Date of Award

12-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Materials Science and Engineering

Advisor

Rao, Apparao M

Committee Member

Skove , Malcolm J

Committee Member

Kornev , Konstantin

Committee Member

Luzinov , Igor

Committee Member

Luo , Jian

Abstract

The modulus of elasticity of a homogeneous body is the same for all directions. No known crystalline materials have a Young's modulus that is the same in all directions. The linear theory of elasticity states that strain is proportional to stress so that a straight line is obtained in a stress versus strain plot. As long as the forces applied to the body are proportional, the body behaves perfectly elastically, obeying Hooke's law. At high enough strains, however, deviations from Hooke's law will occur. Nonlinear elasticity is generally apparent when large deformations are applied and usually when the sample size is on the micro/nano scale. The nonlinear theory of elasticity of materials is more complex and leads to the introduction of higher-order elastic constants. These higher-order constants confer increased accuracy to theoretical predictions of the elastic behavior of the material. Here, equipment specifically designed for the tensile measurements of individual micro/nano-composite fibers will be introduced. The results obtained for the elastic properties of single filaments of IM7 carbon fibers, which include the usual second-order as well as the third-order elastic constants, and the piezoresistivity will be presented.

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