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This study aims to maximize the post-harvest quality of Moutan Cortex and reduce energy consumption. Radio frequency vacuum (RFV) technology was used to dehydrate Moutan Cortex in this study to investigate the effects of different drying temperatures, plate spacing, and vacuum degree on the drying kinetics, physicochemical quality, and microstructure of Moutan Cortex. The results showed that RFV drying shortened the dehydration time of the Moutan Cortex by 10.71–28.57% and increased the drying rate by 15.79–54.39% compared to hot-air drying. The best color (∆E = 6.08 ± 0.28, BI = 26.97 ± 0.98) and relatively high retention of polysaccharides, total phenolics, total flavonoids, antioxidant properties, paeonol, gallic acid, paeoniflorin, and benzoylpaeoniflorin contents were observed in the dried products of Moutan Cortex at a drying temperature of 50 °C, spacing of 90 mm, and vacuum of 0.025 MPa. Analyzing the microstructure, it was found that RFV drying could effectively inhibit the shrinkage and collapse of the cellular structure, and a regular and loose honeycomb pore structure appeared inside the samples, which contributed to the rapid migration of the internal moisture. This study can provide a theoretical reference basis for the selection and application of industrialized processing methods of high-quality Moutan Cortex. [ABSTRACT FROM AUTHOR]

In order to obtain a lightweight, high-strength, and customizable cellular structure to meet the needs of modern production and life, the mechanical properties of four thickness gradient honeycomb structures were studied. In this paper, four types of honeycomb structure specimens with the same porosity and different Poisson's ratios were designed and manufactured by using SLA 3D-printing technology, including the honeycomb, square honeycomb, quasi-square honeycomb, and re-entrant honeycomb structures. Based on the plane compression mechanical properties and failure mode analysis of these specimens, the thickness gradient is applied to the honeycomb structure, and four structural forms of the thickness gradient honeycomb structure are formed. The experimental results show that the thickness gradient honeycomb structure exhibits better mechanical properties than the honeycomb structure with a uniform cellular wall thickness. In the studied thickness gradient honeycomb structure, the mechanical properties of the whole structure can be significantly improved by increasing the thickness of cell walls at the upper and lower ends of the structure. The wall thickness, arrangement order, shape, and Poisson's ratio of the cell all have a significant impact on the mechanical properties of the specimens. These results provide an effective basis for the design and application of cellular structures in the future. [ABSTRACT FROM AUTHOR]

Cellular infill structures such as honeycomb have been widely used in the field of light weighting. In recent years, the emergence of additive manufacturing technologies has provided a new solution to fabricate complicated cellular infill structures. This paper presents a continuous printing path planning method for gradient honeycomb structures. Given a 2D filling region represented by a polygon, a honeycomb graph that covers the filling area is trimmed to generate an infill pattern. Then an algorithm is proposed to transform the honeycomb filling pattern into an Eulerian graph, which can be traversed by a single-stroke printing path. For each honeycomb, double-spiral paths are used to generate gradient honeycomb structures with varying wall thicknesses. Later, the 2D honeycomb infills are generalized to 3D cases that are suitable for multi-axis printing. First, three mutually orthogonal vector fields that are embedded on the tetrahedral mesh of the printed part are generated by considering the support-free condition. Then the three vector fields are used to calculate three monotonically increasing scalar distance fields, which span a non-Euclidean space. Finally, the 2D honeycomb infills are generated in the non-Euclidean space with parallel sliced layers, which are then mapped back to the Euclidean space to obtain the real self-supporting 3D honeycomb infills. The proposed 2D/3D honeycomb infill structures generation algorithms have been verified by both simulation and experimental tests. [ABSTRACT FROM AUTHOR]

