The manufacture of marine propellers in moulded anisotropic polymer composites
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.