Synthetic fibers used in composite materials as the root component of mooring ropes for oil platforms: an evaluation of mechanical properties

The oil industry found on some of the most used synthetic fibers for composites the answer to a relevant challenge: making kilometric mooring lines for offshore oil platforms substantially lighter. The engineering endeavor to anchor an oil extraction Platform upon high depth undersea oil basins, coupled with the barriers in terms of weight and cost imposed by mooring lines made out of cast iron chain links; arose the concept of using ropes build with synthetic fibers as a solution. Over the years, this approach, pioneered in Brazilian oil basins in early 00’s, embraced the technology of composites to use some of its characteristic synthetic materials as fiber for the anchoring ropes. Polyester (PET) always had a prominent role for this purpose due to its low cost and good mechanical properties, although more sophisticated materials such as Polyethylene (PE), Aramid (AR) and Liquid Crystal Polymer (LCP) came to offer other aspects in terms of creep resistance, water absorption and weight, increasing the market competitiveness. Along with the material substitution, the anchoring system has also changed: to replace the catenary layout, the taut-leg system was introduced. This new configuration allows reducing the length of the mooring lines, therefore decreasing their weight. It is basically a configuration in which the ropes are constantly under stress and anchored at a 45 degree angle with the seabed. So, it is possible to infer that since the fibers are constantly tensioned, whether in favor whether against the stream, the wind and the vessel’s dynamic positioning system influences; this cyclic force routine makes the proper knowledge of the mechanical behavior of those synthetic fibers an important topic. Aiming to foresee and compare the behavior of the four aforementioned materials when subjected to mechanical efforts such as tension, creep and fatigue; yarns composed by this fibers used in composite applications were submitted to experimental tests for evaluating their properties. A side effect of the materials qualities is the high endurance when mechanically demanded. Thus, to enable the performance of experimental tests and achievement of substantial results, the tests were conducted under utmost loading conditions in a way to...