Search Results (366)

Triply periodic minimal surface (TPMS) sandwich structures were proposed based on the TPMSs. The test samples for the TPMS sandwich were prepared using Multi Jet Fusion (MJF) with PA12 as the base material. Their low-velocity impact responses were investigated using experimental tests and numerical simulation. The effect of structural parameters (relative density, panel thickness, impact energy, and TPMS core) on the impact performance of the sandwich structures was analyzed through parameter studies. The results indicate that the peak load and stiffness of the sandwich structure increase with the increase in relative density, panel thickness, and impact energy. Among three types of TPMS core sandwich structures, the Diamond sandwich structure exhibits the biggest peak load and best impact resistance. Full article

Rigid polyurethane-based foam is an ideal choice for sandwich-panel-filling materials due to its high strength, low thermal conductivity, high adhesion, and high chemical resistivity. Since sandwich panel materials often face cyclic mechanical loads during their service, it is significant to study the design methods of fatigue-resistant rigid polyurethane foam and its fatigue failure mechanism to improve the performance of sandwich-panel-filling materials. In this study, a fatigue-resistant rubber powder/polyurethane composite material was prepared by introducing rubber powder, and its fatigue failure mechanism was systematically studied. The static mechanical test results indicate that with the introduction of 20% rubber powder, the compressive strength (at 85% strain) increased to 588 kPa. Additionally, thanks to the excellent energy absorption and dissipation properties of rubber powder, it can effectively dissipate mechanical energy during cyclic loading. The fatigue test results show that after the introduction of rubber powder, the fatigue life of the polyurethane foam material increases from 10,258 cycles (for PU, stress ratio 0.6) to 45,987 cycles (for 20R-PU, stress ratio 0.6). This study not only proves the fact that rubber powder can improve the fatigue performance of foam materials but also provides a potential option for the design of high-performance filling materials. Full article

Solar photovoltaic (PV) systems in buildings must comply with both electrotechnical standards for module safety and local building codes, which typically do not address their electrical nature. This regulatory gap creates challenges in assessing the fire performance of PV systems. This paper presents a procedure to adapt a common test method used in some building codes to assess external fire conditions for roofs, while maintaining operative PV modules. Two configurations were tested: an organic PV thin film on a metallic sandwich panel and a glass–glass-encapsulated organic PV module. The tests were conducted under high voltage and current conditions to simulate the systems’ behavior within a larger PV array. Significant electric arcs were observed during testing of the metallic sandwich panel configuration without glass protection when subjected to high voltages or currents. In these cases, total heat release increased by at least 30% compared to non-electrically loaded scenarios or glass-insulated PV modules, likely due to a greater damaged surface area. Electric arcs created new ignition sources, damaging whole PV modules, whereas in the case with no electrical load, propagation flames advanced toward both the upper edge and the corners of the sample, ultimately damaging the entire triangular area above the fire source. The results indicate that the electrical characteristics of PV systems can significantly impact external fire spread behavior. The study identifies challenges in maintaining system activity during testing and simulating real scenarios and proposes for future research directions. Full article

A novel 316L stainless steel Vertex Modified BCC (VM-BCC) lattice unit cell with attractive performance characteristics is developed. Lattice structure, as well as the sandwich panel, are constructed. Numerical simulation is utilized to simulate the quasi-static compression, dynamic compression and blast behavior considering the rate-dependent properties, elastoplastic response and nonlinear contact. Finite element results are validated by comparing with the experimental results. Parametric studies are conducted to gain insight into the effects of loading velocity, equivalent TNT load and explosion distance on the dynamic behavior of the lattice pattern and sandwich panel. Testing results indicate that the proposed 316L stainless steel VM-BCC structure exhibits more superior plateau stress and specific energy absorption (SEA) than those of the BCC or Octet one. The proposed novel lattice will provide reference for improving the protective efficiency in key equipment fields and enhancing overall safety. Full article

The traditional timber architecture of Qiandongnan represents a rich cultural heritage. However, urbanization has led to the replacement of these structures with concrete and brick buildings, resulting in the loss of both functionality and cultural identity. To bridge the gap between traditional architecture and modern building needs, this study conducted field surveys to extract key design parameters from local structures, enabling the development of a modular framework for Structural Insulated Panels (SIPs) based on the dimensions of traditional dwellings. Four types of SIPs were developed using Chinese fir, OSB, EPS, and XPS, and their thermal performance and heat stability were evaluated through theoretical analysis and hot box testing. The results show that all specimens met the required heat transfer coefficient. The combination of OSB and XPS showed a slightly lower heat transfer coefficient of 0.60 compared to Chinese fir, which had a coefficient of 0.62. However, the Chinese fir–XPS combination provided the longest time lag of 6.34 h, indicating superior thermal stability. Due to the widespread use of Chinese fir in local construction and its compatibility with the landscape, this combination is ideal for both energy efficiency and cultural preservation. Full article

