Malaysian Journal of Civil Engineering 22(2) : (2010) Skudai, Johor, Malaysia. *Corresponding Author:

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1 A STUDY ON FLXURAL MODULUS AND DUCTILITY OF LAMINATD CMNTITIOUS COMPOSITS M. Zakaria Hossain 1, A.S.M. Aul Awal 2* 1 Grauate Shool of Bioresoures, Mie University, Japan 2 Faulty of Civil ngineering, Universiti Teknologi Malaysia 8110 Skuai, Johor, Malaysia *Corresponing Author: asmawal@yahoo.om Astrat: This paper presents a new approah for flexural moulus of laminate omposites erive from the analysis of a flexural-setion ompose of several utile an rittle layers of ifferent mouli. The erivation is ase on the assumption that the tension an ompression zones of the laminate omposite are symmetrial with respet to the neutral axis an thus, half of the setion is neee to analyze for omplete erivation of flexural moulus of the whole setion. This ompose of two utile layers of higher mouli proviing in oth tension an ompression zones to maintain the equilirium onitions uring flexure. The formulation shows that the flexural moulus of the entire setion of laminate omposites otaine y this metho is equal to the moulus of utile layers plus a fator of the ifferene of moulus of utile an rittle layers. It is onlue that this fator is ifferent from the usual one whih is otaine uner uniaxial loaings. Despite the fragile nature of rittle layers of the omposite, it has een foun that the inlusion of two utile layers into the laminate ementitious omposites makes it fully utile material owing to the synergeti ation etween the layers of two omponents. Keywors: Laminate ementitious omposites, wire mesh, flexural moulus, an utility. 1.0 Introution The history of man-mae omposite materials ates ak to anient Chinese (Rosato, 1968), gyptians an Israelites (Ruin, 1969), all of whom emee straw in riks to improve their strutural apailities. With the avent of fine iameter elastoplasti mesh reinforement in numerous ement matries, the new era of laminate ementitious omposite is orn. The evelopment of laminate ementitious omposite is a signifiant step in this iretion, wherein onsierale saving in onsumption of ement an steel has een reporte as ompare to reinfore ement onrete (Hossain an Inoue, 2001). Laminate omposite materials are ompose of two or more materials joine together forming a new meium with properties superior to those of its

These materials an e lassifie as ontinuous an orthotropi laminate omposites, the most ommonly use reinfore meshes are aron/steel an polypropylene.

2 217 iniviual omponents. Often, the term laminate omposite is use for meshreinfore ementitious omposites, although ifferent mesh layers exist. Meshreinfore omposites (laminates) onsist of several uniiretional layers arrange at the same or ifferent angles an, therefore, present anisotropi properties. These materials an e lassifie as ontinuous an orthotropi laminate omposites, the most ommonly use reinfore meshes are aron/steel an polypropylene. A typial laminate ementitious omposite is illustrate in Figure 1. The use of omposite materials is onstantly inreasing in moern onstrution eause of low-ost, low-weight an high performane in terms of oth utile an rak arresting properties. Laminate ementitious omposite materials an offer superior performane over stanar onrete materials inluing higher strength-to-weight ratios, stiffness an rak resistane. Pratially laminate ementitious omposites require little or no maintenane as ompare to metal strutures. Owing to the improve harateristis, the appliation of these materials has een growing rapily uring the past eaes in a wie variety of fiels like housing, agriulture, geotehnial an other strutural appliations. It is important to unerstan the funamental properties of laminate ementitious omposites, suh as, flexural moulus in orer to otain reliale esign an onstrution for fiel appliations. During the last ouple of eaes, a. Physial appearane of a ement omposite. Cross-setion showing wire meshes in mortar matrix Figure 1: A laminate ementitious omposite

