Articoli di riviste: "Structures composite sandwich architecturée"

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Proietti, Alice, Nicola Gallo, Denise Bellisario, Fabrizio Quadrini e Loredana Santo. "Damping Behavior of Hybrid Composite Structures by Aeronautical Technologies". Applied Sciences 12, n. 15 (8 agosto 2022): 7932. http://dx.doi.org/10.3390/app12157932.

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Hybrid composite laminates are manufactured by using technologies and raw materials of the aeronautic sector with the aim to improve the damping behavior of composite structures. Matrix hybridization was achieved by laminating carbon fiber reinforced (CFR) plies with elastomer interlayers. Up to 10 different composite sandwich architectures were investigated by changing the stacking sequence, the thickness of the elastomer layers, and the elastomer typology, whereas the total number of the CFR plies was fixed to six for all the hybrid composites. Square panels with the size of 300 × 300 mm2 were autoclave molded with vacuum bagging, and rectangular samples were extracted for static and dynamic tests. Dynamic mechanical analyses were performed to measure the storage modulus and loss factor of hybrid materials, which were compared with static and dynamic performances of the composite structures under bending. Repeated loading–unloading cycles and free oscillation tests allowed us to the energy loss per unit of volume, and the acceleration damping, respectively. Results show that softest elastomer interlayers lead to big loss of stiffness without any positive effect in the damping behavior, which worsens as well. By using soft elastomers, complex architectures do not provide any additional benefit in comparison with the traditional sandwich structure with soft core and hard skins.

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N, Ahobal, Lakshmi Pathi Jakkamputi, Sakthivel Gnanasekaran, Mohanraj Thangamuthu, Jegadeeshwaran Rakkiyannan e Yogesh Jayant Bhalerao. "Dynamic Behavior Modeling of Natural-Rubber/Polybutadiene-Rubber-Based Hybrid Magnetorheological Elastomer Sandwich Composite Structures". Polymers 15, n. 23 (30 novembre 2023): 4583. http://dx.doi.org/10.3390/polym15234583.

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This study investigates the dynamic characteristics of natural rubber (NR)/polybutadiene rubber (PBR)-based hybrid magnetorheological elastomer (MRE) sandwich composite beams through numerical simulations and finite element analysis, employing Reddy’s third-order shear deformation theory. Four distinct hybrid MRE sandwich configurations were examined. The validity of finite element simulations was confirmed by comparing them with results from magnetorheological (MR)-fluid-based composites. Further, parametric analysis explored the influence of magnetic field intensity, boundary conditions, ply orientation, and core thickness on beam vibration responses. The results reveal a notable 10.4% enhancement in natural frequencies in SC4-based beams under a 600 mT magnetic field with clamped–free boundary conditions, attributed to the increased PBR content in MR elastomer cores. However, higher magnetic field intensities result in slight frequency decrements due to filler particle agglomeration. Additionally, augmenting magnetic field intensity and magnetorheological content under clamped–free conditions improves the loss factor by from 66% to 136%, presenting promising prospects for advanced applications. This research contributes to a comprehensive understanding of dynamic behavior and performance enhancement in hybrid MRE sandwich composites, with significant implications for engineering applications. Furthermore, this investigation provides valuable insights into the intricate interplay between magnetic field effects, composite architecture, and vibration response.

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Mat Rejab, Mohd Ruzaimi, W. A. W. Hassan, Januar Parlaungan Siregar e Dandi Bachtiar. "Specific Properties of Novel Two-Dimensional Square Honeycomb Composite Structures". Applied Mechanics and Materials 695 (novembre 2014): 694–98. http://dx.doi.org/10.4028/www.scientific.net/amm.695.694.

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Hexagonal honeycomb cores have found extensive applications particularly in the aerospace and naval industries. In view of the recent interest in novel strong and lightweight core architectures, square honeycomb cores were manufactured and tested under uniform lateral compression. A slotting technique has been used to manufacture the square honeycomb cores based on three different materials; glass fibre-reinforced plastic (GFRP), carbon fibre-reinforced plastic (CFRP) and self-reinforced polypropylene (SRPP). As semi-rigid polyvinyl chloride (PVC) foam was placed in each of unit cells to further stiffen the core structure. The core then was bonded to two skins to form a sandwich structure. The compressive responses of the sandwich structures were measured as a function of relative density. In this paper, particular focus is placed on examining the compression strength and energy absorption characteristics of the square honeycombs with and without the additional foam core. Comparisons in terms of specific strength and specific energy absorption have shown that the CFRP core offers excellent properties. The presence of the foam core significantly increases the energy absorption capability of overall structure and the SRPP core could potentially be used as an alternative lightweight core material in recyclable sandwich structures.

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Cheng, Mai-Li, Shao-Heng Guo e Zhi-Peng Huo. "Numerical Simulation Study on Mechanical Bearing Behavior of Arch Steel–Concrete Composite Sandwich Roof". Buildings 14, n. 1 (13 gennaio 2024): 218. http://dx.doi.org/10.3390/buildings14010218.

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In order to study the mechanical bearing behavior of arched sandwich roof structures, a full combination and independent action mode of concrete sandwich composite panels was constructed using the finite element method, and an arched steel–concrete composite sandwich roof with a span of 18 m was subjected to a numerical simulation test under a full-span vertical uniformly distributed load, with the bearing characteristics of the arched sandwich roof discussed in depth. The results show that the cross-sections of l/16 and l/2 of the elliptical arch sandwich roof are weak sections, and the tensile cracking of concrete appears for the first time in the upper and lower wythes of the elliptical arch sandwich roof, the von Mises stress level of the lower wythe of the l/16 section is higher under the ultimate load, and the roof shows four-part form failure characteristics. With the expansion of the cracking range of the upper and lower concrete wythes of the steel–concrete composite sandwich arch roof, the load–displacement curve of the roof structure does not decrease significantly, and the bearing capacity of the structure is high and the vertical deformation is small. The steel–concrete composite segment at the end of the roof effectively strengthens the edge constraint of the roof and improves the integrity of the sandwich roof. The upper and lower concrete wythes of the sandwich roof show a fully combined action mode in the elastic working stage and, when the concrete cracks, it shows a partial combined action mode.

