Oxidation Embrittlement Probe for Ceramic‐Matrix Composites

Abstract

A test method for probing oxidation embrittlement in ceramic-matrix composites has been devised and demonstrated for three composites: SiC/magnesium aluminosilite, SiC/SiC, and SiC/AI,O,. The method identifies a "pest" temperature TP. The growth of an embrittled region from the surface, at Tp, has been illustrated. The embrittlement mechanism involves oxygen ingress through matrix cracks and silicate formation at the fibers, causing fiber failure. 2097

Fatigue Behavior of Ceramic Matrix Composite Oxidized at Intermediate Temperatures

“…The average diameter and tensile strength of fibers were about 12 mm and 3.0 GPa, respectively. Each bundle consisted of 500 fibers with a density of 3.10 g/cm 3 . The bulk density of the composite was 2.3 g/cm 3 .…”

“…Each bundle consisted of 500 fibers with a density of 3.10 g/cm 3 . The bulk density of the composite was 2.3 g/cm 3 . The specimens for fatigue tests are 3 mm in thickness and 4 mm in width and 36 mm in length.…”

“…The oxidation embrittlement at intermediate temperatures is called ''pest'' phenomenon since tensile strength and creep life are markedly decreased. 2,3) After the carbon interphase is oxidized, the fibers and matrix in SiC fiber reinforced SiC matrix composite (SiC/SiC) locally react with oxygen and therefore their bonding becomes strong with the formation of silica. 4,5) A modified SiC/SiC is fabricated by adding glassy phases in the matrix, which is called the enhanced SiC/SiC.…”

Creep behavior in interlaminar shear of a Hi-NicalonTM/ SiC-B4C composite at 1200∘C in air and in steam

“…Since their constituents are intrinsically oxidation-prone, oxidation embrittlement is the most significant problem hindering SiC/SiC composites [5]. Typically the embrittlement occurs once oxygen enters through the matrix cracks and reacts with the fibers and the fiber coatings [6][7][8]. The degradation of fibers and fiber coatings is generally accelerated in the presence of moisture [9].…”

Stress-Rupture and Stress-Relaxation of Sic\Sic Composites at Intermediate Temperature

“…Therefore, the extent of oxidation from the edge of the fracture surface inwards was determined by the presence of oxidation at the fiber/matrix interphases using a field emission scanning electron microscope. Usually the oxidation region formed a "picture frame" [2] around the unembrittled region. Figure 8 shows the depth of oxidation into the specimen as a function of time at temperature.…”