Multi-scale mechanics of smart material systems and structures

Written by a team of experts that has been working together for several years in the context of a research network involving international institutions, this book brings several applications related to smart material systems such as vibration and noise control, structural health monitoring, energy harvesting and shape memory alloys. Furthermore, this book also provides basic knowledge on the fundamentals of smart material systems and structures. Consequently, the present title serves as an important resource for advanced undergraduate and graduate students. In addition, it serves as a guide for engineers and scientists working with smart structures and materials both with an application and basic research perspective. Smart material systems and structures represent a new paradigm which is increasing the capabilities of engineering systems. Adaptability and versatility are some important aspects related to such systems. In brief, research on smart materials is characterized by synergistically combining different physical features, such as mechanical, electrical, chemical, and magnetic. As a result, smart material technologies have a huge potential to enhance the performance of engineering structures opening unlimited opportunities to innovation and economic benefits

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.

Smart materials and related technologies have been drawing an increasing amount of attention from researchers in related fields worldwide. In the past decade, smart materials and structures has been one of the most progressive fields of research. Recently developed materials and devices have been used to address many challenges in aerospace, mechanical, bionics and medical technologies. The progress made in developing advanced materials and devices is impressive and encouraging.The theme of this special section is smart actuators and applications. This is one of the research areas of smart materials and structures that is recognized as an essential aspect of smart technologies. Therefore, we have organized this special section to promote the development of technology as well as international communication in this field. In the section, current progress in the field of smart materials and structures is presented. The papers published cover the most recent research results in the development of several different kinds of smart materials (e.g. fiber-reinforced shape memory polymer composites, electro-rheological fluids, electro-active papers, shape memory alloys etc). In addition, applications of the materials in smart structures are also included. We believe that the papers published in this special section will be found to provide the latest information and will encourage more researchers to make their contribution to this field of research.The eight papers in the special section were selected from the proceedings of the International Conference on Smart Materials and Nanotechnology 2007 (SMN 2007). The conference was held at the Harbin Institute of Technology, Harbin, People's Republic of China (1–4 July 2007). The conference was an effort to integrate smart materials and nanotechnology with applications from bioengineering to photonics, with an emphasis on application in aerospace engineering. It also addressed and predicted novel developments in this research field. The papers were carefully selected to be representative of over 290 contributions presented at the conference.We would like to take this opportunity to thank all the authors for their hard work and excellent contributions. The valuable progress and significant research results in the field of smart materials and applications deserve to be treasured. We would also like to express our gratitude to all the reviewers for their support and suggestions, thus ensuring the quality of the papers and permitting the publication of this special section.

Nonlinear dynamics and chaos in shape memory alloy systems

Shape memory alloys (SMA) are applied as actuator materials in smart structures and in fastening and pre-stressing devices. Shape memory alloys can be divided into three groups: one-way alloys, two-way alloys and magnetically controlled SMAs. The magnetically controlled SMAs recently suggested by one of the present authors are potential actuator materials for smart structures because they may provide rapid strokes with large amplitudes under precise control. The most extensively applied conventional SMAs are Ni-Ti and Cu- based alloys. Iron-based shape memory alloys, especially Fe-Mn-Si steels, are becoming more and more important in engineering applications due to their low price. The properties of Fe- Mn-Si steels have been improved by alloying, for example, with Cr, Ni and Co. Nitrogen alloying was shown to significantly improve shape memory, mechanical and corrosion properties of Fe-Mn-Si-based steels. Tensile strengths over 1500 MPa, recovery stresses of 300 MPa and recoverable strains of 4% have been attained. In fasteners made from these steels, stresses of 700 MPa were reached. The beneficial effect of nitrogen alloying on shape memory and mechanical properties is based on the decrease of stacking fault energy and increase of the strength of austenite caused by nitrogen atoms. Nitrogen alloyed Fe-Mn-Si- based steels are expected to be employed as actuator materials in pre-stressing and fastening applications in many fields of engineering. Nitrogen alloyed shape memory steels possess good manufacturing properties and weldability, and they are economical to process using conventional industrial methods.

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, the research activities and achievements on the applications of piezoelectric materials in smart structures in China, including vibration control, noise control, energy harvesting, structural health monitoring, and hysteresis control, are introduced. Special attention is given to the introduction of semi-active vibration suppression based on a synchronized switching technique and piezoelectric fibers with metal cores for health monitoring. Such mechanisms are relatively new and possess great potential for future applications in aerospace engineering.

