Panel Thickness Research Articles

Research on the Estimation of the Flexural Capacity of EPS Lightweight Concrete Panels

Expanded Polystyrene (EPS) lightweight concrete possesses numerous special characteristics, including exceptionally low weight, good sound insulation, effective heat insulation, great fire resistance, and low water absorption. Consequently, it has garnered significant attention for research and practical applications in the construction industry, particularly in the development of soundproofing and thermal insulation components, as well as lightweight elements to reduce the superstructure weight, such as external wall panels, floor slabs, roof panels, and base materials. The primary objective of this study is to analyze and estimate the flexural capacity of EPS lightweight concrete panels through both experimental and numerical methods. Furthermore, the influence of the longitudinal reinforcement ratio, strength, and thickness of EPS lightweight aggregate concrete panels on their flexural capacity is thoroughly investigated and evaluated. The findings demonstrate that the Abaqus software, with an appropriate material model for EPS lightweight aggregate concrete, can reliably predict the flexural capacity of EPS lightweight concrete panels reinforced with longitudinal rebars.

Numerical Analysis of Explosion-Induced Deformations on Steel Panels in Urban Environments

Explosion proof structures are designed to be very heavy and non-functional using conventional systems so that they can be resistant to blast effects. As a result, not only the emergence of non-economic structures, but also their operational performance decreases. To effectively mitigate these challenges, a substantial body of research has focused on the development and application of designs and materials specifically engineered to withstand explosive load impacts. In this study, the strength of steel plates under explosives with different energies was tested. Related tests were performed using Ls-Dyna finite element software. An experimental literature was used to calibrate the numerical model. When the results obtained as a result of the calibration were compared with the experimental data, a high level of agreement was obtained. The calibrated numerical model was subjected to burst loads by varying the panel thicknesses and its dynamic responses were simulated. The displacement values were analyzed by placing the explosives equidistant from the panel centers. By comparing the analysis results, explosive energies were compared. The most effective explosive types could be listed according to the amount of change that the evaluated explosives in the same amount caused on the panel surfaces. In line with these studies, information will be gained about what type of steel materials will be used against which type of explosives in areas that need to be protected in urban areas.

Study of shear performance of steel-timber composite connection with different shear connectors

The shear resistance of steel-timber composite (STC) connections largely depends on the shear performance of shear connectors. Three types of shear connectors, i.e., welded stud, screw, and screw-grout were considered in this paper. The failure modes, load-slip curves, shear stiffnesses, and shear carrying capacity of the STC connection with three different connectors were experimentally and theoretically investigated under various shear connector diameters and glulam panel thicknesses. The experimental results indicated that the shear carrying capacity and stiffness of the welded stud connections are 1.49 and 5.17 times higher than those of the screw connection under identical cases, respectively. The failure patterns of welded stud connection were characterized by shear failure of the stud, crushing failure in the grout blocks and splitting failure of the glulam panel. In contrast to welded stud connections, screw and screw-grout connections exhibited significant crushing failure of glulam. It indicated that the grout used in welded stud connection can effectively mitigate or avoid crushing failure in the glulam panel. A simplified and feasible theoretical formula was developed to predict the shear carrying capacity of the STC connection with welded stud connector. Compared with the predictions of GB 50017-2017, AISC 360-16, and EC 4, the developed formula for the shear carrying capacity of welded stud connection provided a reasonable prediction with an error within 15%.

Static and structural dynamic analysis of thick panel kirigami deployable structures

Thick panel origami and kirigami concepts have been wildly used to design novel deployable structures in various engineering applications. However, these novel folding methods usually involve complex connected topologies, which may lead to unclear and intricate characterized relationships between system properties and structural parameters, e.g., the position of cutting creases, design parameters and hinge stiffness arrangement, etc. In this paper, we propose theoretical models to describe the static and dynamic properties of thick panel kirigami structure in the fully deployed configuration. Firstly, the connected topology of the origami and kirigami structure is analysed, and the internal coupling topology of the structure is obtained. Based on the compliant matrix method, the static model of the structure is presented, and the different crease cutting modes of origami and kirigami arrays are discussed. Then, the motion modes of slight oscillation of structure are discussed and the structural dynamic model is obtained based on the Lagrange equation and validated by simulation. On this basis, the sensitivity analysis of the parameters is carried out, and the optimization model is given based on the comprehensive performance evaluation function. A physical prototype is optimized and tested, which indicates that our model is valid. This paper provides models for the structural static and dynamic properties of thick panel kirigami structures with complex connected topology, and the findings have a potential to be developed in other thick panel structures with origami and kirigami folding concepts.

