Experimental Assessment Research Articles

Optical Fibers Use in On-Chip Fabry–Pérot Refractometry to Achieve High Q-Factor: Modeling and Experimental Assessment

This paper investigates the integration of optical fibers into an on-chip Fabry–Pérot (FP) resonator to achieve high-quality (Q) factors, which is favorable in sensing applications. Initially designed for high-speed data transmission, optical fibers are now utilized in sensing applications because of their flexibility and sensitivity to optical phenomena. This article focuses on the role of single-mode fibers (SMF) and the geometry of different structures in enhancing light confinement within FP resonators. Two distinct on-chip designs utilizing SMFs are demonstrated, modeled, and experimentally evaluated. One achieves a Q-factor higher than 5200, demonstrating significant improvement in light confinement, while the other maximizes the spectral range between the resonant modes’ peaks, maximizing the sensing range through the wavelength shift. This is supported by visualized simulation and coupling efficiencies calculations for fundamental and higher-order modes for comprehensive analysis. Comparison with existing literature is also made, underscoring the advancements achieved by the presented approaches. The findings contribute to the development of microscale refractive index sensing applications, highlighting the vital role of optical fiber integration for high-performance sensing.

Sim-to-real transfer of adaptive control parameters for AUV stabilisation under current disturbance

Learning-based adaptive control methods hold the potential to empower autonomous agents in mitigating the impact of process variations with minimal human intervention. However, their application to autonomous underwater vehicles (AUVs) has been constrained by two main challenges: (1) the presence of unknown dynamics in the form of sea current disturbances, which cannot be modelled or measured due to limited sensor capability, particularly on smaller low-cost AUVs, and (2) the nonlinearity of AUV tasks, where the controller response at certain operating points must be excessively conservative to meet specifications at other points. Deep Reinforcement Learning (DRL) offers a solution to these challenges by training versatile neural network policies. Nevertheless, the application of DRL algorithms to AUVs has been predominantly limited to simulated environments due to their inherent high sample complexity and the distribution shift problem. This paper introduces a novel approach by combining the Maximum Entropy Deep Reinforcement Learning framework with a classic model-based control architecture to formulate an adaptive controller. In this framework, we propose a Sim-to-Real transfer strategy, incorporating a bio-inspired experience replay mechanism, an enhanced domain randomisation technique, and an evaluation protocol executed on a physical platform. Our experimental assessments demonstrate the effectiveness of this method in learning proficient policies from suboptimal simulated models of the AUV. When transferred to a real-world vehicle, the approach exhibits a control performance three times higher compared to its model-based nonadaptive but optimal counterpart.

Robust prediction models for flow and compressive strength of sustainable cement grouts for grouted macadam pavement using RSM

This study investigates the utilization of pumice stone ash in cementitious grouts for grouted macadam pavement, aiming to enhance flowability and compressive strength. Partial replacement of ordinary Portland cement (OPC) with varying percentages (5–20 %) of powdered pumice stone (PPS) ash was explored, alongside adjustments in water-to-cement (w/c) ratios. Experimental assessments, including flowability tests and compressive strength evaluations, were conducted on fresh and hardened grouts. Response surface methodology (RSM) and ANOVA analysis were employed to analyze the relationship between pumice stone ash content, w/c ratio, flow, and compressive strength. The results show that increasing the PPS content from 0 % to 20 % led to an increase in flow time from 23.6 to 34 seconds at a 0.3 w/c ratio, from 9 to 19 seconds at a 0.35 w/c ratio, and from 7 to 14 seconds at a 0.40 w/c ratio: indicating reduced flowability of the grouts. The 7-day compressive strength increased by approximately 2–17 % when 5–15 % of the cement was replaced with PPS, but a reduction occurred at 20 % PPS. Similarly, the 28-day compressive strength increased by about 4–23 % with 5–15 % PPS, while 20 % PPS led to a decrease in strength. The results highlight specific combinations of pumice stone ash content and w/c ratios, particularly 10 % PPS at 0.35 w/c and 15 % PPS at both 0.35 and 0.40 w/c, that meet grouted macadam standards, balancing flowability and strength. Fit statistics demonstrate the reliability of the predictive model. Optimization aims to maximize pumice stone ash content and w/c ratio, with graphical representation indicating an optimal composition at 17.25 % PPS and 0.35 w/c ratio for efficient grouted macadam construction. Additionally, Significant contribution towards sustainability can be achieved by replacing cement with pumice stone ash in pavement construction.

