Aluminium Sandwich Panels Research Articles

Experimental and numerical investigations on impact response of reinforced concrete beams with a sandwich panel protective layer

This paper investigates the response of reinforced concrete beams protected by an aluminium foam sandwich panel under impact loadings. A series of impact tests were conducted on one reinforced concrete beam and five beams with a protective layer, focusing on their dynamic responses and failure patterns. Test parameters included the type of protective layers (unprotected, aluminium foam and sandwich panel) and impact energy. Test results showed that the aluminium foam and sandwich panel could effectively protect the reinforced concrete beam from severe damage under impact loadings and converted the failure pattern of beams from shear failure to flexure-shear failure. Compared with the unprotected beam, the beams with a protective layer exhibited a lower peak force and developed a smaller mid-span deformation. Besides, the protective effects of the aluminium foam and sandwich panel were found to be nearly the same. Moreover, the peak force, plateau force and deformation of the beams were increased with the increasing impact energy. A numerical model was developed to investigate the energy distribution of beams with a sandwich panel protective layer. Based on the validated model, the effects of longitudinal reinforcement ratio and shear-span ratio on the impact response of beams were further studied. It was found that the deformation of beams increased significantly with the increasing shear-span ratio, whereas an increase in the longitudinal reinforcement ratio led to a decreased deformation. This study provides an important reference for designing reinforced concrete beams with a sandwich panel protective layer to resist impact loads.

Feature Engineering for Physics-informed Evaluation of Electromechanical Impedance Measurements for Sandwich Face Layer Debonding Identification

The present research exploits various physically explainable features for the evaluation of electromechanical impedance (EMI) measurements for sandwich face layer debonding identification using a recently published two-step physics- and machine-learning (ML)-based approach. In the previous work, the ML approach used employs a One-Class Support Vector Machine and a K-Nearest Neighbor model for debonding detection and size estimation, respectively. Feature engineering was used to compensate for the simplifications of the finite element (FE)-based physical model and a simple data calibration step was used to adapt to distribution shifts. This enabled to train both ML models exclusively with FE simulation-based synthetic EMI spectra data. The efficacy of the method was demonstrated on real-world EMI spectra measurements of a circular aluminum sandwich panel by a piezoelectric transducer. The considered face layer debonding damage was idealized and stepwise increased by a milling process. In the present work, we explore opportunities for further optimization of our method with respect to data distillation, where we reduce the computational requirements of both training and inference while at the same time preserving essential information. Furthermore, we investigate the usefulness of a separate approach for debonding detection, formulated as an anomaly detection problem. The data preprocessing and ML models are validated by unseen real-world EMI measurement data and benchmarked with the previously published damage evaluation results, considering both reliability and accuracy. The data and the code used in this study are provided in their entirety to enable reproducibility, enhance comprehensibility, and encourage future research.

Experimental crashworthiness analysis of corrugated-core sandwich panels under impact loading

ABSTRACT This research scrutinizes and contrasts the crashworthiness of single-core and two-core corrugated sandwich panels with varying configurations, influenced by crucial parameters like thickness, core angle, and foam filling. Experimental investigations encompass quasi-static compressive loads and low-velocity impact tests on these sandwich structures. Employing the design of the experiment (DOE) method, the study examines parameter impacts on initial peak crushing force (IPCF) and specific energy absorption (SEA) across three sequential steps. The fabrication phase involves creating square and trapezoidal aluminium sandwich panels bonded using specialized aluminium glue. The results notably highlight the pivotal role of corrugated sandwich panel thickness in enhancing crashworthiness, displaying a direct correlation between thickness and responses. Particularly, two-core configurations exhibit superior performance in reducing IPCF during low-velocity loading compared to other panels. These structures showcase exceptional capability in diminishing IPCF rates during low-velocity loading, surpassing even foam-filled panels and demonstrating superior crashworthiness among the tested configurations.

Damage evolution of foam aluminum sandwich panel under three-point bending load by micro-CT

To investigate the effect of different thickness ratios of the upper and lower panels on the foam aluminum sandwich panels, this paper conducts three-point bending tests. And use micro-CT technology to perform phased scans of the bending process in the experiment. The results show that, the collapse, splitting, and lateral extrusion of each cell are simultaneously present in three different forms of damage. At a span of 100mm, cell collapse dominates the damage deformation. At spans of 80mm and 60mm, splitting becomes the dominant factor. When the intrusion depth of the loading roller significantly increases, lateral extrusion damage becomes dominant.

