OMAE2017-61069 The Study of a New Concept of Flexible Pipe With Carbon Fiber/Epoxy Reinforced Inner Sheath

Flexible pipe has been widely used in offshore industry for many years. The traditional composite structure of flexible pipe consists of many layers, including multiple metallic layers, such as tensile armor, pressure armor and carcass, as well as nonmetallic layers, such as sheath and liner. Typical flexible pipe is heavy and requires complex manufacturing process, especially pressure armor and carcass manufacturing. Therefore, there is a desire to find a replacement to pressure armor and carcass. With the recent development of a new composite material with lighter weight and higher strength, it now becomes possible. This new composite material is called epoxy compounded carbon fiber (EP/CF). Carbon fiber is 10 times stronger than steel, while it is only 1/5 of the steel weight. Epoxy protects carbon fiber from environmental conditions such as high temperature and corrosion, also bond carbon fiber together and help to redistribute the loading between carbon fibers. This paper is to present a new concept of flexible pipe by applying the EP/CF material to flexible design. In this new flexible concept, EP/CF is used to strengthen the inner sheath by surface activation treatment of sheath material. This provides excellent hoop strength to resist the inner pressure, hence provides a good replacement to the pressure armor and carcass. A new FEA analysis method with ABAQUS is also presented in this paper. In the analysis approach, all helix fibers are modelled using predefined beam element, and EP/CF reinforced inner sheath is modeled using laminated composite shell. Nonlinear FEA analysis is carried out in ABAQUS to investigate the tension and bending behavior of flexible pipe with reinforced inner sheath, including the performance of inner pressure resistance, which is one of the key performances. Analysis is also carried out to study the benefit of using EP/CF on outer sheath reinforcement for collision protection. Lastly, the economics and feasibility of this concept are discussed, and conclusions are drawn.