Micro-dynamic Characterization Experiments For Honeycomb Plates Of The Spacecraft

On-orbit micro-vibration of the spacecraft means the vibration with amplitude below 0.1g caused by normal functioning of on-board equipment such as reaction wheels.Structures of the spacecraft are usually assembled mainly by honeycomb plates jointed by bolts.It is worthy to study dynamic characters under micro-vibration level for precise assessment of the disturbance response of the sensitive payloads.Results of this are presented from an experimental investigation of honeycomb plates under micro-dynamics.The dynamic response of honeycomb plates was characterized in terms of modal parameters at different micro-vibration level.Two main sweep approaches were raised on the ground for measuring the FRF curves of honeycomb plates including a single plate and a combined plate structure jointed by bolts,over a range of vibration acceleration from 10-1 g to 10-6 g,by which the natural frequencies and damping ratios could be obtained.Based on the preceding results from the micro-dynamic modal parameter experiments,several conclusions can be drawn concerning both the combined structure and the single plate.Under micro-vibration,the FRF curves and natural frequencies obtained by experiments show shift in very small range,which has been proved to be related to the characteristics of the honeycomb plate structure itself.No matter for the aluminum honeycomb board or carbon fiber honeycomb board,from the micro-vibration test results,at different excitation level,the error of frequency shift is less than 1%,and the corresponding structural damping ratios tend to a constant value.Compared aluminum honeycomb plate jointed by three bolts and single aluminum honeycomb plate,the damping ratios are same.So for connection structure,the bolt itself provides little damping,and the damping is most from the honeycomb board itself.In the free decay experiments,the damping ratios of the composite structure and these damping ratio values obtained by sweeping are very close,which proves that in the microvibration tests,the evaluation of mechanical properties of aluminum honeycomb panel is considered reliably under the response acceleration less than 0.1g.The damping ratios of honeycomb board structure jointed by single bolt are larger than honeycomb plate structure jointed by three bolts,in that the number of bolt has caused influence on the damping,which is verified by performing the tests for single aluminum honeycomb plate.Same to aluminum honeycomb panel,the natural frequencies and the damping ratios of the carbon fiber honeycomb plate also tend to a constant value under micro-vibration levels,which provides a reference and a guidance for structure mechanical characteristics of other structural plates or connected structures.