An ongoing growth of the available materials dedicated to additive manufacturing (AM) significantly extends the possibilities of their usage in many applications. A very good example is 20MnCr5 steel which is very popular in conventional manufacturing technologies and shows good processability in AM processes. This research takes into account the process parameter selection and torsional strength analysis of AM cellular structures. The conducted research revealed a significant tendency for between-layer cracking which is strictly dependent on the layered structure of the material. Additionally, the highest torsional strength was registered for specimens with a honeycomb structure. To determine the best-obtained properties, in the case of the samples with cellular structures, a torque-to-mass coefficient was introduced. It indicated the best properties of honeycomb structures, which have about 10% smaller torque-to-mass coefficient values than monolithic structures (PM samples). [ABSTRACT FROM AUTHOR]

In this paper, the vibroacoustic performance of the star-shaped honeycomb-core annular cellular structures is investigated. The results imply the superiority of these structures over the hexagonal honeycomb-core annular cellular structures, with constant mass and overall structure size, in terms of sound insulation relative to static bending compliance. The spectral element method (SEM) is employed to accurately evaluate natural frequencies and dynamic responses with a reduced number of elements within a wide frequency range. The sound transmission loss (STL) is used as a metric to define vibroacoustic performance. The in-plane effective shear modulus of star-shaped honeycombs is derived analytically to analyze the mechanical and vibroacoustic characteristics of the structures. A structural–acoustic optimization study of star-shaped honeycombs for the maximum sound transmission loss under constant mass and high static bending stiffness constraints is evaluated and presented for a specified target range. An increase of sound transmission loss by 490.23% for the considered target range in the optimized star-shaped honeycombs shows significant vibroacoustic performance. [ABSTRACT FROM AUTHOR]

A designer of metallic energy absorption structures using additively manufactured cellular materials must address the question of which of a multitude of cell shapes to select from, the majority of which are classified as either honeycomb, beam-lattice, or Triply Periodic Minimal Surface (TPMS) structures. Furthermore, there is more than one criterion that needs to be assessed to make this selection. In this work, six cellular structures (hexagonal honeycomb, auxetic and Voronoi lattice, and diamond, gyroid, and Schwarz-P TPMS) spanning all three types were studied under quasistatic compression and compared to each other in the context of the energy absorption metrics of most relevance to a designer. These shapes were also separately studied with tubes enclosing them. All of the structures were fabricated out of AlSi10Mg with the laser powder bed fusion (PBF-LB. or LPBF) process. Experimental results were assessed in the context of four criteria: the relationship between the specific energy absorption (SEA) and maximum transmitted stress, the undulation of the stress plateau, the densification efficiency, and the design tunability of the shapes tested—the latter two are proposed here for the first time. Failure mechanisms were studied in depth to relate them to the observed mechanical response. The results reveal that auxetic and Voronoi lattice structures have low SEA relative to maximum transmitted stresses, and low densification efficiencies, but are highly tunable. TPMS structures on the other hand, in particular the diamond and gyroid shapes, had the best overall performance, with the honeycomb structures between the two groups. Enclosing cellular structures in tubes increased peak stress while also increasing plateau stress undulations. [ABSTRACT FROM AUTHOR]

The low stiffness resulting from substantial core porosity within the re-entrant honeycomb sandwich panel can be addressed by introducing rib-reinforcements. To investigate its static and vibration characteristics, an energy-based 2D equivalent-homogenization model (2D-EHM) was derived through asymptotic analysis of the leading terms in the governing equations considering the energy-related characteristics. The accuracy of the constructed model for predicting the elastic bending performance of the sandwich panel was verified by comparing the results of a three-point bending experiment with 3D-printed specimens. Comparative analysis with a 3D FE model demonstrates that the 2D-EHM exhibits maximum errors of only 4.65% and 6.46%, respectively, in analyzing static deformation and natural frequency while improving computational efficiencies by up to 59- and 173-folds. Parameter analysis reveals that the performance of SP-RRH is minimally affected by the reinforcement-to-honeycomb wall thickness ratio. However, its performance is compromised when the honeycomb walls align in an equilateral triangle with the reinforcing walls. Comparing specific stiffness as well as static and vibration characteristics of sandwich panels with different core configurations (including traditional and diamond reinforced re-entrant honeycombs) shows that inclusion of rib reinforcements enhances deformation resistance and natural frequencies through increased specific stiffness. These findings provide valuable insights for optimizing design of re-entrant honeycomb sandwich panels. [Display omitted] • VAM-based 2D model of SP-RRH accurately validated against 3D-FEM results. • Equivalent stiffness obtained via asymptotic analysis of unit cell's energy functional. • The tailorability of the unit cell facilitates the customization of its properties. • Rib-reinforcing walls enhance deformation resistance of sandwich panels. • The performance of SP-RRH is influenced by equilateral triangular cellular structure. [ABSTRACT FROM AUTHOR]