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Shahbazi, Sepideh, Nicholas Singer, Muslim Majeed, Miroslava Kavgic e Reza Foruzanmehr. "Cementitious Insulated Drywall Panels Reinforced with Kraft-Paper Honeycomb Structures". Buildings 12, n. 8 (17 agosto 2022): 1261. http://dx.doi.org/10.3390/buildings12081261.

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Standard building practices commonly use gypsum-based drywall panels on the interior wall and ceiling applications as a partition to protect the components of a wall assembly from moisture and fire to uphold the building code and ensure safety standards. Unfortunately, gypsum-based drywall panels have poor resistance to water and are susceptible to mold growth in humid climates. Furthermore, the accumulation of drywall in landfills can result in toxic leachate impacting the surrounding environment. A proposed solution to the pitfalls of gypsum-based drywall arises in its substitution with a new lightweight composite honeycomb sandwich panel. This study aimed to develop sandwich panels with improvements in flexural strength and thermal insulating properties through the combined use of cementitious binder mix and kraft-paper honeycomb structures. The proposed alternative is created by following standard practices outlined in ASTM C305 to create cement panels and experimenting with admixtures to improve the material performance in order to cater to a drywall panel application. The kraft-paper honeycomb structure is bonded to cured cementitious panels to create a composite “sandwich panel” assembly. The results indicate that the sample flexural strength performed well after 7 days and exhibited superior flexural strength at 28 days, while providing a substantial increase in R-value of 5.84 m2K/W when compared to gypsum-based panels, with an R-value of 5.41 m2K/W. In addition, the reinforced kraft-paper honeycomb with a thick core and addition of flax fibres to the cementitious boards possesses better thermal conductivity, with a reduction of 42%, a lower density, and a lower water vapour transmission in comparison to the thin kraft-paper honeycomb sandwich panel.

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Rupp, Peter, Peter Elsner e Kay A. Weidenmann. "Specific bending stiffness of in-mould-assembled hybrid sandwich structures with carbon fibre reinforced polymer face sheets and aluminium foam cores manufactured by a polyurethane-spraying process". Journal of Sandwich Structures & Materials 21, n. 8 (13 agosto 2017): 2779–800. http://dx.doi.org/10.1177/1099636217725250.

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In this paper, the bending stiffness-to-weight-ratio of novel hybrid sandwich structures is investigated. The build-up of the sandwich panels consisted of face sheets made from carbon fibre reinforced polymer, aluminium foam cores and an interface of foamed polyurethane. The sandwich panels were produced in a single step, infiltrating the face sheet fibres and connecting the face sheets to the core simultaneously. By means of mechanical characterization, specimens with several variations of face sheet architecture and thickness, core structure and interface properties were examined. Quasi-static four-point bending and flatwise compression tests of the sandwich composites were conducted, as well as tensile tests of the face sheets. The results of the tensile and compressive tests were integrated in analytical models, describing the sandwich stiffness depending on the load case and the face sheet volume fraction. The effective Young’s modulus of the composite, measured in the four-point bending test, correlates well to the modelled effective bending modulus calculated from the single components face sheet and core. The model underestimates the effective density of the bending specimens. It could be shown that this underestimation results from the polyurethane foam connecting the face sheets to the core, as the mass of this polyurethane is not included in the model.

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Tawil, Herman, Chee Ghuan Tan, Nor Hafizah Ramli Sulong, Fadzli Mohamed Nazri, Muhammad M. Sherif e Ahmed El-Shafie. "Mechanical and Thermal Properties of Composite Precast Concrete Sandwich Panels: A Review". Buildings 12, n. 9 (11 settembre 2022): 1429. http://dx.doi.org/10.3390/buildings12091429.

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Precast concrete sandwich panels (PCSPs) are utilized for the external cladding of structures (i.e., residential, and commercial) due to their high thermal efficiency and adequate composite action that resist applied loads. PCSPs are composed of an insulating layer with high thermal resistance that is mechanically connected to the concrete. In the recent decades, PCSPs have been a viable alternative for the fast deployment of structures due to the low fabrication and maintenance cost. Furthermore, the construction of light and thin concrete wythes that can transfer and resist shear loads has been achieved with the utilization of high-performance cementitious composites. As a result, engineers prefer PCSPs for building construction. PCSP design and use have been examined to guarantee that a building is energy efficient, has structural integrity, is sustainable, is comfortable, and is safe. Hence, this paper reviews the expanding knowledge regarding the current development of the mechanical and thermal properties of the PCSPs components; subsequently, future potential research directions are suggested.

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Huang, Zhenyu, Xiaolong Zhao, Yutao Guo e Xiangqian Liu. "Residual Flexural Performance of Double-Layer Steel–RLHDC Composite Panels after Impact". Buildings 13, n. 12 (23 novembre 2023): 2916. http://dx.doi.org/10.3390/buildings13122916.

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The mechanical behavior of steel–concrete–steel (SCS) sandwich composite structures under low- or high-velocity impact loading has garnered increasing attention from researchers in recent decades. However, to date, limited effort has been dedicated to studying the residual resistance of SCS sandwich composite structures following impact damage. In a previous investigation, the authors developed a rubberized lightweight high-ductility cement composite (RLHDC) for implementation in double-layer steel–RLHDC–steel composite panels and examined the dynamic response of these panels under impact. To further explore the residual performance of impact-damaged composite panels, the present study conducts flexural tests on nine such panels. The study quantifies and analyzes the effects of various connector types, connector spacing, number of concrete layers, rubber powder content, and number of impacts on the residual flexural resistance of the impact-damaged composite panels. Detailed analysis is conducted on the failure modes, load–displacement curves, strain curves, and load–slip curves of the impact-damaged specimens. The test results reveal that the impact-damaged composite panels experience flexural failure with bond slip under static load. The residual flexural performance is found to be sensitive to the number of concrete layers and number of impacts. Finite element (FE) simulations are performed using LS-DYNA to investigate the residual flexural behavior of the impact-damaged composite panels. The restart method is employed in the simulations to mimic the post-impact static loading scenario. The agreement between the FE results and the experimental findings validates the model and provides a straightforward and effective approach for studying the residual performance of composite structures. An expanded parameter analysis leveraging the calibrated FE model indicates that the steel plate’s thickness and strength predominantly influence the composite panel’s residual resistance, whereas the influence from concrete strength proves less consequential.

