This PDF file contains the front matter associated with SPIE Proceedings Volume 9800, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

The desired operating range of ferroelectric materials with compositions near the morphotropic phase boundary is limited by field induced phase transformations. In [001]_C cut and poled relaxor ferroelectric single crystals the mechanically driven ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation is hindered by antagonistic electrical loading. Instability around the phase transformation makes the current experimental technique for characterization of the large field behavior very time consuming. Characterization requires specialized equipment and involves an extensive set of measurements under combined electrical, mechanical, and thermal loads. In this work a mechanism-based model is combined with a more limited set of experiments to obtain the same results. The model utilizes a work-energy criterion that calculates the mechanical work required to induce the transformation and the required electrical work that is removed to reverse the transformation. This is done by defining energy barriers to the transformation. The results of the combined experiment and modeling approach are compared to the fully experimental approach and error is discussed. The model shows excellent predictive capability and is used to substantially reduce the total number of experiments required for characterization. This decreases the time and resources required for characterization of new compositions.

Density functional theory (DFT) provides exceptional predictions of material properties of ideal crystal structures such as elastic modulus and dielectric constants. This includes ferroelectric crystals where excellent predictions of spontaneous polarization, lattice strain, and elastic moduli have been predicted using DFT. Less analysis has focused on quantifying uncertainty of the energy landscape over a broad range of polarization states in ferroelectric materials. This is non-trivial because the degrees of freedom contained within a unit cell are reduced to a single vector order parameter which is normally polarization. For example, lead titanate contains five atoms and 15 degrees of freedom of atomic nuclei motion which contribute to the overall unit cell polarization. Bayesian statistics is used to identify the uncertainty and propagation of error of a continuum scale, Landau energy function for lead titanate. Uncertainty in different parameters is quantified and this uncertainty is propagated through the model to illustrate error propagation over the energy surface. Such results are shown to have an impact in integration of quantum simulations within a ferroelectric phase field continuum modeling framework.

Ionic gels (IGs) using ionic liquids (ILs) can propose diverse applications in the field of optics, sensors and separation have opened wide prospects in materials science. ILs have attracted remarkable interest for gel polymer electrolytes and batteries based on their useful properties such as non-volatility, non-flammability, a wide electrochemical window, high thermal stability and a high ionic conductivity. The formation of gel in IL media makes it possible to immobilize ILs within organic or inorganic matrices and to take advantage of their unique properties in the solid state, thus eliminating some shortcomings related to shaping and risk of leakage. In this work for the first time we used multifunctional thiol monomers having uniform structure and good compatibility with the IL of our interest. Therefore we focused on developing thiol monomer-based IGs using multifunctional thiol monomers and acrylate crosslinkers utilizing thiol-ene reaction between monomer and crosslinking molecules in an IL medium and characterize their physico-chemical properties like thermal, conductive, mechanical properties etc.. This work has been focused mainly to improve the mechanical strength of IGs and make prospects of IGs in tribology and lubricants.

In this work, creep behavior of magnetorheological elastomers is investigated under combined magnetic and mechanical loading conditions. For the first time, a creep behavior model of MR elastomer is presented in this work in compression mode. A Weibull distribution function is used to model this behavior of MRE very well for both magnetic and mechanical loading conditions. This new model, which have been used previously for modeling recovery of thermosetting polymeric materials, is able to demonstrate the MRE creep behavior more accurately compared to previous models in the literature. The results show that the creep intensity is highly dependent on the carbonyl iron particle volume percentage of MRE samples, as well as the applied magnetic field.

This paper presents a new method to eliminate deviation in positioning caused by coil’s heat generation in magnetostrictive actuators. The advantages of the proposed system are compactness, high controllability and high reliability. The actuator package consists of Galfenol as active element and a magnification mechanism combined with a Peltier element or thermoelectric cooler (TEC). By using the temperature sensor, a thermoelectric cooler (TEC) is activated to reduce the temperature of the coil. However, the reduction of temperature by TEC alone is not enough to eliminate the error and controlling of applied voltage is also required. A simple PI controller for coil’s current is combined with TEC and by reducing the temperature and current simultaneously, the positioning error is vanished completely.

