Panel Thickness Research Articles

Numerical and experimental assessment of optimal modeling of laminated glass post-breakage response

Modeling laminated glass response to extreme loading scenarios is a computationally demanding process in designing and analyzing protective structures. Therefore, an optimal modeling scheme requires a delicate trade-off between accuracy and computational demand. This article investigates the failure modeling of laminated glass layups of thin and thick panels (three and 11 layers) under blast loading. This is done by implementing various simulation techniques: the finite element method with element erosion/deletion, the mesh-free method of smoothed particle hydrodynamics, and the hybrid implementation of mesh-based and mesh-free simulation through element conversions into particles. This Article examines the feasibility and limitations of each method, considering both the aspects of accuracy and computational cost in light of experimental testing results obtained from both arena and shock tube scenarios. Mesh sensitivity and the significance of adaptive meshing in capturing the fracture patterns are evaluated. The present paper suggests that using hybrid techniques leads to optimal modeling results. Furthermore, the stability of the modeling results under diverse blast conditions is verified.

Multi-objective optimization for snap-through response of spherical shell panels

Composite spherical shell panels are commonly used for the lightweight design of thin-walled structures in the structure, architecture, aerospace engineering. Depending on the shell panel length, thickness, curvature, and stacking sequence, the load-deflection response under lateral load can be either a completely stable equilibrium path or an unstable snap-through path. In this work, the response of simply supported cross-ply composite spherical shell panels subjected to lateral static loads is studied and optimized. The spherical shell exhibiting snap-through response is optimized to (a) maximize the load required to initiate snap-through and (b) minimize the unstable region. Meanwhile, the spherical shell exhibiting continuous response is optimized to (a) maximize the softening-hardening load and (b) minimize the shell weight. The decision variables for both constraint multi-objective optimization (CMOO) problems include layup sequence, thickness, and the radius of curvature to side length ratio. The nonlinear governing equations are derived based on Kirchhoff–Love hypotheses for thin shells and Hamilton's principle. A novel semi-analytical method is presented based on Bernstein polynomials combined with a fast iterative approach to compute the objective features of the responses. Benefiting from the high efficiency and robustness of the proposed approach, the CMOO problems are solved by the metaheuristic Multi-Objective Artificial Hummingbird Algorithm (MOAHA). Composite spherical shell panels with various geometry and lamination configurations are considered to validate the performance of the proposed method. The optimization of geometric parameters (shell curvature and thickness) in addition to the staking sequence provide a high degree of tailoring of the shell performance to meet various objectives. These parameters are taken as design variables that must be optimized to achieve some objectives and satisfy arbitrary nonlinear constraints.

3D-printed polylactic acid-microencapsulated phase change material composites for building thermal management

The integration of phase change materials (PCM) into architectural elements is an emerging strategy to enhance thermal energy storage in modern buildings. This research examines 3D-printed polylactic acid structures incorporated with microencapsulated PCM, targeting a more efficient thermoregulation in foundational architectural sections such as walls, floors, and ceilings. Through rigorous evaluations, the polylactic acid-PCM composite revealed promising thermoregulatory properties. Notably, latent heat values stood at 198.4 J/g for melting and 197.9 J/g for freezing. Real-world experiments demonstrated a distinct advantage, maintaining temperatures 3.2°C–3.3 °C higher than standard polylactic acid at night and exhibiting a cooler range of 10.4 °C–13.3 °C during daylight. Within specific geographical contexts, like the Mediterranean and Aegean Seas coastline, 0.026 m thick polylactic acid-PCM panels stood out, registering 100 % energy savings. The findings consistently showed that an increase in panel thickness correlated with a decrease in building heating needs. Further analysis explored the carbon emissions landscape. Coal, when utilized with 0.05 m-thick polylactic acid-PCM panels, was identified as particularly effective, yielding a reduction of 34 kg/m2 in annual CO2 emissions. Collectively, the findings underscore the transformative potential of polylactic acid-PCM composites, positioning them as pivotal tools for advancing architectural energy efficiency and fostering sustainable building innovations.

