Single-layer Panels Research Articles

Uncertainties and inaccuracies of micro-perforated and micro-slit panel absorbers in multiple layers

Multilayer micro-perforated/slit panels (MPP/MSP) are used to achieve broadband absorption in Architectural Acoustics. Both micro-perforated and micro-slit panels can achieve a high absorption coefficient, but the frequency bandwidth is usually narrow for single-layer panels. For this reason, the multilayer design is proposed to achieve a broadband high absorption coefficient. This work applies Bayesian inference to the design of multilayered micro-perforated/-slit panels for a given design scheme. A higher level of inference, Bayesian model selection, estimates the parsimonious number of layers needed to achieve the design scheme. The lower level of inference estimates MPP/MSP parameters once the structure of the multilayer design is chosen. Once the exact parameters and the model are given, the theoretical absorption coefficient is compared with the measurement results. The causal inference is further applied to analyze the possible reasons for the deviations between the model and the experimental data. Applying the Bayesian framework and causal inference minimizes the uncertainties and inaccuracies during the manufacture and leads to a satisfactory design.

Methodology of fabricating 3D printing modified plastic single-layer panels with UAV positioning technology in the era of mass customization

Mass customization of prefabricated architecture is becoming increasingly crucial for developing the architectural industry. Advanced technologies such as 3D printing and unmanned aerial vehicles (UAV) has brought opportunities and challenges for traditional fabrication and construction methodology. Based on these emerging digital design tools and intelligent construction methods, this paper presents a novel methodology for fabricating single-layer 3D printing panels using UAV positioning technology, which has the potential to revolutionize the construction process and enhance the overall efficiency. This paper first provides a comprehensive review of the existing technologies in 3D printing and UAV positioning, highlighting their benefits and limitations in the context of construction applications. Next, a step-by-step process for fabricating single-layer 3D printing panels is introduced, detailing the optimal design parameters, material selection, and printing techniques. The utilization of UAV for precise positioning and alignment of the panels is then discussed, including the development of an on-site installation for accurate control. To validate the proposed method, a construction practice of the Chengdu Agricultural Expo Centre is produced o demonstrate the promising manufacturing and installation of single-layer 3D printed panels using UAV positioning technology. The results indicate that this method significantly reduces construction time, material waste, and labour costs, while also demonstrating significant customization and design flexibility.

Solution of the plane problem of the theory of elasticity on bending of an articulated fixed multilayer panel with a circular axis

This article suggests a method for the solution of the plane problem of the theory of elasticity on the bending of an articulated fixed multilayered panel with a circular axis based on the polynomial approximation of displacements through the thickness of the panel. In contrast to the known solutions of this problem, in this case the coefficients of the approximating polynomials are calculated from the equilibrium conditions and equality of displacements and transverse stresses at the transition across the layer interface and solution of differential equations of equilibrium at several points through the thickness of the layers. Finally, the problem is reduced to the solution of a system of linear equations with respect to the coefficients of approximating polynomials. The validity of the method is confirmed by comparing the results of calculations obtained on its basis and the results obtained with the help of the reference finite element model. The problem is solved in two stages. At the first stage, for a single-layer panel, we investigate the dependence of the polynomial degree on the ratio of the average panel radius to its thickness and the ratio of the transverse shear modulus to the modulus of longitudinal elasticity, which characterize the nonlinearity of displacements. At the second stage, on the example of a three-layered panel, we consider the application of the proposed method for the calculation of multilayered panels. In such case, the results obtained at the first stage are used in selecting the initial degree of polynomials approximating displacements through the thickness of layers. The method proposed in this article makes it possible to obtain an analytical solution without introducing simplifying hypotheses about the nature of displacement of layers and their elastic characteristics in a wide range of variation in geometric dimensions and elastic characteristics of panel layers. This method can be used both for verification of numerical models and for carrying out strength calculations of multilayer panels.

Selected Properties of Single and Multi-Layered Particleboards with the Structure Modified by Fibers Implication.

