Performance Characterization of Phenolic Matrix-Composite Gears

Fabric reinforced phenolic gears have been utilized in timing gears to provide quiet operation for many years. Even so, there is a dearth of performance information of the type required by engineers to use rational design approaches when assessing new designs or the capacity capability of current products. This study is ongoing. Its first objective was to select an appropriate test vehicle and approach. The Power Circulating method of testing gears was selected, a rig designed and studies made regarding critical failure modes. Critical failure modes are, of course, the basis of design. They must be understood and prevented, consequently, the load and stress limits for their occurrence was determined by actual gear tests. The first results pertain to the limits associated with two modes, flank wear and tooth bending fatigue. Conventional stress cycle curves are presented for both failure modes. Some 29 gear sets were tested over a considerable range of torques. A new method heretofore untried was used to make wear measurements. It involved replicating the teeth periodically throughout the test. Over 40 replicas were made. The data reported on herein is for Duralite^R, a standard production material. Other materials are being evaluated.