Minimum weights of pressurized hollow sandwich cylinders with ultralight cellular cores
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Shearing (physics)
The pratt truss with diagonals omitted for passageways is the most efficient type of truss to be used in the staggered truss(system).To be economical for mass production,the trusses throughout the building should be identical in form and type of members,designed so that jigs can accommodate the slight differences in member dimensions.This paper analyzes the varieties of the load bearing behavior of the truss from the different location of the vierendeel panel and the different arrangements of web members,and it illustrates that the vierendeel panel can't be placed at the end of the truss.It also give the feasible styles for web members of the staggered truss system.
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Composite lattice truss structures are new type materials with many advantages such as lightweight,high specific stiffness,specific strength and multifunctional applications,leading to heightened concerns among researchers at home and abroad.Composite lattice truss structure is one of the new material structures having the best foreground in the world.This article presents a comprehensive review on novel composite sandwich panels with lattice truss cores,including studies on topology design,fabrication method,mechanical properties,failure mechanism and analytical models.Mechanical properties,failure mechanism and prediction models are studied for composite sandwich panels with lattice truss cores.Especially,the modified strength-density charts are provided in the present paper.Potential applications of composite sandwich panels with lattice truss cores are summarized and development tendency of composite lattice truss structures is pointed out.
Lattice (music)
Failure mechanism
Sandwich panel
Specific strength
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Metallic sandwich panels with periodic truss core are an important new structure.The geometric models and fabrication of periodic metallic truss core sandwich panels are introduced briefly in this paper.Emphasis is placed on the recent development of the experimental and theoretical research of mechanical properties of metallic truss core sandwich panels.The influence of key factors,including properties of parent metal,relative densities of truss core,an alternative core topology,heat treatment of sandwich panels and the influence of joining technique of truss core and panels on mechanical properties,are analyzed.Some future research trends are also presented.
Sandwich panel
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This repart gives theoretical and experimental analysis for the lateral stability of trusses. The general formula for buckling load of the truss is presented. It is gained by an approximate analysis, using the energy method, for the elastic stability out of the plane of the truss. The truss is an elastic plane truss with parallel chords and it, in the present treatment, is considered as a whole. The result applies to any arrangement of vertical and diagonal web members. As the experimental investigation, tests on full size trusses are carried out. The trusses are composed of circular steel tubes and warren type webs are joined rigidly to the main chards of trusses. The most of the test results are found in general to be in good agreement with the theoretical works. In addition, it is found that the lateral buckling load of these trusses is very high, because of the high tarsional rigidity of circular tube. Special mention must be made of these results.
Rigidity (electromagnetism)
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In this study, the effects of the core layering of sandwich structures, as well as arrangements of these layers on the ballistic resistance of the structures under high-velocity impact, were investigated. Sandwich structures consist of aluminum face-sheets (AL-1050) and polyurethane foam core with different densities. Three sandwich structures with a single-layer core of different core densities and four sandwich structures with a four-layer core of different layers arrangements were constructed. Cylindrical steel projectiles with hemispherical nose, 8 mm diameter and 20 mm length were used. The projectile impact velocity range was chosen from 180 to 320 m/s. Considering constant mass and total thickness for the core, the results of the study showed that the core layering increases the ballistic limit velocity of the sandwich structures. The ballistic limit velocity of the panels with a four-layer core of different arrangements, compared to the panel with the single-layer core, is higher from 5% to 8%. Also, for the single-layer core structure, by increasing the core density, the ballistic limit velocity was increased. Different failure mechanisms such as plugging, petaling and dishing occurred for the back face-sheet. The dishing area diameter of back face-sheets was proportional to the ballistic resistance of each sandwich structure.
Ballistic limit
Layering
Sandwich panel
Aluminium foam sandwich
Honeycomb structure
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The objective of this research was to use a three-dimensional (3D) analysis method to evaluate "system effects" in light-frame roof truss assemblies. The goal of this study was to develop an improved and practical design method for 3D roof truss assemblies used in residential construction. A truss plate manufacturer (TPM) design software was used to lay out assemblies and to design individual trusses. The TPM software used a conventional design procedure (CDP) by analyzing one truss at a time in two dimensions. A commercially available structural analysis program was utilized to model and analyze 3D truss assemblies as a system. This system design procedure (SDP) is being proposed as a tool to analyze and design 3D roof truss assemblies. Three truss assemblies, L shape, T shape, and a complex assembly, were analyzed. The structural responses including combined stress index (CSI), truss deflections, and reactions from both CDP and SDP were compared and the system effects were evaluated. From this investigation, it is concluded that there are three system effects observed by the SDP, but not accounted for by CDP. These are: reduced applied load effect, truss-to-truss support effect, and stiff truss effect. Based on this investigation, the maximum CSI for most trusses in all three assemblies reduced by 6–60% because of system effects. SDP can help to improve the design of truss assemblies by directly including system effects that are not accounted for by the CDP.
Structural system
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As a new material suitable for the primary mirror of space telescopes, we focused on foam core CFRP sandwich panels which satisfy lower surface roughness than the conventional honeycomb core sandwich panels. However, large deformations appeared at edge of the ROHACELL (polymethacrylimide based foam) core sandwich panels surface. In order to improve the surface accuracy, we analytically investigated the influence of core thickness and of using the GRAFOAM core (carbon-based foam) having a low coefficient of thermal expansion. Then, ROHACELL core sandwich panels with two different core thickness and GRAFOAM core sandwich panels were manufactured and the surface accuracy of those panels were experimentally measured. Analytical and experimental results showed that edge effect decreased on ROHACELL core sandwich panels with thinner core thickness, and that the edge effect was suppressed by using the GRAFOAM core. In addition, because of lower CME(coefficient of moisture expansion), deformation due to moisture absorption is small.
Honeycomb structure
Honeycomb
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The safety of truss is determined by dynamic response of truss during the engineering application. Truss number is an important parameter for the engineering application of truss, which is related with the economy and convenience. The effect of truss number on the dynamic response of truss can be analyzed by means of commercial finite element software. Here, a finite element model (FEM) was employed to simulate the dynamic response of truss structure. By using the proposed FEM, the effects of truss number on the maximum displacement and Mises stress were researched. Based on the numerical results, the dynamic responses are different from each other for different truss numbers. The maximum displacement and Mises stress increase with the increasing truss number; however, the maximum displacement and Mises stress keep on a stable value when truss number is more than a certain number.
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The present paper tries to introduce the effect of foam-filled on a type of trapezoidal corrugated core and their structures derived from the related previous studies. The main purpose of this work is to present a novel geometry of trapezoidal cores, and their configurations are inspired by the earlier works. These absorbers have been proposed to raise the specific energy absorption (SEA) while declining the initial peak crushing force. Therefore, five corrugated core sandwich panels have been tested under quasi-static axial compressive load experimentally and then simulated by ABAQUS software. The accuracy of the numerical simulations is validated by comparing the numerical results with the corresponding experimental data. Besides, some other simulations have been carried out to investigate the effect of foam density, core type, and thickness in more detail. The comparison results show that the SEA rate of bi-core sandwich panels which has not been filled by foam is better than the single trapezoidal core sandwich panels, and this rate is roughly around 70%. The best performance is relevant to the pure foam core without any trapezoidal core structure and the next item is the single foam-filled corrugated core and the lowest performance among them is related to the bi-core corrugated core foam-filled.
Sandwich panel
Foam concrete
Aluminium foam sandwich
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