3 218 numerous works have een arrie out on mehanial properties of laminate ementitious omposites (Koayashi et al., 1992; Ghavami et al., 1999; Naaman, 2000; Hossain an Inoue, 2001). However, very little is known on flexural moulus although it presents a onsierale versatility towars the reliale esign of strutures. The aim of this researh is to onut oth analytial an experimental investigation to stuy flexural moulus an utility properties of a laminate ementitious omposite. Along with investigation, an analytial equation is also evelope an presente to etermine the relationship etween the utility an flexural moulus. 2.0 Materials an Methos Various types of wire an geogri mashes are availale for the onstrution of laminate omposite struture. The mehanial properties of mesh an mortar otaine experimentally are given in Tale 1. To stuy the utility harateristis of laminate omposite struture, tests were arrie out on speimens (two in eah group) having heating an uring yles. For etter omparison, speimens with same yles in natural rying an uring were also use without heating. For the heating group, eah yle was of 48 hours uration onsisting 24 hours of heating in oven with onstant temperature of 110 o C an 24 hours of wetting in fresh water. In another group, here alle air rying in room temperature, eah yle was of 48 hours uration onsisting 24 hours air rying in room temperature at 15 o C an 24 hours of wetting in fresh water. Tale 1: Mehanial properties of wire mesh, geogri mesh an mortar Wire mesh Geogri Mortar Diameter (mm) 1.00 C/ spaing (mm) Young's moulus (KN/mm 2 ) Poisson's ratio 0.28 Cross-setion of strans in longituinal iretion (mm) 1x5 C/ spaing in longituinal iretion (mm) Diameter of strans in transverse iretion (mm) 1.0 x C/ spaing in transverse iretion (mm) Young's moulus (KN/mm 2 ) Poisson's ratio 0.40 Compressive strength (N/mm 2 ) Young's moulus (KN/mm 2 ) Poisson's ratio 0.19

4 219 The numer of mesh layers selete for this investigation were two (1 top an 1 ottom) for all speimens with square steel mesh an geogri mesh. The size of the speimen was mm with loaing span of 60mm. Defletion was measure at the entre of the speimens teste uner thir point loaing onition, shown in Figure 2. 60mm Dial gauge 120mm 120mm Speimen Figure 2: Speifiation for the test setup.0 Analytial Investigation: Flexural Moulus P Figure illustrates a laminate ementitious omposite of thikness t sujete to flexural loaings where y 0 an Δy are the rittle (mortar) an utile (mesh) portions, respetively. Here, an are stresses evelope in rittle an utile layers, respetively, an y is the istane from the neutral axis to the area A. The A an e expresse as wy where w is the with of the flexural setion an y is the height of strip taken in the rittle an utile portion. It an e given that the eformation ( x ) of any layer having original length x at any istane y from the neutral axis to e varie proportionally with the variation of the istane from the neutral axis (y). Therefore, the equation of strain ( ) in any layer an e erive as follows: x. y (1) x Where, is the proportional onstant. By using the Hook s law for any layer, equation 1 an also e written as follows:

5 220 (2) This is to note that the strains ourre in the rittle ( ) an utile ( ) layers ue to the efletion of eam are equal eause of their relative hanges with respet to neutral axis, i.e.. Beam Setion of length, x Stress Strain Brittle (, ) (+) y (+) t Dutile (, ) x Brittle (, ) Neutral axis x y y o t/2 Brittle (, ) Dutile (, ) t/2 Brittle (, ) (-) (-) Stress Strain Figure : A laminate omposite setion with stress-strain iagram However, the stress evelope in rittle ( ) an utile ( ) layers is varie epening on the rigiity of the layers, i.e.. By applying the onition of equilirium in a setion of a laminate ementitious omposite onsisting of several utile (mesh) an rittle (mortar) layers, the following equation of alane may e formulate. M y0 y0 y t / 2 2 y A y A y A () 0 y0 y0 y By sustituting the values of an from equations 1 an 2 into equation, the following equation an e otaine. y 0 y0 y t / M 2w y y y y y y (4) 0 y 0 y0 y

