bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Additive Manufacturing and Electric Poling Techniques on PVdF Thin Films: Towards 3D Printed Functional Materials
Authors: Fan Jinsheng , Gonzalez David , Garcia Jose , Newell Brittany , Nawrocki Robert A. 
Published: November 2020

Abstract
Mechanical flexibility, faster processing, lower fabrication cost and biocompatibility enable poly (vinylidene fluoride) (PVdF) to have a wide range of applications. This work investigated the use of a piezoelectric polymeric material, PVdF, in combination with 3D printing, to explore new strategies for the fabrication of smart materials with embedded functions, namely sensing. The motivation behind this research was to design and fabricate PVdF thin films that will be used to build pressure sensors with applications in active intelligent structures. In this work, 3D printed PVdF thin films with thickness values in the range of 250 to 350 μm were poled under high direct current electrical fields, which were varied from 0.4 to 12 MV/m and temperatures from 80 to 140 °C. Copper electrodes were applied, forming a standard capacitor layered structure, to facilitate poling and to collect piezoelectric output voltage. The poling process enabled the piezoelectric crystalline phase transition of printed PVdF films to transfer from the non-active a α-phase to the piezoelectric active β-phase and rearranged the dipole alignments of the β-phase. The efficiency of poling was evaluated through the piezoelectric constant calculated from measured calibration curves. These calibration curves demonstrated the PVdF sensing device have a positive linear correlation between mechanical input and voltage output. We found that a peak value in piezoelectric constant correlated with poling voltages and temperatures. The highest piezoelectric constant achieved through contact poling was 32.29 pC/N poled at 750 V and 120 °C, and temperature was deemed the most important factors to influence piezoelectric constant. We believe that the present work demonstrates a path towards fully 3D printed smart, functional materials.
The Piezoresistive Response of CNF/Epoxy to One-Dimensional Strain Wave Excitation via Remote Loading
Authors: Hernandez J. A. , Tallman T. N. 
Published: November 2020

Abstract
The piezoresistive effect in conductive nanofiller-modified polymer, cementitious, and ceramic composites has immense potential to enable multifunctional properties such as intrinsic self-sensing. To date, much work has been done to study the piezoresistive effect under quasi-static loading. Some work has also been done to study the piezoresistive effect under cyclic loading such as when a piezoresistive patch is adhered directly to an oscillating substrate. However, little-to-no work has been done with regard to general dynamic loading conditions such as strain waves originating from a remote source. This is an important gap in the state of the art for two reasons: One, coupling the self-sensing nature of nanocomposites with general elastodynamics is a possible pathway to enabling the study of full-field dynamics (i.e. using the piezoresistive effect to study internal dynamics as opposed to just surface measurements available via tools such as accelerometers and laser vibrometry). And two, coupling piezoresistive self-sensing with damage detection via vibratory methods could lead to transformative gains in the areas of structural health monitoring (SHM) and nondestructive evaluation (NDE). Therefore, we herein work towards addressing this gap in the state of the art by developing basic knowledge on the relation between elastic strain waves and piezoresistive response. Specifically, an electromagnetic-piezoelectric shaker is used to inject highly-controlled strain waves into a long and slender carbon nanofiber (CNF)-modified epoxy rod. Resistance changes along the length of the rod are then measured as strain waves travel along the length of the rod. It is shown that the measured resistance response closely matches the applied mechanical loading. Results from this preliminary study suggest the establishment of an exciting new field — piezoresistive elastodynamics.
Development of Shape Memory-Based Elastic-Adaptive Damping Elements for Sport and Rehabilitation Equipment
Authors: Hoffmann Fabian , Roj Robin , Theiß Ralf , Dültgen Peter 
Published: November 2020

