Determination of properties of Althaea officinalis L. (Marshmallow) fibres as a potential plant fibre in polymeric composite materials

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Determination of properties of Althaea officinalis L. (Marshmallow) fibres as a potential plant fibre in polymeric composite materials

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  Determination of properties of   Althaea officinalis  L. (Marshmallow) fibresas a potential plant fibre in polymeric composite materials Mehmet Sarikanat a , Yoldas Seki b , Kutlay Sever c, ⇑ , Cenk Durmus  kahya d a Department of Mechanical Engineering, Ege University, Bornova, Izmir, Turkey b Department of Chemistry, Dokuz Eylul University, Buca, Izmir, Turkey c Department of Mechanical Engineering,  _ Izmir Katip Çelebi University, Çig ˘ li, Izmir, Turkey d Education Faculty, Science Education Program, Celal Bayar University, Manisa, Turkey a r t i c l e i n f o  Article history: Received 30 May 2013Received in revised form 7 September 2013Accepted 16 September 2013Available online 25 September 2013 Keywords: A. FibresB. Mechanical propertiesB. Thermal propertiesD. Electron microscopy a b s t r a c t The mechanical, thermal, chemical, crystallographic and morphological properties of althaea fibres,extracted from  Althaea officinalis  L. ,  was examined for the first time in this study.  A. officinalis  L. wasobtained from Mordog˘an, Izmir (Turkey). After extraction process, lignin, cellulose and hemicellulosecontents of althaea fibres were identified. Fourier transform infrared and X-ray photoelectron spectros-copy were utilized for surface functional groups of althaea fibres. By using X-ray diffraction analysis, CIvalue for althaea fibre is obtained to be 68%. The images of scanning electron microscopy were taken forobservation of morphology of althaea fibres. The tensile modulus and tensile strength values of althaeafibre were obtained by single fibre tensile tests as 415.2MPa and 65.4GPa, respectively. Thermogravi-metric analysis showed that thermal degradation of the fibre begins at approximately 220  C. Besides,by pulling out the althea fibre from the embedded high density polyethylene, interfacial shear strengthvalue was determined tobe8.16MPa. The results suggest that thealthaeafibre canbeusedincompositeapplications as a natural reinforcement material.   2013 Elsevier Ltd. All rights reserved. 1. Introduction Recently,naturalfibreslikekenaf,jute,banana,andflaxhavebeenusinginpolymericcompositeincreasinglyasreinforcement[1–12].Lowcost, ease of recycling, and less tool wear in the course of pro-cessingarethesomeadvantagesofthevariousplantfibres[13].Plant fibres comprise mostly lignin, cellulose, and hemicellu-lose. The remaining components are the pectin and waxsubstances, which are generally referred to as surface impurities[14]. At the molecular level, at which the fibre–matrix interactionis determined by chemical groups present on the surface of matrixand fibre, the interfacial adhesion is dependent on thephysicochemical interaction (e.g. van der Waals forces, acid–baseinteractions, hydrogenbond) and chemical bonds (covalent bonds)[15]. Chemical composition, and also moisture content, of thefibres affects the properties and end usage of them. Since highercellulose content leads to higher stiffness, natural fibres can beutilizedasreinforcementmaterialforpolymers.Becauseofthefactthat high water content, as well as moisture absorption, of thecellulosic fibres cause swelling, poor mechanical properties andinstability in dimension come into existence. Lignin content of fi-bre facilitates reactivity and allows better response to chemicalmodifications [14]. At the higher levels, the fibre–matrix interfacecan be characterized by mechanical tests carried out on eithersingle fibre micro-composites or bulk laminate composites. In theformer, a single fibre embedded in a matrix block of differentshapes and sizes is used[15]. In order to ascertaininterfacial shearstrength(IFSS), some tests such as the micro-indentation, singlefi-bre composite, and the single fibre pull-out are used [16].Inthisstudy, thealthaeafibresextractedfrom  Althaea officinalisL.  