Sandwich Structure Research Articles

An Effective Approach to Get Aluminum Foam Sandwich with High and Stable Interfacial Properties.

The interfacial mechanical characteristics of sandwich structures are crucial in defining the comprehensive mechanical performance of the whole structure. Nevertheless, in practical applications, the interface often emerges as the weakest segment due to potential defects in the interface of porous metal sandwich plates (PMSP). This study aims to explore the regulatory mechanisms influencing the mechanical characteristics of nano-SiO2-reinforced aluminum foam sandwich structure (AFS) interfaces and to propose an effective strategy to achieve AFS interfaces with superior and stable mechanical properties. Results indicated that surface modification conditions and the amount of nano-SiO2 introduced are the primary process variables determining the strength of the AFS interface. The modified silane coupling agent was capable of enhancing its dispersion in the epoxy resin, thereby improving the interfacial strength of AFS. The most significant enhancement in interfacial strength occurred at a nano-SiO2 concentration of 0.4 wt %, although a marked reduction in interfacial strength was observed with further increases in the nano-SiO2 content. The overall strength and energy absorption capacity of AFS were enhanced by 14.65% and 405.43%, respectively, through the utilization of this enhancement method. More importantly, the AFS produced using this method demonstrated a stable performance and high repeatability.

Spectral heat flux redistribution upon interfacial transmission

In nonmetallic crystals, heat is transported by phonons of different frequencies, each contributing differently to the overall heat flux spectrum. In this study, we demonstrate a significant redistribution of heat flux among phonon frequencies when phonons transmit across the interface between dissimilar solids. This redistribution arises from the natural tendency of phononic heat to re-establish the bulk distribution characteristic of the material through which it propagates. Remarkably, while the heat flux spectra of dissimilar solids are typically distinct in their bulk forms, they can become nearly identical in superlattices or sandwich structures where the layer thicknesses are smaller than the phonon mean free paths. This phenomenon reflects that the redistribution of heat among phonon frequencies to the bulk distribution does not occur instantaneously at the interface, rather it develops over a distance on the order of phonon mean-free-paths.

All-Optical Modulation Photodetectors Based on the CdS/Graphene/Ge Sandwich Structures for Integrated Sensing-Computing.

In this manuscript, an all-optical modulation photodetector based on a CdS/graphene/Ge sandwich structure is designed. In the presence of the modulation (near-infrared) light, the Fermi level of the graphene channel shifts, allowing for the tuning of the visible light response speed as well as achieving a broad responsivity range from negative (-3376 A/W) to positive (3584 A/W) response. Based on this, logical operations are performed by adjusting the power of the modulation light superimposed with the signal light. This facilitates more covert, all-optical, high-speed encrypted communication. The ultrahigh tunability and nearly symmetric positive and negative photoconductivity of all-optical modulation photodetectors significantly enhance the computational capacity of neuromorphic hardware. The proposed device exhibits substantial advantages in applications requiring high fault tolerance for integrated sensing-computing （ISC） and high-resolution motion object recognition, providing insights for the development of next-generation high-bandwidth, low-power-consumption ISC devices.

Stiff, lightweight, and programmable architectured pyrolytic carbon lattices via modular assembling

Recent advances in additive manufacturing have enabled the creation of three-dimensional (3D) architectured pyrolytic carbon (PyC) structures with ultrahigh specific strength and energy absorption capabilities. However, their scalability is limited by reduced strength at larger sizes. Here we introduce a modular assembling approach to scale up PyC lattice structures while retaining strength. Three assembling mechanisms—adhesive, Lego-adhesive, and mechanical interlocking—are explored, demonstrating notably increased specific compressive strength and modulus as size increases, driven by energy release from assembly joint fractures. Practical application is demonstrated by using assembled PyC lattices as the core of an aerospace sandwich structure, significantly enhancing indentation resistance compared to conventional aramid paper honeycomb core. The method also enables versatile designs, including curved structures for space debris protection and bio-scaffold applications. This scalable approach offers a promising pathway for integrating PyC structures into large-scale engineering applications requiring superior mechanical properties and programmability in complicated shape design.