Recovery of carboxylic acids from actual effluent by using sequential cationic-anionic adsorption steps at semi pilot scale

This work presents for the first time an exhaustive experimental assessment at semi-pilot scale for the sequential use of cationic-anionic adsorption columns for recovering carboxylic acids (CAs) from a real fermentation broth. The consecutive steps were dedicated to i) remove cations limiting the CAs interaction with the functional group of the anionic resin, and ii) adsorb CAs onto the anionic resin, respectively. The experimental broth was obtained from anaerobic co-fermentation of urban biowaste (UBW-broth). Breakthrough (BT) tests were firstly performed with the cationic column containing the strong-acid resin Lewatit® S2568H. This allowed both to assess the single process and to prepare 60 L of decationised UBW-broth to be used in the BT-tests with the anionic column (containing the weak-basic resin Lewatit® A365). Both columns were assessed (at 25°C) under packed and expanded bed modes, by feeding at different rates the actual UBW-broth or synthetic solutions. Main study innovative outputs were: 1) 100 % of the CAs occurring in UBW-broth were recovered with the proposed system; 2) best performances were obtained under expanded bed mode of operation, allowing to use 100 % of the installed capacity; 3) the affinity of other organic matter else than CAs resulted weaker than Na+/NH4+ and CAs/PO4x-/Cl- in both cationic and anionic columns, respectively (i.e. low adsorption performances generally reported are due to inorganic cations/anions presence); 4) a very preliminary economic analysis carried out on the basis of the obtained data indicates overall costs ranging 0.58–1.49 EUR/kg of CAs (depending on the process configuration).

An experimental assessment of a solar PVT-PCM thermal management system in severe climatic conditions

Solar photovoltaic thermal (PVT) collectors incorporating phase change material (PCM) as an active-passive cooling approach represent a promising solution for thermally managing PV panels. This needs to be experimentally evaluated in harsh outdoor conditions. Therefore, this study examined the electrical and thermal performance of solar PVT systems in comparison to a reference PV panel during six distinct summer days in Riyadh, Saudi Arabia. A thermal camera was utilized to precisely capture the difference in temperature variations between the two PV panels over the study periods and to examine different options for the PVT collector. On Day 3, near noon, the highest solar irradiance of 1019 W/m2 led to the highest power of the PVT, with an increase of 5.75 % over the reference panel. The highest ambient temperature of 47.69 °C was recorded on Day 1 with 901.4 W/m2 irradiance, providing 10.58 % electrical efficiency of the PVT, an increase of 5.9 %. On Day 6, the PVT module was equipped with eight rectangular metal conduits that were filled with PCM with a transition temperature range of 41–48 °C. This simple-to-implement design added additional passive cooling for the system through the exterior surface of the metal conduits, along with the PCM contribution. The PTV-PCM option led to the best performance, with an 8.05 % improvement in electrical power and efficiency over the reference PV and 71.16 % and 81.50 % thermal and combined PVT efficiencies, respectively. The importance of cooling the PV panel in such challenging circumstances was illustrated by the 2 %–3.24 % increase in electrical output for every 1 °C decrease in the temperature of the cells.

Experimental assessment of hull, propeller, and the gate rudder system interaction in calm water and oblique waves

This study focuses on the experimental assessment of the EU H2020 Innovation Action project GATERS' target ship, a 7241 DWT multi-purpose dry cargo ship (M/V ERGE), scaled to 1/27.1, in calm water and oblique wave (at a yaw angle of the ship model) conditions. M/V ERGE was initially built with a Conventional Rudder System (CRS) in 2010 but was later retrofitted with a newly introduced energy-saving device, the Gate Rudder System (GRS), in 2023 as part of the GATERS project. In this project, the interaction of the GRS with the hull and propeller was investigated using model tests of the vessel in the Kelvin Hydrodynamics Laboratory's (KHL) towing tank at the University of Strathclyde (UoS) and compared to the CRS. The main objectives of these tests were threefold. While they aimed to make experimental contributions toward the establishment of the best procedure for estimating the powering prediction of a ship with the GRS, they also aimed to investigate the hull, propeller and rudder interaction for the CRS and GRS configurations. In addition, a set of comparative pilot tests were conducted in waves to explore the effect of the oblique waves on the vessel's performance with the CRS and GRS. The resistance and self-propulsion tests were performed for both the CRS and GRS configurations, and performance predictions based on the model tests were compared with sea trials. Furthermore, tests at a yaw angle of the ship model were conducted to evaluate the effect of waves on the vessel's performance with the CRS and GRS, simulating the in-service conditions of commercial ships. These tests were conducted in regular waves with the hull at a yaw angle to simulate oblique wave conditions, with a wave height of 1.25 m in full scale (corresponding to moderate breeze, Beaufort 4) for a range of wavelengths. Numerical analyses were performed to obtain the full-scale propeller open water characteristics. The paper demonstrates the superior interaction of the GRS with the hull and propeller in both conditions compared to the CRS configuration, even improving its contribution to the vessel's performance in oblique waves.

