Introduction. Keywords: aluminum alloy sheet, fire performance, mechanical property, wood-aluminum composite (WAC)

Transcription

1 Holzforschung 0; 69(8): Keyng Lu, *, Roert H. White, Feng Fu, Junfeng Hou, Yisheng Zhng, Neil Griins nd Zhiyong Ci* Reinforced hyrid wood-luminum composites with excellent fire performnce Astrct: The fire performnce of severl types of woodluminum composites (WAC) ws nlyzed y the smll verticl furnce test. The time needed to rech the temperture of 9 C/8 C (T 9 C/8 C ) nd the liner chr rte of 00 C (L 00 C ) were otined y evluting the fire performnce of WAC. The T 9 C/8 C vlues rnged from.6 to 44.8 min. The presence nd position of the luminum lloy sheet remrkly ffected the fire performnce of WAC. In ddition to n initil dely of 9 min, the L 00 C lso incresed when the luminum lloy sheet ws locted on the surfce. However, the times for 00 C only incresed slightly when the luminum lloy sheet ws in the middle. The initil dely oserved for the luminum lloy sheet on the surfce ws reduced y more thn 0% when the wood veneer ws locted on the surfce of the luminum lloy sheet. The mechnicl properties of WAC were lso investigted. It ws concluded tht the uniformity nd strength of different composites ws improved fter the lmintion of the luminum lloy sheet. In ddition, the modulus of elsticity of WAC qudrupled, nd the onding strength etween the luminum lloy sheet nd the oriented strnd ord (OSB) ws greter thn tht of the OSB. These uthors contriuted eqully to this work. We would like to dedicte this pper to Roert H. White, who pssed wy just efore the pper ws completed for sumission. Roert H. White plyed n essentil role in the reserch descried here, nd he is gretly missed. *Corresponding uthors: Keyng Lu, Reserch Institute of Wood Industry, Chinese Acdemy of Forestry, Beijing 0009, People s Repulic of Chin; nd USDA Forest Service, Forest Products Lortory, Mdison, WI 76-98, USA, e-mil: luky@cf.c.cn; Zhiyong Ci: USDA Forest Service, Forest Products Lortory, Mdison, WI 76-98, USA, e-mil: zci@fs.fed.us Roert H. White nd Neil Griins: USDA Forest Service, Forest Products Lortory, Mdison, WI 76-98, USA Feng Fu nd Yisheng Zhng: Reserch Institute of Wood Industry, Chinese Acdemy of Forestry, Beijing 0009, People s Repulic of Chin Junfeng Hou: Reserch Institute of Wood Industry, Chinese Acdemy of Forestry, Beijing 0009, People s Repulic of Chin; nd College of Engineering, Zhejing Agriculture nd Forestry University, Lin n 00, People s Repulic of Chin Keywords: luminum lloy sheet, fire performnce, mechnicl property, wood-luminum composite (WAC) DOI 0./hf Received Mrch 0, 04; ccepted Novemer 4, 04; previously pulished online Decemer 6, 04 Introduction Wood-sed composites possess n inherent flmmility nd often contriute to the propgtion of fires. Thus, the fire performnce of such composites plys n incresingly significnt role in their engineered structurl pplictions. Fire retrdnts nd other nonflmmle mterils (i.e., concrete nd metls) (Winndy et l. 008; Urso et l. 009; Zhng et l. 0) my lso improve their fire performnce in coting, lminting, or filling. To this purpose, mixture of clcite nd vrious fire retrdnts were pplied in the coting of medium-density fierord (MDF) pnels, nd the lowest oserved mss loss ws.% when coted with oric cid (Îstek et l. 0). Concrete ws mixed with timer joists to mnufcture timer-concrete composite floors, which could resist fire longer thn 60 min (Jmes et l. 009). Li et l. (004) showed tht the flme-retrding efficiency of wood plstic polymer composites (WPC) with high-density polyethylene (WPC HDPE ) incresed to 0.0 nd tht the limiting oxygen index ws 7.% fter the ddition of luminum hydroxide with weight rtio of 40%. Flmeretrdnt mterils remrkly improved the fire performnce of WPC. However, such composites re seldom in engineering structurl pplictions ecuse of their poor dimensionl stility, decy resistnce, nd strength. Wood-metl composites (WMC) re promising mterils ecuse of their high strength nd dimensionl stility. Most of the reserch on WMC focuses on chrcterizing the mechnicl properties, electromgnetic shielding, flme retrdncy, nd decortive vlues (Schnl et l. 009; Song nd Lm 0; Lu et l. 0). The fire performnce of WMC with surfce coting (White 98), reinforced joints (Moss et l. 009), nd metl plte connected mteril (White 98) ws lso investigted. Lminted Downlod Dte 9// :8 PM

