In his doctoral thesis [1] and associated papers [2-4], Tim Searle undertook an appraisal of current applications of composite materials in the marine industry, focussing on the use of composites in marine propellers. The manufacturing route was Resin Transfer Moulding (RTM) and some critical processing parameters were identified for successful production of laminates suitable for propellers and other high performance marine structures.
Tim tested four novel designs, including trials at sea on university run vessels over many hours, and demonstrated fitness for purpose of composite propellers. Experimental tank testing helped identify the possibility of using hydroelastic tailoring to improve the efficiency of the propeller for a variety of operating conditions as required from the propulsion system. Modelling of the propeller used spreadsheet-based load prediction, followed by finite element analysis (FEA) to model the elastic characteristics of one particular design of novel composite propeller. This indicated that traditional geometries may be too stiff to permit significant performance advantages that exploit 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.
Recent developments in composite propellers have been reported in a Chinese review paper [5], then two chapters [6, 7] of Marine Composites: Design and Performance, edited by MAST Composites Engineering staff.