Statistical evaluation of three-point bending properties of sustainable aluminium sandwich panels with arched-core geometry

This study presents the first assessment of sustainable aluminium sandwich panels with an arched-core geometry. The arches are constructed from recycled aluminium obtained from drink container cans and bonded to aluminium skins using a polymer system. Through statistical analysis, the research aims to investigate the influence of the adhesive system (castor-oil or epoxy), adhesive layer thickness (0.8 mm or 1.5 mm), and core arch configuration (aligned or alternated pattern) on the mechanical performance of the sandwich panels, evaluated through a three-point bending test. The Al-arched-core panels, with a support span of 150 mm and a width of 75 mm, achieve a maximum load of 500 N, equivalent to 51 kg per 150 × 75 mm2. Additionally, the panels exhibit a core shear modulus of up to 10 MPa, while the flexural modulus under pure bending is estimated to be approximately 7 GPa. The mechanical performance of the panels is further enhanced by utilising thicker adhesive layers. Employing alternated arches in the core improves the distribution of flexural stress along the panel. These Al-arched-core panels demonstrate suitable mechanical performance for secondary structural applications, offering a cost-effective and environmentally friendly fabrication process.

Sound insulation performance of honeycomb core aluminum sandwich panels with flexible epoxy-based foam infill

The most distinctive features of sound insulation structures are their flexibility and porosity. Therefore, the flexible epoxy matrix material was made cellular using a suitable foaming agent. In addition, hollow glass microspheres (HGMs) were added to the epoxy matrix. Thus, the sound wave refraction was increased by obtaining cavities in the cell walls. Structures with different densities and voids were created by changing the ratios of the filling material and foaming agents used in the sandwich. An aluminum (Al) honeycomb was used to protect the insulation materials' structural integrity and ensure the homogeneous distribution of sound waves. The effect of density differences on sound insulation values was investigated. The mechanical properties of sandwich structures were determined using compression and three-point bending tests. The distribution of the filler in the matrix was visualized using SEM. TGA, DSC, thermal conductivity, dielectric, and flammability tests were also performed to determine their thermal, electrical, and flammability properties. During the formation of cells in the flexible epoxy, the HGMs were positioned in the cell wall by internal gas pressure. Low-density structures performed better at low frequencies, while high-density structures at high frequencies.

Sandwich Face Layer Debonding Detection and Size Estimation by Machine-Learning-Based Evaluation of Electromechanical Impedance Measurements

The present research proposes a two-step physics- and machine-learning(ML)-based electromechanical impedance (EMI) measurement data evaluation approach for sandwich face layer debonding detection and size estimation in structural health monitoring (SHM) applications. As a case example, a circular aluminum sandwich panel with idealized face layer debonding was used. Both the sensor and debonding were located at the center of the sandwich. Synthetic EMI spectra were generated by a finite-element(FE)-based parameter study, and were used for feature engineering and ML model training and development. Calibration of the real-world EMI measurement data was shown to overcome the FE model simplifications, enabling their evaluation by the found synthetic data-based features and models. The data preprocessing and ML models were validated by unseen real-world EMI measurement data collected in a laboratory environment. The best detection and size estimation performances were found for a One-Class Support Vector Machine and a K-Nearest Neighbor model, respectively, which clearly showed reliable identification of relevant debonding sizes. Furthermore, the approach was shown to be robust against unknown artificial disturbances, and outperformed a previous method for debonding size estimation. The data and code used in this study are provided in their entirety, to enhance comprehensibility, and to encourage future research.

Low velocity impact penetration response of foam core sandwich panels with face sheets

Foam aluminum sandwich panels have potential applications in many fields because of their excellent performance. This study aims to explore the low velocity penetration dynamic response of foam sandwich panels. Based on the experimental results, a three-stage penetration model is established. Based on the principle of energy conservation, minimum potential energy and accumulating damage theory, the load and displacement time history, energy absorption and initial failure mode of the sandwich panel during penetration are predicted theoretically. The theoretical prediction results are compared with the experimental results, showing that the predicted failure load and deformation are within 10% of the experimental data. This paper provides an analytical method for studying the deformation failure mode and energy absorption mechanism of metal foam sandwich panels, which is helpful to improve the efficiency of metal foam sandwich panels in design.

