Smart Structural Materials Research Articles

Technical Analysis of Smart Material Structures and their Applications in Civil Engineering

Due to the continuous development in the field of innovative materials, the smart material and structures can be used as a new tool in architectural industry. A conventional architectural structure is designed to function under pre-assumed forces and loads (pressure) and thus it can’t develop itself an ability to control unexpected forces and loads. The designs using smart materials are inspired with nature to mimic human i.e. a material with capability of sensing and responding with the change in environment .The aim of research in the field of smart material structures is to make a system to mimic living organism with actuators and sensors. These materials have numerous applications in the field of civil engineering e.g. SMA (shape memory alloys) with super elastic properties (inspired with the concept of elasticity),can provide a control over the shape of the structure with changing crystalline structure via a change in temperature.

Variable stiffness modeling of smart cantilever beam under the electrical loading condition

The present paper is concerned with the analytical modeling for the variable stiffness of smart cantilever beam. The stiffness variation concept with the applied voltage on smart structural materials is currently in a developing stage as compared with the actuators and sensors. A mathematical model is presented to understand the stiffness variation with the applied voltage on the smart cantilever beam type structure. The fundamental laws of physics are the basis to develop the analytical model for the stiffness variation with the applied voltage. The obtained theoretical model of stiffness variation with the applied voltage is then compared and validated with the corresponding experimental data.

A magnetic-piezoelectric smart material-structure sensing three axis DC and AC magnetic-fields

In this paper, we demonstrate a smart material-structure can sense not only three-axis AC magnetic-fields but also three-axis DC magnetic-fields. Under x-axis and z-axis AC magnetic field ranging from 0.2 to 3.2 gauss, sensing sensitivity of the smart material-structure stimulated at resonant frequency is approximate 8.79 and 2.80 mV/gauss, respectively. In addition, under x-axis and z-axis DC magnetic fields ranging from 2 to 12 gauss, the sensitivity of the smart material-structure is 1.24–1.54 and 1.25–1.41 mV/gauss, respectively. In addition, under x-axis and z-axis DC magnetic fields ranging from 12 to 20 gauss, the sensitivity of the smart material-structure is 5.17–6.2 and 3.97–4.57 mV/gauss, respectively. These experimental results show that the smart material-structure successfully achieves three-axis DC and AC magnetic sensing as we designed. Furthermore, we also compare the results of the AC and DC magnetic-field sensing to investigate discrepancies. Finally, when applying composite magnetic-fields to the smart material-structure, the smart material-structure shows decent outputs as expected (consistent to the sensing principle). In the future, we believe the smart material-structure capable of sensing AC and DC magnetic fields will have more applications than conventional structures capable of sensing only DC or AC magnetic field. Thus, the smart material-structure will be an important design reference for future magnetic-field sensing technologies.

Thermal, mechanical, and shape‐memory properties of nanorubber‐toughened, epoxy‐based shape‐memory nanocomposites

ABSTRACTEpoxy‐based shape‐memory polymers (ESMPs) are a type of the most promising engineering smart polymers. However, their inherent brittleness limits their applications. Existing modification approaches are either based on complicated chemical reactions or done at the cost of the thermal properties of the ESMPs. In this study, a simple approach was used to fabricate ESMPs with the aim of improving their overall properties by introducing crosslinked carboxylic nitrile–butadiene nanorubber (CNBNR) into the ESMP network. The results show that the toughness of the CNBNR–ESMP nanocomposites greatly improved at both room temperature and the glass‐transition temperature (Tg) over that of the pure ESMP. Meanwhile, the increase in the toughness did not negatively affect other macroscopic properties. The CNBNR–ESMP nanocomposites presented improved thermal properties with a Tg in a stable range around 100 °C, enhanced thermal stabilities, and superior shape‐memory performance in terms of the shape‐fixing ratio, shape‐recovery ratio, shape‐recovery time, and repeatability of shape‐memory cycles. The combined property improvements and the simplicity of the manufacturing process demonstrated that the CNBNR–ESMP nanocomposites are desirable candidates for large‐scale applications in the engineering field as smart structural materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45780.

