Smart Materials and Structures Highlights of 2014 Editor-in-Chief: Professor C Lynch, UCLA, USA w ww ISSN 0964-1726 Dear Colleague, SmartMaterials andStructures Systems from nano-to macroscale 2014 was another successful year for our journal, Smart Materials and Structures, which achieved its highest ever Impact Factor of 2.449. Volume 23 Number 1 January 2014 To recognise some of the outstanding work of our authors, we have put together this collection of articles, which were selected based on their popularity with our readers and referees, as well as the international press. If you would like to find out more about Smart Materials and Structures and read the full-text versions, please go to iopscience.org/sms. iopscience.org/sms Natasha Leeper Publisher IMPACT FACTOR Smart Materials and Structures 2.449* *As listed in the 2013 ISI Journal Citation Reports® Plastic and transformation interactions of pores in shape memory alloy plates Pingping Zhu1, Aaron P Stebner2 and L Catherine Brinson1 1 Mechanical Engineering, Northwestern University, Evanston, USA 2 Mechanical Engineering, Colorado School of Mines, Golden, USA Artificial linear superposition result of two pores from the single-pore simulation results: (left) axial stress and (right) transverse stress. Abstract A three-dimensional constitutive model for shape memory alloys (SMAs) is developed along the lines of the Stebner–Brinson (SB) implementation of the Panico–Brinson model. Plastic kinematic hardening behavior is simulated in addition to elastic deformation and phase transformation. A series of finite element simulations is carried out using this model to investigate the localization effects of the stress and strain field on NiTi plates with structured arrays of pores. The application of this model on porous architectures provides insight into how geometric features influence the mechanics of the structure. The incorporation of plastic deformation shows a marked decrease in the maximum stress levels; these results are more consistent with experimental Referee reward programme data as compared to the original SB model. Furthermore, the new results IOP Publishing has introduced a new referee reward demonstrate that clustered pores lead to more distributed stresses and programme offering referees a 10% credit towards transformation compared to a dispersed configuration of pores, indicating the importance of pore geometry in determining the stress and strain distribution. the cost of publishing on a gold open access The improved model provides a practical tool toward design and optimization of basis. To find out more, visitioppublishing.org/ porous SMA structures. newswire/questions-and-answers-for-referees. 2014 Smart Mater. Struct. 23 104008 iopscience.org/sms Smart Materials and Structures: Highlights 2014 1 were measured. We examined the high variance in mechanical properties Flexible piezoelectric energy harvesting from statistically and demonstrated that ring sections excised from the same trachea exhibit comparable mechanical properties. Our results will form the basis jaw movements for future studies aimed at determining the structure–function relationship of insect tracheal tubes, ultimately inspiring the design of multi-functional Aidin Delnavaz and Jérémie Voix materials and structures. Mechanical Engineering Department, École de technologie supérieure (ÉTS), 2014 Smart Mater. Struct. 23 057001 Montreal, Canada Schematic of the American cockroach Abstract and the four main thoracic tracheal trunks (a) top view (b) cross section. Piezoelectric fiber composites (PFC) represent an interesting subset of smart materials that can function as sensor, actuator and energy converter. Despite their excellent potential for energy harvesting, very few PFC mechanisms have been developed to capture the human body power and convert it into an electric current to power wearable electronic devices. This paper provides a proof of concept for a head-mounted device with a PFC chin strap capable of harvesting energy from jaw movements. An electromechanical model based on the bond graph method is developed to predict the power output of the energy harvesting system. The optimum resistance value of the load and the best stretch ratio in the strap are also determined. A prototype was developed and tested and its performances were compared to the analytical model predictions. The proposed piezoelectric strap mechanism can be added to all types of head-mounted devices to power small-scale electronic devices such as hearing aids, electronic hearing protectors and communication earpieces. 2014 Smart Mater. Struct. 