Mechanical Characterization of Carbon Fibres Recycled by ...

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Mechanical Characterization of Carbon Fibres Recycledby Steam Thermolysis

Maxime Boulanghien Mohamed RrsquoMili Geacuterard Bernhart Florentin BerthetYannick Soudais

To cite this versionMaxime Boulanghien Mohamed RrsquoMili Geacuterard Bernhart Florentin Berthet Yannick Soudais Me-chanical Characterization of Carbon Fibres Recycled by Steam Thermolysis A Statistical ApproachAdvances in Materials Science and Engineering Hindawi Publishing Corporation 2018 2018 art8630232-10 p 10115520188630232 hal-01799722

Research ArticleMechanical Characterization of Carbon Fibres Recycled by SteamThermolysis A Statistical Approach

M Boulanghien 123 M RrsquoMili4 G Bernhart1 F Berthet1 and Y Soudais2

1Institut Clement Ader (ICA) Universite de Toulouse CNRS Mines Albi UPS INSA ISAE-SUPAERO Campus Jarlard81013 Albi CT Cedex 09 France2Universite de Toulouse Mines Albi UMR CNRS 5302 Centre RAPSODEE Campus Jarlard F-81013 Albi cedex 09 France3Alpha Recyclage Composites 4 rue Jules Vedrines 31400 Toulouse France4INSA-Lyon MATEIS UMR CNRS 5510 Universite de Lyon 7 Avenue Jean Capelle 69621 Villeurbanne France

Correspondence should be addressed to M Boulanghien mboulangmines-albifr

Received 16 March 2018 Accepted 23 April 2018 Published 20 May 2018

Academic Editor Akihiko Kimura

Copyright copy 2018 M Boulanghien et al )is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

)e recent development of technologies for recycling carbon fibre reinforced plastics (CFRPs) leads to the need to evaluate themechanical response of recycled carbon fibres As these fibres are likely to be degraded during the recycling treatment it is veryimportant to determine their tensile residual properties so as to evaluate their ability as reinforcement for new compositematerials Carbon fibres reclaimed by a steam-thermal treatment applied to degrade the epoxy resin matrix of a CFRP are hereanalysed Two conditions were chosen so as to reach two degradation efficiency levels of the steam thermolysis Several carbonfibre samples were selected for mechanical testing carried out either on single filaments using single fibre tensile tests or on fibretows using bundle tensile tests It is shown that the single fibre tensile test leads to a wide variability of statistical parametersderived from the analysis Bundle tensile tests results were able to indicate that fibre strength of recycled carbon fibre is similar tocorresponding as-received carbon fibres thanks to a statistically relevant database Wide number of tested filaments enabledindeed to obtain low scatters

1 Introduction

Carbon fibre reinforced plastics (CFRPs) have been widelyused these last years in many industrial sportive andtransport applications especially for their low weight andhigh strength )e global carbon fibre market is expected toreach high annual growth rates until the next few yearsAlthough the current global demand for carbon fibre 82400tons per year is lower than expected in last yearrsquos marketreports [1 2] it is still expected to grow at a minimal annualrate of 90 Global demand in carbon fibres is expected toreach 116000 tons per year in 2021 for the less optimisticscenario [3] whereas other projections estimate a 150200tons demand [4 5] In addition the carbon fibre reinforcedcomposites market obviously shows very similar growthtrends While in 2013 the global demand for this kind of

material was 72000 tons recent reports expect this marketto reach a 191000 tons demand by 2022 [6])e high growthperspectives of wind turbines and aerospace industries canmainly explain the intensification in using CFRP as theirrecent introduction in the automotive industry )is dra-matic increase in using carbon fibre means that the quantityof generated waste will also rise significantly either as an off-cut or as an end-of-life composite product )us it appearsto be critical to develop suitable composite recycling tech-nologies that could offer interesting environmental andeconomic perspectives If the environmental and socialresponsibilities are the first arguments for such developmentefforts market economics is still a key factor Consideringthat the carbon fibre marketrsquos potential is clearly affected bythe high price of carbon fibre although its production ca-pacity is nowadays growing there is a huge opportunity for

HindawiAdvances in Materials Science and EngineeringVolume 2018 Article ID 8630232 10 pageshttpsdoiorg10115520188630232

future or existing recycled carbon fibre producers andprocessers to answer new needs

Although landfilling is currently the main option tomanage CFRP wastes the high added value of carbon fibreassociated with a restrictive European legislation [7 8] hasdriven researchers and engineers to look for new recyclingtechnologies especially as life cycle analysis already showedthat the environmental benefit is much higher for a recyclingscenario than for a classical incineration or landfilling [9ndash11])ese last years the main studied approach has been todegrade the organic matrix to leave clean the carbon fibresthese ones being valorised as reinforcement in second-generation composite products Various technologies fo-cused much effort in this way solvolysis [12] pyrolysis [13]and steam thermolysis [14]

Solvolysis is a chemical process based on the organicmatrix depolymerisation by means of a solvent Most of thetime near- or supercritical conditions are required to obtainthe best results and avoid the use of aggressive chemicalsolvents that make the treatment more complex Methanol[15] propanol [16ndash18] water [19 20] or even a mixture ofwater and ethanol [21] in supercritical conditions weresuccessfully used the removal of an epoxy matrix can reach100 without loss of tensile strength of reclaimed carbonfibres Although more investigation efforts have been madein these methods there is still no example of an industrialscale launch of this technology applied to the CFRP recy-cling supercritical reactors are expensive as they have to bedesigned for high temperatures high pressure and a cor-rosive environment

Pyrolysis is based on the organic matrix thermal deg-radation It has been the most studied thermal process[22ndash24] and some variations can be found as the microwaveheating pyrolysis [25 26] Depending on the matrix natureand the considered variation the efficiency of such a treat-ment is variable from 80 to 99 of eliminated resinReclaimed carbon fibre tensile strength can be degraded dueto the presence of char on the fibre surface that needs to beeliminated by an air posttreatment However in spite oflower results than what can be obtained in solvolysis py-rolysis is a cost-efficient technology well suited to the rel-atively undeveloped composites recycling market )eseresearch efforts have even been commercially applied byEuropean companies such as ELG Carbon Fibre (UnitedKingdom) Karborek (Italia) Reciclalia (Spain) or CFKValley Stade Recycling (Germany) and American ones suchas Adherent Technologies Inc or Carbon Conversions

