PR Jackson et al. / Materials Science and Engineering A 454-455(2007)590-601 2 mary of tensile properties for the N610/M/A and the N610/A composites Specimen Temperature Tensile modulus Tensile Failure strength(MPa) strain(%) B13-3 0. 3(54) l80(117b B13-1900 107 0.19 B2.1a1100 76(56) 57(115) N610/alumina composite 129(73) 17(665) 0.09 Tension B17-190 75(62) 0.07 T=23° B3-2a1100 116(65b) 05(59) 0.11 0 0.05 Data from Ruggles-Wrenn et al. [53] ABS STRAIN (% b Adjusted for V:=0.29 and 1100 C. Modulus, strength and failure strain obtained in compression tests at various temperatures are summarized in Table 3. Tensile and compressive stress-strain curves obtaine for N610/A and N610/M/A composites at 23, 900 and 1100oC are shown in Fig. 2(a-c), respectively. Note that in the case of w compression, stress magnitude versus strain magnitude curves are presented. In order to facilitate comparison between results n 100 obtained for specimens with different fiber volume fractions results in Table 2 as well as all tensile data in Fig. 2 were adjusted nsion for Vr=0.29. Results of the monotonic tensile tests in this study T=900° are consistent with those obtained in prior work [53], where the monotonic tensile behavior of the two composites is described ABS STRAIN (% Compressive failure in fiber-reinforced composites is erally associated with microbuckling of the fibers [54-57] T=1100°c Flexural stresses in a fiber due to in-phase buckling lead to the formation of kink zones. which can cause fracture in brittle longitudinal compressive damage and fracture typically involve 9 200 axial splitting of the matrix, buckling of the fibers, and kink g 160F Compression fibers [58, 59]. In the case of the 0/90 cross-ply composites, for a 0/900 cross-ply CMC, compressive failure initiated with a nucleation of axial cracks between adjacent fibers in the 90 ATension plies. These cracks gradually form shear zones, which induce Ruggles-Wrenn, 2006 0 ply flexure and cause buckling and kinking of the 0 fibers, leading to local fiber fracture and subsequent composite failure For porous matrix composites, the matrix is exceptionally weak (c) ABS STRAIN (% Fig. 2. Monotonic stress-strain curves for N610/M/A and N610/A composites at:(a)23C.(b)900 C and(c)1100C. Tensile data from Ruggles-Wrenn et ummary of compressive properties for the N610/M/A and the N610/A al. [53] are also shown. All tensile data are adjusted for V(=0.29 composites Specimen Temperature Compressive Compressive Failure and the fibers bear most of the load once the oo bundles buckle modulus(GPa) strength(MPa) strain(%) profuse matrix microcracking takes place, resulting in the loss of N610/monazite/alumina composite fiber stabilization and consequently the loss of the composites B12-1 -113 0.19 load-bearing capacity. Composite failure is then reached Bl4-1 11 -0.18 At all temperatures investigated, compressive stress-strain B14-2 -0.17 curves of N610/M/A are nearly linear to failure, indicating that B14-3 -0.16 compression damage and fracture occur in close succession. N610/alumina composite At 23 and 900C compressive m B8-8 72 0.29 B18-71100 0.59 monazite-containing CMC are similar to the corresponding ten- sile values. However, at 1100C the compressive strength isP.R. Jackson et al. / Materials Science and Engineering A 454–455 (2007) 590–601 593 Table 2 Summary of tensile properties for the N610/M/A and the N610/A composites Specimen Temperature ( ◦C) Tensile modulus (GPa) Tensile strength (MPa) Failure strain (%) N610/monazite/alumina composite B13-3 23 64 105 0.20 B9-1a 900 83 (54b) 180 (117b) 0.31 B13-1 900 55 107 0.19 B2-1a 1100 76 (56b) 157 (115b) 0.34 N610/alumina composite B3-1a 23 129 (73b) 117 (66b) 0.09 B17-1 900 75 (62b) 64 (53b) 0.07 B3-2a 1100 116 (65b) 105 (59b) 0.11 a Data from Ruggles-Wrenn et al. [53]. b Adjusted for Vf = 0.29. and 1100 ◦C. Modulus, strength and failure strain obtained in compression tests at various temperatures are summarized in Table 3. Tensile and compressive stress–strain curves obtained for N610/A and N610/M/A composites at 23, 900 and 1100 ◦C are shown in Fig. 2(a–c), respectively. Note that in the case of compression, stress magnitude versus strain magnitude curves are presented. In order to facilitate comparison between results obtained for specimens with different fiber volume fractions, results in Table 2 as well as all tensile data in Fig. 2 were adjusted for Vf = 0.29. Results of the monotonic tensile tests in this study are consistent with those obtained in prior work [53], where the monotonic tensile behavior of the two composites is described in detail. Compressive failure in fiber-reinforced composites is gen￾erally associated with microbuckling of the fibers [54–57]. Flexural stresses in a fiber due to in-phase buckling lead to the formation of kink zones, which can cause fracture in brittle fibers [58,59]. In the case of the 0◦/90◦ cross-ply composites, longitudinal compressive damage and fracture typically involve axial splitting of the matrix, buckling of the fibers, and kink banding or shear banding [60–62]. Lankford [60] reported that for a 0◦/90◦ cross-ply CMC, compressive failure initiated with nucleation of axial cracks between adjacent fibers in the 90◦ plies. These cracks gradually form shear zones, which induce 0◦ ply flexure and cause buckling and kinking of the 0◦ fibers, leading to local fiber fracture and subsequent composite failure. For porous matrix composites, the matrix is exceptionally weak Table 3 Summary of compressive properties for the N610/M/A and the N610/A composites Specimen Temperature ( ◦C) Compressive modulus (GPa) Compressive strength (MPa) Failure strain (%) N610/monazite/alumina composite B12-1 23 74 −113 −0.19 B14-1 900 47 −110 −0.18 B14-2 900 58 −103 −0.17 B14-3 1100 63 −97 −0.16 N610/alumina composite B18-8 900 72 −230 −0.29 B18-7 1100 73 −244 −0.59 Fig. 2. Monotonic stress–strain curves for N610/M/A and N610/A composites at: (a) 23 ◦C, (b) 900 ◦C and (c) 1100 ◦C. Tensile data from Ruggles-Wrenn et al. [53] are also shown. All tensile data are adjusted for Vf = 0.29. and the fibers bear most of the load. Once the 0◦ bundles buckle, profuse matrix microcracking takes place, resulting in the loss of fiber stabilization and consequently the loss of the composite’s load-bearing capacity. Composite failure is then reached. At all temperatures investigated, compressive stress–strain curves of N610/M/A are nearly linear to failure, indicating that compression damage and fracture occur in close succession. At 23 and 900 ◦C compressive modulus and strength of the monazite-containing CMC are similar to the corresponding ten￾sile values. However, at 1100 ◦C the compressive strength is