Investigation into high-speed impact response of composite sandwich structures

Sandwich structures composed of top and bottom face sheets and an inner core are commonly used for energy-absorbing applications, mainly because of their superior stiffness-to-weight ratio and crashworthiness. Despite extensive studies on the ballistic behavior of monolithic and composite materials, limited research has focused on hybrid sandwich structures combining lightweight and ductile materials like thermoplastic polyurethane (TPU) with high-strength aluminum. This study aimed to numerically establish the ballistic limit velocities and the penetrating and perforation resistances of composite sandwich structures to address this gap. The sandwich panels were manufactured from thermoplastic polyurethane (TPU) and aluminum (Al) 2024-T351 as core and face sheets/skins, respectively. The panels were subjected to an impact to investigate the effects of various thicknesses of their face skins and core on high-speed impact resistance. From the results obtained, it was evident that the numerical models simulated experiments with high accuracy. The impact and damage resistances of the composite sandwich structures increased with the thicknesses of their core and face sheets. The resistance of the structure increased by 19% by increasing the thickness of face sheets from 1.2 to 2.0 mm. Similarly, the resistance of the composites can be increased by 44% by increasing the core thickness from 20 to 50 mm. Therefore, it can be established that the impact resistance of the composite sandwich structures depended on the thicknesses of their core and skins. The investigated performances of the different composite sandwich structures should guide their choice for various industrial applications.

Computationally expensive constrained problems via surrogate-assisted dynamic population evolutionary optimization

This paper proposes a surrogate-assisted dynamic population optimization algorithm (SDPOA) for the purpose of solving computationally expensive constrained optimization problems, in which the population is dynamically updated based on the real-time iteration information to achieve targeted searches for solutions with different qualities. Specifically, the population is dynamically constructed by simultaneously considering the real-time feasibility, convergence, and diversity information of all the previously evaluated solutions. The evolution strategies adapted to dynamic populations are designed to arrange targeted search resources for individuals with different potentials. Specifically, for mutation, targeted base solution selection for the top 2 and other center points is designed for emphasizing the exploitation in promising regions; for selection, the search sources arranged on the best and other population individuals are adaptively adjusted with the iteration progresses; for constraint handling, the diversity of infeasible solutions is integrated into the original constraint-domination principle to avoid the locality of only using constraint violation to rank infeasible solutions. For accelerating the convergence, the sparse local search is designed based on update state of the current best solution in which two excellent but non adjacent individuals are used to provide valuable guidance information for local search. Therefore, SDPOA strikes a balance between feasibility, diversity, and convergence. Empirical studies demonstrate that the SDPOA achieves the best performance among all the compared state-of-the-art algorithms, and the SDPOA can obtain new structures with smaller compliance in the design of polyline-based core sandwich structures.

A SERS/colorimetric biosensor based on AuNSs@Ag core-shell Prussian blue nanozyme for non-interference and rapid detection of Staphylococcus aureus in milk.

AAuNSs@PB@Ag-Apt surface-enhanced Raman scattering (SERS) probehas been developedby embedding Prussian blue (PB) between Au core and Ag shell. The PB SERS probe illustrates strong SERS activity in the Raman silent region of 2070 cm-1, and has a zero background signal, ensuring high sensitivity for the detection ofStaphylococcus aureus(S. aureus).Moreover, the assemble SERS probe exhibits the catalytic function of peroxidase (POD), enabling the catalysis of 3,3',5,5'-tetramethylbenzidine (TMB) for colorimetric detection. Additionally, we prepared lectin-functionalized magnetic nanoparticles (F-MNPs-ConA) that demonstrate superior adsorption capabilities towards S. aureus, achieving an impressive adsorption valueof up to 98.62%. The F-MNPs-ConA/S. aureus/AuNSs@PB@Ag-Apt sandwich structure constructed by the above SERS probe and magnetic nanoparticles achieves highly sensitive detection of S. aureus. The detection range is 1 × 100 ~ 1 × 108 CFU·mL-1, and the detection limit (LOD) is 1 CFU·mL-1. Notably, this method can be integrated into smartphones, facilitating rapid and on-site detection of S. aureus. Compared withsimilar biosensors, this biosensor offers distinct advantages, including a wide detection range and a low detection limit. The reliability of the biosensor was confirmed by its application in milk, where the recovery ranged from 93.66 to 120.8%. The dual-mode SERS/colorimetric detection, non-interfering nature, magnetic enrichment, and reusability of the biosensor make it a promising tool for point-of-care testing (POCT).

