Damage nucleation and growth can be complex in hybrid structures composed of layers of metal and laminated composites. Presently there are limited reliable damage growth analytical and empirical methods to evaluate the bond integrity of such structures and to quantify the state of bonding in such joints. Depending on the geometry and accessibility of hybrid joints, ultrasonic nondestructive testing (NDT) techniques are available for inspection of these structures. However there are some limitations for the usage of typical bulk or guided waves to quantify the integrity of bondline in hybrid structures. This work suggests the use of specific forms of ultrasonic guided waves that propagate along the bondline of these hybrid structures. This study is dedicated to modeling of interface guided waves for the purpose of disbond crack damage assessment. The nature of interface waves is discussed and the numerical simulation based on the material properties and geometries of hybrid interfaces as well as composite stacking sequence is verified. A finite element model of a hybrid structure with isotropic and anisotropic multilayer composites is constructed. The behavior of interface guided waves influenced by disbond cracks at free edges of hybrid bonded joints is numerically studied. The propagation characteristics of interface waves is shown to be sensitive to the size of disbond cracks. The velocity of interface waves is shown to have an inverse relation to the disbond damage size. Results show the speed is also a function of the interfacing ply orientation at the bondline. These results suggest that interface waves can be used to monitor the condition of bonded joints in hybrid structures.

The unique micro/nano-structure of an intrinsically conducting polymer can be tuned to get higher gauge factors (GF) and reliability, which make them better materials for piezo-resistive applications than conducting carbon based composites and metallic composites. This work reports a highly sensitive conducting polyaniline (PANI)-based composite film that showed a GF ∼66. This high GF was achieved by forming a particular microstructure of conducting PANI particles in a free standing film of PANI-DBSA/EVA. The paper also attempts to explain the mechanism for the observed high sensitivity using the electronic percolation theory, shape and size of the conducting particles and the changes in the microstructure, due to strain. The high sensitivity, high stability during cyclic loading and low electrical hysteresis together with high mechanical strength make PANI-DBSA/EVA conducting composite film a promising material for piezo-resistive strain sensing applications.

In this study, we investigate underwater energy harvesting from torsional vibration of a patterned ionic polymer metal composite (IPMC). The IPMC design consists of a rectangular polymer strip with patterned electrodes to split the top and bottom surfaces in two equal pairs. We focus on harmonic base excitation of an IPMC, which is modeled as a slender beam with thin cross section vibrating in a viscous fluid. Torsional vibrations with large–amplitude are described using a complex hydrodynamic function considering nonlinear hydrodynamic damping from the surrounding fluid. Along with the theoretical beam model, an electromechanical model is utilized to predict the IPMC electrical response from the torsional deformation of the beam. The integration of both models allows to predict the output voltage of the IPMC from the knowledge of the frequency and amplitude of base excitation. The theoretical predictions are validated against experiments.

In this study, we seek to understand the feasibility of energy harvesting from the tail beating motion of a fish through active compliant materials. Specifically, we analyze energy harvesting from the undulations of a biomimetic fish tail hosting ionic polymer metal composites (IPMCs). The design of the biomimetic tail is specifically inspired by the morphology of the heterocercal tail of thresher sharks. We propose a modeling framework for the underwater vibration of the biomimetic tail, wherein the tail is assimilated to a cantilever beam with rectangular cross section. We focus on base excitation in the form of a superimposed rotation about a fixed axis and we consider the regime of moderately large–amplitude vibrations. In this context, the effect of the encompassing fluid is described through a nonlinear hydrodynamic function. The feasibility of harvesting energy from an IPMC attached to the vibrating structure is assessed and modeled via an electromechanical framework. Experiments are performed to validate the theoretical expectations on energy harvesting from the biomimetic tail.