Abstract
The generation and variation of forces necessary to achieve a training stimulus is often realized in sports and rehabilitation equipment by manually adjustable masses or by complex motor-brake systems. This leads to heavy and unwieldy systems, which cannot be used flexibly, and in addition to high costs. The main objective of this paper is to prove that pseudoelastic shape memory alloys (SMA) are potentially suitable for use in sports and rehabilitation equipment and offer additional value in the area of training flexibility combined with high training resistance. Therefore, the properties of pseudoelastic SMAs for this application were investigated. These multifunctional materials offer the potential for special elastic and sensory properties. The pseudoelastic effect is based on stress-induced martensite formation, which allows high elastic deformations. During this phase transformation, the mechanical stress passes through a plateau. The stress plateau can be moved by changing the temperature of the SMA. The determination of properties of pseudoelastic SMAs with different alloy compositions was carried out according to the specifications of “VDI 2248: Product Development with Shape Memory Technology”. With a functional model based on the material tests, which replaces a commercially available force clamping device, the monitoring of force, displacement and temperature changes can be realized by the integrated sensor technology. This paper presents the methodology, experiments and findings for the use of pseudoelastic SMAs in sport and rehabilitation devices. It concludes with prospects to commercial application.
Performance of a Multifunctional Spiral Shaped Acoustic Metamaterial With Synchronized Low-Frequency Noise Filtering and Energy Harvesting Capability
Authors: Mir Fariha , Banerjee Sourav 
Published: November 2020

Abstract
Metamaterials are man-made materials that behave uniquely and possess exclusively desired properties that are not found in natural materials. Usually, it is the combination of two or more materials and can be engineered to perform tasks that are not possible with traditional materials. These were initially discovered while working with electromagnetic radiation. Apart from electromagnetic radiation, metamaterials are also capable of affecting the wave propagation characteristics through any fluid such as air. These metamaterials are called acoustic metamaterials. Many acoustic metamaterials have gone beyond its definition but still, characterize the waveguiding properties. Incorporation of smart materials while constructing acoustic metamaterial, can achieve multifunctionality of the design. A prospective application field for such acoustic metamaterials is energy harvesting from low-frequency vibration. It is conceptualized that acoustic metamaterials can be used as noise barrier materials to filter roadside and industrial noise. This application can get extended to the aerospace application where engine noise mitigation inside the cabin is a challenge. In this article, a spiral-shaped acoustic metamaterial is modeled which has a dual function of noise filtering and energy harvesting. This acoustic metamaterial has a comparatively high reflection coefficient closer to the anti-resonance frequencies, resulting in high sound transmission loss. The filtered noise is trapped inside the cell in the form of strain energy. Hence, we claim that if the trapped energy which is any way wasted in the material could be harvested to power the local electronic devices, the new solution could make transformative for the 21st century’s green energy solution. Calculated placement of smart materials in the cell-matrix can help to extract the strain energy in the form of power. The acoustic metamaterial cell presented in this work has the capability of isolating noise and reducing diffraction by trapping sound in low frequencies and at the same time recover the trapped abundant energy in the form of electrical potential using piezoelectric materials. The spiral design is sensitive to vibration due to trampoline shaped attachments inside the cell. This makes it capable of harvesting energy using vibration also. This is a promising acoustoelastic metamaterial with multifunctionality properties for future applications.
Non-Traditional Shape Variations on Bistable Carbon Fiber Reinforced Polymer Laminates
Authors: Nelon Christopher M. , Figueroa Jonathan , Myers Oliver J. , Shepard Aaron 
Published: November 2020

