Smart Structures Research Research Articles

The contributions of Prof. Vicente Lopes Jr to smart structures research

The scientific career of Vicente Lopes Jr at UNESP—Ilha Solteira—spanned three decades in which he worked on new applications of smart structures in structural health monitoring and active vibration control. Prof. Lopes Jr. was one of the pioneers in Brazil for using smart materials and intelligent structures, having supervised several students during his career. This article is a tribute, due to his retirement, reviewing his scientific contribution and highlighting the importance to the Brazilian smart structures community.

ACTIVE-CONTRACTING VARIABLE-STIFFNESS FABRICS FOR SELF-FITTING WEARABLES.

Self-fitting is the ability of a wearable, garment or body-mounted object to recover the exact shape and size of the human body. Self-fitting is highly desirable for wearable applications, ranging from medical and recreational health monitoring to wearable robotics and haptic feedback, because it enables complex devices to achieve accurate body proximity, which is often required for functionality. While garments designed with compliant fabrics can easily accomplish accurate fit for a range of body shapes and sizes, integrated actuators and sensors require fabric stiffness to prevent drift and deflection from the body surface. This paper merges smart materials and structures research with anthropometric analysis and functional apparel methodologies to present a novel, functionally gradient self-fitting garment designed to address the challenge of achieving accurate individual and population fit. This fully functional garment, constructed with contractile SMA knitted actuator fabrics, exhibits tunable %-actuation contractions between 4-50%, exerts minimal on-body pressure (≤1333 Pa or 10 mmHg), and can be designed to actuate fully self-powered with body heat. The primary challenge in the development of the proposed garment is to design a functionally gradient system that does not exert significant pressure on part of the leg and/or remain oversized in others. Our research presents a new methodology for the design of contractile SMA knitted actuator garments, describes the manufacture of such self-fitting garments, and concludes with an experimental analysis of the garment performance evaluated through three-dimensional marker tracking.

Field-dependent nonlinear piezoelectricity: a focused review

ABSTRACTThis contribution presents a multidisciplinary review of the so-called field-dependent nonlinear piezoelectricity. It starts with an introduction that poses the literature analysis framework, through defining this operational (that is often met in practice) piezoelectric field-dependent nonlinearity. Indeed, the latter is a less known phenomenon although it is inherent to stress-free actuation responses of corresponding smart materials, actuators and structures. Then, related experimental observations from piezoelectric materials, actuator devices and smart structures tests are multidisciplinary surveyed for understanding the underlying mechanisms of the encountered field-dependent nonlinearity. Next, empirical material and numerical structural modelling and simulation approaches are critically reviewed from, respectively, the constitutive and finite element analysis points of view. Summary conclusions and few future directions for research are finally provided as a closure. It is worth mentioning that, although it is concise (retains only experiments and experimentally-correlated models and simulations), this critical review covers the last three decades period which is almost the whole age of the piezoelectric materials, actuators and smart structures research field.

Plastic Optical Fibre Sensors for Structural Health Monitoring: A Review of Recent Progress

While a number of literature reviews have been published in recent times on the applications of optical fibre sensors in smart structures research, these have mainly focused on the use of conventional glass‐based fibres. The availability of inexpensive, rugged, and large‐core plastic‐based optical fibres has resulted in growing interest amongst researchers in their use as low‐cost sensors in a variety of areas including chemical sensing, biomedicine, and the measurement of a range of physical parameters. The sensing principles used in plastic optical fibres are often similar to those developed in glass‐based fibres, but the advantages associated with plastic fibres render them attractive as an alternative to conventional glass fibres, and their ability to detect and measure physical parameters such as strain, stress, load, temperature, displacement, and pressure makes them suitable for structural health monitoring (SHM) applications. Increasingly their applications as sensors in the field of structural engineering are being studied and reported in literature. This article will provide a concise review of the applications of plastic optical fibre sensors for monitoring the integrity of engineering structures in the context of SHM.

