Experimental Observations of Frictional Heating in Fiber-Reinforced Ceramics

The influence of fatigue loading history and microstructural damage on the magnitude of frictional heating and inter-facial shear stress in a unidirectional Sic fiber/calcium alu-minosilicate matrix composite was investigated. The extent of frictional heating was found to depend upon loading fre-quency, stress range, and average matrix crack spacing. The temperature rise attained during fatigue can be significant. For example, the temperature rise exceeded 100 K during fatigue at 75 Hz between stress limits of 220 and 10 MPa. Analysis of the frictional heating data indicates that the interfacial shear stress undergoes an initially rapid decrease during the initial stages of fatigue loading: from an initial value over 20 MPa, to approximately 5 MPa after 25 000 cy-cles. Over the range of 5 to 25 Hz, the interfacial shear stress was not significantly influenced by loading frequency. The implications of frictional heating in fiber-reinforced ce-ramics are also discussed. [Key words: composites, ceramics, fatigue, interfaces, shear.] I