Stress concentration in octagonal honeycombs due to defects

Different kinds of defects will form in the Additive Manufacturing process for honeycomb structures, which will lead to reductions in the mechanical properties. Missing cell walls along one row for the octagonal honeycomb is one of the typical defect, resulting in great stress concentration. To solve this problem, the defect region is approximated by an elliptical hole, and analytic formula of tensile stress and empirical formula of bending stress for the cell wall closest to the defect region are proposed. Comparison with the FEM results, verifies the effectiveness of the proposed analytical method. Further, the numerical results reveal that the degree of the stress concentration is not only influenced by the number of missing cell walls but also related to the aspect ratio. In addition, the aspect ratio of cell wall has a negligible effect on the results of the tensile stress but can sensitively affect the bending stress.