Composite honeycomb sandwich plates have been widely used in aerospace, ships, construction bridges, machinery, stationery, and other industries. In order to improve the performance and configuration, taking the structural dynamic characteristics of periodic honeycomb plate as the research object, a structural optimization design method based on natural frequency and stiffness was proposed with the goal of weight reduction. The geometric parameters of the structure system were trained by the multiobjective optimization genetic algorithm (MOGA), and the Pareto optimal solution of variable combination was obtained. This paper presented a decoupling method for complex system optimization design based on dynamic performance from the perspective of basic unit, which could solve the coordination problem of vibration stability and weight reduction in periodic honeycomb plate structure optimization design. It has reference significance for the similar composite material frame base structure design. [ABSTRACT FROM AUTHOR]

In order to promote the development of honeycomb composite reinforcements, the mechanical properties and optimization methods of honeycomb beams are studied. A structural optimization design method is proposed based on natural frequency and stiffness and the lightest weight. According to the vibration frequencies and mechanical analysis, the equivalent density and equivalent stiffness of the section in the unit length are deduced, which is considered a typical example. The geometric parameters of the structure system are trained by multiobjective optimization minimax algorithm (MOMA), and the Pareto optimal solution of variable combination is obtained. The results show that optimized objects are significantly better than that previously. Therefore, the optimized scheduling algorithm has some reference value and prospects for practical application. [ABSTRACT FROM AUTHOR]

• An attractive structure with superior dynamic crushing performance was proposed. • Reliable numerical models were established to avoid severe element distortion. • Dynamic crushing response was illuminated in the full range of deformation process. • The effects of strain-rate sensitivity and impact velocity were evaluated in depth. To achieve excellent dynamic crushing performance, an attractive foam-filled periodic hybrid cellular (F-PHC) structure containing both hexagonal and re-entrant cells was designed and fabricated. Dynamic crushing experiments for foam-filled PHC structures were carried out using a direct impact Kolsky bar testing system. Reliable numerical simulations using both finite element method and smoothed particle hydrodynamics method were developed to analyze the dynamic crushing responses of F-PHC structures in the full range of deformation processes. Effects of inertia, strain-rate sensitivity, cell number, and impact velocity were evaluated. The results show that the dynamic plateau stresses of periodic hybrid cellular structures can be substantially enhanced by filling foams. The dynamic crushing response of F-PHC structure is very susceptible to impact velocity due to inertia effect. Compared with foam-filled hexagonal honeycomb and foam-filled re-entrant honeycomb structures, F-PHC structures exhibited superior dynamic crushing performances, including smoother and longer dynamic plateau stresses, more uniform deformation distributions, and much more stable deformation processes. Moreover, F-PHC structures exhibited much lower dynamic initial peak stresses at the rear face. This study provides a fascinating design idea and shines light on attractive F-PHC structures with a promising application prospect in the field of impact protection. [ABSTRACT FROM AUTHOR]

