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1

Mathematical model of modified classical lamination theory for foam core sandwich composites

Kumar S.J. Amith, Kumar Ajith S.J.

Composites Theory and Practice

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2023

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R. 23, nr 4

220--225

EN

Elastic properties are important quantities in the modelling and analysis of sandwich composite structures. The stability of sandwich composites mainly depends on their elastic properties, which in turn depend on the elastic properties of its constituents namely, the core and face skin. Several models have been proposed to predict the elastic constants of core materials such as honeycomb and foam. A foam core may be open-cell foam or closed-cell foam. The present work is focused on the hexagonal cells of a honeycomb grid core and closed-cell polymer syntactic foam core. The honeycomb is considered to be orthotropic with nine independent elastic properties. However, the overall structural performance of the honeycomb core is mainly influenced only by out-of-plane elastic properties. On the other hand, the syntactic foam is considered to beisotropic with two independent elastic constants namely, the modulus of elasticity and Poisson’s ratio. The face skin material may be isotropic with two independent elastic constants or orthotropic with nine elastic constants under three-dimensional loading. The present work is focused on predicting the elastic properties of a honeycomb core, syntactic foam and a glass/epoxy composite using existing theoretical models. Thereafter, the elastic properties of the syntactic foam and glass/epoxy composite are later used to establish the elastic constants for syntactic foam core sandwich composites using modified classical lamination theory (MCLT). The results reveal that the reviewed theoretical models for the honeycomb core, syntactic foam, fiber-reinforced polymeric (FRP) glass/epoxy face skins and sandwich composites are validated by the experimental results.

2

Investigating the effect of honeycomb grid cell size on structural performance of stiffened syntactic foam core sandwich composite

Kumar Amith S.J., Kumar Ajith S.J.

Composites Theory and Practice

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2023

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R. 23, nr 4

202--208

EN

Syntactic foam core composite sandwich structures are potential structural panels because of their high specific properties. The chief ingredient of a syntactic foam is dry fly ash cenospheres, which play a vital role in the mechanical properties of syntactic foam in relation to its volume fraction. In the present investigation, the concept of confining foam in the cells of a honeycomb grid structure was adopted to improve the mechanical properties of composite sandwich structural panels. Experimental investigations were carried out to evaluate the thermal stability and mechanical properties of a honeycomb grid stiffened syntactic foam core composite sandwich as per ASTM standards. The results of the investigations reveal that the syntactic foam confined in the hexagonal cells of the honeycomb grid structure considerably improves the mechanical properties by 20% to 180% than compared with syntactic foam core sandwich composites without a honeycomb grid structure. The cell walls of the honeycomb grid structure hinder the propagation of cracks under loading conditions. The damage tolerance capacity is attributed to the cell size of the honeycomb structure. Interfacial bonding of the constituent materials leads to improved mechanical properties.

3

Effect of Zeolite Addition on the Production of a Cast Porous Composite Based on AC-AlSi11 Silumin

Borowiecka-Jamrożek Joanna, Kargul Marcin

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 4

96--101

EN

The paper presents the application of the casting method for the production of porous composites, called syntactic foams, of the casting alloy - solid particles type. This method was used to produce composites based on Al alloys reinforced with particles of clinoptilolite, a natural mineral from the zeolite group. Before the casting process, tests were carried out on the morphology, physicochemical properties and chemical composition of the zeolite, which was obtained from a rock called zeolite tuff, mined in a quarry in Kucin, (VSK PRO-ZEO s.r.o., Slovakia). Observations of the microstructure of the produced composites were also carried out using a scanning electron microscope. Diffractometric tests of zeolite rock as delivered for research and of the produced samples reinforced with zeolite particles were also carried out. Initial studies of the density and porosity of the produced composites were performed. The usefulness of the presented method of composite production was assessed on the basis of the conducted structural tests, with particular emphasis on the particle distribution in the alloy matrix.

4

Fabrication Optimization of Al 7075/Expanded Glass Syntactic Foam by Cold Chamber Die Casting

Bolat C., Goksenli A.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 3

112--118

EN

Recently, aluminum matrix syntactic foams (AMSFs) have become notably attractive for many different industrial areas like automotive, aerospace, construction and defense. Owing to their low density, good compression response and perfect energy absorption capacity, these advanced composite materials are also considered as strong alternatives to traditional particle reinforced composites and metal foams. This paper presents a promising probability of AMSF fabrication by means of industrial cold chamber die casting method. In this investigation, contrary to other literature studies restricted in laboratory scale, fully equipped custom-build cold chamber die casting machine was used first time and all fabrication steps were designed just as carried out in the real industrial high pressure casting applications. Main casting parameters (casting temperature, injection pressure, piston speed, filler pre-temperature and piston waiting time) were optimized in order to obtain flawless AMSF samples. The density alterations of the syntactic foams were analyzed depending upon increasing process values of injection pressure, piston speed and piston waiting time. In addition, macroscopic and microscopic investigations were performed to comprehend physical properties of fabricated foams. All these efforts showed almost perfect infiltration between filler particles at the optimized injection parameters.

