This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.submitted to Composites Science and Technology 1 FATIGUE AND POST-FATIGUE TENSILE BEHAVIOUR OF NON-CRIMP STITCHED AND UNSTITCHED CARBON/EPOXY COMPOSITES ABSTRACTAn experimental study is described in this paper dealing with the tensile-tensile fatigue and the quasistatic post-fatigue tensile behavior of a structurally stitched multi-ply carbon composite and the unstitched counterpart. The influence of the stitching on the fatigue life and on the residual post-fatigue quasi-static properties in two principal direction is investigated. The fatigue behavior of both composites is represented by Wöhler-like diagrams. The damage imparted during fatigue is studied by X-ray analyses. The present work aims to provide a contribution to understanding of tensile fatigue and post-fatigue behavior of a structurally stitched multi-ply carbon composite. To assess the influence of the structural stitching on the mechanical response of the stitched composite the experimental data are compared to the ones of the unstitched carbon composite counterpart. The term 'structural' means that the stitching yarn does not only consolidate the plies (as the non-structural one does) but forms also a through the thickness reinforcement. The quasi-static mechanical response of the considered stitched carbon composite, produced in a different batch, were experimentally investigated in [12].The first part of the paper presents the characteristics of the two composites and the description of the experimental techniques applied. In the second part, the tensile-tensile fatigue life is presented and compared by Wöhler-like diagrams. Pictures obtained by X-ray device are used to investigate the damage patterns produced during fatigue after different number of cycles for a stress amplitude. The last part of the paper is dedicated to the post-fatigue residual mechanical properties of composites undergone different number of cycles. During the post-fatigue quasi-static tensile tests, the techniques described in detail in [13] (acoustic emission registrations and optic full-field surface strain measurements) were used to investigate the damage onset and development. MATERIALSThe stitched and unstitched preforms (see Figure 1 and Figure 2) are laminated using two Seartex / 23Each NCF has a polyester sewing thread (8.3 tex, 2.6 x 5 mm tricot + chain knitting pattern, 6 g/m 2 )that knits together the carbon plies. The fabrics are stacked to form a symmetric laminate [45/-45/0/90/45/-45] S and has a total thickness of about 4.2 mm before impregnation. 90º direction corresponds to the non-structural sewi...

More than 2,600 trillion cubic feet (Tcf) of natural gas reserves are considered as stranded internationally, outside of North America (i.e., not connected to production). This figure is essentially equal to the 2,800 Tcf currently connected to production. The total world reserves, including North America, are around 7,000 Tcf. Confusing the situation and putting impediments to smooth development, in contrast to oil, is the enormous disparity among natural gas prices in various parts of the world: $1/MMBTU in Russia, $2.5 in the US, $8 in Europe, $16 in the Far East. Lack of adequate and diversified transportation is the reason. It has been repeated often that oil is "fungible" and hence easy to transport with pipelines or easy to load and unload tankers, whereas natural gas is not. Natural gas can be transported with on-land pipelines but it gets rather expensive with underwater pipelines. Traditionally, the cost per length of offshore pipelines has been considered ten times the onshore cost. The main alternative has been liquefied natural gas (LNG) but other options have been offered such as compressed natural gas (CNG) and the chemical conversion of gas to transportable fuels, collectively called gas-to-liquids (GTL). The latter has changed over the years with alcohols getting new prominence. This work presents new information from recent experiences and attempts to provide a methodology of optimization for the transportation options for natural gas. Emphasis is given to new CNG technologies. Guidelines and new limits are presented to provide the appropriate means of transportation and reduce the volume of stranded gas currently in place. Worldwide demand for natural gas is expected to force the issue because of massive new needs, headed by China.

Marine compressed natural gas (CNG) has been considered in the past as a means of natural gas transportation but proved to be a non-starter for a number of reasons including long distances or large volumes of gas when compared with liquefied natural gas (LNG). However, marine CNG still figures economically attractive over shorter voyages (up to ~4,000km) and medium volumes of gas. Recent advances in containment systems are poised to provide marine CNG with the best opportunity to be resurrected as a major enabler of new and previously stranded hydrocarbons by becoming an important optimization tool to petroleum well performance. Almost half of offshore natural gas, SEC-type, reserves are considered" stranded" because of the high unit technical cost to harness natural gas in remote locations involving deep-water and/or pre-salt basins, and the lack of are liable and commercially viable market for the natural gas. Most of them do not contain enough gas to justify their own gas transmission solution, floating or onshore LNG production. Furthermore, inoperable gas affects oil production in many adverse ways from the logistics of handling and facilities capacity to the cost of the treatment. Marine CNG used as a wellhead fluid shuttling service for raw gas can generate significant monetary benefits for an operator attributable directly to the new technology and innovative application. Gas viewed like this is no longer a mid-stream product in need of further processing prior to sale, but becomes a potential upstream saleable product. We present here the new technology emphasizing the containment system manufactured with composite materials that are far lighter than metal and yet can withstand the 200-atmosphere pressure and corrosion from hostile raw gas composition straight out of the primary separator. CNG cargo containment system produced with composite materials can reduce overall steel weight by 50–80% and can operate with pressures ranging from 150 to 250 bars, sufficient to accommodate a wide range of gas-oil-ratios without the need of refrigeration.

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