Mechanical property characterization of multidirectional Si{sub 3}N{sub 4}/BN fibrous monoliths.
Fibrous monoliths (FMs) of Si{sub 3}N{sub 4}/BN ({approx}85 vol% Si{sub 3}N{sub 4}/15 vol% BN) with three different cell architectures (unidirectional, 0{degree}/90{degree}, and {+-}45{degree}) were tested in four-point-bend mode under ambient conditions. The FM constituents (hot-pressed monolithic Si{sub 3}N{sub 4} and BN) were also characterized. The unidirectional Si{sub 3}N{sub 4}/BN FM demonstrated the best properties, with ultimate strength of 476 {+-} 30 MPa and work-of-fracture of 12.6 {+-} 1.9 kJ/m{sup 2}, while Si{sub 3}N{sub 4}/BN FM with {+-}45{degree} cell architecture had the lowest strength (175 {+-} 13 MPa) and work-of-fracture (2.7 {+-} 1.7 kJ/m{sup 2}). The 0{degree}/90{degree} FM had intermediate values of 379 {+-} 86 MPa and 4.9 {+-} 2.2 kJ/m{sup 2}. High work-of-fracture for the unidirectional Si{sub 3}N{sub 4}/BN was correlated to toughening mechanisms such as extensive delamination and crack deflection. Predictions for the elastic moduli of the Si{sub 3}N{sub 4}/BN FMs based on laminate theory correlated well with the observed elastic moduli for the unidirectional and 0{degree}/90{degree} Si{sub 3}N{sub 4}/BN FMs. However, large discrepancies were observed between predictions and observed values for the {+-}45{degree} Si{sub 3}N{sub 4}/BN FMs, possibly due to the increasing role of the BN phase on mechanical properties in these FMs. Mechanical properties of monolithic Si{sub 3}N{sub 4} and BN compared well with literature values.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 11174
- Report Number(s):
- ANL/ET/CP-97896
- Country of Publication:
- United States
- Language:
- English
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