as a potential plant fibre in polymeric composite materials wereinvestigated. Up to now, previous works that addresses thecharacterization of althaea fibres and composite application of althaea fibres are not present. The morphology, chemical composi-tion, moisture content, mechanical properties, thermal stability,crystallite size and crystallinity index of althaea fibres wereevaluated. Also, IFSS value of althaea fibre–HDPE composite wasdetermined by pull out tests. 2. Materials and methods  2.1. Fibre extraction process A. officinalis  L plants were supplied from Mordog˘an (Izmir –Turkey). After cutting plant stems into small parts, the samples 1359-8368/$ - see front matter    2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.compositesb.2013.09.041 ⇑ Corresponding author. Tel.: +90 02323293535x3703. E-mail address:  kutlay.sever@ikc.edu.tr (K. Sever).Composites: Part B 57 (2014) 180–186 Contents lists available at ScienceDirect Composites: Part B journal homepage: www.elsevier.com/locate/compositesb  areembeddedinanacetonesolutionandheateduntilboiling.Aftera while solution was allowed to cooling. After 2days, the samplesweresubmergedin water until thefibres are easilyseparatedfromthestem.Highdensitypolyethylene(HDPE-I-668)withameltflowindexof5.8g/10minandadensityof0.968g/cm 3 and,obtainedbyPetkim A.S  . – Turkey, was utilized in the pull-out test.  2.2. Characterization of althaea fibres 2.2.1. Fourier transform infrared spectroscopy (FTIR) In order to identify the functional groups of althaea fibres, FTIR analysis was made. After drying and grinding processes, 1mg of theparticlesweremixedwith100mgofhighpurityinfrared-gradeKBr, compressed into pellets. Afterwards, the analysis wasperformed by using Perkin Elmer Spectrometer (Spectrum BX-II).FT-IR spectrum of althaea fibre was recorded in the range 4000–550cm  1 (resolution: 2cm  1 ).  2.2.2. X-ray diffraction analysis (XRD) X-Pert Pro Diffractometer (Philips PW3050/60) (Ni-filtered) CuK a  radiation ( k  =1.54Å) was utilized. Samples, as powders, werescanned in 2 h  ranges from 2   to 70   at 45kV and 40mA. The mostpopularmethodfor computingthecrystallinityindex(CI), theXRDheight method, was utilized in this study [17]. The CrystallinityIn-dex (CI) of the fibre is obtained [18,19] by using the followingequation: CI % ¼  I  002  I  am I  002    100  ð 1 Þ where  I  002  corresponds to (002) lattice reflection peak (the maxi-mum intensity) owing to the crystallographic form of cellulose ( I  )at a 2 h  angle of between 22   and 23  .  I  002 , the Bragg peak heightcontains the peak height owing to amorphous background.  I  am  isthe amorphous center (minimum intensity) located at a 2 h  anglebetween 18   and 19   [20–22]. Crystallite size ( L ) was computed via Scherrer’s formula [23]: L ¼  K  k BCos h  ð 2 Þ where  B  is the peak’s full-width at half-maximum,  K   is 0.89 andshows Scherrer’s constant, and  k  the radiation wavelength [24–26].  2.2.3. X-ray photoelectron spectroscopy (XPS) In order to determine elements on the surface of the althaea fi-bres, XPS was utilized. XPS analysis was performed by using aspecs ESCA instrument having a monochromatic Mg K a  radiationsource, operating at 200W (10mA, 10kV). The curve fitting wasmade by using Gaussian/Lorentzian (80/20) distributions.  2.2.4. Density measurement of althaea fibre Archimedes method was used for density measurementaccording to ASTM D 3800-9 [27]. The density of althaea fibreswas obtained to be 1.18g/cm 3 .  