| Acquisition of a Nanoindenter for Research on Small-Scale Materials and Structures |
AUG 2003 |
6 pages |
| Authors:
Frank W. Zok; D. R. Clarke; N. C. MacDonald; Kimberly L. Turner; CALIFORNIA UNIV SANTA BARBARA DEPT OF MECHANICAL AND ENVIRONMENTAL ENGINEERING
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 | The first project is "Matrix Enabled Damage Tolerance in Oxide Continuous Fiber Reinforced Ceramic Composites", PIs: Frank Zok, Carlos Levi and Robert McMeeking, funded by AFOSR. Here, the nanoindenter is being used for measuring the mechanical properties of fiber-matrix interfaces, through the so- called "fiber push-in" test. In essence, the test involves pushing an individual fiber past the surrounding matrix while simultaneously measuring the sliding displacement at the fiber/matrix interface. ... |
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| The Role of Microstructural Damage in the Thermal Diffusivity of Fiber- Reinforced Ceramic-Matrix Composites |
14 MAY 1999 |
105 pages |
| Authors:
Frank W. Zok; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
|
| A phase-sensitive photothermal technique for the determination of the thermal diffusivity of solids and the thermal, conductance of cracks and interfaces has been developed. The technique has been validated using a model systems comprising stainless steel disks, placed either in direct contact with each other or with thin polyethylene sheets between them. The corresponding heat flow analysis has also been developed. The technique has been used to study in detail ... |
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| Influence of Interparticle Forces on the Rheological Behavior of Pressure-Consolidated Alumina Particle Slurries |
94 |
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| Authors:
Bhaskar V. Velamakanni; Fred F. Lange; Frank W. Zok; Dale S. Pearson; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
|
 | The stress relaxation behavior of alumina powder compacts, consolidated from aqueous slurries by pressure filtration, is reported. The interparticle forces were controlled prior to consolidation by changing the pH from 3 to 9 and by adding different amounts of salt (0.1 to 2.0 M NH4Cl) to slurries maintained at pH 4. Disk-shaped bodies were rapidly compressed to an axial strain of 2%, and the resulting stress relaxation data were monitored ... |
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| Flexural Properties of Brittle Multilayer Materials: I, Modeling |
94 |
|
| Authors:
Craig A. Folsom; Frank W. Zok; Fred F. Lange; CALIFORNIA UNIV SANTA BARBARA COLL OF ENGINEERING
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| Multilayer systems comprising brittle materials can exhibit substantially different behaviors under flexural and tensile loadings. The present article addresses the origins of such differences, with emphasis on the modeling of the flexural stress-strain response. Systems with both a deterministic tensile strength and a distribution in strengths (characterized by Weibull statistics) are considered. The model predictions show that both the ultimate strength and strain-to-failure in flexure exceed the corresponding values in ... |
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| Fracture Resistance Characteristics of a Metal-Toughened Ceramic |
93 |
|
| Authors:
Brian D. Flinn; Calvin S. Lo; Frank W. Zok; Anthony G. Evans; CALIFORNIA UNIV SANTA BARBARA COLL OF ENGINEERING**
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| The fracture characteristics of an Al2O3/Al composite are examined. Measurements of resistance curves and work of rupture are compared with predictions of a micromechanical model, incorporating the effects of crack bridging by the Al reinforcements. The bridging traction law is assumed to follow linear softening behavior, characterized by a peak stress, sigma(sub c), and a critical stretch-to-failure, u(sub c). The values of sigma(sub c) and u(sub c) inferred from such ... |
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| Fiber-Reinforced Diamond Matrix Composites |
93 |
|
| Authors:
Michael D. Drory; Robert J. McClelland; Frank W. Zok; Fernando E. Heredia; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
|
| The feasibility of fiber-reinforced diamond matrix composites was examined. For this purpose, monofilament composite specimens were fabricated using SiC fibers. The diamond was deposited onto the fibers using plasma enhanced CVD. The mechanical properties of the composite were characterized using uniaxial tensile tests. The specimens exhibited multiple matrix cracking, followed by fiber fracture and fiber pullout. The measurements were used to obtain an estimate of the interface sliding stress and ... |
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| Damage and Failure in Unidirectional Ceramic-Matrix Composites |
92 |
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| Authors:
Douglas S. Beyerle; S. M. Spearing; Frank W. Zok; Anthony G. Evans; CALIFORNIA UNIV SANTA BARBARA COLL OF ENGINEERING**
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| A study of the mechanical characteristics of a unidirectional fiber reinforced calcium aluminosilicate matrix composite has been conducted. The properties have been related to the individual properties of the matrix, the fibers, and the interfaces, as well as the residual stress, using available models of matrix cracking and fiber fracture. Comparisons have been made with lithium aluminosilicate matrix composites. Predictions of initial matrix cracking and of ultimate strength using the ... |
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| Mechanical Behavior of a Laminar Ceramic/Fiber-Reinforced Epoxy Composite |
92 |
|
| Authors:
Craig A. Folsom; Frank W. Zok; Fred F. Lange; CALIFORNIA UNIV SANTA BARBARA COLL OF ENGINEERING**
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| The mechanical properties of a novel laminar composite are investigated. The composite consists of dense alumina sheets bonded between sheets of uniaxial carbon fiber reinforced epoxy tape. The behavior of the composite in both flexural and tensile loading is characterized and the results are related to the properties of the constituents. The role of the interlaminar interface in composite behavior is also examined. Implications for the design of laminar composites ... |
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| Fiber Bundle Pushout: A Technique for the Measurement of Interfacial Sliding Properties |
92 |
|
| Authors:
Thomas J. Mackin; Frank W. Zok; CALIFORNIA UNIV SANTA BARBARA COLL OF ENGINEERING**
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| An experimental technique for the measurement of interfacial sliding properties in fiber reinforced materials is presented. The technique involves pushing a bundle of fibers simultaneously through a thin section of the composite. Using this technique, sample averages are immediately available, eliminating the need for repeated single fiber tests. The technique is particularly useful for composites that contain small diameter fibers. Salient features of the technique are demonstrated through tests on ... |
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