Shape optimization of solid–air porous phononic crystal slabs with widest full 3D bandgap for in-plane acoustic waves

The use of Phononic Crystals (PnCs) as smart materials in structures and microstructures is growing due to their tunable dynamical properties and to the wide range of possible applications. PnCs are periodic structures that exhibit elastic wave scattering for a certain band of frequencies (called bandgap), depending on the geometric and material properties of the fundamental unit cell of the crystal. PnCs slabs can be represented by plane-extruded structures composed of a single material with periodic perforations. Such a configuration is very interesting, especially in Micro Electro-Mechanical Systems industry, due to the easy fabrication procedure. A lot of topologies can be found in the literature for PnCs with square-symmetric unit cell that exhibit complete 2D bandgaps; however, due to the application demand, it is desirable to find the best topologies in order to guarantee full bandgaps referred to in-plane wave propagation in the complete 3D structure. In this work, by means of a novel and fast implementation of the Bidirectional Evolutionary Structural Optimization technique, shape optimization is conducted on the hole shape obtaining several topologies, also with non-square-symmetric unit cell, endowed with complete 3D full bandgaps for in-plane waves. Model order reduction technique is adopted to reduce the computational time in the wave dispersion analysis. The 3D features of the PnC unit cell endowed with the widest full bandgap are then completely analyzed, paying attention to engineering design issues.

Efficient and robust nonlinear model for smart materials with application to composite magnetostrictive plates

This paper presents a computationally efficient and robust nonlinear modeling framework for smart materials. The framework describes a smart material system through a new 3D inversion scheme for coupled nonlinear constitutive equations which can be integrated with the variational form of governing equations. Building on the Newton technique, the inversion scheme can be applied to any nonlinear smart material with a differentiable direct constitutive model. To further improve computational efficiency, the inversion scheme is integrated with a reduced dimensional (2D) model for smart composite structures. The resulting coupled 2D framework is applied to an aluminum-Galfenol composite plate that operates in actuation mode, and is solved using multiphysics finite element software. Major and minor magnetostriction curves are obtained for the actuator displacements at the tip of the Galfenol element by applying unbiased and biased magnetic fields. A significant advantage in numerical convergence and computational time, an almost six-time speedup for a dynamic simulation case, is demonstrated via comparison with an existing approach for magnetostrictive material modeling. The framework is suitable for fast design and optimization of nonlinear smart material structures.

Sustainable Environment using Smart Materials in Smart Structures

Objectives: The paper presents significant application of smart materials and their implementation in modern structures. The application of shape memory alloys, piezoelectric and magnetostrictive materials are provided in this paper for the readers. It also defines the architectural perspective in order to assess how architecture can develop with the advancement of smart materials. Methods: The scientific utilization of smart structural mechanics in the design, construction and preservation of infrastructures needs attention in civil engineering aspect. Smart meters are important components of next generation structures because they enable remote metering of energy consumption. The influence of TiO2 coated plastering mortar, in its fresh state has good thermal performance in building wall model and makes the building thermally efficient. Additionally it includes the sustainable use and potential contribution of Zero Energy Building (ZEB) principle towards achieving smart cities. Findings: It is found that these technological strides can be used for better reliability and overall safety of any structure. Thus the structural integrity, firmness and long term benefits are taken care of. Finally we came up with the conclusion that the effectiveness of using smart materials in smart structures can become an agent in building “towards a new architecture”. Applications: These materials are useful in creating a sustainable environment which are eco-friendly and leads to less energy consumption which is a boon to our society.

A magnetic–piezoelectric smart material-structure utilizing magnetic force interaction to optimize the sensitivity of current sensing

This paper presents a magnetic–piezoelectric smart material-structure using a novel magnetic-force-interaction approach to optimize the sensitivity of conventional piezoelectric current sensing technologies. The smart material-structure comprises a CuBe-alloy cantilever beam, a piezoelectric PZT sheet clamped to the fixed end of the beam, and an NdFeB permanent magnet mounted on the free end of the beam. When the smart material-structure is placed close to an AC conductor, the magnet on the beam of the smart structure experiences an alternating magnetic attractive and repulsive force produced by the conductor. Thus, the beam vibrates and subsequently generates a strain in the PZT sheet. The strain produces a voltage output because of the piezoelectric effect. The magnetic force interaction is specifically enhanced through the optimization approach (i.e., achieved by using SQUID and machining method to reorient the magnetization to different directions to maximize the magnetic force interaction). After optimizing, the beam’s vibration amplitude is significantly enlarged and, consequently, the voltage output is substantially increased. The experimental results indicated that the smart material-structure optimized by the proposed approach produced a voltage output of 4.01 Vrms with a sensitivity of 501 m Vrms/A when it was placed close to a conductor with a current of 8 A at 60 Hz. The optimized voltage output and sensitivity of the proposed smart structure were approximately 316 % higher than those (1.27 Vrms with 159 m Vrms/A) of representative piezoelectric-based current sensing technologies presented in other studies. These improvements can significantly enable the development of more self-powered wireless current sensing applications in the future.

