COMPARISON OF PERVATED TEMPERATURE TENSILE PROPHRTITS ANID FATIGUE: BEHAVIOR OF TWO VARIANTS OT A WOVEN SiC/SIC COMPOSITE Seeeramesh Kelton ‘Ohne Aerospace Tague NASA Glenn Rescurch Center 21000 Brookpark Road MS 49-7 Brook Park, OH 44135, Antkoay M. Caloming NASA Glenn Research Center 21000 Beookparke Road MIS 49.7 ‘Brook Park, OH 44135 Davie N. Brewer US Army Renearch Fhoratory NASA Glenn Research Center 21000 Brookparic Read M/S 49-7 Tsk Park, OF 14135 ABSTRACT ‘Tensile properties (elastic modotus, prvpacivaul lim strength in plane tensile scength, sna strain at failure} of two vastants of a woven SiC/SiC composite, manufacrarcd duting tw sopanite lime periods (9/99 and 1/01), were determined at 1N38 amd 1204°C: by conducting tensile tests on specimens machined from plates. Conlinunus cycling fatigue tesls R= 0,05 aud 20 cpm) were alsa conducted! at the sams feo fomupovaRucs an specimen From Fal compiles, Tnthis study, average lense propestes, 95% confidence intervals assaciated with the tensile propcitics, and gcometric mean fatigue lives al hoh composite materials arc.compared. The ‘observed similavties and difterenecs inthe tensile properties wre highlighied and sm atrernpt is made lo understand she relatiouship. if any, between the wnsile properties und the Eig Dehuviors ofthe hu woven soemposites, INTRODUCTION Advauced pas cubine engines, which are typically designee us operate augmented efficiencies, esquire higher operating temperatures. Ia onder wo devign for such sn environmcat, ‘materiale thal van seihsiand thee higher operating temperanes as well ax provide sustained performance sce required, Ceramic matrix vompusites (CMCs) are strongly preferred fr these: teks because of tair high temperature copability und high specie strength. A woven SiC composite (manufactured by a slurry-cast, mele-atiltration process) has boon wdantficd as a potetual combustor ner raatctial for the advanced airerat yas turhine enyrnes!. For design, DPurpores, boi the reliability andl repyaducsbilty of this woven CMIC need i he estahlished und swiuble Lensile property and fatigue ie dtu hues ere requtre. ‘The to woven composites evalualed in this study were manufactured by Goacral Blectae Power Systems Composites. LLC during September 1999 (999) and Jumuary 2001 (01) with the Chemical Vapor Infileated (CV1) SiCishunry-casvneleinltration process. “Tensile properties oad fatigue behaviur (hoth without end wich hold-tnus) at 1038 anal 12047 “hug 9.8 pap or rep of a pape xen open Conleteree, Because changes maybe made hele fora fubiaton, tie e mage avec tn ne arse ig tl fo: oad or produced wien persian of he ut for the 9/99 camposite were previously reported? Tensile prapentias a hh the 9/99 an 1201 samp al 16 und [204°C and the variability exhibited ly esch of those properties were also <dgvuunented earlier. In this investigotion, additional tensile tests at 1038°C and Eecigue ests at 1038 and 1204°C were conducted on the L101 composite material. The tensile prapecics and fatigue lives from ihe 9/99 and M01 woven SIC/SIC curposives gencratcu at 1038 and 1204%C ‘were compared to idenity similarities us ell as differences, In purtcular, the dependency of argue ives on the tensile properties af the woven composites Was explored, EXPERIMENIAL DSTAILS Sylramio™ ace in a SHS weave, 20 FPL configuration with # [O90 Iyy-up constituted the fiber pro-form for holh uke 9/99 snd 401 zarmpowites. Tn the case oF tre VOL counpesie, before mates densification, the her pre-forens were subjected ui an in-situ BN GBR} heat Inmalment. Chemical vapat ifilvaed, silican-doped BN interphase and a CV SIC matrix tute suljected wa a slamy-cas, uct infilteation process (Ml) were utlized foc bath the composites, Rectangelar composite plats (229 mam length, 152 mm wis, and mm thiskaess} were produced by the manufacturing prcess aud Lest specimens for buith tensile and fatigue tests were ‘machened finn these plares, The cast section within these specimens was 10.2 mm Wide and 23 nvm i Jenga, Addiciona! details ou the tex specimen zecmetry and test system, iuskacing test specimen gripping method, es! Frame ahgrment procedure, spocimen hes, smu lemperalure measurement lechmaques, strain measurement method, an! Wal proveures, were repurted previously?" In Fatigue tots, triamyulae waveform witha Frequency of @.23 Thz (20 op) and an 2R-tatio Cinimu foad to mastiqnam load) of R= 0.05 were used. tn all the fatigue tests, faiTure ‘yom defined ux separation a dhe lest spesizaen into (90 pieces, TENSILS PROPERTITS ‘Tensile properties investiga in thin study are the follawing: elastic nsvdulus, proportional Hic strength (0.008F offset), PLS: in-plane cenile strength, 11S: and stain at Failure, SF. Mean values and associated srandacd deviations of these four tensile peopertics arc shan Tables {and Il respectively, for che 9/99 and 1404 composites. 