One of the ways of potential improvement of the particleboard properties, especially surface quality, can be the incorporation of wood fibers to face layers. This study aimed to evaluate the selected mechanical and physical parameters of single and multi-layered particleboards with the structure modified by the incorporation of various types and amounts of wood fibers. Single, 3- and 5-layers particleboards were produced with two different types of wood fibers added to the face and core layers. The basic mechanical parameters (modulus of rupture, modulus of elasticity, internal bond, surface soundness), as well as density profile and surface roughness, have been investigated. The results have shown that the single-layer panels with fibers did not meet the standard requirements due to unsatisfactory unstable parameters, probably caused by uneven resination. The remaining panels, 3- and 5-layer, met the standard requirements, and, due to fiber incorporation, there is also potential to reduce the panel density, still meeting standard requirements. The addition of fibers from 0% to 75% in face layers leads to an increase in the modulus of rupture from 10.6 N mm-2 to 15.6 N mm-2. Depending on the fibers' type, the surface soundness can vary between 0.7 N mm-2 and 1.2 N mm-2. Five-layer panels were of similar or even higher parameters, but due to much-complicated technology, it seems unreasonable to develop this type of composite. The novelty of the conducted research is the attempt to modify the structure of particleboards by adding various amounts of two different types of fibers by mixing them with particles or adding them as separate layers and producing panels of different densities.

Numerical and experimental study of an active control logic for modifying the acoustic performance of single-layer panels

This work proposes an active control logic that uses a linear quadratic regulator (LQR) controller and a Kalman-Bucy (KB) state observer to improve the acoustic performance of single-layer panels. When the panel is subjected to an acoustic excitation, the proposed strategy can automatically adapt to the acoustic disturbance by tuning some of the decisive weighting factors in the LQR and the KB filter according to the spectrum of the signals from sensors. This control acts on the panel with PZT patches as actuators and accelerometers as sensors, forming a smart structure. The vibroacoustic model of the smart panel is formulated using modal functions, from which the transmitted power and the transmission loss of the panel are derived. Accordingly, the control strategy is designed using the state-space representation under modal coordinates, during which the spillover effect is considered and the placement of actuators and sensors is optimized by a modified modal H2 norm approach. It is noticeable that several advanced techniques in the active control of noise and vibration are implemented in this development of the smart panel. Following this, numerical and experimental studies oriented to the effectiveness of the proposed control logic are performed. While the numerical simulations are carried out under the assumption that the two sides of the panel are a reverberant and a free field, respectively, the experiments are conducted using the test equipment called Noise-Box, whose inner space is considered able to simulate a field incidence. Two scenarios are provided: one for the monotone at 500 Hz or 1,000 Hz; the other for the white noise within 750 Hz – 1,000 Hz. The results validate that the active control improves the acoustic performance of the panel for sound insulation, whether the acoustic disturbance is a monotone of any frequency or a band-limited noise with a given frequency range.

Plastic Forming of Sandwich Panels and Numerical Analyses of the Forming Processes Based on Elastoplastic Equivalent Model.

This paper studies the plastic forming of sandwich panels and proposes a universal elastoplastic equivalent method suitable for sandwich panels. To verify the generality of the equivalent method, according to the different core structures, the cores of bi-directional trapezoidal sandwich (BTS) panels and aluminum foam sandwich (AFS) panels are equated to orthotropic and isotropic (special orthotropic) single-layer panels respectively. Through the finite element (FE) numerical simulation of the mesoscopic model of the sandwich panel, the elastoplastic constitutive relationship of the equivalent core model is established, and then the macroscopic equivalent model of the sandwich panel is established. The FE numerical simulation of plastic forming was carried out for the mesoscopic model and equivalent model of BTS panel and AFS panel, and plastic forming experiments were conducted for the sandwich panel through a multi-point forming (MPF) test machine. The results show that the relative errors of the section average stress at the same position of the equivalent model and the mesoscopic model of sandwich panels are all within 4%; compared with the experimental results, the equivalent model of the sandwich panel has high forming accuracy and small shape error, which verifies the high accuracy and generality of the equivalent method. Moreover, using the sandwich panel equivalent model effectively reduces the calculation time of the numerical simulation.

Some of the Physical and Mechanical Properties of Particleboard Made from Betung Bamboo (Dendrocalamus asper)

The objective of this study was to evaluate various physical and mechanical properties of experimental particleboard panels made from Asian giant bamboo (Dendrocalamus asper). Single layer panels having a density level of 0.75 g/cm3 from coarse and fine particles were used within the scope of this study. Thickness swelling, water absorption, surface roughness, and wettability characteristics of the samples were tested as physical properties while bending, internal bond strength, and screw withdrawal strength of the panels were considered for their mechanical properties. Resistance of the panels against termite and fungus were also determined. Based on the findings in the work both physical and mechanical properties of the panels made from coarse particles resulted in higher values than those made from fine particles with the exception of their internal bond strength. It appears that using fine particles in the panels enhanced their overall surface quality as well as wettability. Regarding biological deterioration of the samples, those made with coarse particles had better resistance. It seems that giant bamboo as a non-wood lignocellulosic species would have potential to be used as raw material to the manufacture value added particleboard with accepted characteristics.

