Introduction. Composite Materials Advanced Aerospace Application: Advanced Aerospace Application:

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1 Introdution oposite Materials A oposite aterial is a aterial syste oposed o two or ore aro onstituents that dier in shape and heial oposition and whih are insoluble in eah other. The history o oposite aterials dates bak to early 20th entury. In 940, iber glass was irst used to reinore epoxy. Appliations: Aerospae industry Sporting Goods Industry Autootive Industry Hoe Appliane Industry Advaned Aerospae Appliation: Advaned Aerospae Appliation: Lear Fan 200 all-oposite airrat Boeing 767,777, 787 airplanes w/ the latest, ull wing box is oposite): Sporting Goods Autootive

2 Terinology/lassiiation Various appliations oposites: woven ibers -- Multiphase aterial w/signiiant proportions o eah phase. Matrix: -- The ontinuous phase -- Purpose is to: transer stress to other phases - protet phases ro environent -- lassiiation: etal ross setion view MM, M, PM erai polyer Dispersed phase: Purpose: enhane atrix properties. Elya dokua MM: inrease y, TS, reep resist. M: inrease K PM: inrease E, y, TS, reep resist. -- lassiiation: Partile, iber, strutural oposite Strutural Organization: the design variations Fig. SEM iage o the sallest working gear (arbon nanotube/nylon oposite); inset exhibits the ratured surae. Fig. 2 (a) Sheati diagra o an individual layer o honeyob-like arbon alled graphene and how this ould be rolled in order to or a arbon nanotube; (b) (d) HR-TEM iages o single, double- and ulti-walled arbon nanotubes (insets are their orresponding iages). oposite Beneits oposite Survey Ms: Inreased toughness Fore oposites Partile-reinored Largepartile Dispersionstrengthened partile-rein Fiber-reinored ontinuous (aligned) Strutural Disontinuous (short) Aligned Randoly oriented Lainates Sandwih panels iber-rein un-rein Al εss (s-) 0-6 Inreased reep resistane erais Bend displaeent MMs: PMs: Inreased E/ρ 03 E(GPa) 02 PMs Al w/si whiskers etal/ etal alloys. G=3E/8 polyers.0 K=E Density, ρ [g/3] Adapted ro T.G. Nieh, "reep rupture o a silion-arbide reinored aluinu oposite", Metall. Trans. A Vol. 5(), pp , 984. Used with perission. (MPa)

3 oposite Survey: Partile-I oposite Survey: Partile-II Exaples: - Spheroidite atrix: steel errite (α) (dutile) - W/o eented arbide - Autoobile tires 60µ atrix: obalt (dutile) V: 5-2 vol%! 600µ atrix: rubber (sot, dutile) 0.75µ partiles: eentite (Fe3) (brittle) partiles: W (brittle, hard) partiles: (stier) onrete gravel + sand + eent - Why sand and gravel? Sand paks into gravel voids Reinored onrete - Reinore with steel rebar or reesh - inreases strength - even i eent atrix is raked Prestressed onrete - reesh under tension during setting o onrete. Tension release puts onrete under opressive ore - onrete uh stronger under opression. - Applied tension ust exeed opressive ore Post tensioning tighten nuts to put under rod under tension but onrete under opression nut threaded rod oposite Survey: Partile-III Elasti odulus, E, o oposites: -- two approahes. upper liit: rule o ixtures E = VE + VpEp Data: u atrix w/tungsten partiles E(GPa) lower liit: = V + Vp E E Ep vol% tungsten (u) (W) Appliation to other properties: -- Eletrial ondutivity, e: Replae E in the above equations with e. -- Theral ondutivity, k: Replae E in above equations with k. oposite Survey: Fiber Fibers theselves are very strong Provide signiiant strength iproveent to aterial Ex: iber-glass ontinuous glass ilaents in a polyer atrix Strength due to ibers Polyer siply holds the in plae and environentally protets the Fiber Loading Eet under Stress: oposite Survey: Fiber ritial iber length (l ) or eetive stiening & strengthening: iber strength in tension iber length > 5 τ Ex: For iberglass, a iber length > 5 is needed sine this length provides a ontinuous iber based on usual glass iber properties d iber diaeter shear strength o iber-atrix interae Why? Longer ibers arry stress ore eiiently! Shorter, thiker iber: d Longer, thinner iber: iber length < 5 iber length > 5 τ τ (x) (x) d Adapted ro Fig. 6.7, allister 7e. Poorer iber eiieny Better iber eiieny 3