Finally steam thermolysis is a thermochemical processusing superheated steam at environmental pressure fordegrading organic materials It is a cost-efficient technologyas no energy-consuming posttreatment of reclaimed fibres isneeded nor high pressure environment requiring discon-tinuous working flow and expensive reactors It has beenapplied to the material recovery of circuit boards [27] to thedegradation of polyimide [28] or to the production of oilfrom biomass [29] Only few studies focused on the steam-thermolysis process applied to the recovery of carbon fibrefrom CFRP wastes [10 30ndash33] Steam thermolysis enables toefficiently degrade the organic matrix of the CFRP waste

which makes this technology a serious alternative )e aimhere is to evaluate the efficiency of this technology byproposing a true mechanical characterization of thereclaimed carbon fibres considering two techniques singlefibre tensile test (SFTT) and bundle tensile test (BTT) Usingthe widely used SFTT technique some inherent variabilitysources of the tensile strength determination can appear asthe specimen selection the damage of the fibres during thesampling operation and the difficulty in getting a perfectalignment of the fibre with the tensile machine Hence thebundle tensile test can become an alternative for the tensilestrength determination of recycled carbon fibres as it hasbeen successfully used to study virgin glass ceramic andcarbon fibres

2 Theoretical Background

21 Bundle Model )e theoretical model of dry bundle offibres considers a discrete set of N parallel fibres with sta-tistically distributed strength When the bundle is loadedfibresrsquo mechanical behaviour is linear elastic until theirfailure at the applied stress σi i 1 N When a fibrebreaks in the bundle the supplementary load that wascarried by the broken fibre is equally distributed Twodistribution cases can be differentiated )e global loadsharing (GLS) considers that the supplementary load isequally distributed among the survival fibres whereas thelocal load sharing (LLS) considers that the supplementaryload is equally distributed among the neighbouring fibres)e first case is here considered but needs to fit assumptionscalled Colemanrsquos conditions fibre length must be constantwithin the bundle stress-strain relationship follows Hookersquoslaw until failure the released load at a fibre break is uni-formly distributed among the surviving fibres and no ex-ternal phenomena should lead to a premature fracture offibres As a consequence any friction phenomena betweenfibres within the bundle must be avoided as it would lead toa catastrophic fracture of the whole bundle Specific cares aretaken to avoid this effect

22 Statistical Distribution of Fibre Strength Fracture ofcarbon fibres is likely to be caused by flaws within thegauge length Flaws are randomly distributed and showa high heterogeneity in size location and severity )ena wide variation in failure load is expected and the ultimatetensile strengths measured on specimens have a statisticaldistribution Weibull analysis is a well-known methodtypically used for fracture statistics for brittle materialsFor a single gauge length and uniform uniaxial tensilestresses the Weibull equation of failure probability isgiven by

P 1minus exp minusV

V01113888 1113889

εε0

1113888 1113889

m

1113890 1113891 (1)

where V is the stressed volume and V0 a reference volumeε0 σ0Ef σ0 being the scale factor Ef the Young modulusof a fibre and m the Weibull modulus As a common ap-proach a Weibull diagram is usually constructed by using

2 Advances in Materials Science and Engineering

empirical estimators of failure probability )en the sta-tistical parameters are obtained by fitting (1) to the Weibullplot

However the validity of the normal distribution todescribe the distribution of strengths has already beenshown [34] and the statistical parameters that were derivedfrom are considered to provide a better fit to the dataBesides it was demonstrated that the statistical parametersderived from a Weibull distribution showed a wide vari-ability due to the construction of Weibull plots using anestimator and the sample size generally too small that doesnot enable to take into account the natural variability ofmaterial properties )erefore a statistically relevant data-base and normal distribution are used for the analysis offailure data Equations of probability density function f(ε)and normal distribution PN(Ele ε) are as follows

f(ε) 1

S2π

radic expminus(εminus μ)2

2S21113890 1113891

PN(Ele ε) 1113946ε

0f(ε) dε

(2)

with ε the strain μ the mean of strain and S its standarddeviation

23 Bundle Behaviour Assuming that the applied load isuniformly distributed among the surviving fibres in the towand that fibres have a linear load-strain relationship up tobreakage the force-strain relation during a tensile test isgiven by [35]

F(ε) N0 middot Af middot Ef middot ε middot [1minusP(ε)] (3)

where N0 is the number of initially loaded fibres Af is thecross-sectional area of each of the fibres Ef is their Youngrsquosmodulus ε is the applied strain and P(ε) is the probability offailure of a fibre at a strain ε given by (2)

3 Materials and Methods

31 Composite Manufacturing Composite samples weremade by liquid resin infusion A low-viscosity bicomponentsystem was used a Sicomin SR1710 Infusion epoxy resinmixed with a Sicomin SD8822 hardener A twenty hours atroom temperature plus sixteen hours at 60degC polymerisationcycle were applied before removing the system from themould Details of procedure can be found in a work of Baleaet al [36] Carbon reinforcement was a carbon twill 2times 2(Hexcel 46285 U1200) made from AS4C carbon fibresSixteen 400times 400mm plies were stacked so as to obtain anapproximately 800 grams plate for a 4mm final thickness)e average fibre mass fraction was 66 corresponding toa fibre volume fraction of 555)ese plates were cut by themean of a circular saw in order to get 50times120mm samplesable to be used in the steam-thermolysis reactor

32 Recycling Carbon Fibres )e recycling was conducted ina bench-scale reactor as shown in Figure 1 Previous in-house

produced composite samples are treated by steam thermolysisso as to reclaim carbon fibres )e thermochemical processuses superheated steam at atmospheric pressure in order todegrade the organic matrix of the composite

A removable crucible was made from a stainless-steelfabric (own design 1000mL))is crucible was coupled witha thermogravimetric analyser and placed within the heatingzone )e experimental reactor is provided with an easyopening chamber located on the top of the apparatus Oncethe experimental parameters reached the desired level thechamber that contains scrap composites samples (100 g) isopened so as to let them fall into the reactor After epoxyresin was decomposed and once the system cooled downrecycled carbon fibres were collected from the reactor Nocleaning of the surface is required before their use )reecategories of products are actually collected a solid fractionthat is constituted of recycled carbon fibres a permanentgaseous fraction principally constituted of methane andcarbon monoxides and a last condensable gaseous fractionthat is constituted of pyridines benzene and phenols [31]

A unit made up of a steam generator and a nitrogeninput manages atmosphere control )e experimental deviceis designed to operate in a wide range of conditions tem-perature from 100 to 1000degC steam flow rate from 0 to1000 gmiddothminus1 and nitrogen flow rate from 0 to 20 Lmiddotminminus1Experimental conditions and reclaimed samples are de-scribed in Table 1 Experiments were carried out underatmospheric pressure for two hours at two temperatures400degC and 500degC In both cases the nitrogen flow rate was setto 108 Lmiddotminminus1 whereas the steam flow rate was 90 gmiddothminus1Reclaimed carbon fibres from these treatments are re-spectively named RF400 and RF500

