Dynamic failure of ceramics under multiaxial compression
- California Institute of Technology, Pasadena, CA (United States)
Since ceramics and their composites are being increasingly used in structural applications, it is necessary to develop constitutive models to characterize their mechanical behavior and failure modes under multiaxial loading conditions. In brittle materials, the failure strength in compression has been predicted to increase under even moderate amounts of confinement. A new experimental technique has been developed whereby ceramic materials can be subjected to controlled multiaxial compressive loading. The main objective of this research is a systematic characterization of the mechanical behavior of ceramics under static and dynamic multiaxial compression. In addition, the effect of superposed confinement on the dynamic failure strength and failure mode is established. The experimental setup consists of a split Hopkinson (Kolsky) pressure bar (SHPB) which is modified to have single loading capability. Confined hard ceramic platens are placed at the specimen/bar interfaces. The specimen has a cylindrical geometry and is surrounded by a shrink-fit metal sleeve. The SHPB is used for generating uniaxial compressive pulses of known duration, shape and amplitude. Radial confinement is provided by the pressure from the shrink-fit sleeve. The confining pressure can be varied by changing the sleeve wall thickness and material. To study failure mode transition in engineering ceramics, experiments at different strain rates and differing amounts of confinement are performed on a sintered aluminum nitride (A1N) and a model ceramic material, Macor. The failure mode of the ceramic specimens changes from complete fragmentation by axial splitting with no confinement to localized deformation on faults with moderate confinement. Under both quasi-static and dynamic loading conditions, the axial compressive strength of the specimen material increases as lateral confinement is increased. A failure criterion is proposed based on the experimental results.
- OSTI ID:
- 175193
- Report Number(s):
- CONF-950686--
- Country of Publication:
- United States
- Language:
- English
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