Development of lunar ceramic composites, testing and constitutive modeling, including cemented sand.

Abstract

The behavior of Intermediate Ceramic Composite (ICC) is examined experimentally and theoretically in this study. The fabrication procedures, developed molding methods, constitutive modelling of stress-strain-volumetric strain response and relationships between stress and ultrasonic velocity based disturbances as well as crack density are described in this dissertation. The first segment of the investigation involves new molding methods, development of tension testing setup, uniaxial compression and tension testing of ICC. Results showed that strength and ductility can be improved significantly by applying fibers. The second portion of the study proposes a unified constitutive modelling approach called the disturbed state concept (DSC) is extended for brittle materials both in tension and compression, based on the idea that the observed response of the material can be defined using the disturbance function, on the basis of the responses of the material parts in the relative intact (RT) and fully adjusted (FA) states that compose the material at any stage during deformation. Various aspects of the DSC are verified here with respect to laboratory behavior of two materials, a ceramic composite and a cemented sand. The new features in this investigation that (1) the constitutive behavior and parameters can be obtained from stress-strain-volume change behavior, and from ultrasonic P-wave velocity measurements, (2) correlation between mechanical and ultrasonic response can be developed, (3) the concept can provide a description of the crack density, (4) the model can give relationship between crack density and stress state, (5) the simplified version of the model can predict remaining life and load carrying capacity of materials through the proposed constitutive model.