Gear fatigue life and thermomechanical behavior of novel green and bio-composite materials VS high-performance thermoplastics

In many applications, metal gears have been replaced by plastic gears because of their functionality and cost advantages. Despite their many benefits, the intensive use of plastics and composites raises sustainability issues because of the depletion of non-renewable petroleum resources and the pollution that is generated. Thus, alternative ecological solutions for plastic gears are necessary; however, little is known regarding ecologically designed gears. In this study, we propose two types of innovative gear materials. The first is a semi-ecological polyethylene bio-composite gear reinforced with birch fibers, and the second is a fully bio-sourced natural polyethylene gear with birch fibers. This study is the first time such fully ecological composite-plastic gears have been tested. The tests record the evolution of the fatigue and temperature over time under various operating conditions. Furthermore, acoustic emission is used to assess the evolution of fatigue cracks. The results indicate that the fully ecological gears are feasible and offer an alternative to traditional materials, such as engineering plastics, likely at a lower cost.