Estimation of stress concentration due to defects in a honeycomb core

•A technique by replacing defects with an elliptical hole was proposed.•Our predicted values of stress concentration agreed with numerical results.•Our predicted values of moment concentration agreed with numerical results. One of the authors has investigated the stress concentration in honeycomb core subjected to an uniaxial loading due to defect, in which some vertical cell walls are missing consecutively along one row. The objective of this paper is to extend the previous study to the consideration of more general cases, in which the damaged cell walls may exist more than one row and the honeycomb may be subjected to not only the uniaxial loading but also a biaxial loading. Based on our numerical results, it is found that the previous technique by replacing the defect with a crack are not suitable for estimating the stress field. Instead, a new technique by replacing the defect with an elliptical hole is proposed, and approximation methods for evaluating the stress and moment concentrations in the front of the defect are developed. The validity of these values is checked by the results of FEM.