2 08 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce veneer lumer joints were connected with metl pltes, which were covered with grphite phenolic spheres (GPS) (Suykto et l. 00), nd the results showed tht GPS (lrge or medium-sized sheet) delyed the temperture rise time to 60 C for t lest 60 min. The focus of the study of Erchinger et l. (00) ws the fire design of multiple sher steel-to-timer connections with slotted-in steel pltes nd steel dowels; the mteril resisted fire for 60 min due to the protection effect of timer ords or gypsum plster ords. Schffer (967) investigted the flme spred ehvior of thin plywood pnels with noncomustile inserts plced immeditely elow the fce veneers. The noncomustile inserts included 0.8 mm (/ in)-thick 04-T cld luminum lloy nd 0.0 mm (/000 in)- thick luminum foil. Incresing the thickness of the fce veneer from 0.4 mm (/60 in) to 0.9 mm (/8 in) incresed the flme spred index of the pnel. The 0.8-mm-thick luminum sheet insert significntly reduced the flme spred rte, ut the luminum foil did not. The luminum foil ws too thin to resist the pressure of the voltile gses from the wood, nd the foil did not lwys remin intct. As noted in severl U.S. ptent pplictions, erly fire doors consisted of wood core fced with metl sheeting. WMC, s engineered wood products, re widely used in lod-ering structures such s I-joists, studs, lrge roof spns, nd comprtment floors. Among metls, luminum lloy gined high levels of pulic interest due to its excellent properties of recyclility, formility, light weight, nd high strength (Hshim et l. 00; Fogle et l. 0). The literture concerning the fire performnce of wood-luminum composites (WAC) is scre. Aluminum lloy foils were overlid on MDF to prepre WAC, nd the results of cone clorimeter testing indicted decrese of effective het of comustion of 90.6% nd totl het relese of 96.6% (Yng 0). The fire performnce of wood-luminum lminted composites ws not yet tested. In this study, luminum lloy sheets were lminted to the oriented strnd ord (OSB) nd the wood veneer to mnufcture WAC. Their fire performnce ws investigted in smll verticl furnce in ccordnce with ASTM E 9. The mechnicl properties of WAC were tested in ccordnce with ASTM D The purpose of this study ws to provide insights nd estlish mthemticl model to understnd etter the fire performnce of severl types of WAC. Mterils nd methods Aluminum lloy sheets (00) were otined from McMster-Crr Supply Co. (Atlnt, USA). The mteril hs good weldility, formility, nd corrosion resistnce, nd it is similr to lloy 00 ut hs higher strength due to its mngnese content. The size of the luminum lloy sheet ws mm. Isocynte resin (MDI, RUBINATE 840) ws provided y Huntsmn Corportion (Slt Lke City, USA); color: drk rown; viscosity t C: 80 cps. This kind of resin is suited for hot pressing. Isoset WD-C0 resin ws provided y Ashlnd Specilty Chemicl Co. (Msschusetts, USA): color: white; viscosity t C; etween 800 nd 400 cps. Isoset CX-47 cross-linking gent ws lso provided y Ashlnd; color: lck; viscosity t C: etween 40 nd 60 cps. This kind of resin mixture is suited for cold pressing. The OSB with dimensions of mm (Home Depot, Mdison, WI, USA) ws the sis for the preprtion of the composite pnels. The resin in the OSB ws phenol formldehyde resin. The wood fce veneer ws.4 mm thick. Four types of composites were prepred s illustrted in Figure A: () control pnel without ny luminum lloy sheet, () composite with.6-mm-thick luminum lloy sheet plced on the surfce, (c) composite with.6-mm-thick luminum lloy sheet plced in the middle, nd (d) composite with thinner veneer plced on the () type of composites. Furthermore, the thickness of the OSB, luminum lloy sheet, nd wood veneer ws 6.,.6, nd.4 mm, respectively. For the hot-pressed composites, the press time ws 0 min t 0 C nd the pressure ws MP. The cold-pressed composites were prepred t pressure of MP for h. The resin usge for the composites ws 0 g m - for ech onding line. The luminum lloy sheet hs very high surfce free energy nd hs little or no chnce of remining clen for long s it oxidizes esily upon exposure to ir, the surfce is converted to lower energy level, nd the strength is deteriorted (Arrowsmith nd Clifford 98). Therefore, the sheets were rsively clened y snding to remove the wek oundry lyers of oxide nd scle, nd