This paper proposes a method for preparing multi-walled carbon nanotubea/polydimethylsiloxane (MWCNTs/PDMS) composites with enhanced thermal properties by using a high magnetic field (up to 10T). The MWCNT are oriented magnetically inside a silicone by in-situ polymerization method. The anisotropic structure would be expected to produce directional thermal conductivity. This study will provide a new approach to the development of anisotropic thermal-conductive polymer composites.

Systematic studies with the preparation of silicone/graphene composites corresponding to their thermal and mechanical properties are carried out under various conditions: intensity of magnetic field, time, temperature, fillings. The effect of MWCNT/graphene content and preparation procedures on thermal conductivity of composites is investigated. Dynamic mechanical analysis (DMA) is used to reveal the mechanical properties of the composites in terms of the filling contents and magnetic field strength. The scanning electron microscope (SEM) is used to observe the micro-structure of the MWCNT composites. The alignment of MWCNTs in PDMS matrix is also studied by Raman spectroscopy. The thermal conductivity measurements show that the magnetically aligned CNT-composites feature high anisotropy in thermal conductivity.

The ability to monitor and predict the structural health of an aircraft is of growing importance to the aerospace industry. Currently, structural inspections and maintenance are based upon experiences with similar aircraft operating in similar conditions. While effective, these methods are time-intensive and unnecessary if the aircraft is not in danger of structural failure. It is imagined that future aircraft will utilize non-destructive evaluation methods, allowing for the near real-time monitoring of structural health. A particularly interesting method involves utilizing the unique transformation response of shape memory alloy (SMA) particles embedded in an aircraft structure. By detecting changes in the mechanical and/or electromagnetic responses of embedded particles, operators could detect the formation or propagation of fatigue cracks in the vicinity of these particles. This work focuses on a finite element model of SMA particles embedded in an aircraft wing using a substructure modeling approach in which degrees of freedom are retained only at specified points of connection to other parts or the application of boundary conditions, greatly reducing computational cost. Previous work evaluated isolated particle response to a static crack to numerically demonstrate and validate this damage detection method. This paper presents the implementation of a damage model to account for crack propagation and examine for the first time the effect of particle configuration and/or relative placement with respect to the ability to detect damage.

Numerical analysis of static cracks in a plane strain center-cracked infinite medium shape memory alloy (SMA) panel subjected to cyclic thermal variations and a constant mechanical load is conducted using the finite element method. In solid-state SMA actuators, permanent changes in the material's microstructure in the form of dislocations are caused during cyclic thermomechanical loading, leading to macroscopic irreversible strains, known as transformation induced plastic (TRIP) strains. The influence of these accumulated TRIP strains on mechanical fields close to the crack tip is investigated in the present paper. Virtual crack growth technique (VCCT) in ABAQUS FEA suite is employed to calculate the crack tip energy release rate and crack is assumed to be stationary (or static) so that the crack tip energy release rate never reaches the material specific critical value. Increase in the crack tip energy release rate is observed during cooling and its relationship with accumulation of TRIP due to cyclic transformation is studied.

Wire rope (or cables) are a fundamental structural element in many engineering applications. Recently, there has been growing interest in stranding NiTi wires into cables to scale up the adaptive properties of NiTi tension elements and to make use of the desirable properties of wire rope. Exploratory experiments were performed to study the actuation behavior of two NiTi shape memory alloy cables and straight monofilament wire of the same material. The specimens were held under various dead loads ranging from 50 MPa to 400 MPa and thermally cycled 25 times from 140°C to 5°C at a rate of 12°C/min. Performance metrics of actuation stroke, residual strain, and work output were measured and compared between specimen types. The 7x7 cable exhibited similar actuation to the single straight wire, but with slightly longer stroke and marginally more shakedown, while maintaining equivalent specific work output. This leads to the conclusion that the 7x7 cable effectively scaled up the adaptive properties the straight wire. Under loads below 150 MPa, the 1x27 cable had up to double the actuation stroke and work output, but exhibited larger shakedown and poorer performance when loaded higher.

