N24-B CMC system

FIGURE 3. SEM micrographs showing (a) outside debonding for the N24-B CMC system and (b) inside debonding for the N24-A system. Note that the BN adheres to the Sylramic-iBN fibers in the outside debonding composites. 

FIGURE 8. Typical room-temperature tensile stress-strain curves for the inside-debonding N22 and N24-A CMC systems, and the outside-debonding N24-B CMC system (total fiber content -40 vol.%). 

FIGURE 10. Typical room-temperature stiess-strain curves for the N22 CMC system with Sylramic and Hi-Nicalon Type-S fibers, and for the N24-B CMC system with Sylramic-iBN fibers before and after combustion gas exposure ofthe systems in a low-pressure burner rig at -800°C for -100 hours. The fibers in the N22 systems each had carbon on their surfaces before BN interphase deposition. 

Table 2 hsts some key constituent material and process data for five SiC fiber-reinforced CMC systems recently developed at NASA. For convenience, these systems have been labeled by the prefix N for NASA, followed by their approximate upper temperature capability in degrees Fahrenheit divided by 100 that is, N22, N24, and N26, with suffix letters A, B, and C to indicate their generation. Also shown in Table 2 are the primary organizations where the different process steps were performed to fabricate each CMC system into a test panel. However, it should be noted that these steps have also been performed at other organizations, resulting in test panels with equivalent properties. 

---