4 total af 24 tensile tess were conducted st 1204°C for beth the 9/99 and 1/01 composites. At $038°C, due toa limited number of specimens, only six anil eight tes were cemducted far the 999 and 1/01 composites, respectively. Mean YTS and SF values of the HO) conenite were significantly bigher than the corvesponding values forthe 9/99 composite. Na clear cut differences were obseeved among the miean and PLS valves berveen the two composites, iu genes, at batt ‘emperatures. stindurd deviations of the UL material wore higher than lhuse exubited by the ‘9999 marctial wnt two exceptions (PLS at 1204°C and ITS at 1038°C). Table 1. Meum» oo landard Deviations of Vensile Propertics for $49 ML SiC/SiC Composite Temperatuce Numberof Teste E PLS 1S SE bey w [Ges IMPal MPa 16a 1038 6 208415) Tes (20) 325129) O44 0G Pay 4 124d) 160 28} 307 4121} 0.48 {0.07} © [] Pesos Standard Deviation ‘Table I. Means and Standard Deviations of Tensile Properties fon UO MT SiCISIC Composite Tempersture Number of TexsE PLS 11S sr Pel fal lor IMPal ipa ie Tos 3 TRUST wD 135) ATIOE —_OKDIO.ITY 1204 4 184425] 155 (28) 399 137} 0.57 [NL12] 7 f} Denote Stundurd Deviation ‘Average tensile piopottice and eoceesponding 95% confidence intervals ferrar bars) al 1WAS and 1204°C! For the two composites are compared dizcetly wich bar chats in Figs. | 4. ‘The confidence intervals were estimated as wvice the standard deviation for each tensile propsaty. Student's lest with a isk level, = 0.02, und a toretailed divhifution was usa te compre reap valucs of all the tensile prepettes tor both coraposites. At the investigcted tempera rg slaisnally gmitican aiferonces were found to cxist between the two composites for the moun values of TE and PLS, Dillereneve im the scan 11S und SE valves wore found to be ‘statistically significant between the vwo composites, Higher seatier exbited by the mean tensile properties of the 1/01 campasite in camparinan 10 the 999 composite and tho statisucally signin differences observed aumong the mean (TS and SP values of bath composites might Be due wo the iN heat uestincne givea tothe fiber pre forms of che 1/0 composite TATIGUR BEHAVIOR Fatigue tests were conducted with a maxismuta st2SS, Cm,» of 179 MPa azul an Rez, R, of 05 on specimens from both composites. The selected matiamn steess wat abuve ‘he average PLS values of the two composites at boch temperatures {Tables 1 and IL). Three texte wore conduuted uf cach Lemperiuute i obiin x representative fatigne Lie, The observed ueometvic mew fatigue Tives (equivalent ariduaolv rasan Jutigue lives in log space) ure listed in Table TIL Tor the 999 and L/L composites, the geometric meun fatigue life decreased as temperature increased from 1038 to 1204°C. At hoth temperatares, eecmetric mean fatigue lives of the 1/01 composite were higher than chose of the 9/99 composics Since average PLS valuen af bah composites were very similar, the highcrfaticus live of 1401 oompasite conld have resulted Trumn the higher average in-plane tensile sien of this earmpsile Table IIL Geometric Moun Fatigue Lives of MI SIC/SiC Composite (Gg5 = 178 MPa: R= ‘Temperature Number of Tests 9799 01 re im (Cycles Wcyetes] 3 Tie 32038 2 4093 20405 Spccionons fatigued te failure at bth 1038 and 12U4°C are shown in Figs. 3 and 6. Ta <gzousval, a majotity of dhe specimens tailed in the test section with only two speciunens lang in tho tramilion region betsseen The Eripping arca andl the test section (Fi, 8), Fatigue life data trom these (ro socimens were included in calculating the peametzic mean fatigue life bocauss oF the Following reasons: 1) failure locations sere closer to he test eliun than the grip section inckcatiny, that lemmperalures at these lucations were very clone tc dhe lest lempecsunes and 2) Ihe lunge transition radius used in the apecimes Sesien, betiveen the gui and wt sweliom, die na significantly increase the dimensions atthe failuce locations. «Arithmetic awean logarithmic cyclic lives and associated minimum sd eniximm salves sce plotted in Fig, 7 for both composites. For the limited number uf [aliguo toss vondncled, fatigue lives of 1AM composite exhibited neh less sexe ut bolh lemperatures than those fram the 9/99 composite, This obscrved trond in faligue Hives was npposite ta that exhihited by he tensile properties for hath Ihe compasiles [ede that more wnsile Lae thor Tague tests were conducted sm each coraposie and the Realler