Oriblock: The origami-blocks based on hinged dissection

Traditional origami, a well-known art of paper-folding, does not account for material thickness. Subsequently, several thickness-accommodation techniques have been developed, considering the non-negligible thickness of materials, which enables the application of origami to a wide range of mechanisms. Although these techniques prevent self-intersections and preserve kinematics after accommodating panel thickness, they are limited by their reliance on initial zero-thickness origami patterns in two dimensions. To address this issue, this study proposes a novel technique, the volume-accommodation technique in three-dimensional space, which allocates non-coplanar origami creases based on solid geometry to allow a greater variety of shape-changing motions. Typical solid geometries, such as a pyramid and a prism, are selected as examples to demonstrate the design procedures. Closure equations of the obtained oriblock are used to analyze the kinematic properties. Additionally, Bennett and Myard Linkages are derived from oriblocks based on their kinematic equivalence to strengthen their connections. As a result, this new type of origami can offer a variety of mechanisms for designers and facilitate potential applications in origami-inspired metamaterials and robotics.

Evaluation of the Applicability of Waste Rubber in Insulation Panels with Regard to Its Grain Size and Panel Thickness.

This paper explores the effect of waste rubber grain size on the porosity, modulus of elasticity, thermal properties, and soundproofing performance of polymer composites with different thicknesses (10, 15, and 20 mm). All properties were tested in accordance with European standards, with the exception of porosity, which was measured using Archimedes' principle. The findings indicate that with a consistent amount of polyurethane glue, finer rubber grains result in composites with higher porosity, leading to a lower modulus of elasticity but enhanced thermal and sound insulation. In contrast, coarser rubber grains produced composites with lower porosity and a higher modulus of elasticity, though with slightly reduced thermal insulation and significantly worse soundproofing. A combination of fine and coarse rubber grains provided a balanced performance, offering both good thermal and sound insulation while maintaining a high modulus of elasticity. Among the thicknesses tested, 15 mm was identified as optimal, combining a relatively high modulus of elasticity, low thermal conductivity, and better airborne sound insulation index. Future research will focus on applying this composite in concrete building products that meet noise protection and energy efficiency standards.

A conceptual design and structural analysis of thick panel kirigami for deployable volumetric modular structure

This study addresses key challenges in modular construction, such as transportation and lifting limitations, by introducing a kirigami-inspired modular structure that folds into a compact flat-pack and deploys into a volumetric form. The research explores two pop-up kirigami kinematic (i.e.V-fold and sliding) mechanisms utilising thick panel material for modular structural elements. The study develops spatial linkage with degree-four vertices by implementing a thick panel axis-shift method, enabling transformation into volumetric forms through a single-degree-of-freedom actuation. The structural performance of the kirigami deployment pattern under service loads was evaluated using finite element modelling. Fibre-reinforced polymer was selected as the primary material due to its low self-weight and adequate structural properties, making it a viable alternative to conventional steel for deployable structures. Results demonstrated compliance with design standards for displacements, stresses, and global drift. Additionally, the inclusion of a locking mechanism significantly enhances the structural stability of the module by restraining any potential movement in its fully deployed state.

