Actuator Feasibility Study for Active Control of Ducted Axial Fan Noise

A feasibility study was performed to investigate actuator technology which is relevant for a particular application of active noise control for gas turbine stator vanes. This study investigated many different classes of actuators and ranked them on the order of applicability. The most difficult requirements the actuators had to meet were high frequency response, large amplitude deflections, and a thin profile. Based on this assessment, piezoelectric type actuators were selected as the most appropriate actuator class. Specifically, Rainbows (a new class of high performance piezoelectric actuators), and unimorphs (a ceramic/metal composite) appeared best suited to the requirements. A benchtop experimental study was conducted. The performance of a variety of different actuators was examined, including high polymer films, flextensional actuators, miniature speakers, unimorphs, and Rainbows. The displacement/frequency response and phase characteristics of the actuators were measured. Physical limitations of actuator operation were also examined. This report includes the first known, high displacement, dynamic data obtained for Rainbow actuators. A new "hard" ceramic Rainbow actuator which does not appear to be limited in operation by self heating as "soft" ceramic Rainbows was designed, constructed and tested. The study concludes that a suitable actuator for active noise control in gas turbine engines can be achieved with state of the art materials and processing

Piezoelectric Fibers for Sensing and Energy Generation

Au cours de la dernière décennie, la recherche et le développement de générateurs fibrés a reçu une attention significative en raison de la popularité grandissante des appareils électroniques que l’on peut porter, tels que les écrans sur vêtements, les dispositifs de réalité virtuelle, les senseurs médicaux/cliniques portables et les montres intelligentes. Parmi les générateurs fibrés, les fibres piézoélectriques qui opèrent en se basant sur l’effet piézoélectrique sont spécialement attrayantes, parce qu’elles peuvent convertir les vibrations mécaniques de la vie quotidienne (causées par exemple par la marche, les courants d’air ou les battements cardiaques) en signaux électriques. Pour augmenter le potentiel des technologies portables, des textiles piézoélectriques pour alimenter les dispositifs électroniques ont été fabriqués en intégrant les fibres piézoélectriques dans des fibres commerciales utilisant les techniques de fabrication conventionnelles. Les fibres piézoélectriques peuvent aussi avoir des applications techniques dans les domaines de l’information et des communications, dans l’automatisation industrielle, dans le diagnostic médical, dans le control du trafic et dans le secteur de la défense. Par exemple, ces fibres pourraient être implantées dans les avions et les véhicules pour surveiller l’intégrité de la structure mécanique, ainsi qu’alimenter les systèmes électroniques embarqués tels que les réseaux de senseurs sans-fil (WSN) à faible puissance. D’autres applications incluent les détecteurs acoustiques de haute-sensibilité pour la détection des ondes sonores, les actuateurs de micro-positionnement pour les microscopes à force atomique (AFM), les microscopes à effet tunnel (STM), les miroirs laser d’alignement et les dispositifs médicaux implantables (IMD). Encouragés par le marché sans cesse grandissant des appareils électroniques portatifs, des efforts substantiels ont été investis dans la fabrication de fibres piézoélectriques. Aujourd’hui, la plupart des fibres piézoélectriques existantes sont fabriquées soit en faisant croître des nanostructures piézoélectriques dans un filament conducteur ou en extrudant des polymères piézoélectriques avec des polymères conducteurs par trempe sur roue (melt-spinning). La performance et les applications de ces fibres piézoélectriques sont limitées par leur géométries simpliste, leur grandes taille, leur faible fiabilité mécanique, leur coût élevé et leur faible réponse piézoélectrique. Cette thèse a pour objectif de démontrer des fibres piézoélectriques micro et nanostructurées pouvant répondre à ces limitations.----------Abstract In the past decade, the R&D (research and development) of fiber generators has received significant attention due to the growing popularity of wearable mobile electronic systems such as on-garment displays, virtual-reality devices, wearable medical/clinic sensors and smart watches. Among all of these fiber generators, piezoelectric fibers that operate based on piezoelectric effect are especially attractive, because they could convert mechanical vibrations accessible in our daily life (i.e. walking, air flow and heart beating) into electrical signals. To make further improvements to the wearable applications, piezoelectric textiles that power on-body electronics have been fabricated by integrating piezoelectric fibers into commercial fabrics using traditional textile fabrication techniques. Piezoelectric fibers can also find technical applications in the fields of information and communication, industrial automation, medical diagnostics, automation and traffic control, and in the defense industries. For instance, piezoelectric fibers could be implanted on the airplanes and vehicles, for the purpose of structural integrity monitoring, as well as powering the on-board electronic systems such as wireless sensor networks (WSNs) with low-power consumption. Other common examples include ultrasensitive sound detectors for stand-off sound detection, micro-positioning actuators for atomic force microscopes (AFM), scanning tunneling microscopes (STM), and laser mirror alignment; as well as power sources for implanted medical devices (IMDs). Driven by the ever-growing market, extensive effort has been put into the fabrication of piezoelectric fibers. Currently, most of the existing piezoelectric fibers are fabricated either by growing piezoelectric nanostructures along a conductive filament or by extruding piezoelectric polymers together with a conductive polymer by melt-spinning. The performance and applications of these piezoelectric fibers are limited by their simple fiber geometries, large fiber size, poor mechanical reliability, high-cost, and low piezoelectric response. This thesis aims to demonstrate micro- and nanostructured piezoelectric fibers that address these limitations. In our approach, kilometer-long piezoelectric fibers of sub-millimeter diameters are thermally drawn from a macroscopic preform. The piezoelectric fibers feature a soft hollow polycarbonate core surrounded with a spiral multilayer cladding consisting of alternating layers of piezoelectric electrospun nanocomposites (polyvinylidene enhanced with BTO, PZT or CNT)and conductive polymer (carbon filled polyethylene)

