Call number: LD2668 .T4 1961 L36

Use of lightweight materials is an important part of reduction of fuel consumption by commercial aircraft. A considerable number of structural aircraft parts are therefore built of thin layers of epoxy pre-impregnated carbon fibres stacked to laminates. Manufacturing these by hand is costly and different methods of automation have therefore been developed. One cost-effective way of manufacturing is Automated Tape Lay-up of flat stacks followed by a Hot Drape Forming operation. A well-known problem in the industry within forming is fibre wrinkling, which can cause a serious strength knock down. The focus of this thesis has therefore been on understanding how and why wrinkles develop during forming of multi-layer stacks and, based on this, investigate different methods for process and material improvements. The work presented initially investigates the dependency between stacking sequence and wrinkle development. It is shown that wrinkle free forming can be obtained by changing the fibre stacking order. In the following investigation it is shown that the wrinkles cannot be entirely eliminated by local stiffening of the critical layers. In a, related study it is shown that different kinds of wrinkles develops during forming; wrinkles may be either due to global buckling of the entire lay-up or local compression of single layers. Global buckling is due to excessive material. Local compression occurs as the material shear during forming. The work presented leads to an understanding of the importance of making the beneficial neighbouring fibre layers interact during forming. One way to connect neighbouring layers is to tailor the interlayer properties. A study is presented that shows how local manipulation of interlayer properties may steer the multi-layered material into a different deformation mechanisms. The manipulation in this thesis is performed using Multi Wall Carbon Nano Tubes, thermoplastic veils or consolidation of thermoplastic toughener particle interlayers. / <p>QC 20160425</p>

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The consumption of large quantities of fossil fuels on a yearly basis for energy purposes has led to the release of vast quantities of carbon dioxide into the Earth s atmosphere leading to global warming. In order to decrease the amount of carbon dioxide entering the atmosphere, procedures such as carbon dioxide capture and storage are currently being implemented, although this process is successful in decreasing atmospheric carbon dioxide concentration it results in the mindless storage of an otherwise synthetically useful reagent. The development of a viable method to capture carbon dioxide, followed by synthetic utilisation often referred to as CCU is currently gaining much attention. The main challenges in the development of a suitable utilisation reaction are energy and cost efficiency as well as the use of environmentally friendly conditions. Previous reports on utilisation include the catalytic incorporation of carbon dioxide into epoxides under electrochemical conditions, however this process had several drawbacks. In this project the shortcomings of this reported procedure have been addressed in order to develop a potentially viable utilisation process. The catalyst free electrocarboxylation of mono-substituted epoxides, using a magnesium anode/copper cathode electrode couple and tetrabutylammonium bromide supporting electrolyte in a sealed single compartment cell, was achieved under mild reaction conditions (1 atmosphere carbon dioxide pressure, 60 milliamperes constant current and 50 degree celsius heating), producing the corresponding 5-membered cyclic carbonate product in excellent yields (65-96%). Interestingly the use of sono-electrolysis allowed the reduction of para-substituted aromatic epoxides. The stoichiometric addition of tetrabutylammonium bromide was key for the effective activation of carbon dioxide and the epoxide. Similar carbon dioxide incorporation into analogous mono-substituted aziridines, synthesised using a modified Wenker synthesis allowed the formation of the corresponding cyclic carbamates in moderate to excellent yields (32-90%). The selective synthesis of 6-membered cyclic carbonates from oxetane substrates was also achieved in good yields (60-70%) as well the non-selective synthesis of polytrimethylene oxide. The electrochemical process also allowed the tandem formation of magnesium carbonate in quantitative yield (85%). Furthermore substrate free electrocarboxylation allowed the synthesis of alternative iron and zinc carbonates in excellent yield (83-85%) as well as the selective synthesis of aluminium oxalate (99%). Coupled with the high recovery of the supporting electrolyte (90%), this work has demonstrated the economical synthesis of industrially useful chemical feed-stocks under green conditions.

Microbial decomposition of soil organic matter (SOM) releases around 98 Pg of C (as CO2) to the atmosphere annually. Quantifying CO2 emissions from SOM is necessary to monitor and manage them but is complicated by proximate respiration of CO2 from plant roots, and by the influence of roots on SOM decomposition rate. Differences in the natural abundance of 13C in root and SOM-derived respiration (of < 10 ‰ in most temperate ecosystems) can be used to apportion their contributions to soil-surface CO2 efflux. However, this is challenging because all three δ13CO2 measurements are susceptible to significant sampling errors, which this study set out to identify and resolve, as follows. Respired CO2 sampled from excised roots is 13C-depleted by 1.8 ‰ (± 0.47) compared to intact roots due to the contribution of CO2 from root wounds. Root-respired δ13CO2 is more reliably measured using chambers around live, intact roots. These chambers also permit detection of diurnal changes in root-respired δ13CO2. Soil disturbance during sampling and root removal changes the carbon substrates available to microbes and this is reflected in a rapid (1-2 hours) decrease in δ13C of respiration of c. 4 ‰. This change can be regressed to estimate the δ13CO2 of microbial respiration from undisturbed soil. Techniques for measuring soil-surface efflux δ13CO2 induce method-specific biases of as much as 5 ‰, as measured in intact mesocosm soil and when simulated using a numerical diffusion model. Discrepancies between measurements and model predictions may be due to complexities of gas transport not currently accommodated in diffusion models, namely, near-surface advection and non-uniform soil diffusivity. Using improved techniques, this study used natural abundance 13C partitioning to assess priming effects, identify distinct environmental drivers of root-respired and SOM-derived CO2 fluxes, and detect differences in soil carbon cycling between tree species, possibly attributable to mycorrhizal type.

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This study investigated the heat transfer within the anode material moving through and heated by an electric arc. The arc was a low current (< 16 A) atmospheric electric discharge between a carbon rod cathode, and a moving carbon felt anode. The carbon arc was a low current(<16 A) electric discharge between a cathode constructed of a carbon rod, and a moving carbon felt anode. The thermal profile within the anode material was predicted by a system of differential algebraic equations, adapted from the model developed by (Stark and Fricke, 1993). This set of equations was run using the software MATLAB R2011b, using a numerical integrator with consideration taken for sparsity. The change in degree of graphitisation was then predicted using the thermal profiles developed. This indicated that while the graphitisation of the surface of the felt exposed to the arc increased (from about 10% to about 99%) this effect did not penetrate far into the felt. At a depth of 0.3 mm there was very little increase in graphitisation (about 7% increase at slow movement rates, negligible at standard rates), indicating that this gaphitisation degree was unlikely to explain the improvement of battery cells produced using this material compared to non–arc treated material. Vaporisation of carbon due to the arc was then investigated as a possible explanation. With a similar activation energy to graphitisation a similar profile was obtained.

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