In this investigation, we assessed the potential of aluminum composite panels (ACPs) in sustainable engineering applications, focusing on the effects of different glass fiber weights on impact resistance and energy absorption capacity. Aluminum composite panels are an attractive option for sustainable applications due to their lightweight and high-strength properties. In this study, low-velocity impact tests were conducted on panels with glass fiber weights of 200 g/m² and 400 g/m² and equal numbers of fiber layers. The tests were performed using a constant impact energy of 55 joules, and the force–time, force–displacement, energy–time, and energy–displacement behaviors of ACP, 200 ACP, and 400 ACP samples were analyzed. The results showed that the 400 ACP samples exhibited the highest impact strength, the highest energy absorption capacity, and the least damage. In contrast, the other two samples showed lower impact resistance and exhibited fiber breaks, delaminations, and core material damage on their surfaces. The different glass fiber weights used in this study contributed to increases in the impact resistance and energy absorption capacity. Positive correlations were found between the glass fiber weight, layer thickness, and impact strength. These findings provide new insights into how composite materials can be designed to optimize mechanical properties by adjusting the fiber weights in coatings. These results also offer valuable information for the development of next-generation materials used in various sustainable engineering fields, such as automotive engineering and vehicle technology. Full article

In this study, the magnetic signatures of ship structures were investigated. The magnetic signature impacts both navigation safety and the health of the marine ecosystem. Reducing this signature is essential for minimising risks associated with navigation and protecting marine biodiversity. A finite element model was developed to assess the magnetic signature of honeycomb sandwich panels for ship structures. A theoretical approach was proposed, and the predicted results were compared with the values obtained by the finite element analyses. Different types of structures were compared to evaluate the combined effect of materials and geometry on the magnetic signature. The finite element results and the theoretical predictions indicate that the use of metamaterial structures, consisting of honeycomb sandwich panels with a steel core and aluminium skins, produces a significant reduction of the ship magnetic signature compared to the one arising from a steel panel with the same bending stiffness. Full article

The study of the mechanical behavior of functionally graded material (FGM) sandwich plates under thermo-mechanical loading is of great significance for advanced structural design. This study systematically verifies the applicability of the shear strain functions proposed by Reddy and Touratier in the nonlinear bending analysis of porous FGM sandwich plates. Using the existing four-variable shear deformation theory framework, the governing equations are derived through the principle of minimum potential energy, and the Navier method is applied for a numerical solution. For the first time, the study systematically compared the effects of three different porosity distribution patterns on dimensionless deflection, and verified the reliability of the model by comparing it with literature data. The results demonstrate that the adopted shear strain functions can accurately predict the influence of key parameters, including layer thickness ratio, aspect ratio, side-to-thickness ratio, volume fraction index, and porosity, on the deflection performance of sandwich plates. This research provides an important verification basis for the theoretical analysis and engineering application of FGM sandwich plates, particularly offering quantitative evidence for assessing the influence of porosity effects on theoretical prediction accuracy. Full article

Given the current need to improve the thermal and energy performance of buildings, special attention has been given to the building envelope and materials. Concrete sandwich panels (CSPs) are versatile composite construction elements whose popularity is increasing given their properties, e.g., good thermal and acoustic insulation, durability, and fire resistance. Nevertheless, besides their properties, it is important to evaluate the sustainability of composite panels under development. This work aims to assess the eco-efficiency of six CSPs with distinct insulation materials: lightweight concrete (LWC), cork, glass wool, and expanded polystyrene (EPS). Coupling both life cycle assessment (LCA) and life cycle costing (LCC) analysis, this study derives eco-efficiency indicators to inform decisions regarding CSP environmental and economic performances. The results of the LCA and LCC showed that the high-performance concrete (HPC) layer was the main hotspot of the CSPs in all scenarios. Moreover, the best scenario changed when different environmental impact categories were considered. Thus, using multiple environmental indicators is recommended to avoid problem-shifting. Considering the final cost, the CSP with cork is the most expensive panel to produce, with the other five options having very similar manufacturing prices. On average, raw material inputs, labour, and material delivery account for 62.9%, 18.1%, and 17.1% of the total costs, respectively. Regarding the eco-efficiency results, the most eco-efficient scenario changed with the environmental indicator used. Cork seems to be the best option when considering the carbon footprint of the panels, whereas when considering other environmental indicators, the recycled EPS scenario has the best eco-efficiency and the CSP with cork the worst. Full article

