Fatigue testing of composite patches for ship plating fracture repair

The objective of this study is to examine, through physical testing, the use of composite patches for preventing crack growth and extending the service life of ship plating. Fatigue tests were conducted on steel plates to experimentally validate the effectiveness of using composite patches as a means to prevent crack growth and extend the fatigue life of structural components. Specimens were tested with and without the use of composite reinforcements. Previous results of numerical analysis studies had indicated that a one- to two-order of magnitude increase in service life can be expected for the conditions tested. The experimental results presented here show increases closer to a single order of magnitude. The difference is attributed to two factors: failure mechanisms associated with debonding of the patch and cracking of the patch itself. Of critical importance, therefore, are the implementation of a quality-controlled bonding procedure and optimisation of the geometry and properties of the patch systems based upon the parent plate's properties and fracture conditions.