Experimental Assessment of Force Redistribution in Elements of Damaged Bridge Model under Temporary Load from Rolling Stock

The relevance of the work lies in the fact that properties of damaged structures were sufficiently studied. Therefore, there is a high risk of their unpredictable behavior, which can lead to malfunctions, including serious accidents and man-made disasters. The risk of such danger increases significantly in the extreme climate of Siberia and the North. Damage and destruction of structures are confirmed by many facts.Purpose: The aim of the work is to experimentally simulate the bridge bearing capacity after damage in order to understand how the bridge behaves in various conditions and what measures can be taken to restore it.Methodology: The finite element method and experimental modeling in the PASCO digital laboratory were used to determine forces in the truss rods.Research findings: The redistribution of forces in the rods of the superstructure was detected when some of its elements are out of operation, and critical destruction is identified.

Experimental assessment of counterfog bioaerosol fast sampler for virus detection and decontamination

The respiratory system is equipped with several defence mechanisms to protect the body from microorganisms and airborne pathogens. There are situations where the respiratory system can be overwhelmed or compromised and infection happens, especially in individuals with weakened immune systems. Airborne pathogens are a serious risk for human and animal health, as exemplified by the challenges faced during the COVID-19 pandemic. The list includes viruses of varying severity such as Influenza virus, SARS-CoV-2, measles virus, Varicella-Zoster Virus, or Respiratory syncytial virus among others. Smaller particles can remain suspended in the air for longer periods and may reach the lower respiratory tract, including the alveoli in the lungs. The real-time detection of these pathogens in the air presents a significant challenge. The aerosols, especially those carrying viruses, are so small that they often elude conventional air samplers, making it difficult both to detect their presence and to remove them effectively from the air. This work introduces a recent technique designed for rapid aerosol sampling, with a particular emphasis on virus sampling. The system underwent calibration using artificial ɸ29 virus aerosols and was subsequently tested with naturally emitted aerosols of SARS-CoV-2. A series of tests were conducted in diverse settings, including hospitals, farms, offices, and railway cars. The equipment is also capable of swiftly removing bioaerosols from the air, thereby facilitating effective decontamination. The relevance of this technology lies in its capability for swift detection and elimination of viruses and other kinds of aerosols from air, facilitating prompt decision-making during high-risk events.

Experimental assessment of strength characteristics of anthropogenic soils in a given mining area for justification of tractor propulsion type

BACKGROUND: In mining, there is a need to develop tractors as special robotic vehicles of the robotic mining facility that can efficiently move and work on soils with low bearing capacity, in waterlogged areas and in the underwater position. A preliminary evaluation of the strength characteristics of such a heterogeneous surface of the exploitation area helps to choose an effective concept and technical characteristics of the propulsor of the tractor. AIM: Formation of the database of the physical condition and mechanical properties of the environment in which the tractor will move and operate. METHODS: In order to achieve the aim, preliminary experiments were conducted on the terrain. Typical kinds of soil sites and watered areas, including those of anthropogenic origin, of a given mining area were identified. Full-scale instrumental tests were conducted to determine: granulometric composition of soils; physical and mechanical parameters of these soils at the selected sites using the developed original types of a penetrometer and a shear rig. RESULTS: The database of numerical values of measured strength characteristics of one of the soil types (as an example) as a possible supporting surface for vehicle motion in the area of mining facility operation is presented in a graphical form. The basis of this database is the graphs according to the results of experiments on free settlement and shear with the help of dies of two types of configuration (the round die and the original caterpillar track respectively); the granulometric composition of the selected soils has been evaluated. CONCLUSION: The methodology of preliminary assessment of the soil condition by two indicators of soil strength (the rut depth z depending on the average pressure under the die) and shear (average tangential stresses τ in the contact patch on the motion of the die relative to the soil, depending on the ratio of the normal force and the traction force in the contact plane) has been developed. The 3D model of the coastal and bottom area of the technogenic mining zone has been developed. Design variants of highly efficient types of tractor propulsors are selected on the basis of prediction of maximum allowable stresses in the contact patch with the ground for the bearing surface areas of the considered area of operation.

