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The paper presents the results of the second half of a study funded by Research Partnership to Secure Energy for America (RPSEA) under project 10121-4401-02 Ultra-Deepwater Riser Concepts for High Motion Vessels. In the first half of the study, candidate riser systems consisting of alternatives to the steel catenary riser in both geometry – for the purpose of isolating the fatigue-critical riser touchdown zone from the motions of the vessel – and material were identified then down-selected to meet the constraints of high motion vessels like the conventional semi-submersible or a ship-shape floating, production, storage, and offloading vessel (FPSO). In addition to water depths approaching 10,000 feet, the present-day challenges of high pressure, high temperature, and sour well product are incorporated into the problem being framed. Results from dynamic analyses of riser concepts passing through the down-selection process are used to assess both utilization of strength capacity and fatigue performance. Comparisons of dynamic responses highlight the differences of each riser concept's behavior and provide understanding of the limitations of riser concepts. Assessments to other criteria such as cost, failure modes, and installation considerations are also used to ascertain safe riser systems that meet the performance demand of high-motion vessels.

The primary purpose of this analytical report is to compare tension-tension fatiguing of a carbon fiber composite to tension-compression fatiguing. Although carbon fiber composites hold up well in tension-tension fatiguing, there is little knowledge of the effects of tension-compression cyclic testing, especially in the higher regimes. The composites were fabricated using the vacuum assisted resin transfer molding method, VARTM, and are composed of IM7 four harness satin weave carbon fiber (54% by volume) and Epon 862 with curing agent W (46% by volume). The current research shows that carbon fiber composites are resistant to tension-tension fatiguing. However, when the composite must also endure compressive forces the fatigue life is considerably shorter. The results show that at R-ratios, maximum stress over minimum stress, of 0.1 &-0.1 tension-compression fatiguing will result in a failure three times earlier then tension-tension fatiguing for the same maximum stress value. Microscopy shows the extreme damage that carbon fiber epoxy composites endure during tension-compression fatiguing. ________________________________________________________________________ 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 5 19a. NAME OF RESPONSIBLE PERSON

A polystyrene polymer has been reinforced with single wall carbon nanotubes (SWNTs) to effect multifunctional capabilities. The SWNTs are produced by the HipCo process and are subsequently dispersed in the polystyrene resin matrix. The dispersion of the SWNTs in the polystyrene is enhanced by the use of a surfactant and composite samples at 0.0%, 0.1%, 0.2% 0.3% and 1.0% SWNT by weight are made. A multifunctional material is defined as a material with at least one additional property other than mechanical properties, and the desire is that the mechanical properties are not deteriorated due to the added nano-constituents. In this study SWNT reinforced polystyrene nano-composites are evaluated for their electrical conductivity as a function of SWNT weight percentage. The reinforced polystyrene nanocomposites are then evaluated for static strength, ductility and fracture properties to determine the effect of the nano-constituents on these mechanical properties.