23 105020 Smart fabric sensors and e-textile technologies: a review Lina M Castano and Alison B Flatau Department of Aerospace Engineering, University of Maryland, College Park, Jaw movement energy harvester. USA Abstract This paper provides a review of recent developments in the rapidly changing and advancing field of smart fabric sensor and electronic textile technologies. It summarizes the basic principles and approaches employed when building Variation in the mechanical properties of fabric sensors as well as the most commonly used materials and techniques tracheal tubes in the American cockroach used in electronic textiles. This paper shows that sensing functionality can be created by intrinsic and extrinsic modifications to textile substrates Winston R Becker, Matthew R Webster, John J Socha and Raffaella De Vita depending on the level of integration into the fabric platform. The current work demonstrates that fabric sensors can be tailored to measure force, pressure, chemicals, humidity and temperature variations. Materials, connectors, fabric Virginia Tech, Blacksburg, USA circuits, interconnects, encapsulation and fabrication methods associated with fabric technologies prove to be customizable and versatile but less robust Abstract than their conventional electronics counterparts. The findings of this survey The insect cuticle serves the protective role of skin and the supportive role of suggest that a complete smart fabric system is possible through the integration the skeleton while being lightweight and flexible to facilitate flight. The smart of the different types of textile based functional elements. This work intends to design of the cuticle confers camouflage, thermo-regulation, communication, be a starting point for standardization of smart fabric sensing techniques and self-cleaning, and anti-wetting properties to insects. The mechanical behavior e-textile fabrication methods. of the internal cuticle of the insect in tracheae remains largely unexplored due to their small size. In order to characterize the material properties of insect 2014 Smart Mater. Struct. 23 053001 tracheae and understand their role during insect respiration, we conducted tensile tests on ring sections of tracheal tubes of American cockroaches (Periplaneta americana). A total of 33 ring specimens collected from 14 tracheae from the upper thorax of the insects were successfully tested. The ultimate tensile strength (22.6 ± 13.3 MPa), ultimate strain (1.57 ± 0.68%), elastic modulus (1740 ± 840 MPa), and toughness (0.175 ± 0.156 MJ m−3) 2 Smart Materials and Structures: Highlights 2014 iopscience.org/sms state. In addition, the foldability still allows for fabrication by a flat lamination Flexible pressure sensors for smart process, similar to methods used for conventional expanded two dimensional cellular materials. This article presents the geometric characteristics of the protective clothing against impact loading structure together with corresponding kinematic and mechanical modeling, explaining the orthotropic elastic behavior of the structure with classical Fei Wang, Bo Zhu, Lin Shu and Xiaoming Tao dimensional scaling analysis. Institute of Textiles and Clothing, The Hong Kong Polytechnic University, 2014 Smart Mater. Struct. 23 094012 People’s Republic of China Cellular structure actuated Abstract by differentially pressurizing The development of smart protective clothing will facilitate the quick detection two sets of tubes in x and y directions. of injuries from contact sports, traffic collisions and other accidents. To obtain real-time information like spatial and temporal pressure distributions on the clothing, flexible pressure sensor arrays are required. Based on a resistive fabric strain sensor we demonstrate all flexible, resistive pressure sensors with a large workable pressure range (0–8 MPa), a high sensitivity (1 MPa−1) and an excellent repeatability (lowest non-repeatability ±2.4% from 0.8 to 8 MPa) that can be inexpensively fabricated using fabric strain sensors and biocompatible polydimethylsiloxane (PDMS). The pressure sensitivity is tunable by using elastomers with different elasticities or by the pre-strain control of fabric strain sensors. Finite element simulation further confirms the sensor design. The simple structure, large workable pressure range, high sensitivity, high flexibility, Three-dimensional microstructural facile fabrication and low cost of these pressure sensors make them promising candidates for smart protective clothing against impact loading. investigation of high magnetization 2014 Smart Mater. Struct. 23 015001 nano–micro composite fluids using x-ray microcomputed tomography T Borbáth1,2, I Borbáth2, S Günther1, O Marinica3, L Vékás4 and S Odenbach1 1 Technische Universität Dresden, Institute of Fluid Mechanics, Germany 2 Roseal Corporation, Odorheiu Secuiesc, Romania 3 ‘Politehnica’ University of Timisoara, Center for Engineering of