Free vibration characteristic of plain woven fabric laminates with multiple delaminations around a central hole

The free vibration characteristic was studied for plain woven fabric laminates with multiple delaminations around a central hole. Finite elements analysis models were established by MSC. Nastran/Patran for plain woven fabric laminates with elliptical multiple delaminations around an elliptical central hole. From some typical examples，the effects of the holes' size，multiple delaminations' size and damage's location on the vibration characteristic were discussed. The results show that the effect of small-sized hole and delaminations is not great. On the natural frequencies，the effect of transverse elliptical multiple delaminations around an elliptical central hole is more serious than that of lengthways elliptical multiple delaminations around an elliptical central hole；the natural frequencies are very sensitive to damages location，and less sensitive to multiple delaminations' size and the holes' size.