BENDING FATIGUE DAMAGE MODELS OF STEEL HONEYCOMB SANDWICH PANELS

The four-point bending fatigue behaviors of steel honeycomb sandwich panels were investigated in this paper. The fatigue tests results were presented in fatigue life (S-N) diagrams. The results show that with a load ratio of R=0.20, the fatigue properties of specimens are significantly influenced by honeycomb cell orientations. The L-direction appears more suitable for cyclic loading than W-direction, and the fatigue strengths reach 1369 and 859 N, respectively. Based on the equivalent shear modulus degradation theory, the life prediction and damage evolution models were developed. Obviously, the lives of damage initiation for L-direction specimens are 86%-90% of the total number of cycles, while 73% at high load and reduce to 48% at low load for W-direction specimens. When the cores orientations were not concerned, the second order polynomial model and exponential model can be adopted to describe the damage evolution trends at high and low load levels, respectively. While the prediction models exhibit strong material dependent.