Development and characterization of self-healing microcapsules, and optimization of production parameters for microcapsule diameter and core content

PurposeThis study produced epoxy-filled urea-formaldehyde (UF) microcapsules (MCs) and T-403 amine MCs using the in situ technique. The Taguchi method was used to determine the effects of the control factors (temperature, stirring speed, core-shell ratio and surfactant concentration) affecting MCs’ core diameter and core content and optimizing their optimum levels with a single criterion. Optimum control factor levels, which simultaneously provide maximum core diameter and core content of MCs, were determined by the PROMETHEE-GAIA multi-criteria optimization method. In addition, the optimized MC yield was analyzed by thermal camera images and compression test.Design/methodology/approachMicrocracks in materials used for aerospace vehicles and automotive parts cause serious problems, so research on self-healing in materials science becomes critical. The damages caused by micro-cracks need to heal themselves quickly. The study has three aims: (1) production of self-healing MCs, mechanical and chemical characterization of produced MCs, (2) single-criteria and multi-criteria optimization of parameters providing maximum MC core diameter and core content, (3) investigation of self-healing property of produced MCs and evaluation. Firstly, MCs were produced to achieve these goals.FindingsThe optimized micro cures are buried in the epoxy matrix at different concentrations. Thermal camera images after damage indicate the presence of healing. An epoxy-amine MC consisting of a 10% by weight filled aluminum sandwich panel was prepared and subjected to a quasi-static compression test. It was determined that there is a strong bond between the UF shell and the epoxy resin.Originality/valueThe optimization of production factors has been realized to produce the most efficient MCs that heal using less expensive and more accessible methods.

Quasi-Static Three-Point Bending Behavior of Aluminum Foam Sandwich with CFRP Face-Sheets

Aluminum foam sandwich panels are excellent structure–function integrated materials. With high specific strength, cushioning energy absorption and sound absorption of aluminum foam material, they overcome the disadvantage of the low strength of single aluminum foam materials. In this paper, the response of aluminum sandwich panels comprising aluminum foam cores and carbon fiber reinforced plastic (CFRP) face-sheets was investigated under quasi-static three-point bending, and the effect of core thickness as well as core density on flexural loads and deformation modes was studied. The experimental results show that increasing the thickness and the density of the core materials can increase the flexural load and bending stiffness in the bending process. The aluminum foam sandwich panels mainly include the following deformation modes in the three-point bending process: indentation, core shear, face-sheet fracture and debonding.

Development of a Formability Prediction Model for Aluminium Sandwich Panels with Polymer Core.

In the present work, the compatibility relationship on the failure criteria between aluminium and polymer was established, and a mechanics-based model for a three-layered sandwich panel was developed based on the M-K model to predict its Forming Limit Diagram (FLD). A case study for a sandwich panel consisting of face layers from AA5754 aluminium alloy and a core layer from polyvinylidene difluoride (PVDF) was subsequently conducted, suggesting that the loading path of aluminium was linear and independent of the punch radius, while the risk for failure of PVDF increased with a decreasing radius and an increasing strain ratio. Therefore, the developed formability model would be conducive to the safety evaluation on the plastic forming and critical failure of composite sandwich panels.

Numerical analysis of bent aluminium sandwich panels with different tubular cores

Abstract Sandwich panels are frequently used in transportation, automotive, aerospace and marine sectors due to their high rigidity, strength and ability to absorb energy. In this study, finite element analyses investigated the bending behaviour of aluminium sandwich panels fixed at both ends with different geometrical tubular core structures. The sandwich panels consist of 6063-T5 Aluminium core and 7075-T6 Aluminium skin. The core structure used square, circle, triangle, honeycomb, vertical ellipse and horizontal ellipse tube geometries. The square tube-core sandwich panel has the highest specific load-carrying capacity (SLCC) among the different tube-core geometries. In the square tube-core sandwich panel, where the number of tubes varies, the seven-tube-core panel showed the highest SLCC.

