Creep-buckling of hexagonal honeycombs with dual imperfections

The creep-buckling of hexagonal honeycombs with dual imperfections of variable-thickness, cell-edge, cross-section and non-straight profile of cell edges is theoretically analyzed here. By assuming that the material making up cell edges follows power law creep, the theoretical expression for describing the failure time for the onset of creep-buckling of hexagonal honeycombs with plateau borders and curved cell edges is derived. Theoretical results indicate that the effects of dual imperfections on the failure time for the onset of creep-buckling are more significant than those of single imperfection. Moreover, the required normalized compressive stress for hexagonal honeycombs with dual imperfections in a given failure time can be directly estimated from the product of that with single imperfections. In addition, it is found that creep-buckling is more likely to occur when imposed compressive stress is close to elastic buckling strength. But, creep-bending dominates when imposed compressive stress becomes much smaller. The normalized compressive stress for a transition from creep-buckling to creep-bending is affected significantly by the curvature of cell edges but slightly by the solid distribution in cell edges.