Application of Smart Materials in SmartStructures

Smart materials are expected to be an important ingredient of third-generation structures. Candidate smart materials for structural applications include optical fiber-based sensors, Ferro-magnetic sensors, shape memory alloys and piezoelectric sensors. As sensor technologies advance, periodical evaluations of their performance should be conducted to identify the best-performing sensors available for the measurement of structural responses (e.g. displacement, velocity, acceleration, strain, and stress) and detecting structural damage (e.g. cracking, fatigue and corrosion). Such evaluations should consider their performance (e.g. reliability, sensitivity, integrity, and robustness) not only as stand-alone sensors but more importantly when externally attached to structural members as well as internally embedded in concrete and FRP materials. In construction, smart materials and systems could be used in „smart‟ buildings, for environmental control, security and structural health monitoring e.g. strain measurement in bridges using embedded fiber optic sensors. Magnetorheological fluids have been used to damp cable-stayed bridges and reduce the effects of earthquakes. In marine and rail transport, possibilities include strain monitoring using embedded fiber optic sensors. The paper discuss about types of smart materials, smart sensing Technology, components of smart structures, various sensors i.e. Fiber optic sensor, smart concrete, smart structure for seismic protection, health monitoring of smart structure.

Nonlinear dynamics and chaos in shape memory alloy systems

Smart material systems and structures have remarkable properties responsible for their application in different fields of human knowledge. Shape memory alloys, piezoelectric ceramics, magnetorheological fluids, and magnetostritive materials constitute the most important materials that belong to the smart materials category. Shape memory alloys (SMAs) are metallic alloys usually employed when large forces and displacements are required. Applications in aerospace structures, rotordynamics and several bioengineering devices are investigated nowadays. In terms of applied dynamics, SMAs are being used in order to exploit adaptive dissipation associated with hysteresis loop and the mechanical property changes due to phase transformations. This paper presents a general overview of nonlinear dynamics and chaos of smart material systems built with SMAs. Oscillators, vibration absorbers, impact systems and structural systems are of concern. Results show several possibilities where SMAs can be employed for dynamical applications.

Design of thin low-frequency smart material based on giant magnetostrictive actuator

Based on the design principle of alternating current electromagnetic circuit, this paper presents the design of a novel low-frequency high-power miniaturisation of the giant magnetostrictive actuator (GMA) under 10 kHz using Terfenol-D rod. A smart composite material is developed for noise reduction in underwater target. Finite element method is adopted to simulate and optimise the design of smart material structure, and the simulated resonance frequencies of the giant magnetostrictive materials (GMM) are found to be consistent with the measured values. Experiments were carried out in the water tube with GMM as active acoustic absorption material in active acoustic control system. Research results show that the giant magnetostrictive composite smart materials are active sound absorption materials effective for light-weight low-frequency broadband.

Towards the Standardized Fabrication of CNT-Cement Based Composites for Structural Health Monitoring: An Application-Oriented Literature Survey

Civil structures always experience degradation phenomena over their lifespan. The recent advances in nanotechnology and sensing allow to monitor the behaviour of a structure, assess its performance and identify damage at an early stage. The availability of innovative, high performance sensing tools gives the opportunity to carry out maintenance actions in a timely manner, and this definitely enhances the structural reliability and safety. Several Structural Health Monitoring (SHM) applications reported in the literature are traditionally performed at a global level, with a limited number of sensors distributed over a relatively large area of a structure. The main drawback with those systems is related to the possibility of detecting only major damage conditions. A recent progress in the field of civil SHM concerns the development of dense sensor networks and innovative structural neural systems. The latter reproduce the structure and the function of the human nervous system and provides interesting opportunities to overcome the typical limitations of SHM related to the poor spatial resolution of measurements. Miniaturization and embedment are key requirements for the successful implementation of structural neural systems. In this context carbon nanotubes (CNTs) play an attractive role in the development of embedded sensors and smart structural materials. In fact, they can provide to traditional cement based materials both structural capability and measurable response to applied stresses, strains, cracks and other flaws. As a result, cement based sensors can be developed and embedded, ensuring the maximum compatibility and minimum interference with the hosting structure. In this paper investigations about CNT/cement composites and their self-sensing capabilities are summarized and critically revised. The literature review has provided the informative basis for a rational analysis of published experimental results and theoretical developments.The result is an application oriented survey of the literature about CNT/cement composites for SHM. It provides useful design criteria for the standardized fabrication of CNT/cement composites optimized for SHM applications in civil engineering. Specific attention is paid to the opportunities provided by new RF plasma technologies for the functionalization of CNTs in view of sensor development and SHM applications.