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Stanisavljević, Gorjana, Darinka Golubović Matić, Milorad Komnenović, Ivana Vasović Maksimović e Željko Flajs. "Numerical and Experimental Study on Loading Behavior of Facade Sandwich Panels". Buildings 13, n. 6 (18 giugno 2023): 1554. http://dx.doi.org/10.3390/buildings13061554.

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This paper focuses on the study of the strength of facade sandwich panels used in building construction. The paper describes the results of experimental and numerical research on the behavior of sandwich panels made of polyisocyanurate core (PIR) and their structural connections when exposed to tensile and compressive loads. In the initial phase of this study, laboratory tests were performed to determine the physical and mechanical characteristics of the material from which the sandwich panels are made. Laboratory tensile and compression tests were performed on small samples of sandwich facade panels. In order to verify the obtained results, they were compared with the numerical analysis performed in the ANSYS software. The numerical model was found to accurately predict the results of the laboratory tests, suggesting that the model can be used to predict the behavior of these panels under different loads in service. The study showed that the foam core sandwich panel exhibits excellent mechanical properties. The results indicate the suitability of foam-based composite structures in the construction industry for various applications, such as roof and wall structures. The findings of this study may help in the development of lightweight and durable construction materials for the industry.

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Li, Chang-Hui, Jia-Bao Yan e Hui-Ning Guan. "Finite element analysis on enhanced C-channel connectors in SCS sandwich composite structures". Structures 30 (aprile 2021): 818–37. http://dx.doi.org/10.1016/j.istruc.2021.01.050.

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Librescu, Liviu, Sang-Yong Oh e Jorg Hohe. "Implication of Nonclassical Effects on Dynamic Response of Sandwich Structures Exposed to Underwater and In-Air Explosions". Journal of Ship Research 51, n. 02 (1 giugno 2007): 83–93. http://dx.doi.org/10.5957/jsr.2007.51.2.83.

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A study devoted to the dynamic response of sandwich panels to underwater and in-air explosions is presented. The study is carried out in the context of a geometrically nonlinear model of sandwich structures featuring anisotropic laminated face sheets and a transversely compressible orthotropic core. The unsteady pressure generated by the explosion and acting on the face of the sandwich panel includes the effect of the pressure wave transmission through the core. Its implications on the structural time-histories as corresponding to the underwater and in-air explosions are put into evidence. The effects of the transverse core compressibility on dynamic response are highlighted. In this sense, one of its major implications is the possibility to capture interactively the global and local (wrinkling) dynamic response of the panel. It is shown that implementation of the structural tailoring technique in the face sheets can constitute an important mechanism for enhancing the dynamic load-carrying capacity of sandwich panels when exposed to blast pulses. Effects of the core, the composite architecture of face sheets, orthotropy of the material of the core, geometrical non-linearities, initial geometric imperfection, and the damping ratio are investigated, and their implications for the dynamic response are highlighted. The comprehensive structural model considered in conjunction with the time-dependent loads generated by the underwater and in-air explosions, and the results obtained in this context, are expected to contribute to a better understanding of the response behavior and to be instrumental toward a better design of these structures.

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Aparecida Diniz, Camila, Daniel Brighenti Bortoluzzi, João Luiz Junho Pereira, Sebastião Simões da Cunha Junior e Guilherme Ferreira Gomes. "On the influence of manufacturing parameters on buckling and modal properties of sandwich composite structures". Structures 46 (dicembre 2022): 664–80. http://dx.doi.org/10.1016/j.istruc.2022.10.059.

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Chipanga, Tendai, Ouassini Nemraoui e Fareed Ismail. "Damage Assessment of Low-Velocity Impacted Sandwich Composite Structures Using X-Ray Micro-Computed Tomography". Journal of Engineering 2024 (13 febbraio 2024): 1–13. http://dx.doi.org/10.1155/2024/6147948.

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Sandwich composite structures offer significant versatility in structural system design but are susceptible to low-velocity impact damage, impacting their structural robustness. This study focused on nondestructive testing, particularly using X-ray micro-computed tomography, to assess damage on these structures, comprised of thin glass fibre reinforced polymer face sheets and a polyvinyl chloride foam core, under low-velocity impacts. Impacts were induced by a constant mass of 5.61 kg, dropped from various heights, generating impact energies between 2 and 22 J. This resulted in varied damage levels, from indentations to full perforations. The X-ray micro-computed tomography technique was chosen for its ability to detect internal damage. However, the system’s efficacy in accurately assessing damage depends on numerous factors like focus-to-detector distance, focus-to-object distance, and spatial resolution of the detector, among others. The system yielded an approximated resolution range of 10–25 μm for a focal spot size of 4 μm and the resolution range of 11–26 μm for a spot size of 7 μm. To this end, the system was able to reveal damage inflicted across the specimen through captured and reconstructed images. The quality of the reconstructed images was validated using ImageJ2 software by comparing with the processed images. The median filter was found to deliver images that closely resembled the original ones, albeit with a slight reduction in quality. Damage types varied based on impact energies. Low-level impacts caused matrix cracking and delamination at the foam interface. Medium-level impacts led to intralaminar and interlaminar damage, fibre fractures, and significant damage to the foam core through shearing and crushing. High-level impacts resulted in near or full perforations, with more pronounced delamination at the bottom interface, and fibre fractures in the impact zone, displaying a distinctive diamond-like damage pattern. These findings can be instrumental in developing a predictive impact damage model.

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Esmaeili, Kamyar. "An Introduction to Lightweight Flexible Nonlinear Composite (LFNLC) and Elastic Composite, Reinforced Lightweight Concrete (ECRLC) as the Cementitious LFNLC". International Journal of Innovation in Engineering 3, n. 3 (28 settembre 2023): 28–47. http://dx.doi.org/10.59615/ijie.3.3.28.