Utilization of the western juniper (Juniperus occidentalis) in strandboards to improve the decay resistance

Naturally durable wood species such as western juniper (Juniperus occidentalis) are a potential source of bio-based wood preservatives for the improvement of non-durable timber species. This research investigated the durability of southern yellow pine (Pinus sp.) and western juniper lumber or strandboard. Single layer panels were made with six different types of wood or wood treatments: southern yellow pine, mixed juniper sapwood and heartwood, sapwood, heartwood, sapwood strands impregnated with juniper oil prior to and after panel manufacturing. Panels were fabricated with 560 kg/m3 oven-dry density with 5% of PF resin and 0.5% of wax. Durability testing was performed with the brown rot fungi Gloeophyllum trabeum and Rhodonia placenta and the white rot fungus Trametes versicolor. Internal bond as a crucial parameter of OSB was measured. Tests revealed that juniper heartwood and juniper heartwood strandboards were highly decay resistant, and juniper oil pre- and post-impregnation strandboard manufacture imparted increased resistance to decay against one brown rot fungus, Gloeophyllum trabeum. Juniper strandboard manufactured from non-impregnated strands showed significantly higher internal bond than pine. These results suggest there is excellent potential for manufacturing highly decay-resistant OSB from juniper, especially from heartwood and that juniper oil can increase the durability of juniper sapwood strandboard.

Experimental Studies of the Elastic-Dissipative Properties of Structural Materials and the Calculation of Sound Insulation of Building Partitions Based on Refined Characteristics by the SEA Method

An analytical solution to the problem of sound and vibration transmission through structures, taking into account the energy exchange with adjacent structures, requires determination of the elastic-dissipative properties of structural materials: the elastic modulus and the loss factor. In this work, the parameters of the elastic modulus and the loss factor of three known building materials are investigated and experimentally established in comparison with previously obtained data of other authors. For the automation and accuracy of measuring the internal loss factor, a new measurement technique was transferred using Zetlab software and digital equipment. The calculation of sound insulation of a single-layer enclosing structure is performed based on the method of statistical energy analysis (SEA) using the measured data of the elastic modulus and loss factor. In order to determine the reliability of the data obtained for the elastic modulus and the coefficient of internal loss of structural materials, a comparison was made of the values of sound insulation of a single-layer panel made of gypsum fiber board, obtained by means of experimental research, using the calculated values of sound insulation calculated using the elastic modulus and the coefficient of internal losses from literature sources and using the calculated sound insulation values calculated using the measured values of the modulus of elasticity and the internal loss factor.

Properties of the western juniper (Juniperus occidentalis) strandboard

This work investigated the feasibility of using western juniper (Juniperus occidentalis) as a material to manufacture oriented strandboard (OSB) panels. Four different material combinations of juniper sapwood, heartwood, and fibrous bark were compared with regular southern yellow pine (Pinus sp.) strands. The OSB panels were made at an oven-dry density of 560 kg/m3. One pine control panel was also made at a higher density of 650 kg/m3 with a 5% addition of phenol formaldehyde (PF) resin and a 0.5% addition of wax. The single-layer panels were formed with a hot press, and the physical and mechanical properties were tested according to the ASTM standard D1037 (2020). The testing indicated that western juniper is a potential material for manufacturing of OSB panels. The properties of the juniper panels were equivalent or slightly better than those of the southern yellow pine panels at the same density level, except for the modulus of elasticity (MOE). The lower density of the juniper OSB panels may have benefits in construction applications and can decrease transportation costs.

Oblique impact behavior of Al-LDPE-Al sandwich plates

Abstract Metal-polymer-metal hybrid sandwich panels are gaining importance in various industrial applications due to their light weight and damping properties. When compared with composite materials, hybrid materials consisting of separate metal and thermoplastic parts can be recycled more easily. In addition to their applications in civil engineering, the aluminum-low density polyethylene-aluminum (Al-LDPE-Al) sandwich panels yield a potential use as light ballistic protection material. In this study, a standard hybrid panel of 3.2 mm polyethylene filling and 0.4 mm of two aluminum metal sheets was experimentally tested under ballistic impact. A finite element model was constructed via commercial software and validated through shooting experiments with a rifle under real conditions. The finite element model was used to simulate the oblique impact behavior of Al-LDPE-Al sandwich panels as a single layer, as 5 layers stacking and as a single layer equivalent of the stacked 5 layer. Results showed that the oblique impact does not have a significant effect on the single layer panel. Stacked layers, however, and the equivalent single layer of a stacked layer have the highest energy absorption under a 30° hitting angle.