Abstract
The ability of a material to display two equilibrium states, called bistability, has been previously observed in carbon fiber reinforced polymers (CFRPs). For bistability to occur, the laminate must consist of an unsymmetric layup about its midplane which generates internal residual stress from thermal contraction. Prior studies have observed bistability in CFRPs with small-scale rectangular geometries where all sides were less than 250 mm. The aim of this paper is to demonstrate the existence of bistability in large-scale CFRPs with rectangular and non-rectangular geometries. Experiments and finite element analyses were conducted to determine the viability of bistability in large-scale CFRPs where at least one length aspect of the specimen was greater than or equal to 304.8 mm.
Specimens whose shapes included rectangles, deltoids, triangles, and circles, were fabricated and tested to determine the presence of bistability and the associated curvature for each cured equilibrium state. Rectangular specimens had a side length of 914.4 mm and widths that varied from 177.8 to 457.2 mm. For the deltoids, triangles, and circles, one length aspect (i.e. the height, hypotenuse, and diameter, respectively) equaled 304.8 mm. Finite element models were created to compare the equilibrium shapes’ curvatures and displacements with the experimental laminates; the existence of bistability was also examined using a nondimensionalized bifurcation plot.
Experimentally, bistability was found to occur for the fabricated laminates up to six plies. As the studied laminates could be considered thin, they displayed cylindrical cured shapes. The non-traditional shaped CFRPs followed bistability trends found for traditional, small-scale, rectangular laminates. An inverse relationship between the ply count and curvature was exhibited for the large-scale, rectangular laminates; curvature decreased as the number of plies in the laminate increased.
Structurally Embedded Gradient Index Lens for Extended Amplification of Guided Waves in Polymer Pipes
Authors: Danawe H. , Wang Z. , Tol S. , Okudan G. , Ozevin D. 
Published: November 2020

Abstract
In this paper, we propose a novel gradient index metamaterial lens to focus elastic wave energy in polymer pipes. We investigate multi-mode focusing of guided ultrasonic waves in a poly-vinyl chloride (PVC) pipe by designing and integrating an embedded gradient index (GRIN) lens within the pipe wall. The metamaterial lens is composed of equally spaced cylindrical brass inserts embedded into the pipe wall. All the inserts are of same height which is equal to the half-thickness of the pipe. Insert diameters are varied in circumferential direction to realize hyperbolic secant distribution of refractive index around the circumference of pipe. We explore focusing of three pipe wave modes commonly used for guided wave inspection of pipelines namely, L(0,2), L(0,1) and T(0,1), using a single lens design. We further verify the lens performance through numerical simulations estimating the amplification of wave energy in focal regions of the GRIN lens for these three modes. We also estimate attenuation of guided waves propagating in PVC pipe through experimental measurements.
Autonomous Multifunctional Vehicle With Integrated Bio-Inspired SMA Actuated Grasper
Authors: Changoski Vasko , Domazetovska Simona , Anachkova Maja , Jovanova Jovana 
Published: November 2020

Abstract
The space exploration activities are merging new technologies in order to develop systems challenged to achieve capabilities for high mission experience. Inspired by the numerous applications in space exploration, with the integration of shape memory alloys (SMAs), a 3D printed continuous All Terrain Grasper Transport (AT-GT) vehicle with implemented multi-locomotion grasper was created.
In order to reduce failure of the mechanical system, the vehicle is equipped with SMA suspension and SMA tensioner of a pulley system with adaptable height able to achieve movement on a given trajectory and adjust to any terrain. SMA actuators provide controllable actuation based on the simplicity of their design and the shape memory effect.
By using the advantages of the origami engineering, soft robotics and smart material implementation, a bio-inspired autonomous grasper was integrated on the AT-GT, capable of leaving the vehicle, grabbing an object and bringing it back to the vehicle.
The concept development, the analytical models and the prototype including the benefits of the combined work of the vehicle and the grasper are presented.
Flow Control and Separation Delay in Morphing Wing Aircraft Using Traveling Wave Actuation
Authors: Olivett A. , Corrao P. , Karami M. A. 
Published: November 2020

