Effects of ring stiffeners on the underwater collapse behavior of carbon/epoxy composite tubes

An experimental study was performed to analyze the dynamic buckling behavior of stiffened composite tubes. The structures analyzed were filament-wound carbon-fiber/epoxy composite tubes with press-fitted compliant and rigid aluminum ring stiffeners. The ring thicknesses were chosen for a consistent buckling pressure for equally spaced one, two, and three compliant stiffener configurations. The composite structures were submerged inside a pressure vessel and then subjected to increasing hydrostatic pressure until buckle initiation. High-speed photography and Digital Image Correlation were used to acquire full-field displacements and velocities of the collapse event. In addition, piezoelectric transducers were used to concurrently record the local dynamic pressure histories along the length of the tube. The results show that increasing the number of stiffeners for the same collapse pressure decreases the overall energy emission from the implosion event by more than 16%. However, the energy mitigation effects are also influenced by the location of the stiffeners in relation to the buckling initiation point.