In 1993, NSF initiated a program development effort that might have major research implications to civil engineering as well as other science and engineering disciplines. That was a continuous, multidisciplinary, broad-based research program focused on civil infrastructure systems (CIS). The concept, framework, and extent of the proposed CIS research program are presented. The importance of system and intellectual integration are emphasized. Following this effort, major steps have been taken in both domestic and international fronts to define specific research agendas in key areas of CIS such as hazard mitigation and smart material systems and structures. Research needs and opportunities in several cross-cutting areas such as hazard mitigation, smart and advanced materials, and adaptive structures are presented. The relationship of CIS and other strategic initiatives is also explained.

The functional properties of Shape Memory Alloys (SMA's) are used succesfully at present in a variety of industrial and medical applications. The use of these materials in smart structures is now emerging in the field of aeronautic/space technology. Many applications require higher operating temperatures than available to date, or higher cooling rates and/or a higher number of cycles. For this purpose the properties and fabricability of commercial alloys as Ni-Ti-(X), Cu-Al-Ni or Cu-Zn-Al are being adjusted and improved. Other feasible alloys are being developed. The research and development is directed towards the control of the stress, strain, temperature and time dependence of shape memory properties for a stable in-service behaviour. In this paper the various approaches taken up in recent years by academic and industrial laboratories for developing high temperature SMA's are reviewed.

The Japanese Smart Material and Structure System Project started in 1998 and has been developing several key sensor and actuator elements. This project consists of four research groups that consist of structural health monitoring, smart manufacturing, active/adaptive structures, and actuator materials/devices. In order to integrate the developed sensor and actuator elements into a smart structure system and show the validity of the system, two demonstrator programs have been established. Both demonstrators are CFRP stiffened cylindrical structures with 1.5 m in diameter and 3 m in length. The first demonstrator integrates the following six innovative techniques: (1) impact damage detection using embedded small-diameter optical fiber sensors newly developed in this program, (2) impact damage detection using the integrated acoustic emission (AE) system, (3) whole-field strain mapping using the BOTDR/FBG integrated system, (4) damage suppression using embedded shape memory alloy (SMA) foils, (5) maximum and cyclic strain sensing using smart composite patches, and (6) smart manufacturing using the integrated sensing system. The second one is for demonstrating the suppression of vibration and acoustic noise generated in the composite cylindrical structure. High-performance PZT actuators developed in this program are also installed. The detailed design of the demonstrator was made and the testing program has been planned to minimize the time and the cost for the demonstration. The present status of the demonstrator program is presented, including the success and difficulty in the on-going program.

Emerging interest to synthesize active, engineered matter suggests a future where smart material systems and structures operate autonomously around people, serving diverse roles in engineering, medical, and scientific applications. Similar to biological organisms, a realization of active, engineered matter necessitates functionality culminating from a combination of sensory and control mechanisms in a versatile material frame. Recently, metamaterial platforms with integrated sensing and control have been exploited, so that outstanding non‐natural material behaviors are empowered by synergistic microstructures and controlled by smart materials and systems. This emerging body of science around active mechanical metamaterials offers a first glimpse at future foundations for autonomous engineered systems referred to here as soft, smart matter. Using natural inspirations, synergy across disciplines, and exploiting multiple length scales as well as multiple physics, researchers are devising compelling exemplars of actively controlled metamaterials, inspiring concepts for autonomous engineered matter. While scientific breakthroughs multiply in these fields, future technical challenges remain to be overcome to fulfill the vision of soft, smart matter. This Review surveys the intrinsically multidisciplinary body of science targeted to realize soft, smart matter via innovations in active mechanical metamaterials and proposes ongoing research targets that may deliver the promise of autonomous, engineered matter to full fruition.

Two different processing methods were employed, hot pressing and cold pressing for fabricating Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramic bulk samples, which could be used in the applications of electromechanical actuators in smart material system and structures. The dielectric constant, dielectric loss of these samples versus frequency and temperature were measured and analyzed.

