DEVELOPMENT OF HIGH PERFORMANCE BIO-COMPOSITES BASED ON FURAN BIO-RESINS FOR VEHICLE PANELS

Transcription

1 DEVELOPMENT OF HIGH PERFORMANCE BIO-COMPOSITES BASED ON FURAN BIO-RESINS FOR VEHICLE PANELS S. Ginnis 1 E. Arnold 2 H.E. Hoydonckx 3 B.M Weger 2 R.H. Mrtin 1 1 MERL Ltd. Wilbury Wy Hitchin Hertfordshire SG4 0TW UK 2 NetComposites Ltd. Tpton Prk Innovtion Centre Brimington Rod Chesterfield S41 0TZ UK 3 TrnsFurns Chemicls bvb. Industrieprk Leukrd 2 B-2440 Geel BELGIUM ABSTRACT Composite mterils derived from renewble sustinble sources hve received significnt interest in recent yers due to the depletion of the erth s resources nd the incessnt rise in the price of oil. Nturl fibres such s hemp flx jute nd kenf re lredy used in significnt quntities to reinforce conventionl polymers lthough the fibres tend to be short nd rndomly oriented so mechnicl performnce is limited. A number of bio-derived resins re under development but re not yet redy for commercil ppliction. These shortflls re being ddressed by Europen Sixth Frmework Progrmme Project clled BIOCOMP which ims to develop high-performnce composite mterils mde entirely from renewble resources. As prt of this project novel furn thermoset resins derived from furfuryl lcohol hve been developed suitble for use in trditionl composite mnufcturing processes. These furn resins hve high temperture stbility good fire resistnce nd excellent chemicl resistnce nd re potentil sustinble lterntive to epoxy or phenolic resin systems. In ddition qusi-continuous ligned nturl fibre reinforcements hve been obtined by using low-twist nturl fibre yrns nd fbrics. Test pnels hve been produced from glss fibre-reinforced furn resin using hnd ly-up nd vcuum bgging processes nd from ligned flx fibre-reinforced furn resin using prepreg technique with vcuum nd press consolidtion. These pnels hve been subjected to rnge of mechnicl nd physicl tests nd the results compred to conventionl composite mterils such s glss fibre-reinforced unsturted polyester. The bio-bsed mteril exhibited some promising chrcteristics. Prototype vehicle pnels hve been produced from flx fibre-reinforced furn glss fibre reinforced-furn nd glss fibre-reinforced unsturted polyester nd these hve been evluted nd compred to the performnce requirements. 1. INTRODUCTION The use of fibre-reinforced plstic composites in the utomotive industry hs grown significntly in recent yers due to their low weight design flexibility corrosion resistnce nd cost-effectiveness in prticulr for low volume niche vehicles. Glss fibre is commonly used s the reinforcement often in the form of rndom chopped strnd mts nd unsturted polyester resin is populr mtrix polymer. Hnd ly up resin trnsfer moulding nd vcuum infusion re ll well estblished processing techniques well suited to the mnufcture of composite vehicle prts such s exterior nd interior pnels. Currently there is significnt drive to switch to more sustinble nd renewble mterils whilst reducing weight nd cost. For exmple density nd cost cn be reduced by replcing glss fibre with nturl fibres such s hemp flx or kenf 1-2. The specific stiffness which is the stiffness s function of density of nturl fibres exceeds tht of glss fibres 3. Nturl fibre composites hve found pplictions in the utomotive industry lthough these re lrgely for non-structurl prts such s interior pnels. This is prtly due to the composites being mnufctured from short non-woven fibre mts 4 which leds to products tht hve limited mechnicl properties. In ddition the nturl fibres re generlly used with conventionl resins such s unsturted polyester nd polypropylene 5-6 mening tht only the fibres re from renewble sources. 1

