Fatigue analysis of honeycomb-composite sandwich beams

The fatigue behaviour of honeycomb sandwich beams is experimentally investigated through four-point bending tests. Two kinds of specimens, initially undamaged and damaged by interface debonding, have been tested. The fatigue tests results are presented in standard SN diagrams with a best curve fit of the experimental data, while the fatigue limit is evaluated through a stair-case procedure. Two different failure mechanisms were found: undamaged specimen failure is due to collapse of the compressed face, while damaged specimen failure occurs due to the collapse of the honeycomb cell walls at the tip of the debonded portion.