Auxetic lattice structures are known for their superior stiffness-to-density and strength-to-density ratios. Re-entrant hourglass exhibits an acceptable equivalent elastic modulus and remarkable energy absorption capacity among various auxetic configurations due to their flexibility and hinge deflecting during crushing loads. This study introduces a curved hourglass honeycomb which can be produced using 3D printing with pure or reinforced filaments incorporating continuous fibers. New closed-form formulations are analytically derived using an energy method by considering an extracted unit cell to predict the equivalent in-plane mechanical properties for the first time. The plateau stress of the proposed honeycomb is evaluated at the densification state of a unit cell using the energy conservation theory, equating external work with plastic energy dissipation. The accuracy of these extended relations is validated against experimental outcomes, demonstrating good agreement between analytical and experimental results. Additionally, robust linear and nonlinear finite element analyses are conducted to assess the accuracy of the obtained relations, including the equivalent stiffness and plateau stress for structures produced with reinforced filaments. The nonlinear finite element code employs appropriate subroutines to model plasticity/damage events. Based on the established analytical relations for stiffness and plateau stress, multi-objective optimization using Genetic Algorithm is applied to define optimum values for the Pareto front chart's objective functions of stiffness and plateau stress. The optimization process involves exploring the design space and defining the values of geometrical parameters to achieve the desired objectives. In conclusion, this study presents a novel approach to developing curved re-entrant honeycomb structures, with analytical formulations validated against experimental and numerical results. Optimization helps to identify optimal configurations concerning stiffness and plateau stress, offering potential applications in lightweight and high-strength materials design. According to the obtained results, for selection of the best value for curved strut angle which results in the optimum value of stiffness and plateau stress, a range between 10°-34° can be considered depending on the volume fraction of fibers. [ABSTRACT FROM AUTHOR]

The natural beesʼ honeycombs maintain long-term structural stability in harsh environments, employing a highly material-efficient approach. However, the reasons remain somewhat ambiguous. To clarify the stabilization mechanism and investigate quasi-static compression responses of double-layer ordered cellular structures, honeycomb, Tóth and single-layer cellular structures with a relative density (ρ r) of 25.84 % were fabricated using 3D printing technology. Then, quasi-static compression experiments in three directions were conducted. Further, a numerical study was conducted to uncover the stabilization mechanism and effect of ρ r on compressive behaviors. Results revealed that the stabilization mechanism was mainly attributed to bearing load priority of intermediate layer and its inhibition on formation of plastic hinges. A relative density of 5.17 % served as a transition point for deformation mode, beyond which honeycomb and Tóth structures exhibited stronger in-plane compressive strength at expense of less sacrificed out-of-plane compressive strength, below which they both exhibited more stable compressive curves compared to single-layer cellular structures, which were favorable for energy absorption. This study clarifies the stability mechanism of beesʼ honeycombs and addresses the lack on compression behaviors of double-layer ordered cellular structures. Moreover, it introduces two available bionic structures with controllable deformation modes to expand the application of single-layer cellular structures. [ABSTRACT FROM AUTHOR]

This article has been retracted by Hindawi following an investigation undertaken by the publisher [[1]]. We wish to credit our own Research Integrity and Research Publishing teams and anonymous and named external researchers and research integrity experts for contributing to this investigation. [Extracted from the article]

[Display omitted] • Ultrathin ZIF layers were fabricated on flexible hollow fibers. • Highly (2 2 2)-oriented ZIF-8 layer with honeycomb cellular structure was obtained. • Orientation originated from the difference in attachment energy of crystal planes. • Membrane with H 2 permeance of 75,711 GPU and H 2 /CO 2 selectivity of 21.2 at 150 °C. • Excellent membrane flexibility and thermal stability. Metal-organic framework (MOF) membranes demonstrate enormous potential for energy-efficient gas separations, while the construction of flexible and oriented MOF-based membranes remains a significant challenge. Herein, we prepared an ultrathin and highly (2 2 2)-oriented ZIF-8 layer with unique honeycomb cellular structures on porous aminated polyethersulfone (PES) hollow fibers (HF) via UV radiation-induced surface amino-grafting followed by a homogeneous fluidic processing method, and the reaction conditions including amino-grafting density, radiation power, flow rate, and reaction time et al. were systematically investigated and optimized. The orientation of reflection originated from the difference in attachment energy of crystal planes induced by the surface amino groups. The coherent (2 2 2)-oriented NH 2 -ZIF-8@HF membrane exhibited distinguished H 2 /CO 2 separation performance with a mixed-gas H 2 permeance of 75711 ± 610 GPU, among the highest values of previously reported hollow fiber supported ZIF membranes, and the H 2 /CO 2 selectivity of 21.2 ± 0.11 at 150 °C. Additionally, the NH 2 -ZIF-8@HF membrane displayed outstanding mechanical and thermal stability with negligible deterioration of gas separation performance after folding and unfolding at 180° for 20 times and several temperature-swing cycles. ZIF-7 and ZIF-67 composite membranes were also prepared with outstanding H 2 /CO 2 separation performance following the same strategy. The facile membrane fabrication method and exceptional separation performance make NH 2 -ZIF@HF membranes attractive for important industrial energy-efficient H 2 recovery from steam cracking and similar processes. [ABSTRACT FROM AUTHOR]

