Design Optimization and Fatigue Evaluation of Wood Composite Gears

Abstract

Abstract: A great deal of research in polymer gears has gained importance in the last decade. It is necessary to highlight the different polymer materials and fibers used for gears to meet the requirements of a particular drivetrain application. With the increasing need to recycle already used materials, there are trends towards the use of BIO-based materials that would allow recycling and reuse in secondary, less demanding parts or assemblies. To integrate these materials into a real mechanical part such as a gearbox, their mechanical, thermal, and tribological operational performances must be evaluated. In this study, life tests of wood-polymer composite gears were performed using High-Density Polyethylene (HDPE) reinforced with 20% spruce fibers and the same polymer matrix reinforced with 20% beech fibers. The wood-polymer composite gear was tested with a mating steel pinion. The study aimed to determine the life cycles to failure of wood-polymer composite gears, the temperatures generated in the gear pair contact, and the flank wear characteristics of both types of wood composite gears. The results show that HDPE with beech fibers lasts on average 15% longer compared to HDPE with spruce wood fibers. When analyzing the flank wear, the beech fibers proved to be more wear-resistant than the spruce fibers in the same polymer matrix. The analysis of the failure mechanisms shows that the crack propagation at the tooth root is slower in HDPE reinforced with beech fibers compared to HDPE with spruce fibers due to the better mechanical properties. Keywords: High-density polyethylene; Wood; Fibers; Gears; Fatigue; Wear