Catalytic gasification as a management strategy for wastes from pecan harvest

More than 60,000 tons of waste from Carya illinoinensis, known as pecan, are produced yearly in Mexico. Usually, these wastes are either open-cast disposed of or burned, causing environmental issues. An alternative to combustion is gasification, which transforms biomass into syngas and ash. Using a catalyst can improve the gasification reaction since it allows for better heat transfer in the reactor. In this work, a gasification process catalyzed by a clinoptilolite was evaluated as a method of pecan waste management. A fixed bed gasifier in batch mode with a reaction volume of 1 kg was considered. Gasification with 8 % zeolite presented the shortest reaction time (39 min) and the highest average flow of synthesis gas (0.779 m3/5 min). The environmental impact was evaluated through a life cycle assessment considering two scenarios: conventional and catalyzed gasification (2, 4, 6, and 8 % of zeolite). In the former, the gasification stage induces the largest potential impact (>95 %) in all the categories, and global warming is the most affected category (>90 %). In the second scenario, gasification (82 %) and zeolite production (16 %) stages are the main potential impact inducers; global warming is also the most affected category (85 %). Considering the experimentation and environmental assessment, gasification with 8 % zeolite was selected for the next stage. Regarding economic feasibility, it was found that a pilot-scale gasification processing 1000 kg of pecan waste becomes feasible if gas is either sold or used to produce electricity.

A-RFP: An Adaptive Residue Flexibility Prediction Method Improving Protein-ligand Docking Based on Homologous Proteins

Background: Computational molecular docking plays an important role in determining the precise receptor-ligand conformation, which becomes a powerful tool for drug discovery. In the past 30 years, most computational docking methods have treated the receptor structure as a rigid body, although flexible docking often yields higher accuracy. The main disadvantage of flexible docking is its significantly higher computational cost. Due to the fact that different protein pocket residues exhibit different degrees of flexibility, semi-flexible docking methods, balancing rigid docking and flexible docking, have demonstrated success in predicting highly accurate conformations with a relatively low computational cost. Methods: In our study, the number of flexible pocket residues was assessed by quantitative analysis, and a novel adaptive residue flexibility prediction method, named A-RFP, was proposed to improve the docking performance. Based on the homologous information, a joint strategy is used to predict the pocket residue flexibility by combining RMSD, the distance between the residue sidechain and the ligand, and the sidechain orientation. For each receptor-ligand pair, A-RFP provides a docking conformation with the optimal affinity. Results: By analyzing the docking affinities of 3507 target-ligand pairs in 5 different values ranging from 0 to 10, we found there is a general trend that the larger number of flexible residues inevitably improves the docking results by using Autodock Vina. However, a certain number of counterexamples still exist. To validate the effectiveness of A-RFP, the experimental assessment was tested in a small-scale virtual screening on 5 proteins, which confirmed that A-RFP could enhance the docking performance. And the flexible-receptor virtual screening on a low-similarity dataset with 85 receptors validates the accuracy of residue flexibility comprehensive evaluation. Moreover, we studied three receptors with FDA-approved drugs, which further proved A-RFP can play a suitable role in ligand discovery. Conclusion: Our analysis confirms that the screening performance of the various numbers of flexible residues varies wildly across receptors. It suggests that a fine-grained docking method would offset the aforementioned deficiency. Thus, we presented A-RFP, an adaptive pocket residue flexibility prediction method based on homologous information. Without considering computational resources and time costs, A-RFP provides the optimal docking result.

