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Diver-Applied Underwater Composite Patch Repair on Aluminum Hulls

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Technical Report

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Naval Postgraduate School Monterey United States

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This thesis investigates the feasibility of applying a composite repair patch in the underwater environment as an alternative repair on aluminum ship hulls over conventional welding and replacement repairs, which can be too costly and time consuming. An aluminum sample with a machined hole was chosen as the defected material to repair. After much research and leveraging of NSWCCDs approved topside composite repair procedure, a composite repair patch with E glass and a chosen underwater epoxy was selected. In a controlled laboratory setting, in two experiments, 24 different patched samples were tested for tensile load and a bending moment. Strain, load, and displacement were measured and compared with the baseline composite patch performance characteristics. A model was developed for each test using finite element analysis to predict the different stress data, and was used to investigate failure modes. The primary property used as a comparison for patch performance was strain, which was measured using strain gauges and numerically derived using FEA. The results showed that, in both loading conditions, the underwater composite repair patches were successful at significantly decreasing the strain at the hole i.e., the location of maximum strain concentration. Both experiments also showed that the interface strength increased as the underwater cure time of the patch increased.

Subject Categories:

  • Marine Engineering
  • Mechanics

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