33 Fibre Morphology Yields of eliminated resin weremeasured by dissolution of remaining resin with hot sul-phuric acid according to the French standard NF EN 2564

Environmental scanning electron microscopy (ESEM)was used to observe surface texture and morphology of thefibres as well as visual signs of residual resin impurities Fibrebundles of each sample were randomly selected andmounted on an adhesive carbon layer stuck onto an alu-minium stub As carbon fibre is conductive no other specificpreparation was needed )e acceleration voltage was 20 kVDiameters of the fibres were also measured using imageanalysis with ImageJ software For each sample an averagediameter was determined by measuring a population of 200fibres from an image database obtained during the corre-sponding ESEM analysis

34 Mechanical Properties

341 Single Fibre Tensile Test )emost common techniquethe single fibre tensile test (SFTT) measures the strength ofindividual fibres By measuring many fibres a wide pop-ulation can be formed and used for stress analysis )is testwas employed to determine the tensile strength of the threefibre types of the study Method is based on internationalstandards ISO 11566 [37] A single filament is bonded to

Advances in Materials Science and Engineering 3

a paper window with cyanoacrylate Loctite 409 en thespecimen is inserted into a tensile rig equipped with a 5Nload celle carbon bre has to be carefully aligned with thetensile testing machine axis Each side of the paper windowwas cut before testing e gauge length was 25mm ecrosshead speed was set to 01mmmin Carbon brespecimens were loaded at room temperature until failureand the force displacement curve was recorded At least 40laments were tested for each bre type that is VF RF400and RF500

342 Bundle Tensile Test Mechanical tests were also carriedout on bre bundles using bundle tensile tests (BTTs) so as toquantify the tensile strength of the recycled carbon bres Itis based on the random and individual bre failure withinthe bundle erefore statistics laws are used for analysisis statistical data approach enables to take into consid-eration a wide single lament population

One of the diculties is the measurement of a reliablebundle strain An extensometer is placed on heat shrinktubes previously threaded on each tip of the bundle as it isshown in Figure 2 to dene the gauge length Each tip isimpregnated with Araldite 2015 resin and then poly-merised at 70degC for one hour Impregnated tips are theninserted in metallic tubes and lled again with Araldite2015 resin and polymerised at 70degC for one hour Metallictubes enable a regular clamping by tensile grips Duringany of these preparation steps a specic care must betaken to avoid any handling of the bre bundle within thegauge length Before loading the sample is lubricated bypetroleum wetting avoiding premature rupture due tofriction phenomena between bres within the bundleis meticulous experimental procedure is also describedin [38 39]

e tensile tests were performed using a pneumatictesting machine with a 2 kN cell ey were carried out at

Table 1 Samples of the study and associated steam-thermolysis experimental conditions

Samples Treatment temperature (degC) Nitrogen ow rate (Lmin) Steam ow rate (gh) Treatment time (h)VF Virgin bre (reference) mdash mdash mdashRF400 400 108 90 2RF500 500 108 90 2

Removable crucible

ermogravimetric analyser

Composite samples

Easy opening chamber Output Gas

Steam

Nitrogen

Heating zone

Temperature measurement

Figure 1 A schematic diagram for the recycling process


room temperature under constant displacement rate of006mmmin on specimens prepared according to theprevious procedure with a gauge length of 60mm Carbonbre bundles were loaded until failure and the load dis-placement curve was recorded For each bre type about3000 laments were tested in each tow For RF500 bre 3tows were tested so as to make sure measurements arerepeatable

343 Methods of Failure Data Analysis For single breanalysis the means of ultimate strengths are known bycollecting individual data Both normal and Weibull dis-tributions are used Weibull plots are constructed using anempirical distribution function Pj (jminus 05)N withN thesample size and j the specimen number

For bundle analysis the mean of bre tensile strengthand its standard deviation are obtained by tting an ana-lytical curve based on (4) to the experimental data Firstlythe load-strain curve of the bundle is determined by thetensile test as described in 342 en the initial slope of thelinear part of the analytical curve is tted to the experimentalone Equation (3) can also be written as

F(ε) N0 middot Af middot Ef middot ε middot [1minusP(ε)] R0ε middot [1minusP(ε)] (4)

where R0 is the initial slope of the (Fminus ε) curve Finally bytting the nonlinear parts of experimental and analyticalcurves the mean of strains to failure μ and its standarddeviation S are determined Assuming Youngrsquos modulus ofeach type of bre is constant the mean of ultimate tensilestrength of each type of bre and its standard deviation canbe determined

4 Results

41 Eciency of Steam-ermal Treatments e tempera-ture is an important parameter on the degradation kineticand thus on the eciency of the treatment Measurements ofyields of eliminated resin are shown in Table 2 A 400degCthermolysis did not enable the elimination of all the resin ofthe composite (yield of eliminated resin reached 95 inmass) whereas the 500degC treatment was more ecurrenective andenabled to degrade all the epoxy resin (yield of eliminatedresin is higher than 99 in mass)

Figure 3 shows an ESEM image of the virgin bre VFand recycled carbon bre RF500 Examination of images ofseveral bres from dicurrenerent batches clearly showed novisible alteration of the surface topography due to steam

thermolysis Similar regular and clean surfaces are observedindicating the eciency of the treatment that removed themost part of the resin of the composite material RecycledRF400 bres are shown in Figure 4 A few small particles canbe seen and are attributed to resin residues that stuck on thesurface e 400degC steam-thermal treatment left littlequantities of residual resin on a smooth and regular surface(5 by mass of residual resin) e particles have a sizeranging from 2 to 20micrometres avoiding individual bresto be properly separated ese observations obviously showthe importance of temperature on the degradation kinetic

emean diameters were calculated as 71 69 and 69μmrespectively for VF RF400 and RF500 bres (Table 1) is isin good agreement with the value of 69μm provided by themanufacturer [40] It may be inferred from the similarity of themean and standard deviation values of the bres with visualevidence from the ESEM that there was no alternation to thebre morphology


421 Single Fibre Mechanical Analysis Two statistical pa-rameters are deduced from the analysis the mean of strengthμ and its standard deviation S From the experimental datathe 95 condence interval of mean value is also establishedas it is often used as an indicator of the precision of anestimate derived from an analysis For a sample sizeN 40μ the sample mean and S the standard deviation the 95condence interval of mean value (Ic) is given by

Ic μminus 202SN

radic μ + 202SN

radic[ ] (5)