Geopolymer-based insulated wall incorporating construction and demolition waste: Experimental assessment of thermo-physical behavior

The benefit of the application of geopolymers in the building sector is nowadays undisputed. In addition to good structural characteristics, these are characterized by interesting thermophysical properties, obtained through a production process, that reduces CO2 emissions and could incorporate recycled material, thus responding to environmental sustainability. However, it is noted the lack of studies regarding the in-field thermal performance. Thus, the aim of the present study is to investigate the thermal performance, under real conditions, of an innovative geopolymer-based insulated wall. It incorporates over 70% of net weight of Construction and Demolition Waste materials. The wall is conceived within the European project called “Green INSTRUCT” aimed to realize modular prefabricated building elements, for retrofitting and new construction of buildings. Two wall prototypes are analysed, which differ for the type of lightweight aggregate of geopolymer matrix, 3% by weight: expanded polystyrene or extruded polystyrene. The study refers to almost one year of continuous monitoring within a full-scale test room located in southern Italy. The method developed consists of 5 different phases and it involves also a normative-insulated reference wall. The results show higher insulation level of the proposed wall package, with a reduction of the heat flux of about 66% and more stable indoor thermal conditions, compared to the reference wall. Also the inertial properties are satisfactory, showing an experimental decrement factor equal to 0.05 and a time-shift of decrement factor higher than 6 h. All told, the experimental results can provide valuable insights into the real impact of innovative technology on energy efficiency and indoor thermal comfort.

Evaluation of Triticale Yield under the Influence of Hydrogen Peroxide in the Presence of Oxidative Catalysts

An experimental assessment of the effect of activators of oxidative processes on the yield of triticale grain crops was carried out at experimental sites of the Federal Agrarian Scientific Center of the South-East, Saratov. Triticale plants during the growing season were sprayed with an aqueous solution of hydrogen peroxide with a concentration of 5 mmol/l in the presence of oxidative catalysts based on oxygen-containing compounds: 2-butanone, 1-tetralone, cyclohexanone. The effectiveness of the use of all catalysts used in this work is shown. The best results were obtained by double treatment with an aqueous solution of cyclohexanone in hydrogen peroxide with a concentration of 5 mmol/l in a ratio of 1: 300, carried out 4 and 3 weeks before the start of harvesting, which led to an increase in the yield of triticale grain by 176% relative to the control. Hydrogen peroxide is an additional source of oxygen that accelerates metabolism in plants. An even greater activation of metabolic processes in plants occurred in the presence of oxidative catalysts (2-butanone, 1-tetralone, cyclohexanone), due to the formation of highly active oxygen-containing structures in aqueous solutions, which ultimately led to higher yields of cultivated plants, in particular triticale.

Thermodynamic investigation of reduced barium molybdates

Precise identification and thermodynamic assessment of the various phases in spent nuclear fuel are necessary for the accurate dynamic modeling of nuclear fuel. The Thermodynamics of Advanced Fuels – International Database (TAF-ID) compiles high-quality, self-consistent, and reliable thermodynamic data of various phases in chemical systems of interest for the international nuclear industry, such as the Ba-Mo-O ternary system. The thermodynamic properties of compounds in the Ba-Mo-O ternary system, especially those of hexavalent Mo, have been extensively studied and included in computational thermodynamic assessments. In contrast, compounds with Mo in reduced oxidation states, such as BaMo6O10 and Ba3Mo18O28, have been excluded from such assessments due to a lack of experimentally assessed thermodynamic data. In this work, high-quality samples of the aforementioned compounds were synthesized, and the first experimental assessment of their heat capacities in the temperature range 300–600 K were obtained. Furthermore, a reversible phase transition was identified at ∼380 K for BaMo6O10. The collected experimentally-assessed thermodynamic data from this work and initial calculated estimations of standard enthalpies of formation and entropies for these compounds were successfully integrated into a preliminary, updated Ba-Mo-O thermodynamic assessment using the CALPHAD method. Key thermodynamic properties of the newly included compounds (i.e., standard enthalpy of formation and entropy) were calculated using the new Ba-Mo-O assessment.

Thermal buckling analysis of reinforced composite conical shells in acidic environments: Numerical and experimental investigation on the effects of nanoparticles