this tretment lso enhnced their mechnicl interlocking with the dhesive. The specimens were removed from the hot press nd stored in plstic gs efore fire testing to mintin similr moisture contents (MC) within the test specimens. The norml prctice of conditioning t C nd 0% reltive humidity ws not followed for time shortge. Moreover, it ws confirmed tht the metl fcings limit the moisture dsorption of the specimens. Proly, the metl fcings resulted in uneven moisture grdients within the specimens nd cused inconsistencies in the MC of specimens with nd without metl fcings. To keep the thermocouples intct, the specimens were not swed or cut. The specimen size ws 0 0 mm (0 0 in.). The specimens tested in the smll verticl furnce re listed in Tle. The tests were conducted in the Forest Products Lortory (FPL) smll verticl concrete furnce (customer-designed y Forest Products Lortory, Wisconsin, USA). The specimen sizes were considerly smller thn those required y the ASTM E9 stndrd. The verticl gs-fired furnce hd squre opening (0 0 mm ; i.e., 0 0 in) for the test specimen (Figure B). The furnce hd pipe outlets for dischrging the nturl gs from the furnce. A single-furnce thermocouple ws used to control the furnce, which ws in cpped metl pipe situted opposite the center of the test specimen in distnce of 0 mm ( in) from the exposed surfce. The flow of nturl gs ws controlled so tht the furnce temperture ws lso well controllle. Due to the plcement of the pipe outlets, the furnce thermocouple ws closer to the specimen surfce thn the mm (6 in) specified in ASTM E9. All ir for comustion ws dmitted y nturl drft through side vents ner the ottom of the furnce. Most tests were replicted three times. The thermocouples on the unexposed surfce were plced underneth the smll cermic fier pds. Downlod Dte 9// :8 PM

3 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce 09 A Thermocouple OSB Bck One lyer Bck Thermocouple Bck Thermocouple Aluminum lloy sheets Wood venter c Thermocouple Bck d Thermocouple B Figure (A) Construction of WAC nd position of thermocouples in the composites ( ck ws the surfce of the composite unexposed to fire during the smll verticl furnce test): () control pnels without ny luminum lloy sheet, ().6-mm-thick luminum lloy sheet plced in the middle, (c).6-mm-thick luminum lloy sheet plced on the surfce, nd (d).4-mm-thick wood veneer plced on the (c) type of composites. (B) FPL smll verticl furnce. The thermocouples were plced in the overll center of the 0 0 mm pnel nd in the center of ech qudrnt. Five thermocouples were plced etween ech lyer (Figure A). The thermocouples within or on the specimens were mde from 0. mm (0.0 in) dimeter (0-guge) chromel/lumel (type K) wires. These thermocouples enled the recording of the times for temperture increse to n verge of 9 C or to T mx of 8 C (shortly T 9 C/8 C ). This temperture increse time is one of the filure criteri in ASTM E9 (White 98). A series of models were estlished to nlyze the chr rte of wooden composites (White 00; Brusks 00; Tsi et l. 0). In this study, the seline of the chr lyers ws determined to e pproximtely 00 C in ccordnce with ASTM E9 fire exposure. Therefore, the times for temperture increse to 00 C (T 00 C ) were Downlod Dte 9// :8 PM

4 00 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce Tle Description of the specimens tested in smll verticl furnce. Composite Code No. of tests Type of pressing Thickness (mm) Tle Test results of the composites indicted. Composite X C (mm) Lyer no. Time to rech the T (min) 9 C/8 C 00 C c Eqution for clcultion of T 00 C (min) d C O+O+O Cold 8 H O+O+O Hot 8 CA A+O+O+O+A Cold HA A+O+O+O+A Hot HO O+A+O+A+O Hot HV V+A+O+O+O+A Hot A, luminum lloy sheet; C, cold pressing; H, hot pressing; O, OSB; nd V, wood veneer. Code indictes the pnel type. recorded. The chr rtes were clculted ssuming simple liner model of T 00 C divided y the distnce from the fire-exposed surfce (Tle ) (Schffer 967). The model for the OSB s n outer lyer (composites: C, H, nd HO) ws T = L X () 00 C 00 C C where T 00 C is the time to rech 00 C (min), L 00 C is the liner chr rte prmeter (min mm - ), nd X C is the distnce (mm) from the fireexposed surfce. For specimens protected with the luminum lloy sheet (composites: CA, HA, nd HV), y-intercept prmeter must e dded to Eqution () to ccount for the