2 Thermoplstic bio-resins such s polylctic cid (PLA) polyhydroxybutyrte (PHB) nd strch-bsed polymers re currently being developed nd used primrily for food pckging 7. Much of their ppel in the pckging industry lies in their biodegrdble nture. Some thermosetting bio-resins derived from plnt oils such s soyben 8-9 nd linseed 10 re currently under development but re not redy for commercil ppliction. New clsses of engineering composite mterils from renewble resources re being developed nd commercilised through BIOCOMP n Integrted Project for SMEs supported by the Europen Commission through the Sixth Frmework Progrmme (FP6). A primry objective of the BIOCOMP project is to develop high-performnce composite mterils entirely derived from renewble sources using new fmily of furn-bsed resins reinforced with continuous ligned nturl fibres. The furn-bsed resins re being developed by TrnsFurns Chemicls under the trdenmes BioRez nd Furolite. The resins re synthesized from pre-polymers of furfuryl lcohol which is derived from biomss sources including sugr cne bgsse (Figure 1). Furn resins offer number of interesting properties such s high stiffness fire resistnce nd chemicl resistnce to orgnic nd inorgnic cids. Figure 1: Production route of furfuryl lcohol prepolymer resin from hemicellulosic biomss. This pper discusses work undertken during the BIOCOMP project to develop highperformnce furn-bsed bio-composites for rnge of pplictions including utomotive prts bsed on furn-bsed resins re being developed by TrnsFurns Chemicls. An externl pnel from low-volume utility vehicle ws used to demonstrte nd evlute the mterils ginst specifiction. NetComposites Ltd. developed the mnufcturing process nd produced test smples nd prototype pnels nd MERL Ltd. conducted ll the evlution tests. Typicl requirements for this type of component include mechnicl integrity impct resistnce environmentl resistnce good surfce finish cceptble cost t low production volumes (e.g. 200/yer). 2. MATERIALS AND PROCESSING Two grdes of furn resin hve been investigted in this study: (1) 2-prt low viscosity resin suitble for use with glss fibres nd (2) 1-prt prepreg system for use with nturl fibres. The 2-prt resin includes n cid-bsed ctlyst dded t 6 wt% which ws found to degrde the nturl fibres during initil tests. A ph neutrl resin ws therefore developed for use with nturl fibres. Due to the higher viscosity of this modified resin the resin hd to be dissolved in solvent in order to impregnte the fibres properly. After impregntion the solvent ws evported off leving furn-flx prepreg contining 40 wt% fibres. 2

3 Stndrd Glss fibre reinforced polyester (GRP) mterils were mnufctured nd tested for benchmrk comprison purposes using n unsturted polyester resin nmely Crystic 489PA from Scott Bder Ltd. with 2 wt% MEKP ctlyst. A powder bound glss fibre chopped strnd mt (CSM) 450gsm ws used s the reinforcement in the furn-glss system. An emulsion bound glss fibre chopped strnd mt 450gsm ws used s the reinforcement in the polyester-glss system. A unidirectionl flx stitched fbric with cotton stitch yrn ws used in the prepreg. The fbric (230gsm) ws mde from loosely twisted yrns in order to improve resin impregntion nd to mintin fibre lignment. Both flt test pnels nd prototype vehicle pnels were produced from furn-glss polyester-glss nd furn-flx. The vehicle pnel tool ws single cvity epoxy bord mould. 2.1 Glss fibre/furn (BioCompA) Four lyers of 450gsm glss CSM nd the 2-prt furn resin were lid up into the prepred mould using brushes nd rollers. Being development system the furn resin ws not formulted to include thixotropic or low-shrink dditives. Therefore following lmintion the prts were vcuum bgged nd vcuum of 0.9 br ws pplied to the system during curing to improve prt qulity. This lso resulted in prt with higher fibre volume frctions thn stndrd hnd ly-up prt (32 wt% resin). The prts were cured t room temperture for 140 min 50 C for 45 min nd 80 C for 45 min nd then post-cured t 80 C overnight (pproximtely 18 hrs). Figure 2: Prototype furn-glss fibre exterior vehicle pnel. 2.2 Glss fibre/polyester (GRP) Four lyers of glss CSM nd polyester resin were lminted into the mould s bove vcuum bgged nd cured overnight t room temperture (pproximtely 18 hrs) followed by 3 hour post-cure t 80 C. 2.3 Flx fibre/furn (BioCompB) Four lyers of furn-flx prepreg were lid into the prepred mould in blnced crossply ly up 0/90 S. A vcuum bg ws pplied to the system nd the prt ws cured in n oven for 15 minutes t 150 C. Approximtely 20% by weight resin ws lost through resin bleeding resulting in prts with finl fibre content of pproximtely 60 wt% nd higher levels of porosity thn desirble. Further development is required to reduce the resin bleeding. 3