Overcoming the Conductance versus Crossover Trade-off in State-of-the-Art Proton Exchange Fuel-Cell Membranes by Incorporating Atomically Thin Chemical Vapor Deposition Graphene.

Permeance-selectivity trade-offs are inherent to polymeric membranes. In fuel cells, thinner proton exchange membranes (PEMs) could enable higher proton conductance and increased power density with lower area-specific resistance (ASR), smaller ohmic losses, and lower ionomer cost. However, reducing thickness is accompanied by an increase in undesired species crossover harming performance and long-term efficiency. Here, we show that incorporating atomically thin monolayer graphene synthesized via scalable chemical vapor deposition (CVD) and tunable defect density into PEMs (Nafion, ∼5-25 μm thick) can allow for reduced H2 crossover (∼34-78% of Nafion of a similar thickness) while maintaining adequate areal proton conductance for applications (>4 S cm-2). In contrast to most prior work using >50 μm symmetric Nafion sandwich structures, we elucidate the interplay of graphene defect density and Nafion proton transport resistance on the performance of Nafion|graphene composite membranes and find high-quality low-defect density CVD graphene (G) supported on Nafion 211 (∼25 μm); i.e., N211|G has a high areal proton conductance (∼6.1 S cm-2) and the lowest H2 crossover (∼0.7 mA cm-2). Fully functional centimeter-scale N211|G fuel-cell membranes demonstrate performance comparable to that of state-of-the-art Nafion N211 at room temperature as well as standard operating conditions (∼80 °C, ∼150-250 kPa-abs) with H2/air (power density ∼0.57-0.63 W cm-2) and H2/O2 feed (power density ∼1.4-1.62 W cm-2) and markedly reduced H2 crossover (∼53-57%).

Direct laser writing of planar and stretchable supercapacitors based on a graphene oxide and manganese dioxide nanoparticle composite on a paper substrate

Paper-based supercapacitors (P-SCs) exhibit superior electrochemical performance owing to the flexibility and unique surface properties of paper substrates. Currently, most P-SCs adopt a sandwich structure that is limited by electrode fabrication methods. However, the development of planar paper-based devices is crucial to satisfy the tremendous demand for wearable electronics. Herein, based on the mechanism of interaction between the laser and material, we used direct laser writing (DLW) techniques to fabricate in-plane P-SCs based on graphene oxide (GO) and manganese dioxide (MnO2) composite-covered paper substrates. Owing to the in-plane device structure and pseudocapacitive MnO2, the acquired rGO-MnO2-based planar P-SCs possessed a much higher specific capacitance value (17.7 mF/cm2) than that based on sandwich-structured reduced GO (rGO) (1.71 mF/cm2). In addition, three in-series integrated devices can be easily achieved via the DLW fabrication method, which shows potential for practical applications such as powering a light emitting diode. In addition, by carefully designing the paper substrate structure, the paper-based device exhibited excellent stretching stability. A specific capacitance retention of 86.8% remained after 5000 stretch cycles. Therefore, this study provides valuable insights into the design and fabrication of wearable paper-based electronics.

Effect of curvature angle and structural configurations on dynamic performance of honeycomb sandwich structures

The aim of this study is to investigate the effects of curve angle and structural parameters on ballistic performance of honeycomb sandwich structures. In the study, high-velocity impact simulations were performed in LS DYNA finite element program to investigate the effects of honeycomb structural parameters, curve angle, residual velocity, specific energy absorption (SEA) and damage mechanism. Progressive damage analysis based on the combination of cohesive zone model (CZM) and bilinear traction-separation law was performed. The ballistic limit value increased by 41.9% when the facesheet thickness increased by two times. When the cell wall thickness increased by five times, the ballistic limit value increased by 13.3%. When the core height was two times increased, the ballistic limit velocity value increased by 2.076 times. Although the ballistic limit velocity value of the CFRP Facesheet and Aluminum (Al) core sandwich structure is 7.14% lower than the all Al specimen, the SEA value is 9.47% higher. When the curve angle increases from 0˚ to 180˚, the ballistic limit value decreases by 22.8%. In general, this study provides useful information about the design of ballistic structures, parameters affecting their performance and their effects.

Numerical Simulation of Compressive Testing of Sandwich Structures with Novel Triply Periodic Minimal Surface Cores.