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 societyKeywords: Magnetostrictive Materials, Piezoelectric Materials, Shape Memory Alloys, Smart Meters, ZEB

Auxetics comes from the Greek (auxetikos), meaning ‘that which tends to expand’. The term indicates specifically materials and structures with negative Poisson’s ratio (NPR). Although the Poisson’s ratio is a mechanical property, auxetic solids have shown evidence of multifunctional characteristics, ranging from increased stiffness and indentation resistance, to energy absorption under static and dynamic loading, soundproofing qualities and dielectric tangent loss. NPR solids and structures have also been used in the past as material platforms to build smart structural systems. Auxetics in general can be considered also a part of the ‘negative materials’ field, which includes solids and structures exhibiting negative thermal expansion, negative stiffness and compressibility. All these unusual deformation characteristics have the potential to provide a significant contribution to the area of smart materials systems and structures. In this focus issue, we are pleased to present some examples of novel multifunctional behaviors provided by auxetic, negative stiffness and negative compressibility in smart systems and structures. Particular emphasis has been placed upon the multidisciplinary and systems approach provided by auxetics and negative materials, also with examples applied to energy absorption, vibration damping, structural health monitoring and active deployment aspects.Three papers in this focus issue provide significant new clarifications on the role of auxeticity in the mechanical behavior of shear deformation in plates (Lim), stress wave characteristics (Lim again), and thermoelastic damping (Maruszewski et al ). Kochmann and Venturini describe the performance of auxetic composites in finite strain elasticity. New types of microstructures for auxetic systems are depicted for the first time in three works by Ge et al , Zhang et al , and Kim and co-workers. Tubular auxetic structures and their mechanical performance are also analyzed by Karnessis and Burriesci. Foams with negative Poisson’s ratio constitute one of the main examples of auxetic materials available. The focus issue presents two papers on this topic, one on a novel microstructure numerical modeling technique (Pozniak et al ), the other on experimental and model identification results of linear and nonlinear vibration behavior (Bianchi and Scarpa). Nonlinearity (now in wave propagation for SHM applications) is also investigated by Klepka and co-workers, this time in auxetic chiral sandwich structures. Vibration damping and nonlinear behavior is also a key feature of the auxetic structural damper with metal rubber particles proposed by Ma et al . Papers on negative material properties are introduced by the negative stiffness and high-frequency damper concept proposed by Kalathur and Lakes. A cellular structure exhibiting a zero Poisson’s ratio, together with zero and negative stiffness, is presented in the work of Virk and co-workers. Negative compressibility is examined by Grima et al in truss-type structures with constrained angle stretching. Finally, Grima and co-workers propose a concept of tunable auxetic metamaterial with magnetic inclusions for multifunctional applications.AcknowledgmentsWe would like to thank all the authors for their high quality contributions. Special thanks go also to the Smart Materials and Structures Editorial Board and the IOP Publishing team, with particular mention to Natasha Leeper and Bethan Davies for their continued support in arranging this focus issue in Smart Materials and Structures .

Starting from the very definition of smart structures and smart materials, this paper addresses the fundamental mechanism of operation of some well known smart materials like piezoelectric ceramic/polymer, electrostrictive ceramic, magnetostrictive alloy, shape memory alloy, electroheological fluid, magnetoheological fluid, optical fibers and so on. It also describes briefly the working principles of the actuators and sensor based upon these materials. In addition to that an overview of the various applications and research dealing with the application of these smart materials in aerospace structures mainly in the context of vibration suppression, shape control and adaptive structures for their efficient functioning has been presented. On the whole the presentation stresses on actuators. Since it is the actuator not the sensor that is often the limiting factor in smart structure used for active control. Numerous investigations have been made and are on the way to improve upon the piezoelectric and electrostrictive actuator for greater generating force and larger stroke, as well as shape memory alloy actuator for fast response. Development of multilayer piezoelectric and electrostrictive actuator and discovery of precompressed piezoelectric element and actuator is a forward leap in that direction.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Nowadays, the use of smart materials in structures is a major concern to structural engineers. The act of benefiting from numerous advantages of these materials is the main objective of researches and studies focused on seismic and structural engineering. In the present study, in addition to the development of finite element models of several steel frames using ABAQUS software, the effect of shape memory alloys (SMAs) on superelastic behavior and the various types of eccentric braces will be checked. Moreover, it was observed that the use of SMAs within various types of bracing systems of steel frames leads to a decrease in the reduction factor of the frames. Also, the eccentric bracing in which SMAs are utilized in the middle of bracing led to the highest effect on reduction of lateral drift of the frames and decrease of reduction factor. The obtained results indicated that the application of smart materials led to increasing of strain energy and base shear of the first plastic hinge, which is followed by a decrease in the reduction factor of the frame.