Composite honeycomb sandwich columns under in-plane compression: Optimal geometrical design and three-dimensional failure mechanism maps

In this paper, three-dimensional failure mechanism maps are developed to investigate the in-plane compressive characteristics of all-composite honeycomb sandwich columns and optimize their load-weight efficiency. Analytical models are derived based on five possible failure modes, including shear macro-buckling, intracellular dimpling, face wrinkling, face fracture and debonding. The dominant failure mode can be determined by three dimensionless geometrical parameters, i.e., the length-height ratio of the sandwich column, the height ratio of face and core, and the relative density of honeycomb core. A series of three-dimensional failure mechanism maps are constructed based on the fiber orientations in the face sheet and honeycomb core. It is observed that failure mode transforms with dimensionless geometrical parameters in a spatial region. A typical three-dimensional failure mechanism map is experimentally validated. Sectional views in different directions are used to locate the boundaries of failure modes. All-composite honeycomb sandwich columns are designed and fabricated using the tailor-folding method. In-plane compressive experiments are carried out to verify the analytical models and three-dimensional failure mechanism map. The experimental results agree well with analytical predictions. Optimal geometrical design is performed to obtain the geometrical relations of honeycomb sandwich columns with the highest load-weight efficiency under in-plane compression. The novelty of this work lies in broadening the failure mechanism map to spatial region and optimal geometrical design.