The impact of solid–fluid interaction on transient stress wave propagation due to Acoustic Emissions in multi-layer plate structures

In this work the effect of a solid–fluid interaction on stress wave propagation within a composite overwrapped pressure vessel (COPV) was investigated. A modeling approach capable of adequately capturing the multi-physics nature of the solid–fluid interaction is presented, and then validated through comparison to experimental waveforms and time–frequency distributions. With a validated modeling approach, a numerical study on stress wave propagation in COPV structures was undertaken. It was found that the compressibility of the pressurizing media used during the pressure testing of COPVs has an effect on the leakage of the propagating Lamb modes, as well as alternative direct paths that may propagate within the fluid. Results regarding the effects of the most common microstructural deformation mechanisms that occur in composite materials on the detected Lamb modes, as well as on the direct fluid path arrival are presented. Finally, the impact of source depth on the detected Lamb modes and the direct fluid path arrival was investigated. It was found that information gleaned from the direct fluid path arrival may have the potential for aiding Modal Acoustic Emission practices in source mechanism identification, determination of source orientation, as well as source depth estimation.