panels Using Strut, Strip, and Finite Element Methods , 2003 .

[13]  Chiara Bisagni,et al.  Post-buckling optimisation of composite stiffened panels using neural networks , 2002 .