Author

Nengda Jiang

Date of Award

8-2018

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Graduate Studies

Committee Chair

Dr. Sirish Namilae

First Committee Member

Dr. Daewon Kim

Second Committee Member

Dr. Yi Zhao

Third Committee Member

Dr. Mandar Kulkarni

Abstract

Silicone based biofidelic surrogates are being used in many biomedical applications; e.g. to understand the body injury mechanisms, evaluate protective equipment like helmets and armors. Apart from matching the mechanical behavior of bodily tissues, there is an increasing requirement for these materials to be electrically conductive and piezoresistive to facilitate direct instrumentation. Carbon nanotubes (CNTs) are a possible filler to impart electrical conductivity and piezoresistivity to silicone biofidelic materials. A sandwich structure of silicone and CNT sheet, comprising two dielectric facesheets and a highly conductive core layer has added advantages of raising the dielectric permittivity and suppressing dielectric loss.

In this thesis, a fabrication methodology was developed for a proprietary blend of two-part silicone/CNT sheet sandwich composite with biofidelic mechanical properties corresponding to that of white matter of human brain tissue. The mechanical and electromechanical behavior of these sandwich composites was characterized using resistivity measurements, tensile tests and dynamic mechanical analysis (DMA). The composition of the two-part silicone in this composite was varied to obtain electrical conductivity and piezoresistivity while retaining the mechanical properties of the white matter. Interestingly, the mechanical and electromechanical performance of the composite varied between first loading and subsequent loadings during the testing. The effect of a second filler addition: graphite platelets (GP) on the properties of silicone nanocomposite was also investigated. The experimental observations were analyzed using simple mechanical models and scanning electron microscope (SEM) micrographs to explain the findings. The results indicate potential for using this biofidelic silicone/CNT sheet sandwich composite with electrical conductivity and piezoresistivity for biomedical applications (e.g. traumatic brain injury simulation) without deploying external strain sensors.

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