Investigation of parameters governing the damage and energy absorption characteristics of honeycomb sandwich panels

Honeycomb sandwich panels of various skin thicknesses and core densities have been investigated under quasi-static loading in bending and indentation with both hemispherical (HS) and flat-ended (FE) indenters. Core crushing, top skin delamination, and top skin fracture are identified as major damage mechanisms. Their characteristics and energy-absorbing capabilities are established using load-displacement and load-strain curves and inspections of cross-sectioned specimens. The effects of varying skin thickness, core density and type, indenter nose shape, and boundary conditions on the damage and energy-absorbing characteristics are examined. The variation of the indenter nose shape is shown to induce a change in the damage mechanisms and have the most significant effect on energy absorption, especially for panels with relatively thicker skins. Increasing the skin thickness significantly increases not only the initial threshold and ultimate loads but also the absorbed energy (AE) of the panels. Increasing the core density has a very small effect on either the ultimate loads or the energy-absorbing capacity, while the effect of the support conditions on the damage and energy-absorbing characteristics is small. The larger 220 mm diameter panels absorb significantly more energy than the 100 mill diameter panels because of the much greater ultimate displacement. Different core materials with a similar density show little difference in either the damage or the energy-absorbing characteristics due to the limited contribution of transverse shear resistance. Panels with a delaminated top skin have lower threshold loads under both indenters and lower ultimate load for the HS indenter.