2.2.5. Chemical composition of althaea fibre Lignin, hemicellulose and cellulose composition of Althaeafibres were obtained by using Van Soest’s detergent method [28–30]. Moisture contents were determined through SartoriousMA45 moisture analyzer. Ash content of Althaea fibre was deter-mined in accordance with ASTM E175.  2.2.6. Measurment of tensile properties of althaea fibre The tensile strength and modulus values of althaea fibre werefound by means of Shimadzu universal testing machine (AUTO-GRAPH AG-IS Series). Details of the method were given inelsewhere [27]. The average value of minimum eight measure-ments was used for consideration.  2.2.7. Thermogravimetric analysis (TGA) TGA was conducted to determined the degradation propertiesof the althaea fibre. Thermal stability of the fibre was determinedvia Perkin–Elmer Diamond TG/DTA Analyzer in a temperatureinterval of 25–600  C. The heating rate was 20  C/min under anitrogen atmosphere. The mass of the althaea fibres was about5mg.  2.2.8. Pull-out test  In order to identify interfacial shear strength, the characteriza-tion of fibre–matrix interphase was made by using pull-out test(Shimadzu AUTOGRAPH AG-IS Series universal testing machine).Althea fibres were embedded in HDPE matrix for 60min at150  C. The cross-head speed and gauge length were 0.1mm/minand 10mm, respectively. The average value of ten successfulmeasurement was taken into account. The interfacial shearstrength (IFSS)  s d  was computed as follows [2]: s d  ¼  F  max d p l e ð 3 Þ where  d, l e ,  F  max  show the diameter, the embedded length and thedebonding force of the fibres, respectively.  2.2.9. Scanning electron microscope (SEM) observations The surface morphologies of althaea fibre was examinedthrough scanning electron microscope (FEI Quanta FEG 250).Before SEM observations, a thin layer of gold was coated on thesurface of althaea fibres by using an automatic sputter coater(EmitechK550X). Thenobservationwasconductedat anaccelerat-ing voltage of 2kV. 3. Results and discussion  3.1. FTIR analysis FTIR spectrum of althaea fibre was shown in Fig. 1. A broadabsorption band in the range of 3600–3100cm  1 corresponds tostretching vibration of O A H groups and hydrogen bond of theOH groups [31]. The stretching vibration of hydrogen-bonded(O A H)isderivedfromtheligninandcellulosestructureofthefibre[32]. The band at 2913cm  1 represents CH stretching vibrations.Saha et al. indicated that the absorbance peak at 2910cm  1 maybe due to methyl and methylene groups, C A Hstretchingvibration,present in cellulose and hemicellulose [33]. The absorption peakcentred at 1737cm  1 can be ascribed to the C @ O group of stretching vibration of ester group in hemicellulose or carboxylicacid in lignin [10,31,34]. The very small peak at around1638cm  1 may be revealed by water content (H A O A H bending Fig. 1.  Fourier transform infrared spectra for althaea fibre. M. Sarikanat et al./Composites: Part B 57 (2014) 180–186   181  vibration) of the fibre [10,34,35] or C @ O bonds on hemicellulose[36]. The peaks appearing at 1597cm  1 , 1503cm  1 and1424cm  1 may be assigned to stretching of benzene ring andCH 2  deformation of lignin, respectively [37]. The two peaksobserved at 1380cm  1 and 1330cm  1 was observed due to CH 2 wagging and CH 3  bending in lignin [37]. The peak at 1245cm  1 representsstretchingvibrationof C A Oof the acetyl groupinlignin[34,38]. The peak near 1157cm  1 can be owing to C A O A C groups,theantisymmetricbridgestretching,inhemicelluloseandcellulose[39]. The band at 1050cm  1 is due to the skeletal vibration of C A O A Cpyranosering[40].Thepeakat898cm  1 isshows b -glyco-sidic linkages in cellulose [41,42]. The band was noticed at606cm  1 corresponding to the C A OH bending [31].  