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

This work investigates the propagation of elastic waves in spacecraft structures that have been induced by hypervelocity impacts. The structures considered were an aluminium plate, a Carbon-Fibre Reinforced Plastic (CFRP) plate, and a aluminium sandwich panel with CFRP facesheets. A number of impact experiments have been performed, during which the velocity of the surface displacement induced by the passage of the transient waveforms was monitored at a fixed distance from the impact location using a laser velocity interferometer (laser vibrometer). As an essentially massless and point-like sensing system, the laser vibrometer provides unparalleled high spatial, temporal and spectral resolution. The longitudinal, shear and flexural waves were clearly identified in measurement signals recorded during impact on all structure types investigated. A Fourier analysis of the signals revealed that much higher frequencies are propagated by the waves in the aluminium plates plate compared to the CFRP structures. In order to explain the different waveform types and wave propagation velocities, the theory of wave propagation in structures was reviewed. Material and structure parameters were then used to calculate the theoretical wave propagation velocities of the dominant waveform types and compare them against those experimentally determined.