Design and actuation modes of IntraVAD assistive device for end stage congestive heart failure patients are discussed in this paper. Flexibility, biocompatibility and coupled behavior of Ionic Polymer Metal Composites and Shape Memory Alloys allow replicating the motion of natural heart to address the cardiac deficiency. The squeezing motion of the heart is approximated by propulsion mechanism of a jelllyfish, while the rising-twisting motion of the heart is augmented by upward-downward motion of a cone shaped structure. These motion mechanisms may be combined or used separately, in order to create various blood flow regimes and provide different levels of support for each individual. Not only as actuators, but SMAs and IPMCs may be utilized as sensors to provide feedback from instantaneous status of the device to the controller. A device embodiment is introduced and followed by discussion on IPMC and antagonistic two-way SMA actuators in order to explain how actuation modes are delivered.

In this paper, we propose a physics-based model of ionic polymer metal composites (IPMCs) charge dynamics in response to dynamic mechanical deformation by developing a perturbation solution of a particular form of the Poisson-Nernst-Planck equations. We derive an equivalent nonlinear circuit model whose components are directly controlled by the imposed mechanical deformation. We show results for a variety of loading scenarios to gather insight on the nonlinear characteristics of IPMC electrical response and its potential application in sensors and energy harvesting devices.

In this paper, we analyze the chemoelectrical behavior of ionic polymer metal composites (IPMCs) in the small voltage range with a novel hypothesis on the charge dynamics in proximity of the electrodes. Specifically, this paper introduces a so-called composite layer which extends between the polymer membrane and the metal electrode. This homogeneous layer describes the charge distribution at the electrode via two species of charge carriers, that is, electrons and mobile counterions. Charge dynamics is described by adapting the multi-physics formulation based on the Poisson-Nernst-Planck (PNP) equations through the incorporation of the electron transport in the composite layer. Under the hypothesis of small voltage input, we use the linearized PNP model to derive an equivalent IPMC impedance model with lumped elements. The equivalent model is represented as a resistor connected in series with the parallel of a capacitor and a Warburg impedance element. These elements idealize the phenomena of charge build up in the double layer region and the faradaic impedance related to mass transfer, respectively. We validate the equivalent model through measurements on in-house fabricated samples addressing both IPMC step response and impedance.

Ionic Polymer Transducers (IPTs), also known as Ionic Polymer Metal Composites (IPMCs), are a promising group of intelligent materials which exhibit electromechanical coupling behavior in both actuation and sensing. They are composed of an electroactive ionomer, inserted between metallic electrodes. In this study, IPTs are experimentally examined as a sensor in the aspect of electrode composition optimization. Sensors with electrodes having several volumetric percentages of metallic powder, ruthenium dioxide -RuO 2 -, are tested in bending under different step displacement inputs to explore the output current response. Optimum metallic powder content in the electrode solution for a sensor generating maximum current output is determined. Furthermore, the magnitude of the tip deflection’s effect on sensitivity is examined. The IPTs used in the experiments are fabricated via Direct Assembly Process which enables direct control over the electrode architecture.

This paper presents the design, fabrication, and characterization of a second generation biomimetic jellyfish robot that uses ionic polymer metal composites (IPMCs) as flexible actuators for propulsion. The shape and swimming style of this underwater vehicle are based on the Aurelia aurita jellyfish, which has an average swimming speed of 13 mm/s and which is known for a high swimming efficiency. The critical components of the vehicle include the flexible bell that provides the overall shape and dimensions of the jellyfish, a central hub used to provide electrical connections and mechanical support to the actuators, and flexible IPMC actuators that extend radially from the central hub. In order to provide increased shape holding ability and reduced weight, the bell is fabricated from a commercially available heat-shrinkable polymer film. A new lightweight hub has been designed and was fabricated by 3D printing using ABS plastic material. The hub features internal electrical contacts for providing voltage to the individual IPMC actuators. Finally, a new set of IPMC actuators are manufactured using the Direct Assembly Process (DAP). The IPMC actuators constructed for this study demonstrated peak-to-peak strains of ∼ 0.7% in water across a frequency range of 0.1–1.0Hz. By tailoring the applied voltage waveform and the flexibility of the bell, the completed robotic jellyfish swam at maximum speed of 1.5 mm/s.

