Sandwich Constructions 4, pp. 160-171, 1998
W.K. Vonach, F.G. Rammerstofer
Institute of Lightweight Structures and Aerospace
TU Wien, Vienna, Austria
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
The results have been veryfied by a numerical model  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
 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.
 Plantema F.J., Sandwich Construction, John Wiley & Sons, New York, 1966.
 Wiedemann J., Leichtbau, Springer Verlag, Berlin, 1986.