Statistical parameters of normal distribution of strengthdeduced from SFTT are reported in Table 3 e averagetensile strength of RF500 bre is slightly dicurrenerent from thatof the corresponding virgin bre VF A 4 decrease wasobserved However the result shows a high degree of var-iability with a standard deviation of about 540MPa fora tensile strength of 3610MPa Looking at the frame given bythese 95 condence intervals it appears to be dicult toobtain reliable results Indeed there is no statistically rep-resentative dicurrenerence between the two samples us itcould be premature to arm that the tensile strength loss isreally signicant or not although it could be negligibleregarding the low decrease of only 4 Nevertheless it canbe stated that reclaimed RF400 bre showed substantialstrength degradation relatively to the virgin bre Eventaking into account the high degree of variability of mea-surements tensile strength loss of RF400 bre is likely to be

Table 2 Studied samples and associated steam-thermolysis ex-perimental conditions

Fibres Yield of eliminatedresin ()

Mean diameter (standarddeviation) (μm)

VF mdash 71 (07)RF400 95 69 (07)RF500 gt99 69 (07)

Fibre bundle

Extensometer

Tensile grip

Figure 2 Bundle tensile test conguration


signicant is could be explained by the presence of re-sidual resin on the bre surface that could act as stressconcentrators leading to a premature failure of the breFigure 5 shows mean stress-displacement curves obtainedfrom single bre testing and condence interval on the meanvalue of tensile strength and displacement at failure As it canbe seen that average value of failure strain is lower than thatof virgin and RF500 bres it conrms that the single brefails before reaching its maximum stress level

Weibull diagrams derived from this analysis are alsopresented in Figure 6 as they are a usual approach fordescribing failure behaviour of brittle materials ey arecompared to log-log graphs of normal distributions of stressto failure for each sample A good agreement between bothdistributions is obtained for RF400 bre However a cleardiscrepancy can be noticed at the low failure probabilities forVF and RF500 bres e RF500 Weibull plot suggests thepresence of two domains reecting two distinct failuremodes for this bre whereas it does not seem to be the case inFigure 7 showing the probability density function of thisbre and the associated experimental points Indeed at the

lower stress values experimental data do not clearly showtwo distinct populations Many other reasons can be ad-vanced to explain discrepancies on Weibull plots and highscatters observed on SFTT results the use of an empiricalestimator the selection and damage of the bres during theoperation of sampling or the low sample size leading toa low representativity in the case of brittle materials [35 41]A wide distribution in aw size is inevitable considering theselection of test specimens While variability cannot beavoided until a relevant database is used for failure analysis

Table 3 Statistical parameters of normal distributions obtainedfrom single bre tensile tests analysis and related 95 condenceintervals

Fibresamples

Mean of tensilestrength (MPa)

Standarddeviation(MPa)

95 condenceinterval (MPa)

VF 3776 547 146RF400 3272 672 179RF500 3610 540 144

4000

3000

2000

1000

0

Appl

ied

stres

s (M

Pa)

00 01 02 03 04 05 06 07 08Displacement (mm)

VFRF400RF500

Figure 5 Mean displacement-applied stress curves obtained fromSFFT and 95 condence intervals

(a) (b)

Figure 3 ESEM images of VF (a) and RF500 (b) bres (times5000)

(a) (b)

Figure 4 ESEM images of RF400 bre (a times1000 b times5000)


there is nomeans to evaluate the validity of this selection andso to validate the full strength retention of recycled carbonbres

422 Bundle Mechanical Analysis Figure 8 shows typicalload-strain curves obtained from bundle mechanical anal-ysis It is easy to see that a good agreement is obtainedbetween experiment and model experimental curve andnormal distribution-based curve were well tted e loaddecrease beyond maximum ts well with that obtainedexperimentally Maximum load also depends on the numberof laments in each tested tow and is consequently notalways the same for a same sample Exact number of la-ments is determined from the initial slope of the load-strain

curve Statistical parameters of normal distribution ofstrength extracted from analysis of bundle tensile tests arelisted in Table 4

e RF400 sample shows the lowest mean strength of3657MPa whereas the VF sample and RF500 sample showa quite similar mean strength of about 3860MPa Variabilityof the results rst seems to be as high as that obtained forsingle lament tensile tests However as the tested pop-ulation is very wide (Table 4) condence intervals are lowerthan those obtained by single bre tensile tests analysis isenables to get more condence on the precision of the es-timate us no signicant dicurrenerence can be noticed be-tween RF500 bres and VF bres indicating that steam

3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]

RF400 normal distributionRF400 Weibull distribution

(a)

3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]


VF normal distributionVF Weibull distribution

(b)

Figure 6 Comparison of Weibull plot and normal distribution of stress to failure of RF400 RF500 and VF bres (log-log plots)

2

4

6

8

10

Failu

re ev

ents

2000 3000 4000 5000 6000Tensile strength (MPa)

Experimental pointsRF500 probability density function

Figure 7 Normal probability density function of RF500 bre andfrequency histogram of failure events

100

200

300

400

Load

(N)

00 05 10 15 20 25Strain ()

VF-analyticalVF-experimentalRF400-analytical

RF400-experimentalRF500-analyticalRF500-experimental

Figure 8 Typical load-strain curves obtained from bundle me-chanical analysis and their tted analytical curve


thermolysis enables to retain tensile strength of thereclaimed carbon bre RF500 It shows that steam-thermalprocess has only little ecurrenect on carbon bresrsquo mechanicalproperties although the recycling was performed at 500degCOn the contrary a decrease of almost 200MPa acurrenectedRF400 bres Resin nodules on the surface of RF400 brescould be a contribution to the increase of friction betweenlaments during the tensile test Friction in BTT leads toa premature failure of the neighbouring bres in the tow [42]contributing to a steep load decrease beyond the highestmeasured load However the curve seems to be smooth anddoes not show any signs of bre friction especially as an-alytical curve ts very well with experimental data Indeedanalytical data are based on bundle theory that considersthat bres are independent As in single bre tensile tests theRF400 tensile strength decrease rather suggests that resinnodules could act as stress concentrators that lead to pre-mature failure of single laments in the tow

5 Discussion

Figure 9 shows that tensile strength values obtained frombundle tensile tests are in good agreement with those ob-tained by SFTT although a slight dicurrenerence can be noticedHowever when taking into account the larger gauge lengthof tows (60mm instead of 25mm for single bres) tensilestrengths should be much lower than those obtained bysingle bre testing Indeed carbon bre tensile strength isdependent on its length [43] More generally the geometryof carbon bre plays an important role in its strength[44 45] e higher is its length the larger is the number ofaws and thus the probability to nd a severe aw that leadsto fracture of the bre Just as the bre diameter that isrelated to the bre volume that increases the probability tond a severe aw at is why higher gauge lengths shouldlead to lower strengths For these reasons experimental datamust be statistically analysed Taking into account a statis-tically signicant sample size bundle tensile test enables toovercome uncertainties that usually acurrenect single bre tensiletests analysis as the specimen selection the damage of bresduring sampling or the sample size is is why it is rea-sonable to consider that dicurrenerences observed betweenbundle and single lament testing results conrm thatvariability in single bre testing is high and inevitable andthat results that are derived from could have likely beenhigher or lower if experiments were repeated On this pointrepeatability of the bundle tensile test was investigated on