Shape memory alloys (SMAs), due to their ability to repeatedly recover substantial deformations under applied mechanical loading, have the potential to impact the aerospace, automotive, biomedical, and energy industries as weight and volume saving replacements for conventional actuators. While numerous applications of SMA actuators have been flight tested and can be found in industrial applications, these actuators are generally limited to non-critical components, are not widely implemented and frequently one-off designs, and are generally overdesigned due to a lack of understanding of the effect of the loading path on the fatigue life and the lack of an accurate method of predicting actuator lifetimes. Previous efforts have been effective at predicting actuator lifetimes for isobaric dogbone test specimens. This study builds on previous work and investigates the actuation fatigue response of plate actuators with various stress concentrations through the use of digital image correlation and finite element simulations.

Shape memory materials (SMMs) are materials that can return to their virgin state and release mechanically induced strains by external stimuli. Shape memory polymers (SMPs) are a class of SMMs that show a high shape recoverability and which have attractive potential for structural applications. In this paper, we experimentally study the shape memory effect of origami based metamaterials. The main focus is on the Muira origami metamaterials. The fabrication technique used to produce origami structure is direct molding where all the geometrical features are molded from thermally virgin polymers without post folding of flat sheets. The study shows experimental investigations of shape memory metamaterials (SMMMs) made of SMPs that can be used in different applications such as medicine, robotics, and lightweight structures. The origami structure made from SMP blends, activated with uniform heating. The effect of blend composition on the shape memory behavior was studied. Also the influence of the thermomechanical and the viscoelastic properties of origami unit cell on the activation process have been discussed, and stress relaxation and shape recovery were investigated. Activation process of the unit cell has been demonstrated.

Shape memory polymer (SMP) is one of smart polymers which exhibit shape memory effect upon external stimuli. Recently, shape memory polymer composites (SMPCs) have been considered for space structure instead of shape memory alloys due to their deformability, lightweight and large recovery ratio, requiring characterization of their mechanical properties against harsh space environment and further prediction of the durability of SMPCs in space. As such, the durability of carbon fiber reinforced shape memory polymer composites (CF-SMPCs) was investigated using accelerated testing method based on short-term testing of CF-SMPCs in harsh condition. CF-SMPCs were prepared using woven carbon fabrics and a thermoset SMP via vacuum assisted resin transfer molding process. Bending tests with constant strain rate of CF-SMPCs were conducted using universal tensile machine (UTM) and Storage modulus test were conducted using dynamic mechanical thermal analysis (DMTA). Using the results, a master curve based on time-temperature superposition principle was then constructed, through which the mechanical properties of CF-SMPCs at harsh temperature were predicted. CF-SMPCs would be exposed to simulated space environments under ultra-violet radiations at various temperatures. The mechanical properties including flexural and tensile strength and shape memory properties of SMPCs would be measured using UTM before and after such exposures for comparison. Finally, the durability of SMPCs in space would be assessed by developing a degradation model of SMPC.

Flexible Thin-film Electrochemical Capacitors (ECs) are emerging technology that plays an important role as energy supply for various electronics system for both present era and the future. Intrinsically conductive polymers (ICPs) are promising pseudo-capacitive materials as they feature both good electrical conductivity and high specific capacitance. This study focuses on the construction and characterization of ultra-high surface area porous electrodes based on coating of nano-sized conductive polymer materials on nylon membrane templates. Herein, a novel nano-engineered electrode material based on nylon membranes was presented, which allows the creation of super-capacitor devices that is capable of delivering competitive performance, while maintaining desirable mechanical characteristics. With the formation of a highly conductive network with the polyaniline nano-layer, the electrical conductivity was also increased dramatically to facilitate the charge transfer process. Cyclic voltammetry and specific capacitance results showed promising application of this type of composite materials for future smart textile applications.

Piezoelectric nanowires, in particular zinc oxide (ZnO) nanowires, have been vastly used in the fabrication of electromechanical devices to convert wasted mechanical energy into useful electrical energy. Over recent years, the growth of vertically aligned ZnO nanowires on various structural fibers has led to the development of fiber-based nanostructured energy harvesting devices. However, the development of more realistic energy harvesters that are capable of continuous power generation requires a sufficient mechanical strength to withstand typical structural loading conditions. Yet, a durable, multifunctional material system has not been developed thoroughly enough to generate electrical power without deteriorating the mechanical performance. Here, a hybrid composite energy harvester is fabricated in a hierarchical design that provides both efficient power generating capabilities while enhancing the structural properties of the fiber reinforced polymer composite. Through a simple and low-cost process, a modified aramid fabric with vertically aligned ZnO nanowires grown on the fiber surface is embedded between woven carbon fabrics, which serve as the structural reinforcement as well as the top and the bottom electrodes of the nanowire arrays. The performance of the developed multifunctional composite is characterized through direct vibration excitation and tensile strength examination.

