International Journal of Applied Ceramic Technolog-Sauder, Brusson and Lamon Vol. 7, No. 3, 2010 Table Ill. Main Characteristics of the Tensile Behavior of Minicomposites. Hi-NicalonS/SiC E(GPa) or(MPa) ER(%) G,(MPa) E(%) t(MPa) 400(10)870(40)0.61(0.04)250(40)0.07(0.01) (1)350(20) M65 390(40)980(30)0.69(0.05)350(50)0.10(0.02)10(4) 40(170) M6 410(21)830(20)0.60(0.03)320(30)0.07(0.01)33(12)173(26) SA3/SiC E(GPa) o (MPa) Eg(%) g1(MPa) E1(%) t(MPa) d,(ur 420(20)855(255)0.380.25)290(30)0.08(002)280()40() 415(40)600(120)0.15(0.02)430(50)0.11(0.02) deviations are given in parentheses. gs modulus; O, failure stress; ER, failure strain; ol, stress at the onset of matrix cracking: El, strain at the onset of matrix cracking: t, interfacial shear stress; d,, crack spacing distance at saturation used.4.17,18 The current values of t fall within the range Minicompolle rain Bebavior of SA3/Sic terphase system because untreated fibers have beer Te of data determined on SiC/SiC minicomposites rein forced with as-received Nicalon or Hi-Nicalon fi- The tensile behavior of the SA3/SiC minicompo bers,. It is worth pointing out that t seems to ites was considerably erratic(Fig. 4) depend on the thickness of the Py C fiber coating: com For some test specimens, it was comparable with parable t was obtained for specimens MI, M3, and M5 that of Hi-Nicalon S/SiC minicomposites(Fig for which the PyC fiber coating 3), exhibiting the conventional features of SiC/ A larger t was obtained for specimen M6 with a thinne SiC minicomposites. Note the curve inflection coating of 30 nm. that was obtained at a larger strain(.5%), which Fracture surface images show a graceful composite her density of matrix cracks failure with pullout fibers of comparable length(Fig 3) and stronger fiber/matrix interfaces. The larger (a)1200 120000 1000 100000 80000 40000 sample 1 sample 2 0010203040506 Fig 3. Tensile stress-strain curves obtained for SA3/SiC minicomposites: (a )M2 and(b)M4.terphase system because untreated fibers have been used.4,17,18 The current values of t fall within the range of data determined on SiC/SiC minicomposites rein￾forced with as-received Nicalon or Hi-Nicalon fi- bers.4,18,22 It is worth pointing out that t seems to depend on the thickness of the PyC fiber coating: com￾parable t was obtained for specimens M1, M3, and M5 for which the PyC fiber coating thickness was 150 nm. A larger t was obtained for specimen M6 with a thinner coating of 30 nm. Fracture surface images show a graceful composite failure with pullout fibers of comparable length (Fig. 3). Tensile Stress–Strain Behavior of SA3/SiC Minicomposites The tensile behavior of the SA3/SiC minicompos￾ites was considerably erratic (Fig. 4): For some test specimens, it was comparable with that of Hi-NicalonS/SiC minicomposites (Fig. 3), exhibiting the conventional features of SiC/ SiC minicomposites. Note the curve inflection that was obtained at a larger strain (0.5%), which reflects a higher density of matrix cracks and stronger fiber/matrix interfaces. The larger Table III. Main Characteristics of the Tensile Behavior of Minicomposites. Hi-NicalonS/SiC E (GPa) rr (MPa) eR (%) rl(MPa) el (%) s (MPa) ds (lm) M1 400 (10) 870 (40) 0.61 (0.04) 250 (40) 0.07 (0.01) 9 (1) 350 (20) M3 390 (40) 980 (30) 0.69 (0.05) 350 (50) 0.10 (0.02) 10 (4) 340 (170) M5 420 (20) 880 (40) 0.63 (0.07) 410 (60) 0.10 (0.01) 16 (3) 220 (40) M6 410 (21) 830 (20) 0.60 (0.03) 320 (30) 0.07 (0.01) 33 (12) 173 (26) SA3/SiC E (GPa) rr(MPa) eR(%) rl (MPa) el (%) s (MPa) ds (lm) M2 420 (20) 855 (255) 0.38 (0.25) 290 (30) 0.08 (0.02) 280 () 40 () M4 415 (40) 600 (120) 0.15 (0.02) 430 (50) 0.11 (0.02) — — Standard deviations are given in parentheses. One test—not measured. E, Young’s modulus; sr, failure stress; eR, failure strain; s1, stress at the onset of matrix cracking; e1, strain at the onset of matrix cracking; t, interfacial shear stress; ds, crack spacing distance at saturation. Fig. 3. Tensile stress–strain curves obtained for SA3/SiC minicomposites: (a) M2 and (b) M4. 296 International Journal of Applied Ceramic Technology—Sauder, Brusson and Lamon Vol. 7, No. 3, 2010