This study investigates the effects of acid penetration and temperature on the buckling behavior of conical composite shells, to enhance structural integrity and longevity in corrosive environments. The study explores the impact of acid exposure on thermal properties and examines the efficacy of incorporating nano-silica and nano-clay in preventing buckling. Additionally, it analyzes the influence of nanoparticles on the thermal, moisture, and mechanical properties of the composite material. Experimental assessments are conducted to measure material properties during exposure to a sulfuric acid solution, providing a comprehensive understanding of the material's behavior under extreme conditions. However, due to the complexity of investigating the combined effects of temperature, acid, and nanoparticles on composite shell buckling, a combined numerical and experimental approach is adopted to predict the critical buckling load. To this end, equations of conical shells under hygrothermal loading are derived, and the critical buckling load is determined through pre-buckling analysis. The Generalized Differential Quadrature (GDQ) method is employed to solve the hygrothermal buckling of the composite shell using experimentally obtained material properties. Comparative results are presented for different nanoparticles, shell geometries, and exposure times in acidic environments. The experiments reveal that adding nanoparticles enhances mechanical properties and reduces thermal and moisture expansion coefficients. Conversely, the acidic conditions deteriorate these properties. Numerical analysis demonstrates that incorporating nanoparticles significantly increases the critical buckling temperature, with nano-silica and nano-clay particles resulting in an 11.5 % and 34.2 % increase, respectively. However, acidic environments decrease the critical buckling temperature, with reductions of 32 % for unreinforced, 29 % for nano-silica reinforced, and 46 % for nano-clay reinforced composites after three months of exposure.

Anion exchange-HPLC method for evaluating the encapsulation efficiency of mRNA-loaded lipid nanoparticles using analytical quality by design

Lipid nanoparticles (LNPs) are emerging nucleic acid delivery systems in the development of mRNA therapeutics such as the severe acute respiratory syndrome coronavirus 2 vaccines. However, a suitable analytical method for evaluating the encapsulation efficiency (EE) of the LNPs is required to ensure drug efficacy, as current analytical methods exhibit throughput issues and require long analysis times. Hence, we developed and validated an anion-exchange HPLC method using Analytical Quality by Design. Three critical method parameters (CMPs) were identified using risk assessment and Design of Experiments: column temperature, flow rate, and sodium perchlorate concentration. The CMPs were optimized using Face-Centered Central Composite Design. The discriminating power of the optimized HPLC method and RiboGreen assay was comparable. The main advantage of this method is that LNPs can be directly injected into the HPLC system without bursting the LNPs loaded with encapsulated poly(A). The optimized HPLC method was validated as robust, high-throughput, and sufficiently sensitive according to the ICH Q2 guidelines. We believe our findings could promote efficient LNPs-based drug development.

Experimental and theoretical assessment of bioinspired next-generation intercalated graphene oxide-based ceramic membranes for oil-in-water emulsion separation

2D graphene oxide (GO) membranes are gaining prominence for water reclamation from oily wastewater. Unresolved challenges include low membrane permeance from tight sheets and fouling during separation. In this work, a bioinspired Arabic gum (AG) was used as an intercalated agent with the help of glutaraldehyde to improve the GO membranes’ permeation and fouling resistance. The 2D-laminated separating layer is crafted through a self-assembling innovative approach utilizing pressurized dead-end assembly. The Arabic gum intercalated graphene oxide-modified ceramic membrane (AGIGO-CM) appeared superhydrophilic and underwater (UW) superoleophobic with a UW oil contact angle (UWOCA) of 156.1 ± 1.2°. The membrane prepared with 1 mg of AGIGO (AGIGO-1-CM) offers a flux of 17 times higher than pristine graphene oxide (p-GO) while maintaining a separation efficiency of >99% during the separation of the oil-in-water emulsions. Molecular dynamics (MD) simulations showed AG intercalation expanding the interlayer distance by up to 20 Å, with AGIGO having a higher fractional free volume (FFV) of 0.986 compared to p-GO’s 0.599. AGIGO-CM displayed lower interfacial formation energy (EIFE) of −1865.2 kcal/mol versus −765.5 kcal/mol for p-GO, indicating easier separation. It is further supported by the substantial interfacial thickness of 148 Å for AGIGO-CM compared to 53.0 Å for the p-GO membranes. AGIGO-CM showed minimal fouling, retaining >99% separation efficiency for 6 h. Compared to p-GO-CM, AGIGO-CM flux decreased by only 17.84% versus 44.72%. AGIGO-CM exhibited stability even in acidic and basic environments, showcasing its potential for high performance.

