Influence of out-of-plane fiber waviness and different environmental conditionings on mechanical and morphological characteristics of fiber glass/epoxy laminates

The use of structural polymeric composites constitutes an interesting option in the area of wind turbine blade manufacturing. Nevertheless, thick composite components may present out-of-plane waviness in their fibers, compromising the service life of the wind blades. In this context, the present study aims to study the influence of out-of-plane waviness in the fibers with different degrees of severity as well as to verify the effect of fiber glass/epoxy resin composites immersion in distilled water and saline solution in their tensile strength (σmax), modulus of elasticity (E), and deformation at break (єrup), analyzing the reinforcement/matrix interface changes. The results showed that the increase in severity promoted, in general, a statistically significant deterioration in σmax of the samples exposed to the same environmental conditioning. The conditioning led to a decrease in E and an increase in єrup, attributed to the deterioration of the interface and the plasticization of the polymeric matrix, respectively, as evidenced by fractographic analysis. The effect of severity on the єrup and σmax properties was only noticed in laminates exposed to environmental conditioning, due to water sorption favoring the deterioration of the matrix/reinforcement interface, intensifying the deleterious effect of out-of-plane waviness of fibers.

Systematic experimental comparison of particle filtration efficiency test methods for commercial respirators and face masks

Respirators, medical masks, and barrier face coverings all filter airborne particles using similar physical principles. However, they are tested for certification using a variety of standardized test methods, creating challenges for the comparison of differently certified products. We have performed systematic experiments to quantify and understand the differences between standardized test methods for N95 respirators (NIOSH TEB-APR-STP-0059 under US 42 CFR 84), medical face masks (ASTM F2299/F2100), and COVID-19-related barrier face coverings (ASTM F3502-21). Our experiments demonstrate the role of face velocity, particle properties (mean size, size variability, electric charge, density, and shape), measurement techniques, and environmental preconditioning. The measured filtration efficiency was most sensitive to changes in face velocity and particle charge. Relative to the NIOSH method, users of the ASTM F2299/F2100 method have commonly used non-neutralized (highly charged) aerosols as well as smaller face velocities, each of which may result in approximately 10% higher measured filtration efficiencies. In the NIOSH method, environmental conditioning at elevated humidity increased filtration efficiency in some commercial samples while decreasing it in others, indicating that measurement should be performed both with and without conditioning. More generally, our results provide an experimental basis for the comparison of respirators certified under various international methods, including FFP2, KN95, P2, Korea 1st Class, and DS2.

Assessing Urban Landslide Dynamics through Multi-Temporal InSAR Techniques and Slope Numerical Modeling

Landslides threaten more than before the urbanized areas and are a worldwide growing problem for the already affected communities and the local authorities committed to landslide risk management and mitigation. For this reason, it is essential to analyze landslide dynamics and environmental conditioning factors. Various techniques and instruments exist for landslide investigation and monitoring. Out of these, Multi-temporal Synthetic Aperture Radar Interferometry (MT-InSAR) techniques have been widely used in the last decades. Their capabilities are enhanced by the availability of the active Sentinel-1 mission, whose 6-day revisiting time enables near real-time monitoring of landslides. Interferometric results, coupled with ground measurements or other approaches such as numerical modeling, significantly improve the knowledge of the investigated surface processes. In this work, we processed the C-band SAR images of the available European Space Agency (ESA) satellite missions, using MT-InSAR methods to identify the surface deformations related to landslides affecting the Iași Municipality (Eastern Romania). The results (i.e., velocity maps) point out the most active landslides with velocities of up to 20 mm/year measured along the satellite Line of Sight (LOS). Following, we focused on the most problematic landslide that affects the Țicău neighborhood and is well-known for its significant implications that it had. To better understand its behavior and the sensitivity of the displacements to the environmental factors (i.e., rainfall), we carried out 2D numerical modeling using a finite difference code. The simulated displacement field is consistent with the InSAR displacements and reveals the most active sectors of the landslide and insights about its mechanism.