Enhanced design of hourglass truss sandwich structures for compressive resistance

In this article, the design of the hourglass truss sandwich structure is improved by optimizing the number of layers to enhance the compressive strength of both the core and the face sheet and then its mechanical performance. The hourglass truss structures characterized by three different numbers of layers are manufactured using an interlocking and vacuum brazing method. The effect of the layer number of the hourglass core panels on their out-of-plane compression and in-plane compression performance is investigated, and the results from calculations and experiments are in reasonable agreement. The results show that as the layer number of the hourglass core increases, the out-of-plane compressive strengths show little change, but their energy absorption properties are effectively increased. The in-plane compressive failure mechanism maps are constructed, and the specimens are designed to examine the local elastic and inelastic buckling failure modes of the face sheets. The results suggest that as the number of layers of the hourglass core increases, its maximum in-plane compressive load increases. The maximum in-plane compressive loads of the two-layer hourglass truss panels are 57%–70% higher than those of the single-layer panels. It can also be concluded that the out-of-plane and in-plane compression mechanical properties of the multilayer hourglass truss outperform those of the pyramidal truss. Furthermore, the number of layers of the hourglass core is optimized in consideration of both mechanical properties and fabrication cost.

Oblique impact behavior of Al-LDPE-Al sandwich plates

Abstract Metal-polymer-metal hybrid sandwich panels are gaining importance in various industrial applications due to their light weight and damping properties. When compared with composite materials, hybrid materials consisting of separate metal and thermoplastic parts can be recycled more easily. In addition to their applications in civil engineering, the aluminum-low density polyethylene-aluminum (Al-LDPE-Al) sandwich panels yield a potential use as light ballistic protection material. In this study, a standard hybrid panel of 3.2 mm polyethylene filling and 0.4 mm of two aluminum metal sheets was experimentally tested under ballistic impact. A finite element model was constructed via commercial software and validated through shooting experiments with a rifle under real conditions. The finite element model was used to simulate the oblique impact behavior of Al-LDPE-Al sandwich panels as a single layer, as 5 layers stacking and as a single layer equivalent of the stacked 5 layer. Results showed that the oblique impact does not have a significant effect on the single layer panel. Stacked layers, however, and the equivalent single layer of a stacked layer have the highest energy absorption under a 30° hitting angle.

Experimental study on bending and shear behaviours of composite timber sandwich panels

Composite sandwich panels were manufactured by gluing plywood skins to either bamboo rings to produce Bamboo Core Sandwich (BCS) panels or to peeler core rings to produce Peeler Core Sandwich (PCS) panels. Single and double core layer panels were made. The optimum adhesive spread rate was identified through conducting shear bond tests. The manufactured panels were physically tested in standard bending (using four-point) and shear (using three-point) tests. Results were compared to the test results of conventional Cross-laminated Timber (CLT) panels with almost similar depth. Under bending action, both the BCS and PCS panels showed tensile failure in the plywood, while the plywood in compression exceeded its plastic limit at the ultimate load. In shear, BCS panels failed due to the loss of shear interface contact between bamboo core rings and the plywood skins, whereas PCS panels showed local indentation/bond failure between the peeler core rings and the plywood skins. No significant improvements were observed in the double-layer panels compared to single-layer panels in bending. However, in shear, double-layer panels showed more consistent capacities. One PCS panel with thicker plywood skins and less peeler core rings (PCS-TH) was manufactured, and was shown to achieve 0.77 times the bending stiffness-to-weight ratio of the commercial CLT panel. Reduced weight, lower material costs, ease of manufacturing and usage of sustainable/waste products, make the proposed sandwich panels a potential alternative for CLT in terms of structural performance. Moreover, the proposed peeler core sandwich panels displayed better ductile performances in bending and shear compared to CLT suggesting it could be a preferred product choice in some building applications.

Evaluation of recycled Al–LDPE–Al sandwich panels as ballistic protection material

Metal–polymer–metal hybrid sandwich panels are gaining importance in civil, automotive and aerospace applications due to their light weight and damping properties. Compared with composite materials, hybrid materials consisting of separate metal and thermoplastic parts can be recycled much more easily. Besides their applications as covering material on buildings as well as general insulation material, recycled aluminum (Al)–low-density polyethylene (LDPE)–aluminum hybrid panels yield a potential usage of light ballistic protection. In this study, a standard hybrid panel of 3·2 mm polyethylene filling and two 0·4 mm aluminum metal sheets was experimentally tested under ballistic impact. A finite-element model was used with a commercial software program and validated against the experimental results. The finite-element results show that stacking of multiple layers of panels absorbs more energy than an equivalent single-layer panel. Six layers of stacked hybrid aluminum–LDPE–aluminum panels are capable of absorbing the impact energy of a 9 mm pistol projectile, and they can be utilized as recyclable inexpensive ballistic protection materials.

