Untersuchung zur Schaelfestigkeit von Stringer-Haut-Verbindungen aus Faserverbundwerkstoffen bei grossen Deformationen Abschlussbericht

The present study investigated the buckling and postbuckling behavior of stringer reinforced fiber composite plates in theory and experiments. Particular attention was paid to the analysis of stringer peel-off mechanisms which may occur as a result of buckled skin fields. At the same time production defects were simulated and their effects as well as impact damage were studied. Calculations of the postbuckling condition used a geometrically nonlinear mixed finite element scheme (FiPPS) based on a generalized working principle in accordance with Hellinger-Reissner. Quantitative statements became possible with the introduction of a failure model on the basis of critical energy release rates. The critical values determined by means of simple specimen tests are independent of local stiffness discontinuities; their validity range rather covers all adhesive bonded joints produced from the material T300/913C using the one-shot process. As a result it was possible to numerically acquire a variety of variations with respect to the influence of local delaminations under the stringer foot as well as different laminate lay-ups of the stringer foot. The bottom line is that initial failure of the stringer-skin bonded joints occurs at a point quite far into the postbuckling range. Therefore, with proper stringer design, there is an initial possibility of utilizing the postbuckling range beyond the safe operating load of an aircraft for the static case. (orig./RHM)SIGLEAvailable from TIB Hannover: RO 5657(93-02)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman