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1
Abbasloo, Aslan, and Mohamad Reza Maheri. "On the mechanisms of modal damping in FRP/honeycomb sandwich panels." Science and Engineering of Composite Materials 25, no. 4 (July 26, 2018): 649–60. http://dx.doi.org/10.1515/secm-2015-0444.
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Abstract Sandwich panels made of fibre-reinforced plastic (FRP) skins and a honeycomb core can be effectively damped through the choice of the skin and especially of the core materials. Because the core is often highly damped, a lateral deflection that causes more shearing of the core than bending of the skin increases sandwich damping. Aside from the skin and the core material properties, the shearing/bending ratio depends on a number of other, often interacting, factors, including the sandwich planar as well as transverse dimensions, the particular modal pattern in which the panel vibrates and its relationship to the type of skin layup, as well as the panel end conditions. In the present work, using a simple, first-order shear deformation theory, damping results have been produced for simple modes of vibration of a sandwich panel comprising composite skins and a damped honeycomb core, demonstrating the mechanisms by which the above factors affect the FRP skin/honeycomb core sandwich damping.
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Mironov, Viktor, Mihails Lisicins, and Irina Boiko. "Sandwich Panels Made of Perforated Metal Materials." Solid State Phenomena 320 (June 30, 2021): 155–60. http://dx.doi.org/10.4028/www.scientific.net/ssp.320.155.
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Nowadays, the growing attention has focused on the sandwich-structured composites (panels), especially on those, which are environmentally friendly. The sandwich panel is a special type of the composites made of at least three layers: a core and a skin-layer bonded to each side. The aim of this paper is to investigate the possibility of using of perforated metallic materials for producing sandwich panels for the different application in the civil engineering. By using the perforated metallic materials in combination with different core materials or by using the perforated metallic material as the core material the wide range of products for the construction, damping or isolation purposes could be manufactured. In the paper the example of using of perforated metallic sheet materials for manufacturing the sandwich panels is proposed. Both, the simulation and experimental studies (mechanical testing) were carried out in order to assess the load-bearing capacity of sandwich panels and to prove the applicability of the proposed sandwich panels for construction structures. For the analysis of the achieved structures the finite element analysis (FEA) software was used. The simulation results are well-coincided with the results of the experimental studies. Thus, new types of the sandwich panels and the manufacturing technology thereof are shown its reliability and could be recommended for application in the different branches, in particular for producing lightweight ceiling panels with filler from heat insulating materials.
3
Fajrin, Jauhar, Ni Nyoman Kencanawati, Miko Eniarti, and Arismanto Arismanto. "Core Configuration Effect On The Flexural Behaviour Of Sandwich Panel Made Of Aluminium Skin And Sengon Wood Core." Jurnal Rekayasa Sipil (JRS-Unand) 17, no. 3 (February 26, 2022): 186. http://dx.doi.org/10.25077/jrs.17.3.186-193.2021.
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Among the many choices of composite sandwich panel cores, Balsa wood is one of the main alternatives of cores made of wood. However, the availability and price of Balsa wood are quite expensive, so it needs alternatives from other types of wood such as Sengon wood. The purpose of this study was to evaluate the feasibility of Sengon wood as a core of composite sandwich panels. Three variations of the Sengon wood layout had been prepared as the core of the sandwich panels with a skin made of aluminum. All specimens, including the control specimens made of whole Sengon wood, were prepared with a size of 550 x 50 x 24 mm for length, width, and depth, respectively. Each variation and also the control specimens were made of 3 pieces. Tests were carried out based on the ASTM C 393-94 standard under the three-point bending test scheme. The results showed that the sandwich panel with plain Sengon wood core has the highest capacity to carry a flexural load, which is approximately 177.391 MPa, followed by a sandwich panel with long and end grain Sengon board that possess flexural strength of 153.913 MPa and 79.101 MPa, respectively. The flexural strength of these sandwich panels is superior to solid Sengon wood. The sandwich panels showed a typical ductile material indicated by a non-linear curve without a distinct yielded point before reach the maximum failure load. Three sandwich panels with various Sengon wood cores collapsed under three types of failure mechanisms; face wrinkling, shearing of the core, and delamination between the interface of skin and core. In conclusion, Sengon wood has a great potential to be used as the core material for a composite sandwich panel.
4
Mohamad, Noridah, and Hilmi Mahdi Muhammad. "Testing of Precast Lightweight Foamed Concrete Sandwich Panel with Single and Double Symmetrical Shear Truss Connectors under Eccentric Loading." Advanced Materials Research 335-336 (September 2011): 1107–16. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.1107.
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This paper reports the structural behavior of precast lightweight foamed concrete sandwich panel, PLFP, subjected to eccentric loading. An experiment was conducted to investigate the structural performance of PLFP under this load. Two PLFP panels, PE-1 and PE-2 were cast with 2000 mm in heights, 750 mm in width and 100 mm in thickness. The thickness of the wall is actually a combination of three layers. Skin layers were cast from lightweight foamed concrete while the core layer is made of polystyrene. The skin layers were connected to each other by 9 mm steel shear truss connector which were embedded through the layers. Panel PE-1 was strengthened with single diagonal shear truss connectors made of 6 mm steel rebar while panel PE-2 was strengthened with symmetrical diagonal shear truss connectors of similar steel diameter. Both panels were tested under eccentric load till failure. The results showed that panel with symmetrical double truss connectors, PE-2, is able to sustain higher load compared to panel with single shear truss connector. The load-deflection profiles indicate that both panels achieved certain degree of composite action especially during the later stage of loading where the wythes tend to move in the same direction until they reached failure. The load-strain curves for both panels highlight the inconsistent distribution of surface strain along the height of panels. The overall trend of the strain curves show that they are under compression.
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Yuen, Steeve Chung Kim, Gerald Nurick, and Misha C. du Plessis. "Response of Sandwich Panels with Tubular Cores to Blast Load." Applied Mechanics and Materials 566 (June 2014): 581–85. http://dx.doi.org/10.4028/www.scientific.net/amm.566.581.
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This paper reports on the response of cladding sandwich panels with tubular cores to uniform blast load. The panels consist of thin-walled circular tubes (38 mm in diameter) made from aluminium 6063-T6 riveted laterally between the skin plates at varying spacing arrangements to provide four different types of panels. The skin exposed to the blast load is made from DOMEX 700 Steel while the back face skin is made from mild steel. Varying charge masses of explosive (ranging from 5 g to 40 g) with a prescribed load diameter of 40mm is detonated at a stand-off distance of 200 mm to provide a “uniform” blast load to the sandwich panels. Energy is dissipated mostly through the plastic deformation of the tubular cores. The results show an increase in average deflection with an increase in charge mass/impulse for the different types of panels. The cladding panels with the least interaction between the tubular cores are observed to have the highest energy absorption capabilities for a given charge mass.
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Pereira, Meyrick, Maziar Ramezani, Timotius Pasang, and Ben Withy. "Investigation of Polyurethane Bonding to Steel in Sandwich Panels." Materials Science Forum 890 (March 2017): 401–5. http://dx.doi.org/10.4028/www.scientific.net/msf.890.401.
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Sandwich panels made of thin and stiff skins, connected by a thick and soft core are widely used in load-bearing components mainly due to their high strength to weight ratio. To improve the reliability in using sandwich beams, it is necessary to understand their responses under external mechanical and environmental stimuli. This paper investigates the construction of steel-polyurethane-steel sandwich panels and their mechanical properties. Key properties of a sandwich structure are the adhesion between the skins and the sandwich material, and the load transfer from the outer skin to the inner skin. Lap shear specimens were selected to give an indication of the bond strength of the polyurethane to steel, whilst three point bend test specimens were selected to indicate the degree of load transfer between the skins and the bending resistance provided by the sandwich structure.
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Luengo, Emilio, Francisco Arriaga, Ignacio Bobadilla, and Eva Hermoso. "Mechanical Efficiency and Quality Control Preliminary Analysis of Incompletely Bonded Wood-Based Sandwich Panels." Forests 14, no. 6 (May 23, 2023): 1074. http://dx.doi.org/10.3390/f14061074.
