Aeronautical composite stiffened structures have the capability to carry loadsdeep into postbuckling, yet they are typically designed to operate below thebuckling load to avoid potential issues with durability and structural integrity. Largeout-of-plane postbuckling deformation of the skin can result in the opening of theskin-stringer interfaces, especially in the presence of defects, such as impactdamage. To ensure that skin-stringer separation does not propagate in an unstablemode that can cause a complete collapse of the structure, a deeper understanding ofthe interaction between the postbuckling deformation and the development ofdamage is required. The present study represents a first step towards a methodologybased on analysis and experiments to assess and improve the strength, life, anddamage tolerance of stiffened composite structures subjected to postbucklingdeformations.Two regions were identified in a four-stringer panel in which skin-stringerseparation can occur, namely the region of maximum deflection and the region ofmaximum twisting. Both regions have been studied using a finite element model ofa representative single-stringer specimen. For the region of maximum deflection, aseven-point bending configuration was used, in which five supports and twoloading points induce buckling waves to the specimen. The region of maximumtwisting was studied using an edge crack torsion configuration, with two supportsand two loading points. These two configurations were studied by changing thepositions of the supports and the loading points. An optimization procedure wascarried out to minimize the error between the out-of-plane deformation of therepresentative single-stringer specimen and the corresponding region of the fourstringerpanel.
展开▼