Experimental and numerical study of light, fragile vent covers under vented gas explosions

In this study, the venting functions of autoclaved aerated concrete (AAC) and gypsum vent covers under gas explosion conditions were examined for the first time. Eleven sets of field tests were performed, data such as overpressuretime history and rupture pressure data were collected, and failure modes were recorded and analysed. The results show that the AAC and gypsum panels can substantially reduce the internal peak overpressure and duration, and the AAC panel is the venting component with the best performance. The dynamic rupture pressure of venting covers obviously differs from the internal peak overpressure and static failure overpressure, so the opening process and dynamic effect of venting covers should be considered in the design. A numerical model of the AAC panel was established in LS-DYNA. In a parametric study, the panel thickness, material strength, boundary conditions and rate of overpressure rise considerably affected the rupture pressure. On this basis, an empirical formula for the rupture pressure and its applicable range is presented.

Environmental Sustainability Assessment of Cold Storage Panel Production

Today's ever-increasing environmental sustainability concerns have led to a major shift in construction sites and industrial sectors. In this context, the choice of construction materials for important structures such as cold storages plays an important role in terms of both environmental impacts and energy efficiency. The aim of this study is to evaluate the environmental loads of cold storage panels with thicknesses of 80 mm, 100 mm, 120 mm, 150 mm, 180 mm and 200 mm. In order to reveal the production inputs that cause these loads, the environmental effects were examined specifically for the 100 mm thick cold storage panel. Environmental impacts were analyzed using the Life Cycle Assessment (LCA) method in accordance with the ISO 14040/44 methodology as a system boundary "cradle to gate". This study focused on three different environmental impact categories of cold storage panels produced in Türkiye: global warming potential (GWP), cumulative energy demand (CED) and water footprint. In the evaluation of environmental impacts, production inventory information obtained from the panel manufacturer was used. For analyses, Simapro v. 8.5 LCA software was used. Analysis results show that the use of galvanized sheet metal in cold storage panel production is a hot spot in terms of global warming effect. It has been determined that the largest share in the water footprint belongs to polyurethane used as insulation material. Additionally, according to the CED, non-renewable fossil and non-renewable nuclear were determined to be the most affected categories, and the use of galvanized sheet metal and polyurethane were determined to be the most important hot spots in terms of non-renewable and renewable resources. To help improve the environmental performance of the cold storage panel, it is recommended to use bio-based and less environmentally impactful raw materials in production and to measure their environmental impact on a life cycle basis from cradle to grave.

Bending response and energy absorption of sandwich beams with combined reinforced auxetic honeycomb core

This study introduces a reinforced star-shaped auxetic honeycomb (RSSAH) sandwich beam, enhanced with hollow thin-walled tubes to improve bending resistance and energy absorption performance. The bending performance of the RSSAH is systematically investigated through quasi-static three-point bending tests and finite element numerical simulations. The findings suggest that when subjected to mid-span stress, the RSSAH displays both localized indentation and overall bending deformation, accompanied by notable negative Poisson’s ratio (NPR) impact under bending loads. Parametric studies are undertaken by numerical simulations to investigate the impact of compression position, auxetic angle, and face sheet thickness on the bending mode of the auxetic honeycomb sandwich beam. The analysis shows that the RSSAH can exhibit excellent bending performance and, at one of the compression positions, displays double-plateau stress characteristics. It is also found that altering key geometric parameters, such as the auxetic angle and panel thickness ratio, can greatly improve the bending capabilities of the RSSAH, achieving stable plastic deformation and high energy absorption. Finally, compared to star-triangle honeycomb (STH) sandwich beam, traditional reentrant honeycomb (RH) sandwich beam and star-shaped auxetic honeycomb (SSAH) sandwich beam, the RSSAH demonstrates superior bending performance and energy absorption capacity. This study offers insights and references for the development of innovative reinforced auxetic honeycomb sandwich beams.

