Microvibration tests for honeycomb plates of the spacecraft

The whole experiment was conducted to determine that the structural modal parameters can be divided into two regions. First, the frequency-response function (FRF) curves are obtained by sweeping with a thin metal string imposing different excitations to attain a low level of vibration, of which the test limitation is found to be 0.0005 N. Small offset of the curves and shifting natural frequencies are observed for different excitation levels, which are verified to be the natural characteristics of the combined structure itself. Then, a piezoelectric chip is used to excite the specimen and further measure lower acceleration vibration. From the test results for the combined structure, shifting of natural frequencies exists for different vibration levels, which is less than 1%. A small variation for modal damping ratio is also observed. For the combined structure connected by bolts, the bolts provide little support for the source of the damping, and the vast majority of damping of the combined structure comes from the honeycomb board.