Lead zirconate titanate (PZT) fibers are mainly used in active fiber composites (AFC) where they are embedded in a polymer matrix. Interdigitated electrodes (IDE) along the direction of the fibers are used to achieve planar actuation, hereby exploiting the d₃₃ coefficient of PZT. When embedded in the AFC, the PZT fibers are subjected to mechanical loading as well as non-uniform electric field as a result of the IDEs. Therefore, it is important to characterize the electrical and electromechanical behavior of these fibers ex-situ using the IDE electrodes to assess the impact of nonuniform electric field on the properties of the fibers. For that reason, this work aims at quantifying the impact of IDE electrodes on the electrical and electromechanical behavior of PZT fibers, which is necessary for their successful implementation in devices like AFC. The tested fibers were purchased from Advanced Cerametrics and they have an average diameter of 250 micrometers. The IDE electrodes were screen printed on an acrylic substrate. The PZT fibers were subjected to frequency sweeps at low voltages to determine permittivity for parallel and interdigitated electrodes. The piezoelectric e₃₃ constant is determined from electromechanical testing of PZT fibers in parallel electrodes to compare the electromechanical behavior for PZT in bulk and fiber form. The dielectric constant and e₃₃ were found to be lower for the IDE and parallel electrodes compared to bulk but comparable to results published in literature.

Dielectric materials are commonly known as electrical insulators that can be polarized under strong electrical field. Currently, emerging dielectric research interests are focusing on nanoparticles mixed polymer based composites, since such materials demonstrated an astonishing increase in dielectric performance when compared to neat polymer matrix, due to the exponential increase in the interfacial area between the nanoparticles and polymer. Such findings infer that particle dispersion plays a critical role for the overall dielectric performance. In this study, we present a continuous manufacturing process consists of extrusion and stretching for Poly(vinylidene fluoride)/silane-treated titanium dioxide (PVDF/silane-treated TiO₂) flexible organic/inorganic polymer nanocomposites and the experimental result. Our results show that melt blending process is able to break down both silane treated and untreated micro-size TiO₂ agglomerates with extremely well dispersion in PVDF matrix. Follow-up studies and characterizations indicated that the material performances such as dielectric constant and dielectric loss are either similar or surpass the sample prepared via solvent casting and the effects of silane treatment are also discussed. A number of methods was used to characterize the composites, including AFM for dispersion verification and dielectric spectroscopy for dielectric analysis.

A nanoporous polyvinylidene Fluoride (PVDF) thin film was developed for applications in energy harvesting, medical surgeries, and industrial robotics. This sponge-like nanoporous PVDF structure dramatically enhanced the piezoelectric effect because it yielded considerably large deformation under a small force. A casting-etching method was adopted to make films, which is effective to control the porosity, flexibility, and thickness of the film. The films with various Zinc Oxide (ZnO) mass fractions ranging from 10 to 50% were fabricated to investigate the porosity effect. The piezoelectric coefficient d₃₃ as well as dielectric constant and loss of the films were characterized. The results were analyzed and the optimal design of the film with the right amount of ZnO nanoparticles was determined.

Human intervention can be replaced through development of tools resulted from utilizing sensing devices possessing a wide range of applications including humanoid robots or remote and minimally invasive surgeries. Similar to the five human senses, sensors interface with their surroundings to stimulate a suitable response or action. The sense of touch which arises in human skin is among the most challenging senses to emulate due to its ultra high sensitivity. This has brought forth novel challenging issues to consider in the field of biomimetic robotics. In this work, using a multiphase reaction, a polypyrrole (PPy) based hydrogel is developed as a resistive type pressure sensor with an intrinsically elastic microstructure stemming from three dimensional hollow spheres. Furthermore, a semi-analytical constriction resistance model accounting for the real contact area between the PPy hydrogel sensors and the electrode along with the dependency of the contact resistance change on the applied load is developed. The model is then solved using a Monte Carlo technique and the sensitivity of the sensor is obtained. The experimental results showed the good tracking ability of the proposed model.

