Sustainable Environment using Smart Materials in Smart Structures

The concept of an adaptive aircraft wing, i.e., whose shape parameters such as camber, span-wise twist, and thickness can be varied to optimize the wing shape for various flight conditions, has been extensively studied by numerous researchers. While the aerodynamic benefits (in terms of increased lift/drag ratios, improved maneuverability, and delayed flow separation) have been analytically and experimentally established, the complexity and weight penalty of the designs and actuation using smart materials could potentially alleviate the shortcomings of prior designs, leading the way to a more practical `smart' adaptive wing which responds to changes in flight and environmental conditions by optimally modifying its shape. A summary of recent work in the area of adaptive wing concepts incorporating smart structures technologies is presented. Emphasis is placed on continuing research at Northrop Grumman under a United States Defense Advanced Research Projects Agency contract entitled `Smart Structures and Materials Development-Smart Wing,'. Limitations and potential benefits of adaptive wing designs, applications and advantages of smart material actuators and sensors, and results of recent tests are discussed. Recommendations for future work required to develop an operational smart adaptive wing are also outlined.

Advances in smart materials and structures technology, especially in applications of Shape Memory Alloys (SMA) as actuators and vibration isolation devices require understanding of the nonlinear hysteretic response found in SMAs. SMA hysteresis can be modeled either through constitutive models based on physical material parameters or through models based on system identification. In this work, a simplified material model for the pseudoelastic response of SMAs is presented, suitable for vibration isolation applications. Response obtained from the simplified model is compared with the response obtained from an existing thermodynamic constitutive SMA model and the results from the two models are found to match well. The computation time required by the simplified model was approximately seven times faster compared with the thermodynamic constitutive model. The simplified model is utilized to simulate a single degree of freedom mass-SMA system where the SMA acts as a passive vibration isolation device, showing a substantial reduction in displacement transmissibility.

Shape memory alloys (SMAs) are often used in smart materials and structures as the active components. Their ability to provide a high force and large displacement has been useful in many applications, including devices for damage control, active structural acoustic control, dynamic tuning, and shape control. The paper presents a macroscopic mathematical model which captures the thermomechanical behaviors and the two-way shape memory effect (TWSME) of SMAs, and SMA applications as an actuator to control the shape of a circular composite cylinder. The radial displacement control of an externally pressurized circular composite cylinder where a thin SMA layer actuator is bonded inside the cylinder is investigated numerically. The circular composite cylinder with the thin SMA layer was designed and analyzed to determine the feasibility of such a system for the removal of stiffeners from externally pressurized stiffened composite structures. SMAs start to transform from the martensitic into the austenitic state upon actuation through resistive heating, simultaneously recover the prestrain, and thus cause the composite cylinder to expand in the radial direction. The externally pressurized composite cylinder with the SMA actuators was analyzed using the 3-D finite element method.

Building on the research performed during the DARPA/AFRL/NASA Smart Wing Phase 1 program (Kudva, J.N. et al. (July 1999). Overview of the DARPA/AFRL/NASA Smart Wing Program, SPIE Symposium on Smart Structures and Materials, Newport Beach, CA, Vol. 3674, pp. 230 6; Martin, C.A. et al. (1999). Smart Materials and Structures Smart Wing Phase 1 Final Report, AFRL-ML-WP-TR-1999-4162, Air Vehicles Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH.) sought to improve vehicle aerodynamic efficiency using control surfaces actuated by smart materials, the goal of the Phase 2 effort was to develop larger scale, smart hingeless control surfaces capable of high-rate actuation and quantify their performance benefits at test conditions representative of operational flight environments. To achieve this goal, a 30-percent geometric scale, full-span wind tunnel model of a proposed Northrop Grumman Corporation (NGC) Uninhabited Combat Air Vehicle (UCAV) was designed and tested. The model incorporated conventional, hinged control surfaces on the left side and smart, hingeless control surfaces on the right to allow incremental aerodynamic performance comparisons; including lift increment due to unit control surface deflection (CL), and roll moment due to unit control surface deflection (Cld). This paper describes the design, fabrication, system integration, and ground test results of the Smart Wing Phase 2 model. Topics that are covered include: (1) wind tunnel model selection; (2) analysis and design procedure; (3) smart control surface integration; (4) model instrumentation; and (5) static load and Ground Vibration Test (GVT) results and correlation.