This study explores the optimization of rigid polyisocyanurate (PIR) foam formulations, focusing on foaming kinetics that significantly influence the foam’s microstructure and thermal insulation properties. By systematically altering components such as isocyanate, polyols, catalysts, blowing agents, and additives, this research investigates their effects on key characteristics including cell density, mechanical strength, and thermal conductivity. A statistical approach known as response surface modeling (RSM) was employed to identify relationships between formulation variables and performance metrics. The optimization aimed to enhance thermal insulation while ensuring feasibility for industrial-scale production, particularly for sandwich-type PIR panels. Two distinct formulations, with isocyanate indices of 335 and 400, were developed to assess the impact of various parameters on properties like foaming start time, gel time, and density. The results indicated that the choice of blowing agents and catalysts played a pivotal role in controlling foaming kinetics and final mechanical properties. The optimized formulations exhibited competitive thermal conductivity values (around 23.7 mW/(m·K)) and adequate compression strength (0.32 MPa), aligning closely with commercially available materials. These findings affirm the potential for enhancing production efficiency and performance consistency in the manufacturing of rigid PIR foams for insulation applications. Full article

The green transition trend in the wood-based panel industry aims to reduce environmental impact and waste production, and it is a viable approach to meet the increasing global demand for wood and wood-based materials as roundwood availability decreases, necessitating the development of composite products as alternatives to non-wood lignocellulosic raw materials. As a result, the purpose of this study is to examine and assess the physical, mechanical, and acoustic properties of particleboard manufactured from non-wood lignocellulosic biomass. The core layer was composed of non-wood lignocelluloses (banana stem, rice straw, coconut fiber, sugarcane bagasse, and fibrous vascular bundles (FVB) from snakefruit fronds), whereas the surface was made of belangke bamboo (Gigantochloa pruriens) and wood. The chemical characteristics, fiber dimensions and derivatives, and contact angles of non-wood lignocellulosic materials were investigated. The contact angle, which ranged from 44.57 to 62.37 degrees, was measured to determine the wettability of these materials toward adhesives. Hybrid particleboard (HPb) or sandwich particleboard (SPb) samples of 25 cm × 25 cm with a target density of 0.75 g/cm³ and a thickness of 1 cm were manufactured using 7% isocyanate adhesive (based on raw material oven dry weight). The physical parameters of the particleboard, including density, water content, water absorption (WA), and thickness swelling (TS), ranged from 0.47 to 0.79 g/cm³, 6.57 to 13.78%, 16.46 to 103.51%, and 3.38 to 39.91%, respectively. Furthermore, the mechanical properties of the particleboard, including the modulus of elasticity (MOE), bending strength (MOR), and internal bond strength (IB), varied from 0.39 to 7.34 GPa, 6.52 to 87.79 MPa, and 0.03 to 0.69 MPa, respectively. On the basis of these findings, the use of non-wood lignocellulosic raw materials represents a viable alternative for the production of high-performance particleboard. Full article

Sandwich panels, consisting of two concrete wythes that encase an insulating core, are designed to improve energy efficiency and reduce the weight of construction applications. This research examines the thermal and flexural properties of a novel sandwich panel that incorporates ultra-high-performance fiber-reinforced concrete (UHPFRC) and cellular lightweight concrete (CLC) as its core material. Seven sandwich panel specimens were tested for their thermo-flexural performance using four-point bending tests. The experimental parameters included variations in UHPFRC thickness (20 mm and 30 mm) and different shear connector types (shear keys, steel bars, and post-tension steel bars). The study also assessed the effects of adding steel mesh reinforcement to the UHPFRC layer and evaluated the performance of UHPFRC box sections without a CLC core. The analysis concentrated on several critical factors, such as initial, ultimate, and serviceability loads, load–deflection relationships, load–end slip, load–strain relationships, composite action ratios, crack patterns, and failure modes. The thermal properties of the UHPFRC and CLC were evaluated using a transient plane source technique. The results demonstrated that panels using post-tension steel bars as shear connectors achieved flexural performance, and the most favorable composite action ratios reached 68.8%. Conversely, the box section exhibited a brittle failure mode when compared to the other sandwich panels tested. To effectively evaluate mechanical and thermal properties, it is important to design panels that have adequate load-bearing capacity while maintaining low thermal conductivity. This study introduced a thermo-mechanical performance coefficient to evaluate both the thermal and mechanical performance of the panels. The findings indicated that sandwich panels with post-tension steel bars achieved the highest thermo-mechanical performance, while those with steel connectors had the lowest performance. Full article