Shape memory polymer (SMP) is one of smart polymers which exhibit shape memory effect upon external stimuli. Reinforcements as carbon fiber had been used for making shape memory polymer composite (CF-SMPC). This study investigated a possibility of designing self-deployable structures in harsh space condition using CF-SMPCs and analyzed their shape memory behaviors with constitutive equation model.CF-SMPCs were prepared using woven carbon fabrics and a thermoset epoxy based SMP to obtain their basic mechanical properties including actuation in harsh environment. The mechanical and shape memory properties of SMP and CF-SMPCs were characterized using dynamic mechanical analysis (DMA) and universal tensile machine (UTM) with an environmental chamber. The mechanical properties such as flexural strength and tensile strength of SMP and CF-SMPC were measured with simple tensile/bending test and time dependent shape memory behavior was characterized with designed shape memory bending test. For mechanical analysis of CF-SMPCs, a 3D constitutive equation of SMP, which had been developed using multiplicative decomposition of the deformation gradient and shape memory strains, was used with material parameters determined from CF-SMPCs. Carbon fibers in composites reinforced tensile and flexural strength of SMP and acted as strong elastic springs in rheology based equation models. The actuation behavior of SMP matrix and CF-SMPCs was then simulated as 3D shape memory bending cases. Fiber bundle property was imbued with shell model for more precise analysis and it would be used for prediction of deploying behavior in self-deployable hinge structure.

The purpose of this study is to improve fatigue properties of chopped carbon fiber reinforced plastics fabricated by SMC (Sheet Molding Compound) method and to clarify the mechanism for improvement. To enhance the properties, micro glass fibers with 500nm in diameter were added directly into vinyl ester resin with 0.3wt% contents. The chopped carbon fiber reinforced plastics were fabricated and cured at room temperature for 1hour under 1MPa and then at 60degree-C for 3hours. After curing, the fabricated plate was cut into the dimension of specimen. Tensile and bending strength and fatigue life of chopped carbon fiber reinforced plastics were investigated by tensile and three point bending test and cyclic tension-tension test, respectively. The behavior of strain concentration around the tips of carbon fiber were discussed with model specimen on the observations with DIC (Digital Image Correlation) method and polarizing microscope under tensile loading, in which one chopped carbon fiber was embedded into the matrix. In conclusion, when toughened vinyl ester resin modified with micro glass fibers was used as matrix, tensile and bending strength and fatigue life of chopped carbon fiber reinforced plastics were increased 56.6%, 49.8% and 14 to 23 times compared with those of unmodified specimens. It should be explained that static and dynamic properties of chopped carbon fiber reinforced plastics were improved by that crack initiation and propagation were prevented according to the prevention of the locally increasing of strain around the tip of carbon fiber, when vinyl ester resin modified with micro glass fibers was used as matrix.

One of the most effective uses for self repair is in material systems that crack because the cracks can allow the repair chemical to flow into the crack damage sites in all three dimensions. In order for the repair chemical to stay in the damage site and flow along to all the crack and repair there must be enough chemical to fill the entire crack. The repair chemical must be designed appropriately for the particular crack size and total volume of cracks. In each of the three examples of self repair in crackable brittle systems, the viscosity and chemical makeup and volume of the repair chemicals used is different for each system. Further the chemical delivery system has to be designed for each application also. Test results from self repair of three brittle systems are discussed.

In "Self Repair of Concrete Bridges and Infrastructure" two chemicals were used due to different placements in bridges to repair different types of cracks- surface shrinkage and shear cracks, In "Airplane Wings and Fuselage, in Graphite" the composite has very different properties than the concrete bridges. In the graphite for airplane components the chemical also had to survive the high processing temperatures. In this composite the cracks were so definite and deep and thin that the repair chemical could flow easily and repair in all layers of the composite. In "Ceramic/Composite Demonstrating Self Repair" the self repair system not only repaired the broken ceramic but also rebounded the composite to the ceramic layer

A thermally tunable periodic structure is proposed and studied through analytical and finite element methods to investigate the effect of thermomechanical coupling in dynamic regime. Bimaterial ligaments composed of two strips with contrast in their thermal expansion coefficients are employed to design local resonators inside a periodic structure. The thermally induced large deformations are utilized to exploit pattern change in the structure to control elastic wave propagation. Geometric and material nonlinearities are taken into account to study the dynamic response of the deformed structure. Once the temperature gradient is removed the structure tends to return to the initial state providing opportunities to be used as thermally tunable acoustic switches and filters.