Abstract
This study examines the biomimicry of wave propagation, a mode of locomotion in aquatic life for the use-case of morphing aircraft surfaces for boundary layer control. Such motion is theorized to inject momentum into the flow on the upper surface of airfoils, and as a consequence, creates a forcible pressure gradient thereby increasing lift. It is thought that this method can be used to control flow separation and reduce likelihood of stall at high angles of attack. The motivation for such a mechanism is especially relevant for aircraft requiring abrupt maneuvers, and especially at high angles of attack as a safety measure against stalling. The actuation mechanism consists of lightweight piezoelectric ceramic transducers placed beneath the upper surface of an airfoil. An open-loop system controls surface morphing. A two-dimensional Fourier Transform technique is used to estimate traveling to standing wave ratio, which is verified analytically using Euler Bernoulli beam theory, and experimentally using a prototype wing. Propagating wave control is tuned and verified using a series of scanning laser vibrometry tests. A custom two-dimensional NACA 0018 airfoil tests the concept in a low-speed wind tunnel with approximate Reynolds Number of 50,000. Both traveling waves and the changes in lift and drag will be experimentally characterized.
A Computational Framework for Predicting Properties From Multifield Processing Conditions in Polymer Matrix Composites
Authors: Widdowson Denise , von Lockette Paris , Erol Anil , Rodriguez Manuel A. 
Published: November 2020

Abstract
Composites can be tailored to specific applications by adjusting process variables. These variables include those related to composition, such as volume fraction of the constituents and those associated with processing methods, methods that can affect composite topology. In the case of particle matrix composites, orientation of the inclusions affects the resulting composite properties, particularly so in instances where the particles can be oriented and arranged into structures. In this work, we study the effects of coupled electric and magnetic field processing with externally applied fields on those structures, and consequently on the resulting material properties that arise. The ability to vary these processing conditions with the goal of generating microstructures that yield target material properties adds an additional level of control to the design of composite material properties. Moreover, while analytical models allow for the prediction of resulting composite properties from constituents and composite topology, these models do not build upward from process variables to make these predictions.
This work couples simulation of the formation of microscale architectures, which result from coupled electric and magnetic field processing of particulate filled polymer matrix composites, with finite element analysis of those structures to provide a direct and explicit linkages between process, structure, and properties. This work demonstrates the utility of these method as a tool for determining composite properties from constituent and processing parameters. Initial particle dynamics simulation incorporating electromagnetic responses between particles and between the particles and the applied fields, including dielectrophoresis, are used to stochastically generate representative volume elements for a given set of process variables. Next, these RVEs are analyzed as periodic structures using FEA yielding bulk material properties. The results are shown to converge for simulation size and discretization, validating the RVE as an appropriate representation of the composite volume. Calculated material properties are compared to traditional effective medium theory models. Simulations allow for mapping of composite properties with respect to not only composition, but also fundamentally from processing simulations that yield varying particle configurations, a step not present in traditional or more modern effective medium theories such as the Halpin Tsai or double-inclusion theories.
Controlling the Rotational DOF of Laminar Jamming Structures With End Clamping Mechanism
Authors: Allen Emily A. , Swensen John P. 
Published: November 2020

Abstract
Variable stiffness structures lie at the nexus of soft robots and traditional robots as they enable the execution of both high-force tasks and delicate manipulations. Laminar jamming structures, which consist of thin flexible sheets encased in a sealed chamber, can alternate between a rigid state when a vacuum is applied and a flexible state when the layers are allowed to slide in the absence of a pressure gradient. In this work, an additional mode of controllability is added by clamping and unclamping the ends of a simple laminar jamming beam structure. Previous works have focused on the translational degree of freedom that may be controlled via vacuum pressure; here we introduce a rotational degree of freedom that may be independently controlled with a clamping mechanism. Preliminary results demonstrate the ability to switch between three states: high stiffness (under vacuum), translational freedom (with clamped ends, no vacuum), and rotational freedom (with ends free to slide, no vacuum).
Deadbands Tell No Tails: X-56A Dynamic Actuation Requirements
Authors: Pankonien Alexander M. , Suh Peter M. , Schaefer Jacob R. , Mitchell Robert M. 
Published: November 2020

