COMPOSITE SHAFTING FOR NAVAL PROPULSION SYSTEMS

Abstract

ABSTRACTAdvanced composite materials offer the potential to improve naval propulsion shafting by reducing corrosion and galvanic effects, weight, life‐cycle costs, bearing loads, magnetic signature, alignment problems, and use of strategic materials; and by increasing allowable fatigue stress, flexibility, and vibration damping characteristics. The Navy is investigating the potential impact and feasibility of a standardized family of composite shaft sizes manufactured by a highly‐automated filament‐winding process incorporating continuous graphite and glass filaments in a thermosetting epoxy resin matrix. A small‐diameter (2.5 inch) filament‐wound composite propulsion shaft is being evaluated in a 2‐year trial aboard a Naval Academy yard patrol vessel (YP‐654 class). Encouraging results to date from the YP trial, laboratory torsion and fatigue testing, and analytical studies employing finite‐element stress‐analysis techniques, have led to current R&D efforts to develop a Navy‐standard composite shafting “base laminate,” design and procurement specifications, and metal/composite coupling technique suitable for the largest diameter shafting systems. Laboratory evaluations with small diameter composite shafts have demonstrated their torsional loading and fatigue capabilities, and have shown the joint to a metal flange or propeller as the consistent weak point in the system. This paper presents a summary of assessments of composite shafting in terms of size, weight, and costs comparisons with conventional materials; Navy experience with the YP composite shaft installation; discussion of finite element investigations of composite shafting and coupling system models; and technological areas requiring additional investigation.