The current work aims to explore the potential for in-situ structural health monitoring in polymer bonded energetic materials through the introduction of carbon nanotubes (CNTs) into the binder phase as a means to establish a significant piezoresistive response through the resulting nanocomposite binder. The experimental effort herein is focused towards electro-mechanical characterization of surrogate materials in place of actual energetic (explosive) materials in order to provide proof of concept for the strain and damage sensing. The electrical conductivity and the piezoresistive behavior of samples containing randomly oriented MWCNTs introduced into the epoxy (EPON 862) binder of 70 wt% ammonium perchlorate-epoxy hybrid composites are quantitatively and qualitatively evaluated. Brittle failure going through linear elastic behavior, formation of microcracks leading to reduction in composite load carrying capacity and finally macrocracks resulting in eventual failure are observed in the mechanical response of MWNT-ammonium perchlorateepoxy hybrid composites. Incorporating MWNTs into local polymer binder improves the effective stiffness about 40% compared to neat ammonium perchlorate-polymer samples. The real time in-situ relative change in resistance for MWNT hybrid composites was detected with the applied strains through piezoresistive response.

The recent progress of Nanotechnology allowed the development of new smart materials in several fields of engineering. In particular, innovative construction materials with multifunctional enhanced properties can be produced. The paper presents an experimental characterization on cement-matrix pastes doped with Carbon Nanotubes, Carbon Nano-fibers, Carbon Black and Graphene Nano-platelets. Both electro-mechanical and thermo-physical investigations have been carried out. The conductive nano-inclusions provide the cementitious matrix with piezo-resistive properties allowing the detection of external strain and stress changes. Thereby, traditional building materials, such as concrete and cementitious materials in general, would be capable of self-monitoring the state of deformation they are subject to, giving rise to diffuse sensing systems of structural integrity. Besides supplying self-sensing abilities, carbon nano-fillers may change mechanical, physical and thermal properties of cementitious composites. The experimental tests of the research have been mainly concentrated on the thermal conductivity and the optical properties of the different nano-modified materials, in order to make a critical comparison between them. The aim of the work is the characterization of an innovative multifunctional composite capable of combining self-monitoring properties with proper mechanical and thermal-energy efficiency characteristics. The potential applications of these nano-modified materials cover a wide range of possibilities, such as structural elements, floors, geothermal piles, radiant systems and more.

However, studies on the effect of nano-reinforcements in repeated impact scenarios are relatively limited. This work investigates the effect of resin nanoclay modification on the impact resistance of glass-fiber reinforced polymer (GFRP) composites subjected to repeated impacts. Three impact energy levels were used in experiments with a minimum of four specimens per case for statistical significance. Each sample was subjected to 40 repeated impacts or was tested up to perforation, whichever happened first. The impact response was evaluated in terms of evolution of the peak force, bending stiffness, visual damage inspection and optical transmission scanning (OTS) at critical stages as a function of number of impacts. Also, the damage degree (DD) was calculated to monitor the evolution of damage in the laminates. As expected, the impact response of the GFRP composites varied based on the presence of nano-clay and the applied impact energy. The modification of the resin with nano-clay introduced novel phenomena that changed the damage progression mechanism under repetitive impacts, which was verified by visual observation and optical transmission scanning. A better understanding of these phenomena (e.g. crack-bridging, tortuosity) and their contributions to enhancements in the impact behavior and modifications of the types of damage propagation can lead to better design of novel structural composites.

Recently, the reinforcement-matrix interface of fiber reinforced polymers has been modified through grafting nanostructures – particularly carbon nanotubes and ZnO nanowires – on to the fiber surface. This type of interface engineering has made a great impact on the development of multiscale composites that have high stiffness, interfacial strength, toughness, and vibrational damping – qualities that are mutually exclusive to a degree in most raw materials. Although the efficacy of such nanostructured interfaces has been established, the reinforcement mechanisms of these multiscale composites have not been explored. Here, strain transfer across a nanowire interphase is studied in order to gain a heightened understanding of the working principles of physical interface modification and the formation of a functional gradient. This problem is studied using a functionally graded piezoelectric interface composed of vertically aligned lead zirconate titanate nanowires, as their piezoelectric properties can be utilized to precisely control the strain on one side of the interface. The displacement and strain across the nanowire interface is captured using digital image correlation. It is demonstrated that the material gradient created through nanowires cause a smooth strain transfer from reinforcement phase into matrix phase that eliminates the stress concentration between these phases, which have highly mismatched elasticity.

