Papers by Keyword: Smart Material

Abstract: Nowadays, the demand for glass fibre-reinforced polymers (GFRPs) has increased in the industry owing to their low weight, high strength, corrosion resistance and low cost compared with other fibre-reinforced polymer composites. However, GFRP is anisotropic material with low interlaminar strength where the damage can occur without warning. Integrating a real-time damage detection process can mitigate this problem. Therefore, this paper presents the initial fabrication of an embedded capacitive sensor into the GFRP by using conductive electrodes inbetween its layers. To form the sensing electrodes, glass fibre yarns were coated with conductive material and braided into the fibregalss woven fabric. Two coating methods were considered to form embedded electrodes in this work which include aerosol spray coatings that were carbon based and gold-based physical vapour deposition, (PVD). It has been shown that spray coating has a weak bond and the carbon particles disperse during the molding process. In the PVD technique the nanoparticle (Au) distributed uniformly along the fibres and has a good resistance (≈100Ω). The capacitive sensor based on gold coating was exaimined using a three point bending test which demonstrate linear response toward the flexural load with a sensitivity of 25.1 fF/N.

Abstract: Self-healing composites are smart materials that can be fabricated through the dispersion of tubular nanofillers loaded with appropriate healing agents in a polymeric matrix. In this study, polysulfone (PSf) containing epoxy-loaded halloysite nanotubes (e-HNTs) were successfully fabricated via non-induced phase separation (NIPS) method at varying concentrations. Fourier Transform Spectroscopy (FTIR) analysis showed that epoxy (healing agent) and amine (hardener) were successfully loaded into the lumen of the HNT through the observed functional groups of the epoxy system along the HNT spectrum. The tensile strength of the loaded membranes compared to their unloaded counterpart slightly decreased due to the possible embrittlement of the unreacted epoxy. However, the membranes with epoxy-loaded HNTs garnered lower wettability on average due to the hydrophobic character of the epoxy system, which is a preferable trait for smart coatings. The self-healing capability of the membranes with 5% filler (loaded and unloaded) was investigated by scratch test and Scanning Electron Microscopy (SEM). The result revealed a high tendency of healing for the epoxy-infused nanocomposite film.

Abstract: Magnetorheological braking devices function due to the organization of domain structures between liquid and solid magnetic materials under the action of an electromagnetic or magnetic field. The disc is most widely used as a rotating braking element that made of a solid magnetic material due to the large area of contact with a magnetorheological fluid. Many factors affect the braking characteristics of the magnetorheological disc brake. Specifically, the value of the magnetic field and how the field is distributed across the work element is significantly affected at the braking torque. There are different ways to generate a magnetic field. In this study, the method of installation of permanent magnets into the construction, allowing to increase the braking torque of the magnetorheological disc brake is proposed. Simulation modelling showing the distribution of the magnetic field across the disk depending on the installation of permanent magnets with different pole orientations were carried out. The model takes into account the possibility of increasing the gap between solid magnetic materials of the structure, inside them which the magnetorheological fluid is placed. Comparative estimation of the distribution of the magnetic fields depending on the chosen method of installation of permanent magnets with different orientations of their poles is carried out. Further research is planned to focus on a comparative assessment of the distribution of magnetic fields depending on the selected material of the braking chamber.

Abstract: In the Li₂O-M₂O₅-TiO₂ system, Li_1+x-yM_1-x-3yTi_x+4yO₃ (M = Nb, or Ta, 0.06 ≤ x ≤ 0.33, 0 ≤ y ≤ 0.175 (LMT) forms a superstructure, known as smart material. The superstructure is formed by periodical insertion of a corundum-type intergrowth layer of [Ti₂O₃]²⁺ in a matrix having a trigonal structure during the grain growth. To apply this unique structure as a host material of phosphor, new phosphors doped with Mn⁴⁺ ion with a red emission colour, which had a broad peak around 685 nm excited by 493 nm. In order to improve the PL intensity, we investigated the compositions, Mn⁴⁺ ratio and crystal structure. Results showed that PL intensity was closely related to Mn⁴⁺ ratio and its crystal structure.

Abstract: Smart materials are discussed in architecture to transfer the state-of-the-art technology and expand the horizon of building performance. Although the effects of smart material applications in building design are discussed in literature and publications from the context of an autonomous responsive system and an environment-control device, the notion of sustainability assessment of smart materials is not comprehensively discussed yet. Researches on the energy simulation, life cycle cost assessment, thermal behavior evaluation, and daylight assessment have been developed for some specific materials. However, the sustainable performance of building is evaluated with criteria of region-based building sustainability assessment tools. Although smart materials in building may contribute to energy demand reduction and be considered as innovative technology with multiple values, currently available sustainability assessment tools would not allow the adequate evaluation of smart materials in buildings. Therefore, this research reviews the possibility to evaluate smart materials in major sustainability assessment tools – BREEAM, LEED, and CASBEE and proposes the assessment criteria to embrace a smart material application in architecture as an opportunistic smart approach toward sustainability of buildings.

