Date of Award

8-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Materials Science

Advisor

Kornev, Konstantin

Committee Member

Blouin , Vincent

Committee Member

Dean , Delphine

Committee Member

Luo , Jian

Abstract

Current advances in the manufacture of nanoporous and nanofibrous materials with high absorption capacity open up new opportunities for the development of fiber-based probes and sensors. Pore structures of these materials can be designed to provide high suction pressure and fast wicking. During wicking, due to the strong capillary action, the liquids exert stresses on the fiber network, thus the stressed state of dry and wet parts of the material differs. In this work the effect of stress reduction in fibrous materials due to the presence of wetting liquid in the pore structure is studied in details for both static and dynamic cases. It is suggested that this effect can be used for liquid monitoring and the examples of one and two dimensional probes are provided.
To open a discussion an illustrative example of a single capillary is considered and the effect of a moving meniscus on the stress distribution along capillary walls is demonstrated. Then the similar effects are analyzed in yarns and fabrics. A yarn that can capture an aerosol droplet is considered as a promising sensing element that could monitor the stresses caused by wetting fronts. It is shown that the stress transfer between dry and wet parts of the yarn upon liquid wicking significantly depends on the boundary conditions. The stress distribution in the yarn with clamped ends is discussed. The elasto-capillary problem is resolved for 2D case of a freely suspended self-reconfigurable material. It is shown that the classical Bernoulli problem of a freely suspended fabric can be used for the analysis of stresses in the fibrous matrix.
The theoretical conclusions on elasto-capillarity are supported by experimental results on tensile testing of fibrous materials. The results show that the elasto-capillary effect is pronounced in the porous samples with the pore sizes smaller than 10 microns.

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