Sandwich structures with triply periodic minimal surface (TPMS) cores have garnered research attention due to their potential to address challenges in lightweight solutions, high-strength designs, and energy absorption capabilities. This study focuses on performing finite element analyses (FEAs) on eight novel TPMS cores and one stochastic topology. It presents a method of analysis obtained through implicit modeling in Ansys simulations and examines whether the results obtained differ from a conventional method that uses a non-uniform rational B-spline (NURBS) approach. The study further presents a sensitivity analysis and a qualitative analysis of the meshes and four material models are evaluated to find the best candidate for polymeric parts created by additive manufacturing (AM) using a stereolithography (SLA) method. The FEA results from static and explicit simulations are compared with experimental data and while discrepancies are identified in some of the specimens, the failure mechanism of the proposed topologies can generally be estimated without the need for an empirical investigation. Results suggest that implicit modeling, while more computationally expensive, is as accurate as traditional methods. Additionally, insights into numerical simulations and optimal input parameters are provided to effectively validate structural designs for sandwich-type engineering applications.

Influence of Potting Radius on the Structural Performance and Failure Mechanism of Inserts in Sandwich Structures

In this study, the mechanical performance and failure modes of cold-potted inserts within sandwich structures were examined, focusing on the influence of the potting radius, while maintaining constant insert radius and specimen characteristics. In this research, destructive testing was used to evaluate the pull out, load-carrying capacity, and failure mechanisms of the inserts. The methods of stiffness degradation and acoustic emissions (AE) were employed for structural health monitoring to capture real-time data on failure progression, including core buckling, core rupture, and skin delamination. The results indicated that increasing the potting radius significantly altered the failure modes and critical failure load of the insert system. A critical potting radius was identified where maximum stiffness was achieved. Beyond this point, insert fracture became the dominant failure mode, with minimal damage to the surrounding core and CFRP skins. Larger potting radii also led to reduced displacement at failure, increased ultimate loads, and elevated stiffness, which were maintained until sudden structural failure. Through detailed isolation and observation of each failure event and with the use of AE data, precise identification of system damage in real time was allowed, offering insights into the progression and causes of failure.

Studies on Shielding and Activation Levels in a Concrete-Iron-Concrete Sandwich Structure Wall in the CMUH Proton Therapy Facility.

The shielding performance and activation susceptibility of a sandwich wall in the proton therapy facility of China Medical University Hospital were investigated in an integrated manner using FLUKA Monte Carlo simulations. The 2-m-thick partition wall between two adjoining treatment rooms had a three-layered structure, which comprised a 0.2-m-thick iron layer sandwiched between two layers of 0.9-m-thick concrete. In comparison with that of a concrete wall of the same thickness, the shielding performance of the concrete-iron-concrete wall was marginally better, further reducing the transmitted dose rate by approximately a factor of 2 against secondary neutrons generated through proton bombardment. This study also investigated radioactivity levels from long-lived radionuclides (3H, 22Na, 54Mn, 55Fe, 60Co, 134Cs, 152Eu, and 154Eu) that are primarily induced in concrete or iron by neutrons. The specific activities of 54Mn, 55Fe, and 60Co in the middle iron layer were considerably higher (by factors of 75, 25, and 5, respectively) than those in the neighboring concrete. However, as for clearance levels, the index value of the iron layer was lower than that of the neighboring concrete because of the presence of fewer types of long-lived radionuclides in iron. Under irradiation scenarios considered in this study, the residual activity levels of the sandwich wall do not exceed those of a full-concrete wall, and the indexes at various depths estimated at 5 years cooling following a 20-y operational period comply with clearance criteria.

Effect of Depth of Cut and Number of Layers on the Surface Roughness and Surface Homogeneity After Milling of Al/CFRP Stacks.

