Fatigue Damage And Life Prediction Of Lightweight Foam Sandwich

Sandwich structure composed of lightweight core material and thin panel were more and more widely used in aviation,aerospace and shipbuilding and other industries owing to the excellent performance.At present,China is relatively backward in the study of sandwich composites.The sandwich structure material used in domestic high-tech industry depends on import.Considering that sandwich structure is more likely to suffer from fatigue load in practical engineering,it is meaningful to study the fatigue damage of sandwich structure.First of all,the basic characteristics of sandwich structure and relevant mechanical parameters were discussed,and some common damage modes and causes were discussed.In this paper,the PMI foam sandwich structure was selected.All the experiments are carried out by three-point bending test.The basic characteristic parameters of this structure are obtained through the static strength test to fully understand the mechanical properties of aluminum foam,foam core and PMI foam sandwich structure.According to the results of the static strength test,the fatigue damage tests were carried out with the controlled variable force load.The failure mode of the structure is local depression failure.The damage evolution formula with force controlled was established by introducing the change of displacement as damage parameter,and the damage process is predicted well.After that,the fatigue damage test with displacement controlled was carried out.It was found that the damage mode and the fatigue damage process of the sandwich structure were obviously different from the load control mode.When the maximum control displacement is smaller,the failure mode is the separation of the panel and the foam layer;when the displacement is large,the panel is broken and the foam core is collapsed.The damage evolution formula with displacement controlled was established by introducing the change of load as the damage parameter,and the damage process of the two modes was predicted well.Finally,some innovations,shortcomings and future research directions of this study are prospected.