Effect of Cell Geometry on the Shear Modulus and on Density of Sandwich Panel Cores

1961 ◽  
Vol 83 (4) ◽  
pp. 513-517 ◽  
Author(s):  
Chieh C. Chang ◽  
Ibrahim K. Ebcioglu
Keyword(s):  
Aspect Ratio ◽  
Shear Modulus ◽  
Sandwich Panel ◽  
Analytic Theory ◽  
Cell Geometry ◽  
Cell Weight ◽  
The Core ◽  
Special Cases ◽  
Square Cells ◽  
Sandwich Core

A simple analytic theory for the effect of cell geometry on both the shear modulus and the density of sandwich panel core is presented. The core shear modulus in different directions is analyzed to include the effects of the angle α and the aspect ratio b/a of the cell. It is also found that the minimum cell weight of the sandwich core depends both on the cell angle α and the cell aspect ratio b/a. The theory compares fairly well with some available experiments. The cell geometry chosen is so general that the regular hexagonal and square cells of commercial sandwich cores are special cases.

scholarly journals Transverse fastening reinforcement of sandwich panels with upcycled bottle caps core

2020 ◽  
pp. 002199832096052
Author(s):  
PR Oliveira ◽  
LJ da Silva ◽  
TH Panzera ◽  
GG del Pino ◽  
F Scarpa
Keyword(s):  
Shear Modulus ◽  
Mechanical Strength ◽  
Sandwich Panel ◽  
Sandwich Panels ◽  
Transverse Reinforcement ◽  
Moderate Increase ◽  
Remarkable Improvement ◽  
The Core ◽  
Panel Stiffness ◽  
Strength And Stiffness

This work describes the use of transverse reinforcement in eco-friendly sandwich panels made from aluminium skins and a core of upcycled bottle caps. The Design of Experiments technique identifies the effect of the position of the metal rivets on the panel. The results show a moderate increase in strength and a significant enhancement of the sandwich panel stiffness when the rivets are placed on the upper skin, with a remarkable improvement in terms of the core shear modulus. The use of metal rivets has also increased the specific mechanical strength and stiffness of the panels, which highlights the effectiveness of the transverse reinforcement in bottle caps panels.

Computing Cores for Existential Rules with the Standard Chase and ASP

2020 ◽  
Author(s):  
Markus Krötzsch
Keyword(s):  
Large Class ◽  
Data Exchange ◽  
Answer Set Programming ◽  
Query Answering ◽  
Universal Model ◽  
The Core ◽  
Universal Models ◽  
General Terms ◽  
Special Cases ◽  
The Many

To reason with existential rules (a.k.a. tuple-generating dependencies), one often computes universal models. Among the many such models of different structure and cardinality, the core is arguably the “best”. Especially for finitely satisfiable theories, where the core is the unique smallest universal model, it has advantages in query answering, non-monotonic reasoning, and data exchange. Unfortunately, computing cores is difficult and not supported by most reasoners. We therefore propose ways of computing cores using practically implemented methods from rule reasoning and answer set programming. Our focus is on cases where the standard chase algorithm produces a core. We characterise this desirable situation in general terms that apply to a large class of cores, derive concrete approaches for decidable special cases, and generalise these approaches to non-monotonic extensions of existential rules.

scholarly journals A numerical study of the impact perforation of sandwich panels with graded hollow sphere cores

2021 ◽  
Vol 13 (4) ◽  
pp. 168781402110094
Author(s):  
Ibrahim Elnasri ◽  
Han Zhao
Keyword(s):  
Boundary Conditions ◽  
Hollow Sphere ◽  
Sandwich Panel ◽  
Numerical Study ◽  
Sandwich Panels ◽  
Hopkinson Bar ◽  
Core Density ◽  
The Core ◽  
The Impact ◽  
Force Displacement

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.

ON TWO THEOREMS OF QUINZII AND RENT CONTROLLED HOUSING ALLOCATION IN SWEDEN

2007 ◽  
Vol 09 (03) ◽  
pp. 515-525
Author(s):  
KIMMO ERIKSSON ◽  
JONAS SJÖSTRAND
Keyword(s):  
Control System ◽  
Empirical Data ◽  
General Theorem ◽  
Black Market ◽  
Utility Functions ◽  
Rent Control ◽  
Black And White ◽  
The Core ◽  
Special Cases ◽  
Housing Allocation

The Swedish rent control system creates a white market for swapping rental contracts and a black market for selling rental contracts. Empirical data suggests that in this black-and-white market some people act according to utility functions that are both discontinuous and locally decreasing in money. We discuss Quinzii's theorem for the nonemptiness of the core of generalized house-swapping games, and show how it can be extended to cover the Swedish game. In a second part, we show how this theorem of Quinzii and her second theorem on nonemptiness of the core in two-sided models are both special cases of a more general theorem.

scholarly journals Swirling Flows Characteristics in a Cylinder Under Effect of Buoyancy