delyed chrring of the OSB. The corresponding model is T = L X + Y () 00 C 00 C C 0 where Y 0 ws the y-intercept prmeter (min). The mechnicl properties of WAC were investigted in ccordnce with ASTM D The modulus of elsticity (MOE) of WAC ws mesured y sttic ending, nd the internl ond strength ws mesured y tension perpendiculr to surfce (internl ond). The microgrphs of onding interfce etween the OSB nd the luminum lloy sheet were investigted y the D Anlysis System of Super Depth (KEYENCE VHX-000, Osk, Jpn). Results nd discussion C 6..0 ± ±..X C C.4. ±.4 9. ±..X C C ±.6.8 ± 0.4.X C H 6..7 ± ± 0..X C H ± ± 0.6.X C H ±.0.7 ± 0.8.X C CA.6. ±.. ± 4.8.6X C +.0 CA ±..7 ±..6X C +.0 CA.6. ± ± 4..6X C +.0 CA ± 4.9. ± 4.4.6X C +.0 CA ± ± 6..6X C +.0 HA ±.4.9 ±.7.X C +.6 HA ±.4.0 ±.7.X C +.6 HA.6.8 ± ±.6.X C +.6 HA ± ±..X C +.6 HA. 4.6 ± ±..X C +.6 HO ± ± 0.4.6X C HO ± ± 0.4.6X C HO.6. ± ± 0.4.6X C HO ± ± 0..6X C HO..6 ±.0.7 ± 0..6X C HV.0.4 ± ± 0.4.7X C +.9 HV ± 0.. ±..7X C +.9 HV ± 0.. ±.0.7X C +.9 HV ±.4 4. ±.6.7X C +.9 HV.6.6 ± ±.8.7X C +.9 For revitions, see Tle. X C distnce from the fire-exposed surfce. Time (T, men ± SD of three replictes) for the unexposed surfce of ech lyer of WAC to rech n verge T 9 C or T mx,8 C ove room temperture. c Time (T, men ± SD of three replictes) for the unexposed surfce of ech lyer of WAC to rech n verge T 00 C. In some cses, some individul thermocouples of the lst lyer (i.e., lyer or ) did not record T 00 C or were influenced y ignition nd flme spred over the unexposed surfce t the end of the test. This is the reson why sometimes the vlues for the lst lyer re less thn expected. d Liner chr rte equtions to rech 00 C. Dt otined from the thermocouples of the unexposed surfce were not considered to otin Eqution () or (). See footnote for rtionle. Numericl results Tle shows the test results for T 9 C/8 C, T 00 C, nd the liner chr rte models (L) of the different composites. The totl T 9 C/8 C of ll composites rnged from 7.8 to 44.8 min. Individully, the lmintion of the luminum lloy sheet (except in the middle) significntly improved the fire performnce. For hot-pressed composites, the following T 9 C/8 C order ws found: HA > HV > HO > H. Composite CA hd the longest T 9 C/8 C mong ll composites. The results were similr for the totl T 00 C. These results re illustrted in Figure. The chr rtes for the two models [Equtions () nd ()] were clculted from the corresponding times nd distnces from the exposed surfce (Tle ). The L 00 C for the OSB specimens without ny luminum lloy sheet (C nd H) ws. nd. min mm -, respectively. The L 00 C for the corresponding OSB with the luminum lloy sheet (CA nd HA) ws slightly higher (.6 nd. min mm - ). These vlues indicted slightly fster chrring thn the liner Downlod Dte 9// :8 PM

5 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce 0 T 9 C/8 C (min) T 00 C (min) C H CA HA HO HV C H CA HA HO HV OSB ignited nd urned down in 0 min (Figure ). The second lyer of the OSB lso comusted nd turned gry in min. After continuous exposure to fire, chrred holes ppered on the ckside of the pnel nd the entire pnel urned wy in min (Figure ). In the cse of composite HA, some resin cme out with the smoke fter 0 min when the luminum lloy sheet ws locted on the surfce (Figure c). The first lyer of the luminum lloy sheet melted in min. The OSB urned out in min nd the second luminum lloy sheet ws delminted from the OSB nd completely melted in 60 min (Figure d). Composite HO strted to urn nd turned lck fter 0 min of exposure. Lrge mounts of smoke were relesed during the comustion of the OSB (Figure e). The first lyer of the luminum lloy sheet ws seprted from the OSB nd melted in 0 min followed y the comustion of the OSB, nd the second lyer of the luminum lloy sheet fell off the specimen in 0 min. For composite HV, the wood veneer comusted quickly in min (Figure f). The first lyer of the luminum lloy sheet strted to melt in min. The OSB urned up nd the second lyer of the luminum lloy sheet melted in 0 min Distnce from fire exposed surfce (mm) Regression model of the times to rech T 00 C Figure Plots of the times for 9 C/8 C () nd 00 C () increse in temperture t vrious distnces from the fire-exposed surfce. chrring rte of.6 min mm - (0.6 mm min -, 8 mm h -, nd. in h - ) generlly ssumed for the chrring of semiinfinite sl of solid wood or