In recent years, increasing research efforts have been devoted to the development of new controllable dampers, in the aim of mitigating vibration of mechanical equipment, automobile, civil construction and so on. Most of the new controllable dampers are made with special performance of smart materials, such as MR/ER fluid, piezoelectric ceramic and shape memory alloy. Although has similar smart performance such as rapid response time, low power requirement and large driving force with those smart materials, magnetostrictive material, especially magnetostrictive composite material is only got attention by a few researchers. In this paper, by analysis character of magnetosrtrictive effect, the possible applications of magnetosrtrictive composite material in area of vibration control are discussed; several new dampers, made with magnetosrtrictive composite material, such as smart friction or viscous dampers are presented.

Research on smart meters has shown that fine-grained energy usage data poses privacy risks since it allows inferences about activities inside the home. While smart meter deployments are very limited, more than 40 million meters in the United States have been equipped with Automatic Meter Reading (AMR) technology over the past decades. AMR utilizes wireless communication for remotely collecting usage data from electricity, gas, and water meters. Yet to the best of our knowledge, AMR has so far received no attention from the security research community. In this paper, we conduct a security and privacy analysis of this technology. Based on our reverse engineering and experimentation, we find that the technology lacks basic security measures to ensure privacy, integrity, and authenticity of the data. Moreover, the AMR meters we examined continuously broadcast their energy usage data over insecure wireless links every 30s, even though these broadcasts can only be received when a truck from the utility company passes by. We show how this design allows any individual to monitor energy usage from hundreds of homes in a neighborhood with modest technical effort and how this data allows identifying unoccupied residences or people's routines. To cope with the issues, we recommend security remedies, including a solution based on defensive jamming that may be easier to deploy than upgrading the meters themselves.

Liquid crystal elastomers (LCEs) are shape-morphing materials whose large and reversible shape transformations are caused by the coupling between the mobile anisotropic properties of liquid crystal (LC) units and the rubber elastic of polymer networks. Their shape-changing behaviors under certain stimuli are largely directed by the LC orientation; therefore, various strategies have been developed to spatially modulate the LC alignments. However, most of these methods are limited as they require complex fabrication technologies or have intrinsic limitations in applicability. To address this issue, programmable complex shape changes in some LCE types, such as polysiloxane side-chain LCEs, thiol-acrylate main-chain LCEs, etc., were achieved by using a mechanical alignment programming process coupled with two-step crosslinking. Here, we report a polysiloxane main-chain LCE with programmable 2- and 3D shape-changing abilities that were created by mechanically programming the polydomain LCE with two crosslinking steps. The resulting LCEs exhibited a reversible thermal-induced shape transformation between the initial and programmed shapes due to the two-way memory between the first and second network structures. Our findings expand on the applications of LCE materials in actuators, soft robotics, and smart structures where arbitrary and easily programmed shape morphing is needed.

Smart structures are a result of effective integration of control system design and signal processing with the structural systems to maximally utilize the new advances in materials for structures, actuation and sensing to obtain the best performance for the application at hand. The research in smart structures is constantly driving towards attaining self adaptive and diagnostic capabilities that biological systems possess. This has been manifested in the number of successful applications in many areas of engineering such as aerospace, civil and automotive systems. Instrumental in the development of such systems are smart materials such as piezo-electric, shape memory alloys, electrostrictive, magnetostrictive and fiber-optic materials and various composite materials for use as actuators, sensors and structural members. The need for development of control systems that maximally utilize the smart actuators and sensing materials to design highly distributed and highly adaptable controllers has spurred research in the area of smart structural modeling, identification, actuator/sensor design and placement, control systems design such as adaptive and robust controllers with new tools such a neural networks, fuzzy logic, genetic algorithms, linear matrix inequalities and electronics for controller implementation such as analog electronics, micro controllers, digital signal processors (DSPs) and application specific integrated circuits (ASICs) such field programmable gate arrays (FPGAs) and Multichip modules (MCMs) etc. In this paper, we give a brief overview of the state of control in smart structures. Different aspects of the development of smart structures such as applications, technology and theoretical advances especially in the area of control systems design and implementation will be covered.

The piezoelectric materials, as the most widely used functional materials in smart structures, have many outstanding advantages for sensors and actuators, especially in vibration control and energy harvesting, because of their excellent mechanical-electrical coupling characteristics and frequency response characteristics. Semi-active vibration control based on state switching and pulse switching, have been receiving much attention over the past decade because of several advantages. The technique is based on a nonlinear processing of the voltage delivered by the piezoelectric elements. This process increases the amount of electrically converted energy during a mechanical loading cycle of the piezoelectric element. A new approach for energy harvesting from mechanical vibrations is also derived from the nonlinear approach based on Synchronized Switch Damping. The present research activities of vibration control and energy harvesting using piezoelectric elements and a nonlinear approach are introduced.

