Tensile behavior and cyclic creep of continuous fiber-reinforced glass matrix composites at room and elevated temperatures

Abstract

In this study we investigated the stress-strain behavior at room and elevated temperatures and the tensile creep and cyclic creep response of a unidirectional SiC fiber-reinforced aluminosilicate glass matrix composite. The interfacial condition of the as-received material was measured by a push-out indentation technique. The stress-strain behavior was that expected for this kind of composite, i.e. "pseudoductile" behavior with extensive fiber "pull-out" at room temperature and brittle failure at intermediate temperatures (750 ~ due to oxidation embrittlement. The stiffness of the composite at 750 ~ was analyzed for different loading rates, highlighing the influence of the loading rate on apparent composite stiffness, due to matrix softening. The creep studies were conducted at temperatures above and below the softening temperature of the glass (Tg, 745 ~ in air. The cyclic creep experiments showed the existence of extensive viscous strain recovery during the unloading period. The creep strain recovery was quantified using strain recovery ratios. These ratios showed a slight dependence on the temperatures investigated (700 and 750 ~ The crept composites retained their "graceful,, fracture behavior only partially after testing, indicating that oxidation of the fiber/matrix interface due to oxygen diffusion through the matrix occurred in the peripheral area of the samples.

Cyclic creep and recovery behavior of Nextel™720/alumina ceramic composite at 1200°C

“…A similar increase in creep strain recovery ratio was observed during the 125 MPa creep-recovery test. Fairly high creep recovery ratios obtained for N720/A composite in this study are similar to the R cr values reported for the tensile cyclic creep-recovery of SiC/CAS [18] and SiC/AS composites [21], and for the flexural cyclic creep-recovery of SiC/BMAS composite [22].…”

“…Holmes et al [17,20] investigated tensile creep and creep-recovery behavior of unidirectional SCS-6 SiC f /Si 3 N 4 composites in air at 1200 • C. Wu and Holmes [18,20] studied tensile creep and creep-recovery of 0 • and 0 • /90 • Nicalon SiC f /CAS-II composites at 1200 • in high-purity argon. Work in this field has also been performed by Boccaccini et al [21] for an aluminosilicate glass matrix composite reinforced with SiC (Nicalon) fibers and by Sun et al [22] for barium-magnesium-aluminosilicate matrix composite reinforced with SiC fibers. The experimental results reported in literature suggest that, when compared to sustained creep loading, elevated-temperature cyclic creep loading can decrease the overall creep strain accumulation in fiber-reinforced ceramics.…”

“…Hence the knowledge of the composite response under both sustained creep and cyclic creep loading is important for material evaluation. Yet relatively few studies have investigated the creep-recovery behavior of the CMCs at temperatures over 1000 • C, the temperature range targeted for future applications [17][18][19][20][21][22]. Holmes et al [17,20] investigated tensile creep and creep-recovery behavior of unidirectional SCS-6 SiC f /Si 3 N 4 composites in air at 1200 • C. Wu and Holmes [18,20] studied tensile creep and creep-recovery of 0 • and 0 • /90 • Nicalon SiC f /CAS-II composites at 1200 • in high-purity argon.…”