4 3. EXPERIMENTAL PROCEDURES A comprehensive experimentl progrmme ws set-up in order to chrcterize the behviour of the three mterils considered in this work. Mechnicl nd physicl tests were performed to ssess some key elements of the behviour of the mterils nd these re presented in detil in the following sections. 3.1 Exposure to fluids A utility vehicle pnel will be exposed to number of fluids nd environments while in service. Therefore number of tests were performed to investigte the behviour of the mterils when exposed to these fluids. Flt squre mm test pieces were cut from the mnufctured pnels nd immersed in the following fluids: (1) Motor oil 10W30 (2) Hydrulic oil 10W40 (3) Diesel oil (4) Antifreeze fluid (ethylene glycol 99%) (5) Windscreen wsh (6) Pesticide nd (7) Distilled wter. In prllel to mss chnge Brcol hrdness ws lso mesured for the GRP nd the BioCompA mterils. However due to the very high surfce roughness Brcol hrdness could not be mesured for the BioCompB. All immersions took plce t mbient lbortory conditions (23±2 C 55±5 % RH) with test pieces being weighed t regulr intervls. Smples were immersed for period of up to 2000 hrs. Wter immersion of GRP nd BioCompA lsted for pproximtely 3600 hrs. Aprt from the squre smples dumbbell shped tensile test pieces were lso immersed in ll seven fluids in order to ssess the effect the fluid uptke (sturtion level) on the bsic mechnicl properties. A number of smples for fstener pull through nd impct resistnce tests were immersed in wter over period of time nd their response ws lso ssessed nd compred to tht of un-ged smples. 3.2 Tensile tests Tensile tests were performed following the ISO Interntionl Stndrd 11. Dumbbell shped test pieces (specimen type 1B) were mchined from the mnufctured flt pnels using CNC fcility. All tests were performed on ZWICK Z250 test frme using 5 kn lod cell nd crosshed speed of 5 mm/min. Tensile tests were performed on un-ged (s received) smples s well s on smples exposed for certin period of time to number of fluids s described bove. 3.3 Fstener pull through tests Figure 3: Experimentl set-up detils for fstener pull through tests. 4

5 Since the instlltion of the prototype utility vehicle pnel will involve the use of number of fsteners the fstener pull through response of the mterils ws investigted. For the experimentl work ASTM D Stndrd ws dopted. Flt mm test specimens were cut from the pnels. A 10 mm clernce hole ws drilled t the centre of the test piece nd n M10 fstener instlled. The experimentl set-up for the test cn be seen in Figure 3. All tests were performed t mbient lbortory conditions utilizing ZWICK test frme nd using 5 kn lod cell. Loding ws pplied t rte of 5 mm/min. Tests were performed prior nd fter immersion in distilled wter to ssess the durbility of the mterils. 3.4 Impct tests One of the min in-service threts for utility vehicle pnel is impct due to rod debris vndlism etc. Thus impct resistnce ws investigted for ll the mterils. Drop weight impct tests were performed on rectngulr mm flt test specimens cut from the mnufctured pnels. Different impct energy (impct velocity) levels were chieved by ltering the drop height (0.3 to 1.2 m) of the 2.5 kg impctor mss. A hemisphericl impctor nose 10 mm in dimeter ws used for ll tests. A lod cell ttched to the impctor ws used to mesure the impct response of the mterils. Test specimens were clmped t four corners using toggle clmps on top of mm window frme. The experimentl set-up cn be seen in Figure 4. Due to the lrge difference in thickness (BioCompB pnels hd nominl thickness of 2 mm while GRP nd BioCompA ones 4 mm) different impct energy levels were pplied to the smples but the rtio of impct energy per unit thickness of the mteril ws kept constnt. Tests were performed on dry (s received) smples s well s on smples sturted with wter. Figure 4: Drop weight impct test set-up. 4. EXPERIMENTAL RESULTS 4.1 Exposure to fluids Results of the fluid exposure tests re given in Tble 1. The mss t equilibrium (sturtion level) is used s mens to quntify the effect of the vrious fluids on the three mterils under investigtion. GRP fluid bsorption levels were found to be very low nd in ll cses significntly lower thn BioCompA nd BioCompB. In one cse (immersion in nti-freeze) GRP 5

