State of the Art
In over 30 years of global operation under harsh environments, maritime products, especially tailor-made structures with decreased safety margins and new materials, need specific, easy to handle and low-cost repair technologies to be acceptable for owners and authorities. Composite patch over-lamination was successfully tested in several projects and has been applied e.g. for repair of aluminium aircraft structures as well as thick steel sections in offshore and pipelines. Composite patches work as crack arrestors for existing damages. Effects of composite over-lamination to improve fatigue life of welded joints have been studied sporadically. No systematic design and processing guidelines is available.
Solution
For wider maritime applications, both for repair and joint fatigue improvement dimensioning, design, material selection and processing procedures will be established on a systematic basis and verified by tests and parameter studies (statistical models) on fatigue, aging and corrosion, first at lab scale. This will serve as a basis for quality assurance guidelines and approval by class societies. Tests will allow for directly comparing the effect of over-laminated specimens against untreated ones, as well as with the composite demos. Finally, real-life application tests and long-term monitoring of the effects will be carried out at a shipyard as well as on-board a real ship.
Potential
A comparatively easy-to-apply, robust and cheap method to extend the lifetime of many applications, within and beyond the maritime sector. Methods to strengthen and improve critical joints are already in use in other transport modes, but are new for the maritime sector, partially owing to the need for worldwide application, extreme environmental conditions and lacking long-term experience. In future, it may become a valuable method to assist various lightweight applications in different materials.