Optimization of Composite Structures to Delay Mode Jump Instabilities

Andrea A. Faggiani, Brian G. Falzon, Dominik Brunner

Research output: Contribution to journalArticlepeer-review


Numerous studies have shown that postbuckling stiffened panels may undergo abrupt changes in buckled mode
shape when loaded in uniaxial compression. This phenomenon is often referred to as a mode jump or secondary
instability. The resulting sudden release of stored energy may initiate damage in vulnerable regions within a
structure, for example, at the skin-stiffener interface of a stiffened composite panel. Current design practice is to
remove a mode jump by increasing the skin thickness of the postbuckling region. A layup optimization methodology,
based on a genetic algorithm, is presented, which delays the onset of secondary instabilities in a composite structure
while maintaining a constant weight and subject to a number of design constraints. A finite element model was
developed of a stiffened panel’s skin bay, which exhibited secondary instabilities. An automated numerical routine
extracted information directly from the finite element displacement results to detect the onset of initial buckling and
secondary instabilities. This routine was linked to the genetic algorithm to find a revised layup for the skin bay, within
appropriate design constraints, to delay the onset of secondary instabilities. The layup optimization methodology,
resulted in a panel that had a higher buckling load, prebuckling stiffness, and secondary instability load than the
baseline design.
Original languageEnglish
Pages (from-to)703-711
Number of pages9
JournalAIAA Journal
Issue number4
Publication statusPublished - Apr 2011


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