glued lminted lumer. The results were consistent with the results of.4.47 min mm - reported for 8- to 0-mm-thick OSB rim ords (White 00). For the specimens without ny luminum lloy sheet, the regressions with nonzero y-intercept [Eqution ()] confirmed tht the y-intercept is smll nd tht the zero-intercept model [Eqution ()] ws pproprite. The specimens with the luminum lloy sheet on the surfce confirmed the need for nonzero intercept in the model [Eqution ()] (Tle ) due to n initil dely in the chrring. These conclusions were consistent with the results illustrted in Figure nd. Visul oservtion The min oservtions of fire test specimens re shown in Figure. For composite H, the surfce lyer of the The liner regression dt were clculted sed on the complete dt set for the times to rech 00 C (T 00 C ) s function of the composite construction. The unexposed surfce of WAC ws excluded from the dt set. The resulting eqution for T 00 C t distnce X C from the fireexposed surfce ws T =.X + 0.4M X + 9.7M+.94P 00 C C C +.7 HO-.0HV where M = for the specimens with the luminum lloy sheet on the exposed surfce with or without the wood veneer covering (CA, HA, nd HV) nd M = 0 for the ones with exposed OSB (C, H, nd HO). P = for the OSB mde y cold pressing (C nd CA) nd P = 0 for the OSB mde with hot pressing (H, HA, HO, nd HV). HO = for the specimen type HO with the luminum lloy sheet in the interior nd HO = 0 for the rest. HV = for the specimen type HV with the wood veneer covering the luminum sheet nd HV = 0 for the rest. The more significnt prmeters in the eqution were HV, M, nd X C with P r > t of < The less significnt prmeters of P, HO, nd M*X C hd P r > t dt (i.e., 0.047, 0., nd 0.049) eing > The eqution ccounted for most of the vritions with n R of With regrd to the sttistics, () Downlod Dte 9// :8 PM

6 0 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce c d e f Figure Photos nd pproximte oservtion time (the pproximte oservtion time ws in the curve ehind the specimen nme) of WAC during the smll verticl furnce test: () composite H ( min), () composite H (4 min), (c) composite HA (0 min), (d) composite HA (0 min), (e) composite HO ( min), nd (f) composite HV ( min). it should e noted tht the 60 oservtions in the nlysis were not completely independent, s multiple redings cme from ech of the 8 tests included in the nlysis. Comprison of the press method The comprison of the composites under different press methods is listed in Tles nd () nd Figures nd 4 nd. As oserved from the results in Tle, the L 00 C ws. min mm - for composite C with density of 78 kg m -,.0 min mm - for composite H with density of 70 kg m -,.6 min mm - for composite CA with density of 07 kg m -, nd. min mm - for composite HA with density of 969 kg m -. It is visile tht the cold-pressed OSB with higher density hs lower L 00 C (Figure 4 nd ). The overll liner regression model [Eqution ()] indictes those times for T 00 C.9 min longer with the coldpressed OSB. Tle () nd Figure show the T 9 C/8 C improvement in ech lyer of the composite. The T 9 C/8 C difference concerning the composite without the lmintion of the luminum lloy sheet rnged from. to.8 min (verge of.9 min). Tht of WAC rnged from.7 to.8 min (verge of.9 min). The therml resistnce long the thickness plne incresed due to incresed density nd contriuted to the oserved sutle L differences. The lrger is the therml resistnce, the greter is L 00 C. The presented dt here support those of White (00) nd Schffer (967) concerning the L 00 C increment s function of density. Downlod Dte 9// :8 PM

7 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce 0 Tle T 9 C/8 C difference (min) of ech lyer (L) of the composites: () composites under different press methods (H nd HA for hot pressing nd C nd CA for cold pressing), () lmintion with or without ny luminum lloy sheet (C nd H without ny luminum lloy sheet, CA nd HA with the luminum lloy sheet on the surfce, nd HO with the luminum lloy sheet in the middle), nd (c) lmintion with or without the wood veneer (HA without the wood veneer nd HV with the wood veneer on the surfce of the luminum lloy sheet). Composites T 9 C/8 C difference (min) for the lyers L L L L4 L () H vs. C..6.8 HA vs. CA () C vs. CA H vs. HA..0. HO vs. HA HO vs. H (c) HV vs. HA Effect of the luminum lloy sheet The influence of the luminum lloy sheet