Mechanika ◽  
2021 ◽  
Vol 27 (3) ◽  
pp. 201-208
Author(s):  
Mustafa FEKHAR ◽  
Rachid SACI ◽  
Renée GATIGNOL
Keyword(s):  
Aspect Ratio ◽  
Thermal Stratification ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Swirling Flows ◽  
Viscous Effects ◽  
Thermal Buoyancy ◽  
State Diagrams ◽  
The Core ◽  
Flow Stagnation

Thermal buoyancy, induced by injection or by differential heating of a tiny rod is explored to control breakdown in the core of a helical flow driven by the lid rotation of a cylinder. Three main parameters are required to characterize numerically the flow behavior; namely, the rotational Reynolds number Re, the cavity aspect ratio and the Richardson number Ri. Warm injection/rod, Ri > 0, is shown to prevent on-axis flow stagnation while breakdown enhancement is evidenced when Ri < 0. Results revealed that a bubble vortex evolves into a ring type structure which may remain robust, as observed in prior related experiments or, in contrast, disappear over a given range of parameters (Λh, Re, Ri > 0). Besides, the emergence of such a toroidal mode was not found to occur under thermal stratification induced by a differentially heated rod. Moreover, three state diagrams were established which provide detailed flow characteristics under the distinct and combined effects of buoyancy strength, viscous effects and cavity aspect ratio.

scholarly journals Probability of infectious disease in humans during epidemic

2021 ◽  
Author(s):  
AM Karmishin ◽  
IV Borisevich ◽  
VI Skvortsova ◽  
AA Goryaev ◽  
SM Yudin
Keyword(s):  
Infectious Disease ◽  
Biological Object ◽  
Epidemiological Modeling ◽  
Pathogen Virulence ◽  
The Core ◽  
Special Cases ◽  
Quantitative Characteristics ◽  
Infective Dose ◽  
The Law ◽  
Generalized Time

Popular SIR models and their modifications used to generate predictions about epidemics and, specifically, the COVID-19 pandemic, are inadequate. The aim of this study was to find the laws describing the probability of infection in a biological object. Using theoretical methods of research based on the probability theory, we constructed the laws describing the probability of infection in a human depending on the infective dose and considering the temporal characteristics of a given infection. The so-called generalized time-factor law, which factors in the time of onset and the duration of an infectious disease, was found to be the most general. Among its special cases are the law describing the probability of infection developing by some point in time t, depending on the infective dose, and the law that does not factor in the time of onset. The study produced a full list of quantitative characteristics of pathogen virulence. The laws described in the study help to solve practical tasks and should lie at the core of mathematical epidemiological modeling.

Study on Sandwich Core Modeling for Structural Analysis of Sandwich Composite Structure

2018 ◽  
Vol 926 ◽  
pp. 57-63
Author(s):  
Hyun Bum Park
Keyword(s):  
Structural Analysis ◽  
Composite Structure ◽  
Solid Modeling ◽  
Modeling Method ◽  
Core Structure ◽  
Sandwich Composite ◽  
Damage Area ◽  
The Core ◽  
Sandwich Core ◽  
Sandwich Composite Structure

This study aims to investigate numerically the damage area of a sandwich composite structure. In this work, the optimal sandwich core modeling method was proposed. This study applied two modeling methods to compare their analysis results for the structural analysis of the sandwich composite structure. Firstly, the modeling of sandwich core structure was performed with laminate modeling method. Secondly, the modeling of core structure was performed with core solid modeling method. The laminate modeling method was compared with the core solid modeling method. For the modeling, a carbon/epoxy composite structure was applied to the face sheet. And a nomex honeycomb core was applied to the core. Finally, comparing the result of modeling as actual shape with the one of virtually applying the thickness and modeling, it was examined that the former had three times more stress than the latter.

scholarly journals Conceptual Design of Composite Sandwich Structure Submarine Radome

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1966 ◽  
Author(s):  
Waqas ◽  
Shi ◽  
Imran ◽  
Khan ◽  
Tong ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Composite Materials ◽  
Conceptual Design ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Element Analysis ◽  
The Core ◽  
Reinforced Polymer ◽  
Sandwich Core

Radomes are usually constructed from sandwich structures made of materials which usually have a low dielectric constant so that they do not interfere with electromagnetic waves. Performance of the antenna is increased by the appropriate assortment of materials enabling it to survive under marine applications, and it depends on composite strength-to-weight ratio, stiffness, and resistance to corrosion. The design of a sandwich core submarine radome greatly depends on the material system, number of layers, orientation angles, and thickness of the core material. In this paper, a conceptual design study for a sandwich core submarine radome is carried out with the help of finite element analysis (FEA) using two unidirectional composite materials—glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP)—as a skin material and six different core materials. Conceptual designs are obtained based on constraints on the composite materials’ failure, buckling, and strength. The thickness of the core is reduced under constraints on material and buckling strength. Finite element analysis software ANSYS WORKBENCH is used to carry out all the simulations.

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