Today carbon nanotubes have found various applications in structural, thermal and almost every field of engineering. Carbon nanotubes provide great strength, stiffness resilience properties. Evaluating the structural behavior of nanoscale materials is an important task. In order to understand the materialistic behavior of nanotubes, atomistic models provide a basis for continuum mechanics modelling. Although the properties of bulk materials are consistent with the size and depends mainly on the material but the properties when we are in Nano-range, continuously change with the size. Such models start from the modelling of interatomic interaction. Modelling and simulation has advantage of cost saving when compared with the experiments. So in this project our aim is to use a continuum mechanics model of carbon nanotubes from atomistic perspective and analyses some structural behaviors of nanotubes. It is generally recognized that mechanical properties of nanotubes are dependent upon their structural details. The properties of nanotubes vary with the varying with the interatomic distance, angular orientation, radius of the tube and many such parameters. Based on such models one can analyses the variation of young’s modulus, strength, deformation behavior, vibration behavior and thermal behavior. In this study some of the structural behaviors of the nanotubes are analyzed with the help of continuum mechanics models. Using the properties derived from the molecular mechanics model a Finite Element Analysis of carbon nanotubes is performed and results are verified. This study provides the insight on continuum mechanics modelling of nanotubes and hence the scope to study the effect of various parameters on some structural behavior of nanotubes.

Membranes separate fluid compartments and can comprise transport structures for selective permeation. In biology, channel proteins are specialized in their atomic structure to allow transport of specific compounds (selectivity). Conformational changes in protein structure allow the control of the permeation abilities by outer stimuli (gating). In polymeric membranes, the selectivity is due to electrostatic or size-exclusion. It can thus be controlled by size variation or electric charges. Controllable permeation can be useful to determine particle-size distributions in continuous flow, e.g. in microfluidics and biomedicine to gain cell diameter profiles in blood. The present approach uses patterned polyethylene terephthalate (PET) membranes with hydrogel surface coating for permeation control by size-exclusion. The thermosensitive hydrogel poly(N-isopropylacrylamide) (PNIPAAm) is structured with a cross-shaped pore geometry. A change in the temperature of the water flow through the membrane leads to a pore shape variation. The temperature dependent behavior of PNIPAAm can be numerically modeled with a temperature expansion model, where the swelling and deswelling is depicted by temperature dependent expansion coefficients. In the present study, the free swelling behavior was implemented to the Finite Element tool ABAQUS for the complex composite structure of the permeation control membrane. Experimental values of the geometry characteristics were derived from microscopy images with the tool Image J and compared to simulation results. Numerical simulations using the derived thermo-mechanical model for different pore geometries (circular, rectangle, cross and triangle) were performed. With this study, we show that the temperature expansion model with values from the free swelling behavior can be used to adequately predict the deformation behavior of the complex membrane system. The predictions can be used to optimize the behavior of the membrane pores and the overall performance of the smart membrane.

The piezoresistivity of carbon nanotube (CNT) reinforced nanocomposites is modeled using a multiscale damage modeling technique. Two phenomena of piezoresistivity are studied, the inherent piezoresistivity of the CNTs and the electrical tunneling effect. The damage model is developed under the framework of continuum damage mechanics (CDM) with a physical damage evolution equation inspired by Molecular Dynamics (MD) simulations. This damage model is applied to a nanocomposite unit cells with randomly dispersed CNTs. Orders of magnitude change in piezoresistivity is observed as the nanocomposite changes from non-damaged state to damaged state. This study provides insights into the prevailing mechanisms associated with piezoresistivity in the damaged and undamaged state of the CNT reinforced nanocomposites at the sub micro scale.