Finite-element Analysis of Cotton Serrated Ginning State Based on Three-dimensional Braided Modeling

ABSTRACT In order to analyze the stress state of the seed cotton in the process of ginning cotton, a theoretical model for cotton, namely three-dimensional braided cotton was developed. The model consists of cotton fiber bundles arranged according to the unit cell structure of a three-dimensional four-directional braided composite material. The fiber bundle has a circular section and the shape of the cross section remains unchanged along the axial direction. Based on this model, the serrated ginning process is simulated using finite-element analysis. By analyzing of the effects of different moisture regain and speed on the serration cotton ginning process, the results show that the simulation results agree with the actual situation and the model has certain applications. Compared to the laminated cotton model, the three-dimensional braided cotton model has been improved obviously. In terms of model structure, the three-dimensional braided cotton model is closer to the actual situation of cotton than the existing laminated cotton model. The whole model in the laminated cotton model is an entity, which is bonded together by multiple layers of single-layer panels at different angles. The three-dimensional braided cotton model takes into account the intertwining of fibers and apces, but does consider the distribution of cottonseed which will be the focus research.

Development of a method for optimization calculation of a group of sound-insulating panels for airborn noise protection

Various designs and procedures for calculating soundproof panels for protecting premises against airborne noise were considered. These procedures make it possible to calculate single-layer, two-layer and three-layer panels. Single-layer panels may consist of homogeneous solid and thin materials. Two-layer panels may consist of two thin layers of different thickness and an air gap. Three-layer panels can be made of two thin layers of different thickness and a sound-absorbing material between them. These procedures enable calculation and optimization of individual structures of sound-proofing panels independently of each other. The problem of simultaneous penetration of noise from one source into several adjacent rooms was considered. When using the procedures considered in references, maximum effect is unattainable. In this regard, a method of optimization calculation of a group of sound-proofing panels aimed at achievement of the most advantageous value of the objective function was proposed. The method is based on a random search resting on random distribution of typical structures and procured materials among panels. Choice of the best result is made proceeding from a result of checking fulfillment of limiting conditions. The following options of the objective function were proposed: the excessive noise load, the total index of noise reduction in rooms, the total cost of sound-proofing panels and the number of panels made. Recommendations were given on the choice of the objective function option taking into account concrete production conditions. The result of optimization consists in the choice of design of the panel for each room and distribution of available materials among them. Formulation of the optimization problem with various options of the objective function and limitations has been considered. Efficiency of using this method was confirmed by almost 24 % lower cost of panels compared to the separate panel designing using conventional methods.

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

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

Crashworthiness of cardboard panels reinforced with braided glass fiber rods for vehicle side impact protection

This paper investigates the quasi-static compression properties of cardboard panels reinforced with braided glass fiber rods manufactured using a tubular braiding method. Compression tests are performed on single- and two-layer panels reinforced with varying number of rods and panel layer orientation. The crushing results of single-layer panels show more progressive crushing behavior than those of two-layer panels for different number of rods. In two-layer panels, certain rods are inclined from the direction of applied load due to deformation of the surrounding cardboard, resulting in reduced specific energy absorption compared with single-layer panels. Moreover, panels consisting of two layers of cardboard oriented in the same direction perform better than when the layers are off-set 90° where cardboard shifting is more pronounced. The role of cardboard is to constrain the rods from excessive splaying, causing greater levels of fiber fragmentation which consumes more energy compared with rods without cardboard.

A new approach for bending analysis of bilayer conical graphene panels considering nonlinear van der Waals force

Abstract In the present study, the effects of nonlinear van der Waals forces on the bending analysis of orthotropic bilayer conical graphene panels are investigated. In order to model the nano-sized panels, the first-order shear deformation shell theory is used to obtain the governing equations by applying energy method in nonlocal form. Semi-analytical polynomial method (SAPM) is utilized to solve the resulting nonlinear governing equations. Due to cover a wide range of geometric shapes, the geometry is considered as a conical panel, so the results can be simulated for cylindrical panels, annular sectors, and even rectangular plates. The van der Waals force between upper and lower layers of graphene panel is simulated by an extension spring with the linear and nonlinear stiffness. It is easy to obtain the results of single-layer panels by eliminating the van der Waals force, and also for macroscopic plates, with neglecting the nonlocal effects. Finally, the affecting parameters on the results are examined in detail such as the plate size, orthotropic effects of material, nonlocal effects, van der Waals force including its nonlinear term and various types of boundary conditions, even the free edges.