Load bearing investigations on novel Acrylonitrile butadiene styrene‐carbon quantum dots 3D printed core/bamboo fiber polyester sandwich composite for structural applications

AbstractIn this research, a novel 3D printed core and natural fiber polyester composite skin based thick sandwich panel was developed as structural material for domestic and commercial infrastructure applications. The main objective of this research was to analyze how the carbon quantum dots (C‐dots) from agriculture waste strengthen the softer thermoplastic acrylonitrile butadiene styrene (ABS) core and overall sandwich panel's load bearing properties. The core of sandwich was prepared using additive manufacturing method whereas the skin was developed by hand layup method. According to the results the C‐dots of 20 phr into the ABS improved the compression properties of core in both flatwise and edgewise directions. A highest tensile and flexural strength of skin was observed to be 114 and 146 MPa respectively. The addition of C‐dots improved the load bearing effect and also restricts the deformation against load. This performance improved novel 3D printed core and bamboo fiber skin sandwich could be used as an alternative construction and building material where the commercial plywood and other forms of powder wood face damages via weather and termite issues.Highlights Higher filler volume of up to 20 phr of carbon quantum dots in acrylonitrile butadiene styrene (ABS) were developed Novel 3D printed thin walled core of 1 mm diameter was developed using carbon quantum dots and ABS. Bamboo fiber‐polyester skin with highest tensile strength of 114 MPa was developed. Improved flatwise compression and tensile strength were achieved for ABS core with 20 phr of Carbon quantum dots Flexural strength and edgewise compression properties were improved with 20 phr of Carbon quantum dots in ABS

Impact responses of the steel-PU foam-concrete-tube multilayer energy absorbing panel: Numerical and analytical studies

The enhancement of structural protection can be achieved by using energy absorbing structures as sacrificial layers. In this study, a new steel-PU foam-concrete-tube multilayer energy absorbing panel (SFCTMEAP) is developed to improve the impact resistance of buildings and infrastructures, and its behaviour under impact loading is numerically and analytically studied. A Finite Element (FE) model is established using LS-DYNA to further study the behaviours of SFCTMEAP, and its results (including the failure mode, displacement–time and impact force–time curves) agree well with the test data. The SFCTMEAP presents a deformation mode of local indentation of the front energy absorbing layer, flexure of the steel-concrete-steel panel and collapse of PU foam-filled steel tubes (PUFSTs). The energy dissipations of variant components of the SFCTMEAP are obtained through the FE model and the PUFSTs is the main energy absorbing component. In addition, parametric studies are performed to obtain the influences of the impact location, initial momentum of impactor and thickness of PU foam panel on the response of SFCTMEAP. The results indicates that the specimen with larger impact eccentric distance dissipates less impact energy, and raising the initial momentum of the impactor is benefit to the energy dissipation by the PUFSTs. Moreover, an analytical model is developed to calculate the displacement history of SFCTMEAP under the impact loading. The displacement responses predicted by the analytical model are found to be in good agreement with the test results.

Establishment and applicability verification of hysteretic model of shear wall bottom corner dampers

In this study, the experimental results of a shear wall bottom corner damper (SWBCD) were investigated. It was found that the effects of the corrugated shear panel thickness, corrugated shear panel length, and flange plate thickness on the seismic performance from large to small. The failure process of the specimens was summarized; it was found that the high stiffness at the bend contributed to failure of cross-cracks in each long corrugated band of the corrugated shear panel in all specimens due to the geometric shape constraints of the corrugated shear panel. According to the calculation method for the skeleton curve parameters and the hysteretic rules of the SWBCD, a multilinear hysteretic model of the SWBCD was established. Using a corrugated steel plate-reinforced concrete composite shear wall with bottom corner dampers (RSPCW) as the application background, based on the layer shell model, a reasonable equivalent simulation method for an embedded corrugated steel plate based on the tension strip model was proposed. The hysteretic model of the SWBCD was modified according to the deformation requirements of the bottom corner damper. The twoNodeLink element representing the SWBCD was placed in the height range under the boundary element at both ends of the RSPCW. The ability of the hysteretic model to accurately reflect the nonlinear analysis of the SWBCD was verified.

