Vacuum Assisted Techniques For Improved Repair Performance In Legacy Fibre Reinforced Composites

Some large fibre reinforced polymer (FRP) marine structures—such as the U.K.’s mine countermeasures vessels—were designed decades ago. Of these early designs, some entered production, and have been in regular service for many years. When compared to modern FRP structures, the sparsity of literature available for legacy structures means they often constitute an asset maintenance dilemma. In these contexts, certain repair variables are often fixed according to the original design and are not possible to change easily. Examples could include the materials used in the repair and laminate structure. This paper presents a study aimed at improving the effectiveness of repairs on these legacy marine FRPs by using vacuum assistance to produce higher quality repairs, without changing the materials used in, or the design of, the repairs. First, the relationship between consolidation pressure applied to a wet lay-up repair and the repair’s performance, was investigated. Thereafter, a vacuum-assisted resin infusion process replaced the wet lay-up, to demonstrate further improvements in repair performance. Both of these improvements are based on the repair procedures, and are readily implementable within the asset maintenance programs of in-service legacy marine FRP structures. Extending the life of these structures by means of improved repair practices like these would mitigate their environmental impact by reducing unnecessary structure downtime and premature decommissioning, especially where end-of-life disposal processes are limited and environmentally harmful.