A Circular Economy Perspective: Recycling Wastes through the CO2 Capture Process in Gypsum Products. Fire Resistance, Mechanical Properties, and Life Cycle Analysis

In recent years, the implementation of CO2 capture systems has increased. To reduce the costs and the footprint of the processes, different industrial wastes are successfully proposed for CO2 capture, such as gypsum from desulfurization units. This gypsum undergoes an aqueous carbonation process for CO2 capture, producing an added-value solid material that can be valorized. In this work, panels have been manufactured with a replacement of (5 and 20%) commercial gypsum and all the compositions kept the water/solid ratio constant (0.45). The density, surface hardness, resistance to compression, bending, and fire resistance of 2 cm thick panels have been determined. The addition of the waste after the CO2 capture diminishes the density and mechanical strength. However, it fulfills the requirements of the different European regulations and diminishes 56% of the thermal conductivity when 20%wt of waste is used. Although the CO2 waste is decomposed endothermically at 650 °C, the fire resistance decreases by 18% when 20%wt. is added, which allows us to establish that these wastes can be used in fire-resistant panels. An environmental life cycle assessment was conducted by analyzing a recycling case in Spain. The results indicate that the material with CO2 capture waste offers no environmental advantage over gypsum unless the production plant is located within 200 km of the waste source, with transportation being the key factor.

Topology optimization based on the improved high-order RAMP interpolation model and bending properties research for curved square honeycomb sandwich structures

Curved honeycomb sandwich structures with larger surface areas effectively reduce the number of fasteners and connectors, resulting in weight reduction, cost savings, and reliability improvement. Square honeycombs exhibit higher in-plane tensile strength, and are more compatible with mechanical components. Topology optimization can realize the variable-density design of square honeycombs, enhancing the strength and stiffness of curved sandwich structures, but the high-order Rational Approximation of Material Properties (RAMP) interpolation model with a fast convergence rate has the relatively poor clarity and stability in topology boundaries. Hence, a variable-density topology optimization method based on the improved high-order RAMP model is developed for curved square honeycomb sandwich structures. The high-order RAMP interpolation model is improved by incorporating a minimum modulus term into the material interpolation function and employing the Bi-directional Evolutionary Structural Optimization (BESO) to refine the Optimality Criteria (OC) method. A functional relationship between the wall thickness of cross-shaped cells (i.e., simplified models of four adjacent square cells arranged in a cross) and the relative density of topology units is constructed using a density mapping method, and the topology optimization with the relative density of cross-shaped cells as the design variable is performed to minimize the compliance of the core. Three-point bending tests are conducted on 3D printed non-optimized and optimized curved honeycomb sandwich structures with different core material retention rates and panel thicknesses, and the experimental results are compared with those of simulations to explore the bending properties and failure behaviors. The results indicate that the modified high-order RAMP interpolation model enhances the clarity and stability of topology structures, the variable-density topology optimization significantly improves the bending properties of curved square honeycomb sandwich structures, and the experimental and numerical results are largely consistent.

A rigidly foldable and reconfigurable thick origami antenna.

A rigidly foldable and reconfigurable origami antenna is developed here. This antenna uses thick folding panels thereby providing robust operation and folding/unfolding actuation, which are very important for many applications in extreme environments, such as space. Also, this antenna can be constructed using standard printed circuit boards, which simplifies its manufacturing. For the reconfigurable antenna developed here, the origami flasher pattern is chosen to achieve a spatial transformation of a dipole operating at 0.48 GHz to a conical spiral antenna (CSA) operating from 2.1 to 3.7 GHz. The design equations for the origami CSA are derived. A prototype is built using a 0.81-mm-thick FR4 substrate to validate the proposed methodology. The antenna parameters are investigated in a wide frequency range. Our simulated results agree very well with the measurements. The rigid structure of the proposed design and its reconfigurable nature make it a good candidate for satellite communications.This article is part of the theme issue 'Origami/Kirigami-inspired structures: from fundamentals to applications'.

Out-of-plane performance of BFRP reinforced UHPC thin panel: experiment and numerical analysis