Configuration Design and Dynamics Simulation Analysis of Deployable Exposure Experiment Platform

Aiming at the problem that the traditional rigid exposure experiment platform takes up too much launch space and consumes high launch cost, a thick panel kirigami method is used to propose a deployable thick panel model for the exposure experiment platform, which realizes the plane of the thick panel. In the unfolding design, the unfolding process simulation of the structure was carried out, the influence of different hinge position drives on the dynamic behavior of the structure unfolding was studied, and the kinematics laws of the structure unfolding process under different driving modes were summarized. The new deployable exposure experiment platform provides new ideas for the development and application of practical engineering in the future, and the dynamic simulation also provides a driving strategy for it.

Optimization of micro-perforated panel absorber backed with parallel-arranged cavities of different depths

Micro-perforated panel absorber (MPA) is one of the most effective materials in noise control. For the MPA backed with parallel-arranged cavities of different depths (PCD-MPA), the panel thickness, perforation diameter, perforation rate, and cavity depth are essential parameters for absorption performance. In this study, a Genetic Algorithm (GA)-based optimization design method for PCD-MPA is proposed to achieve specific performance objectives. Firstly, a prediction model for absorption performance of PCD-MPA is proposed. Secondly, a GA optimization method suitable for PCD-MPA is established, taking into account interactive parameters and generating multi-objective and high-quality optimal solutions through iterative adjustments. Finally, an acoustic standard sample was fabricated for experimental validation and compared with analytical results. The findings demonstrate that the proposed optimization method can achieve nearly perfect absorption with a well-selected combination of parameters that meet specific absorption requirements.

Deployment dynamics of thick panel Miura-origami

Origami and kirigami folding methods applied to deployable structures have been investigated in many studies, and most of them use approximately zero-thickness materials to follow the paper-folding movement. However, the rigidity and thickness of materials cannot be neglected in aerospace engineering applications, resulting in different kinematic and dynamic characteristics of deployment. This work deals with the deployment dynamics of a typical thick panel Miura origami (Miura-ori). The kinematics of the Miura-ori unit and array are discussed considering the tessellated extension of the Miura-ori pattern, which can be described by the recursively relative movement. Based on the Lagrange's equation, the dynamic equation is determined by generalized force and potential energy. Furthermore, prototypes for Miura-ori unit and array are fabricated, respectively. To measure the dynamic behaviours during deployment, a gravity compensation apparatus is designed and constructed, which can effectively reduce the gravity effect of Miura-ori prototypes. The comparison of the numerical and experimental results validates our dynamic model. Our work provides a recursive dynamic modelling method and experiment apparatus for analysing and testing the deploying dynamic behaviours of tessellated thick-panel origami deployable structures, and the findings can be developed in the other thick-panel origami and kirigami concepts of actual engineering applications in the future.

The novel synthesis of origami-inspired mechanisms based on graph theory

In this paper, a novel synthesis approach based on graph theory is proposed. This approach can be used to design the creases of origami mechanisms. All possible contracted graphs of the 1-DOF origami mechanism are provided based on the number and graph synthesis methods. Then, a new method named loop synthesis is presented and this method is used to obtain different loop situations of the contracted graphs considering the structural characteristics of the origami mechanism. Two theorems are proposed and proven to determine the availability of loop situations. Furthermore, a modified thick panel design method for the origami mechanism is presented, and both single units and multiple units of the origami mechanism are modelled. At the same time, a rotary actuator based on this mechanism is introduced to verify the validity of the above synthesis approach. Finally, rotation, repeatability, and static torque tests are conducted to measure the inherent stiffness constant of the actuator. This approach, which was proven to be effective for designing the origami mechanism, can be readily applied to generate the desired mechanism.