5

High porosity fly ash/Ni/P composite produced by electroless deposition

Yanachkov B., Drenchev L., Lyutov L.

Prace Instytutu Odlewnictwa

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2017

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Vol. 57, no. 4

369--373

EN

The aim of the present study is to create a composite material possessing useful properties enabling the waste fly ash to be utilized. To obtain the final material, fly ash is subjected to separation by size and density. The innovative approach to making the composite material is the use of chemical nickel deposition by which the free particles are bonded as a solid body. Deposition of nickel was carried out by two stages: first Ni-coating of the particles and second – bonding of the particles by nickel deposition. Structure of this material is near to syntactic foam. Some properties of the obtained material as a porosity, density, and permeability with regard to its application have been investigated.

6

Flexural Properties of Syntactic foam Reinforced by Warp Knitted Spacer Fabric

Zhi C., Long H.

Autex Research Journal

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2016

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Vol. 16, no. 2

57--66

EN

The aim of this study was to investigate the flexural behaviours of syntactic foam reinforced by warp knitted spacer fabric (SF-WKSF). Seven kinds of SF-WKSF samples were fabricated by warp knitted spacer fabric (WKSF) with structural parameters including surface layer structures, inclination-angle and fineness of spacer yarns, different microballoons types and contents. The flexural tests were carried out and the bending properties of SF-WKSF were analysed based on the strength and modulus values obtained from the test results. It is indicated that the SF-WKSF shows higher flexural strength and modulus compared to neat syntactic foam with almost no impact on the density of composites. The results also demonstrate that the surface layer structure, inclination-angle of spacer yarns, microballons content and type have significant effects on the flexural responses of SF-WKSF. The composites exhibit better antibending capacities by selecting larger inclination-angle, closer surface layer structure, higher density and relatively higher content of S60HS microballoons.

7

Materiały wysokoporowate - metody wytwarzania i zastosowanie

Darłak P., Dudek P.

Odlewnictwo - Nauka i Praktyka

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2004

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R. 6, nr 1

3-17

PL

Autorzy, stawiając sobie za cel przybliżenie tematyki z zakresu materiałów porowatych, zwrócili szczególną uwagę na analizę wszystkich dostępnych informacji, opisujących metody ich wytwarzania, również w aspekcie zachodzącej ewolucji na przełomie kilkudziesięciu ostatnich lat. Biorąc pod uwagę fakt, że w Polsce znajomość zagadnień wytwarzania pian metalowych nie jest szeroko spopularyzowana, znaczna część artykułu poświęcona jest próbie scharakteryzowania znanych technik wytwarzania, jak również technologii od niedawna stosowanych, znajdujących się w fazie badań, tj. gazarów i pian syntaktycznych. W artykule zamieszczono szereg fotografii przedstawiających charakterystyki, budowę oraz zastosowanie materiałów komórkowych w konkretnych przykładach. Materiały wysokoporowate, z powodu swoich unikalnych właściwości fizycznych, głównie bardzo malej gęstości, zdolności do tłumienia energii mechanicznej oraz pochłaniania fal dźwiękowych, znalazły szerokie spektrum zastosowań. Ich odmienna budowa strukturalna idealnie predysponuje te materiały do zastosowania w przemyśle samochodowym, lotniczym i kosmicznym, otwierając tym samym olbrzymie rynki zbytu, stąd może wynikać zauważalnie wzrastające zainteresowanie materiałami o obniżonej gęstości.

EN

The authors presented many aspects of scope of manufacturing high porous materials. Therefore, a lat of information regarding metallic foams in various aspects, describing the production in the last century, has been collected. Taking into consideration that in Poland the knowledge concerning the metal foams is not widely highlighted, the significant part of publication describes existing commercial methods as well as methods being under investigation, namely: gasars and syntactic foams. In each chapter examples of characteristic structure as well as application of high porosity materials have been given. The porous materials, due to their unique physical properties, such as ultra-low density, ability to annihilate mechanical energy as well as sound wave, have found a wide spectrum of application. This fact stimulates their using in automotive, aircraft and space industries.