Abstract: The glass fiber plain woven panel honeycomb sandwich structure was subjected to low-velocity impact by punches with diameters of 25.4 mm, 38.1 mm and 50.8 mm at a notch 1 mm depth. The static compression and compression-compression fatigue tests after the impact under the punch of three diameters were carried out to study the residual strength, conditional fatigue limit, stiffness degradation, cyclic creep and failure mode of the specimens, revealing the compression-compression fatigue behavior of the honeycomb sandwich structure after low-velocity impact. The results show that the static residual strength decreases with the increase of punch diameter. When the punch diameter is 25.4 mm, the conditional fatigue limit is the maximum reaching 68.1% of the static failure load, while the counterparts in the cases of 38.1 mm and 50.8 mm are about 60% of the static failure load. Cyclic stiffness and cyclic creep both show a “three-stage” evolution feature during the whole fatigue life. In the first 10% of the fatigue life, the stiffness increases in high cycle fatigue, while in low cycle fatigue the stiffness decreases, and the cyclic creep occurs. Before 90% of the fatigue life, the stiffness remains stable, and the cyclic creep phenomenon is not significant. After 10% of the fatigue life, the stiffness decreases, and the cyclic creep phenomenon can be observed again. Compared with the static residual strength of the specimen, the dispersion of its fatigue residual strength is obviously larger. The failure mode of the specimen under fatigue load is similar to that under static load.

Key words: composites, fatigue, compression after impact, honeycomb sandwich structure, stiffness evolution