Layerwise models for supersonic flutter analysis of viscoelastic sandwich panels with curvilinear fibre composite skins

In this work, an assessment of layerwise finite element models for supersonic flutter analysis of soft core viscoelastic sandwich panels is presented, making use of various kinematic descriptions involving shear deformation theories and Lagrange z-expansions with thickness stretching, progressively refined to render numerically accurate and computationally efficient solutions. Numerical applications of sandwich panels include either viscoelastic or purely elastic core with skins of metal or laminated composite, using unidirectional or curvilinear fibres, considering thin and moderately thick panels, with core thickness ratios ranging from narrow to wide cores. A comprehensive assessment of the models predictive capabilities in free vibration analysis is carried out by comparison with three-dimensional exact solutions and numerical methods available in the literature. Even though it is concluded that layerwise first-order modelling, with no thickness stretching, ensures a fair compromise between numerical accuracy and computational efficiency in the aeroelastic flutter analysis of thin sandwich panels, layerwise high-order theories accounting for thickness stretching are rather necessary for the proper modelling of moderately thick sandwich panels, with either viscoelastic or purely elastic core.

Experimental and numerical study on dynamic behavior of laminated glass window under combustible gas explosions

In this paper, full-scale field tests and numerical simulations are used to study the dynamic behaviour and destruction process of the laminated glass windows under combustible gas explosions. The blast overpressure caused by the explosions of combustible gas, the mid-span displacement and damage process of the windows were all documented during the field tests. The results are analyzed and presented in this paper. It is found that the laminated glass windows under blast loads of combustible gas explosions exhibit a characteristic bending failure, which differs from those under high explosives explosions. Numerical model of dynamic behaviour and destruction of laminated glass windows is developed in LS-DYNA and validated by the test results. The factors affecting the resistance of laminated glass windows to explosions of combustible gas are analyzed through numerical simulations. The results show that increasing the thickness of the glass panel and the interlayer, using soft supports and providing sufficient bite depth for the laminated glass window can significantly enhance its capacity to resist combustible gas explosions.

Blast Resistance in Sandwich Structures Based on TPMS

This study analyzes the blast resistance in triple-period minimal surface (TPMS) sandwich panel structures with a cellular structure. The explosion test of the TPMS sandwich panel was carried out, and experimental data verified the effectiveness of the finite element model. Four TPMS configurations, Diamond, Gyroid, IWP, and Primitive, were selected as the core of the sandwich panel to determine the dynamic response process of the TPMS sandwich panel under the action of a blast load. The effects of the thickness of the core material and the explosive charge on the blast resistance in the TPMS sandwich panel were investigated. The results show that the increase in core thickness reduces the blast energy absorption efficiency of the sandwich panel, and the energy resistance in the Diamond configuration sandwich panel is stronger than the other three configurations under the same blast load; the increase in explosive charge significantly increases the displacement of the sandwich panel, and the Gyroid configuration shows better energy absorption effect; different TPMS configurations and panel thickness have a significant effect on the deformation and energy absorption of the sandwich panel under the blast load. The results of this study can promote the application of TPMS sandwich structures in blast-resistant structures.

Seismic behaviors of CFT-column frame-four-corner bolted connected buckling-restrained steel plate shear walls using ALC/RAC panels

A Frame-Buckling Restrained Steel Plate Shear Walls (BRSPSWs) system has been designed, featuring a steel plate connected to frame elements, to withstand lateral loads like seismic or wind forces. This system incorporates recycled aggregate concrete (RAC) to create concrete-filled and concrete panels, promoting eco-friendly and sustainable construction materials. Two single-span, two-floor specimens were tested under cyclic quasi-static load. A four-corner bolted connection was used to connect the steel plate to the square concrete-filled steel tubes (CFTs) column and H-section beam, minimizing the potential deformation of the frame elements produced by the tension field of the steel plate after high-order bucking. The steel plate was sandwiched using either autoclaved lightweight concrete (ALC) or RAC panels. The study analyzed failure modes, load-displacement responses, and characteristic capacities. Test results inferred that BRSPSWs exhibited favorable cyclic behavior, with similar failure modes observed using both ALC and RAC panels. The buckling of steel plates was reduced, and the type of restrained panels had a negligible impact on buckling. Consequently, ALC panels can effectively replace RAC panels. Furthermore, bearing capacities and yield stiffness were primarily determined by the bolted connection forms. A finite element (FE) modeling was developed using ABAQUS software and validated against test results. This FE modeling method successfully simulated failure modes and load-displacement curves. Parametric analyses were conducted and revealed that bearing capacity and yield stiffness positively correlated with steel plate thickness, bolt diameter, and the number of bolts but negatively correlated with the axial compression ratio. In contrast, the panel thickness and span length had a minor impact due to shear deformation in the bolted connection. Based on the test results and parametric studies, an equation for the yield-bearing capacity of BRSPSWs was proposed and verified.