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Here, a new class of high-performance composites, called “Lightweight Flexible Nonlinear Composites (LFNLC)”, has been briefly introduced. This class of composites has its own structural and functional characteristics. Nonlinear behavior in bending and porous or porous-like texture are instances of such characteristics. - Cementitious LFNLC is termed “Elastic Composite, Reinforced Lightweight Concrete (ECRLC)”. The ECRLC provides lightweight beams with substantial strain capability, resilience modulus and toughness in bending, resulting in a considerable increase in bearing capacity while weighing significantly less. The failure mode in low-height and ultra-lightweight beams made of the ECRLC is not compressive and brittle. - This lightweight, flexible composite is a non-monopolistic, versatile and comparatively low-price material. Likewise, the virtues such as resilience and flexibility, workability, lightness, durability, and high formability are important in architecture. - In general, lightweight and integrated construction has a key importance in earthquake resistance. Therefore, the ECRLC can be especially beneficial in earthquake-prone regions. - By taking advantage of the resilience and flexibility of this formable system, it can also be used to build non-brittle reinforced ultra-lightweight and insulation sandwich panels, safe and lightweight guards, and shock-resistant structures. In addition, they are utilizable in some infrastructures and explosion-proof pieces with suitable behavior, resilience, and toughness. - This work presents a practical method for converting a rigid solid into a flexible material with lower density or increasing the elasticity of a flexible material while decreasing the density. Essentially, this method entails creating a porous or porous-like texture in the material, reinforcing appropriately, and providing it with the necessary integrity. (For example, properly dispersing lightweight aggregates all over the reinforced, conjoined matrix can produce a porous-like texture.) By this process, the resilience modulus and toughness in bending rise and the density reduces. - This paper briefly discusses the functional and structural characteristics of LFNLCs, some applications, and a Reproducible example of the ECRLC.

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Drissi-Habti, Monssef, e Venkadesh Raman. "Fatigue Behavior of Smart Composites with Distributed Fiber Optic Sensors for Offshore Applications". Journal of Composites Science 6, n. 1 (22 dicembre 2021): 2. http://dx.doi.org/10.3390/jcs6010002.

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Continuous inspection of critical zones is essential to monitor the state of strain within offshore wind blades, thus, enabling appropriate actions to be taken when needed to avoid heavy maintenance. Wind-turbine blades contain various substructures made of composites, sandwich panel, and bond-joined parts that need reliable Structural Health Monitoring (SHM) techniques. Embedded, distributed Fiber-Optic Sensors (FOS) are one of the most promising techniques that are commonly used for large-scale smart composite structures. They are chosen as monitoring systems for their small size, being noise-free, and low electrical risk characteristics. In recent works, we have shown that embedded FOSs can be positioned linearly and/or in whatever position with the scope of providing pieces of information about actual strain in specific locations. However, linear positioning of distributed FOS fails to provide all strain parameters, whereas sinusoidal sensor positioning has been shown to overcome this issue. This method can provide multiparameter strains over the whole area when the sensor is embedded. Nevertheless, and beyond what a sensor can offer as valuable information, the fact remains that it is a “flaw” from the perspective of mechanics and materials. In this article and through some mechanical tests on smart composites, evidence was given that the presence of embedded FOS influences the mechanical behavior of smart composites, whether for quasi-static or fatigue tests, under 3-point bending. Some issues directly related to the fiber-architecture have to be solved.

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Leader, David P., e E. James Milner-White. "The β-link motif in protein architecture". Acta Crystallographica Section D Structural Biology 77, n. 8 (27 luglio 2021): 1040–49. http://dx.doi.org/10.1107/s2059798321006768.

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The β-link is a composite protein motif consisting of a G1β β-bulge and a type II β-turn, and is generally found at the end of two adjacent strands of antiparallel β-sheet. The 1,2-positions of the β-bulge are also the 3,4-positions of the β-turn, with the result that the N-terminal portion of the polypeptide chain is orientated at right angles to the β-sheet. Here, it is reported that the β-link is frequently found in certain protein folds of the SCOPe structural classification at specific locations where it connects a β-sheet to another area of a protein. It is found at locations where it connects one β-sheet to another in the β-sandwich and related structures, and in small (four-, five- or six-stranded) β-barrels, where it connects two β-strands through the polypeptide chain that crosses an open end of the barrel. It is not found in larger (eight-stranded or more) β-barrels that are straightforward β-meanders. In some cases it initiates a connection between a single β-sheet and an α-helix. The β-link also provides a framework for catalysis in serine proteases, where the catalytic serine is part of a conserved β-link, and in cysteine proteases, including Mpro of human SARS-CoV-2, in which two residues of the active site are located in a conserved β-link.

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Zhuang, Zhaoyi, Xuebin Yang, Kun Xie, Mengyan Tang, Yanbiao Xu e Xianye Ben. "The Mathematical Modeling and Performance of Sky Radiative Coolers". Buildings 13, n. 12 (28 novembre 2023): 2972. http://dx.doi.org/10.3390/buildings13122972.

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Sky radiative cooling is a kind of passive cooling technology that uses the “atmospheric window” to emit the object’s own heat to the low temperature of outer space; this technology has low energy consumption, no pollution, and other useful characteristics, so in recent years it has attracted widespread attention. The cooling effect of the sky radiative cooler is mainly affected by the constantly changing outdoor ambient temperature. In addition, the structure of the radiative cooler itself also means that its radiative cooling power undergoes obvious changes. Here, we utilized COMSOL simulation software to establish a numerical heat transfer model for radiative cooling, aimed at investigating the influencing factors on the sky radiative cooler and methods to enhance the structure of the radiative cooling. This study discusses outdoor ambient wind speed, the inlet flow rate of the cooler, installation angle of the cooler, and different cooler structures. Based on simulation results, it is observed that, for varying wind speeds, when the ambient radiation temperature is higher than the surface temperature of the cooler, a larger ambient wind speed leads to a poorer refrigeration effect. The maximum temperature difference in surface temperature at wind speeds of 0 m/s and 4 m/s is 0.59 °C. When the ambient temperature is lower than the surface temperature of the cooler, a smaller wind speed results in a greater net refrigeration power. The maximum temperature difference in this scenario is 0.32 °C. The net refrigeration power of the radiative cooler increases with an increase in water flow rate. As the water flow rate increases from 0 L/min to 5 L/min, the net refrigeration power increases from 25 W/m2 to 200 W/m2 and gradually stabilizes. Considering the radiative impact of the cooler on the surrounding environment, as the installation angle increases from 0° to 90°, the surface temperature of the cooler first increases and then decreases, reaching its highest temperature of 29.26 °C at 45°. The surface temperature of the cooler varies with the thickness of the air sandwich, increasing from 1 cm to 12 cm, and then decreasing. The lowest temperature of 23.4 °C is achieved at a thickness of 8 cm. The increase in the fin structure on the surface of the radiative cooler leads to a decrease in its refrigeration performance, and the difference between the inlet and outlet temperatures of the radiative cooler with a flat plate structure is always greater than that of the finned plate, and the difference in the average radiance is 23.52 W/m2. Finally, the energy-saving effect of the sky radiative cooling composite system is analyzed. Taking a typical small office building as an example, an energy consumption analysis model is set up, and the energy consumption of the composite system is simulated in four cities with different climates, using EnergyPlus software (version 8.6); the system’s power consumption is the largest in hot and humid climates. Compared with the traditional vapor-compression refrigeration system, the composite system reduces air conditioning power consumption by 25.7%, 32.5%, 37.1%, and 44.8% in Guangzhou, Shanghai, Jinan, and Shenyang, respectively. The main innovations of this paper include analyzing and studying the influence of the tilt angle change of the radiative plate on the refrigeration performance of the cooler and the relationship between the surrounding buildings, adding air sandwiches and ribs to the radiative cooler to analyze the influence of convective heat transfer on the refrigeration effect, which plays a guiding role in the design and research of the sky radiative cooler.

