Papers by Keyword: Smart Composites

Abstract: Smart materials technologies are most significant in 21st-century. "Smart Materials" shall have a crucial role in construction technology. These innovative materials constitute an important part of smart building systems that shall be capable to detect its surrounding, so that the smart materials behave similar to living systems. The design of smart materials involves highly integrated components and requires interdisciplinary knowledge. Smart materials, are capable of adapting to their exterior surrounding. They alter their properties by applying exterior physical stimuli and thus adapt to their external environment in best possible manner. In the process of adapting to their external environment they involve various energy conversion processes. Thus mechanical energy is converted into electrical energy and vice versa by smart materials during their functioning. Smart materials are therefore predetermined and predesigned to perform as sensors and actuators as the need be. This paper discusses various types of smart materials available, their characteristics and applications in smart infrastructure.

Abstract: Three phase composites that consists of piezoelectric and piezomagnetic fibers embedded inan elastic matrix phase exhibits new product properties such as magnetoelectric effect, pyroelectric andpyromagnetic effect, which are absent in individual phases. In this work, simple analytical expressionsare developed based on strength of materials approach to find these effective coupling coefficients. In amicro scale rectangular representative volume element (RVE) of a layered type three phase composite,series connectivity is assumed between fiber and matrix layers along transverse direction and parallelconnectivity is assumed along longitudinal direction. The analytical model is validated with otherhomogenisation methods and effective property variation of BaTiO₃-CoFe₂O₄-Epoxy composite andLiNbO₃-CoFe₂O₄- Epoxy composite are discussed.

Abstract: Due to an increasing use of composite materials in various applications and related open questions concerning structural health monitoring and damage detection, the realisation of function integrating lightweight structures with sensory properties is subject of numerous research activities. Main objective is the transfer of already in laboratory and prototype scale established methods for the integration of sensory elements on serial applications. Here, combining the previously separated processing steps sensor manufacturing, component manufacturing and sensor integration can help to make a significant step forwards. Therefore, as part of the activities in the Collaborative Research Centre/Transregio (CRC/TR) 39, a highly productive spray coat method based on the long fibre injection (LFI) process is developed, which allows the process-integrated manufacturing and embedding of novel piezoelectric sensor modules into fibre-reinforced polyurethane composite structures.Based on studies on the technological implementation of the newly developed process, theoretical and experimental studies for contacting and polarisation of the novel sensor elements are presented. In addition, the characterisation of the adhesion properties of thermoplastic films on the used fibre-reinforced polyurethane composites is part of the presented research to evaluate the possibility of integrating thermoplastic-compatible piezo modules for actuator applications.

Abstract: The material development is aimed at utilizing a suitable Metal Alloy in combination with a most appropriate plastic material considering the achievement of desirable basic features of Smart materials like Shape Memory Effect, Flexibility, recovery time etc. In the present work shape memory composites were developed using Ni-Ti alloy as reinforcement into the epoxy matrix. To understand the recovery and the influence of the Young’s modulus of the matrix, three different combinations of epoxy and hardeners are used. This experiment has considered different combinations of Ni-Ti SMA wire spacing, Ni-Ti SMA wire orientations and Epoxy Mix proportions. The experiments are designed based on ‘Taguchi’s’ L9 orthogonal arrays. ‘Taguchi’s’ method combined with S/N ratio of analysis is used as the statistical tool for optimization of the most recommendable combination of the newly developed SMA polymer composite material. This is due to the special intention of finalizing the most advantageous product in view of physical properties, percentage shape recovery, recovery time etc.

Abstract: In this paper, preliminary investigation of a new cement-sand based piezoelectric composite was conducted for potential structural engineering applications. PZT ceramic powder has been incorporated into cement material to form composite smart materials in earlier studies and showed promising outcome. However, the previous studies were limited to using only PZT and cement. In this study, PZT powder mixed with cement and sand, which is more realistic in civil engineering applications. The compressive strength of the composites with different PZT volume ratios was investigated. The results showed that embed PZTs increased the strength of the composites. Modified Sawyer-Tower circuit was applied to pole the composites in order to obtain the desired electrical properties of the composites. The mechanical and electrical properties of this type of new smart material had been investigated experimentally. Through a series of MTS compression tests, feasibility of using cement-sand based PZT composite materials in civil engineering is evaluated.

Abstract: The present paper describes the development of a genetic algorithm (GA) based methodology for determination of optimal number of actuators and their locations in smart fiber reinforced polymer composite shell structures. Finite element (FE) based state space representation of the system has been used to determine the optimal placement of actuators in order to maximize the controllability. Spillover from residual modes has also been considered while maximizing controllability. Even though the developed methodology needs a large computational time, it will be useful in off-line determination of optimal actuators locations in large structures.

Abstract: Shape memory alloys (SMA) are thermo-responsive materials where deformation can be induced and recovered through temperature changes. Therefore, SMA are considered smart materials. In this work, an epoxy beam reinforced by NiTi SMA wires was developed. This active composite contains five pre-trained NiTi SMA wire actuators, evenly distributed along the neutral plane of the epoxy beam, which can be activated by resistive heating. The results of different ways for electrical activation of the smart composite in a simply clamped mode are discussed. It was possible to demonstrate the viability of this concept for attenuation of mechanical vibrations by controlled electrical heating of the NiTi wire actuators.

Abstract: Dielectric elastomers (DEs) could be considered as a new type of transducers. They can convert electrical and mechanical energies in a bi-directional manner. In this work, the electromechanical behavior of a DE diaphragmatic generator was investigated. Circular diaphragms were fabricated using a prestretched DE film sandwiched between laminates of compliant electrodes. A special chamber was used to apply pressure. Pressure-Volume characteristics of diaphragms were measured to calculate elastic energy density. DC voltages were applied to the electrodes and the generated voltages were measured. It was concluded that efficiency of generators was strongly dependent on the amount of biased voltage, pre-straining level and applied pressures.

Abstract: The method of generating the most practicable shape recovery force in smart composite materials which embedded shape-memory alloy (SMA) fiber under the resin matrix is electric heating. However, because the calorie for the heating of the resin matrix increases in the low temperature environment, it is necessary to control the electric heating corresponding to an ambient temperature to obtaining a steady shape recovery force. Then, the method of self-detecting the temperature without using a special temperature sensor by measuring the electrical resistance of the SMA fiber in the composite material was examined.