Training by research - program of, and experiences in, the Smart Structures Research Training Network project

Smart Structures is a Marie Curie Research Training network (RTN) named “A Computer Aided Engineering Approach to Smart Structures Design”. The overall objective of the RTN is to develop an educational and research framework for developing macroscale noise control applications based on intelligent material systems. The scientific and technological objective of the network is to advance the state-of-the-art in smart materials research to the level of system integration and industrial applicability, with a specific focus on solutions for noise and vibration reduction and for vibration-based damage detection. The paper gives a short overview of the project partners' activity and summarizes the experiences of the researchers and their tutors after the first 18 months of the network.

DEVELOPMENT OF SMART STRUCTURE SYSTEMS FOR HELICOPTER VIBRATION AND NOISE CONTROL

Helicopters are susceptible to high vibratory loads, excessive noise levels and poor flight stability compared to fixed-wing aircraft. The multidisciplinary nature of helicopter structures offers many opportunities for the innovative smart structure technology to improve helicopter performance. This paper provides a review of smart structures research at the National Research Council Canada for helicopter vibration and cabin noise control applications. The patented Smart Spring approach is developed to vary the blade impedance properties adaptively to reduce the vibratory hub loads transmitted to the fuselage by vibration reduction at the source. A smart gearbox strut and active structural acoustic control technologies are investigated to suppress the vibration and tonal gear meshing noise into the cabin either by modifying the vibration load transmission path, or weakening the coupling between exterior and cabin acoustic fields. Two adaptive seat mount concepts are proposed to reduce the vibration of the aircrew directly to improve ride quality of the vehicle.

The future role of smart structure systems in modern aircraft

The paper intends to summarize some guidelines for future smart structure system application in military aircraft. This preview of system integration is based upon a review on approximately one and a half decades of application oriented aerospace related smart structures research. Achievements in the area of structural health monitoring, adaptive shape, adaptive load bearing devices and active vibration control have been reached, potentials have been identified, several feasibility studies have been performed and some smart technologies have been already implemented. However the realization of anticipated visions and previously initial timescales announced have been rather too optimistic. The current development shall be based on a more realistic basis including more emphasis on fundamental aircraft strength, stiffness, static and dynamic load and stability requirements of aircraft and interdisciplinary integration requirements and improvements of integrated actors, actuator systems and control systems including micro controllers.

Smart and designer structural material systems

AbstractAn efficient civil infrastructure system is essential to every country's productivity, security, and quality of life. Basic research and development in smart structures and designer materials have shown great potential for enhancing the functionality, serviceability, and increased lifespan of civil infrastructure systems. New construction and the intelligent renewal of ageing and deteriorating civil infrastructure systems include efficient and innovative use of high‐performance designer materials, sensors, actuators, and mechanical and structural systems. High‐performance designer materials, in particular, require new methods of computational materials science, some of which are described herein. In this paper, some examples of National Science Foundation (NSF) funded awards, some examples of National Institute of Standards and Technology (NIST) ‘designer material’ projects, and future research needs, as well as new research initiatives on nanotechnology, are presented.