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ERYILDIZ, Meltem. "Estimation of three-point bending behavior using finite element method for 3D-printed polymeric sandwich structures with honeycomb and reentrant core". European Mechanical Science 6, n. 3 (20 settembre 2022): 196–200. http://dx.doi.org/10.26701/ems.1101832.

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Sandwich structures are known as ultra-light porous materials. Because the structure has advantages in terms of acoustics, fatigue, and impact resistance that conventional stiffened plates cannot match, it has become a popular material in aerospace, automotive, marine, windmill, and architectural applications. One promising method for decreasing production waste and enhancing flexural stress is to employ Additive Manufacture (AM) technologies for sandwich structure manufacturing. In this study, polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyethylene terephthalate glycol (PETG) sandwich structures with reentrant and honeycomb cores were designed and then a finite element analysis (FEA) was carried out to compare the stress distributions in these sandwich composites. According to the findings, higher flexure stresses and specific energy absorption were obtained in the reentrant sandwich structures compared to honeycomb sandwich structures. A minimum equivalent stress value was found in the ABS material, while a maximum equivalent stress value was found in the PLA material.

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Williams, H. R., R. S. Trask e I. P. Bond. "Self-healing composite sandwich structures". Smart Materials and Structures 16, n. 4 (29 giugno 2007): 1198–207. http://dx.doi.org/10.1088/0964-1726/16/4/031.

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Fergusson, Alexander D., Amit Puri, Andrew Morris e John P. Dear. "Flexural Testing of Composite Sandwich Structures with Digital Speckle Photogrammetry". Applied Mechanics and Materials 5-6 (ottobre 2006): 135–44. http://dx.doi.org/10.4028/www.scientific.net/amm.5-6.135.

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Composite sandwich structures are finding increasingly widespread use in fields ranging from aerospace and wind turbines to sports applications such as skis and surfboards. The high specific stiffness that composite sandwich structures can provide lends them well to these applications. However, the operational environment of these structures is frequently aggressive and often results in damage during service. The extent and effect of damage incurred is an important factor in the design and maintenance of composite sandwich structures. Failure of an individual component can be catastrophic for the rest of the structure. The purpose of this investigation was, firstly, to ascertain whether DSP was a viable technique for determining strain fields within composite sandwich structures. Secondly, to determine whether four point flexure would give rise to pure flexure between the central rollers, and if not, to understand what load conditions were present. This investigation was also carried out with a view to extend the investigation into the effect of defects on composite sandwich structures manufactured by RIFT. The grounds for selection of composite sandwich structures normally lie in their flexural performance. Reliable and accurate quantitative testing methods for evaluating the flexural performance of sandwich panels are needed if composite sandwich structures are to be used safely and effectively. In addition, methods to determine the effect of damage and defects on flexural behaviour of sandwich structures is particularly important for designing the repair and maintenance regimes of composite sandwich components.

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Birman, Victor. "Thermomechanical Wrinkling in Composite Sandwich Structures". AIAA Journal 42, n. 7 (luglio 2004): 1474–79. http://dx.doi.org/10.2514/1.5913.

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Grünewald, Jonas, Patricia Parlevliet e Volker Altstädt. "Manufacturing of thermoplastic composite sandwich structures". Journal of Thermoplastic Composite Materials 30, n. 4 (5 agosto 2016): 437–64. http://dx.doi.org/10.1177/0892705715604681.

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Composite sandwich structures show promising lightweight properties for the aviation industry. Nowadays time-consuming manufacturing methods still prevent an extensive application of composite sandwiches, which can be overcome by the use of thermoplastic polymers in skins and core. During manufacturing of thermoplastic composite (TPC) sandwich structures, the joining of skins and core is a critical step. Therefore, several skin–core joining methods have been under investigation and development in the published literature, which can be categorized into adhesive bonding or fusion bonding. Fusion bonding by means of vacuum moulding, compression moulding or in situ foaming shows great potential for joining sandwich skins and core. Although various phenomena such as core collapsing or skin deconsolidation challenge the processes. This article aims to present an overview of research that has been done in the area of manufacturing TPC sandwich structures and will serve as a baseline and aid for further research and development efforts.

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Tarlochan, F., A. M. S. Hamouda, E. Mahdi e B. B. Sahari. "Composite sandwich structures for crashworthiness applications". Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 221, n. 2 (aprile 2007): 121–30. http://dx.doi.org/10.1243/14644207jmda112.

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24

Dear, John P., Emily Rolfe, Mark Kelly, Hari Arora e Paul A. Hooper. "Blast Performance of Composite Sandwich Structures". Procedia Engineering 173 (2017): 471–78. http://dx.doi.org/10.1016/j.proeng.2016.12.065.

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25

Potluri, P., E. Kusak e T. Y. Reddy. "Novel stitch-bonded sandwich composite structures". Composite Structures 59, n. 2 (febbraio 2003): 251–59. http://dx.doi.org/10.1016/s0263-8223(02)00087-9.

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Katzman, Howard A., Robert M. Castaneda e Han Sik Lee. "Moisture diffusion in composite sandwich structures". Composites Part A: Applied Science and Manufacturing 39, n. 5 (maggio 2008): 887–92. http://dx.doi.org/10.1016/j.compositesa.2008.01.005.

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Krot, Kamil, Edward Chlebus e Bogumiła Kuźnicka. "Laser cutting of composite sandwich structures". Archives of Civil and Mechanical Engineering 17, n. 3 (maggio 2017): 545–54. http://dx.doi.org/10.1016/j.acme.2016.12.007.