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Wood-based sandwich panels are building products composed of two skins attached to a lightweight continuous core in which at least one skin is made of wood-based products, contributing to the use of renewable forest goods. Since the connection between the skins and the core is often provided by adhesive bonding, its characteristics affect the mechanical behavior of the sandwich and, therefore, must be thoroughly assessed. Full adhesion is often considered the standard situation, although some batches of the commercial product show incompletely glued surfaces, and scarce data is available with regard to their bonding performance. For this reason, analyses were performed using tensile tests with a load perpendicular to the skins and specific shear tests with a load parallel to the longitudinal direction of the panel. The test samples were obtained from wood-based sandwich panels with extruded polystyrene cores and different skin materials. The tensile tests proved to be suitable only for panels with adequate skin material cohesion, their functionality improving as a control method when the glued surface percentage assessment is used together with the tensile strength. The results of the shear tests provided non-linear models relating the effect of the glued surface to the mechanical properties, revealing that the mechanical efficiency of the incompletely bonded specimens is better than that which might be expected if the core only worked in proportion to the glued surface, due to the help of the adjoining non-glued core material.
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Hoxha, Dashnor, Brahim Ismail, Ancuța Rotaru, David Izabel, and Thibaut Renaux. "Assessment of the Usability of Some Bio-Based Insulation Materials in Double-Skin Steel Envelopes." Sustainability 14, no. 17 (August 30, 2022): 10797. http://dx.doi.org/10.3390/su141710797.
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In this paper, a double-skin steel building-demonstrator, set up using panels of five bio-based insulators and a classical mineral insulating material, is studied. The panels used in the demonstrator are made from industrially manufactured and commercialized bio-materials. To assess the suitability of these panels for use in cold formed steel envelope buildings, their advantages and/or the drawbacks (if any) of the synchronized records of temperatures, relative humidity and thermal flux of each panel are obtained using a system of continuous measurements. Data from 6 months of records in the roof of the demonstrator are used to assess the infield properties of the panels and the seasonal evolution of these properties in relation to the presence of the vapor barrier. The thermal resistance of each panel is determined from these data using two methods: the ISO 9869-1:2014 based on the Heat Flow Meter (HFM) method and an inverse problem identification method. All bio-sourced panels manifest higher thermal resistance than the classical insulation system, whatever conditions of use with or without barrier vapor. The seasonal variations of thermal properties are attenuated when a vapor barrier is used. No risk for water condensation inside the bio-insulations is revealed so far.
9
Grenestedt, Joachim L., and Mikael Danielsson. "Elastic-Plastic Wrinkling of Sandwich Panels With Layered Cores." Journal of Applied Mechanics 72, no. 2 (March 1, 2005): 276–81. http://dx.doi.org/10.1115/1.1828063.
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Elastic-plastic wrinkling of compression loaded sandwich panels made with layered cores was studied analytically and experimentally. A core with a stiff layer near the sandwich skins can improve various properties, including wrinkling and impact strengths, with only a minor weight penalty. The 2D plane stress and plane strain bifurcation problems were solved analytically, save for a determinantal equation which was solved numerically. Experiments were performed on aluminum skin/foam core sandwich panels with different combinations of stiff and soft core materials. Good correlation between experiments and theory was obtained.
10
Elnasri, Ibrahim. "Impact perforation of sandwich panels with graded hollow sphere cores: Numerical and Analytical investigations." EPJ Web of Conferences 250 (2021): 02027. http://dx.doi.org/10.1051/epjconf/202125002027.
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In this study, we numerically and analytically investigate the impact perforation of sandwich panels made of 0.8 mm 2024-T3 aluminum alloy skin sheets and graded polymeric hollow sphere cores with four different gradient profiles. A suitable numerical model was conducted using the LS-DYNA code, calibrated with an inverse perforation test, instrumented with a Hopkinson bar, and validated using experimental data from the literature. Moreover, the effect of boundary conditions on the perforation resistance of the studied graded core sandwich panels was discussed. The simulation results showed that the piercing force– displacement response of the graded core sandwich panels is affected by the core density gradient profiles. Besides, the energy absorption capability can be effectively enhanced by modifying the arrangement of the core layers with un-clumping boundary conditions in the graded core sandwich panel, which is rather too hard to achieve with clumping boundary conditions. Finally, an analytical model, taken account only gradient in the quasi-static plateau stress, is developed to predict the top skin pic peak load of the graded sandwich panel.
11
Ashish R. Pawar, Dhanashree S. Ware, Sampada S. Ahirrao, Kashinath H. Munde, Ganesh E. Kondhalkar,. "Analysis of Damping of Sandwich Materials by using Free Vibrations." Mathematical Statistician and Engineering Applications 70, no. 1 (January 31, 2021): 796–806. http://dx.doi.org/10.17762/msea.v70i1.2701.
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Sandwich material panel is a structure made from three layers. A low density core is inserted in between two relatively thin skin layers. This sandwich material is used to achieve excellent mechanical performance at minimal weight. Sandwich panels with polygonal cores are widely used in different structural applications such as aircraft floor panels, control surfaces, civil engineering structures and many more. The main use of these panels is to reduce weight and material usage. These panels undergo various static and dynamic loading along with thermal environment. This project is a comparative study of PVC (Poly Vinyl Chloride), PU (Poly Urethane), GRF( Glass Reinforced fibre) all these sandwich materials. So there is requirement to develop the material which can be used easily for various engineering applications.
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SKOVAJSA, MICHAL, FRANTISEK SEDLACEK, and MARTIN MRAZEK. "DETERMINATION OF MECHANICAL PROPERTIES OF COMPOSITE SANDWICH PANEL WITH ALUMINIUM HONEYCOMB CORE." MM Science Journal 2021, no. 6 (December 15, 2021): 5353–59. http://dx.doi.org/10.17973/mmsj.2021_12_2021132.
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This paper deal with comparison of mechanical properties of composite sandwich panel with aluminium honeycomb core which is determined by experimental measurement, analytic calculation and numerical simulation. The goal was to compared four composite sandwich panels. The composite sandwich panels were made of two different aluminium honeycomb cores with density 32 and 72 kg.m-3 and two different layup of skin with 4 and 5 layers. The comparison was performed on a three-point bend test with support span 400 mm. This paper confirms the possibility of a very precise design of a composite sandwich panel with an aluminium honeycomb core using analytical calculation and numerical simulation.
13
Komarov, V. A., and S. A. Pavlova. "Optimal design of sandwich floor panels made of high-strength composite materials considering stiffness constraints." VESTNIK of Samara University. Aerospace and Mechanical Engineering 20, no. 2 (July 9, 2021): 45–52. http://dx.doi.org/10.18287/2541-7533-2021-20-2-45-52.
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The article considers the challenge of designing sandwich floor panels made of high-strength composites considering stiffness constraints. A dimensionless criterion is proposed for assessing the stiffness of floor panels. A new constraint equation determines an interrelation between geometrical parameters of composite constructions and a given criterion. A demo example and the results of designing a typical floor panel using a high-strength composite material are presented. The mass of a square meter of the structure is considered as an objective function, and the thickness of the skin and the height of the honeycomb core of a sandwich construction are considered as design variables. In order to find the optimal ratio of design variables, a graphical interpretation of the design problem is used considering strength and stiffness constraints in the design space. It is noted that the presence of restrictions on a given value of the permissible relative deflection leads to an increase in the required height of the honeycomb filler with an insignificant consumption of additional mass of the sandwich construction.
14
Labib Adyavit, Muhammad, Larasati Irischa Ramadhani, and Steven Steven. "Kajian Material Komposit Sandwich pada Floor Panel Pesawat Terbang." Mesin 29, no. 1 (July 28, 2023): 45–63. http://dx.doi.org/10.5614/mesin.2023.29.1.4.
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Sandwich composites have been used as lightweight materials in aircraft manufacturing for a long time, from balsa wood sandwich in the 1930s to honeycomb and fiber-reinforced polymers sandwich. Its characteristics are considered as a 'perfect' material for aircraft, which has high strength with low density. Sandwich composites are the common materials for aircraft floor panels. The core is usually made of Nomex or aluminum honeycomb, while the skin is made of 1 "“ 2 ply of carbon/glass fiber in epoxy resin composite. The core is usually constructed using the corrugating or expansion method, whilst the skins are usually constructed using the prepreg lay-up method. Both materials are combined together by a simple adhesive bonding. Being the most strictly regulated transportation method on the planet, floor panel manufacturers must abide by aircraft manufacturing companies and local aviation authority standards and specifications to ensure the product's safety. The purpose of this study is to determine the most used materials for aircraft floor panels and why is it widely used, to understand the manufacturing process, and to know the specifications and standards that need to be fulfilled.
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Epasto, Gabriella, Fabio Distefano, Hozhabr Mozafari, Emanoil Linul, and Vincenzo Crupi. "Nondestructive Evaluation of Aluminium Foam Panels Subjected to Impact Loading." Applied Sciences 11, no. 3 (January 27, 2021): 1148. http://dx.doi.org/10.3390/app11031148.
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Aluminium foam sandwich structures have excellent energy absorption capacity, combined with good mechanical properties and low density. Some of the authors of this paper proposed an innovative Metallic Foam Shell protective device against flying ballast impact damage in railway axles. A closed-cell aluminium foam was chosen for the Metallic Foam Shell device. The main goal of this study was the experimental investigation of the impact responses of aluminium foam panels. Low velocity impact tests were carried out at different energies on different types of aluminium foam panels in order to investigate the effects of some parameters, such as core thickness, skin material and layer. Tests were conducted at repeated impacts on aluminium foam panels without and with skins made of aluminium and glass fibre-reinforced polymer. The experimental results were compared and the impacted panels were investigated by means of the nondestructive techniques ultrasonic phased array and digital radiography.
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Vavrovič, Boris. "Importance of Envelope Construction Renewal in Panel Apartment Buildings in Terms of Basic Thermal Properties." Advanced Materials Research 855 (December 2013): 97–101. http://dx.doi.org/10.4028/www.scientific.net/amr.855.97.
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Envelope constructions of panel apartment buildings in Slovakia are made up of one or more layers of external panels. They typically have one or double-skin flat roofs. Nowadays, almost all envelope constructions, that yet have not been insulated and renovated, show to have insufficient thermoisolation performances. Especially roofs seems to have unsatisfactory moisture regime facilities. The article describes fundamental thermal technical characteristics of envelope constructions (external walls and flat roofs) in panel appartment buildings in their original state and after renewal in the form of additional thermal insulation.
17
Elnasri, Ibrahim, and Han Zhao. "A numerical study of the impact perforation of sandwich panels with graded hollow sphere cores." Advances in Mechanical Engineering 13, no. 4 (April 2021): 168781402110094. http://dx.doi.org/10.1177/16878140211009415.
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In this study, we numerically investigate the impact perforation of sandwich panels made of 0.8 mm 2024-T3 aluminum alloy skin sheets and graded polymeric hollow sphere cores with four different gradient profiles. A suitable numerical model was conducted using the LS-DYNA code, calibrated with an inverse perforation test, instrumented with a Hopkinson bar, and validated using experimental data from the literature. Moreover, the effects of quasi-static loading, landing rates, and boundary conditions on the perforation resistance of the studied graded core sandwich panels were discussed. The simulation results showed that the piercing force–displacement response of the graded core sandwich panels is affected by the core density gradient profiles. Besides, the energy absorption capability can be effectively enhanced by modifying the arrangement of the core layers with unclumping boundary conditions in the graded core sandwich panel, which is rather too hard to achieve with clumping boundary conditions.
18
Meneghin, Ivan, Goran Ivetic, and Enrico Troiani. "Analysis of Residual Stress Effect on Fatigue Crack Propagation in Bonded Aeronautical Stiffened Panels." Materials Science Forum 681 (March 2011): 236–42. http://dx.doi.org/10.4028/www.scientific.net/msf.681.236.
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The application of adhesively bonded straps made of high-static strength materials on aeronautical stiffened panels to retard the fatigue skin crack growth is currently a topical research subject. The detrimental effect of the residual stress fields induced as a consequence of the dissimilar coefficients of thermal expansion of the skin and strap materials on the fatigue skin crack propagation was investigated. The residual stresses induced in a stiffened panel representative of a pressurized fuselage shell with titanium doublers in the middle of the stringer bays is numerically quantified for two likely operational temperatures. Their effect on the fatigue crack propagation is analyzed by means of a linear elastic fracture mechanics approach. The results show that adhesively bonded straps on the cracked surface can significantly retard the fatigue crack propagation but, in order to achieve reliable and conservative predictions on their performances, the effect of the residual stress fields they introduce must be taken into account.
19
Mastali, Mohammad, Joaquim Barros, and Isabel Valente. "Structural performance of hybrid sandwich slabs under shear loading." Journal of Sandwich Structures & Materials 21, no. 3 (April 11, 2017): 809–37. http://dx.doi.org/10.1177/1099636217699660.
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In a hybrid panel with glass fiber-reinforced polymer (GFRP) bottom skin and ribs, and deflection hardening cementitious composites (DHCC) top layer, it is very important to provide good shear connection between these various components in order to increase the load carrying capacity of the resulting hybrid slabs and a larger increment of deflection before the occurrence of the structural softening of this panel. The effectiveness of the proposed hybrid sandwich panels strongly depends on the performance of the shear connectors. The efficiency of indented shear connectors in improving the flexural performance of hybrid sandwich panels is here demonstrated. Since the efficiency of indented shear connectors in the hybrid sandwich panels is unknown, efforts are made in this paper in investigating the shear performance of hybrid slabs. A special focus is given on the indented shear connector’s behavior, considering different shear span ratios in ranges of 2.00, 1.39, and 0.77. In this regard, six hybrid sandwich panels were manufactured and experimentally tested under different shear loads. Then, the results are interpreted comprehensively. The results obtained show that the GFRP rib thickness and height, and shear span ratios influence the damage events and the structural performance of the hybrid sandwich panels. Moreover, it was observed that using indented shear connectors in the hybrid slabs, regardless of the shear span ratios, provides high load capacity, high stiffness, and large residual deflection.
20
Takagi, Hitoshi, Kenya Nishimura, and Antonio N. Nakagaito. "Trial Fabrication of Carbon Fiber-Reinforced Thermoplastic Honeycomb Sandwich Materials." Key Engineering Materials 774 (August 2018): 25–30. http://dx.doi.org/10.4028/www.scientific.net/kem.774.25.
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This paper deals with a new fabrication technique of carbon fiber-reinforced thermoplastic (CFRTP) honeycomb cores and all-CFRTP honeycomb sandwich panels. The CFRTP core was made of plane woven carbon fiber-reinforced polypropylene prepreg sheets. The stacked CFRTP prepreg sheets were periodically hot-pressed at the node locations, and then expanded to form an all-CFRP honeycomb core. The resultant CFRTP honeycomb cores were glued with the same polypropylene-based plain-woven CFRTP skin plates. The mechanical performance of the all-CFRTP honeycomb sandwich panels was evaluated by flexural tests. The experimental results showed the effectiveness of proposed all-CFRTP sandwich panels.
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Brekken, Kristoffer Aune, Aase Reyes, Torodd Berstad, Magnus Langseth, and Tore Børvik. "Sandwich Panels with Polymeric Foam Cores Exposed to Blast Loading: An Experimental and Numerical Investigation." Applied Sciences 10, no. 24 (December 18, 2020): 9061. http://dx.doi.org/10.3390/app10249061.
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Sandwich panels have proven to be excellent energy absorbents. Such panels may be used as a protective structure in, for example, façades subjected to explosions. In this study, the dynamic response of sandwich structures subjected to blast loading has been investigated both experimentally and numerically, utilizing a shock tube facility. Sandwich panels made of aluminium skins and a core of extruded polystyrene (XPS) with different densities were subjected to various blast load intensities. Low-velocity impact tests on XPS samples were also conducted for validation and calibration of a viscoplastic extension of the Deshpande-Fleck crushable foam model. The experimental results revealed a significant increase in blast load mitigation for sandwich panels compared to skins without a foam core, and that the back-skin deformation and the core compression correlated with the foam density. Numerical models of the shock tube tests were created using LS-DYNA, incorporating the new viscoplastic formulation of the foam material. The numerical models were able to capture the trends observed in the experimental tests, and good quantitative agreement between the experimental and predicted responses was in general obtained. One aim of this study is to provide high-precision experimental data, combined with a validated numerical modelling strategy, that can be used in simulation-based optimisation of sandwich panels exposed to blast loading.
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Schagerl, M. "Analytical formulas for the effective width caused by bulging and flattening of curved aircraft panels." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, no. 10 (September 30, 2011): 2399–412. http://dx.doi.org/10.1177/0954406211412314.
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The skin of a curved aircraft panel flattens, if it is subjected to circumferential tension, and bulges, if it is subjected to compression. These deformations distort the hoop stress distribution, which further leads to a reduced load-carrying width of the skin in circumferential direction. The book Roark's Formulas for Stress and Strain (W. C. Young and R. G. Budynas, 2002) presents a method to calculate the effective width of wide flanges of curved beams under tension. Although often used, it is shown in the current article that this method is not applicable to assess the effects of flattening and bulging of aircraft panels. As a reason, the support provided by the longitudinal stringers is identified. The current article consists of two parts. The first part presents the derivation of an analytical method to calculate the effective width caused by bulging and flattening of curved aircraft panels. The underlying model uses standard theories for straight and curved beams and is thus consistent with the assumptions made for Roark's formula. For improving the accuracy of this analytical result, the second part presents a simple procedure to fit this analytical approach to results from parametric Finite Element studies.
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Mitrofanov, O., E. Toropylina, Andrey Smolyaninov, and Inessa Lukmanova. "Design of z-shaped reinforced panels of composite materials under compression and shear." E3S Web of Conferences 383 (2023): 05015. http://dx.doi.org/10.1051/e3sconf/202338305015.
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When designing thin-walled aircraft structures, as a rule, the main limitations are associated with ensuring stability. The objects of research in this work are composite z-shaped reinforced panels of the wing box of an aircraft. For the early stages of the design of load-bearing panels, it is necessary to evaluate the weight of the design decisions made, taking into account possible defects. The paper proposes an analytical technique for designing reinforced panels, taking into account the use of the condition of uniform stability and the presence of possible regulated defects in the skin that may occur in further operation. The task of determining the parameters of panels of minimum weight is reduced to minimizing the function of one variable, which is the ratio of the height to the reinforcement step. To take into account the indicated regulated defects, parametric studies were carried out using the finite element method, on the basis of which refinement coefficients were added to the analytical ratios of the stiffness parameters of the reinforced panels. The paper presents the results of studies of orthotropic panels with defects in the form of through holes under loading with compressive and tangential forces. The results are presented in the form of graphs that show possible changes in the critical stresses of thin skins with defects.
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Damian, Andrei, Marian Alexandru, and Tiberiu Catalina. "Numerical Evaluation of the Solar Collectors Selfshading Related to their Building Integration." Mathematical Modelling in Civil Engineering 13, no. 4 (December 20, 2017): 12–26. http://dx.doi.org/10.1515/mmce-2017-0011.
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AbstractIn view of the recent preoccupation at worldwide level, for the integration of the solar systems components within the building skin, we made a numerical investigation in order to assess the opportunity to implement a long string of solar panels along a horizontal or vertical building surface.The study analyses deals with the phenomenon of self-shading, which appears in the case of medium and large solar systems that use solar panels placed one behind the other, along the same row (individual string), but also under the shape of parallel rows (parallel strings). The study creates a mathematical instrument for the evaluation of the shaded surface depending on the location of the panels and the relative position of the Sun. The shading-caused energy loss is analysed along the one-year period, for each of the 12 months, while the panels are considered either placed on a horizontal surface such as a building terrace, or on a vertical surface, such as a building facade. The simulations are made for six Romanian cities located in different climatic zones, characterized by different levels of solar radiation.
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Liu, Gang, Wei Tang, Ying-Lin Ke, Qing-Liang Chen, and Yunbo Bi. "Modeling of fast pre-joining processes optimization for skin-stringer panels." Assembly Automation 34, no. 4 (September 9, 2014): 323–32. http://dx.doi.org/10.1108/aa-05-2014-036.
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Purpose – The purpose of this paper is to propose a new model for optimizing pre-joining processes quickly and accurately, guiding workers to standardized operations. For the automatic riveting in panel assemblies, the traditional approach of determination of pre-joining processes entirely rests on the experience of workers, which leads to the improper number, location and sequence of pre-joining, the low quality stability and the high repair rate in most cases. Design/methodology/approach – The clearances computation with the complete finite element model for every process combination is time-consuming. Therefore a fast pre-joining processes optimization model (FPPOM) is proposed. This model treats both the measured initial clearances and the stiffness matrices of key points of panels as an input; considers the permissive clearances as an evaluation criterion; regards the optimal number, location and sequence as an objective; and takes the neighborhood-search-based adaptive genetic algorithm as a solution. Findings – A comparison between the FPPOM and complete finite element model with clearances (CFEMC) was made in practice. Further, the results indicate that running the FPPOM is time-saving by >90 per cent compared with the CFEMC. Practical implications – This paper provides practical insights into realizing the pre-joining processes optimization quickly. Originality/value – This paper is the first to propose the FPPOM, which could simplify the processes, reduce the degrees of freedom of nodes and conduct the manufacturers to standardized manipulations.
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Gavva, Lubov' Mikhailovna. "Buckling Problems of Structurally-Anisotropic Composite Panels of Aircraft with Influence of Production Technology." Materials Science Forum 971 (September 2019): 45–50. http://dx.doi.org/10.4028/www.scientific.net/msf.971.45.
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The different approaches were analyzed to investigate the buckling problems of structurally-anisotropic panels made from composite materials. Aircraft composite structure design in the field of production technology is the outlook research trend. New mathematical model relations for the buckling investigation of structurally-anisotropic panels comprising composite materials are presented in this study. The primary scientific novelty of this research is the further development of the theory of thin-walled elastic ribs related to the contact problem for the skin and the rib with an improved rib model. One considers the residual thermal stresses and the preliminary tension of the reinforcing fibers with respect to panel production technology. The mathematical model relations for the pre-critical stressed state investigation of structurally-anisotropic panels made of composite materials are presented. Furthermore, the mathematical model relations for the buckling problem investigation of structurally-anisotropic panels made of composite materials are presented in view of the pre-critical stressed state. The critical force definition of the general bending form of the thin-walled system buckling and the critical force definition of the many-waved torsion buckling are of the most interest in accordance with traditional design practices. In both cases, bending is integral with the plane stress state. Thus, the buckling problem results in the boundary value problem when solving for the eighth order partial derivative equation in the rectangular field. The schematization of the panel as structurally-anisotropic has been proposed as a design model when and the critical forces of total bending form of buckling are determined. For a many-waved torsion buckling study, one should use the generalized functions set. The solution is designed by a double trigonometric series and by unitary trigonometric series. A computer program package is developed using the MATLAB operating environment. The computer program package has been utilized for multi-criteria optimization of the design of structurally-anisotropic aircraft composite panels. The influence of the structure parameters on the level of critical buckling forces for bending and for torsion modes has been analyzed. The results of testing series are presented.
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Zhang, Wen Chao, Yuan Guo, Zhi Dong Guan, Xia Guo, Wei He, and Ri Ming Tan. "Finite Element Analysis of Stiffened Composite Panels Subjected by Low-Velocity Impact." Applied Mechanics and Materials 644-650 (September 2014): 4726–30. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.4726.
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In this paper, the low-velocity performance of stiffened composite panels is investigated experimentally and numerically. In order to illustrate the effect of the stiffener, a number of plain laminates with same lay-up of the skin were impacted in various energies. Progressive damage models based on continuum damage mechanics (CDM) were used in combination with cohesive interface elements to predict the structural response and fracture mechanics of stiffened composite panels. The constitutive mode was implemented into the ABAQUS/Explicit FE code by user-defined material subroutines (VUMAT). The developed FE model made a good prediction about the structural impact response of stiffened panels over the rang of impact energies examined. Very good agreement was achieved between the extent of damage predicted around the impact site and the damage detected by non-destructive technique (NDT) ultrasonic C-scan of the panels.
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Liuzzi, Stefania, Chiara Rubino, Pietro Stefanizzi, and Francesco Martellotta. "Performance Characterization of Broad Band Sustainable Sound Absorbers Made of Almond Skins." Materials 13, no. 23 (December 1, 2020): 5474. http://dx.doi.org/10.3390/ma13235474.
