No abstract

In many structural vibration control applications, strain sensors play a key role in the design and implementation of the vibration controller. Different types of sensors are commercially available, among which is the poled polyvinylidene difluoride (PVDF), an attractive sensor for large bandwidths and low costs. Despite such attractive features, PVDF-based sensors have limited use due to their low efficiency (mechanical energy to electrical energy conversion factor). To remedy this, nanocrystals and nanostructures have been recently cited as candidate materials that can be engineered to exhibit enhanced or entirely new properties for use in different applications. Particularly, carbon nanotubes (CNTs) have raised considerable interest in the scientific community due to their size and wide range of outstanding material properties. Given the moduli and strength values of CNTs, they are ideal filler materials for high performance (polymer) composite materials with unbeatable modulus-to-weight and strength-toweight ratios-the attributes that are essential for structural vibration control of a wide variety of industrial equipment and systems. Along this line of reasoning, this paper undertakes the development and implementation of a novel sensor paradigm based on proper fusion of CNTs with PVDF materials.

In this paper, the strength and damping properties of carbon nanotube-epoxy composites are examined. Carbon nanotubes (Single-walled and Multi-walled) were grown on stainless steel substrates using thermal chemical vapor deposition process. The nanotube-epoxy composites were then prepared by applying a layer of epoxy on the grown nanotubes and a PZT actuator was attached on this layer. The composite beam consisting of steel, nanotube-epoxy layer and PZT actuator was used as a cantilever beam for vibration experiments in order to determine the enhancement in strength and damping properties of the nanotube-epoxy layer. Several different samples were prepared for this purpose. Impulse and frequency sweep tests were conducted on these beams to obtain the impulse response and frequency response functions. Fast Fourier Transform of the impulse response was used to find the natural frequency of the composite beam. It was observed that there was an increase in the stiffness by using multi-walled nanotubes in the epoxy, while the damping ratio increased by using single-walled nanotubes. The stick-slip mechanism is discussed in order to explain the results obtained.