Evaluation of damage within sandwich honeycomb panels subjected to impact fatigue loading

This work was aimed at investigating damage evolution within sandwich panels consisting of aluminum skins and Nomex (TM) honeycomb core, with three different values of the core densities, subjected to multiple impacts. Repeated impacts at low energy were conducted using an impact fatigue machine. Bending tests were conducted to determine the residual stiffness after impacts in order to analyze the evolution of a damage parameter D. A model was therefore proposed for describing the changes in this parameter as a function of impact cycles N. After repeated impacts, the D(N) curves are characterized by an S-shaped curve. A good agreement is observed between model and experimental results, the maximum standard deviation being less than 7% for different densities. Microscopic observations of the impacted specimens were conducted in order to evaluate the crater growth (associated with permanent indentation). The influence of the number of impacts on the dimensions of the impact zone has also been evaluated. For all the core densities, the permanent indentation gradually increases as a function of impact cycles.

Automated summary

This study investigated the damage evolution in sandwich panels with different core densities subjected to repeated impacts. Results showed that the permanent indentation on the panel surface gradually increased as the number of impacts increased. The proposed model for describing the changes in the damage parameter showed good agreement with experimental results, with a maximum standard deviation of less than 7% for various core densities.