Environmental effects on fiber debonding and sliding in an SCS-6 SiC fiber reinforced reaction-bonded Si 3N 4 composite

Abstract

Because fiber/matrix interfacial mechanical properties are critical to the overall strength and toughness of fiber-reinforced composites, several test methods have been developed to evaluate fiber debonding and sliding behavior. Most interface testing of metal or ceramic matrix composites has been performed in room (laboratory) air at room temperature without considering the effects of moisture or testing environment on the test results. Even though chemical reactivity at the fiber/matrix interface may be insignificant at room temperature for these composites, it is well known that friction and wear between sliding surfaces can be strongly dependent on environment, even at room temperature. Therefore, awareness of the environmental sensitivity of interface testing is necessary for the reliable interpretation and comparison of interfacial mechanical property tests. In addition, such awareness is needed to prevent the potentially inaccurate prediction of the performance of composites intended for service in high altitude or space environments based on interface tests completed in laboratory ambient. This paper will demonstrate the effect of environment on fiber debonding and sliding as evaluated by fiber push-out testing at room temperature of an SCS-6 SiC fiber reinforced reaction-bonded Si{sub 4}N{sub 4} matrix composite (SCS-76/RBSN). SCS-6/RBSN is a promising candidate material for component applications inmore » advanced heat engines, and its low fiber/matrix interfacial shear strength is a key determinant in its demonstrated toughness (as evidenced by graceful failure beyond matrix cracking).« less