Out-of-plane shear performance of a novel non-metallic CLT dovetail joint subjected to monotonic and cyclic loading

Timber structures have garnered increasing attention owing to their sustainability and assemblability. Particularly, engineered wood products like cross-laminated timber (CLT) coupled with digital fabrication technologies have promoted the application of traditional mortise-tenon joints in modern mass timber structures. In this paper, a novel non-metallic dovetail joint was proposed to connect the perpendicular CLT wall and lintel. A total of nine specimens were tested under monotonic and cyclic loading to investigate the out-of-plane shear behavior with different widths of the tenon head. The failure modes of the joints were presented, and the mechanical properties including stiffness, strength, ductility and energy dissipation were compared and analyzed. A simplified strength model was developed to evaluate the shear strength of the joint. The experimental results revealed that the specimens mainly failed by timber splitting and crushing under monotonic loading due to the shear force and additional bending moment. The increase in the tenon head width of the dovetail joint from 70 mm to 105 mm resulted in a significant improvement in both stiffness and strength, with enhancements of more than 42 % and 54 %, respectively. All specimens exhibited similar failure modes but more severe timber crushing under cyclic loading. Due to the damage accumulation, the stiffness and strength of the dovetail joint degraded significantly. The specimen with the tenon head width of 84 mm exhibited the highest energy dissipation and relatively low strength degradation under cyclic loading. Additionally, it is recommended to use a ratio of tenon head width to CLT panel thickness at 4/5. The proposed strength model underestimated the load-carrying capacity of the joint generally due to the neglect of the contribution of the bending moment. This study provides base guidelines for the application of dovetail joints in CLT structures.

The temperature effects on embedded PZT signals in structural health monitoring for composite structures with different thicknesses

Ultrasonics guided waves (GWs) are established as an effective structural health monitoring technique for detecting damage in composite structures. However, for GWs to be applied reliably in service, the effect of temperature needs to be accounted for baseline damage detection approaches. Previous studies have focused on developing temperature compensation methods for surface-mounted transducers. In this paper, an extensive investigation has been carried out to develop an effective temperature compensation method for GWs generated by embedded transducers in different thickness composites. To accomplish this, Laser Doppler Vibrometer experiments were carried out to obtain wavenumbers generated by embedded transducers and to compare them against surface mounted cases. The consistent trend observation of dispersion curves between surface-mounted and embedded PZTs serves as a foundation for conducting analysis of the embedded signals with the effect of temperature. Following that, GW propagation has been studied in three quasi-isotropic composites of 2 mm, 4 mm and 9 mm thicknesses. Based on the established temperature database with measurements from − 50 °C to 70 °C, a temperature compensation methodology has been developed and validated with the temperature difference of 30 °C. It demonstrates that the temperature effect on the embedded PZTs is lower in comparison to surface mounted PZTs, and the temperature compensation of a single thickness composite is scalable to other panels thickness. This novel methodology proves beneficial in reducing the scale of the experimental campaign required, which holds significant value for actual aeronautical structures characterized by variable composite thicknesses across different sections, such as in fuselage panels or wing boxes.

