Micromechanical and fracture characteristics of metal -ceramic composites
Abstract
The micromechanical and fracture characteristics of various metal-ceramic composites were investigated. The effect of microstructure was incorporated in analyzing the behavior of these composites. The parameters whose effects were systematically investigated included metal-ceramic volume fraction, grain/particle size, and the contiguity and architecture of various phases. First, elastic properties of these composites were studied by obtaining elastic and shear moduli with the help of ultrasonic sensors. It was found that volume fraction was the dominant parameter that influences the elastic behavior. The other parameters like contiguity; grain size etc., do not significantly affect the elastic properties. Quasi-Static compression tests were performed to study the overall stress-strain behavior. It was found that the composites deform plastically after a certain stress level. The extent of yielding and nature of strain hardening was found to be a function of other microstructural parameters like contiguity and residual stresses besides the volume fraction. A two-layer model was developed and successfully implemented to predict the elastic-plastic behavior of these composites. In order to measure the magnitude of residual stresses; neutron diffraction experiments were performed. It was found that the magnitude of hydrostatic stresses was significantly high; well beyond the tensile yield point in case of metals. To investigate fracture mechanisms and crack propagation, three point bend tests were performed on SENB specimens inside the environmental SEM chamber. Video films and stills of crack-growth inside these composites were recorded. The failure mechanisms were explained in terms of the interfacial strength, residual stresses and yielding inside the metal phase. Finite element simulations were utilized to explain the fracture behavior and crack propagation.
Degree
Ph.D.
Advisors
Sun, Purdue University.
Subject Area
Mechanics|Materials science
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