Abstract: A Smart material can adapt to the external influences such as pressure, temperature, humidity, pH, electric or magnetic fields, an example is liquid crystal. Liquid crystal materials also can be applied for thermal mapping such as thermochromic liquid crystals (TLC) sheet. TLC sheet has a good response to the temperature changes which is shown by color play. This special characteristic of TLC can be used to explain some theoretical aspects of heat transfer on metals. The metals surface images during heating will be processed by converting the RGB images to the HSV images and then applied an edge detection method on hue images. From the thermal visualization, it can be shown that the largest heat exchange to the environment occurs at metal edges, so it is necessary to apply the heat insulator during the process of collecting data in block calorimeter experiments. The brass metal has the highest heat transfer rate, followed by copper and brass. It corresponds to the specific heat (c) of metals which c_steel>c_copper>c_brass. Furthermore, it can be shown that since the heat starts to be evenly distributed until 300 seconds, the increasing of metals temperature is obtained ∆T_steel<∆T_copper<∆T_brass and the increasing of mean hue (∆_mean-hue) are obtained ∆_{mean-hue(steel)}<∆_{mean-hue(copper)}<∆_{mean-hue(brass)}. This result can be used to explain that in block calorimeter experiments, the measurement should be carried out after several minutes to obtain the even heat distribution across the entire metal surface.

Abstract: During the last few years, synthetic self-healing materials have become a new class of emerging smart materials with the ability to repair damage and restore lost or degraded properties or performance using resources inherently available to the system. Success in the design of self-healing materials is important to material safety, product reliability and prolonged lifetime. This article covers fundamental material-independent principles and different self-healing approaches for polymeric materials. Among these approaches, some depend on specific external stimulus to achieve their goal while others regain the physical properties of the pristine material without such external intervention. Both the mechanisms and performance of different methods are discussed and evaluated, along with their advantages and disadvantages. In the end, both the potential application areas and the main challenges are also discussed in this article for a better understanding of future development trend of self-healing polymeric materials.

Abstract: Shape memory alloys (SMA) have been at the forefront of research in recent years. They have been used for a wide variety of applications in various fields. This work presents a brief study at the atomic scale of Cu-Al based Shape Memory Alloys. Using first-principles Density Functional Theory (DFT) method, the stability of different austenitic and martensitic phases of Cu₃Al, the effect of intrinsic vacancies, the doping effect by an element X (X = Be, Zn, Ti, Ni, Ag and Au) have been studied.

Abstract: The effects of thermo-mechanical training on damping capacity of two types of stainless steels, Fe-18Cr-8Ni (SUS 304) and Fe-25Cr-20Ni (SUS 310S) stainless steels, are studied. The thermo-mechanical training with bending deformation is adopted, since vibration manner in internal friction measurement is bending mode. An anisotropic damping capacity as well as hardness of samples is studied. It is found that deformation induced ε-martensite is observed for trained SUS 304 sample, while deformation twins are formed in the trained SUS 310S sample. It is also found that internal friction of SUS 304 sample is larger than that of SUS 310S sample. Increase in number of training results in an increase in the internal friction and hardness. In addition, anisotropic damping capacity is observed in the samples subjected the thermo-mechanical training. To be concluded, the thermo-mechanical training is useful for enhancement of both damping capacity and strength of SUS 304 and SUS 310S stainless steels.

Abstract: In this study, Polyvinylidene fluoride (PVDF) ultrafine fibers was fabricated by electro spinning equipment using rotating collector drum with different weight percentage of multi-walled carbon nanotube (MWCNT). The fabricated PVDF-MWCNT fiber has embedded to a glass fiber reinforced polymer (GFRP) for structural health monitoring of composite structures. GFRP is non-conductive material. However, by adding (or) embedding conductive PVDF-MWCNT nanocomposites, measuring its relative electrical resistance can be achieved. This study assesses the use of piezo resistive effect and conductivity of carbon nanotubes (CNT) for in-suit measurement of electrical resistance measurements and strain measurement of carbon fiber are correlated for sensing and damage monitoring purpose. The PVDF-MWCNT fiber and PVA-MWCNT fiber embedded in GFRP were evaluated and compared. Its first time PVDF-MWCNT fiber is used in composite material for sensing the damages; hence embedded sensor will downgrade the fatigue life of the composite structures usually, but in this investigation PVDF-MWCNT focus on not to downgrade the material’s mechanical properties. The manufactured specimens were subjected to various incremental loading and unloading tensile test. During mechanical loading and unloading processes the corresponding electrical resistance was monitored simultaneously, to assess the damage level in the structure.