Optimization Study of Driver Crash Injuries Considering the Body NVH Performance

Optimal body structure design is a central focus in the field of passive automotive safety. A well-designed body structure enhances the lower threshold for crash safety, serving as a basis for the deployment of other safety systems. Frontal crashes, particularly those with an overlap rate below 25%, are the most frequent types of vehicular accidents and pose elevated risks to occupants due to variable energy absorption and force transmission mechanisms. This study aims to identify an optimized, cost-effective, and lightweight solution that minimizes occupant injuries. Using a micro-vehicle as a case study and accounting for noise, vibration, and harshness (NVH) performance, this paper employs Elman neural networks to predict key variables such as the first-order modes of the body, the body’s mass, and the head injury values for the driver. Guided by these predictions and constrained by the first-order modes and body mass, a genetic algorithm was applied to explore optimal solutions within the solution space defined by the body panel thickness. The optimized design yielded a reduction of approximately 173.43 in the driver’s head injury value while also enhancing the noise, vibration, and harshness performance of the vehicle body. This approach offers a methodological framework for future research into the multidisciplinary optimization of automotive body structures.

Quantitative structural uncertainty analysis of composite honeycomb sandwich using a feedback neural network

The quantification of margins and uncertainty (QMU) method was applied using a neural network to inversely determine the strength boundary of a composite honeycomb sandwich structure considering the random uncertainty of its elastic modulus, shear modulus, tensile strength, compressive strength, and shear strength in the warp and fill directions, and panel thickness. An application framework for the deterministic quantitative analysis of strength was proposed based on margin design theory, combining the strength problem with the quantitative analysis of uncertainty. First, the failure criterion of the structure was modeled based on the progressive damage principle using ABAQUS. Next, Latin hypercube sampling was applied to simulate the stochastic uncertainty of the structural parameters, and the resulting sample sets were input into ABAQUS to calculate the corresponding structure lateral bearing capacities. These results were considered to collectively represent the actual strength boundary of the composite structure. A feedback neural network was subsequently trained on these ABAQUS data to obtain the functional mapping relationship between the parameters and capacity. The capacity obtained using this relationship was multiplied by an empirical safety factor to serve as the theoretical strength boundary. Finally, the QMU method was applied using cumulative distribution functions of the theoretical and actual strength boundaries to calculate the confidence factor and thereby evaluate the reliability of the composite honeycomb sandwich structure.

Effect of Core Density on the Three-Point Bending Performance of Aluminum Foam Sandwich Panels.

Using the powder-metallurgy rolling method, aluminum foam sandwich (AFS) panels with a metallurgical bond between the foam core and the panel can be produced. In this study, by manipulating the foaming temperature and duration, AFS panels were fabricated with varying core densities and thicknesses, all maintaining a panel thickness close to 1 mm. Through the three-point bending test, this research deeply delved into how core density influences the mechanical behaviors of these AFS panels. It became evident that a rise in core density positively affects the bending strength and failure load of the panels but inversely impacts their total energy absorption efficiency. Differing core densities brought about distinct failure patterns: low-density samples primarily showed panel indentation and core shear failures, whereas those of high density demonstrated panel yield and fractures. Furthermore, the research offers predictions on the initial failure loads for different failure modes and introduces a comprehensively designed failure diagram, laying a foundational theory for the production of AFS panels.

A deterministic energy method for predicting the response of coupled finite structures

The forced response of finite, thin rectangular plates coupled by a line joint can be predicted using well-established analytical methods. However, such methods become difficult to implement for thick panels coupled by complex joints. In these cases, the finite element (FE) method and conventional statistical energy analysis (SEA) are viable alternatives. However, the FE method can be time-consuming at mid/high frequencies while SEA involves various approximations and assumptions. This paper develops a deterministic energy method for predicting the forced response of coupled complex panels based on a hybrid finite element/wave finite element method (WFE), modelling the panels as coupled wave-bearing subsystems. Excitation of the structure by a time-harmonic point force is considered. The method involves meshing only a small segment of the panel and the joint using finite elements, and is able to model complex structures such as laminated panels and joints with low computational cost. An illustrative example of the method is presented - coupled thin, rectangular plates coupled by an "L" shaped joint.