4 * d l = 2τ Fiber Load Behavior under Stress: oposite Survey: Fiber Fiber Materials Whiskers - Thin single rystals - large length to diaeter ratio graphite, SiN, Si high rystal peretion extreely strong, strongest known very expensive Fibers polyrystalline or aorphous generally polyers or erais Ex: Al 2 O 3, Araid, E-glass, Boron, UHMWPE Wires Metal steel, Mo, W Fiber Alignent Adapted ro Fig. 6.8, allister 7e. Behavior under load or Fibers & Matrix aligned ontinuous aligned rando disontinuous oposite Strength: Longitudinal Loading ontinuous ibers - Estiate iber-reinored oposite strength or long ontinuous ibers in a atrix oposite Strength: Transverse Loading In transverse loading the ibers arry less o the load and are in a state o isostress Longitudinal deoration = V + V but ε = ε = ε = = = ε = ε V + ε V volue ration isostrain E e = E V + E V longitudinal (extensional) odulus F = EV = iber F E V = atrix Reebering: E = /ε and note, this odel orresponds to the upper bound or partiulate oposites E t V = E V + E transverse odulus Reebering: E = /ε and note, this odel orresponds to the lower bound or partiulate oposites 4

5 An Exaple: oposite Strength UTS, SI Modulus, SI 57.9 MPa 3.8 GPa 2.4 GPa GPa Estiate o E and TS or disontinuous ibers: -- valid when iber length > 5 d τ -- Elasti odulus in iber diretion: (24.5 GPa) (9.34 GPa) Note: (or ease o onversion) 6870 N/ 2 per psi! E = E V + KE V eiieny ator: -- aligned D: K = (aligned ) -- aligned D: K = 0 (aligned ) -- rando 2D: K = 3/8 (2D isotropy) -- rando 3D: K = /5 (3D isotropy) -- TS in iber diretion: (TS) = (TS) V + (TS) V Values ro Table 6.3, allister 7e. (Soure or Table 6.3 is H. Krenhel, Fibre Reinoreent, openhagen: Akadeisk Forlag, 964.) (aligned D) oposite Survey: Fiber oposite Survey: Fiber Aligned ontinuous ibers Exaples: -- Metal: γ'(ni3al)-α(mo) -- erai: Glass w/si ibers by euteti solidiiation. ored by glass slurry atrix: α (Mo) (dutile) Eglass = 76 GPa; ESi = 400 GPa. 2µ ibers: γ (Ni 3 Al) (brittle) Fro W. Funk and E. Blank, reep deoration o Ni3Al-Mo in-situ oposites", Metall. Trans. A Vol. 9(4), pp , 988. Used with perission. (a) (b) rature surae Fro F.L. Matthews and R.L. Rawlings, oposite Materials; Engineering and Siene, Reprint ed., R Press, Boa Raton, FL, (a) Fig. 4.22, p. 45 (photo by J. Davies); (b) Fig..20, p. 349 (irograph by H.S. Ki, P.S. Rodgers, and R.D. Rawlings). Used with perission o R Press, Boa Raton, FL. Disontinuous, rando 2D ibers Exaple: arbon-arbon ibers: -- proess: iber/pith, then very sti burn out at up to 2500º. very strong -- uses: disk brakes, gas (b) atrix: turbine exhaust laps, nose less sti ones. view onto plane less strong Other variations: -- Disontinuous, rando 3D -- Disontinuous, D (a) E = E V + KE V eiieny ator: -- rando 2D: K = 3/8 (2D isotropy) -- rando 3D: K = /5 (3D isotropy) ibers lie in plane Looking at strength: l > l l V 2l ( V ) ' d = + where is iber rature strength oposite Survey: Strutural Staked and bonded iber-reinored sheets -- staking sequene: e.g., 0º/90º or 0 /45 /90º -- beneit: balaned, in-plane stiness & ' l < l is atrix stress when oposite ails ( V ) ' d ' where: d is iber diaeter & τ is saller o Matrix Fiber shear strength lτ = V + d or atrix shear yield strength Sandwih panels -- low density, honeyob ore -- beneit: light weight, large bending stiness ae sheet adhesive layer honeyob Adapted ro Fig. 6.8, allister 7e. (Fig. 6.8 is ro Engineered Materials Handbook, Vol., oposites, ASM International, Materials Park, OH, 987.) Adapted ro Fig. 6.6, allister 7e. 5

6 oposite Manuaturing Proesses Partiulate Methods: Sintering Fiber reinored: Several Strutural: Usually Hand lay-up and atospheri uring or vauu uring Irwin/MGraw-Hill 2000 The MGraw-Hill opanies, In., Open Mold Proesses Only one old (ale or eale) is needed and ay be ade o any aterial suh as wood, reinored plasti or, or longer runs, sheet etal or eletroored nikel. The inal part is usually very sooth. Shaping. Steps that ay be taken or high quality. Mold release agent (silione, polyvinyl alohol, luoroarbon, or soeties, plasti il) is irst applied. 2. Unreinored surae layer (gel oat) ay be deposited or best surae quality. Hand Lay-Up: The resin and iber (or piees ut ro prepreg) are plaed anually, air is expelled with squeegees and i neessary, ultiple layers are built up. Hardening is at roo teperature but ay be iproved by heating. Void volue is typially %. Foa ores ay be inorporated (and let in the part) or greater shape oplexity. Thus essentially all shapes an be produed. Proess is slow (deposition rate around kg/h) and labor-intensive Quality is highly dependent on operator skill. Extensively used or produts suh as airrae oponents, boats, truk bodies, tanks, swiing pools, and duts. A spray gun supplying resin in two onverging streas into whih roving is hopped Autoation with robots results in highly reproduible prodution Labor osts are lower SPRAY-UP MOLDING ut and lay the ply or prepreg under oputer ontrol and without tension; ay allow reentrant shapes to be ade. ost is about hal o hand lay-up Tape-Laying Mahines (Autoated Lay-Up) Extensively used or produts suh as airrae oponents, boats, truk bodies, tanks, swiing pools, and duts. 6

7 Filaent Winding Ex: pressure tanks ontinuous ilaents wound onto andrel Adapted ro Fig. 6.5, allister 7e. [Fig. 6.5 is ro N. L. Hanox, (Editor), Fibre oposite Hybrid Materials, The Maillan opany, New York, 98.] Filaent Winding harateristis ٠Beause o the tension, reentrant shapes annot be produed. ٠N winding ahines with several degrees o reedo (soeties 7) are requently eployed. ٠The ilaent (or tape, tow, or band) is either preoated with the polyer or is drawn through a polyer bath so that it piks up polyer on its way to the winder. ٠Void volue an be higher (3%) ٠The ost is about hal that o tape laying ٠Produtivity is high (50 kg/h). ٠Appliations inlude: abriation o oposite pipes, tanks, and pressure vessels. arbon iber reinored roket otor ases used or Spae Shuttle and other rokets are ade this way. Pultrusion ٠ Fibers are ipregnate with a prepolyer, exatly positioned with guides, preheated, and pulled through a heated, tapering die where uring takes plae. oposite Prodution Methods Pultrusion ontinuous ibers pulled through resin tank, then preoring die & oven to ure ٠Eerging produt is ooled and pulled by osillating laps ٠Sall diaeter produts are wound up ٠Two diensional shapes inluding solid rods, proiles, or hollow tubes, siilar to those produed by extrusion, are ade, hene its nae pultrusion ٠Prodution rates around /in. Adapted ro Fig. 6.3, allister 7e. ٠Appliations are to sporting goods (gol lub shats), vehile drive shats (beause o the high daping apaity), nonondutive ladder rails or eletrial servie, and strutural ebers or vehile and aerospae appliations. PrePreg Proess PREPREG PRODUTION PROESSES ٠Prepreg is the oposite industry s ter or ontinuous iber reinoreent pre-ipregnated with a polyer resin that is only partially ured. ٠Prepreg is delivered in tape or to the anuaturer who then olds and ully ures the produt without having to add any resin. ٠This is the oposite or ost widely used or strutural appliations ٠ Manuaturing begins by olliating a series o spool-wound ontinuous iber tows. ٠ Tows are then sandwihed and pressed between sheets o release and arrier paper using heated rollers (alendering). ٠ The release paper sheet has been oated with a thin il o heated resin solution to provide or its thorough ipregnation o the ibers. 7

8 PrePreg Proess PrePreg Proess ٠ The inal prepreg produt is a thin tape onsisting o ontinuous and aligned ibers ebedded in a partially ured resin ٠ Prepared or pakaging by winding onto a ardboard ore. ٠ Typial tape thiknesses range between 0.08 and 0.25 ٠ Tape widths range between 25 and 525. ٠ Resin ontent lies between about 35 and 45 vol% ٠The prepreg is stored at 0 (32 F) or lower beause theroset atrix undergoes uring reations at roo teperature. Also the tie in use at roo teperature ust be iniized. Lie tie is about 6 onths i properly handled. ٠Both theroplasti and therosetting resins are utilized: arbon, glass, and araid ibers are the oon reinoreents. ٠Atual abriation begins with the lay-up. Norally a nuber o plies are laid up to provide the desired thikness. ٠The lay-up an be by hand or autoated. Suary oposites are lassiied aording to: -- the atrix aterial (M, MM, PM) -- the reinoreent geoetry (partiles, ibers, layers). oposites enhane atrix properties: -- MM: enhane y, TS, reep perorane -- M: enhane K -- PM: enhane E, y, TS, reep perorane Partiulate-reinored: -- Elasti odulus an be estiated. -- Properties are isotropi. Fiber-reinored: -- Elasti odulus and TS an be estiated along iber dir. -- Properties an be isotropi or anisotropi. Strutural: -- Based on build-up o sandwihes in layered or. 8