Extreme loading events such as blasts, impacts and earthquakes often lead to the partial or total collapse of reinforced-concrete structures, resulting in economic and human life losses. Civil engineers have therefore been seeking innovative materials and systems that would allow the design of resilient and smart structures that can withstand such catastrophic events. Recently, engineered cementitious composites (ECCs) and shape memory alloys (SMAs) have emerged as strong contenders in the production of smart and resilient structural systems. This paper examines recent research work into the performance of structural members produced with ECCs and/or SMAs for applications in new structures as well as in strengthening and retrofitting work. The constraints on wider implementation of these materials in structural applications are discussed. It is shown that the superior performance of SMA-reinforced ECC elements under static and dynamic loading could allow the development of novel resilient composites with exceptional impact performance to protect infrastructure of paramount importance for homeland security against explosive, dynamic and impact loading.

With the substantial increase in implementation of green technology across all sectors worldwide to overcome energy loss, attributes such as reliability, efficiency, productivity, and security become very crucial for a system. Especially with the integration of IoT and smart features into a system alongside the evolution of Internet, cybersecurity and privacy of an individual component should be taken into important consideration. A smart grid comprises wireless network components exposed to cyber-attacks, smart meters being one the most vulnerable part of an advanced metering infrastructure. An advanced metering infrastructure enables two-way communication for automatic meter readings (AMR) and transmits data through wireless network. To counter cyber-attacks afflicting the network of AMI and functioning of a smart meter, additional intrusion detection methods are implemented into the grid network. The review includes cybersecurity concerns associated with smart meters along with an in-depth insight to some major cyber-attacks and their aftermath.KeywordsCybersecurityCyber-attacks advanced metering infrastructure (AMI)Smart metersDenial-of-service (DoS)False data injection (FDI)Man-in-the-middle (MitM)

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.

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

The energy policies and environmental issues require novel solutions to generate electricity in a challenging and efficient way. The sustainable and reliable grid operations are related to demand management as well as generation. One of the most important requirements to build smarter grids is including smart metering to the power system. The smart grid is not only considered to provide essential energy infrastructure but also a key concept to increase the energy efficiency owing to control and management opportunities brought by communication features. The prominent technologies of smart meters enable operational equipment on the distribution network in addition to conventional metering operations. The load management approach that is defined with several terms as demand side management, demand side response, or demand control is required for the systematic management of loads on distribution networks. There is a wide variety of smart meters and operation structures are available in industry. The automatic meter reading (AMR) and advanced metering infrastructure (AMI) are the most widely known smart metering infrastructure. Although they are similar in many aspects, they differ in communication and metering processes. The network structures and gateway organisations used in smart metering will also be discussed in this presentation. Another outstanding device that is being widely integrated into the transmission and distribution networks is Phasor Measurement Units (PMUs). Although the PMUs are operated in wide networks of transmission lines, it is considered that they will be required to be used in medium voltage (MV) and low voltage (LV) in a short while. The contents of this presentation will cover the topics summarized above and their industrial and scientific application examples.

To unlock the lock of futuristic developments, nowadays shape memory alloys (SMAs) are acting as key by outnumbering the existing smart materials in view of new design competence, innovative techniques, enhanced technologies, and meeting the dire need according to the demand of ongoing scientific and industrial progress. Undoubtedly, it can be worthy to associate SMAs with the term polymorphism, as they possess unique capability to encapsulate multitudinous inherent characteristics under their name. Shape memory effect, superelasticity, and damping are there to name a few among many others, as prime indicators. The exhibition of these characteristics of SMAs is due to the transformation that takes place between austenite phase and martensite phase which is achieved either by temperature or stress variation. The fascinating characteristics they possess enable them to attract researchers and designers toward their potential applications in diverse domain as smart and multi-functional materials. The present work focuses on the review of research works accomplished in the recent 5 years pertaining to modeling and applications of shape memory alloys in distinct domains. Under the topic of modeling, a look into the research carried out on a variety of SMA structures—like functionally graded SMAs, SMA springs, porous SMAs, novel SMA actuators—is presented. In addition to this, the work carried out to represent SMAs with large strains and large rotations and to model polycrystalline SMAs is also covered. This is supplemented by application-oriented domains, each of which disseminates the attributes of SMAs that are self-sufficient to express what factors make SMAs more prominent. It is believed that the foregoing works comprehensively detailed in this review article will certainly lay a solid platform for the future investigations that are going to take place in time to come.