Cellular structures exhibit attractive mechanical properties like lightweight, high specific stiffness, and excellent energy absorption. Materials and structures design offers valuable enhancement of nature honeycombs. This work proposed a variable cross-section unit cell to improve compressive and energy absorption properties of the cellular structure constituting these unit cells. In the developed variable cross-section unit cell, the inclined cell walls of the traditional accordion honeycomb were flipped at an angle in the out-of-plane direction or swept along a cousin wave path. The Fused Deposition Modeling (FDM) technique was employed to prepare honeycomb specimens from polylactic acid (PLA). In-plane quasi-static compressive tests were carried out to investigate mechanical behavior and energy absorption of the designed honeycomb structures. The results indicate that the design of the variable cross-section in the width direction enhanced compressive strength and improved energy absorption capability. Based on the variable stiffness characteristic of PLA, isothermal compression experiments were conducted to investigate the temperature dependence of the compressive behavior. This work provides a demonstration for improving the mechanical performance and energy absorption of lightweight cellular structures. [ABSTRACT FROM AUTHOR]

Rapid increase in the operating speeds of aerospace/automobile vehicles has demanded for the design of light weight structures resisting high velocity impact loads. Cellular structures have shown significant potential for mitigating the effects of extreme loading. Due to its geometry, honeycomb structure is observed to possess the highest load carrying capacity as compared to other regular shapes. In this study, three different hybrid cellular structures, namely: design 2, design 3 and design 4, are designed and developed for impact applications, through a systematic study considering the hexagonal basic unit cell, and combining order and levels by mimicking bamboo-spiderweb structures. Parametric studies are performed and the proposed unit cell in design 4 is observed to demonstrate the best performance in terms of specific energy absorption and crush force efficiency. Analytical models are developed to estimate the energy absorption of unit cells in designs 2–4 during the impact. Numerical studies are performed considering the proposed unit cells to estimate the energy absorption characteristics. Results from analytical and numerical investigations are compared to notice a close agreement, with a maximum error of 9.97%. The resistance to local impact is tested by developing sandwich structures with cores developed from the proposed unit cells. Bullet impact studies are performed on the sandwich structures at three different identified locations with an impact velocity of 115 m/s. Design modifications are carried out by combining the multi-staging and strategically offsetting the unit cells in each core of a two core sandwich structure, such that it can withstand the impacts at arbitrary locations for bullet speeds up to 115 m/s. The proposed novel fourth order and third level hybrid unit cell in design 4 is found to efficiently resist the impact loads. Hence, it is recommended for applications involving energy absorption under extreme loads. [ABSTRACT FROM AUTHOR]