6 smples showed n erly mximum followed by continuous decrese in weight until they reched equilibrium t weight lower thn the initil one. Tht indicted significnt leching of constituents in the nti-freeze fluid. Both BioCompA nd BioCompB smples bsorbed considerble mount of the fluids with BioCompB reching 23.2% increse in weight following immersion in wter. The fluid bsorption behviour hs Fickin chrcteristics for wter nd windscreen wsh (Figure 5() nd (b)). The considerble difference between BioCompA nd BioCompB indicted tht the flx fibres lso bsorb gret mount of fluids during immersion. The initil furnflx mterils (BioCompB) hd higher porosity thn idel which my hve contributed to the reltively high fluid uptke results. The fluid immersion ws found to hve n effect on the surfce chrcteristics of the GRP nd BioCompA smples which leded to decrese in Brcol hrdness. Tble 1: Fluid mss uptke nd Brcol Hrdness test results Mss Chnge M % Mteril GRP BioCompA BioCompB Motor Oil 10w Hydrulic Oil 10w Diesel Anti-freeze Pesticide Windscreen wsh Distilled Wter All results for up to 2000 hrs immersion except GRP nd BioCompA in wter tht correspond to 3600 hrs 25 Wter 25 Windscreen Wsh 20 BioCompB 20 % 15 e g n h C 10 s M BioCompA % 15 e g n h C 10 s M BioComp BioCompA 5 GRP 5 GRP Time h 1/2 Time h 1/2 () (b) Figure 5: Plots of the mss chnge of the three mterils immersed in () wter nd (b) windscreen wsh. 4.2 Tensile tests Some bsic mechnicl dt for the three mterils re summrized in Tble 2 s mesured from uni-xil tensile tests. Young s modulus ws found to be very similr for the three mterils. However ultimte tensile strength nd strin to filure ws considerbly different. BioCompB ws found to hve the lowest strin to filure nd 6

