A failure criterion for honeycomb structures considering the onset of instability under out-of-plane loads

A failure criterion for predicting the damage of honeycomb structures under combined compression and transverse shearing is put forward in this paper. An analytical method using the Bloch wave function and von Kármán plate theory is employed to predict the onset of damage based on the fact that failure of honeycomb structures is closely related to the buckling behavior of its core. After obtaining a bunch of data points of different stress conditions where damage occurs, a failure envelop for honeycomb cores under out-of-plane loads is formed and fitted by a nonlinear function. In order to validate the proposed failure criterion, experimental studies are performed on honeycomb sandwich structures consisting of Nomex honeycomb core and CFRP (carbon-fiber reinforced plastics) facesheets including in-plane compression, three-point bending and combined-compression-shearing. The accuracy of the proposed criterion is evaluated by comparing experiments with results predicted by progressive damage model incorporating the failure envelope of honeycomb core.