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In order to limit the environmental impact caused by the use of non-renewable resources, a growing research interest is currently being shown in the reuse of agricultural by-products as new raw materials for green building panels. Moreover, the European directives impose the goal of sustainability supporting the investigation of passive solutions for the reduction of energy consumption. Thus, the promotion of innovative building materials for the enhancement of acoustic and thermal insulation of the buildings is an important issue. The aim of the present research was to evaluate the physical, acoustical, and thermal performances of building panels produced by almond skin residues, derived from the industrial processing of almonds. In this paper different mix designs were investigated using polyvinyl acetate glue and gum Arabic solution as binders. Air-flow resistivity σ and normal incidence sound absorption coefficient α were measured by means of a standing wave tube. Thermal conductivity λ, thermal diffusivity α, volumetric heat capacity ρc were measured using a transient plane source device. Finally, water vapor permeability δp was experimentally determined using the dry cup method. Furthermore, a physical characterization of the specimens in terms of bulk density ρb and porosity η allowed to study the correlation existing between the binder and the aggregates and the consequent acoustical and hygrothermal behavior occurring on the different mix designs. The achieved results suggested the investigated materials comparable to the main products currently existing on the market.
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Zhao, Mengmeng, Chuansi Gao, and Min Wang. "Development of Air Ventilation Garments with Small Fan Panels to Improve Thermal Comfort." Sustainability 15, no. 11 (May 23, 2023): 8452. http://dx.doi.org/10.3390/su15118452.
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Air ventilation garments (AVGs) are reported to be effective in improving thermal comfort in hot environments in previous research. The purpose of this study was to develop AVGs with small fan panels and examine their cooling performance. Three AVGs equipped with more, much smaller sized ventilation fans were developed, including FFV (ten small fans all located on the front body), BBV (ten small fans all located on the back body), and FBV (six small fans located on the front body and four small fans located on the back body). Another garment, without ventilation fans but with the same structure and textile material, was made as a reference garment (CON). The cooling performance of the four garments was examined through subject trials in a moderately hot environment of 32 °C and 60% relative humidity. Simulated office work with 70 min of sedentary activity was performed. The results showed that the physiological indexes of the mean body skin temperature, the mean torso skin temperature, and the heart rate in the three AVG scenarios were significantly lower than those in the CON condition (p < 0.05). Thermal sensation, thermal comfort, and wetness sensation were also improved when wearing the three AVGs (p < 0.05). No significant difference was displayed among the three AVGs on the whole body and the whole torso (p > 0.05) due to the similarity of the air velocity created by the fan panels. A significant difference was found on the local torso skin, with FFV significantly reducing the chest and the belly skin temperature, and BBV significantly reducing the scapula and the lower back skin temperature (p < 0.05). This study indicates that the AVGs with the small fan panels were effective in reducing heat strain and improving thermal comfort, and thus are recommended for use in hot environments.
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Tsangouri, Eleni, Hasan Ismail, Matthias De Munck, Dimitrios G. Aggelis, and Tine Tysmans. "Reveal of Internal, Early-Load Interfacial Debonding on Cement Textile-Reinforced Sandwich Insulated Panels." Applied Sciences 11, no. 2 (January 19, 2021): 879. http://dx.doi.org/10.3390/app11020879.
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Internal interfacial debonding (IID) phenomena on sandwich façade insulated panels are detected and tracked by acoustic emission (AE). The panels are made of a thin and lightweight cementitious composite skin. In the lab, the panels are tested under incremental bending simulating service loads (i.e., wind). Local (up to 150 mm wide) skin-core detachments are reported in the early loading stage (at 5% of ultimate load) and are extensively investigated in this study, since IID can detrimentally affect the long-term durability of the structural element. A sudden rise in the AE hits rate and a shift in the wave features (i.e., absolute energy, amplitude, rise time) trends indicate the debonding onset. AE source localization, validated by digital image correlation (DIC) principal strains and out-of-plane full-field displacement mapping, proves that early debonding occurs instantly and leads to the onset of cracks in the cementitious skin. At higher load levels, cracking is accompanied by local debonding phenomena, as proven by RA value increases and average frequency drops, a result that extends the state-of-the-art in the fracture assessment of concrete structures (Rilem Technical Committee 212-ACD). Point (LVDT) and full-field (AE/DIC) measurements highlight the need for a continuous and full-field monitoring methodology in order to pinpoint the debonded zones, with the DIC technique accurately reporting surface phenomena while AE offers in-volume damage tracking.
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Croitoru, Emilian Ionut, and Gheorghe Oancea. "Impact Properties of Parts Manufactured from Fiberglass and Kevlar Composite Panels." Applied Mechanics and Materials 809-810 (November 2015): 938–43. http://dx.doi.org/10.4028/www.scientific.net/amm.809-810.938.
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This paper presents a method of finite element modelling used to study the effect of laminates orientation and thickness on impact properties of a composite sandwich panel made of glass and kevlar fibers in an epoxy resin matrix. In this research, the composite sandwich panel consists of a fuselage skin panel from an aircraft having two configurations: (0/90/0/90/core/90/0/90/0) and (0/90/45/-45/core/-45/45/90/0). This panel is loaded with one uniform distributed abuse loading case and the stress variation within the composite panel for each configuration is determined.
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Kananen, Markku, Antti Järvenpää, Matias Jaskari, and Kari Mäntyjärvi. "Mechanical Properties of a “Simple Panel Structure” Manufactured of an Ultra High Strength Stainless Steel." Key Engineering Materials 786 (October 2018): 319–24. http://dx.doi.org/10.4028/www.scientific.net/kem.786.319.
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Corrugated core panels contain a formed, corrugated core bonded between two skin sheets. These panels are typically used in applications, where a low weight is required with integrity in stiffness. This paper demonstrates the mechanical properties of a simple panel structure (SPS), constructed using strips of work-hardened, austenitic stainless steel (ASS) grade 1.4310 (type 301) with the yield strength (YS) of ~1200 MPa. The 0.5 mm thick strips were formed into a C-shape and subsequently laser welded together by lap joints to form a SPS. The thickness of the SPS was 50 mm. The bending tests for the SPS were carried out transverse and 45-degrees related to the orientation of the web sheet. The results showed that the SPS, as loaded in the transverse direction, has about the same bending stiffness prior yielding as that of the previously tested 6 mm thick, low carbon S355 plain steel sheets, but the SPS is three times lighter than 6mm thick plain steel sheet. Compared with a corrugated core panel made of an annealed ferritic stainless steel (SS-panel) with the YS ~ 250 MPa, the weight of the both panels are roughly the same, but the bending resistance of the SPS is 45% higher. Experimental tests also verified that the benefit in the stiffness is quickly reduced if the load direction differs from transverse. In the 45-degrees loading direction, the SPS and the SS-panel had almost the same bending strength. On the other hand, the SPS and the SS-panel stiffnesses are much better than that of the carbon steel (the YS ~ 300 MPa) panel (CS-panel) in the both loading directions – the SPS being twice as stiff as the CS-panel.
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Korcz-Konkol, Natalia, and Piotr Iwicki. "Corrugated Sheeting as a Member of a Shear Panel Under Repeated Load—Experimental Test." Materials 13, no. 18 (September 11, 2020): 4032. http://dx.doi.org/10.3390/ma13184032.
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In stressed-skin design, the cladding stiffening effect on structures is taken into account. However, the “traditional” design is more usual, wherein this effect is neglected. Even if the diaphragm actions are not regarded, in particular cases such as big sheds (and others), the parasitic (unwanted) stressed-skin action may occur with the result of leakage or even failure. The structures of this kind have already been built. Thus, an important question arises: How can one assess them if there is a need to correct or redesign them? What kind of non-destructive approach can be used to achieve that? Experimental tests of small-scale shear panels made of trapezoidal sheeting were designed in order to observe the behaviour of the diaphragm under increasing and repeated load. The tests were oriented toward force–displacement relations and strains in selected areas of the sheeting. The results revealed nonlinear, hysteretic force–displacement behaviour of the panel and the occurrence of the persistent deflections and stresses which remain even after the unloading. The relation among the stresses, force–displacement paths and modes of failure can be potentially used in monitoring systems of existing buildings in terms of parasitic stressed-skin action.