Inspired by heterogeneous structures observed in nature (graphene, insects' eyes, and beehives), we demonstrate that topological defects in hexagonal honeycombs can enhance strength and energy absorption capacity. These defects consist of pentagon-heptagon pairs (known as 5–7 defects). Experimental studies of additive manufactured specimens and computational studies are performed on honeycomb panels that are perfectly periodic or that contain defects in one of two arrangements: (i) clustered to form inclusions or (ii) aligned to form 5–7 domain boundaries. The focus is on the compressive response in out-of-plane, in-plane, and inclined orientations. The results show a 25–30% strength improvement when the 5–7 defects are arranged into aligned domain boundaries. The boundaries induce asymmetric deformation and hydrostatically reinforce the neighbouring hexagonal cells. Such effects can be attributed to differences in topological network adjacency. The results suggest that there remains a largely untapped design space involving heterogeneous cellular structures. [Display omitted] [ABSTRACT FROM AUTHOR]

• The mechanical properties and deformation behavior of cellular MGs with different cellular structures are investigated. • The structure-mechanical properties relationship for cellular MGs is established. • MGs with stochastic cellular structures exhibit much higher energy absorption capacity than those with microlattice structures. • The mechanical properties of cellular MGs can be tuned by adjusting their cellular structures. The mechanical properties of cellular metallic glasses (MGs) are governed by the shape of their cellular structures. We employ finite element method analysis to characterize the mechanical behavior under quasi-static compression of cellular MGs with the same porosity but different shape, including stochastic (disordered) structures with uniform or gradient porosity and periodic (ordered) microlattice structures such as honeycomb, chiral, and body-centered cubic structures. The results show that stochastic structures with graded porosities degrade the yield strength and Young's modulus compared to uniform cellular MGs. MGs with microlattice structures display much lower Young's modulus and yield strength than stochastic cellular MGs with uniform porosity. However, the chiral structure presents the largest Young's modulus of all cellular MG models investigated. Furthermore, MGs with stochastic cellular structures exhibit much higher energy absorption capacity than those with microlattice structures. It is found that the deformation behaviors of cellular MGs can be tuned by adjusting their cellular structures. The obtained structure-mechanical properties relationship can provide useful guidance for designing cellular MG-based composites for advanced multifunctional applications. [ABSTRACT FROM AUTHOR]

Cellular structures such as honeycombs are used to manage impact loads in many engineering applications, where often the impact load is oblique (non-axial). Although these structures have been extensively studied under axial impacts, a key question remains largely unaddressed: How may their axial and shear responses be independently tailored for oblique impacts? Here we test whether incorporating curvature in the form of axisymmetric shape changes in the cell walls of viscoelastic circular cell honeycombs enables independent control over their shear and compressive responses during oblique impacts. We developed detailed finite element models of the circular cell honeycombs made of the 3D printable viscoelastic material Agilus. Using a new rig, we validated the predictions of the finite element models under oblique impacts. We performed a full-factorial computational design-of-experiments, varying the cell shape from concave to convex with different amplitudes and impact velocities from 2.5 to 7.5 m/s in order to determine their effects on the shear and compressive responses of the honeycombs under oblique impacts. The finite element models demonstrate remarkable agreement with experimental oblique impacts for both concave and convex cells. Our full-factorial computational search shows that both convex and concave cells have similar compressive stresses. However, the post-buckling shear stress of the concave cells are up to 300% larger than the convex cells. In addition, increasing the impact velocity increases both compressive and shear stresses by 211% due to the viscoelastic nature of the material. Our results show that these new recoverable honeycombs provide a compelling control over their shear response under oblique impacts, which is nearly independent from their compressive response. These new honeycombs can be used to manage oblique impacts in a wide range of products, such as helmets, shoes and seats, where enabling an independent control over shear and compressive responses will open new design avenues. In addition, the proposed simple control mechanism, i.e. the curvature change, can be exploited in future to actively morph the honeycomb cells during use for real-time performance adjustment. [Display omitted] [ABSTRACT FROM AUTHOR]