7 tensile strength. The structure of the reinforcement mteril (bixil vs. rndom oriented fibres) will ply significnt role in the tensile response. The properties of the three mterils under considertion before nd fter immersion in vrious fluids re summrized in Tble 3. Tble 2: Mechnicl properties of the mterils tested (Men Vlues ± Stdev) Mteril Tensile Strength Young s Modulus Strin to Filure MP GP % GRP 131±27 9.2± ±0.2 BioCompA 93±8 7.2± ±0.3 BioCompB 0/90 S 64± ± ±0.1 Tble 3: Tensile strength nd Young s modulus of GRP BioCompA nd BioCompB fter immersion in vrious fluids Mteril GRP BioCompA BioCompB 0/90 S Tensile Strength MP Young s Modulus GP Tensile Strength MP Young s Modulus GP Tensile Strength MP Young s Modulus GP Before immersion 131±27 9.2±1.1 93±8 7.2±1.0 64± ±0.8 Motor Oil 10w30 96± ±0.4 86± ±0.3 64± ±0.7 Hydrulic Oil 10w40 98± ±0.5 91± ±0.4 53± ±0.6 Diesel 99± ±0.1 89± ±0.4 55± ±0.5 Anti-freeze 101± ±0.6 89± ±0.6 56± ±0.4 Pesticide 94± ±0.5 79± ±0.3 61± ±0.3 Windscreen wsh 95± ±0.1 80± ±0.4 65± ±0.1 Distilled Wter 99± ±0.2 85± ±0.4 61± ± P 8.0 G s lu u d o M % r e ilu f to in tr S Mss Chnge % 0.0 Figure 6: Vrition of modulus nd strin to filure with mss chnge during immersion in vrious fluids for BioCompB. Stiffness of the GRP mteril ppers to be slightly reduced by the immersion in the vrious fluids nd the decrese in modulus ws found to be pproximtely the sme for ll fluids. Tensile strength ws reduced to greter extent but gin similr results were obtined for ll fluids. BioCompA followed similr trend nd only pesticide windscreen wsh nd wter cused more noticeble drop in strength nd modulus. 7

8 The effect of fluid exposure is more evident in the mechnicl behviour of BioCompB. Lrge fluid uptkes (pesticide windscreen wsh nd wter) resulted in more ductile mteril with considerble loss in stiffness (Figure 6). 4.3 Fstener pull through nd bering strength tests The experimentl results of the fstener pull through tests prior to (un-ged) nd fter wter immersion re presented in Figure 7. Photogrphs of some chrcteristic smples fter testing re presented in Figure N d 3000 o L m u 2000 im x M1000 GRP un-ged BioCompA un-ged BioCompB un-ged GRP wter BioCompA wter BioCompB wter Hole Dimeter / Thickness Figure 7: Experimentl mximum pull through lod plotted s function of the hole dimeter to thickness rtio for ech smple. () (b) (c) (d) Figure 8: Photogrphs of the fstener pull through filure mode of the three mterils; () GRP un-ged (b) BioCompA un-ged (c) BioCompB un-ged nd (d) BioCompB wter immersed smples. The results indicted no significnt difference between the GRP nd BioCompA in terms of mximum pull through lod. However the mode of filure for the two mterils ws mjorly different. GRP smples showed bending type filure with crcks inititing round the fstener nd propgting towrds the support of the smple while BioCompA smples presented pure pull thought filure mode (Figure 8() nd (b)). After wter immersion there ws slight drop in the mximum pull lod but no 8

9 pprent chnge in the mode of filure. BioCompB ws found to hve firly poor pull through strength. The un-ged smples behved in brittle mnner nd bending type filure occurred t n verge mximum lod of 520 N. After wter immersion the behviour of the mteril ws evidently more ductile (higher displcements to filure) nd the verge mximum lod incresed up to 680 N. The filure mode in this cse ws lso different (Figure 8(d)). The decrese in the fstener hole dimeter to thickness rtio is due to the increse in thickness of the wter immersed smples. 4.4 Impct tests The experimentl results for the drop weight impct tests re summrised in Figure 9(). The mximum impct force ws used to ssess the impct response of the mterils prior nd fter wter immersion. For similr energies (per unit thickness) the GRP smples showed mrginlly higher impct forces thn the BioCompA smples. The mximum impct force ws not found to be ffected by the wter immersion N 4000 x m F 3000 d o L t c 2000 p I m x 1000 M GRP BioCompA 4.0 N3.0 k d 2.0 o L t c p Im 1.0 GRP un-ged GRP wter BioCompA wter BioCompA unged Impct Energy / Thickness U /h J/mm Time sec () (b) Figure 9: () Vrition of mximum impct lod with normlized impct energy nd (b) Force-time history for GRP nd BioCompA before nd fter wter immersion. However it ws found tht wter immersed GRP smples showed higher impct durtion thn the un-ged ones (Figure 9(b)). Tht indictes higher levels of impct dmge for these smples (for the sme energy level) Figure 10(). This ws not observed for the cse of the BioCompA smples. In generl for these two mterils some locl indenttion t the front side ws found t high energy levels while significnt fibre frcture occurred t the bck side (Figure 10() nd (b)). () (b) (c) Figure 10: Photogrphs of the impct induced dmge on the three mterils; () bck side dmge of GRP (b) bck side dmge of BioCompA nd (c) front side dmge of BioCompB smples. 9