In this study, the out-of-plane performance of ultra-high performance concrete (UHPC) thin panels reinforced with basalt fiber reinforced polymer (BFRP) bars was investigated. Eight panels were tested under four-point load, with the investigating parameters including panel thickness, reinforcement ratio, and the presence of steel fibers. The failure mode, crack pattern, load vs. mid-span displacement, and reinforcement strain relationships were studied. Test results revealed that panels with a higher thickness (70 mm) exhibited 178.6% higher initial stiffness, 34.5% higher cracking loads, and 88.7% higher peak loads compared to those with a lower thickness (50 mm). The effects of a larger reinforcement ratio and the presence of steel fibers became more pronounced after concrete cracking, leading to 21.2% and 22.1% higher post-cracking stiffness, respectively. Adding steel fibers helped control the development of diagonal cracks and shifted the panel failure mode from shear to flexural failure. Based on the comparison of test results with design codes, the expressions in CAN/CSA-S806-12 were recommended for predicting the load-carrying capacity of the specimens. Furthermore, a two-dimensional finite element (FE) model was developed to reproduce the test results, which validates the adopted CDP model for UHPC and the bond-slip behaviors between UHPC and BFRP bars.

An innovative approach for enclosure design of power generators to meet noise regulation targets

The use of diesel-powered engine generators as a power source is very common for various industrial and residential applications. There are strict regulatory requirements and legislations to limit the noise levels from these generators below statutory limits. The purpose of the paper is to present an approach using statistical energy analysis (SEA) augmented by experimental inputs for the prediction of noise levels for the generators and propose strategies for optimized enclosure design that effectively mitigate noise to achieve regulatory requirements. The study begins by developing an SEA model that represents the acoustic behavior of the generator and enclosure. The airborne sources such as engine, alternator, radiator fan and exhaust are modelled explicitly using experimental noise source characterization. Based on the established SEA model and excitation sources, noise levels are predicted through the calculation of energy flow between subsystems. The predicted sound levels for an existing Diesel Generator with enclosure were validated with its test data to ensure correctness of SEA model. Parametric studies were carried out using simulations on key variables, including critical noise paths, panel thickness, and noise control treatments. These investigations helped identify optimal process parameters that reduce noise levels emitted by genset in adherence to noise regulations.

Centrifugal pump impeller wheel inspired acoustic metamaterial for low frequency sound absorption

Addressing low-frequency noise is a significant concern within the realm of acoustics and noise management. Labyrinthine channel based acoustic metamaterials have been proved to control low frequency noise using local resonance effect and thermoviscous dissipations. Drawing inspiration from centrifugal pump impeller wheel, an acoustic metamaterial absorber has been devised. The design incorporates impeller vanes to create a channel with variable widths and a micro-perforate panel through which sound wave propagates to the channels. Numerical simulations using COMSOL Multiphysics and experimental analysis are conducted employing Two microphone impedance tube method. Acoustic pressure and acoustic particle velocity distribution plots from numerical simulation study are used to comprehend the sound absorption mechanism. Sound absorption coefficient results reveal that this design offers a tunable sound absorption peak in low frequency regime. Furthermore, this paper discusses the influence of various geometric parameters such as, number of vanes, panel thickness and micro-hole diameter. The subwavelength dimensions of the design contribute to noise control in machineries with space constraints.

Fluid–structure interaction analysis of curved wedges entering into water

The water entry of wedges with curvature differs significantly from that of linear wedges, which have been fully investigated and formulated. The safety and integrity of structures prompt an urgent investigation into the mechanism by which the curvature affects slamming loads and structural responses during water entry. This study examines the slamming force characteristics, pressure distributions, fluid jet evolutions, and structural response behaviors of two-dimensional curved wedge sections, considering five different curvatures and two panel thicknesses. A two-way coupling fluid–structure interaction (FSI) solver has been proposed within an open-source framework. The FSI solver was validated against published literature to ensure its high-fidelity. The small deadrise angle results in a more complicated time-domain characteristics for the slamming pressure, with a gradual transition from a single peak to a double peak. The half-peak pressure duration time were defined, and the quantitative results reveal that the hydroelastic effect of the linear wedge is significantly higher than the curved wedges. When considering the geometric curvature, the elastic wedges do not consistently reduce the peak slamming pressure and lengthen the pulse time. Additionally, large deformations generated by the panel vibrations alter the evolutionary pattern of the fluid jet. In contrast to the linear wedge, the structural responses of the curved wedges show distinctive two-stage behaviors.

