A proof of concept study on reliability assessment of different metal foil length based piezoelectric sensor for electromechanical impedance techniques.

Lead zirconate titanate (PZT) patches gained popularity in structural health monitoring (SHM) for its sensing and cost effective. However, a robust installation of PZT patches is challenging due to the often-complex geometry and non-accessibility of structural parts. For tubular structures, the curved surface can compromise the perfect bonding of PZT patches. To alleviate the above-mentioned challenges, the non-bonded and reusable configuration of sensor received considerable interest in the field of SHM. However, ensuring the repeatability and reproducibility of Electro-Mechanical Impedance (EMI) measurements is crucial to establish the reliability of these techniques. This work investigated the repeatability and reproducibility measures for one of non-bonded configuration of PZT patch i.e., Metal Foil Based Piezo Sensor (MFBPS). In addition, the concept, application, and suitability of MFBPS for impedance-based monitoring technique of Civil infrastructure are critically discussed. This study evaluates the effect of length of MFBPS on piezo coupled admittance signature. Also, this study evaluates repeatability and reproducibility of EMI measurements via statistical tools such as ANOVA and Gage R&R analysis. The statistical index CCDM was used to quantify the deviations of impedance signals. The overall result shows that the repeatability of the EMI measurements improves with a metal foil length of 500 mm. Overall, this investigation offers a useful point of reference for professionals and scholars to ensure the reliability of MFBPS for EMI techniques, a variant of piezoelectric sensor for SHM applications.

Experimental and Numerical Simulation of a Radiant Floor System: The Impact of Different Screed Mortars and Floor Finishings.

The radiant floor system market is growing rapidly because Europe is moving toward a low-carbon economy and increased awareness about environmental sustainability and energy efficiency, stimulated by the ambitious EU Energy Efficient Directive and nZEB challenge. The high growth rate of the market share is due to the involvement of homeowners in the specifications of their living commodities, so they are thus willing to invest more at the initial stage to obtain long-term benefits and lower energy exploration costs. We performed an experimental campaign over three slabs with a hydronic radiant floor system of equal dimensions, shape, and pipe pitch with different screed mortar formulations to assess their performance throughout a heating/cooling cycle. The temperature at different heights within the interior of the screed mortars and at the surface were monitored. The results revealed that an improved screed mortar has a relevant impact on the efficiency of the system. Moreover, a three-dimensional transient heat transfer model was validated using the experimental data. The model was used to evaluate the impact of different finishing materials, namely wood, cork, ceramic, and linoleum, on the floor surface temperatures. The results showed differences of 15% in the surface temperature when using different floor finishing solutions.

Multifunctional hybrid structures made of open-cell aluminum foam impregnated with cellulose/graphene nanocomposites.

This work focuses on exploring combinations of disintegrated bacterial cellulose nanofibres (BC) with graphene oxide (GO) (reduced and non-reduced) and phase change materials (PCMs) prepared in the form of foam-like structures. The presence of GO remarkable improves the fire-retardancy and provides dimensional stability to the foams while PCMs gives thermal energy storage capacity. The foams were exposed to methyltrimethoxysilane (MTMS) vapour to become hydrophobic which was confirmed by measuring water absorption capacity and water contact angle. To extend the multifunctionality of these nanocomposite foams, a selected composition was impregnated into an open-cell aluminium foam creating a hybrid structure (Al-BC/GO) with higher mechanical properties (increase in stress of 100 times) and high sound absorption coefficient (near 1 between 1000-4000 Hz). The low thermal conductivity confirms that this hybrid structure is a thermal insulator. These advantages highlight the potential applications of the proposed materials e.g. construction, automotive and aeronautical sectors.

Bacterial cellulose/graphene oxide aerogels with enhanced dimensional and thermal stability.

We present a novel method for processing bacterial cellulose/graphene oxide (BC/GO) aerogels with multifunctional properties. The addition of a small amount of dimethyl sulfoxide (DMSO) to the aqueous dispersion of the nanomaterials during the gelification process affected the water freezing temperature of the system and thereby affecting the porous structure of the aerogel obtained after liophilization. The possibility to obtain small and elongated pore with axial orientation allowed a significant improvement of the structural stability of the aerogels. Moreover, the aerogels reduction by thermal treatment with ammonia gas induced crosslinking between the different nanophases, thus given an incremental factor for the mechanical performance of the aerogels under harsh conditions. The resulting aerogels also showed significant improvements in terms of thermal stability and electrical conductivity. These multifunctional BC/GO aerogels present high potential as sustainable and ecological alternative materials for lightweight packaging, filters for atmosphere and water treatment, or energy applications.

Thermal Energy Storage and Mechanical Performance of Crude Glycerol Polyurethane Composite Foams Containing Phase Change Materials and Expandable Graphite.

The aim of this study was to enhance the thermal comfort properties of crude glycerol (CG) derived polyurethane foams (PUFs) using phase change materials (PCMs) (2.5⁻10.0% (wt/wt)) to contribute to the reduction of the use of non-renewable resources and increase energy savings. The main challenge when adding PCM to PUFs is to combine the low conductivity of PUFs whilst taking advantage of the heat released/absorbed by PCMs to achieve efficient thermal regulation. The solution considered to overcome this limitation was to use expandable graphite (EG) (0.50⁻1.50% (wt/wt)). The results obtained show that the use of PCMs increased the heterogeneity of the foams cellular structure and that the incorporation of PCMs and EG increased the stiffness of the ensuing composite PUFs acting as filler-reinforcing materials. However, these fillers also caused a substantial increase of the thermal conductivity and density of the ensuing foams which limited their thermal energy storage. Therefore, numerical simulations were carried using a single layer panel and the thermal and physical properties measured to evaluate the behavior of a composite PUF panel with different compositions, and guide future formulations to attain more effective results in respect to temperature buffering and temperature peak delay.

Analysis of the picosecond magneto-optical phenomena in scattering media of biological interest.

The behaviour of a magneto-optically active biological-like medium under picosecond optical excitation is analysed. The new technique is based on the fact that photons trapped in multiple scattering events inside the magneto-optical medium leave the medium with larger induced rotation angles, as they travel longer distances. Two- and three-dimensional displacements of the photons in the medium are separately analysed. The dependence of this effect on the applied magnetic field strength, the value of the magneto-optical constant of the medium and the standard deviation of the statistical distribution of the photons scattered inside the turbid medium are studied. The best values for the magnetic field and optical parameters of the biological medium are proposed for the experimental observation of the picosecond magneto-optical phenomena in scattering media of biological origin. We also make some prospective studies to evaluate the potential application of the magneto-optical effect as a tool for optical tissue biopsy. Values for the optimum magnetic field intensities and for the expected experimental sensitivity in diverse conditions are reported.