RF500 bre Table 5 shows that only very slight dicurrenerencecan be seen between average tensile strengths lower than1 Most of all the 95 condence interval is quite the samefrom one experiment to another It only changes a little onaccount of the change in the number of laments in the towthat directly has a consequence on this interval value istest is a repeatable way to generate large databases ina reasonable amount of time in order to take into account theheterogeneity of carbon bres that naturally leads to highscatter in tensile strength results [45] if only a small pop-ulation is considered In this study bundle tensile test en-abled to characterize mechanical properties of recycledcarbon bres with a good precision However the BTTneedsvery meticulous preparation and advanced statistics to beimplemented At the contrary SFTT only needs an easy-to-follow procedure and data can be readily analysed Alsogeometry of most of CFRP recycling bench-scale reactorsdoes not enable to reclaim recycled carbon bre lengthshigher than 50mm which makes it dicult to determinetheir tensile properties by BTT

6 Conclusion

Steam-thermal process was used in a bench-scale reactor torecycle carbon bre from epoxy resincarbon bre com-posites Properties of the recycled carbon bres werecharacterized using ESEM single bre tensile test andbundle tensile test Carbon bres were properly separatedfrom polymer matrix during the treatment showing thata steam-thermal treatment is ecient and enables to reachhigh resin elimination levels

4500

4000

3500

3000

2500

Mea

n str

engt

h (M

Pa)

VF VFRF400 RF400RF500 RF500

Single fibretensile test

Bundle tensiletest

Figure 9 Mean strengths and their 95 condence intervalsobtained from single bre tensile tests and bundle tensile tests

Table 5 Statistical parameters of normal distributions obtainedfrom three RF500 bundle tensile tests analysis and related 95condence intervals

Samplenumber

Number oflamentstested

Mean oftensilestrength(MPa)


95condenceinterval(MPa)

1 2940 3852 591 182 2615 3849 598 193 2850 3864 644 19

Table 4 Statistical parameters of normal distributions obtainedfrom bundle tensile tests analysis and related 95 condenceintervals

Fibresamples





VF 3240 3864 573 20RF400 3390 3657 437 15RF500 2940 3852 591 19


Two techniques were used for mechanical character-ization of recycled carbon fibres Single fibre tensile test didnot allow to validate the full strength retention of recycledcarbon fibres due to unavoidable high variability of theresults Bundle tensile tests were able to show that a 500degCsteam-thermal treatment enables to leave clean carbon fibreswith no degradation of tensile properties )us advantagesof bundle tensile tests were highlighted no selection ofspecimen and a relevant database that enabled to get reliableresults

)erefore steam thermolysis not only degrades thewhole part of matrix resin of the composite so as to leaveperfectly clean carbon fibres but also enables to recoverfibres with full tensile strength retention Valorisation ofthese fibres could be possible Properties of composites madefrom recycled carbon fibres should be measured so as toreveal the viability of such a process to produce recycledcarbon fibres from epoxy-based composite materials Recentworks considered different ways to reintroduce them instructural components although potential applications arecritical to identify [46ndash48] )e recycling of CFRP is ac-quiring a considerable importance due to legislative contextand the need to find sustainable solutions for waste pro-cessing Steam-thermal process also demonstrated its abil-ities in this field

Data Availability

Analysed and generated datasets underlying the findings of thecurrent study are available from the corresponding author onrequest

Conflicts of Interest

)e authors declare that there are no conflicts of interest re-garding the publication of this paper

Acknowledgments

)e work presented in this paper was funded by Frenchcompany Alpha Recyclage Composites and French associationANRT (Association Nationale Recherche Technologie) )eauthors gratefully acknowledge their support

References

[1] IHS Markit ldquoIHS chemical carbon fibrerdquo in Chemical Eco-nomics Handbook IHS Markit London UK 2016

[2] Smithers Apex Market Intelligence =e Future of CarbonFiber to 2017 Global Market Forecasts Smithers ApexLeatherhead UK 2012

[3] T Kraus and M Kuhnel =e Global CFRP Market Com-posites market report 2015 market developments trendsoutlook and challenges 2015

[4] S Das J Warren and DWest Global Carbon Fiber CompositesSupply Chain Competitiveness Analysis CEMAC (Clean EnergyManufacturing Analysis Center) Technical report 2016

[5] C Red ldquoGlobal markets for carbon fiber composites adap-tations to high growth and market maturity compositesworldrdquo in Proceedings of the Carbon Fiber 2015 ConferenceKnoxville TN USA December 2015

[6] M Kuhnel and T Kraus ldquo)e global cfrp market 2016rdquo inProceedings of the Experience Composites 2016 ConferenceAugsburg Germany September 2016

[7] European Parliament Council Directive 200053EC (End-of-Life Vehicles) Official Journal of the European Union L269September 2000

[8] European Parliament Council Directive 20105UE (Industrialemissions) Official Journal of the European Union L334December 2010

[9] F Meng J McKechnie T A Turner and S J PickeringldquoEnergy and environmental assessment and reuse of fluidizedbed recycled carbon fibresrdquo Composites Part A AppliedScience and Manufacturing vol 100 pp 206ndash214 2017

[10] A O Nunes L R Viana P-M Guineheuc et al ldquoLife cycleassessment of a steam thermolysis process to recover carbonfibers from carbon fiber-reinforced polymer wasterdquo In-ternational Journal of Life Cycle Assessment vol 22 no 11pp 1ndash14 2017

[11] R A Witik R Teusher V Michaud C Ludwig andJ-A Manson ldquoCarbon fibre reinforced composite waste anenvironmental assessment of recycling energy recovery andlandfillingrdquo Composites Part A Applied Science andManufacturing vol 49 pp 89ndash99 2013

[12] F Cansell C Aymonier C Morin and A Loppinet-SeranildquoNear and supercritical solvolysis of carbon fibre reinforcedpolymers (CFRPs) for recycling carbon fibers as a valuableresource state of the artrdquo Journal of Supercritical Fluidsvol 66 pp 232ndash240 2012

[13] S Pimenta and S T Pinho ldquoRecycling carbon fibre reinforcedpolymers for structural applications technology review andmarket outlookrdquo Waste Management vol 31 no 2 pp 378ndash392 2011

[14] G Oliveux L O Dandy and G A Leeke ldquoCurrent status ofrecycling of fibre reinforced polymers review of technologiesreuse and resulting propertiesrdquo Progress in Materials Sciencevol 72 pp 61ndash99 2015

