Date of Award

2015

Document Type

Open Access Thesis

Department

Mechanical Engineering

First Advisor

Kenneth L. Reifsnider

Abstract

The long-term properties of continuous fiber reinforced composite materials are increasingly important as applications in airplanes, cars, and other safety critical structures are growing rapidly. The mechanical, electrical, and thermal properties of composite materials are altered by the initiation and accumulation of discrete fracture events whose distribution and eventual interaction defines the limits of design, such as strength and life. There is a correlation that exists between the long term behavior of those materials under combined mechanical, thermal, and electrical fields, and the functional properties and characteristics of the composite materials that requires a fundamental understanding of the material state changes caused by deformation and damage accumulation. While a strong foundation of understanding has been established for damage initiation and accumulation during the life of composite materials and structures, an understanding of the nature and details that define fracture path development at the end of life has not been established. This present research reports a multiphysics study of that progression, which is focused on measured and predicted changes in through-thickness electric/dielectric response of polymer based composites. Experimental data are compared to simulations of micro-defect interactions and changes in electrical and mechanical properties. Applications of the concepts to prognosis of behavior are discussed.

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