Development of modelling design tool for harpoon for active space debris removal

The level of debris in Earth orbit presents an increasing risk. Active debris removal, involving capture and deorbit of larger items, has been identified as important in controlling future debris population growth. One concept for capturing debris is a harpoon, with low post-penetration residual velocity being a key design requirement. Aluminium sandwich panels are common structural components on typical spacecraft and consequently a probable target structure. An ideal harpooning event is characterised with complete penetration of the sandwich panel and low harpoon residual (post penetration) velocity. This paper presents development of a numerical modelling tool for a harpoon design for active orbital debris removal. The ability to predict the ballistic limit of an aluminium sandwich panel with a honeycomb core representative of a large satellite structural element being the primary requirement for the modelling tool. The modelling approach was validated against the experimental results from normal and oblique impact tests performed for ogive and flat nose projectiles over a velocity range between 50 m/s to 120 m/s. The modelling was based on explicit finite element method, using the commercial LS-DYNA code. An element failure criterion was used to approximate material damage and failure. Sensitivity studies were performed to investigate the influence of model key features on the projectile exit velocity. The features with the strongest influence were the face sheet material model and the projectile-panel friction model. The projectile exist velocities observed in the experiments were used to select the final parameters used. The use of an element deletion criterion that incorporated the influence of stress triaxiality improved the agreement for the plate deformation behaviour between the numerical and experimental results. For the ogive nose projectile, the exit velocity agreed well with the experiments for the range of impact velocities and angles considered. For the flat nose projectile, the model overestimated the exit velocity. In the case of the normal impact this was due to the model's inability to capture the honeycomb crushing ahead of the projectile.

Bending Performance of Aluminum Sandwich Panel with Polyurethane Foam Core

Although rigid foam core structures have gotten a lot of attention, there have only been a few researches on foam reinforced sandwich panels with aluminum alloy A6061 sheets as face-sheets. In this research, the sandwich concept was applied to develop lightweight panels for roofing system. Analysis on the influences of core thickness, density, and foam layer arrangement on energy absorption, bending strength and displacement of sandwich panel under the quasi-static three-point bending test were investigated. Sandwich panel core is made of closed-cell polyurethane foam with densities of 40 kg/m3, 60 kg/m3, and 80 kg/m3. The quasi-static three-point bending tests were conducted in accordance to ASTM C-393 Standard and the polyurethane foam cores are design accordingly to the guideline of National Institutes of Standards and Technology (NIST). Load–displacement curves and mechanical properties are shown using data from experimental works. Results demonstrate that increased in thickness of the sandwich panel, also increased the bending strength, energy absorption and displacement. Furthermore, the sandwich panel with 50 mm thickness and 60 kg/m3 density foam core has the maximum bending strength.

Surface and honeycomb core damage in adhesively bonded aluminum sandwich panels subjected to low-velocity impact

The effect of the adhesive geometry on the impact damage of adhesively bonded aluminum sandwich panels was studied experimentally and numerically. Both the physical testing and the finite element results show that the core damage depth is dependent on the adhesive fillet height and can be linearly correlated with the dent depth . The focus of the finite element simulation is on representing the adhesive fillet height and the constraint that it provides for the cell walls at the interface with the face-sheet. A hybrid method combining the numerical study and the Bayesian method was proposed to predict the range of core damage depths from the numerical simulations based on the variability of the adhesive fillets. The variation of the adhesive fillet height between different cell walls significantly influences the core damage depth and cannot be ignored when predicting the range of the core damage depth. The non-uniform distribution of the adhesive fillets causes the core damage depth to vary within a range of up to 20% of the core thickness for the panel configurations considered in this study.

High-impact resistant hybrid sandwich panel filled with shear thickening fluid

This study developed a hybrid aluminium sandwich panel (ASP) with aluminium/Kevlar fabric facings filled with a concentrated shear thickening fluid (STF) for high impact resistance. Local puncture failure mode was dominant in pristine ASP after low-velocity impact, whereas global energy absorption behaviour was achieved after the addition of Kevlar fabrics and STF. The impact resistance of hybrid ASPs was greatly enhanced with increased core thickness. Micro-CT analysis after impact revealed that the excellent impact resistance of the hybrid sandwich panels was attributed to the synergistic effect of STF’s high energy absorption, Kevlar fabrics’ increased in-plane stiffness after STF impregnation and confinement of aluminium cells on the STF fillings. The energy absorption mechanism after the addition of Kevlar fabrics and STF are discussed in detail.