6 221 Where, an are the mouli of elastiity of rittle (mortar) an utile (mesh) layers, respetively. Integration of equation 4, gives: M y t 2w {( y0 y) y0} { ( y0 y) (5) 8 The utile layer Δy an e written as the part of the omposite iniating y α t whih is expresse as y for half of the thikness of the omposite ue to 2 symmetry. Similarly, the rittle layer y 0 an e written as the part of the t t omposite iniating y β whih is expresse as y0 (1 ) for half of 2 2 the thikness of the omposite ue to symmetry. Sustituting the values of Δy an y 0 into equation 5, the following equation an e otaine. M wt 12 ( 2 wt 2 wt wt ) ( ) ( ) (6) wt It is known that the term of equation 6 is the moment of inertia of the 12 omposite flexural setion with respet to neutral axis whih an e iniate as wt I i.e. I. Therefore, equation 6 an e written in terms of moment of 12 inertia as follows: I 2 2 M ( )( ) (7) Comining equations 2 an 7, it takes the following form: M y 2 2 ( )( (8) ) I quation 8 is the general equation for expressing the strain in any point of a laminate omposite setion ue to the ening moment M, where the term 2 2 ( )( ) iniates the flexural moulus of the whole setion ompose of rittle an utile layers, iniate as. Hene, equation 8 an e written as:

222 M y (9) I Where, 2 2 ( )( ) (10) The synergy etween the rittle an utile material is evient from equation 10 iniating that the flexural moulus of laminate matrix epens on the thir orer of utile

7 222 M y (9) I Where, 2 2 ( )( ) (10) The synergy etween the rittle an utile material is evient from equation 10 iniating that the flexural moulus of laminate matrix epens on the thir orer of utile material. This means that the utile material may play a signifiant role on the rittle matrix whih nees to e sustantiate through laoratory experiment. 4.0 xperimental Investigations: Dutility uner Flexural Loaings The utility ehavior of a laminate ementitious omposite is illustrate in Figure 4. It an e seen that the laminate ementitious omposite ehaves like utile material espite the 90% of the onstituents is of rittle nature. This iniates the effet of the fator epite in equation 10 whih is the thir orer of the utile layer. This means laminate ementitious omposites uner flexural loaings ehaves like a plasti flexile material whih an withstan any loa without suen failure. Inee, this will e of great enefit for safe an reliale esign of strutures. Figure 4: Dutility of the laminate ement omposite The utility properties of some ement omposites ontaining steel wire mesh an geogri mesh treate uner normal temperature of 25 o C an elevate temperature of 110 o C are given in Tale 2. The symol W0 iniates ement

8 22 omposite reinfore with wire mesh having ure for 28 ays (ontrol speimens), G0 iniates ement omposite reinfore with geogri mesh with 28 ays uring (ontrol speimens), W0 iniates ement omposite reinfore with wire mesh with 28 ays uring an then 0 uring yle in water, WH0 iniates ement omposite reinfore with wire mesh with 28 ays uring an then 0 heating yle, G0 iniates ement omposite reinfore with wire mesh with 28 ays uring an then 0 uring yle in water, GH0iniates ement omposite reinfore with geogri mesh with 28 ays uring an then 0 heating yle an so on for other numering of speimens. The utility of the ement omposites ue to effet of reinforement has een stuie at ifferent stages of loaings suh as, at first rak loa, at ultimate loa an at failure loa. The amount of utility (efletion) at first rak varies epening on the types of reinforements an variation of temperature. However, the utility at ultimate an failure loas is almost same for all the ases. An example of the loa-efletion relationships of zero heating yle with 28 ays uring is shown in Figure 5 iniating that ultimate loa is otaine at the utility range of to 12 mm an the failure loa is otaine at the utility value of 15 mm. Ultimate loa.5.0 Thir point loa, kn WH0-1 GH0-1 WH0-2 GH0-2 Failure loa Defletion at enter, mm Figure 5: Loa vs. efletion of laminate ementitious omposite showing the range of ultimate loa an failure loa

