Fracture toughness and R-curve behavior of laminated brittle-matrix composites
- Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering
- Univ. of California, Berkeley, CA (United States)
The fracture toughness and resistance-curve behavior of relatively coarse-scale, niobium/niobium aluminide (Nb/Nb{sub 3}Al) laminated composites have been examined and compared to other Nb/Nb{sub 3}Al composites with (in situ) Nb particulate or microlaminate reinforcements. The addition of high aspect-ratio Nb reinforcements, in the form of 20 vol. pct of 50- to 250-{micro}m-thick layers, was seen to improve the toughness of the Nb{sub 3}Al intermetallic matrix by well over an order of magnitude, with the toughness increasing with Nb layer thickness. The orientation of the laminate had a small effect on crack-growth resistance with optimal properties being found in the crack arrester, as compared to the crack divider, orientation. The high fracture toughness of these laminates was primarily attributed to large ({approximately}1- to 6-mm) crack-bridging zones formed by intact Nb layers in the crack wake; these zones were of sufficient size that large-scale bridging (LSB) conditions generally prevailed in the samples tested. Resistance-curve modeling using weight function methods permitted the determination of simple approximations for the bridging tractions, which were then used to make small-scale bridging (SSB) predictions for the steady-state toughness of each laminate.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 669742
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 29, Issue 10; Other Information: PBD: Oct 1998
- Country of Publication:
- United States
- Language:
- English
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