• Advances in aircraft and spacecraft science
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• v.9 no.5
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• pp.377-400
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• 2022

The aim of this work is a numerical comparison (FEM) between lattice pyramidal-core panel and honeycomb core panel for different core thicknesses. By evaluating the mid-span deflection, the shear rigidity and the shear modulus for both core types and different core thicknesses, it is possible to define which core type has got the best mechanical behaviour for each thickness and the evolution of that behaviour as far as the thickness increases. Since a specific base geometry has been used for the lattice pyramidal core, the comparison gives us the opportunity to investigate the unit cell strut angle giving the higher mechanical properties. The presented work considers a detailed FEM modelling of a standard 3-point bending test (ASTM C393/C393M Standard Practice). Detailed FEM modelling addresses to detailed discretization of cores by means of beam elements for lattice core and shell elements for honeycomb core. Facings, instead, have been modelled by using shell elements for both sandwich panels. On lattice core structure, elements of core and facings are directly connected, to better simulate the additive manufacturing process. Otherwise, an MPC-based constraint between facings and core has been used for honeycomb core structure. Both sandwich panels are entirely built of Aluminium alloy. Prior to compare the two models, the FEM sandwich panel model with lattice pyramidal core needs to be validated with 3-point bending test experimental results, in order to ensure a good reliability of the FEM approach and of the comparison. Furthermore, the analytical validation has been performed according to Allen's theory. The FEM analysis is linear static with an increasing midspan load ranging from 50N up to 500N.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.1-4
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• 2004

In this paper we developed Composite-Smart-Structures(CSS) using sandwich structure composed of Glass/Epoxy laminates and Nomex honeycomb and microstrip antenna. Transmission/reflection theory shows that antenna performances can be improved due to multiple reflection by Glass/Epoxy facesheet, and honeycomb is used for air gap between antenna and facesheet. Stacked radiating patches are used for the wideband. Facesheet and honeycomb thicknesses are selected considering both wideband and high gain. Measured electrical performances show that CSS has wide bandwidth over $10\%$ and higher gain by 3.5dBi than initially designed antenna, and no doubt it has excellent mechanical performances by sandwich effect given by composite laminates and honeycomb core. The CSS concept can be extended to give a useful guide for manufacturers of structural body panels as well as antenna designers, promising innovative future communication technology.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.238-243
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• 2004

A new sandwich composite was investigated in this paper. The honeycomb core of this composite was filled with viscoelastic material in order to obtain an improved damping performance. The viscoelastic fillings in the honeycomb cells was hoped to act as dampers and provide the function of energy dissipation in this combined material system. Dynamic test was set up to the specimens with various stacked carbon/epoxy laminate facesheets, $[0/90]_{4s}$, $[0/45/-45/90]_{2s}$, $[45/-45]_{4s}$. Frequency response, displacement response and damping ratio were checked and compared for the both groups of specimens, with and without rubber fillings. The experimental results provided a good agreement with our material design concept.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.284-291
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• 1997

Many papers have been conducted on the applications of honeycomb sandwich maintenance, and to improve the high speed and light weight in rolling stocks, aircrafts and so on. The end door of rolling stock is generally made of rolled steel or stainless steel. Thus, the weight of these materials are heavier than of nonferrous metals and thermal deformation by welding or complexity of manufacturing process is occurred. Therefore, this paper is aimed to develop the light weight by application of end door which is made of aluminum honeycomb sandwich panels in rolling stocks and to propose the standards of design and evaluation for its adhesively bonded strength.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.83-87
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• 2002

Aerospace industries are widely using honeycomb sandwich structures that it has high specific strength and stiffness, chemical material resistance and fatigue resistance. But, in repairing process of damaged areas, one of the problems is that delamination can be occurred in the sound areas during and/or after the exposure to the elevated curing temperature in case that the repair process is repeated. Therefore, this study was conducted Flatwise tensile, Drum peel and Long beam flexural strength tests to evaluate the degree of degradation of mechanical properties of the honeycomb sandwich structures by affecting thermal aging. As the results, the decrease of mechanical strength was observed at the specific specimen which is exposed over 50hrs at $127^{\circ}C$.

• Steel and Composite Structures
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• v.46 no.5
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• pp.659-667
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• 2023

Nonlinear forced vibration behaviors of sandwich plates having graphene platelets (GPL) based face sheets have been researched in this article. Possessing low weight together with low stiffness, square honeycomb cores are mostly constructed by aluminum. Herein, the square shaped core has been fortified by two skins of GPL-based type in such a way that the skins have uniform and linearly graded GPL dispersions. The square shaped core has the effective material specification according to the relative density concept. The whole formulation has been represented based upon classical plate theory (CPT) while harmonic balance approach is applied for solving the problem and plotting the amplitude-frequency curves. The forced vibration behaviors of such plates are influenced by square-shaped core and the relative density, skin's height and GPL fortification.

• Journal of the Korean Society for Railway
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• v.13 no.1
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• pp.31-36
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• 2010

The objective of this study is to evaluate effects of honeycomb cell size for compressive behaviors of square sandwich composite tubes with woven fabric carbon/epoxy skin and Al honeycomb core. In order to achieve these goals, four different kinds of tubes were fabricated and compressed to 200mm~250mm under quasi-static load of 10mm/min. The Al honeycombs with cell size of 6.35mm and 9.53mm were used. The relationship of mean compressive load and cell size was evaluated. In addition, the effect of peel strength and equivalent elastic modulus in ribbon direction for the mean compressive load was investigated.

• Composites Research
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• v.26 no.2
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• pp.116-122
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• 2013

In this study, impact behavior of aluminium and glass-fiber structure is studied under low impact velocity. Compression test is carried out to investigate the compressive strength of the specimens. The degree of damage is observed using microscopy and compared with the experimental analysis data. The maximum load capacity, impact strength and elastic energy of glass-fiber honeycomb sandwich panel are more than the aluminium honeycomb sandwich panel.

• Composites Research
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• v.26 no.2
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• pp.85-90
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• 2013

This paper presents the fabrication and 3-point flexion testing of carbon fiber reinforced polymer (CFRP) composite face/aluminum honeycomb core sandwich panels. Specimen sandwich panels were fabricated with three honeycomb types (3.18 mm, 4.76 mm, and 6.35 mm cell size) and three panel radii (flat, r = 1.6 m, r = 1.3 m). The curved sandwiches were fabricated normally with the core in the W-direction. The tensile mechanical properties of the CFRP $2{\times}2$ twill fabric face laminate were evaluated (modulus, strength, Poisson's ratio). The measured values are comparable to other CFRP fabric laminates. The flat sandwich 3-point flexion test core shear strength results were 11-30% lower than the manufacturer published data; the test set-up used may be the cause. With a limited sample size, the 1.3 meter panel curvature appeared to cause a 0.8-3.8% reduction in ultimate core shear strength compared to a flat panel.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.106-123
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• 1996

This paper experimentally investigates the characteristics of Al-honeycomb sandwich panels which are considered as a promising primary strength member of weight critical large structures. Some tests on the aluminum honeycomb panels subject to 3-point bending or uniaxial compression or crushing load are carried out. Based on the test results, linear elastic response, buckling/ultimate strength and crushing/energy absorption capacity are discussed. Some guidelines for design of aluminum honeycomb panels are given.