This study proposed a new bio-inspired hierarchical circular honeycomb (BHCH), mimicking the hierarchical structures from wood. The mechanical properties and energy absorption characteristics of the proposed structures were investigated by means of quasi-static compression tests and finite element (FE) analysis. Subsequently, the influences of geometric parameters and material selections on the energy absorption capacity were investigated. The experimental results and parametric study indicated that the BHCH outperformed the conventional circular honeycomb (CH) in terms of energy absorption capacity. Specifically, the BHCH had a higher specific energy absorption (SEA) than the corresponding CH with the same wall thickness (i.e. 45.3%) and the same volume of honeycombs (i.e. 71.2%). Furthermore, the relative stiffness, relative strength, and relative energy absorption of the BHCH were significantly higher than other popular cellular structures. Finally, a theoretical model was developed to estimate the mean crushing stress (MCS) and interaction effect of the proposed structure, which further demonstrated its enhanced energy absorption mechanisms. A good correlation between the predicted values and the numerical results proved the reliability of the proposed analytical models. With its excellent performance, the proposed BHCH provided a promising solution for the enhanced energy absorption of the honeycomb structure used in a wide range of applications from structural components of defence structures to protection systems in vehicles. [ABSTRACT FROM AUTHOR]

Cellular structures are light weight structures with high specific, impact, flexural strength and stiffness. Hierarchical structures offer higher load-bearing capacity compared to their conventional counter parts. In this study, performance of enhanced hierarchical honeycomb core cellular structures under compression and impact loads is investigated. The hierarchy is proposed by varying the order and the level of the cells. Hierarchical patterns are developed by replacing the vertex cells of regular hexagonal honeycomb with circular cells. The local arrangement of the proposed hierarchical cellular structures is improved to withstand higher loads. The out-of-plane performance of honeycomb structure is enhanced by a hierarchical scheme. As a result, a novel hierarchical second order second level hexagon based hybrid cell has been developed. Furthermore, the influence of sandwiching the cellular structures between face sheets against impact loads is also studied using numerical simulations. In order to transfer the loads efficiently from the top and bottom ends to the mid walls of the unit cell, the structural angle β is introduced as the angle between the normal of the face-sheet and the axis of the unit cell. Such an arrangement is observed to enhance the load distribution in the cellular structures. [ABSTRACT FROM AUTHOR]

The heat accumulator designed for the purposes of this study consists of two chambers with metal foam structures and honeycomb segments casted by the means of investment casting from an Al Si alloy. The cellular metal castings, characterized by a relatively large coefficient of thermal conductivity, provide rapid transport of heat energy from the source to the heat storage materials (paraffin or zeolite). In order to simulate the conditions of solar heating, two outdoor halogen reflectors were used for the heating stage. Multiple long-term cycles of charging and discharging of this heat accumulator, with and without porous metallic inserts to improve the thermal conductivity and increase the heat transfer area, were conducted and subsequently analysed. The metal foams are suitable for enhancing heat transfer in a zeolite bed, whereas the durable honeycomb casting is preferable for phase change material. Additionally, the porous foam improves the conditions for transporting vapour during dehydration/hydration. The application of cast inserts in the zeolite chamber helped to decrease the temperature gradient to below 50 °C. The overall amount of energy stored in the hybrid TES unit equaled 7676.4 kJ (2.14 kWh). [ABSTRACT FROM AUTHOR]

Periodic cellular structures are widely used in structural protection due to their lightweight and excellent energy absorption characteristics, but the corresponding crashworthy design is still limited. Based on the framework of hybrid cellular automata (HCA), the optimal design of periodic cellular structure for crashworthiness is carried out. To guarantee the periodicity of cellular structure, elemental internal energy (EIE) is redistributed averagely as a periodic constraint. Then, by iteratively modifying the local EIE target, the cellular structure is optimized until the maximum energy absorption (EA) is obtained under the specific volume fraction constraint. Through several 2D and 3D numerical examples, this design method is proved to be efficient for the crashworthiness design of periodic cellular structures. Specifically, EA of the optimized cellular structures in this study can be improved by design comparing with solid structures and classical honeycombs. Effects of cellular number and volume gradient on crashworthiness are also discussed. [ABSTRACT FROM AUTHOR]