Experimental and numerical study to investigate impact-induced wave propagation in spacecraft

Paper number

IAC-06-B6.3.11

Author

Dr. Frank Schaefer, Fraunhofer-Institut für Kurzzeitdynamik, Ernst-Mach-Institut (EMI), Germany

Coauthor

Mr. Guy Spencer, Ernst-Mach Institut, Germany

Coauthor

Mr. Shannon Ryan, School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Australia

Coauthor

Dr. Markus Wicklein, Ernst-Mach Institut, Germany

Coauthor

Mr. Michel Lambert, European Space Agency (ESA)/ESTEC, The Netherlands

Year

2006

Abstract

Impact damage from meteoroids and orbital debris is fairly well documented with respect to penetration of structures. Future ESA missions (e.g. GOCE, GAIA, LISA) include equipment sensitive to very low accelerations, which are on the order of 10-12 g. Thus, extremely high platform stability is required. Beyond the mechanical impact damage caused by impacts of hypervelocity particles, the local perturbations induced by shock and vibration have to be defined in the vicinity of the sensitive instrumentation on those missions. 

Therefore, it is important to understand the propagation of impact-induced shock waves, including the associated effects of dispersion and damping. To this purpose, hypervelocity impact experiments on aluminium and CFRP plate structures have been performed at impact velocities around 5 km/s using spherical aluminium projectiles, launched from two-stage Light Gas Gun accelerators. In the experiments, the surface displacement induced by the passage of the transient wave at various locations from the impact site was monitored using a state-of-the-art laser interferometer (laser vibrometer). The laser vibrometer is essentially a massless and point-like sensing system providing an unparalleled high spatial-, temporal- and spectral resolution. A second acceleration sensor was applied to monitor the quasi steady-state vibration of the plates over long durations after the impact. The different types of waveforms (longitudinal wave, shear wave, flexural wave) were clearly identified and their evolution as a function of time and of the distance from the impact location could be investigated. To allow extrapolation of the data to impact conditions outside the range of the capabilities of the hypervelocity accelerator, hydrocode impact simulations of the impact processes have been performed. In a first step, the numerical impact simulations have been validated against the measurements made in the experiments.  The second step was the extrapolation of the structure response from a hypervelocity impact at velocities of 10 km/s.

In this paper, the theory of wave propagation in thin plates will be reviewed and applied to the problem of hypervelocity impact-induced waves. The hypervelocity impact experiments are described and the transient measurements of the plate motion are presented and interpreted. The paper concludes with the comparison of the hydrocode impact simulations against the experiments and the application of hydrocodes to impact conditions not achievable by current light gas gun accelerators. 

Abstract document

IAC-06-B6.3.11.pdf

Manuscript document

IAC-06-B6.3.11.pdf (🔒 authorized access only).

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