Multi-scale mechanics of smart material systems and structures

During the last few decades, active composites have been in the focus of intense technological and fundamental researches from industry and academia, respectively. Besides, the wide use of passive composites in transport vehicles and infrastructures led to their functionalisation for their monitoring and control. Good candidates for related sensing, actuation or transduction functions are the so-called smart materials, such as piezoelectric materials, shape memory alloys or polymers, electroor magneto-strictive materials, electroor magnetorheological fluids and electro-active polymers. With the help of integrated control algorithms and processing devices, passive material systems and structures become smart; therefore, due to their multi-physical and multi-disciplinary nature, their multi-scale modelling and simulation are still not yet fully mastered. Hence, in order to reach robust designs of these advanced smart material systems and structures, special fundamental and applied research efforts are still required in order to reach: (i) materials multi-physical effective properties complete and reliable data sets; (ii) efficient multi-scale models and local/global solutions; (iii) mastering integrity and reliability critical issues for wider and safer applications. This focused issue of Acta Mechanica presents six revised, from ten peer-reviewed, manuscripts that were extended after their selection from the twelve contributions presented in two sessions at the Mini-Symposium MS27 on Multi-scale Mechanics of Smart Material Systems and Structures, co-organised by the present guest editors during the 8th European Solid Mechanics Conference held at Graz (Austria) on 9–13 July 2012. These six papers focused on one or more of the above mentioned research issues of Multi-scale Mechanics of Smart Material Systems and Structures; in particular, Micro-mechanics-based numerical homogenisations of magneto-electro-rheological particle and piezoelectric fibre reinforced polymer composite material systems, local (section)-global (structural) analytical models and solutions for the piezoelectric d15 shear-induced torsion actuation and sensing problems, multi-scale fatigue life analyses of polymer encapsulated piezoceramic transducers, and behaviour and response nonlinearities analyses for healthy and cracked piezoelectric transducers at room or cryogenic temperatures. It is hoped that this focused issue contributes to the progress of this topic state-of-the-art and serves the research needs of the Acta Mechanica readers. As a closure, we would like to thank the authors, for their high quality contributions; the reviewers, for their constructive expertises; and the Editor-in-Chief, Professor Hans Irschik, for letting us the entire freedom of this issue management and his editorial administration team for the great help in managing anonymously the managing guest editor’s co-authored contributions.

The Status of Research on Self-Sensing Properties of CNT-Cement Based Composites and Prospective Applications to SHM

Degradation phenomenacan affect civil structures over their lifespan. The recent advances innanotechnology and sensing allow to monitor the behaviour of a structure,assess its performance and identify damage at an early stage. Thus, maintenanceactions can be carried out in a timely manner, improving structural reliabilityand safety. Structural Health Monitoring (SHM) is traditionally performed at aglobal level, with a limited number of sensors distributed over a relativelylarge area of a structure. Thus, only major damage conditions are detectable. Densesensor networks and innovative structural neural systems, reproducing thestructure and the function of the human nervous system, may overcome thisdrawback of current SHM systems. Miniaturization and embedment are keyrequirements for successful implementation of structural neural systems. Carbonnanotubes (CNT) can play an attractive role in the development of embeddedsensors and smart structural materials, since they provide to traditionalmaterials like cement both structural capability and measurable response toapplied stresses, strains, cracks and other flaws. In this paper the mainresults of an extensive literature review about CNT/cement composites and theirself-sensing capabilities are summarized and critically revised. The analysisof experimental results and theoretical developments provides useful designcriteria for the fabrication of CNT/cement composites optimized for SHM applicationsin civil engineering.

