Date of Award
Master of Science in Mechanical Engineering and Applied Mechanics
Mechanical, Industrial and Systems Engineering
A comprehensive series of experiments was conducted to understand the effect of confining environments on the mechanics of implosion of carbon/epoxy composite cylinders. In the case of implosion, a confining environment can be defined as any environment which limits, restricts, or otherwise manipulates particle motion towards an implodable volume during an implosion event. As such, the implosion of composite structures within two different types of confining environments was investigated: implosion within full confinement, and implosion within partial confinement. It was found that a fully-confining environment considerably limits the energy available to drive implosion, and thus two implosion phenomena can result: full implosion and partial implosion. Full implosion occurs when the energy contained in the compressed water bounded by the confining structure is sufficient to cause wall contact in the implodable. This resulted in water-hammer pressure spikes at the ends of the confining chamber due to the formation and subsequent collapse of large cavitation bubbles. Partial implosion occurs when the energy contained in the compressed volume of water bounded by the confining structure is not sufficient to cause wall contact in the implodable structure, causing an arrest in the implosion process and resulting in structural oscillation of the walls of the impolodable. This resulted in pressure oscillations of the same frequency throughout the confining chamber, with oscillations increasing in amplitude with distance from the axial center. In partially-confining environments, it was found that the implosion of composite structures resulted in pressure oscillations which behaved as a damped harmonic oscillator of frequency 𝑓, amplitude Δ𝑃𝑚𝑎𝑥, and damping ratio ξ. Pressure oscillations were experimentally characterized, and an analytical investigation was conducted in which expressions for 𝑓 and Δ𝑃𝑚𝑎𝑥 were derived, showing good agreement with experimental results. Finally, it was experimentally shown that by decreasing the energy stored in the compressed volume of water bounded by the partially-confining structure, implosion with dwell can be achieved, in which there is a short pause in the implosion process. This phenomenon is analogous to partial implosion within full confinement.
Salazar, Christopher J., "DYNAMIC INSTABILITY OF COMPOSITE CYLINDERS IN UNDERWATER CONFINING ENVIRONMENTS" (2019). Open Access Master's Theses. Paper 1451.
Available for download on Saturday, October 19, 2019