on the fire performnce of WAC is shown in Tle () nd Figures nd 4c f. The results in Tle () indicte tht the T 9 C/8 C improvement of ech lyer for cold0pressed specimens ws 7.8,., nd. min with n verge of 0.4 min. The corresponding dt of hot-pressed specimens re.,.0, nd. min with n verge of 9. min (see lso Figure ). The composites with the luminum lloy sheet on the lminte surfce needed remrkly longer totl time for destruction thn the composites without ny luminum lloy sheet. The overll regression model [Eqution ()] shows n verge dely in the chrring of the OSB (T 00 C ) of 9. min with the luminum lloy sheet on the lminte surfce. The luminum lloy sheet with thickness of 0. mm dhered to the surfce of cron fier-reinforced composites y Chng nd Zheng (00) to improve their therml resistnce ecuse of its excellent therml conductivity. The temperture differences of the vrious res diminished with time, nd the therml resistnce long with the thickness significntly incresed with the luminum lloy sheet on the surfce (Figure 4c nd d). This prevents rpid temperture increse long with the thickness. The het dissiption potentil of the luminum lloy sheet should e emphsized; tht is, the luminum lloy sheet on the surfce is kind of het rditor nd reflector nd prevents the rpid heting of the OSB (Suykto et l. 00). Moysey nd Muir (968) worked with shiny glvnized steel or luminum on wood nd estimted tht the time for ignition of wood ws four times longer with these mterils on the surfce. With the metl cldding pinted or smered with mud, the effect ws essentilly deteriorted ecuse of hindering the ionizing rdition. The T 9 C/8 C difference for the composites with the luminum lloy sheet in different positions (HO vs. HA) ws.9, 6.6, nd 8. min [Tle ()]. The temperture for composite HO rose fster thn tht of composite HA (Figure 4e). Expectly, HO initilly ehved more like composite H thn composite HA [Tle (); Figures nd 4f]. For composite HO, the comustion performnce of the first lyer of the OSB ws criticl point. The het reflection ility of the luminum lloy sheet diminished with the OSB on the surfce. Therefore, the influence of the luminum lloy sheet on the first lyer of the OSB ws very smll. After urning the OSB lyer, the interior luminum lloy sheet ecme surfce luminum lloy sheet. As result, there ws smll increse in T 9 C/8 C over tht for composite H [Tle (); Figure ]. In summry, lmintes with the luminum lloy sheet in the middle provided miniml improvement in the fire performnce of WAC. In the overll regression chrring model [Eqution ()], the ddition of the luminum lloy sheet in the interior incresed the T 00 C y. min. Effect of the wood veneer The effect of the wood veneer on the fire performnce of WAC is presented in Tle (c) nd Figures nd 4g). The T 9 C/8 C of ech lyer ws reduced y 7., 8.7,.4, 4.8, nd 6.0 min, respectively, fter the lmintion of the wood veneer on the surfce of the luminum lloy sheet (HV shown in Figure A nd Tle ) s shown in Tle (c). The verge reduction time ws 7.7 min. The results indicted tht the fire performnce of WAC decresed if the wood veneer ws on the surfce (Figure 4g). In the overll regression chrring model for T 00 C [Eqution ()], the ddition of the wood veneer to the luminum lloy sheet reduced the T 00 C y min. This is in contrst to the improvement of 9. min provided with the luminum lloy sheet on the surfce of the OSB. As illustrted in Figure 4g for T 9 C/8 C, the composite with the wood veneer (HV) on the luminum lloy sheet initilly ehved like the exposed OSB (H), ut lter on the T 9 C/8 C ws more consistent in the cse of composite HA. This cn e explined y the het reflection of the luminum lloy sheet fter the wood veneer ws urned off. Modulus of elsticity The sttic MOE of different composites is shown in Tle 4. The MOE vlue of composite HA, which ws prllel or Downlod Dte 9// :8 PM