3.2. XPS analysis The distribution of elements on the surface of althaea fibres isreportedinTable1.ThemainelementsdeterminedbyXPSanalysisare carbon (C) (70.2%), oxygen (O) (18.2%), nitrogen (N) (3.4%) andmagnesium (Mg) (7.5%). Small amounts of aluminium and siliconalso appear on the surface of althaea fibres. Sain and Panthapulak-kal pointed out that the relatively greater content of carbon in thestraw fibres may be ascribed to the domination of extractives andlignin [43]. The greater content of carbon atoms on the surface of wheat straw shows lignin content and waxy coating of wheatstraw [44,45]. O/C ratio for Althaea fibre is determined to be0.26. Lignin has a O/C ratio of 0.35, pectin, while hemicelluloseand cellulose have a ratio of 0.83 [36]. Brígida et al. indicated thatthe O/C ratio for green coconut fibres was obtained to be lowerthan 0.83. Therefore the surface contains a noteworthy proportionof waxes and lignin [32]. Therefore, it may be said the surface of Althaeafibresisrichinligninandlesspolar.Besides,itislikelythata good compatibility between althaea fibres and non-polar poly-mers, e.g. HDPE, may be observed.Fig.2andTable2showthedeconvolutionresultsofC1sspectra. Bymeansofcurvefitting,deconvolutionofC1speakwasmadeanditwasdeterminedthatthealthaeafibrewasmadeupofC A C/C A H,C A OH/C A O A C,C @ O/O A C A OandO A C @ Ogroups.Theproportionsof C A C/C A H, C A OH/ C A O A C, C @ O/O A C A O and O A C @ O groupswere calculated to be 2.4%, 81.2%, 9.6% and 6.8%, respectively.Kazayawoko et al. indicated that C A C/C A H, C A O, C @ O/O A C A O,and O A C @ O in untreated wood fibres shows aromatic and ali-phatic carbons, primary and secondary alcohols, aliphatic and aro-matic ethers and esters, and carboxylic acids in lignin andextractives, respectively [46].  3.3. XRD analysis The XRD pattern of althaea fibres was presented in Fig. 3. Typ-ical cellulose I pattern demonstrates a reflection peak at 2 h  =22.3  corrosponding to the 002 crystallographic plane of the cellulose Ilattice. The other major peak at 15.7   probably represents typicalcelluloseI diffractograms[47]. CIvalueforalthaeafibreisobtainedto be 68%, which is smaller than sisal (71%), flax (80%), jute (71%)and hemp (88%) and greater than wrighitia tinctoria seed fibre(49.2%), ramie (58%), cotton (60%) and sansevieria cylindrica fibres(60%) [14,19,25,48,49].  L  valuewasestimatedas 2.4nmfor althaeafibres by applying Scherrer’s formula to the (200) peak. This valueis smaller than those of cornstalk fibres (3.8nm), flax fibre(2.8nm), raffia textilis fibres (32nm), ramie fibres (16nm) andSansevieria cylindrica fibres (86nm) [19,48,50,51].  3.4. Chemical compositions of althaea fibres Table3showsthecontentofalthaeafibreandsomefibresources[14,27,52,53].AswasseenfromTable3,Lignincontentofalthaeafi- breisgreaterthanthoseoframiefibreandferulafibres.Hemicellu-losecontentofalthaeafibreisclosetothatofjutefibre.Thecontentof cellulose in althaea fibre, which is compared to those in otherfibre sources in Table 3, may be considered as relatively low.  3.5. Tensile results of althaea fibres Tensile modulus and strength of althaea fibre were determinedand a comparison with the other plant fibres [1,54–59] was made,  Table 1 Surface elemental composition of althaea fibre. C% N% O% Mg% Al% Si%Althaea 70.2 3.4 18.2 7.5 0.3 0.4 Fig. 2.  High resolution X-ray photoelectron spectra presenting the deconvolutedC1s envelope.  Table 2 Distribution of functional groups on the surface of althaea fibre. C A C, C A H C A OH, C A O A C C @ O, O A C A O O A C @ OBinding energy 285.1 286.7 287.9 289.3% 2.4 81.2 9.6 6.8 Fig. 3.  X-ray diffraction patterns of Althaea fibre.182  M. Sarikanat et al./Composites: Part B 57 (2014) 180–186   as presented in Table 4. The tensile strength of althaea fibres,determinedas415.2±11.5MPa,ishigherthanthoseofluffafibres,coir and cotton. It can be emphasized that tensile modulus foralthaea fibres is higher than those for ferula communis, banana,henequen, abaca, sisal, kenaf, coir, cotton, flax, luffa, and jute, asgiven in Table 4.  