International Journal of Applied Ceramic Technolog-Sauder, Brusson and Lamon Vol. 7, No. 3, 2010 the comparison of grids of pixels constructed from im- before ultimate failure of the minicomposite. The fol- needed to be adapted to the specific geometry of mini- was used i 9. on, which has been established elsewher ages of the specimen surface taken at various loads. It composites with a curved surface and a rangy shape Comparison of deformations with those given by the brN(1-a,VOR LVDT extensometers provided the system compliance 2VFEm 2()(-a)0 Cs=0.26um/N(Fig. 1). It is worth mentioning that this value is close to that C determined on dry tows with Unloading-reloading cycles were conducted on a Er few specimens of each batch, in order to evaluate the E C interfacial shear stress (t). The interfacial shear stress was extracted from the width of the hysteresis loop (1+V)EmE+(1-2V)E measured during the last unloading-reloading cycle, just b2=[(1+v)E+(1-v)E (b)1000 1000 60000 M3(strain from image correlation) 50000 30000 600 25000 50 20000 15000 10000 010203040.5 203 (c)1200 120000 70000 1000 60000 80000 40000 500 10000 Strain (%) Strain(%) Fig. I. Tensile stress-strain curves obtained for Hi-Nicalon S/SiC minmicomposites:(a)MI,(b)M3 with deformations measured using both LVDT extensometers and the digital image correlation technique, (c) M5, and (d)M6.the comparison of grids of pixels constructed from im￾ages of the specimen surface taken at various loads.20 It needed to be adapted to the specific geometry of mini￾composites with a curved surface and a rangy shape. Comparison of deformations with those given by the LVDT extensometers provided the system compliance Cs 5 0.26 mm/N (Fig. 1). It is worth mentioning that this value is close to that Cs determined on dry tows with various gauge lengths.5,21 Unloading–reloading cycles were conducted on a few specimens of each batch, in order to evaluate the interfacial shear stress (t). The interfacial shear stress was extracted from the width of the hysteresis loop measured during the last unloading–reloading cycle, just before ultimate failure of the minicomposite. The fol￾lowing equation, which has been established elsewhere, was used19: t ¼ b2Nð1  a1VfÞ 2 Rf 2V 2 f Em s2 p dD ! s sp 1  s sp ð1Þ with a1 ¼ Ef Ec ð2Þ b2 ¼ ð1 þ nÞEm½  Ef þ ð1  2nÞEc Ef½  ð1 þ nÞEf þ ð1  nÞEc ð3Þ Fig. 1. Tensile stress–strain curves obtained for Hi-NicalonS/SiC minicomposites: (a) M1, (b) M3 with deformations measured using both LVDT extensometers and the digital image correlation technique, (c) M5, and (d) M6. 294 International Journal of Applied Ceramic Technology—Sauder, Brusson and Lamon Vol. 7, No. 3, 2010