Creation Sustainable Building Shell Using Smart Materials

It’s been almost a decade that the idea of smart materials has attracted man’s attention. These materials are capable of responding to their surrounding environment and of adapting to it. The development pace of construction materials has also been towards multi-purpose and smart materials, which would ultimately result in manufacturing phase matters. In fact, the existence of smart structural materials and systems has played a substantial role in developing the idea of the smart control of a construction. These materials can improve designing methods and the construction of buildings. In the sustainable buildings design approach (a new approach to designing buildings which should meet a high level of environmental standards with an emphasis on the costs of their useful lifespan), such highly efficient materials are used because they are more adaptable to the environment and increase a building’s useful lifespan. In this article, some of the smart materials used for the façade are introduced and their performances will be studied. It is concluded that using such technologies requires less energy and very little amounts of chemicals and detergents which could be a step taken towards achieving sustainable architectural and environmental goals.

A computational framework for the optimal design of morphing processes in locally activated smart material structures

A proof-of-concept study is presented for a strategy to obtain maximally efficient and accurate morphing structures composed of active materials such as shape memory polymers (SMP) through synchronization of adaptable and localized activation and actuation. The work focuses on structures or structural components entirely composed of thermo-responsive SMP, and particularly utilizes the ability of such materials to display controllable variable stiffness. The study presents and employs a computational inverse mechanics approach that combines a computational representation of the SMP thermo-mechanical behavior with a nonlinear optimization algorithm to determine location, magnitude and sequencing of the activation and actuation to obtain a desired shape change subject to design objectives such as prevention of damage. Two numerical examples are presented in which the synchronization of the activation and actuation and the location of activation excitation were optimized with respect to the combined thermal and mechanical energy for design concepts in morphing skeletal structural components. In all cases the concept of localized activation along with the optimal design strategy were able to produce far more energy efficient morphing structures and more accurately reach the desired shape change in comparison to traditional methods that require complete structural activation prior to actuation.

The resonance frequency shift characteristic of Terfenol-D rods for magnetostrictive actuators

This paper focuses on the resonance frequency shift characteristic of Terfenol-D rods for magnetostrictive actuators. A 3D nonlinear dynamic model to describe the magneto-thermo-elastic coupling behavior of actuators is proposed based on a nonlinear constitutive model. The coupled interactions among stress- and magnetic-field-dependent variables for actuators are solved iteratively using the finite element method. The model simulations show a good correlation with the experimental data, which demonstrates that this model can capture the coupled resonance frequency shift features for magnetostrictive actuators well. Moreover, a comprehensive description for temperature, pre-stress and bias field dependences of resonance frequency is discussed in detail. These essential and important investigations will be of significant benefit to both theoretical research and the applications of magnetostrictive materials in smart or intelligent structures and systems.

Intelligent Hybrid Control of Smart-Material Structure System by Using Magnetorheological Fluids and Isolators

Intelligent Hybrid Control of Smart-Material Structure System by Using Magnetorheological Fluids and Isolators

A study on PVDF sensor using wireless experimental system for bridge structural local monitoring

Originated from aerospace area, smart material structures have been a research hotspot in the application of engineering. For structural health monitoring within the context of civil engineering, the research about high-performance sensing units are very important. As one of the piezoelectric materials belonging to smart ones, Polyvinylidene Fluoride (PVDF) is widely regarded for its property advantages of low cost, good mechanical abilities, high sensibility, and corrosion resistance. In this paper, for the validation of PVDF sensors as sensing units for bridge structural local monitoring, wireless experimental systems of PVDF sensor for structural local monitoring on a bridge model and beam were built. Firstly, based on the operating mechanism, the measurement circuit and the characteristics of PVDF are introduced. Secondly, system framework of PVDF sensor for local monitoring is proposed, a bridge model is built, wireless sensor kits are then developed. Finally, Bridge damage monitoring experiments have been done for structural local health monitoring using PVDF sensors. The experimental results show that PVDF sensor can handle structural impact response monitoring and damage detection of civil engineering, and the developed wireless sensor experimental system can be easily implemented for use in practical monitoring engineering.

Research on applications of piezoelectric materials in smart structures

Piezoelectric materials have become the most attractive functional materials for sensors and actuators in smart structures because they can directly convert mechanical energy to electrical energy and vise versa. They have excellent electromechanical coupling characteristics and excellent frequency response. In this article, some research activities on the applications of piezoelectric materials in smart structures, including semi-active vibration control based on synchronized switch damping using negative capacitance, energy harvesting using new electronic interfaces, structural health monitoring based on a new type of piezoelectric fibers with metal core, and active hysteresis control based on new modified Prandtl-Ishlinskii model at the Aeronautical Science Key Laboratory for Smart Materials and Structures, Nanjing University of Aeronautics and Astronautics are introduced.