Fabrication of Laminated Electrospun Fire˗Resistant Phosphorylated Poly(Vinylalcohol) Membrane for Enhanced Firefighter Safety

AbstractThe current study focuses on the creation of breathable and fire˗retardant fibrous membranes using phosphorylated poly(vinylalcohol) (PPVA) via the electrospinning method, with a specific interest in their application for structural firefighter clothing. Poly(vinylalcohol) (PVA) was phosphorylated to enhance its inherent flame resistance. Optimization of reaction conditions, including time and temperature, was conducted to achieve a solution suitable for electrospinning. The flame resistance of PPVA was confirmed through vertical flammability tests, with thermogravimetric analysis indicating a significant increase in carbonaceous char formation during PPVA decomposition compared to unmodified PVA. The limiting oxygen index also exhibited a notable increase from PVA to PPVA. Furthermore, the study established optimal operating conditions for producing uniform fibers, considering parameters such as polymer concentration, feed rate, tip to collector distance, and applied potential difference. The PPVA membrane demonstrated superior water vapor transmission rates compared to PVA, indicating enhanced breathability. The entire fabrication process utilized an environmentally friendly water‐based solvent. Additionally, a moisture‐cum‐thermal barrier layer (MCTB) was developed by laminating the PPVA fibrous membranes with microporous polytetrafluoroethylene and further with needle punch‐spunlaced OPAN fabric. Experimental assessments of the MCTB layer revealed satisfactory breathability and thermal performance, surpassing the standard requirements of 35 cal/cm2 for structural firefighting configuration.

Multiscale Computational Modeling of 3D Printed Continuous Fiber-Reinforced Composites

The printing parameters used during the printing procedure have a significant effect on the mechanical characteristics of 3D printed continuous fiber reinforced composites (3DP-CFRPCs). However, conducting experimental assessments of the material characteristics of 3DP-CFRPCs may require more effort and incur more costs. Computational material modeling may be used as a viable alternative to investigate the behavior of 3DP-CFRPCs under various printing conditions. The current work used material modeling approaches to examine the impact of different printing settings on the elastic characteristics of 3DP-CFRPCs. The inherent flexibility of beads is primarily established by homogenizing the pores within the matrix via the use of the Mori-Tanaka process. Subsequently, the elastic modulus is calculated by using finite element modeling on Representative Volume Element (RVE), which takes into account the microstructure and other printing attributes. An inconsistency was seen in the variation of projected elastic properties across models distinguished by various microstructures, with a more pronounced differentiation observed between intricate and simpler microstructures. Computational modeling has enhanced our understanding of the elastic properties of 3DP-CFRPCs under various printing conditions. Moreover, it has been shown that alterations in printing parameters have diverse impacts on the pliable characteristics of 3DP-CFRPCs. The impact of layer thickness on the mechanical characteristics of 3DP-CFRPCs was determined to be more substantial compared to the effect of printing temperature. The application of offset layup printing techniques enhanced the elastic properties of 3DP-CFRPCs, with the degree of improvement varying based on the orientation. As the level of porosity increased, the influence of pores situated between beads on the overall stiffness of 3DP-CFRPCs gradually diminished, while the impact of matrix pores on the overall stiffness of 3DP-CFRPCs gradually intensified.

Additively manufactured carbon fiber reinforced-polyamide component: a study based on statistical modeling and regression analysis

This paper presents the experimental assessment of the hardness characteristic of additively manufactured polyamide (PA 6) composite reinforced with carbon micro-fibers. The carbon fiber-reinforced polyamide (CFPA) components were manufactured using the additive manufacturing technique—fused deposition modeling (FDM). The experiments were conducted for testing the hardness of the samples using a Shore-D hardness tester. The novel contributions of the work towards the manufacturing fraternity include selecting a scantly researched material like CFPA, and the elaborative investigation of hardness variation with the alteration of the prime parameters pertaining to FDM. The effect of the print-related parameters, namely, layer height (LH), infill density (ID), and raster orientation (RO) on the hardness of the CFPA component was studied, and the results were analyzed using statistical analysis tool ‘analysis of variance (ANOVA)’. Moreover, a regression model was developed to predict the output response, i.e. hardness for different combinations of the input parameters. Considering an ID of 100% and an RO of 0°, the hardness value of 93.89 at 0.1 mm LH reduced to 88.44 at 0.3 mm LH, depicting a reduction of 5.81%. An increasing trend was observed for hardness with the increase in ID for all the levels of LH and RO. The highest value of hardness (93.89) was achieved at an ID of 100%, with the LH and RO values kept at 0.1 mm and 0°, respectively. The ANOVA suggested that the effect of all three parameters is significant in the study, ID being the most affecting parameter with an effect contribution of 37.88%. The fitness of the adopted model was well justified by the high R-sq value of 0.9618 and significantly low error values in the range of 0.002–0.08.