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Azouaoui, Krimo, and Said Mouhoubi. "Study on Damage Modes of a Sandwich Panel Impacted Repeatedly." Advanced Materials Research 980 (June 2014): 147–51. http://dx.doi.org/10.4028/www.scientific.net/amr.980.147.
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This paper describes an experimental investigation for determining the damage modes under low energy impact-fatigue of sandwich panels consisting of aluminum skins supported by honeycomb core made of aluminum. Square samples of 125mm by 125mm sides and 10mm thickness (skin of 0.6mm and 8.8mm of core) were subjected to impact fatigue loading using a testing machine at four different energy levels (2J, 3J, 5J and 7J). The square plates are clamped in a fixture system over a 100mm diameter hole. Three different diameters of impactor head (15mm, 25mm and 35mm) are used to study their influence on life duration of the sandwich plates. Results showed that damage area at impacted face and propagation of multi-cracks at rear face are greatly affected by energy level and impactor diameter.
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Hassanin, Ahmed H., Zeki Candan, Cenk Demirkir, and Tamer Hamouda. "Thermal insulation properties of hybrid textile reinforced biocomposites from food packaging waste." Journal of Industrial Textiles 47, no. 6 (June 30, 2016): 1024–37. http://dx.doi.org/10.1177/1528083716657820.
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Due to the significant and harmful effect of the global warming on our communities, health, and climate, the usage of thermal insulation material in building is must to decrease the energy consumption and to improve energy efficiency. On the other hand, the utilization of waste and biomass resources for developing new bio-based composite materials is attracting much attention for the environmental and socioeconomics. Therefore, in this study, thermal insulation bio-based composite panels from Tetra Pak® waste and wool fiber waste with different ratios were manufactured. Likewise, other sandwich bio-based composite panels were manufactured using Tetra Pak waste as a core material with glass woven fabric and jute wove fabric as skin materials. Thermal conductivity and thermal resistance results showed a significant improvement on thermal insulation properties of the developed biocomposite panels compared to the control samples made of plain Tetra Pak®.
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Larin, A. A., M. Yu Fedotov, O. N. Budadin, V. A. Aniskovich, S. O. Kozel’skaya, and V. I. Reznichenko. "ON THE EXPERIENCE OF COMPUTED X-RAY TOMOGRAPHY OF REINFORCED THREE-STRINGER PANELS MADE OF POLYMER COMPOSITE MATERIALS." Kontrol'. Diagnostika, no. 274 (April 2021): 40–49. http://dx.doi.org/10.14489/td.2021.04.pp.040-049.
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Experimental studies of the possibility of the MCT method for NC three-stringer panels made of PCM by the method of autoclave molding have been carried out. Based on the results of the experimental studies, it was shown that the MCT method makes it possible with a high reliability to identify defects in composite structures at the stage of final inspection (immediately after production), which is especially important for highly loaded and critical structures made of carbon composite materials based on polymer matrices of various types. On the example of testing a three-stringer (reinforced) panel, it is shown that the presented structure as a whole does not have pronounced macrodefects, however, an accumulation of micro-layers is observed in the zone of transition of layers from the sheathing plane to the stringer, which indicates a slight decrease in the molding pressure in this zone. In the studies carried out, these microdefects are not critical, while the results of the tomogram can be used to slightly refine the shape of the tooling in the zone of transition of layers from the skin to the stringer to provide the required molding pressure. Thus, it has been shown that the SRT method is an effective tool for assessing the structure of reinforced composite panels, taking into account different degrees of damage. The high measurement accuracy and resolution of the MCT method allow realizing high reliability and information content of control and ensuring high reliability of PCM structures due to the following factors: • Structures with defects exceeding the maximum permissible ones are not allowed into operation by the technical control department (QCD); • Structures with defects close to the maximum permissible are taken out of service until their properties are restored; • Positioning of defects reduces the labor intensity of repair.
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Bisagni, C., and R. Vescovini. "A fast procedure for the design of composite stiffened panels." Aeronautical Journal 119, no. 1212 (February 2015): 185–201. http://dx.doi.org/10.1017/s0001924000010332.
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AbstractThis paper describes the analysis and the minimum weight optimisation of a fuselage composite stiffened panel made from carbon/epoxy material and stiffened by five omega stringers. The panel investigated inside the European project MAAXIMUS is studied using a fast tool, which relies on a semi-analytical procedure for the analysis and on genetic algorithms for the optimisation. The semi-analytical approach is used to compute the buckling load and to study the post-buckling response. Different design variables are considered during the optimisation, such as the stacking sequences of the skin and the stiffener, the geometry and the cross-section of the stiffener. The comparison between finite element and fast tool results reveals the ability of the formulation to predict the buckling load and the post-buckling response of the panel. The reduced CPU time necessary for the analysis and the optimisation makes the procedure an attractive strategy to improve the effectiveness of the preliminary design phases.
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Croitoru, Emilian Ionut, and Gheorghe Oancea. "Effect of Laminates Orientation on Impact Properties of Fiberglass and Kevlar Composite Panels." Applied Mechanics and Materials 808 (November 2015): 119–24. http://dx.doi.org/10.4028/www.scientific.net/amm.808.119.
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This paper presents the study of the effect of laminates angle on impact properties of a composite panel made of glass and Kevlar fibers using finite element modelling. In this research, the composite panel consists of a skin panel, specifically the front left wing, from an automotive vehicle having multiple configurations. A distributed pressure on the composite package represents the loading on the selected panel modelled as one uniform distributed abuse loading case and the stress variation within the composite panel for each configuration is determined. The results of these analyses are used for the determination of mathematical models for tensions, longitudinal and shear tensions, as functions of laminate angle for each configuration.
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Corrao, Rossella. "Mechanical Tests on Innovative BIPV Façade Components for Energy, Seismic, and Aesthetic Renovation of High-Rise Buildings." Sustainability 10, no. 12 (November 30, 2018): 4523. http://dx.doi.org/10.3390/su10124523.
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The paper shows the results of mechanical tests carried out on prototypes of a new Building Integrated Photovoltaic (BIPV) component developed by the author and SBskin Smart Building Skin s.r.l. This patented innovative component is able to merge structural function, insulation proprieties, and production of clean energy for retrofit actions and/or the construction of translucent façades in high-rise buildings located in different climatic contexts. Due to colored PV cells integrated into 3 Dimensional (3D) glass components and the dry-assembly system used for assembling them into precast and pre-stressed panels, an easy and creative customization of the product is allowed. Green energy production, safety, and energy efficiency of buildings can be assured in accordance with the environmental conditions and users’ needs. The pre-stressing force used to improve the mechanical resistance of the panel toward horizontal forces due to winds and earthquakes guarantees the construction of secure translucent and active building envelopes. The paper summarizes the features of this innovative and patented BIPV product by focusing on its mechanical behavior. Laboratory tests are described and commented for underlining the benefits derived from the use of the dry-assembly system and of the supporting structure made of plastic for the construction of the panels. Bending and breaking strength tests have been carried out on two sq.m of panel prototypes, which have been dry-assembled through a supporting structure made of Polypropylene (PP) in order to compare the results with the theoretical calculations derived from the Finite Element (FE) simulations. Cyclic mechanical testing of the panel has been also carried out to verify its behavior under cyclic loading and understanding its ability to counteract the actions of the wind and earthquake.
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Ucan, Hakan, Joachim Scheller, Chinh Nguyen, Dorothea Nieberl, Thomas Beumler, Anja Haschenburger, Sebastian Meister, et al. "Automated, Quality Assured and High Volume Oriented Production of Fiber Metal Laminates (FML) for the Next Generation of Passenger Aircraft Fuselage Shells." Science and Engineering of Composite Materials 26, no. 1 (January 28, 2019): 502–8. http://dx.doi.org/10.1515/secm-2019-0031.