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28

Sierakowski, R. L., e M. L. Hughes. "Force protection using composite sandwich structures". Composites Science and Technology 66, n. 14 (novembre 2006): 2500–2505. http://dx.doi.org/10.1016/j.compscitech.2006.03.034.

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29

Khoran, M., P. Ghabezi, M. Frahani e M. K. Besharati. "Investigation of drilling composite sandwich structures". International Journal of Advanced Manufacturing Technology 76, n. 9-12 (30 settembre 2014): 1927–36. http://dx.doi.org/10.1007/s00170-014-6427-x.

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30

Gdoutos, E. E., I. M. Daniel e K. A. Wang. "Indentation failure in composite sandwich structures". Experimental Mechanics 42, n. 4 (dicembre 2002): 426–31. http://dx.doi.org/10.1007/bf02412148.

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31

Tian, Ce, Zhimin Tian, Xinwei Cao e Shangwei Dong. "Lightweight design of composite sandwich corrugated structures based on variable density method". Journal of Physics: Conference Series 2808, n. 1 (1 luglio 2024): 012076. http://dx.doi.org/10.1088/1742-6596/2808/1/012076.

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Abstract For the lightweight design of composite sandwich corrugated structures, a new topology optimization design scheme is proposed using the variable density method. Multi-working conditions static analysis of the composite sandwich corrugated structure is carried out by finite element software. Then, the topology optimization is carried out by using the minimum flexibility method. Finally, the results of different working conditions are coupled to propose a new composite sandwich corrugated structure. The results indicate that the structure has a weight reduction of 34% and exhibits periodicity and continuity while also meeting the necessary mechanical properties to fulfill the engineering requirements. The optimization of composite sandwich corrugated structures has been achieved, providing a new approach to the lightweight design of composite sandwich structures.

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32

Zhou, Hao, Rui Guo, Rongzhong Liu e Wei Jiang. "Dynamic response of composite sandwich structures with the honeycomb-foam hybrid core subjected to underwater shock waves: Numerical simulations". Journal of Composite Materials 56, n. 6 (31 gennaio 2022): 911–28. http://dx.doi.org/10.1177/00219983211066386.

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The dynamic response of composite sandwich structures with honeycomb-foam hybrid cores subjected to underwater shock waves was investigated by numerical simulations. The deformation process, core compression, momentum transmitting characteristics, and energy absorbing properties of sandwich structures subjected to underwater shock waves with different initial pressures were analyzed. The dynamic responses of the composite sandwich with different core configurations were also compared. The results show that the composite sandwich structures can provide superior protection from underwater shock waves than mass equal laminate plates and the sandwich structures with hybrid cores have better performance than that with empty honeycomb cores when subjected to underwater shock waves. The research can provide reference for the lightweight design and optimization of protective structures against underwater blast loading.

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33

Cvitkovich, Michael K., e Wade C. Jackson. "Compressive Failure Mechanisms in Composite Sandwich Structures". Journal of the American Helicopter Society 44, n. 4 (1999): 260. http://dx.doi.org/10.4050/jahs.44.260.

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34

Al-Khazraji, Mustafa, Sadeq Bakhy e Muhsin Jweeg. "Modal Analysis of Specific Composite Sandwich Structures". Engineering and Technology Journal 41, n. 1 (15 settembre 2022): 13–22. http://dx.doi.org/10.30684/etj.2022.133585.1195.

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35

Daniel, Isaac M., Emmanuel E. Gdoutos, Jandro L. Abot e Kuang-An Wang. "Deformation and Failure of Composite Sandwich Structures". Journal of Thermoplastic Composite Materials 16, n. 4 (luglio 2003): 345–64. http://dx.doi.org/10.1177/0892705703016004005.

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Williams, Richard R., William E. Howard e Scott M. Martin. "Composite sandwich structures with rapid prototyped cores". Rapid Prototyping Journal 17, n. 2 (8 marzo 2011): 92–97. http://dx.doi.org/10.1108/13552541111113835.

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37

Johnson, WS, JE Masters, C. Kassapoglou, SC Fantle e JC Chou. "Wrinkling of Composite Sandwich Structures Under Compression". Journal of Composites Technology and Research 17, n. 4 (1995): 308. http://dx.doi.org/10.1520/ctr10451j.

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38

Gdoutos, E. E., I. M. Daniel e K. A. Wang. "Compression facing wrinkling of composite sandwich structures". Mechanics of Materials 35, n. 3-6 (marzo 2003): 511–22. http://dx.doi.org/10.1016/s0167-6636(02)00267-3.

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Kishore, S., P. Naik Parrikar, N. DeNardo e A. Shukla. "Underwater Dynamic Collapse of Sandwich Composite Structures". Experimental Mechanics 59, n. 5 (28 gennaio 2019): 583–98. http://dx.doi.org/10.1007/s11340-019-00470-x.

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Naik, N. K., G. Nageswara Rao, Ullas Agarwal, K. A. Raju, Shrinivas A. Pottigar e V. Suresh. "Sandwich structures with composite inserts: Experimental studies". Polymer Composites 30, n. 5 (maggio 2009): 639–48. http://dx.doi.org/10.1002/pc.20600.

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Gresham, J., W. Cantwell, M. J. Cardew-Hall, P. Compston e S. Kalyanasundaram. "Drawing behaviour of metal–composite sandwich structures". Composite Structures 75, n. 1-4 (settembre 2006): 305–12. http://dx.doi.org/10.1016/j.compstruct.2006.04.010.

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Sahu, Santosh Kumar, P. S. Rama Sreekanth e S. V. Kota Reddy. "A Brief Review on Advanced Sandwich Structures with Customized Design Core and Composite Face Sheet". Polymers 14, n. 20 (11 ottobre 2022): 4267. http://dx.doi.org/10.3390/polym14204267.

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Sandwich structures are a class of multifunctional high-performance structural composites that have the advantages of being lightweight, of a high strength-to-weight ratio, and of high specific energy absorption capabilities. The creative design of the core along with the apposite material selection for the fabrication of the face sheet and core are the two prerequisites with encouraging areas for further expedition towards the fabrication of advanced composite sandwich structures. The current review work focused on different types of core designs, such as truss, foam, corrugated, honeycomb, derivative, hybrid, hollow, hierarchical, gradient, folded, and smart core along with different composite materials accessible for face sheet fabrication, including fiber-reinforced composite, metal matrix composite, and polymer matrix composite are considered. The joining method plays a major role for the performance evolution of sandwich structures, which were also investigated. Further discussions are aligned to address major challenges in the fabrication of sandwich structures and further enlighten the future direction of the advanced composite sandwich structure. Finally, the work is summarized with a brief conclusion. This review article provides wider guidelines for researchers in designing and manufacturing next-generation lightweight multilayer core sandwich structures.

