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Composite systems are a generally-accepted method for repairing corroded and mechanically-damaged onshore pipelines. The pipeline industry has arrived at this point after more than 15 years of research and investigation. Because the primary method of loading for onshore pipelines is in the circumferential direction due to internal pressure, most composite systems have been designed and developed to provide hoop strength reinforcement. On the other hand, offshore pipes (especially risers), unlike onshore pipelines, can experience significant tension and bending loads. As a result, there is a need to evaluate the current state of the art in terms of assessing the use of composite materials in repairing offshore pipelines and risers. The significance of the body of work presented herein is that this study is the first comprehensive evaluation of a composite repair system designed for the repair of offshore risers using a strain-based design method coupled with full-scale prototype testing. This paper presents findings conducted as part of a joint industry effort involving the Minerals Management Service, the Offshore Technology Research Center at Texas A&M University, Stress Engineering Services, Inc., and several composite repair manufacturers to assess the state of the art using finite element methods and full-scale testing methods. Representative loads for offshore risers were used in the test program that integrated internal pressure, tension, and bending loads. This program is the first of its kind and likely to contribute significantly to the future of offshore riser repairs. The end result of this study was the development of a carbon-fiber repair system that can be easily deployed to provide significant reinforcement for repairing risers. It is anticipated that the findings of this program will foster future investigations involving operators by integrating their insights regarding the need for composite repair based on emerging technology.

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Decreased mechanical strength in a fiber reinforced plastic part can often be traced to poor or incomplete impregnation of the reinforcing fiber with the matrix. To properly understand the impregnation process in the design of new composites manufacturing machinery (specifically in unidirectional tape machines), or to optimize wetout in existing machine designs, the raw process materials and their relationship within the process environment must be examined. The critical factors are: resin viscosity vs. temperature; the work of adhesion between the fiber and resin; and the problem of forcing the resin to completely penetrate a fiber bundle. If these factors are known, nip rolls can be designed to meet a specific process envelope, or in the case of existing equipment, the existing process envelope for specific fiber/matrix combinations can be manipulated for maximum fiber wetout.