An overview of smart technology

In recent years there has been a seemingly ever-increasing use of the synonymous adjectives 'smart' and' intelligent' to describe a diverse range of materials, structures, systems and technologies. The origin of this terminology can be dated to the early 1980s when researchers working mainly in the US, and funded predominantly from defence budgets, began to examine the potential of combining advanced materials and sensors with powerful and compact computers to produce futuristic systems able to monitor their operating environment in real time and respond appropriately. Public awareness of this technology was given an enormous boost by the prominence given to use of'smart' munitions during the Gulf war. Various articles appearing in popular science journals and broadsheet newspapers in the months following the successful conclusion of this conflict served to maintain interest and it became fashionable to examine the use of 'smart' technology in industrial applications far removed from those originally envisaged in aerospace and defence. Various dedicated university research groups were formed at around this time (among the first in the UK being the Smart Structures Research Institute at Strathclyde University), often bringing together academics who had been working on 'smart' technologies for several years without realising it! Over the last five years researchers working in most of the major industrial sectors have given at least some thought to how they might apply 'smart' technology, important areas being in transport, building, civil infrastructure, biomedicine, sport and leisure, power generation and oil, gas and petrochemical. Packaging has not been left out of this process, with the prospects for 'intelligent packaging' being assessed most notably by CEST and Pira International in a report prepared in 1992 under DTI funding. Interest in 'smart' packaging has been sustained over the four years since this pioneering study, with the focus of attention gradually shifting from abstract conjecture to practical application. Notwithstanding the attention now being devoted to all things 'smart', the underlying concepts are still only poorly understood in many quarters and the word must warrant some sort of prize for the proportion of times that it is inaccurately applied. This paper presents a systematic definition of 'smart' technology and goes on to review very briefly some of the major advances being made under this technological umbrella. The UK's Defence Research Agency (DRA), like its American counterparts, has been active in 'smart' technology from its earliest days and has, for obvious reasons, concentrated mainly on aerospace and defence applications. However, with the launch in April 1994 of the DRA's Structural Materials Centre (SMC), committed explicitly to promoting wealth creation via the dual (i.e. military and civil) use of technology, there has been a conscious effort to identify wider opportunities for the exploitation of the contributing 'smart' technologies. Some ideas relevant to packaging which are currently being developed in conjunction with the DRA's Packaging Authority are outlined, together with an invitation for interested companies to participate in various DRA-led joint development programmes.

Smart materials and structures: what are they?

There has been considerable discussion in the technical community on a number of questions concerned with smart materials and structures, such as what they are, whether smart materials can be considered a subset of smart structures, whether a smart structure and an intelligent structure are the same thing, etc. This discussion is both fueled and confused by the technical community due to the truly multidisciplinary nature of this new field. Smart materials and structures research involves so many technically diverse fields that it is quite common for one field to completely misunderstand the terminology and start of the art in other fields. In order to ascertain whether a consensus is emerging on a number of questions, the technical community was surveyed in a variety of ways including via the internet and by direct contact. The purpose of this survey was to better define the smart materials and structures field, its current status and its potential benefits. Results of the survey are presented and discussed. Finally, a formal definition of the field of smart materials and structures is proposed.

The importance of complementary assets in the development of smart technology

Smart technology covers a broad area of inquiry from complex devices utilizing optoelectronics and sensors for monitoring structural integrity to research into molecularly intelligent materials. Much smart technology is still embryonic, but promises considerable benefits in a wide range of industry sectors. Two years ago the first Smart Structures Research Institute was inaugurated at the University of Strathclyde, in Scotland, to stimulate the development of these new technologies in Europe. This paper explores the options for developing the technology within different industry sectors. The authors discuss the nature of ‘demand’ in innovation and demonstrate that an awareness of ‘complementary assets’ is important at a very early stage of the innovations process. The Institute's successes in bringing together partners in collaborative research, establishing a communication network and exploiting different public funding schemes at different stages of research are all important ways in which it has influenced the dynamics of innovation. The authors conclude that assessing the future prospects of a research institute must include a number of market and organisational issues as well as technical inputs, and that the process of assessment itself serves as a further influencing factor on future direction and focus.

Engineering research in composite and smart structures

The U.S. National Science Foundation (NSF) supports research in composite materials and smart structures in a number of NSF Directorates. NSF funding covers such areas as engineering, materials, physics, chemistry, computer sciences, education, bio- and geo-sciences, social, behavioral and economic sciences. Since World War II, significant amounts of basic research and technology have contributed to the long-range financial well-being of the country by the development of high-tech products. In this paper, discussions of NSF research projects in composite materials and smart structures are presented. The results of this research are intended to be part of the improvement in the Civil Infrastructure System (CIS), in the “clean car” and in improved safety and reduced costs of civilian aircraft and in better quality of life for all. Most of the cited examples are related to the CIS, clean car and improved aircraft just to keep the size of the report to a manageable level. Of course, several projects are generic and typical NSF-type research that is sufficiently basic as to be of use in these projects, but also have a wider application.