Papers by Author: Mark J. Schulz

Abstract: Carbon nanotube spun threads are becoming growingly important for various technological and medical applications. Threads can be spun directly from carbon nanotube arrays using age old method of spinning. The process involves two rotations about two mutually perpendicular axes viz. spinning nanotubes into thread from array and winding the spun thread on spool. It is found that an array with properties of high uniform density, low amorphous carbon content and highly aligned nano-tubes are better spinnable. Piezoresistive property of spun thread is investigated through experiments. The change in resistivity of spun carbon nanotube thread with change in load will enable its use as force sensors. In a structural neural network system a network of sensors can pinpoint the location of damage in structure. If such network can be made of very small dimension it can detect crack initiation and crack propagation. Linearity of resistivity increase with increase in strain is observed for fine spun carbon nanotube threads. Upon unloading also this linearity is preserved with same slope.

Abstract: This study introduces a nano smart material to develop a novel sensor for Structural Health Monitoring (SHM) of mechanical and civil systems. Mechanical, civil, and environmental systems need to become self-sensing and intelligent to preserve their integrity, optimize their performance, and provide continuous safety for the users and operators. Present smart materials and structures have fundamental limitations in their sensitivity, size, cost, ruggedness, and weight. Smart materials developed using nanotechnology have the potential to improve the way we generate and measure motion in devices from the nano to the macro scale in size. Among several possible smart nanoscale materials, Carbon Nanotubes (CNT) have aroused great interest in the research community because of their remarkable mechanical, electrochemical, piezoresistive, and other physical properties. To address the need for new intelligent sensing based on CNT, this study presents piezoresistivity and electrochemical properties and preliminary experiments that can be applied for SHM. This study is anticipated to develop a new multifunctional sensor which can simultaneously monitor strain, stress and corrosion on a structure with a simple electric circuit.

Abstract: To address the need for new smart materials, this paper explores the use of carbon nanotubes to develop a nanocomposite smart material having electrochemical impedance properties for sensing and actuation. Fabrication and characterization of the carbon nanocomposite material are discussed in the paper. The issues related to hurdles in the practical manufacturing of commodity level macro size nanocomposite smart materials with prescribed electrical and electrochemical properties are also discussed.

Abstract: This paper experimentally investigates the power generation property of carbon nanotubes in an aqueous environment. Carbon nanotube based films are investigated in this paper as a new method for power generation based on ionic conductivity of the fluid. It is demonstrated that a carbon nanotube film that is bonded onto a structure vibrating with an electrolyte on the surface produces an alternating current without a net fluid flow. The power produced is smaller than for a piezoelectric material of the same size, but the CNT power generator is lightweight and has no moving parts, and does not require the structure to be immersed in an electrolyte. There are various possible applications for nanotube power generators.

Abstract: This paper introduces a new sensor design based on a carbon nanotube structural neuron for structural health monitoring applications. The carbon nanotube neuron is a thin and narrow polymer film sensor that is bonded or deposited onto a structure. The electrochemical impedance (resistance and capacitance) of the neuron changes due to deterioration of the structure where the neuron is located. A network of the long carbon nanotube neurons can form a structural neural system to provide large area coverage and an assurance of the operational health of a structure without the need for actuators and complex wave propagation analyses that are used with other SHM methods. The neural system can also reduce the cost of health monitoring by using biomimetic signal processing to minimize the number of channels of data acquisition needed to detect damage. The carbon nanotube neuron is lightweight and easily applied to the structural surface, and there is no stress concentration, no piezoelectrics, no amplifier, and no storage of high frequency waveforms. The carbon nanotube neuron is expected to find applications in detecting damage and corrosion in large complex structures including composite and metallic aircraft and rotorcraft, bridges, and almost any type of structure with almost no penalty to the structure.