8 04 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce C-lyer- C-lyer- C-lyer- H-lyer- H-lyer- H-lyer- 4 4 CA-lyer- CA-lyer- CA-lyer- CA-lyer-4 CA-lyer- HA-lyer- HA-lyer- HA-lyer- HA-lyer-4 HA-lyer- Temperture ( C) c e C-lyer- C-lyer- C-lyer- CA-lyer- CA-lyer- CA-lyer- CA-lyer-4 CA-lyer- HA-lyer- HA-lyer- HA-lyer- HA-lyer-4 HA-lyer- HO-lyer- HO-lyer- HO-lyer- HO-lyer-4 HO-lyer- d f 4 4 H-lyer- H-lyer- H-lyer- HA-lyer- HA-lyer- HA-lyer- HA-lyer-4 HA-lyer- H-lyer- H-lyer- H-lyer- HO-lyer- HO-lyer- HO-lyer- HO-lyer-4 HO-lyer g HA-lyer- HA-lyer- 700 HA-lyer- 600 HA-lyer-4 00 HA-lyer- HV-lyer- HV-lyer- 400 HV-lyer- 00 HV-lyer HV-lyer Time (min) Figure 4 Time-temperture curve of different composites: () composite C vs. composite H, () composite CA vs. composite HA, (c) composite C vs. composite CA, (d) composite H vs. composite HA, (e) composite HA vs. composite HO, (f) composite H vs. composite HO, nd (g) composite HA vs. composite HV. perpendiculr to the OSB, incresed y 09% (4.09 GP) nd 48% (4.7 GP), respectively. Mentime, the MOE of composite HO exceeded tht of composite H y out 6% (.4 GP), which ws prllel to the OSB, nd tht of the perpendiculr to the OSB ws out 66% (4.6 GP). Oviously, the lmintion of the luminum lloy sheet Downlod Dte 9// :8 PM

9 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce 0 Tle 4 MOE of different specimens prllel ( ) nd perpendiculr ( ) to OSB orienttion Composite MOE ( ) to the OSB Men ± SD (GP) CV (%) MOE ( ) to the OSB Men ± SD (GP) CV (%) O.6 ± ± H 4.6 ± ± 0.. HA 8.6 ± ± 0.9. HO 8.0 ± ± Men is for repeted specimens. CV is coefficient of vrition. Composite O hs single lyer of the OSB. thn tht of composite HO. The reson ws tht the MOE incresed with the incresing distnce etween the luminum lloy sheet nd the core lyer (Arni et l. 0). As consequence, composite HA exhiited the lrgest MOE mong the entire composites. Figure shows the MOE difference etween prllel nd perpendiculr to the OSB. The difference of MOE etween prllel nd perpendiculr to the OSB decresed due to the isotropic nd excellent mechnicl performnce of the luminum lloy sheet lminted with the OSB. The uniformity nd strength of the composites ws enhnced due to the lmintion of the luminum lloy sheet Internl ond strength MOE difference (GP) Composite O Composite H Composite HA Composite HO Specimen nme Figures 6 nd 7 show the onding interfce etween the luminum lloy sheet nd the OSB. It ws found tht the MDI dispersed sufficiently nd formed excellent mechnicl interlocking etween the OSB nd the luminum lloy sheet. A compct nd continuous glue lyer ws efficiently generted. Rupture ws oserved to occur in the core of the OSB for the entire composites (Figure 7). It ws concluded tht the onding strength etween the OSB nd the luminum lloy sheet ws greter thn the internl ond strength of the OSB. Figure MOE (for the OSB nd WAC) difference etween prllel nd perpendiculr to the OSB (composite O ws the composite with single lyer of the OSB). in the middle (HO) or on the surfce (HA) significntly enhnced the composite strength (HO nd HA shown in Figure A nd Tle ). It ws lso noted tht the incrementl strength of composite HA ws significntly greter Conclusion The fire performnce of WAC ws investigted in ccordnce with ASTM E9. The T 9 C/8 C of different composites rnged from 7.8 to 44.8 min. It ws lso indicted tht the position of the luminum lloy sheet significntly ffected the fire performnce of WAC. The T 9 C/8 C ws improved nd more thn douled fter the lmintion of the OSB with c Figure 6 Bonding interfce etween the luminum lloy sheet nd the OSB. Mgnifiction, 00, 000, nd 000 ( c, respectively). Downlod Dte 9// :8 PM

10 06 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce Figure 7 Reference photo for tension testing perpendiculr to the surfce (internl ond) of the specimen. The specimen size ws mm ( in). the luminum lloy sheet. The cold-pressed composites showed etter fire performnce thn the hot-pressed composites. The fire performnce of composite with.6-mmthick luminum lloy sheet locted on the surfce ws est followed y the composite with.4-mm-thick wood veneer on the surfce of the luminum lloy sheet nd then y the composite without ny luminum lloy sheet for the hotpressed composites. The lmintion of the wood veneer on WAC surfce detrcted the fire performnce. The positioning of the luminum lloy sheet in the middle of the composite provided little improvement in the fire performnce compred with the OSB without ny luminum lloy sheet. The MOE vlues qudrupled when the luminum lloy sheet ws locted on the surfce. The onding strength etween the OSB nd the luminum lloy sheet ws greter thn the internl ond strength of the OSB lone. Acknowledgments: The uthors thnk the industry specil fund project (004004) nd outstnding scholr teching pln of Chinese Acdemy of Forestry (CAF) for supporting