PR Jackson et al. / Materials Science and Engineering A 454-455(2007)590-601 (b) 5mm 4 mm 5 mm mm Fig 9. Fracture surfaces of N601/M/A specimens tested in compression at: (a)900C, (b)900oC-side view, (c)1100 C and(d)1100 C-side view. b))is striking. The fracture surface of the N610/M/A spec- related fiber fracture was observed in all cases. However, imen exhibits a large damage zone, significant delamination, the pre-crept specimens produced somewhat smaller damage and extensive uncorrelated fiber fracture with the length of fiber zones and less extensive delamination than the as-processed "brushes"reaching 8 mm. Conversely, the fracture surface of material the N61O/A specimen does not have a"brushy"appearance and Additional monotonic tension and compression tests were shows only a short damage zone of approximately 6 mm. In conducted at 900C using specimens from billet B15. Tensile compression at 900C, the uncoated fiber CMC responds more strength and modulus values were close to those reported for like a monolithic ceramic than a composite As seen in Fig. 10(c other billets in Table 3, indicating that no fiber degradation and d), the fracture surface topography of the N610/A speci- occurred during processing of this billet. Compressive stiff- mens becomes more serrated at 1100C. Some delamination ness values (ranging from 48 to 58 GPa) obtained for billet and a larger damage zone(approaching 17 mm in length) are B15 were also close to those reported in Table 3 for billet observed B14. However, compressive strength values of B15 specimens Fracture surfaces produced in compression tests to failure were surprisingly low. While specimens from billet B14 pro- conducted on N61O/M/A specimens that had achieved com- duced compressive strength values of -110 and -103 MPa, the pressive creep run-out at 1100C were also examined. Prior strength values obtained for the B15 specimens were between creep had little effect on the fracture surface appearance. Uncor- 6 and -58 MPa Such unusually low compressive strengthP.R. Jackson et al. / Materials Science and Engineering A 454–455 (2007) 590–601 597 Fig. 9. Fracture surfaces of N601/M/A specimens tested in compression at: (a) 900 ◦C, (b) 900 ◦C—side view, (c) 1100 ◦C and (d) 1100 ◦C—side view. b)) is striking. The fracture surface of the N610/M/A spec￾imen exhibits a large damage zone, significant delamination, and extensive uncorrelated fiber fracture with the length of fiber “brushes” reaching ≈8 mm. Conversely, the fracture surface of the N610/A specimen does not have a “brushy” appearance and shows only a short damage zone of approximately 6 mm. In compression at 900 ◦C, the uncoated fiber CMC responds more like a monolithic ceramic than a composite. As seen in Fig. 10(c and d), the fracture surface topography of the N610/A speci￾mens becomes more serrated at 1100 ◦C. Some delamination and a larger damage zone (approaching 17 mm in length) are observed. Fracture surfaces produced in compression tests to failure conducted on N610/M/A specimens that had achieved com￾pressive creep run-out at 1100 ◦C were also examined. Prior creep had little effect on the fracture surface appearance. Uncor￾related fiber fracture was observed in all cases. However, the pre-crept specimens produced somewhat smaller damage zones and less extensive delamination than the as-processed material. Additional monotonic tension and compression tests were conducted at 900 ◦C using specimens from billet B15. Tensile strength and modulus values were close to those reported for other billets in Table 3, indicating that no fiber degradation occurred during processing of this billet. Compressive stiff￾ness values (ranging from 48 to 58 GPa) obtained for billet B15 were also close to those reported in Table 3 for billet B14. However, compressive strength values of B15 specimens were surprisingly low. While specimens from billet B14 pro￾duced compressive strength values of −110 and −103 MPa, the strength values obtained for the B15 specimens were between −36 and −58 MPa. Such unusually low compressive strength