3.6. TGA analysis The differential thermogravimetric (DTG) and TGA curves of althaea fibre are presented in Fig. 4. Two degradation steps can beseeninDTGcurve.TheDTGcurveofalthaeafibreshowedaninitialpeak in the range 25–125  C due to weight loss (about 3%), whichcorrespondstothewatervaporizationinalthaeafibre.Thefirstpeakwasobservedatabout50  C.Degradationtemperatureofalthaeafi-brewasobservedintherangeof220and400  Cwithasingledecom-position step. Thermal degradation of the fibre begins atapproximately 220  C (onset degradation temperature) and maxi-mumdecompositiontemperatureis344  C.Lossinweightbetween25  Cand600  Cisabout77.9%.Themaximumdecompositiontem-peraturesofsomenaturalfibreswereobtainedtobe359  Cforokrafibre[10],365  Cforjutefibre[60],340  Cforsisalfibre[61],345  Cforflaxfibre[61], and363  Cforcurauafibre[62].Brígidaetal.pointedoutthatthelossofweightduetothedegra-dationofcelluloseandlignininthelackofdetectablelevelsofhemi-cellulose reveals the existence of only two peaks for green coconutfibres (50–350  C) [32]. Thermogravimetric analysis shows thatthe Althaea fibre is thermally stable until about 220  C similar toonset decomposition temperature of other natural fibres such asbagasse(222.3  C), kenaf(219  C), cottonstalk(221.6  C), ricehusk(223.3  C),andwood-maple(220.9  C)[63].Thus,althaeafibrescanbeusedasreinforcementifmoldingofthermosetandthermoplasticmaterialsoccursunderthistemperature.AspresentedinTable4,thetensilestrengthofalthaeafibreisintensilerangeofjutefibrewhichisoneofthecommonlyusedandcheapfibre.Moreover,thecrystal-linityindexvalueofalthaeafibres(68%)isclosetothatofjutefibre(71%). Thermal stability of jute fibre is superior to althaea fibres.However,elongationatbreakandtensilemodulusvaluesofalthaeafibrearegreaterthanthoseofjutefibres.  3.7. Morphology of fibres Fig. 5(a–c) shows SEM micrographs of althaea fibre at differentmagnifications. As it was shown in Fig. 5a, the diameter range of althaea fibres was observed in between 156 and 194 l m. As seeninFig.5bandc,althaeafibrescontainnumerouselongatedindivid-ual fibres havingdiameters of about 5–10 l m. Similar results wereobtained for kenaf fibres and sisal fibre which also contain numer-ouselongatedindividualfibreshavingdiamatersofabout6–30 l m[64,65].  3.8. Pull-out test  Fibre–matrix adhesion, as is known, in a composite structure isabasicfactorfortransferringofstressfrommatrixtofibre.Inorder  Table 3 Chemical compositions of althaea fibre and some plant fibres. Sample Cellulose (%) Hemicellulose (%) Lignin (%) Ash (%) OtherAlthaea 44.6 13.5 2.7 2.3 36.9Ferula [27] 53.3 8.5 1.4 7.0 29.9Banana [52] 32–55 27–32 5–10 1–4 Jute [48] 72 13 13 2Sponge gourd [1,52] 62 20 13 0.4–3Kenaf  [53] 53.14 14.33 8.18 16.99Straw [48] 40 28 17 15Ramie [48] 76 15 1 8  Table 4 Tensile properties of althaea and other natural fibres. Fiber Tensile strength (MPa) Tensile modulus (GPa) Elongation at break (%) ReferenceAlthaea fiber 415.2 65.4 3.9 In this studyLuffa cylindrica 385 12.2 2.65 [1,27]Kenaf 930 53 1.6 [68]Flax 500–1500 27.6 2.7–3.2 [69,70]Ramie 400–938 61.4–128 3.6–3.8 [27,55,56]Hemp 690 70 2.0–4.0 [59]Pineapple 180–748 25–80 1.6–3.2 [56,71–73] Jute 400–773 10–30 1.5–1.8 [2,14,27,33,54–56,74]Sisal 511–635 9.4–22 2.0–2.5 [54,73,75]Abaca 756 31.1 2.9 [58]Banana 700–800 27–32 2.5–3.7 [55,56]Ferula Communis 475.6 52.7 4.2 [27]Coir 95–220 2.5–6.0 13.7–51.4 [55,57,76–78]Piassava 76.9 2.93 10.45 [24]Coconut 131–175 4–6 15–40 [79] Fig. 4.  