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AbstractThe use of fiber-metal laminates (FML) allows for substantial advantages over a fuselage skin made of monolithic aluminum materials. Glass fiber prepreg reinforced aluminium is characterized by high damage tolerance capabilities, supporting the structural strength capability in case of any kind of damage. For this reason, FML, and GLARE in particular, have been identified as superior materials for aerospace applications. More than 400m2 FML is applied on each A380, as skin panels and as D-noses for both, vertical and horizontal stabilizer. FML possess the potential to become the baseline material for next-generation single-aisle aircrafts [1, 2, 6].The development of a new production chain that will allow automated fuselage production for future short-haul aircrafts is the focus of the studies that make up the joint project AUTOGLARE. As part of the fifth call-up for the German Aeronautical Research Programme (LuFo), the German Aerospace Center (DLR) is working with its project partners Airbus Operations, Premium Aerotech (PAG) and the Fraunhofer Gesellschaft (FhG). The development of a production chain for stiffened fuselage panels made of Fiber metal Laminates should support a production rate of 60 aircraft per month [3].This study contains the research work of the DLR and FhG regarding the automated and quality assured process for chain stiffened FML fuselages. In addition to a detailed explanation of the systems that were set up, this paper covers the planned tests, the completed demonstration models and the findings derived from them.
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Fernández-Calvo, Ana Isabel, Clara Delgado, Philippe Dufour, Egoitz Aldanondo, Mario Díaz, and María Belén García-Blanco. "New EoL Routes of Al-Li Aircraft Integral LBW and FSW Welded Panels including New Cr-Free Coatings." Crystals 13, no. 5 (May 11, 2023): 807. http://dx.doi.org/10.3390/cryst13050807.
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The end of fife (EoL) of new aircraft panels made of Al-Li alloys in which the stringers and skin were joined, either by laser beam welding (LBW) or by friction stir welding (FSW), was investigated at the lab scale. Different cutting strategies, ranging from cutting only for size reduction to full separation of all materials, including the removal of the welded seam, were defined, with the objective of recycling the maximum amount of panel scrap back into high-quality aircraft Al-Li alloys. Those welded aerostructures were coated with two novel Cr-free coating systems. The effect of the coatings on the recyclability of the panels and the need to eliminate the primer and topcoats were researched. Fading/enrichment of the alloying elements during recycling was determined. The chemical compatibility of the recycled alloys with four commercial Al-Li alloys was examined. The EoL route that maximized closed-loop recycling and the conservation of the valuable alloying elements was identified. Nine out of the ten configurations were found to be compatible with joint recycling. Only the LBW structure with ER4047 filler wire required sorting into scrap fractions and removing the weld seam. Decoating by corundum blasting followed by cutting before remelting is the recommended EoL process.
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Heitmann, M., P. Horst, and D. Fitzsimmons. "Effective stiffness of postbuckled stiffened metallic panels under combined compression and shear stress." Journal of Strain Analysis for Engineering Design 38, no. 6 (August 1, 2003): 539–55. http://dx.doi.org/10.1243/030932403770735908.
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The paper deals with the analysis of the effective stiffness of stiffened metallic panels under combined compression and shear stress as used, for example, in aircraft fuselages. The first part presents the realization of the compression and shear test facility in a finite element model. Verification of the finite element model is important for subsequent parameter variations. The second part of the paper presents the approach used to find the effective skin stiffness. On the one hand, a comparison between the results for pure compression stress and the effective width method is made and, on the other hand, the results for pure shear stress are compared with the method of Kuhn. A new approach is derived from the finite element results for combined compression and shear stress. Further parametric studies are necessary to verify the new method.
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Максименков, В. И., М. В. Молод, and П. С. Огурцов. "LAYERED PANEL FOR THE AIR INTAKE CHANNEL OF THE AIRCRAFT." ВЕСТНИК ВОРОНЕЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНИЧЕСКОГО УНИВЕРСИТЕТА, no. 2 (May 5, 2023): 135–39. http://dx.doi.org/10.36622/vstu.2023.19.2.020.
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рассмотрены вопросы проведения анализа применяемых сотовых панелей в каналах воздухозаборника самолетов. Приведены трехслойные сотовые панели, применяемые в конструкции пассажирских самолетов, соответствующих 4 главе Международного стандарта ИКАО (Конвекция о международной гражданской авиации). Поставлена задача повышения акустической эффективности слоистых панелей за счет создания новых конструкций. Приведена трехслойная конструкция, подтвержденная патентом, которая состоит из верхнего несущего слоя, выполненного из перфорированной обшивки и сеток С 685, и слоев сотового заполнителя, плотность которых меняется от верхнего слоя к нижнему в соотношении 1:2:3. Такая конструкция расширяет спектр частот, обеспечивая широкополосное поглощение шума. Выполнены расчеты плотности каждого слоя сотовой панели. Проведены прочностные расчеты образцов сотового заполнителя с различной плотностью. Полученные значения предела прочности на сжатие определяют выбор слоистой конструкции с учетом допустимых требований. Разработан технологический процесс изготовления трехслойной панели, позволяющий получать слоистые панели требуемого качества. Проведен весовой расчет, позволяющий определить, что разработанная конструкция практически снижает вес более чем в 1,5 раза по сравнению с базовым вариантом. Проведенные испытания выявили повышение акустической эффективности конструкции панели по сравнению с базовым вариантом the article deals with the issues of analysis of honeycomb panels used in aircraft structures. The three-layer honeycomb panels used in the design of passenger aircraft, which provide the 4th chapter of the International ICAO Standard, are given. The task was set to increase the acoustic efficiency of layered panels by creating new structures. A three-layer design is presented, confirmed by a patent, which consists of an upper carrier layer made of perforated skin and C 685 meshes, and layers of honeycomb core, the density of which varies from the upper layer to the lower one in the ratio 1:2:3. This design expands the frequency spectrum, providing broadband noise absorption. Calculations of the density of each layer of the honeycomb panel are made. Strength calculations of samples of honeycomb filler with different densities were carried out. The obtained values of the ultimate compressive strength determine the choice of a layered structure, taking into account the allowable requirements. A technological process for the manufacture of a three-layer panel has been developed, which makes it possible to obtain layered panels of the required quality. A weight calculation was carried out, which makes it possible to determine that the developed design practically reduces the weight by more than 1.5 times compared to the base case. The tests carried out revealed the acoustic efficiency of this design by more than 2 times compared to the base case
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Mills, James A., Andrew W. Hamilton, David I. Gillespie, Ivan Andonovic, Craig Michie, Kenneth Burnham, and Christos Tachtatzis. "Identifying Defects in Aerospace Composite Sandwich Panels Using High-Definition Distributed Optical Fibre Sensors." Sensors 20, no. 23 (November 25, 2020): 6746. http://dx.doi.org/10.3390/s20236746.
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Automated methods for detecting defects within composite materials are highly desirable in the drive to increase throughput, optimise repair program effectiveness and reduce component replacement. Tap-testing has traditionally been used for detecting defects but does not provide quantitative measurements, requiring secondary techniques such as ultrasound to certify components. This paper reports on an evaluation of the use of a distributed temperature measurement system—high-definition fibre optic sensing (HD-FOS)—to identify and characterise crushed core and disbond defects in carbon fibre reinforced polymer (CFRP)-skin, aluminium-core, sandwich panels. The objective is to identify these defects in a sandwich panel by measuring the heat transfer through the panel thickness. A heater mat is used to rapidly increase the temperature of the panel with the HD-FOS sensor positioned on the top surface, measuring temperature. HD-FOS measurements are made using the Luna optical distributed sensor interrogator (ODISI) 9100 system comprising a sensor fabricated using standard single mode fibre (SMF)-20 of external diameter 250 μm, including the cladding. Results show that areas in which defects are present modulate thermal conductivity, resulting in a lower surface temperature. The resultant data are analysed to identify the length, width and type of defect. The non-invasive technique is amenable to application in challenging operational settings, offering high-resolution visualisation and defect classification.
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Дибир, А. Г., А. А. Кирпикин, and Н. И. Пекельный. "ЩОДО ПИТАННЯ ПРО РАЦІОНАЛЬНУ ФОРМУ ПРЕСОВАНОГО БУЛЬБОКОСИНЦЯ." Open Information and Computer Integrated Technologies, no. 87 (June 30, 2020): 165–72. http://dx.doi.org/10.32620/oikit.2020.87.09.
