Thermal Expansion of Polyether Ether Ketone Bearing Components

Abstract

Carbon fiber–reinforced polyether ether ketone (PEEK) is a strong candidate for aerospace bearing cages due to its low density and good mechanical properties. However, there are still concerns regarding its performance at the elevated temperatures seen in aerospace applications. In particular, an accurate measurement of PEEK's coefficient of thermal expansion (CTE) is critical to proper bearing design. In this paper, the CTE of as-manufactured PEEK cages was measured to determine the range of CTE that can be expected for production parts. A range of cage sizes and designs were considered in this study. Components that were manufactured from stock shapes through subtractive methods were studied in addition to components made via injection molding. The CTE of machined PEEK was found to be significantly higher than that of injection-molded PEEK and also varied significantly from part to part. In contrast, the CTE of molded PEEK cages was found to be fairly consistent between parts. Finally, the CTE of PEEK was found to increase above the glass transition temperature of 143 °C, but it was demonstrated that this increase is relatively small for injection-molded parts.