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This thesis examines the feasibility of manufacturing small marine propellers from continuous fibre reinforced polymer composite materials. An appraisal of some current applications of composite materials in the marine industry is given, together with the moves shown towards the use of composites in the area of propeller design. It has been shown that manufacturing propellers in composite materials is theoretically more cost effective than traditional materials. The manufacturing route investigated is Resin Transfer Moulding, where some detailed investigations have highlighted some of the critical processing parameters necessary for successful production of laminates suitable for propellers and other high performance marine structures. A thorough testing programme of 4 novel designs of composite propeller is reported. Trials at sea on university run vessels has enabled many hours use to be logged, which has shown the fitness for purpose of propellers made from glass reinforced, epoxy composite. Experimental tank testing has helped to shape the remainder of the research by identifying the possibility of using hydroelastic tailoring to improve the efficiency of the propeller when a variety of operating conditions are required from the propulsion system. Further experience is required with respect to the the tooling construction and the life assessment of the propeller. To facilitate appropriate modelling of the propeller, spreadsheet based load prediction models have been used. Finite element analysis (FEA) was used to model the elastic characteristics of one particular design of novel composite propeller. This indicated that traditional geometries may be too stiff to allow significant performance advantages from the anisotropy of the material. However the potential does exist for modified propeller geometries made from composite to give some performance benefit. For specific applications, small marine propellers made from continuous glass fibre reinforced epoxy composite are likely to yield cost savings over traditional propeller materials.

No description available.

No description available.

No description available.

No description available.

This is the thesis which explains the progress made in the analysis, simulation and testing of plastics forming. This progress can be applied to injection and compression mould design. Three activities of plastics forming have been investigated, namely filling analysis, cooling analysis and ejecting analysis. The filling section of plastics forming has been analysed and calculated by using MOLDFLOW and FILLCALC V. software. A comparing of high speed compression moulding and injection moulding has been made. The cooling section of plastics forming has been analysed by using MOLDFLOW software and a finite difference computer program. The latter program can be used as a sample program to calculate the feasibility of cooling different materials to required target temperatures under controlled cooling conditions. The application of thermal imaging has been also introduced to determine the actual process temperatures. Thermal imaging can be used as a powerful tool to analyse mould surface temperatures and to verify the mathematical model. A buckling problem for ejecting section has been modelled and calculated by PATRAN/ABAQUS finite element analysis software and tested. These calculations and analysis are applied to the special case but can be use as an example for general analysis and calculation in the ejection section of plastics forming.

The objective of this research project was to carry out the investigation of the relationship between processing conditions, micromorphology and mechanical properties of isotactic polypropylene homopolymer using conventional and shear controlled orientation injection moulding (SCORIM) techniques by systematically changing carefully controlled processing conditions, mould geometry and compound additives. Both SCORIM and conventional techniques were employed for iPP injection moulding using three moulds of different shapes by varying the processing conditions, including nozzle temperature, mould temperature, injection speed, hold pressure and oscillating patterns of pistons. The results obtained were compared so as to indicate the differences in microstructure and physical properties resulting from the two moulding techniques. A range of analytical methods were employed. Optical transmitted light microscopy was used to reveal the skin-core morphology and preferentially oriented fibrous textures. Transmitted Electron Microscopy represented the enlargement of the fibrous alignment. Micro hardness analysed the hardness and isotropy characteristics by measuring the diagonal lengths of the indentations. Mechanical testing determined Young's modulus, the strength and toughness of the mouldings. X-ray diffraction exhibited the distribution of the cc, 6 and 7 crystalline phases of the iPP mouldings. The WAXS Debye patterns confirmed the existence of the preferred orientation through the thickness of the moulding. Differential Scanning Calorimetry analysed the thermal behaviour from the endothermal and exothermal curves. In the initial stage of the study, the polypropylene was moulded in the form of a standard tensile bar on a conventional Sandretto injection machine in order to obtain the basic characteristics of the polypropylene study material, which could then be used to compare with those properties to be gained using the SCORIM technique. A ring mould was then used in a Negri Bossi twin injection machine to investigate improvements in uniformity of micromorphology and dimensional reproducibility of mouldings made possible by four live-feed injection moulding. Later, a study was carried out on injection moulding of polypropylene by varying processing conditions, including three hold pressures, two mould temperatures and two nozzle temperatures for both conventional and SCORIM injection processes by using a rectangular bar mould in a Demag injection moulding machine. In the finial stage, the study explores the influences of composition, in essence a limited range of nucleating agents, and processing methods, and aspects of the micromorphology, dimensional control and the mechanical properties of polypropylene. Polypropylene, as a sernicrystalline polymer, represents a class of materials in which mechanical properties are strongly influenced by processing conditions and micromorphology.

Yes / The application of vacuum venting for the removal of air from mould cavity has been introduced in injection moulding with the intent to enhance micro/nano features replication and definition. The technique is adopted to remove air pockets trapped in the micro-features, which are out of reach for conventional venting technologies and can create considerable resistance to the melt filling flow. Nonetheless, several studies have revealed a negative effect on replication that could possibly arise from the application of vacuum venting. Although the incomplete filling of micro-scale features has often been attributed to poor venting, the limited research examining the application of vacuum venting has produced mixed results. In this work, the effect of air evacuation was experimentally investigated, monitoring mould and polymer temperature evolution during the micro injection moulding process by means of a high speed infrared camera and a sapphire window, which forms part of the mould wall. The results show that air evacuation removes a mould surface heating effect caused by rapid compression of the air ahead of the flow front and subsequent conduction of that heat into the mould surface. Hence, with the increase of the surface-to-volume ratio in micro-cavities, air evacuation has a detrimental effect on the cavity filling with polymers that are sensitive to changes of the mould temperature.