Predicting Failure Loads of Undamaged Sandwich Honeycomb Panels Subject to Bending

This paper describes a method to predict failure loads accurately in undamaged sandwich panels subject to bending. The current method of predicting failure loads using linear wrinkling models is limited. A general lack of correlation exists between experimental and analytical/numerical wrinkling models. In some cases, the linear wrinkling models over-estimate wrinkling failure loads in undamaged panels by 100%. Various authors have tried to account for this discrepancy by modifying their linear models to take into account imperfections or irregularities in the structure or in some cases by using correction factors to get them to agree. This research uses these Finite Element models to find failure stresses in undamaged panels and to track the failure mode and determine the failure mechanism. Based on the failure mechanism found from the Finite Element analyses, a revised analytical expression is developed. These numerical and analytical models are verified against four point bend tests for a range of panel configurations. The results show that the panels collapse due to localised core crushing as a consequence of face sheet wrinkling. By using correct core failure criteria an almost perfect correlation is found between experimental, numerical and analytical results.