inthe fatigue lives of te 1401 composite might evenmally increase i woe fatiaue tests were conducted, DISCESSION ‘he primary differcnos in processing between the twe composites was the WBN hea: trearment provided for the fiber preforms of the 1/01 composite before msatix densification, ‘Sinaia teestraent was na given 4 the fice pre Forms of the 9/99 composite, «As evidenced by the Studems's Ices resulls af meun tensile properlies of hott computes, the IBN reatment seuins ls amprove the mean TTS and SF values while having na sigafieunl influence cn the mer, Bend PLS values. Moteover. the 1/01 composite, whieh secelved this resumen, exhibited much Jeger variation in all four tensile propertis than the 9/99 eorapesite, The higher geometric mean Exugue ves observed for Ine 1-05 composite ay comune thy vorzesponding Ives ofthe 9510 composite corelad well with higher mean TTS voluee exhibited by the L101 coraporte, The ‘tenson For Inwer scatter observed in the fatigue lives of the L4¥T composite, which is opposite te lhe end observed inthe tensile prope, is abt very lear due tp the liited nurber af Taligue tests conducted inthis study. syatcunatic Tatigus investigation tat includes at less six to ben -spcciranns pox tes! condition is roquited ro quantify seatcr inthe fatsgne data in a scliable COKCLUDING REMARKS: ‘Tensile properties an fatigue behavior of two variants of a woven SiC/SiC: composi anu faetured during neo seprated ime perivuls (9/99 and 1/01) were investigated at 1038 and T2DASC. Fiber pre-forres vf the 1/01 coax were WBN hel-reated pric o mesrix sdonwficusion by slurry-casl, melGinfltation proces, Na sucla abet wax given to the her pre-fotms of he 9/99 composite. Average tensile properties and associated standard deviations ‘were reported anc compared for bath composites, Geometric mew farigue lives of bath the composites ure proanted vlong wath the associnied soatcr funds, Lhe 1/01 comaposite oxtibited bighor average valuey of in-plane tensile strength and etrin at Flue inthe tonsil tests and higher geometric mean fatigue lives campared th the 9/99 compasite. The 1/01 composite exlibited moce vasiation i the tensile peoperties than the 9/99 cormposte, whereas the upposile ‘was truc forthe acatfer abssrved in tho fatigue lives. ACKNOWLT.DGEMENTS Financial support for this work Was obtained from NASA Glenn Research Center, Brock Park, Ohio under cooperative agreement NCC-=3-1841 through the Citta Bttcieat Rngioe ‘Technology Program. The authors ure grateful io Mf Joba D, Zima and Mi. Willissa L, Browa Tor comducting Ue tensile and faigue tests at NASA Glenn Research Center, REFERENCES: 'D, Brewer, “HSR/EEM Combustor Materials Development Program,” Materials Science and Engineering, 4261, pp. 284-201, 1999 “8. Kalhiri, A.M. Coloring, and D. N. Brewer, “Tigh Temperature Tensile Properties and Fatigue Dehaviie of a Mel-Infillcaed SiCISIC. Composite,” Farigue 2002, Pr. of the 8! Id. Fatigue Congeess, Vol. 3/5, A. F. Blom, Bd, Stockholm, Sweden, pp. 4965-1972, 2002. '§. Kollor, 8. M. Gilomino, snd D,.N- Brewer, "An Assossment of Variability in he AverageTontile Priperies af « Melt-nfiliruial SiC SiC Compose,” Canale Engmerring ant Science Proceedings, Vol. 25, Tous 4, 28° Inlemativnsl Conference on Advanced Ceraraivs wd ‘Composites: B, Edgar Lara-Curzia and Michael J. Resdey, Ts., pp. 79-86, 2004. “ML. J. Verll, A. M. Calomino, and D. N. 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Lin and M Singh, Fes. pp. 435-442, 2002, 400 7 — ca 101 & 00 g 1 3 00 i 3 cE g % woot F 0 1028"C- Temperature [°C] igure J: Average Elastic Modul and 95% Confidence Intetvals for ‘Twa Waviants of a Woven SICISIC Composite 300 Proportional Limit Strength, PLS [MPa] 100 30 a 1038°C. 1208°C ‘Temperature [°C] Figure % Average Propostional Limit Strengths and 95% Canfideney Fubervuls for ‘Twa Variants of a Woven SICSIC Composive In-Plane Tensile Strength, ITS [MPa] 038°C 1208°C ‘Temperature [’C] sigue 3: Average in-Plau fensile Stengths and 95% Confldenec Intervals tor ‘Torn Voriants of a Woven SiCISiC Composite _ om ao Eos vot T & 8 08 Pay e B02 oo 4038°C 1200 ‘Temperature [°C] igure ds Average Singing at aplure and 958% Confidence Intcvals for ‘Twi Varinus ofa Waven SiCISHC Compose ie orraey ess ee Tox” NASA] ena fit. Fel ‘Figure 5: Specimens Tested in Futigu at L204°C: 9199 SICISIC Compile Mean Log Cyclic Life, Log, {N,) syeure 7, Figune 6: Specimens Tested in Fatigue at 1038" VOL SiCISiC Composite 6 . Smax= 7OMPa R=005 | == 8108 st ™ T woz 1101 4 a 2 1 a 1038°C 1208°C. Temperature [°C] Auithmctie Mean Logarithmic Fatigue Lives and Eatseme Values for ‘Tun Varn of a Woven SICISIC Composite