10 In the cse of BioCompB smples perfortion occurred even t very low energy levels. The filure ws found to be brittle nd the impct forces very low. The wter immersed smples showed similr impct behviour with evidence of less brittle filure thn the dry ones. Possible plsticiztion of the mterils due to the presence of wter s lso found from the tensile nd pull through tests could result in the observed behviour. 5. CONCLUSIONS There is gret potentil in using composites mde of sustinble nd renewble mterils. In the present study the mechnicl nd physicl behviour of mterils under development (glss fibre/furn nd flx fibre/furn) ws investigted nd compred to glss fibre/polyester benchmrk system. The requirements (strength stiffness impct resistnce chemicl resistnce etc) were set by the potentil use of these mterils to mnufcture utility vehicle pnels. The glss fibre/furn resin system could be good lterntive to the glss fibre/polyester system. Further development is needed for the cse of the fully renewble system (flx fibre/furn resin) in order to chieve the desired results. ACKNOWLEDGEMENTS This study ws undertken through BIOCOMP project n Integrted Project for SMEs supported by the Europen Commission through the Sixth Frmework Progrmme (Project No.NMP2-CT ) under the Contrct No The support of the project prtners is grtefully cknowledged in prticulr TrnsFurns Chemicls nd Celbor for supplying mterils nd Risø nd Giker for technicl ssistnce. REFERENCES 1- Oksmn K. Skrifvrs M. Selin J.-F. Nturl Fibres s Reinforcement in Polylctic Acid (PLA) Composites Composites Science nd Technology 2003;63: Bledzki A.K. Fruk O. Sperber V.E. Crs from Bio-Fibres Mcromoleculr Mterils nd Engineering 2006;291: Mdsen B. Thermoplstic Composites of Plnt Fibre Yrn-Mnufcturing nd Chrcteristion Coronet Regionl Seminr Roskilde Denmrk Reidel U. Nickel J. Herrmnn A. S. High Performnce Applictions of Plnt Fibres in Aerospce nd Relted Industries Nturl Fibres Performnce Forum Copenhgen Denmrk Hrgiti H. Rcz I. Development of Hemp Fibre-PP Nonwoven Composites By Zoltn Institute for Mterils Science nd Technology Budpest Hungry Dhkl H.N. Zhng Z.Y. Richrdson M.O.W. Effect of Wter Absorption on the Mechnicl Properties of Hemp Fibre Reinforced Unsturted Polyester Composites Composites Science nd Technology 2007;67: Vn de Velde K. Keikens P. Biopolymers: Overview of Severl Properties nd Consequences of their Applictions Polymer Testing 2002;21: Adekunle K. Skrifvrs M. Synthesis of Rective Soyben Oils for Use s Thermoset Resins in Composites Interntionl Sustinble Mterils Polymers & Composites Conference nd Explortory Workshop University of Wrwick United Kingdom Wool R.P. Sun Z.S. (Eds) Bio-Bsed Polymers nd Composites Elsevier Burlington Mosiewicki M. Borrjo J. Arnguren M.I. Mechnicl Properties of Woodflour / Linseed Oil Resin Composites Polymer Interntionl 2005;54: ISO Plstics - Determintion of Tensile properties Test Conditions for Isotropic nd Orthotropic Fibre-Reinforced Plstic Composites Interntionl Stndrds Orgniztion ASTM D7332 Stndrd Test Method for Mesuring the Fstener pull-through Resistnce of Fibre-Reinforced polymer Mtrix Composite ASTM Interntionl