[15] R Pinero-Hernanz J Garcia-Serna C Dodds et alldquoChemical recycling of carbon fibre composites using alcoholsunder subcritical and supercritical conditionsrdquo Journal ofSupercritical Fluids vol 46 no 1 pp 83ndash92 2008

[16] G Jiang S J Pickering E H Lester et al ldquoCharacterization ofcarbon fibres recycled from carbon fibreepoxy resin com-posites using supercritical n-propanolrdquo Composites Scienceand Technology vol 69 no 2 pp 192ndash198 2009

[17] J R Hyde E Lester S Kingman S Pickering andK H Wong ldquoSupercritical propanol a possible route tocomposite carbon recovery a viability studyrdquoComposites PartA Applied Science and Manufacturing vol 37 no 11pp 2171ndash2175 2011

[18] H Yan C-X Lu D Jing et al ldquoRecycling of carbon fibers inepoxy resin composites using supercritical 1-propanolrdquo NewCarbon Materials vol 31 no 1 pp 46ndash54 2016

[19] R Pinero-Hernanz C Dodds J Hyde et al ldquoChemicalrecycling of carbon fibre reinforced composites in nearcriticaland supercritical waterrdquo Composites Part A Applied Scienceand Manufacturing vol 39 no 3 pp 454ndash461 2008

[20] I Okajima K Yamada T Sugeta and T Sako ldquoDe-composition of epoxy resin and recycling of CFRP withsub- and supercritical waterrdquo Kagaku Kogaku Ronbunshuvol 28 no 5 pp 553ndash558 2002

[21] L Henry A Schneller J Doerfler et al ldquoSemi-continuous flowrecycling method for carbon fibre reinforced thermoset poly-mers by near- and supercritical solvolysisrdquo Polymer Degradationand Stability vol 133 pp 264ndash273 2016


[22] A Torres I de Marco B M Caballero et al ldquoRecycling bypyrolysis of thermoset composites characteristics of theliquid and gaseous fuels obtainedrdquo Fuel vol 79 no 8pp 897ndash902 2000

[23] J Yang J Liu W Liu J Wang and T Tang ldquoRecycling ofcarbon fibre reinforced epoxy resin composites under variousoxygen concentrations in nitrogenndashoxygen atmosphererdquoJournal of Analytical and Applied Pyrolysis vol 112pp 253ndash261 2015

[24] M A Nahil and P T Williams ldquoRecycling of carbon fibrereinforced polymeric waste for the production of activatedcarbon fibresrdquo Journal of Analytical and Applied Pyrolysisvol 91 no 1 pp 67ndash75 2011

[25] E Lester S Kingman K H Wong et al ldquoMicrowave heatingas a means for carbon fibre recovery from polymer com-posites a technical feasibility studyrdquoMaster Research Bulletinvol 39 no 10 pp 1549ndash56 2004

[26] D Akesson Z Foltynowicz J Christeen and M SkrifvarsldquoMicrowave pyrolysis as a method of recycling glass fibre fromused blades of wind turbinesrdquo Journal of Reinforced Plasticsand Composites vol 31 no 17 pp 1136ndash42 2012

[27] P Evangelopoulos E Kantarelis andW Yang ldquoExperimentalinvestigation of pyrolysis of printed circuit boards for energyand materials recovery under nitrogen and steam atmo-sphererdquo Energy Procedia vol 105 pp 986ndash991 2017

[28] S Kumagai T Hosaka T Kameda and T Yoshioka ldquoPy-rolysis and hydrolysis behaviors during steam pyrolysis ofpolyimiderdquo Journal of Analytical and Applied Pyrolysisvol 120 pp 75ndash81 2016

[29] E P Onal B Bureau Uzun and A E Putun ldquoSteam pyrolysisof an industrial waste for bio-oil productionrdquo Fuel ProcessingTechnology vol 92 no 5 pp 879ndash885 2011

[30] S Y Ye A Bounaceur Y Soudais and R Barna ldquoParameteroptimization of the steam thermolysis a process to recovercarbon fibers from polymer-matrix compositesrdquo Waste andBiomass Valorization vol 4 no 1 pp 73ndash86 2013

[31] S Y Ye Valorisation de dechets composites a matrices poly-meriques renforcees de fibres de carbone par un procede devapo-thermolyse PhD thesis University of Toulouse Tou-louse France 2012

[32] K-W Kim H-M Lee J-H An et al ldquoRecycling andcharacterization of carbon fibers from carbon fiber reinforcedepoxy matrix composites by a novel super-heated-steammethodrdquo Journal of Environmental Management vol 203pp 872ndash879 2017

[33] J Shi J Kato L Bao and K Kemmochi ldquo)e mechanicalproperty of recycled fiber reinforced polymer composites bysuperheated steamrdquo Applied Mechanics and Materials vol 339pp 687ndash690 2013

[34] M RrsquoMili N Godin and J Lamon ldquoFlaw strength distri-butions and statistical parameters for ceramic fibers thenormal distributionrdquo Physical Review E vol 85 no 5pp 1106ndash1112 2012

[35] M RrsquoMili V Massardier P Merle et al ldquo)e effect of thermalexposure on the strength distribution of B4C coated carbonfibersrdquo Carbon vol 37 no 1 pp 129ndash145 1999

[36] L Balea G Dusserre and G Bernhart ldquoMechanical behav-iour of plain-knit reinforced injected composites effect ofinlay yarns and fibre typerdquo Composites Part B Engineeringvol 56 pp 20ndash49 2014

[37] ASTM D 3379-75 Standard Test Method for TensileStrength and Youngrsquos Modulus for High-Modulus FilamentMaterials ASTM International West Conshohocken PAUSA 1989

[38] M RrsquoMili T Bouchaour and P Merle ldquoEstimation ofWeibull parameters from loose-bundle testsrdquo CompositesScience and Technology vol 56 no 7 pp 831ndash834 1996

[39] M RrsquoMili and M Murat ldquoCaracterisation des fibres paramelioration de lrsquoessai sur meches avec mesure directe de ladeformationrdquo Comptes Rendus de lrsquoAcademie des Sciences-Series IIB-Mechanics-Physics-Chemistry-Astronomy vol 324pp 355ndash364 1997

[40] HexcelHexTow AS4C carbon fiber Technical datasheet 2010[41] J L )omason ldquoOn the application of Weibull analysis to

experimentally determined single fibre strength distributionsrdquoComposites Science and Technology vol 80 pp 77ndash74 2013

[42] M RrsquoMili and J Lamon ldquoInvestigation of subcritical crackgrowth using load relaxation tests on fiber bundlesrdquo ActaMateriala vol 59 no 7 pp 2850ndash2857 2011