Performance of Smart Materials-Based Instrumentation for Force Measurements in Biomedical Applications: A Methodological Review

The introduction of smart materials will become increasingly relevant as biomedical technologies progress. Smart materials sense and respond to external stimuli (e.g., chemical, electrical, mechanical, or magnetic signals) or environmental circumstances (e.g., temperature, illuminance, acidity, or humidity), and provide versatile platforms for studying various biological processes because of the numerous analogies between smart materials and biological systems. Several applications based on this class of materials are being developed using different sensing principles and fabrication technologies. In the biomedical field, force sensors are used to characterize tissues and cells, as feedback to develop smart surgical instruments in order to carry out minimally invasive surgery. In this regard, the present work provides an overview of the recent scientific literature regarding the developments in force measurement methods for biomedical applications involving smart materials. In particular, performance evaluation of the main methods proposed in the literature is reviewed on the basis of their results and applications, focusing on their metrological characteristics, such as measuring range, linearity, and measurement accuracy. Classification of smart materials-based force measurement methods is proposed according to their potential applications, highlighting advantages and disadvantages

2nd International Conference on Nanomaterials Science and Mechanical Engineering: book of abstracts

2nd International Conference on Nanomaterials Science and Mechanical Engineering: book of abstracts - University of Aveiro, Portugal July 9-12, 2019.publishe

A microgripper for single cell manipulation

This thesis presents the development of an electrothermally actuated microgripper for the manipulation of cells and other biological particles. The microgripper has been fabricated using a combination of surface and bulk micromachining techniques in a three mask process. All of the fabrication details have been chosen to enable a tri-layer, polymer (SU8) - metal (Au) - polymer (SU8), membrane to be released from the substrate stress free and without the need for sacrificial layers. An actuator design, which completely eliminates the parasitic resistance of the cold arm, is presented. When compared to standard U-shaped actuators, it improves the thermal efficiency threefold. This enables larger displacements at lower voltages and temperatures. The microgripper is demonstrated in three different configurations: normally open mode, normally closed mode, and normally open/closed mode. It has-been modelled using two coupled analytical models - electrothermal and thermomechanical - which have been custom developed for this application. Unlike previously reported models, the electrothermal model presented here includes the heat exchange between hot and cold arms of the actuators that are separated by a small air gap. A detailed electrothermomechanical characterisation of selected devices has permitted the validation of the models (also performed using finite element analysis) and the assessment of device performance. The device testing includes electrical, deflection, and temperature measurements using infrared (IR) thermography, its use in polymeric actuators reported here for the first time. Successful manipulation experiments have been conducted in both air and liquid environments. Manipulation of live cells (mice oocytes) in a standard biomanipulation station has validated the microgripper as a complementary and unique tool for the single cell experiments that are to be conducted by future generations of biologists in the areas of human reproduction and stem cell research