this pper. We lso gretly pprecited ssocite Professor Youming Yu (Zhejing Agriculture & Forestry University) for his technicl ssistnce during the nlyzing of onding interfce. References Arni, A.G., Mghmiki, S., Mohmmdimehr, M., Arefmnesh, A. (0) Buckling nlysis of lminted composite rectngulr pltes reinforced y SWCNTs using nlyticl nd finite element methods. J. Mech. Sci. Techn. : Arrowsmith, D.J., Clifford, A.W. (98) A new pretretment for the dhesive onding of luminum. Int. J. Adhes. Adhes. :40 4. Brusks, V. (00) Chrring rte of wood s tool for fire investigtions. Fire Sfety J. 40:8 4. Chng, X.Q., Zheng, G.T. (00) Three-dimensionl het trnsfer nlysis to hyrid multilyer composite structure. Chin. J. Appl. Mech. :6 67. Erchinger, C., Frngi, A., Fontn, M. (00) Fire design of steel-totimer dowelled connections. Eng. Struct. : Fogle, E.J., Lttimer, B.Y., Feih, S., Kndre, E., Mouritz, A.P., Cse, S.W. (0) Compression lod filure of luminum pltes due to fire. Eng. Struct. 4: 6. Hshim, R., How., L.S., Kumr, R.N., Sulimn, O. (00) Some of the properties of flme retrdnt medium density fierord mde from ruer wood nd recycled continers contining luminum trihydroxide. Bioresource Technol. 96:86 8. Îstek, A., Aydemîr, D., Eroğlu, H. (0) Comustion properties of medium-density fierords coted y mixture of clcite nd vrious fires retrdnt. Turk J. Agric. For. 7: Jmes, O., Dvid, C., Peter, J.M., Mssimo, F., Andrew, H.B. (009) Fire performnce of timer-concrete composite floors. NZL Tim. Des. J. 9:4. Li, B., Jing, H.L., Zhng, S.F., Wng, Y.F., Sui, X.Y. (004) Influence of luminum hydroxide on flme retrdncy nd mechnicl properties of PE-HD/wood flour composites. J. Chin. Plst. 6:. Lu, K.Y., Fu, F., Sun, H.L., Fu, Y.J. (0) Bonding technology of electromgnetic shielding plywood lminted with conductive sheets. Wood Res. Slov. 8: Moss, P.J., Buchn, A.H., Frgicomo, M., Lu, P.H., Chuo, T. (009) Fire performnce of olted connections in lminted veneer lumer. Fire Mter. : 4. Moysey, E.B., Muir, W.E. (968) Pilot ignition of uilding mterils y rdition. Fire Technol. 4:46 0. Schffer, E.L. (967) Chrring Rte of Selected Woods Trnsverse to Grin. Forest Products Lortory. USDA Forest Service, Forest Products Lortory, Mdison, WI. pp. 8. Schffer, E.L. Effect of Pnel Thickness nd Noncomustile Inserts on Surfce Flmmility of Plywood. Reserch Note FPL-. USDA Forest Service, Forest Products Lortory, Mdison, WI, 967. Schnl, S., Plninc, I., Turk, G. (009) Fire nlysis of timer composite ems with interlyer slip. Fire Sfety J. 44: Song, X.B., Lm, F. (0) Stility nlysis of metl-plte-connected wood truss ssemlies. J. Struct. Eng. 8:0 9. Suykto, B., Ht, T., Ide, I., Kwi, S. (00) Fire-resistnt performnce of lminted veneer lumer joint with metl plte connectors protected with grphite phenolic sphere sheeting. J. Wood Sci. 47: Tsi, K., Crrdine, D., Moss, P., Buchnn, A. (0) Chrring rtes for doule ems mde from lminted veneer lumer. Fire Mter. 7:8 74. Urso, V.M., Gison, A.G. (009) Fire model for fier reinforced plstic composites using pprent therml diffusivity (ATD). Plst. Ruer Compos. 8:87 9. White, R.H. (98) Wood-Bsed Pneling s Therml Brriers. USDA Forest Service, Forest Products Lortory, Mdison, WI. pp.. White, R.H. (98) Use of coting to improve fire resistnce of wood. In: The Need for Stndrds. ASTM STP 86. Eds. Morris, L., Stumpf, F.M. ASTM. pp Downlod Dte 9// :8 PM

11 K. Lu et l.: Reinforced hyrid wood-luminum composites with excellent fire performnce 07 White, R.H. (00) Anlyticl methods for determining fire resistnce of timer memers. In: The SFPE Hndook of Fire Protection Engineering. Section 4, Chpter, rd ed. NFPA, Quincy, MA. Vol. 4. pp White, R.H. (00) Fire Resistnce of Engineered Wood Rim Bord Products. Forest Products Lortory. pp.. White, R.H., Crmer, S.M., Shresth, D.K. Fire Endurnce Model for Metl-Plte-Connected Wood Truss. FPL-RP-. USDA Forest Service, Forest Products Lortory, Mdison, WI, 99. Winndy, J.E., Wng, Q.W., White, R.H. (008) Fire-retrdnt-treted strndord: properties nd fire performnce. Wood Fier Sci. 40:6 7. Yng, H.Q. (0) Preprtion nd properties of luminum/wood decortive composite. Chin. Acd. For Zhng, Z.X., Zhng, J., Lu, B.X., Xin, Z.X., Kng, C.K., Kim, J.K. (0) Effect of flme retrdnts on mechnicl properties, flmmility nd fomility of PP/wood-fier composites. Compos. Prt B Eng. 4:0 8. Downlod Dte 9// :8 PM