A multilayer structure is a type of construction consisting of outer layers and a core, which is mainly characterized by high strength and specific stiffness, as well as the ability to dampen vibration and sound. This structure combines the high strength of traditional materials (mainly metals) and composites. Currently, sandwich structures in any configurations (types of core) are one of the main directions of technology development and research. This paper evaluates the surface quality of II- and III-layer sandwich structures that are a combination of aluminum alloy and CFRP (Carbon Fiber-Reinforced Polymer) after the machining. The effect of depth of cut (ae) on the surface roughness of the II- and III-layer sandwich structures after the milling process was investigated. The surface homogeneity was also investigated. It was expressed by the IRa and IRz surface homogeneity indices formed from the Ra and Rz surface roughness parameters measured separately for each layer of the materials forming the sandwich structure. It was noted that the lowest surface roughness (Ra = 0.03 µm and Rz = 0.20 µm) was obtained after the milling of the II-layer sandwich structure using ae = 0.5 mm, while the highest was obtained for the III-layer structure and ae = 1.0 mm (Ra = 1.73 µm) and ae = 0.5 mm (Rz = 10.98 µm). The most homogeneous surfaces were observed after machining of the II-layer structure and using the depth of cut ae = 2.0 mm (IRa = 0.28 and IRz = 0.06), while the least homogeneous surfaces were obtained after milling of the III-layer structure and the depths of cut ae = 0.5 mm (IRa = 0.64) and ae = 2.0 mm (IRz = 0.78). The obtained results may be relevant to surface engineering and combining hybrid sandwich structures with other materials.

Multilayer Graphene Stacked with Silver Nanowire Networks for Transparent Conductor.

A mechanically robust flexible transparent conductor with high thermal and chemical stability was fabricated from welded silver nanowire networks (w-Ag-NWs) sandwiched between multilayer graphene (MLG) and polyimide (PI) films. By modifying the gas flow dynamics and surface chemistry of the Cu surface during graphene growth, a highly crystalline and uniform MLG film was obtained on the Cu foil, which was then directly coated on the Ag-NW networks to serve as a barrier material. It was found that the highly crystalline layers in the MLG film compensate for structural defects, thus forming a perfect barrier film to shield Ag NWs from oxidation and sulfurization. MLG/w-Ag-NW composites were then embedded into the surface of a transparent and colorless PI thin film by spin-coating. This allowed the MLG/w-Ag-NW/PI composite to retain its original structural integrity due to the intrinsic physical and chemical properties of PI, which also served effectively as a binder. In view of its unique sandwich structure and the chemical welding of the Ag NWs, the flexible substrate-cum-electrode had an average sheet resistance of ≈34 Ω/sq and a transmittance of ≈91% in the visible range, and also showed excellent stability against high-temperature annealing and sulfurization.

Boosting Impedance Matching by Depositing Gradiently Conductive Atomic Layers on Porous Polyimide for Lightweight, Flexible, Broadband, and Strong Microwave Absorption.

Gradient structures are effective for microwave absorbing but suffer from inadequate lightweight and poor flexibility, making them fall behind the comprehensive requirements of electromagnetic protection. Herein, we propose a hierarchical gradient structure by integration with porous and sandwich structures. Specifically, polyimide (PI) foams are used as a robust and flexible skeleton, in which the foam cell walls are sandwiched by Ti3C2Tx, ZnO, and ZrO2 atomic layers in sequence. Owing to the decreasing conductivity of Ti3C2Tx, ZnO, and ZrO2, they form gradient impedance matching layers on both sides of the PI foam cell walls, significantly enhancing the absorbing intensity for microwaves. In addition, the porous and sandwich structures can synergistically facilitate multiple reflections, increasing the number of interactions between microwave and foam cell walls. Therefore, the resulting lightweight ZrO2@ZnO@Ti3C2Tx@PI (ZrZnTP) composite foams reach a minimum reflection loss of -68.4 dB with an effective absorbing bandwidth covering the whole X band (8.2-12.4 GHz). The ZrZnTP also exhibits outstanding flexibility even at an extremely low temperature of -196 °C (i.e., liquid nitrogen). This work offers a general approach to realizing hierarchically integrated structures of gradient, porousness, and sandwich structures for lightweight, flexible, broadband, and strong microwave absorbing materials.