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Suciu, Mihaela. "About Buckling Bio-Composite Sandwich Bars". Applied Mechanics and Materials 245 (dicembre 2012): 39–44. http://dx.doi.org/10.4028/www.scientific.net/amm.245.39.

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Abstract. The bio-composites materials are very important for a lot of industry and life domains, particularly in the aeronautic industries and medicine, in orthopedics. Titanium and its alloys are most widely used, due to their mechanical properties similar to bone tissue. The sandwich structures are very light, they have a high stiffness in flexion and very good thermal characteristics. For the compressed sandwich structures, risks of buckling are higher than the conventional compressed structures, limited by a critical value of the applied force, then the deformations grow in importance and uncontrolled manner. We try to calculate the critical buckling force by the method presented in [2].

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Zaharia, Sebastian Marian, Mihai Alin Pop, Lucia-Antoneta Chicos, George Razvan Buican, Camil Lancea, Ionut Stelian Pascariu e Valentin-Marian Stamate. "Compression and Bending Properties of Short Carbon Fiber Reinforced Polymers Sandwich Structures Produced via Fused Filament Fabrication Process". Polymers 14, n. 14 (19 luglio 2022): 2923. http://dx.doi.org/10.3390/polym14142923.

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Additive manufacturing, through the process of thermoplastic extrusion of filament, allows the manufacture of complex composite sandwich structures in a short time with low costs. This paper presents the design and fabrication by Fused Filament Fabrication (FFF) of composite sandwich structures with short fibers, having three core types C, Z, and H, followed by mechanical performance testing of the structures for compression and bending in three points. Flatwise compression tests and three-point bending have clearly indicated the superior performance of H-core sandwich structures due to dense core structures. The main modes of failure of composite sandwich structures were analyzed microscopically, highlighting core shear buckling in compression tests and face indentation in three-point bending tests. The strength–mass ratio allowed the identification of the structures with the best performances considering the desire to reduce the mass, so: the H-core sandwich structures showed the best results in compression tests and the C-core sandwich structures in three-point bending tests. The feasibility of the FFF process and the three-point bending test of composite wing sections, which will be used on an unmanned aircraft, have also been demonstrated. The finite element analysis showed the distribution of equivalent stresses and reaction forces for the composite wing sections tested for bending, proving to validate the experimental results.

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Beznea, Elena Felicia, Ionel Chirica, Nicusor Baroiu e Virgil Teodor. "Parametric Study of Experimental and Numerical Simulation of Sandwich Composite Structures Flexural Behaviour". Materiale Plastice 54, n. 4 (30 dicembre 2017): 682–88. http://dx.doi.org/10.37358/mp.17.4.4925.

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Sandwich panels with composite/steel skin sheets and foam core are very often used as lightweight structures in automotive, maritime and aerospace applications due to their performances like high bending stiffness and strength and also lightweight. As an alternative to classical structural reinforced panels, the sandwich structures are justifying their use in various industrial fields, making these structures less complex, by eliminating the need for secondary stiffening. In the paper are presented three models of sandwich, steel-foam-steel, composite-foam-composite or steel-foam-composite structures, of different thicknesses, with functional use in various fields depending on necessities. The mechanical characteristics of the materials used in their manufacture have been determined. The panels have been subjected to various load cases in order to determine an optimal combination of weight and strength. At the same time, the numerical models used in the finite element analysis of the sandwich structures with specific elements for layered composites or sandwich (SHELL 4L and SOLID L) are presented.

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Yartsev, Boris, Viktor Ryabov e Lyudmila Parshina. "Dissipative properties of composite structures. 1. Statement of problem". Transactions of the Krylov State Research Centre 4, n. 398 (15 novembre 2021): 24–34. http://dx.doi.org/10.24937/2542-2324-2021-4-398-24-34.

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Object and purpose of research. The object under study is a sandwich plate with two rigid anisotropic layers and a filler of soft isotropic viscoelastic polymer. Each rigid layer is an anisotropic structure formed by a finite number of orthotropic viscoelastic composite plies of arbitrary orientation. The purpose is to develop a mathematical model of sandwich plate. Materials and methods. The mathematical model of sandwich plate decaying oscillations is based on Hamilton variational principle, Bolotin’s theory of multilayer structures, improved theory of the first order plates (Reissner-Mindlin theory), complex modulus model and principle of elastic-viscoelastic correspondence in the linear theory of viscoelasticity. In description of physical relations for rigid layers the effects of oscillation frequencies and ambient temperature are considered as negligible, while for the soft viscoelastic polymer layer the temperaturefrequency relation of elastic-dissipative characteristics are taken into account based on experimentally obtained generalized curves. Main results. Minimization of the Hamilton functional makes it possible to reduce the problem of decaying oscillations of anisotropic sandwich plate to the algebraic problem of complex eigenvalues. As a specific case of the general problem, the equations of decaying longitudinal and transversal oscillations are obtained for the globally orthotropic sandwich rod by neglecting deformations of middle surfaces of rigid layers in one of the sandwich plate rigid layer axes directions. Conclusions. The paper will be followed by description of a numerical method used to solve the problem of decaying oscillations of anisotropic sandwich plate, estimations of its convergence and reliability are given, as well as the results of numerical experiments are presented.

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Buican, George Razvan, Sebastian-Marian Zaharia, Mihai Alin Pop, Lucia-Antoneta Chicos, Camil Lancea, Valentin-Marian Stamate e Ionut Stelian Pascariu. "Fabrication and Characterization of Fiber-Reinforced Composite Sandwich Structures Obtained by Fused Filament Fabrication Process". Coatings 11, n. 5 (19 maggio 2021): 601. http://dx.doi.org/10.3390/coatings11050601.

