Sandwich Constructions 4, pp. 160-171, 1998

EFFECTS OF IN-PLANE STIFFNESS ON THE WRINKLING LOAD OF SANDWICH CONSTRUCTIONS

W.K. Vonach, F.G. Rammerstofer

Institute of Lightweight Structures and Aerospace Engineering,
TU Wien, Vienna, Austria


Abstract - A refined analytical calculation is presented for wrinkling of thick sandwich constructions with isotropic facelayers and orthotropic cores. This approach leads to a single explicit equation for the critical wrinkling load in an asymptotic sense, taking into account in-plane deformations of the core. The results have been veryfied by a numerical model [1] and show that, when dealing with highly orthotropic cores (eg honeycomb) the wrinkling loads and wrinkling patterns can strongly depend on the in-plane stiffness of the core. Therefore, the classical wrinkling formula [2,3] can lead to significant errors when used in connection with highly orthotropic cores. This way it can be shown that the in-plane stiffness of the core (which is relatively small in the case of honeycombs) has a significant influence and must not be disregarded in wrinkling analysis. For extremely small values of the in-plane stiffness, the wrinkling load decreases to the load given by the Winkler foundation model even for very thick cores.

[1] Starlinger A., Development of Efficient Finite Shell Elements for the Analysis of Sandwich Structures under Large Deformations and Global as well as Local Instabilities, VDI Fortschrittberichte Nr 18/93, VDI Verlag, Düsseldorf, 1991.
[2] Plantema F.J., Sandwich Construction, John Wiley & Sons, New York, 1966.
[3] Wiedemann J., Leichtbau, Springer Verlag, Berlin, 1986.


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