Processing, Characterization And Performance Of Carbon Nanopaper Based Multifunctional Nanocomposites

Carbon nanofibers (CNFs) used as nano-scale reinforcement have been extensively studied since they are capable of improving the physical and mechanical properties of conventional fiber reinforced polymer composites. However, the properties of CNFs are far away from being fully utilized in the composites due to processing challenges including the dispersion of CNFs and the viscosity increase of polymer matrix. To overcome these issues, a unique approach was developed by making carbon nanopaper sheet through the filtration of well-dispersed carbon nanofibers under controlled processing conditions, and integrating carbon nanopaper sheets into composite laminates using autoclave process and resin transfer molding (RTM). This research aims to fundamentally study the processing-structure-property-performance relationship of carbon nanopaper-based nanocomposites multifunctional applications: a) Vibrational damping. Carbon nanofibers with extremely high aspect ratios and low density present an ideal candidate as vibrational damping material; specifically, the large specific area and aspect ratio of carbon nanofibers promote significant interfacial friction between carbon nanofiber and polymer matrix, causing higher energy dissipation in the matrix. Polymer composites with the reinforcement of carbon nanofibers in the form of a paper sheet have shown significant vibration damping improvement with a damping ratio increase of 300% in the nanocomposites. b) Wear resistance. In response to the iv observed increase in toughness of the nanocomposites, tribological properties of the nanocomposite coated with carbon nanofiber/ceramic particles hybrid paper have been studied. Due to high strength and toughness, carbon nanofibers can act as microcrack reducer; additionally, the composites coated with such hybrid nanopaper of carbon nanofiber and ceramic particles shown an improvement of reducing coefficient of friction (COF) and wear rate. c) High electrical conductivity. A highly conductive coating material was developed and applied on the surface of the composites for the electromagnetic interference shielding and lightning strike protection. To increase the conductivity of the carbon nanofiber paper, carbon nanofibers were modified with nickel nanostrands. d) Electrical actuation of SMP composites. Compared with other methods of SMP actuation, the use of electricity to induce the shape-memory effect of SMP is desirable due to the controllability and effectiveness. The electrical conductivity of carbon fiber reinforced SMP composites can be significantly improved by incorporating CNFs and CNF paper into them. A vision-based system was designed to control the deflection angle of SMP composites to desired values. The funding support from National Science Foundation and FAA Center of Excellence for Commercial Space Transportation (FAA COE CST) is acknowledged

ฟิล์มบางที่มีการจัดตัวสูงและฟิล์มบางพรุนของ Pb(ZrxTi1-x)O3

Thesis (Ph.D., Physics)--Prince of Songkla University, 200

Review and Perspectives: Shape Memory Alloy Composite Systems

Following their discovery in the early 60's, there has been a continuous quest for ways to take advantage of the extraordinary properties of shape memory alloys (SMAs). These intermetallic alloys can be extremely compliant while retaining the strength of metals and can convert thermal energy to mechanical work. The unique properties of SMAs result from a reversible difussionless solid-to-solid phase transformation from austenite to martensite. The integration of SMAs into composite structures has resulted in many benefits, which include actuation, vibration control, damping, sensing, and self-healing. However, despite substantial research in this area, a comparable adoption of SMA composites by industry has not yet been realized. This discrepancy between academic research and commercial interest is largely associated with the material complexity that includes strong thermomechanical coupling, large inelastic deformations, and variable thermoelastic properties. Nonetheless, as SMAs are becoming increasingly accepted in engineering applications, a similar trend for SMA composites is expected in aerospace, automotive, and energy conversion and storage related applications. In an effort to aid in this endeavor, a comprehensive overview of advances with regard to SMA composites and devices utilizing them is pursued in this paper. Emphasis is placed on identifying the characteristic responses and properties of these material systems as well as on comparing the various modeling methodologies for describing their response. Furthermore, the paper concludes with a discussion of future research efforts that may have the greatest impact on promoting the development of SMA composites and their implementation in multifunctional structures