9 224 Tale 2: Dutility properties of omposites uner normal an elevate temperatures Speimen W0 WH0 G0 GH0 W0 WH0 G0 GH0 W60 WH60 G60 GH60 W90 WH90 G90 GH90 W120 WH120 Group Central efletion(mm) at first-rak loa Central efletion(mm) at ultimate loa Central efletion(mm) at failure loa to to to to to to to to to to to to to to to to to to to to to to to to to to to to to to to to to to to to

10 225 Tale 2 Cont: (Dutility properties of omposites uner normal an elevate temperatures) G to to GH to to (W= Wire, G=Geogri, H= Heating an 0, 60, 90 & 120 are no. of yles) 5.0 Disussion This is to note that the usual equation of moulus of elastiity ( ) of a omposite memer onsisting of ifferent materials uner uniaxial loaing (tension or ompression) has een given as: (11) Where an are the volume frations of utile an rittle layers respetively, as efine in earlier setion. quation 11 an also e written in the following form: ) (12) ( This equation iniates that the moulus of elastiity of a omposite ompose of utile an rittle layers uner uniaxial loaings epens on the mouli of rittle an utile layers. The terms an ( ) are ommon for oth the ases of uniaxial an flexural onitions ut the fator is ifferent epening on the loaing onitions. As an e seen from the rule of mixture (equation 12), the fator is first orer of the utile layers. In ontrast to this, the fator (equation 10) otaine through analytial investigation of a omposite flexural setion is thir orer of the utile layer. Due to this thir orer of utile portion, the laminate ementitious omposite having rittle material i.e. mortar as the matrix an utile material as the reinforement possesses utility properties whih has een verifie y experimental oservation. 6.0 Conlusion The utility properties in terms of flexural moulus an efletion of a rittle laminate ementitious omposite have een stuie analytially an experimentally. The synergy etween the rittle an utile layers of a laminate omposite is larifie through an analytial equation. The analytial oservation shows that the flexural moulus of a rittle matrix is affete signifiantly y the

11 226 utile layers, whih is of thir orer of the utile portion. The effet of the utile layer foun in analytial equation has also een verifie through experimental work. Laoratory test results reveal that the rittle matrix with only two layers of utile material possesses a goo utility uner flexural loaings. The esign utility value of laminate ementitious omposites, for example, in ase of water storage strutures may e taken as 0.5 to 1.0% within the first rak loaing range. However, for other strutures suh as partition wall where maro-raks may not e a great prolem, the esign utility value may e taken as 1.5 to 6% at the ultimate loaing range. Aknowlegement The present stuy is partly supporte y the Researh Grant No with funs from Grants-in-Ai for Sientifi Researh, Japan. The authors gratefully aknowlege the support. The finings, onlusions an any opinion expresse in this paper are those of the authors an o not neessarily reflet the views of the sponsor. Referenes Ghavami, K., Filho, R.D.T. an Barosa, N.P. (1999) Behavior of omposite soil reinfore with natural fiers, Cement an Conrete Composites, 21(1), Hossain, M.Z. an Inoue, S. (2001) Analysis of geogri reinfore ementitious Composite panels with reyle aggregates, Conrete uner Severe Conitions, nvironment an Loaing, 1, Koayashi, Y., Tanaka, Y. an Ono, M. (1992) Flexural impat amage of ferroement, Journal of Ferroement, 22(), Naaman, A.. (2000) Ferroement an Laminate Cementitious Composites, Tehno Press 000, Ann Aror, Mihigan. Rosato, D.V. (1968) History of Composite, Han Book of Fierglass an Avane Plasti Composites, New York. Ruin, M. (1969) History of Composite, Han Book of Fierglass an Avane Plasti Composites, New York.

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