A novel acoustic micro-perforated panel (MPP) based on sugarcane fibers and bagasse

Natural materials are becoming a reliable alternative to traditional artificial materials used in sound absorption insulation. The present study was conducted to investigate the acoustic insulation of micro-perforated panel (MPP) based on sugarcane fibers and bagasse as an available and environmentally friendly material. The absorption properties of single- and double-leaf natural micro-perforated panels (MPP) made of bagasse and also nonnatural MPPs made of Plexiglass were measured using an impedance tube based on ISO 10534–2. Then the effect of bagasse and sugarcane fibers composite on the air gap of MPP was investigated. The results showed the peak sound absorption of the bagasse composite is in the range of 1000 to 2000 Hz, and the sugarcane fiber composite has a higher sound absorption coefficient than the bagasse composite. Also, natural MPPs have a higher absorption coefficient than nonnatural MPPs at all frequencies, and as the panel thickness increases, the peak absorption coefficient shifts to lower frequencies. The peak sound absorption coefficient of double-leaf MPPs made of bagasse is 76%, in the range of 160 to 200 Hz. Using sugarcane fiber composite in the air gap of single- and double-leaf natural MPPs causes the absorption peak to shift to frequencies below 100 Hz. According to the results, natural MPPs have a high sound absorption coefficient at low frequencies. These panels can control sounds with much lower frequencies, especially in a double layer and along with cane fiber composite in their air gap.

Compression Molding of Low-Density Polyethylene Matrix/Glass-Fiber-Reinforced Thick Laminates.

Thermoplastic fiberglass was compression molded in the form of thick panels with a nominal thickness of 10 mm and a size of 300 × 300 mm2. A simplified procedure was adopted to speed up the lamination procedure and adapt it to the aim of recycling waste, glass fibers, fabrics, and thermoplastic films. Low density polyethylene was used as a matrix to simplify the laboratory process, but the same procedure can be extended to other thermoplastic film, such as polyamide. The final thermoplastic composite shows unique properties in terms of its repairability, and its performance was improved by increasing the number of repairing repetitions. For this aim, a repairability test was designed in the bending configuration, and three consecutive cycles of bending/repairing/bending were carried out. The static mechanical properties of the final thermoplastic composite were, conversely, low in comparison with traditional fiberglass because of the choice of a polyethylene matrix. The bending tests showed that the maximum strength was lower than 10 MPa and the elastic modulus was less than 1 GPa. Nevertheless, the toughness of the thermoplastic composite was high, and the samples continued to deform under bending without splitting into two halves.

Glass serviceability limits: new evidence from human-centred studies

AbstractThe performance of the building envelope is crucial for minimizing operational carbon emissions of buildings and maintaining indoor comfort. Contemporary building envelopes, such as engineered glazed façades, achieve high performance levels but often add a significant amount of embodied carbon. There is therefore an incentive to reduce the thickness of the glass panels, but the minimum thickness possible is often not governed by strength or manufacturing limits but rather by the deflection (serviceability) limits. Despite objective criteria guiding serviceability limits, user acceptance of deformation remains unexplored, leading to conservative designs. This paper introduces a novel method for measuring user satisfaction with glass deformations, aiming to establish acceptance thresholds comparable to objective criteria. The study involves a novel experimental campaign to assess volunteers' levels of perception and acceptance of various glass deformations. The glass was deformed using a bespoke electro-pneumatic system at levels corresponding to below, above, and at the current serviceability limit. The results demonstrate the feasibility of measuring human responses to deformations in the glazing and provide essential data for setting serviceability limits. The experiments and corresponding user satisfaction feedback indicate that the current serviceability limit of L/50, may be relaxed, thereby presenting opportunities for material efficiency, such as the adoption of thinner glass in facades. The methodology effectively captures human responses, revealing that changes in reflection were the primary reason for the perception of movement; leading to a higher perception of glazing movement and a lower acceptance at night. Overall, participants felt safe regardless of their prior knowledge on glass properties, and providing this information to participants did not improve acceptance, which was already sufficiently high. The findings from this research fill an important knowledge gap in understanding user acceptance of glass deformations, crucial for comprehensive user satisfaction assessments and evidence-based reductions in glazing thickness.