Due to their high strength to weight and stiffness to weight ratio, there is a huge shift towards the composite materials from the conventional metals, but composites have poor damage resistance in the transverse direction. Undergoing impact loads, they can fail in wide variety of modes which severely reduces the structural integrity of the component. This paper deals with the homogenization of glass-fibers and epoxy composite with a material introduced as an inelastic inclusion. This nonlinearity is being modelled by kinematic hardening procedure and homogenization is done by one of the mean field homogenization technique known as Mori-Tanaka method. The homogenization process consider two phases, one is the matrix and another is the inelastic inclusion, thus glass-fibers and epoxy are two phases which can be considered as one phase and act as a matrix while homogenizing non-linear composite. Homogenization results have been compared to the matrix at volume fraction zero of the inelastic inclusions and to the inelastic material at volume fraction one. After homogenization, increase of the energy dissipation into the composite due to addition of inelastic material and effects onto the same by changing the properties of the matrix material have been discussed.

Performance and efficiency of magnetostrictive transducer are highly dependent on working conditions. Magnetic bias field and pre-stress of the magnetostrictive rod are two of the main factors affecting the transducer behavior. Unexpected changes may cause unpredictable behavior of the transducer and a dramatic loss of performances. This paper experimentally investigates the effect of different working conditions on quality factor, bandwidth, resonance of a Terfenol-D resonance transducer that works in its first mode of vibration. For this purpose, an experimental setup consisting of laser Doppler, power amplifier and current transducer has been used. A Terfenol-D resonance transducer that is capable of changing magnetic bias field and mechanical pre-stress has been designed and fabricated. Working frequency of the transducer is between 5000 Hz to 7000 Hz. Output parameters of the transducer are experimentally calculated using an equivalent electrical circuit model. Results of the study improves the knowledge in the field and gives suggestions to the design of resonance transducers.

In current paper, a multi-degree freedom IPMC cylinder actuator was developed. The IPMC actuator was theoretically modeled and experimentally investigated. The surface electrode of the IPMC actuator was mechanically processed. By selectively activating specific regions of the IPMC actuator, multi-degree freedom locomotive behaviors can be achieved. A physical-based model of the IPMC actuator was developed based on the Poisson-Nernst-Planck system of equations. Experiments were conducted to verify the model. A good agreement between the theoretical results and experimental results is achieved. Current study may be useful on the fabricating, modeling and controlling of multi-degree freedom IPMC cylinder actuators.

A smart composite with functional fibers and reinforcement fibers optimally placed with an embroidery machine was created. Fiber orientation affects mechanical properties of composite laminates significantly. Accordingly, if the fibers can be placed along a desired curved path, fiber reinforced plastic (FRP) structures can be designed more lightly and more sophisticatedly. To this end a tailored fiber placement method using the embroidery machine have been studied. To add functions to the FRP structures, shape memory alloy (SMA) wires were placed as functional fibers. First, for a certain purpose the paths of the reinforcement fibers and the SMA wires were simultaneously optimized in analysis. Next, the reinforcement fibers and tubes with the SMA wires were placed on fabrics by using the embroidery machine and this fabric was impregnated with resin by using the vacuum assisted resin transfer molding method. This smart composite was activated by applying voltage to the SMA wires. Fundamental properties of the smart composite were examined and the feasibility of the proposed creation method was shown.

In the traditional layered piezoelectric structures, high stress concentrations could cause the structural failure in interlayer surfaces due to repeated strain reversals. To overcome the performance limitations of these structures, the concept of Functionally Graded Materials (FGMs) has been introduced to improve the lifetime, integrity, and reliability of these structures. In this paper, the free and forced vibration of radially polarized Functionally Graded Piezoelectric (FGP) cylinders under different sets of loading are studied. Material properties such as piezoelectric, elastic and permittivity are assumed to change along its thickness, based on a specific gradation function. Four-parameter power law distribution is used to grade the volume fraction of the constituents comprising of PZT-5A and PZT-5H. Material property is assumed to be temperature dependent for a few numerical studies. The present modeling approach is validated by comparing the free and forced vibration of radially polarized Functionally Graded Piezoelectric (FGP) cylinders with those reported in the literature. The effects of material composition, loading and boundary conditions on the dynamic behavior of FGP cylinder are described. Since the modeling of functionally graded piezoelectric systems is challenging, the present study can help in the design and analysis of FGP cylinders.