[43] G G Tibbetts and C P Beetz ldquoMechanical properties ofvapour-grown carbon fibersrdquo Journal of Physics D AppliedPhysics vol 20 no 3 pp 292ndash297 1987

[44] T Tagawa and T Miyata ldquoSize effect on tensile strength ofcarbon fibersrdquo Materials Science and Engineering A vol 238no 2 pp 336ndash342 1997

[45] M Huson J S Church A Kafi et al ldquoHeterogeneity ofcarbon fibrerdquo Carbon vol 68 pp 240ndash249 2014

[46] S Pimenta and S T Pinho ldquo)e effect of recycling on themechanical response of carbon fibres and their compositesrdquoComposites Structures vol 94 no 12 pp 3669ndash3684 2012

[47] K Stoeffler S Andielic N Legros J Roberge and S SchougaardldquoPolyphenylene sulfide (PPS) composites reinforced withrecycled carbon fiberrdquo Composites Science and Technologyvol 84 no 29 pp 65ndash71 2013

[48] D W N Feng X Wang and DWu ldquoSurface modification ofrecycled carbon fibre and its reinforcement effect on nylon 6composites mechanical properties morphology and crys-tallization behaviorsrdquo Current Applied Physics vol 13 no 9pp 2038ndash2050 2013


CorrosionInternational Journal of

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Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

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Advances inPhysical Chemistry


BioMed Research InternationalMaterials

Journal of


Na

nom

ate

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ls


Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

Research ArticleMechanical Characterization of Carbon Fibres Recycled by SteamThermolysis A Statistical Approach

M Boulanghien 123 M RrsquoMili4 G Bernhart1 F Berthet1 and Y Soudais2

1Institut Clement Ader (ICA) Universite de Toulouse CNRS Mines Albi UPS INSA ISAE-SUPAERO Campus Jarlard81013 Albi CT Cedex 09 France2Universite de Toulouse Mines Albi UMR CNRS 5302 Centre RAPSODEE Campus Jarlard F-81013 Albi cedex 09 France3Alpha Recyclage Composites 4 rue Jules Vedrines 31400 Toulouse France4INSA-Lyon MATEIS UMR CNRS 5510 Universite de Lyon 7 Avenue Jean Capelle 69621 Villeurbanne France

Correspondence should be addressed to M Boulanghien mboulangmines-albifr

Received 16 March 2018 Accepted 23 April 2018 Published 20 May 2018

Academic Editor Akihiko Kimura

Copyright copy 2018 M Boulanghien et al )is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

)e recent development of technologies for recycling carbon fibre reinforced plastics (CFRPs) leads to the need to evaluate themechanical response of recycled carbon fibres As these fibres are likely to be degraded during the recycling treatment it is veryimportant to determine their tensile residual properties so as to evaluate their ability as reinforcement for new compositematerials Carbon fibres reclaimed by a steam-thermal treatment applied to degrade the epoxy resin matrix of a CFRP are hereanalysed Two conditions were chosen so as to reach two degradation efficiency levels of the steam thermolysis Several carbonfibre samples were selected for mechanical testing carried out either on single filaments using single fibre tensile tests or on fibretows using bundle tensile tests It is shown that the single fibre tensile test leads to a wide variability of statistical parametersderived from the analysis Bundle tensile tests results were able to indicate that fibre strength of recycled carbon fibre is similar tocorresponding as-received carbon fibres thanks to a statistically relevant database Wide number of tested filaments enabledindeed to obtain low scatters

1 Introduction

Carbon fibre reinforced plastics (CFRPs) have been widelyused these last years in many industrial sportive andtransport applications especially for their low weight andhigh strength )e global carbon fibre market is expected toreach high annual growth rates until the next few yearsAlthough the current global demand for carbon fibre 82400tons per year is lower than expected in last yearrsquos marketreports [1 2] it is still expected to grow at a minimal annualrate of 90 Global demand in carbon fibres is expected toreach 116000 tons per year in 2021 for the less optimisticscenario [3] whereas other projections estimate a 150200tons demand [4 5] In addition the carbon fibre reinforcedcomposites market obviously shows very similar growthtrends While in 2013 the global demand for this kind of

material was 72000 tons recent reports expect this marketto reach a 191000 tons demand by 2022 [6])e high growthperspectives of wind turbines and aerospace industries canmainly explain the intensification in using CFRP as theirrecent introduction in the automotive industry )is dra-matic increase in using carbon fibre means that the quantityof generated waste will also rise significantly either as an off-cut or as an end-of-life composite product )us it appearsto be critical to develop suitable composite recycling tech-nologies that could offer interesting environmental andeconomic perspectives If the environmental and socialresponsibilities are the first arguments for such developmentefforts market economics is still a key factor Consideringthat the carbon fibre marketrsquos potential is clearly affected bythe high price of carbon fibre although its production ca-pacity is nowadays growing there is a huge opportunity for

HindawiAdvances in Materials Science and EngineeringVolume 2018 Article ID 8630232 10 pageshttpsdoiorg10115520188630232










P 1minus exp minusV

V01113888 1113889

εε0

1113888 1113889

m

1113890 1113891 (1)





f(ε) 1

S2π


2S21113890 1113891

PN(Ele ε) 1113946ε

0f(ε) dε

(2)






















Removable crucible


Composite samples


Steam

Nitrogen

Heating zone









4 Results







Ic μminus 202SN

radic μ + 202SN

radic[ ] (5)





VF mdash 71 (07)RF400 95 69 (07)RF500 gt99 69 (07)

Fibre bundle

Extensometer

Tensile grip







Fibresamples




VF 3776 547 146RF400 3272 672 179RF500 3610 540 144

4000

3000

2000

1000

0

Appl

ied

stres

s (M

Pa)

00 01 02 03 04 05 06 07 08Displacement (mm)

VFRF400RF500


(a) (b)


(a) (b)







3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]


(a)

3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]



(b)


2

4

6

8

10

Failu

re ev

ents




100

200

300

400

Load

(N)

00 05 10 15 20 25Strain ()






5 Discussion



6 Conclusion


4500

4000

3500

3000

2500

Mea

n str

engt

h (M

Pa)



Bundle tensiletest



Samplenumber





1 2940 3852 591 182 2615 3849 598 193 2850 3864 644 19


Fibresamples





VF 3240 3864 573 20RF400 3390 3657 437 15RF500 2940 3852 591 19




Data Availability




Acknowledgments


References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls













P 1minus exp minusV

V01113888 1113889

εε0

1113888 1113889

m

1113890 1113891 (1)





f(ε) 1

S2π


2S21113890 1113891

PN(Ele ε) 1113946ε

0f(ε) dε

(2)






















Removable crucible


Composite samples


Steam

Nitrogen

Heating zone









4 Results







Ic μminus 202SN

radic μ + 202SN

radic[ ] (5)