Abstract
Following significant effort over the past several years by AFRL and NASA, the X-56A flight vehicle has proven to be a useful platform for exploring controllers and distributed actuation on a flexible, swept flying-wing. The program sought to advance the state of the art in airworthiness for vehicles encountering flutter, leading to relaxed design constraints that could drastically decrease structural weight and improve aircraft performance. Specifically, the vehicle was designed to encounter different forms of flutter: body-freedom flutter, and wing-bending torsion flutter, making it an ideal candidate for identifying dynamic actuation challenges. Flight testing led to fundamental observations by controller designers about the actuation needs for such a vehicle. Namely, the small inherent actuator deadband led to significant constant-amplitude limit cycle oscillations of the system during post-flutter controlled flight. This work captures these observations by exploring theoretical changes in the actuators via a nonlinear simulation tuned with flight testing data and shows that a 60% reduction in actuator deadband can improve ride quality by nearly 50%. The results are combined into a set of actuation challenges for the adaptive structures community at large, including precise actuation for a large number of cycles over multiple timescales, with a relevant baseline described by original actuation system.
Characterization of a Multifunctional Bioinspired Piezoelectric Swimmer and Energy Harvester
Authors: Wang Yu-Cheng , Kohtanen Eetu , Erturk Alper 
Published: November 2020

Abstract
Fiber-based flexible piezoelectric composites with interdigitated electrodes, namely Macro-Fiber Composite (MFC) structures, strike a balance between the deformation and actuation force capabilities for effective underwater bio-inspired locomotion. These materials are also suitable for vibration-based energy harvesting toward enabling self-powered electronic components. In this work, we design, fabricate, and experimentally characterize an MFC-based bio-inspired swimmer-energy harvester platform. Following in vacuo and in air frequency response experiments, the proposed piezoelectric robotic fish platform is tested and characterized under water for its swimming performance both in free locomotion (in a large water tank) and also in a closed-loop water channel under imposed flow. In addition to swimming speed characterization under resonant actuation, hydrodynamic thrust resultant in both quiescent water and under imposed flow are quantified experimentally. We show that the proposed design easily produces thrust levels on the order of biological fish with similar dimensions. Overall it produces thrust levels higher than other smart material-based designs (such as soft material-based concepts), while offering geometric scalability and silent operation unlike large scale robotic fish platforms that use conventional and bulky actuators. The performance of this untethered swimmer platform in piezoelectric energy harvesting is also quantified by underwater base excitation experiments in a quiescent water and via vortex induced-vibration (VIV) experiments under imposed flow in a water channel. Following basic resistor sweep experiments in underwater base excitation experiments, VIV tests are conducted for cylindrical bluff body configurations of different diameters and distances from the leading edge of the energy harvesting tail portion. The resulting concept and design can find use for underwater swimmer and sensor applications such as ecological monitoring, among others.
Dating lacustrine carbonate strata with detrital zircon U-Pb geochronology
Authors: Finzel Emily S. , Rosenblume Justin A. 
Published: November 2020

Abstract
Carbonate lacustrine strata in nonmarine systems hold great potential for refining depositional ages through U-Pb dating of detrital zircons. The low clastic sediment flux in carbonate depositional environments may increase the relative proportion of zircons deposited by volcanic air fall, potentially increasing the chances of observing detrital ages near the true depositional age. We present U-Pb geochronology of detrital zircons from lacustrine carbonate strata that provides proof of concept for the effectiveness of both acid-digestion recovery and resolving depositional ages of nonmarine strata. Samples were collected from Early Cretaceous foreland basin fluvial sandstone and lacustrine carbonate in southwestern Montana (USA). Late Aptian–early Albian (ca. 115–110 Ma) maximum depositional ages young upsection and agree with biostratigraphic ages. Lacustrine carbonate is an important component in many types of tectonic basins, and application of detrital zircon U-Pb geochronology holds considerable potential for dating critical chemical and climatic events recorded in their stratigraphy. It could also reveal new information for the persistent question about whether the stratigraphic record is dominated by longer periods of background fine-grained sedimentation versus short-duration coarse-grained events. In tectonically active basins, lacustrine carbonates may be valuable for dating the beginning of tectonic subsidence, especially during periods of finer-grained deposition dominated by mudrocks and carbonates.