Thermogravimetric analysis curves of althaea fibre. M. Sarikanat et al./Composites: Part B 57 (2014) 180–186   183  to transfer the load from matrix to fibre, which is also required forgood performance, a strong fibre–matrix adhesion is necessary[66]. The althaea fibre–HDPE matrix interfacial shear strength(IFSS) was obtainedtobe8.16±1.12MPa. Li Y. et al. haveobtainedIFSSvalueofsisal/HDPEas1.6MPa[67]. TheIFSSvalueobtainedinthestudyis aboutfivetimesgreaterthanthatof sisal/HDPE, whichindicates a better adhesion between althaea fibre and HDPE. 4. Conclusion The althaea fibres were extracted from  A. officinalis  L. andcharacterized by using different methods. The surface elementalcompositionsof althaeafibrewere determinedto be richin carbon(70.2%),oxygen(18.2%),andmagnesium(7.5%).Inaddition,O/Cra-tioforalthaeafibrewascalculatedas0.26.Crystallinityindexvaluefor althaea fibre from XRD analysis was obtained to be 68%. Crys-tallite size value was estimated to be 2.4nm for althaea fibre byapplying Scherrer’s formula to the (200) peak. Cellulose, hemicel-lulose,ligninandashcontentofalthaeafibreare44.6,13.5,2.7and2.3%, respectively. By means of tensile tests, tensile modulus andstrength values of the fibre were determined to be415.2±11.5MPa and 65.4±7.2GPa, respectively. Thermaldegradation of the fibre starts at approximately 220  C and themaximum decomposition temperature is 344  C. The fibre–matrix(althaea fibre–HDPE) interfacial shear strength was measured as8.16±1.12MPa. Since the degradation temperature of althaea fi-bre is higher than the melting temperature of HDPE, althaea fibresreinforced HDPE composites may be fabricated by utilizing twinscrew extruder. Besides, we offer that althaea fibre may be usedmaking composites materials with a thermoset matrix. In sum-mary, althaea fibres may be utilized as a natural fibre to reinforcepolymeric composites.  Acknowledgment The Authors acknowledge Mithat Yüksel (Prof. Dr.), SelmanGüls  en and BurhanS  _ IMS  _ IR for their valuable supports to our work. References [1] Seki Y, Sever K, Erden S, Sarikanat M, Neser G, Ozes C. Characterization of luffacylindrica fibers and the effect of water aging on the mechanical properties of its composite with polyester. J Appl Polym Sci 2012;123(4):2330–7.[2] Bozaci E, Sever K, Demir A, Seki Y, Sarikanat M, Ozdogan E. Effect of theatmospheric plasma treatment parameters on surface and mechanicalproperties of jute fabric. Fiber Polym 2009;10(6):781–6.[3] Sever K, Sarikanat M, Sekai Y, Erkan G, Erdogan UH. The mechanical propertiesof gamma-methacryloxypropyltrimethoxy silane-treated jute/polyestercomposites. J Compos Mater 2010;44(15):1913–24.[4] Sarikanat M. The influence of oligomeric siloxane concentration on themechanical behaviors of alkalized jute/modified epoxy composites. J Reinf Plast Compos 2010;29(6):807–17.[5] Sever K. The improvement of mechanical properties of jute fiber/LDPEcomposites by fiber surface treatment. J Reinf Plast Compos 2010;29(13):1921–9.[6] Chen Y, Sun LF, Chiparus O, Negulescu I, Yachmenev V, Warnock M.Kenaf/ramie composite for automotive headliner. J Polym Environ2005;13(2):107–14.[7] Wang LH, Xu H, Teng CQ, Han KQ, Yu MH. Full biodegradable thermoplasticcomposite: natural ramie fiber reinforced PLA-PCL copolymer compositeprepared by in situ polymerization. In: Proceedings of 2005 internationalconference on advanced fibers and polymer materials (ICAFPM 2005), vols. 1and 2; 2005. p. 1019–20.[8] Hepworth DG, Hobson RN, Bruce DM, Farrent JW. The use of unretted hempfibreincompositemanufacture. ComposPart A–Appl Sci Manuf 2000;31(11):1279–83.[9] Mwaikambo LY, Ansell MP. The effect of chemical treatment on the propertiesof hemp, sisal, jute and kapok for composite reinforcement. Angew MakromolChem 1999;272:108–16.[10] De Rosa IM, Kenny JM, Puglia D, Santulli C, Sarasini F. Morphological, thermaland mechanical characterization of okra (  Abelmoschus esculentus ) fibres aspotential reinforcement in polymer composites. Compos Sci Technol 2010;70(1):116–22. Fig. 5.  Scanning electron microscopy micrographs of althaea fibre.184  M. Sarikanat et al./Composites: Part B 57 (2014) 180–186 
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