Numerical Optimization of a Single Bunch of NiTi Wires to be Placed in an Elastocaloric Experimental Device: Preliminary Results

Italy has not yet presented to the scientific community any elastocaloric prototype suitable for refrigeration/air conditioning. The SUSSTAINEBLE project was born from the idea to build a demonstrative elastocaloric prototype for environmental conditioning. The prototype is planned to be rotary and composed by a few bunches of elastocaloric wires crossed by air as heat transfer fluid. Many are the parameters to be investigated before the realization of the device. A numerical practical tool would help to easily optimize the prototype. In this paper a two-dimensional tool of a single bunch of elastocaloric wires based on finite-element method is introduced; it can reproduce step by step the velocity and the pressure field of fluid to predict more accurately the solid-to-fluid heat exchange. The results of a test campaign mostly focused on the optimization of the frequency of the cycle, fluid velocity and the distance between the elastocaloric wires are presented. The results reveal that: (i) 0.12 Hz as frequency; (ii) 7 m s−1 as velocity; (iii) 1.0 mm as optimal wire distance, would better satisfy the trade-off existing in the maximization of temperature span and cooling power per mass unit: 23.7 K and 311.97 W kg−1 are the values achieved, respectively.

Tensile Fatigue Behavior of Polyester and Vinyl Ester Based GFRP Laminates—A Comparative Evaluation

Fatigue loading is critical to fibre reinforced polymer composites due to their anisotropic and heterogenous nature. This study investigated the tensile fatigue behaviour of polyester and vinyl ester based GFRP laminates to understand the critical aspects of failure mode and fatigue life under cyclic loading. GFRP laminates with two different resin systems (polyester and vinyl ester), two different stress ratios (0.1 and 0.5) and two different environmental conditions (air and water) were investigated at an applied stress of 80%, 60%, and 40% of the ultimate capacity. Based on the investigated parameters (i.e., resin types, stress ratio, environmental conditioning, and maximum applied stress), a fatigue model was proposed. Results show that the resin system plays a great role in fatigue failure mode while the stress ratio and environmental condition significantly affect the tensile fatigue life of GFRP laminates. The types of resin used in GFRP laminates and environmental conditions as input parameters in the proposed fatigue model are a unique contribution.

Housing Energy Equivalence: A Graphical Approach

All buildings, even the most passive, need active energy to provide habitability. Apart from heating and cooling needs, which have been broadly studied and regulated, a significant percentage of the energy consumed in housing is due to home appliances. Furthermore, this value is increasing as the design of environmental conditioning becomes more efficient. The objective of this paper is to visualize the impact of these consumptions by a graphical equivalence that uses drawing to represent the surface area of photovoltaic modules that correspond to the energy demand. With this aim, a straightforward method is proposed based on graphical means that fit well with the working practice of architects. The procedure starts by detailing the energy consumption of a home, focusing on the consumption values of all appliances and lighting. Next, each single value is converted into the surface area of photovoltaic modules required to produce this energy in one year. Finally, each appliance and its corresponding energy production area are represented graphically side by side, resulting in the housing energy equivalence. This method has been tested by a group of architecture master's students using their own homes as the case study. The results show that the energy equivalent surface area for lighting and appliances represents between 8% and 46% of the floor area of their homes. Altogether, this approach makes visible a pending question in sustainable building design − the consumption of electrical home appliances − and provides rough graphical data which is useful for pre-dimensioning in the architectural design process.

INTERNALISASI NILAI-NILAI KARAKTER RELIGIUS SISWA DI MADRASAH IBTIDAIYYAH NURUSSALAM MANTINGAN

This study aims to determine the madrasah strategy in internalizing the values of religious character to students. The type of research the writer uses is descriptive qualitative research, with data collection techniques using in-depth interviews, documentation and participatory observation. Data analysis techniques in this study used data reduction, data presentation and data verification. The internalization stage or inculcation of religious character values for classes 1-2 MI Nurussalam is at the value transformation stage, classes 2 (process) and 3 are at the value transaction stage, while classes 4, 5 and 6 MI are at the value trans-internalization stage. MI Nurussalam's strategy in internalizing the values of religious character is divided into two fields, namely the academic and non-academic fields. The strategy in the academic field of MI Nuruusalam is to develop the Madrasah curriculum from grade 1 to grade 6 by adding special Islamic subjects and fostering a love affair with Arabic (the key to opening Islamic insights). In the non-academic field, MI Nurussalam integrates religious character values into routine activities, spontaneous activities, exemplary activities, and the Madrasah environmental conditioning system.