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The application of fused filament fabrication processes is rapidly expanding in many domains such as aerospace, automotive, medical, and energy, mainly due to the flexibility of manufacturing structures with complex geometries in a short time. To improve the mechanical properties of lightweight sandwich structures, the polymer matrix can be strengthened with different materials, such as carbon fibers and glass fibers. In this study, fiber-reinforced composite sandwich structures were fabricated by FFF process and their mechanical properties were characterized. In order to conduct the mechanical tests for three-point bending, tensile strength, and impact behavior, two types of skins were produced from chopped carbon-fiber-reinforced skin using a core reinforced with chopped glass fiber at three infill densities of 100%, 60%, and 20%. Using microscopic analysis, the behavior of the breaking surfaces and the most common defects on fiber-reinforced composite sandwich structures were analyzed. The results of the mechanical tests indicated a significant influence of the filling density in the case of the three-point bending and impact tests. In contrast, the filling density does not decisively influence the structural performance of tensile tests of the fiber-reinforced composite sandwich structures. Composite sandwich structures, manufactured by fused filament fabrication process, were analyzed in terms of strength-to-mass ratio. Finite element analysis of the composite sandwich structures was performed to analyze the bending and tensile behavior.

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Ashraf, W., M. R. Ishak, M. Y. M. Zuhri, N. Yidris e A. M. Ya’acob. "Experimental Investigation on the Mechanical Properties of a Sandwich Structure Made of Flax/Glass Hybrid Composite Facesheet and Honeycomb Core". International Journal of Polymer Science 2021 (10 marzo 2021): 1–10. http://dx.doi.org/10.1155/2021/8855952.

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This research is aimed at developing the sandwich structure with a hybrid composite facesheet and investigate its mechanical properties (tensile, edgewise compression, and flexural). The combination of renewable and synthetic materials appears to reduce the weight, cost, and environmental impact compared to pure synthetic materials. The hybrid composite facesheets were fabricated with different ratios and stacking sequence of flax and glass fibers. The nonhybrid flax and glass composite facesheet sandwich structures were fabricated for comparison. The overall mechanical performance of the sandwich structures was improved by increasing the glass fiber ratio in the hybrid composites. The experimental tensile properties of the hybrid facesheet and the edgewise compression strength and ultimate flexural facing stress of the hybrid composites sandwich structures were achieved higher when the results were normalized to the same fiber volume fraction of glass composite. The hybrid composite sandwich structure showed improved compression and flexural facing stress up to 68% and 75%, respectively, compared to nonhybrid flax composites. The hybrid composite using glass in the outer layer achieved the similar flexural stiffness of the nonhybrid glass composite with only a 6% higher thickness than the glass composite sandwich structure.

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Chang, Bianhong, Zhenning Wang e Guangjian Bi. "Study on the Energy Absorption Characteristics of Different Composite Honeycomb Sandwich Structures under Impact Energy". Applied Sciences 14, n. 7 (27 marzo 2024): 2832. http://dx.doi.org/10.3390/app14072832.

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A honeycomb structure is a sandwich structure widely used in fuselage, among which the hexagonal honeycomb core is the most widely used. The energy absorption characteristics and impedance ability of the structure are the main reasons that directly affect the energy absorption characteristics of the honeycomb sandwich structure. Therefore, it is necessary to study the out-of-plane mechanical properties of the composite honeycomb sandwich structure. Based on the numerical simulation results, the energy absorption characteristics of several composite honeycomb sandwich structures are verified by drop hammer impact experiments. The research shows that the transient energy absorption characteristics of the composite honeycomb sandwich structure are mainly related to the cell size of the honeycomb structure. The smaller the size of the front cell, the stronger the overall impact resistance; the strength of the composite honeycomb sandwich structure exceeds that of 7075 aluminum alloy-NOMEX and carbon fiber-NOMEX honeycomb sandwich structures. In this paper, the energy absorption characteristics of composite honeycomb sandwich structures under different impact energy are compared and studied. The displacement, force and energy curves of energy absorption characteristics related to time variables are analyzed. The difference in protective performance between the composite honeycomb sandwich structure and existing airframe structure is compared and studied. The optimal structural design parameters of composite honeycomb sandwich under low-speed impact of drop hammer are obtained. The maximum energy absorption per unit volume of the designed honeycomb sandwich structure is 171.7% and 229.8% higher than that of the NOMEX-AL and NOMEX-C structures. The 6.4 mm and 3 mm cell sizes show good characteristics in high-speed buffering and crashworthiness. The composite honeycomb sandwich airframe structure can improve the anti-damage performance of the UAV airframe structure, ensure the same thickness and lightweight conditions as the existing honeycomb sandwich airframe structure, and improve the single-core bearing mode of the existing airframe structure.

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Gu, Xuetao, Jiawen Li, Ji Huang, Yaoliang Ao e Bingxiong Zhao. "Numerical Analysis of the Impact Resistance of Composite A-Shaped Sandwich Structures". Materials 16, n. 14 (16 luglio 2023): 5031. http://dx.doi.org/10.3390/ma16145031.

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This paper focuses on the finite element analysis simulation of the impact properties of composite sandwich structures made of carbon fiber-reinforced polymer lamina. In the existing studies, the composite sandwich structures with A-shaped cores have superior mechanical properties under quasi-static plane compression loads compared to W-shaped, Y-shaped, and X-shaped cores. However, there is limited research on the impact resistance of this structure. This paper studied the resistance of a composite A-shaped core structure to ballistic impact. Using ABAQUS/explicit finite element analysis software, ballistic impact tests for the composite A-shaped core structure were simulated based on the Hashin and Yeh failure criteria with a progressive damage model introduced in the user-defined subroutine VUMAT. First, the composite Y-shaped core sandwich structure was verified via experiments and simulations to determine the accuracy of the method, and then the composite A-shaped sandwich structure was subjected to a series of ballistic impact simulations. With varied impact velocity, the damage to the front and rear face sheet and cores via ballistic loads was simulated to illustrate the overall dynamic response process of the sandwich structure. Subsequently, a curve was fitted using a ballistic limit velocity equation, which was used as the criterion to evaluate the impact resistance of the composite A-shaped core structure. The results showed that, under the same relative density and the same number of component layers, the ballistic limit velocity of the composite A-shaped core sandwich structure was bigger than the composite Y-shaped core sandwich structure. The composite A-shaped core structure had 12.23% higher ballistic limit velocity than the composite Y-shaped core, indicating the impact resistance capabilities of the A-shaped core structure. In addition, the impact location’s effect on the impact response was investigated.

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