An investigation of the nature of microstructural damage in a filled elastomeric compostie material

Abstract

Elastomeric composite materials have been of interest for some time. With the advent of solid rocket propellants, however, a critical need has developed for the evaluation of those mechanical properties needed for structural analysis and failure prediction. It is well-known that the mechanical response and failure characteristics of composite propellants are related to the formation and growth of vacuoles within the material (microstructural damage) and that these same vacuoles cause the material to dilate with strain (stain-dilatation). The principal objectives of this dissertation were to define those elements which are the most influential in determining the extent of microstructural damage and to develop the apparatus and techniques necessary to measure those elements accurately and directly. Because of the direct relationship between microstructural damage and dilatation, those elements which determine the extent of dilatation are the same ones which determine the extent of microstructural damage. An expression for dilatation as a function of strain based on a generalized model of the process of dewetting and vacuole growth was derived. From this expression, it was determined that the two elements most influential in determining the extent of microstructural damage are the dewetting distribution function (the fraction of the total possible number of vacuoles which exist at any given strain) and the rate at which individual vacuoles grow with strain. ...