An experimental study of quasi-static indentation on composite sandwich panels supported rigidly

The indentation behaviour of sandwich panels could be affected by a variation of a large number of both intrinsic and extrinsic parameters. It is thus challenging not only to identify those parameters that dominate the indentation behaviour but also to ascertain how they influence the indentation behaviour across all applications. In this work, we focus on the indentation behaviour of rigidly-supported laminate-skinned sandwich panels up to an occurrence of incipient damage. Sandwich panels were constructed with carbon/epoxy skins of two different thicknesses, each in one of two lay-ups and aluminium honeycomb core. They were tested quasi-statically using hemispherical indentor. The effects of varying the thickness of loaded skin laminates, skin laminate lay-up, indentor diameter and panel support conditions on the indentation behaviour have been examined in terms of initial critical load and incipient damage mechanisms. On a basis of the extensive examinations of obtained results, we’ve found that (1) the mechanisms of incipient damage induced in all ten groups of sandwich panels were combined delamination in the loaded skin laminate and buckled honeycomb cells without debonding and there were clear indications that induced local stresses were dominated by ILS stress of the skin laminates and through-the-thickness compressive strength of aluminium honeycomb core; (2) varying the thickness of the loaded laminate skin has got a profound influence over the indentation behaviour of the sandwich panels in terms of critical load, critical indentation and initial stiffness; (3) the increase of indentor diameter had the substantial effect on the indentation behaviour of the sandwich panels; (4) varying either the lay-up of the loaded skin laminates or support conditions had very little effect on the indentation behaviour.