GALCIT Colloquium

A marine structure has to withstand a wide range of loading conditions such as underwater shock loading and repeated wave slamming events coupled with extreme variations in its environmental surrounding. For example, a naval vessel is subjected to a variety of temperatures, humidity levels, and UV radiation during its life span. Marine structures are subjected to hostile sea environments for extended periods of time and therefore experience degradation in mechanical properties and a change in their fracture behavior due to moisture absorption. In this talk, I will present results from fluid-structure interaction during an underwater shock focusing event. If the structure is made of a material that is sensitive to water uptake, its dynamic response might change depending on the level of water uptake currently in the structure. Therefore, a set of experiments were performed to determine the fracture behavior of PMMA, and neat vinyl ester resin samples when subjected to high strain rate dynamic loading. The test specimens were conditioned in various environments: "ideal" laboratory conditions, different relative humidity environments, and liquid environments for extended periods of time. After conditioning, the specimens were subjected to dynamic loading to study mode-I fracture. The method of transmitted caustics with simultaneous strain gauge measurements were utilized to obtain qualitative and quantitative data from the impact experiments, such as strain-to-fracture, stress intensity factor, and crack propagation velocity. Results show that the fluid-structure response changes drastically depending on the properties of the solid structure, and that fracture behavior due to high strain rate impact changes with moisture uptake.