Objectives: Low-grade metabolic inflammation is associated with several chronic metabolic disorders, including obesity. However, no concrete evidence that supports obesity as a direct cause of chronic inflammation. This study aims to identify the association of inflammation with obesity in apparently healthy adults. Methods: In this study, 162 seemingly healthy volunteers, aged between 20 and 40 years, of comparable sex ratio, were recruited and categorized based on their body mass index (BMI) into four obesity scales: normal (N), overweight (OW), obese (OB), and severely obese (SOB). After clinical examination, fasting blood samples were collected from the study subjects for glycemic (fasting blood glucose—FBG, and HbA1c) and lipid (total cholesterol, LDL-C, HDL-C, and triacyl glycerides -TAG) profile analysis. In addition, plasma levels of a panel of diverse inflammatory biomarkers, IL6, IL8, procalcitonin (PCT), TREM1, and uPAR were analyzed by sandwich ELISA. Results: The results showed that LDLC, TAG, FBG, and HbA1c were significantly higher in the obese (OB and SOB) group, compared to the non-obese (N and OW) group, while HDLc was significantly lower. The biomarker levels were not correlated with age or significantly differed between males and females. Importantly, levels of all assessed inflammatory biomarkers were comparable between the obesity classes. Moreover, the assessed biomarkers in subjects with dyslipidemia or dysglycemia were comparable to those with normal profiles. Finally, the biomarker levels were not correlated with the obesity, glycemic, or lipidemic parameters. Conclusions: After correction for age and co-morbidities, our results deny the association of discrete obesity, probably dyslipidemia, and dysglycemia with systemic chronic inflammation. Further studies of local and systemic inflammation in non-elderly, healthy obese subjects are needed. Full article

Ultimate strength is critical for hull structures because it determines the maximum load the structure can withstand before catastrophic failure. Aluminium honeycomb sandwich panels provide excellent energy absorption and a high strength-to-weight ratio. However, further investigation of honeycomb sandwich panel structural performance is needed in typical marine conditions. This study focuses on the numerical analysis of honeycomb sandwich panels employing the nonlinear finite element method through the commercial software ANSYS. It investigates their performance under uniaxial compression and varying lateral pressure conditions while considering different cell edge lengths and core height configurations. Several structural configurations are compared to the experimental work published in the literature. Enhanced by experimental accuracy, the present study is a further step in expanding the application of honeycomb sandwich panels for ship hull applications that may lead to light and energy-efficient structures. Full article

The construction field is one of the largest sectors and industries worldwide. This industry is the main industry accused of contributing to greenhouse gases and increasing the effects of climate change. However, the construction industry is indispensable, accordingly in an attempt to decrease the greenhouse gas effects of construction this research presents the manuscript for building a one-story building with all components including waste products. The building model used a strip foundation with a concrete mix design incorporating recycled concrete as a partial replacement for aggregates, cement hollow blocks containing granite waste instead of conventional cement blocks, and sandwiched insulated panels made of wood-plastic composites for the roof. The structural soundness of the system was tested by loading it with a load surpassing its design load in addition to measuring the deflection and checking its abidance to the code limitations. The thermal efficiency was tested by measuring the temperatures in comparison with the outside of the building for a span of 7 days with data recorded every 1 h. Analysis of both the short-term and long-term costs and carbon emissions was performed by acquiring the carbon emissions per unit of material from literature and multiplying it by the quantities of the materials used within the different building alternatives. That study showed that the roofs made of Structural Insulated Panels (SIPs) using Wood-Plastic Composite (WPC) facings when used with hollow-block cement block walls have shown enduring cost efficiency and improved thermal insulation, leading to diminished energy usage, life-cycle expenses, and carbon emissions. Furthermore, the proposed system is more environmentally friendly than conventional reinforced concrete technologies due to their lower costs and emissions in addition to improving sustainability through utilizing recycled materials. Full article