Application of bonded composites in the repair of ships structures – A 15-year service experience

Abstract

The carbon fibre composite overlays (patches) installed on a Royal Australian Navy frigate to inhibit the recurrence of superstructure fatigue cracking have been in service for 15 years now. The service life these composite repairs have accumulated is now sufficient for the ship to have gone through several complete maintenance cycles. The ship has also had a major upgrade/modification programme and been exposed to a full range of environmental conditions while it has served on its many active deployments. This paper examines the success of this repair methodology in the light of ship owner’s expectations. These expectations have two major aspects which are addressed here. The first is the effectiveness of the composite repair in restoring the strength and function of the damaged structure, the cost and timeliness in effecting that repair and the disruption incurred prior to and during the repair. The second aspect to determining the success of the composite repair is more long term. This comprises the durability and repairability of the composite repair itself, including the availability of clear, objective, and documented criteria for inspecting the repair in future years and authorising its continued service. Furthermore, the ease with which the repair itself can be removed and replaced to facilitate subsequent maintenance work or modifications to the parent structure, and the ability to survey the parent structure behind the repair all make up this second facet. Unfortunately, this aspect is less obvious to the repair team but quickly becomes apparent to the ongoing custodians of the structure. These custodians are also the ones most likely to be authorising the repair method to be used for similar damage in the future and so they are important stakeholders to keep ‘on side’. This paper reviews the service history of the carbon fibre overlays since their installation and comments on both the short and long term success of the repair methodology.