Ionic polymer metal composites (IPMC) are a new class of smart materials that have attractive characteristics such as muscle like softness, low voltage and power consumption, and good performance in aqueous environments. Thus, IPMC’s provide promising application for biomimetic fish like propulsion systems. In this paper, we design and analyze IPMC underwater propulsor inspired from swimming of Labriform fishes. Different fish species in nature are source of inspiration for different biomimetic flapping IPMC fin design. Here, three fish species with high performance flapping pectoral fin locomotion is chosen and performance analysis of each fin design is done to discover the better configurations for engineering applications. In order to describe the behavior of an active IPMC fin actuator in water, a complex hydrodynamic function is used and structural model of the IPMC fin is obtained by modifying the classical dynamic equation for a slender beam. A quasi-steady blade element model that accounts for unsteady phenomena such as added mass effects, dynamic stall, and the cumulative Wagner effect is used to estimate the hydrodynamic performance of the flapping rectangular shape fin. Dynamic characteristics of IPMC actuated flapping fins having the same size as the actual fins of three different fish species, Gomphosus varius , Scarus frenatus and Sthethojulis trilineata , are analyzed with numerical simulations. Finally, a comparative study is performed to analyze the performance of three different biomimetic IPMC flapping pectoral fins.

This paper presents model reference adaptive control (MRAC) of underwater vehicle propelled by the Ionic polymer metal composite (IPMC) actuator. Trajectories of the vehicle are controlled by simultaneously controlling the bias and amplitude of the sinusoidal voltage applied to the IPMC actuator attached at the real end of the vehicle. It is assumed that the system parameters as well as high frequency gain matrix are unknown. Using Lyapunov stability theory and factorization of the high frequency gain matrix, an adaptive output feedback control is designed for trajectory control of a heading angle and a speed of the vehicle. In the proposed approach, SDU (Square Diagonal and Upper triangular matrix) decomposition of the high frequency gain (HFG) matrix is used. Only signs of the leading principle minors of the HFG matrix are assumed to be known. Simulations results are presented to show that precise trajectory control of the heading and speed is achieved in spite of the coupling between controlled variables.

Application of Ionic Polymer Metal Composites (IPMCs) for curvature sensing and measurement of dynamic structures has been presented. IPMC’s are electro active polymers that exhibit the characteristics of both actuators and sensors. The flexibility of IPMC makes it possible to be applied both in small and large deflection applications. Developing a curvature sensor based on IPMC can be of high importance in a wide variety of fields including shape monitoring of deployable structures in which the curvature of structure varies during deployment process until it maintains a target curvature. In this article, in order to characterize the IPMC sensor properties for curvature sensing, various experimental procedures have been conducted including sensing response of IPMC sensor to sinusoidal and step deflections at different frequencies. The effect of voltage recovery of IPMC on sensing signal was studied by applying the deformation in the form of ramp functions at very slow rates of curvature variation. Experiments show that due to the linear response of IPMC sensor to curvature change at different rates, it could be potentially used as a sensitive curvature sensor for several structural applications.

In this paper, a closed-loop feedback controller is developed for the underwater vehicle propelled by ionic polymer metal composite (IPMC) actuator. The dynamics of the underwater vehicle with IPMC actuator are modeled using the large deflection beam model and hydrodynamic forces due to its interaction with the surrounding water. The hydrodynamic force coefficients are identified based on the results of extensive computational fluid dynamics (CFD) simulations. The path of the vehicle is controlled by simultaneously controlling the yaw angle and speed of the vehicle using the proportional controllers. Simulation data is utilized to find the relation between control input parameters namely, amplitude and bias of the voltage applied to the IPMC, and yaw angle and speed of the vehicle. In the simulations, frequency of the control input is assumed to be fixed. Simulation results show that the proposed controller can be effectively used to steer the under water vehicles propelled by IPMC.