VF mdash 71 (07)RF400 95 69 (07)RF500 gt99 69 (07)

Fibre bundle

Extensometer

Tensile grip







Fibresamples




VF 3776 547 146RF400 3272 672 179RF500 3610 540 144

4000

3000

2000

1000

0

Appl

ied

stres

s (M

Pa)

00 01 02 03 04 05 06 07 08Displacement (mm)

VFRF400RF500


(a) (b)


(a) (b)







3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]


(a)

3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]



(b)


2

4

6

8

10

Failu

re ev

ents




100

200

300

400

Load

(N)

00 05 10 15 20 25Strain ()






5 Discussion



6 Conclusion


4500

4000

3500

3000

2500

Mea

n str

engt

h (M

Pa)



Bundle tensiletest



Samplenumber





1 2940 3852 591 182 2615 3849 598 193 2850 3864 644 19


Fibresamples





VF 3240 3864 573 20RF400 3390 3657 437 15RF500 2940 3852 591 19




Data Availability




Acknowledgments


References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls






f(ε) 1

S2π


2S21113890 1113891

PN(Ele ε) 1113946ε

0f(ε) dε

(2)






















Removable crucible


Composite samples


Steam

Nitrogen

Heating zone









4 Results







Ic μminus 202SN

radic μ + 202SN

radic[ ] (5)





VF mdash 71 (07)RF400 95 69 (07)RF500 gt99 69 (07)

Fibre bundle

Extensometer

Tensile grip







Fibresamples




VF 3776 547 146RF400 3272 672 179RF500 3610 540 144

4000

3000

2000

1000

0

Appl

ied

stres

s (M

Pa)

00 01 02 03 04 05 06 07 08Displacement (mm)

VFRF400RF500


(a) (b)


(a) (b)







3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]


(a)

3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]



(b)


2

4

6

8

10

Failu

re ev

ents




100

200

300

400

Load

(N)

00 05 10 15 20 25Strain ()






5 Discussion



6 Conclusion


4500

4000

3500

3000

2500

Mea

n str

engt

h (M

Pa)



Bundle tensiletest



Samplenumber





1 2940 3852 591 182 2615 3849 598 193 2850 3864 644 19


Fibresamples





VF 3240 3864 573 20RF400 3390 3657 437 15RF500 2940 3852 591 19




Data Availability




Acknowledgments


References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls










Removable crucible


Composite samples


Steam

Nitrogen

Heating zone









4 Results







Ic μminus 202SN

radic μ + 202SN

radic[ ] (5)





VF mdash 71 (07)RF400 95 69 (07)RF500 gt99 69 (07)

Fibre bundle

Extensometer

Tensile grip







Fibresamples




VF 3776 547 146RF400 3272 672 179RF500 3610 540 144

4000

3000

2000

1000

0

Appl

ied

stres

s (M

Pa)

00 01 02 03 04 05 06 07 08Displacement (mm)

VFRF400RF500


(a) (b)


(a) (b)







3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]


(a)

3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]



(b)


2

4

6

8

10

Failu

re ev

ents




100

200

300

400

Load

(N)

00 05 10 15 20 25Strain ()






5 Discussion



6 Conclusion


4500

4000

3500

3000

2500

Mea

n str

engt

h (M

Pa)



Bundle tensiletest



Samplenumber





1 2940 3852 591 182 2615 3849 598 193 2850 3864 644 19


Fibresamples





VF 3240 3864 573 20RF400 3390 3657 437 15RF500 2940 3852 591 19




Data Availability




Acknowledgments


References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls









4 Results







Ic μminus 202SN

radic μ + 202SN

radic[ ] (5)





VF mdash 71 (07)RF400 95 69 (07)RF500 gt99 69 (07)

Fibre bundle

Extensometer

Tensile grip







Fibresamples




VF 3776 547 146RF400 3272 672 179RF500 3610 540 144

4000

3000

2000

1000

0

Appl

ied

stres

s (M

Pa)

00 01 02 03 04 05 06 07 08Displacement (mm)

VFRF400RF500


(a) (b)


(a) (b)







3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]


(a)

3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]



(b)


2

4

6

8

10

Failu

re ev

ents




100

200

300

400

Load

(N)

00 05 10 15 20 25Strain ()






5 Discussion



6 Conclusion


4500

4000

3500

3000

2500

Mea

n str

engt

h (M

Pa)



Bundle tensiletest



Samplenumber





1 2940 3852 591 182 2615 3849 598 193 2850 3864 644 19


Fibresamples





VF 3240 3864 573 20RF400 3390 3657 437 15RF500 2940 3852 591 19




Data Availability




Acknowledgments


References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls








Fibresamples




VF 3776 547 146RF400 3272 672 179RF500 3610 540 144

4000

3000

2000

1000

0

Appl

ied

stres

s (M

Pa)

00 01 02 03 04 05 06 07 08Displacement (mm)

VFRF400RF500


(a) (b)


(a) (b)







3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]


(a)

3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]



(b)


2

4

6

8

10

Failu

re ev

ents




100

200

300

400

Load

(N)

00 05 10 15 20 25Strain ()






5 Discussion



6 Conclusion


4500

4000

3500

3000

2500

Mea

n str

engt

h (M

Pa)



Bundle tensiletest



Samplenumber





1 2940 3852 591 182 2615 3849 598 193 2850 3864 644 19


Fibresamples





VF 3240 3864 573 20RF400 3390 3657 437 15RF500 2940 3852 591 19




Data Availability




Acknowledgments


References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls








3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]


(a)

3

2

1

0

ndash1

ndash2

ndash3

ndash4

ndash5

Ln[ndash

Ln(1

ndashP)

]

76 78 80 82 84 86Ln[σ (MPa)]



(b)


2

4

6

8

10

Failu

re ev

ents




100

200

300

400

Load

(N)

00 05 10 15 20 25Strain ()






5 Discussion



6 Conclusion


4500

4000

3500

3000

2500

Mea

n str

engt

h (M

Pa)



Bundle tensiletest



Samplenumber





1 2940 3852 591 182 2615 3849 598 193 2850 3864 644 19


Fibresamples





VF 3240 3864 573 20RF400 3390 3657 437 15RF500 2940 3852 591 19




Data Availability




Acknowledgments


References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





5 Discussion



6 Conclusion


4500

4000

3500

3000

2500

Mea

n str

engt

h (M

Pa)



Bundle tensiletest



Samplenumber





1 2940 3852 591 182 2615 3849 598 193 2850 3864 644 19


Fibresamples





VF 3240 3864 573 20RF400 3390 3657 437 15RF500 2940 3852 591 19




Data Availability




Acknowledgments


References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls






Data Availability




Acknowledgments


References





















































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls


































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls






Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




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