Ceramic composites: Roles of fiber and interface
- Argonne National Lab., IL (United States). Energy Technology Div.
Results are presented that elucidate (a) the effects of fiber coating on retained fiber strength and mechanical properties of Nicalon-fiber-reinforced SiC matrix composites, and (b) the role of residual stresses in the interfacial bond strength of SiC-fiber-reinforced reaction-bonded Si{sub 3}N{sub 4} matrix composites. For Nicalon-fiber-reinforced SiC matrix composites that were fractured in a flexural mode, retained in-situ fiber strength, ultimate strength, and work-of-fracture (WOF) of the composites increased with increasing thickness of the fiber coating and reached maximum values at a coating thickness of {approx} 0.3 {micro}m. A direct correlation between the variation of in-situ fiber strength and the variation of ultimate strength and WOF of the composites clearly indicates the critical role of the retained in-situ strength of reinforcing fibers in composites. Fiber pushout tests performed on SiC-fiber-reinforced reaction-bonded Si{sub 3}N{sub 4} matrix composites indicate that both debonding and frictional shear stresses decreased with increasing fiber content. These variations are consistent with the variation of residual radial stress on fibers, as measured by neutron diffraction, i.e., residual stresses decreased with increasing fiber content. Because fracture behavior is strongly controlled by interfacial bond strength, which is proportional to the residual radial stress, appropriate control of residual stress is critical in the design of composites with desired fracture properties.
- Research Organization:
- Argonne National Lab., IL (United States)
- Sponsoring Organization:
- USDOE Assistant Secretary for Fossil Energy, Washington, DC (United States)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 554777
- Report Number(s):
- ANL/ET/CP--94259; CONF-9710120--; ON: DE98050332
- Country of Publication:
- United States
- Language:
- English
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