Hybrid assessment of acoustic radiation damping combining in-situ mobility measurements and the boundary element method

A hybrid experimental-numerical approach is proposed for assessing acoustic radiation damping – a major energy dissipating mechanism in lightweight structures. The vibrational behavior is characterized by distributed mobility measurements using laser Doppler vibrometry allowing to realistically capture the mechanical behavior of the structure under test. The experimentally obtained matrix of mobilities are coupled to a boundary element model to evaluate the radiated sound power numerically. Thereby, acoustic measurements and associated low frequency limitations are avoided, which results in two salient features of the proposed hybrid approach: modeling of diffuse incident acoustic fields and consideration of acoustic short-circuiting induced by slits and gaps. These features contribute to an accurate and excitation-dependent estimation of acoustic radiation damping in the low frequency range. The proposed hybrid approach is applied to flat and C-shaped aluminum sandwich panels mounted onto a tub-shaped foundation. The results are compared to those obtained by a previously reported numerical method.

Mechanical response and strength characteristics of aluminum honeycomb sandwich panels for infrastructure engineering

The use of aluminium sandwich panels has been increased in a certain number of engineering applications from infrastructure systems and transportation to aircraft and naval engineering. Due to their structural efficiency these materials are ideal for applications where ratio of strength to weight is of crucial importance. In the current study the investigation of the strength characteristics of aluminium sandwich panels with aluminium honeycomb core and different types of skins is performed using both analytical models and experimental procedures. A series of strength tests such as tension, shear, three point bending and double cantilever beam were conducted on aluminium honeycomb-cored sandwich panel specimens with five different skins in order to examine the mode of failure and the mechanical behaviour of the structural elements. The experimental findings are compared to theoretical values while an attempt for the explanation of the mechanisms leading to failure such as buckling, delamination or debonding between core and skins is performed. The results occurring from the study are very useful for the enhancement of the mechanical behaviour of sandwich constructions, thus more intensive work must be carried out in order to understand the physical mechanisms leading to strength characteristics of sandwich panels.

Energy absorption characteristics of aluminum sandwich panels with Shear Thickening Fluid (STF) filled 3D fabric cores under dynamic loading conditions

In this study, the energy absorption characteristics of aluminum sandwich panels with Shear Thickening Fluid (STF) filled 3D fabric cores was investigated under various loading conditions. The sandwich panel with 5-ply STF-filled 3D fabric (2Al-5STF) showed the highest absorbed energy (3.53 J) in three-point bending test. The 2Al-5STF specimen also demonstrated more resistance under ballistic impact loading than the sandwich panel with 5-ply neat 3D fabric (2Al-5Neat) such that with less average penetration depth presented the highest ballistic resistance. The dynamic compression test showed the STF helped to improve the impact absorption and compressive performance of the sandwich panels. The average peak force applied to the 2Al-5STF sandwich panel (30.5 kN) was 24.5 and 54.6% less than the 2AL-5Neat and 4Al specimens, respectively, and this sandwich panel demonstrated the highest impact absorption (peak force reduction). However, the 2Al-3STF specimen demonstrated the highest peak force reduction per unit areal density, and the 2Al-5Neat specimen demonstrated better reversibility.

An insight into stress and strain analysis over on hexagonal aluminium sandwich honeycomb with various thickness glass fiber face sheets

Aluminium honeycomb sandwich panels have greater applications for constructions and Hexagonal aluminium design of satellites, missiles, aircraft, ships and also automobiles. To prevent failure of an important structure that subjected to stress, the aluminium honeycomb sandwich panels with face sheets act as protective mechanism. It is important to go for analysis study about stress and strain distribution on aluminium honeycomb with face sheets. In this investigation, it is focused on stress and strain distribution of sandwich structures, which were constructed of hexagonal aluminium core with glass fibre face sheets. The model of hexagonal aluminium sandwich panels with glass fibre face sheets will develop by using the Pro-E software. Further the stress and strain distribution for glass fibre face sheets with aluminium honeycomb will analyze by using ANSYS software. The ANSYS analysis carried out for the face sheets of 0.5 mm, 1 mm and 1.5 mm thicknesses with hexagonal aluminium honeycomb, which should be useful effectively for various applications.