1562 v.A. Krab et al. Composites Science and Technology 61(2001)1561-1570 200m Fig. 1. Nextel610/AS composite polished cross section optical micrograph. under the trade name Gen IV. The Nextel610 fibers, pro- duced by the 3M Company [12] consisted of polycrystal δ土 line alpha alumina. The fibers were bundled into tows containing approximately 400 individual fibers, and woven into an eight harness satin weave(&HSW) cloth The composite panel used in this study contained 12 plies 0.8mm The matrix consisted of a porous alumina-silica(AS) 2 mm matrix. Fiber volume fraction was 33%. Extensive microcracking was present throughout the matrix as a result of the shrinkage which occurred during the pyrolysis processing(Fig. 1). These microcrack distributed throughout the interior matrix as well as on the specimen surface. The resulting composite contains sintered matrix which is bonded to the fibers with no naturally occurring Fig. 2. Schematic of (a) single edge notched specimen geometry. For All meng and microstructure are discussed in (4.5%e specimens tested at 23.C,W=12.6 mm, and at 950oC,W=25.4 mm or engineered interphase. Further details of the compo for edge notched fracture tests. The lines within the gages indicate the notched specimens [13] in lab air, using a servo-con direction of strain measurement trolled, hydraulic, horizontal test system [14, 15]. The specimen ends were rigidly clamped using friction grips, thus resulting in rotationally constrained end opening displacement(CMOD) was measured using a conditions(Fig. 2). The fiber orientation relative to the high resolution, knife edge extensometer. At 950oC a loading axis was [0%90] for all edge notched speci- high temperature extensometer, with quartz or alumina mens. During the room temperature tests, crack mouth rods, was used to measure CMOD. The extensometerunder the trade name Gen IV. The Nextel610 fibers, pro￾duced by the 3M Company [12], consisted of polycrystal￾line alpha alumina. The fibers were bundled into tows containing approximately 400 individual fibers, and woven into an eight harness satin weave (8HSW) cloth. The composite panel used in this study contained 12 plies. The matrix consisted of a porous alumina-silica (AS) matrix. Fiber volume fraction was 33%. Extensive microcracking was present throughout the matrix as a result of the shrinkage which occurred during the pyrolysis processing (Fig. 1). These microcracks are distributed throughout the interior matrix as well as on the specimen surface. The resulting composite contains sintered matrix which is bonded to the fibers with no naturally occurring or engineered interphase. Further details of the composite processing and microstructure are discussed in [4,5,9]. All mechanical testing was conducted on single edge notched specimens [13] in lab air, using a servo-con￾trolled, hydraulic, horizontal test system [14,15]. The specimen ends were rigidly clamped using friction grips, thus resulting in rotationally constrained end conditions (Fig. 2). The fiber orientation relative to the loading axis was [0
/90
] for all edge notched speci￾mens. During the room temperature tests, crack mouth opening displacement (CMOD) was measured using a high resolution, knife edge extensometer. At 950
C a high temperature extensometer, with quartz or alumina rods, was used to measure CMOD. The extensometer Fig. 1. Nextel610/AS composite polished cross section optical micrograph. Fig. 2. Schematic of (a) single edge notched specimen geometry. For specimens tested at 23
C, W=12.6 mm, and at 950
C, W=25.4 mm. For all specimens, B=2.9 mm and H/W=4. (b) Strain gage locations for edge notched fracture tests. The lines within the gages indicate the direction of strain measurement. 1562 V.A. Kramb et al. / Composites Science and Technology 61 (2001) 1561–1570