Effect of frequency and environment on fatigue behavior of a CVI SiC/SiC ceramic matrix composite at 1200 °C

• Published in: Composites science and technology Vol. 71; no. 2; pp. 190 - 196
• Main Authors: Ruggles-Wrenn, M.B., Christensen, D.T., Chamberlain, A.L., Lane, J.E., Cook, T.S.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2011; Elsevier
• Subjects: A. Ceramic–matrix composites (CMCs); B. Fatigue; B. High-temperature properties; B. Mechanical properties; Cross-disciplinary physics: materials science; rheology; D. Fractography; Exact sciences and technology; Materials science; Other materials; Physics; Specific materials; B. Mechanical properties; A. Ceramic–matrix composites (CMCs); B. Fatigue; D. Fractography; B. High-temperature properties; Ceramic matrix composite; Fatigue life; A. Ceramic-matrix composites (CMCs); Fiber reinforced material; Boron nitride; Mechanical properties; Experimental study; Mineral fiber; Stress-strain relations; Laminates; Frequency effect; Non oxide ceramics; Silicon carbide; Composite materials; Temperature effects; Fatigue strength; Woven material; Fracture mode; Tensile properties; Ceramic fiber
• ISSN: 0266-3538; 1879-1050
• DOI: 10.1016/j.compscitech.2010.11.008

The fatigue behavior of a SiC/SiC CMC (ceramic matrix composite) was investigated at 1200 °C in laboratory air and in steam environment. The composite consists of a SiC matrix reinforced with laminated woven Hi-Nicalon™ fibers. Fiber preforms had boron nitride fiber coating applied and were then densified with CVI SiC. Tensile stress–strain behavior and tensile properties were evaluated at 1200 °C. Tension–tension fatigue tests were conducted at frequencies of 0.1, 1.0, and 10 Hz for fatigue stresses ranging from 80 to 120 MPa in air and from 60 to 110 MPa in steam. Fatigue run-out was defined as 10 5 cycles at the frequency of 0.1 Hz and as 2 × 10 5 cycles at the frequencies of 1.0 and 10 Hz. Presence of steam significantly degraded the fatigue performance. In both test environments the fatigue limit and fatigue lifetime decreased with increasing frequency. Specimens that achieved run-out were subjected to tensile tests to failure to characterize the retained tensile properties. The material retained 100% of its tensile strength, yet modulus loss up to 22% was observed. Composite microstructure, as well as damage and failure mechanisms were investigated.