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In airplane building and helicopter engineering a bulb angle bar an angle bar with a bulb at the end of a wall are widespread. They are better than a simple angle bar, since they have higher critical stresses under compression more than the proportionality limit. They are better than T bar, as T bar are fastened with two rows of rivets, which impairs tightness. Bulb angle bar are better than Z bar. The latter are higher, which reduces the structural height of the cross section and increases the load on the panel and usually have an excess cross-sectional area. Bulb angle bars are widely used in the structure of metal fuselages of airplanes and helicopters, in the tail boom of helicopters, in the wing and tail unit of light aircraft, in flaps, ailerons and rudders. However, modern the bulb angle bar have a significant drawback.When a bulb angle bar is loaded by a transverse load from the skin in the wing structure, tail unit, fuselage, except of normal stresses from bending of the stringer with attached skin, supported by ribs or frames, additional normal and shear torsional stresses arise. This torsion is caused by the fact that the lateral load is not applied at the center of the bend. Additional stresses reduce the service life and tightness of the structure in this place. An altered cross-sectional shape of the bulb is proposed for use in light aircraft panels to increase their strength and service life. The change in shape had a significant impact on the location of the center of the bend in the cross section. The determination of the position of the center of the bend in the balloncube was carried out using the Wagner model with walls not working for shear stresses. The modified cross-sectional shape of the bulbogon allowed to reduce the level of residual stresses after the panels were assembled, to rationally transfer the load from the casing to the stringer and to improve the technology of their assembly in the panels. It is recommended to drill holes for rivets in the stringer in the middle of the entire width of its shelf, taking into account the wall.A modified cross-sectional shape of a corner with bulb is proposed for use in light aircraft panels. The change in shape had a significant impact on the location of the center of the bend in the cross section. This made it possible to reduce the level of residual stresses after the assembly of the panels, to rationally transfer the load from the casing to the stringer and to improve the technology of their assembly.
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Mirdehghan, Abolfazl, Hooshang Nosraty, Mahmood M. Shokrieh, Roohallah Ghasemi, and Mehdi Akhbari. "Micromechanical modelling of the compression strength of three-dimensional integrated woven sandwich composites." Journal of Industrial Textiles 48, no. 9 (March 16, 2018): 1399–419. http://dx.doi.org/10.1177/1528083718764909.
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This paper is concerned with a theoretical and experimental verification of a micromechanical model of newly developed sandwich panels denoted as 3D integrated woven sandwich composite panels. The integrated hollow core was made of a pile of 3D bars with a special configuration. Integrated woven sandwich composite panels consist of two fabric faces which were interwoven by pile fibers and therefore a very high skin core debonding resistance was obtained. With the objective of qualifying the mechanical properties of these structures, fairly extensive experimental research was carried out by investigators. Although some numerical methods have been developed to predict the mechanical behaviors of these structures, there are less analytical models in this area. Due to the computational difficulties and the time consuming nature of the finite element method, in the present study, a new micromechanics analytical model has been suggested for predicting the compressive strength of integrated woven sandwich composites. In order to evaluate the proposed model, fabricated samples with different pile heights and pile distribution densities were subjected to flatwise compression tests. The results show that compressive properties of integrated woven sandwich composite panels are decreased with the increase of core heights and increased greatly with that of the pile density. Furthermore, the micromechanics model reasonably predicted the compression strength, and there is a good agreement between the experimental data and model predictions.
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Citarella, Roberto G., M. Silvestri, and A. Apicella. "DBEM Crack Growth Simulation and Experimental Results for a Multi-Layer and Multi-Material Aeronautic Panel." Key Engineering Materials 324-325 (November 2006): 1123–26. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.1123.
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A special specimen was created cutting a rectangular notched area from the surrounding of the upper left corner of a wide body aircraft door. This part of the aircraft skin is made of different layers with variable thickness and material (titanium or aluminum). Then a fatigue traction load was applied and some notches were cut in the different layers in order to speed up the crack initiation and reproduce a realistic crack scenario. Such through cracks were monitored during their propagation along the specimen width, in order to have available for the simulation a realistic initial scenario and experimental propagation data useful for the correlation with the simulated crack path and growth rates. In particular an innovative DBEM modelling approach was devised, using a commercial code (BEASY), capable of explicitly modelling the different test article layers with their rivet connections even in a two-dimensional approach. The results of the simulation show a satisfactory correlation with the experimental crack path and growth rates even for such a complex problem: three different panels (one skin with two doublers), made of different materials, each one with a variable thickness and connected through numerous rivets (whose shear stiffness is taken into account for the simulation).
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Aldrete, Jonathan, Christopher J. Peterson, James A. Tarbox, and John S. Pixley. "Polymyositis Presenting With Nontraumatic Rhabdomyolysis and Dysphagia: A Case Report." Journal of Investigative Medicine High Impact Case Reports 10 (January 2022): 232470962210745. http://dx.doi.org/10.1177/23247096221074589.
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Idiopathic inflammatory myopathies (IIMs) are a rare, heterogeneous group of diseases with a characteristic clinical presentation consisting of muscle inflammation and weakness. They often present with accompanying extra-muscular findings, most notably in the skin, lungs, and joints. Inflammatory myopathies are also identified by their characteristic laboratory abnormalities, including a 10- to 50-fold increase in creatinine kinase, elevated liver enzymes, and characteristic electromyography and magnetic resonance imaging findings. Distinct autoimmune markers and clinical phenotypes have advanced our understanding of IIMs and have led to the recognition of 5 distinct entities, each with its unique pathophysiology, autoimmune markers, and clinical features. While autoimmune panels and muscle biopsies help clinicians distinguish one entity from the other, their sensitivity and specificity vary. Of the various inflammatory myopathies, polymyositis remains the most elusive. Often, the diagnosis is ultimately made by combining clinical findings and laboratory data. As our case report illustrates, clinicians must use this constellation of data to initiate treatment for suspected polymyositis despite negative autoimmune panels and negative muscle biopsy.
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Zhao, Han, I. Elnasri, and Hui Jian Li. "Cellular Structures under Impact Loading." Materials Science Forum 539-543 (March 2007): 1880–85. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.1880.
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This paper presents a study of the strength enhancement under impact loading of metallic cellular materials as well as sandwich panels with cellular core. It begins with a review of likely causes responsible for the strength enhancement of cellular materials. A testing method using 60mm diameter Nylon Hopkinson pressure bars is used to investigate the rate sensitivity of various metallic cellular materials. In order to identify the factor responsible for the strength enhancement of those materials, an experimental analysis is performed on a model structure which is a square tube made of rate insensitive materials. Significant enhancement is experimentally observed under impact loading, whereas the crushing mode is nearly the same under both static and impact loading. Finally, an inversed perforation test on sandwich panels with an instrumented pressure bar is also presented. Such a new testing setup provides piercing force time history measurement, generally inaccessible. Testing results show a notable enhancement of piercing forces, even though the skin aluminum plates and the foam cores are nearly rate insensitive.
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Brahma, Siddhartha, Vikas Patel, Selvum Pillay, Haibin Ning, and Vinoy Thomas. "Characterization of discontinuous carbon fiber liquid molded PA-6 composites via strategic placement of additional reinforcements." Journal of Reinforced Plastics and Composites 37, no. 22 (August 22, 2018): 1335–45. http://dx.doi.org/10.1177/0731684418793718.
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The flexibility of processing PA6-based discontinuous carbon fiber panels using vacuum-assisted resin transfer molding was studied. The ease of incorporating various reinforcements namely baseline, tow in the center of preform, fabric in the center of preform and fabric on the outside as skin was investigated. Mechanical characterization was conducted on all the variations made. There was an average increase of about 3%, 20% and 47% in the tensile properties of tow in the center, fabric in the center and fabric on the outside as skin, respectively, as compared to the baseline. A similar increase in properties was noticed in its flexural and impact strength. The data showed a correlation between the mechanical properties and the total surface area of additional reinforcements used. As the surface area of the reinforcement increased, the mechanical properties increased as well. It also showed that reinforcements on the surface of the preform as a skin performed the best. DMA analysis showed the effect of reinforcement on the storage modulus and tan delta across temperatures ranging from 30°C to 150°C. SEM analysis showed that the fibers and the additional reinforcements were coated with PA6 which translated into consistent mechanical performance.