High-Temperature Compressive Deformation of Si₃N₄/BN Fibrous Monoliths


Fibrous monolithic Si3N4/BN (≈85 vol.% Si3N4/15 vol.% BN) and monolithic Si3N4 ceramics were compressed at a nearly constant strain rate (ε) at 1200-1400 ⁰C in N2. The ε range was ≈1x10-6 to 5x10-6 s-1; the stress (σ) range was 37-202 MPa. The Si3N4 and the unidirectional fibrous monoliths that were oriented with the long axis of the Si3N4 cells parallel to the compression direction exhibited plasticity at 1300 and 1400 ⁰C, with ε∝σ. A 0/90⁰ cross-ply Si3N4/BN laminate also exhibited significant plasticity, but it was weaker than the above-mentioned ceramics. The unidirectional fibrous monoliths that were compressed perpendicular to the cell direction fractured at ≈50 MPa in all tests. A ±45⁰ laminate tested at 1300 ⁰C fractured at a stress of ≈40 MPa. Low fracture stress correlated with shear through BN layers.

Meeting Name

Proceedings of the 1999 23rd Annual Conference on Composites, Advanced Ceramics, Materials, and Structures (1999: Jan. 25-29, Cocoa Beach, FL)


Materials Science and Engineering

Keywords and Phrases

Boron compounds; Compressive stress; Crystal orientation; Deformation; Fracture testing; Laminates; Plasticity; Silicon nitride; Strain rate; Stress analysis; Boron nitride; Compressive deformation; Ceramic fibers

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Document Type

Article - Conference proceedings

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© 1999 American Ceramic Society (ACS), All rights reserved.

Publication Date

01 Jan 1999