Electrochemical biosensor based on Novozym 435 enzymatic ring-opening polymerization for CEA detection

Carcinoembryonic antigen (CEA) is a broad-spectrum tumour marker, with its concentration levels serving as a crucial predictor of cancer diagnosis. In this study, we synthesized a polycaprolactone (PCL) macromolecular polymer via enzyme ring-opening polymerization (eROP). This polymer was then utilized as a signal amplification element in the “sandwich structure” electrochemical impedance biosensor designed for CEA detection. Initially, 3-mercaptopropionic acid (MPA) was self-assembled onto the electrode surface via a gold-sulfur bond. The carboxyl terminus of MPA was then activated using carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Subsequently, antibody 1 (Ab1) was immobilised on the electrode surface through the formation of an amide bond, serving as a recognition probe. To prevent non-specific binding, the remaining sites were blocked with Bovine Serum Albumin (BSA). Following the specific capture of CEA by Ab1, the unreacted amino group on the electrode surface was sealed using acrolein. Antibody-2 (Ab2) was then introduced to specifically recognize CEA, forming a classic antibody-antigen–antibody “sandwich structure.” Finally, a DMPA (2,2-dihydroxymethylpropionic acid)-PCL (Polycaprolactone) polymer was conjugated to the electrode surface as a signal amplification unit. The impedance signal strength was subsequently measured using Electrochemical Impedance Spectroscopy (EIS). Under optimal conditions, the biosensor demonstrated a wide linear range (1 pg mL−1 ∼ 100 ng mL−1) and a low detection limit of 0.38 pg mL−1. The sensor also exhibited high selectivity, stability and reproducibility when tested with clinical serum samples, highlighting its potential applications for early diagnosis and clinical monitoring.

Structure failure and strength evaluation of honeycomb-based sandwich composites under variable hydro-thermal-mechanical load

The high-strength and lightweight sandwich structures have broad application prospect in aerospace, wind turbine generator, traffic and civil engineering. The sandwich structures usually service with severe environment and complicated mechanical load, structure failure and strength prediction are crucial issues. Under time-varying and optional position hydro-thermal–mechanical loading, this paper systematically analyzes strength failure, buckling and delamination of a sandwich beam with carbon fiber-reinforced polymer face sheet and aluminum honeycomb core. Effects of elastic boundary conditions, hydrothermal stress, configuration of honeycomb cell and thickness of face sheet on failure pattern and critical failure loading are evaluated. The theoretical deformation model is verified by performing a bending experiment of cantilever beam. For the honeycomb core with small re-entrant angle and shot horizontal cell wall, the sandwich cantilever beam occurs strength failure of face sheet and delamination is happened in simply supported beam. With increase of re-entrant angle and cell wall length, buckling of horizontal cell wall becomes the primary failure pattern of sandwich beam. With thickness increase of face sheet, the failure pattern switches from face sheet’s strength failure to delamination. The critical load for delamination decreases to a volley value and then increases with thickness of face sheet.

Acetylene semi-hydrogenation catalyzed by Pd single atoms sandwiched in zeolitic imidazolate frameworks via hydrogen activation and spillover.

The semi-hydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry, and palladium-based metallic catalysts are currently employed. Unfortunately, a fairly high cost and uncontrollable over-hydrogenation impeded the application of Pd-based catalysts on a large scale. Herein, a sandwich structure single atom Pd catalyst, Z@Pd@Z, was prepared via impregnation exchange and epitaxial growth methods (Z stands for ZIF-8), in which Pd single atoms were stabilized by pyrrolic N in a zeolitic imidazolate framework (ZIF-8). Semi-hydrogenation of acetylene was performed and Z@Pd@Z achieved 100% acetylene conversion at 120 °C with an ethylene selectivity of more than 98.3% at an extra low Pd concentration. Z@Pd@Z exhibited a specific activity of 1872.69 mLC2H4 mgPd-1 h-1, surpassing most of the reported Pd-based catalysts. The existence of Pd single atoms coordinated by nitrogen (Pd-N4) was verified by XAS (synchrotron X-ray absorption spectroscopy), which provided active sites for H2 dissociation and the dissociated hydrogen quickly spilled over the surface of the outer ZIF layer to hydrogenate alkyne to ethene; besides, the catalytic activity could be controlled by adjusting the thickness of the outer ZIF layer. The confinement of the ZIF on Pd single-atom sites and the high energy barrier of ethylene hydrogenation were found to be responsible for the superior C2H2 semi-hydrogenation activity. This work opens up valuable insights into the design of ZIF-derived single-atom catalysts for efficient acetylene selective hydrogenation.

Multifunctional charging and thermal–mechanical performance of double-layer sandwich structure with PCM

Multifunctional charging and thermal–mechanical performance of double-layer sandwich structure with PCM