AN EXPERIMENTAL INVESTIGATION OF PENETRATION FAILURE MODES IN COMPOSITE LAMINATES

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1 16 TH INTRNATIONAL CONFRNC ON COMPOSIT MATRIALS AN XPRIMNTAL INVSTIGATION OF PNTRATION FAILUR MODS IN COMPOSIT LAMINATS Guiping Zho*, Zhengho Wng**, Jinxin Zhng**, Chongdu Cho*** *MO Key Lbortory for Strength nd Vibrtion, School of Aerospce, Xi n Jiotong University, P.R.Chin ** Deprtent of Civil ngineering, Xi n Jiotong University, P.R.Chin *** Deprtent of Mechnicl ngineering, Inh University, S. Kore Keywords: coposite terils, ipct, high velocity, energy bsorption, dge Abstrct The ipct tests were conducted with highvelocity gs cnnon. Three kinds of stcking sequence coposite lintes [(45/-45) 4 ] s, [(0/45/90/-45) ] s nd [(0/45/90/-45) 4 ] s were ipcted by projectile with velocity of /s. A lser velocity surveying pprtus ws eployed to esure the striking nd residul velocities of the projectiles. The process of ipct perfortion ws observed by tking photogrphs with high-speed fring cer to those trgets. And the ipct frcture behvior nd the energy bsorption property were nlyzed. The bllistic chrcteristics were represented by the experientil foruls which gve the reltionship between the striking nd residul velocities of the projectile. The experientil foruls cn estite the bllistic liit penetrtion velocities nd the residul velocities. 1 Introduction Fiber reinforced coposite terils re used extensively in ilitry nd civil pplictions due to their excellent echnicl properties like high specific strength, specific stiffness, resistnce to corrosion, incresed ftigue life ong others. However, they re susceptible to ipct dge due to their low toughness properties. Coposites tht re used in erospce nd lnd bsed structurl coponents re often subjected to high velocity ipct threts like broken engine prts, turbine bldes, frgents fro bobs, shells, ortrs, nd grendes. There re ny issues tht deterine the response of the coposite terils to ipct threts. These include: type nd volue frction of the fibers, linte thickness, boundry conditions, the trix syste, the ly-up sequence, geoetry, size nd the kinetic energy of the ipctor. A study on ipct response of coposite lintes concluded tht ipct perfortion is the ost iportnt dge stge in coposite lintes subjected to ipct loding. The reson is tht ipct chrcteristics nd echnicl properties degrdtion of coposite lintes rech criticl vlues when perfortion tkes plce [1-3]. In order to investigte ipct perfortion behvior of crbon fiber reinforced coposite, the ipct tests were conducted with high-velocity gs cnnon. The perfortion behviors were evluted by bsorbed energies during perfortion, orphologicl in situ observtions using high-speed fring cers nd postorte observtions. The bllistic chrcteristics were represented by given experientil forul, which gve the reltionship between the striking nd residul velocities of the projectile. Speciens nd Projectile T300 crbon fibers were used in king coposite linte speciens. The weight frction of fibers ws kept constnt t 60%. The trix of the speciens ws fro thero-setting epoxy resin. The cure of ll lintes ws done t roo teperture, 3 0 C, nd reltive huidity 50%. Three kinds of stcking sequence, [(45/-45) 4 ] s, [(0/45/90/-45) ] s nd

2 GUIPING ZHAO, Zhengho Wng, Jinxin Zhng, Chongdu Cho [(0/45/90/-45) 4 ] s were used in the test. The configurtion of the speciens is in plne re nd.4 (4.8) in thickness (Fig. 1). A steel bullet of weight 19.99g ws used s projectile in the test. The size of the bullet is shown in Fig.. chnged fro the ipct energy s to the residul energy r fter perforting specien. The energy bsorbed by the specien ws s - r =0.5(v s -v r ), where is the ss of bullet. After the experients, postorte orphologicl observtions were crried out on the speciens to investigte their filure odes. A seril of highspeed photogrphs of thick-0 specien ipcted t the velocity of 161 /s re shown in Fig. 5. Fig. 1. Diensions of specien (T is the thickness) Fig. 3. Schetic digr of ipct testing Fig.. Diensions of projectile 3 xperients The high velocity ipct tests were de by using gs cnnon. The specien ws ounted in clp supported boundry condition long its four edges. Fig. 3 shows schetic digr of the ipct perfortion experientl setup. Vrying the pressure of gs in the firing chber vried the ipct velocity. The ipct tests were designed to investigte the dge evolution t the bllistic liit. The bullet ccelerted fro 10 to 300 /s by light gs cnnon, ws ejected fro its luncher tube. It pssed velocity esureent device nd verticlly ipcted the center of the front surfce of the specien. A lser velocity surveying pprtus ws eployed to esure the striking velocity v s nd residul velocities v r of the projectile. A typicl signl output fro velocity esureent is shown in Fig. 4. A high-speed fring cer ws used for the in situ observtion of the ipct perfortion behvior. The kinetic energy of projectile ws Fig. 4. Typicl signl output fro velocity esureent Fig. 5. High-speed photogrphs of thick-0 ipcted t the velocity of 161 /s

An experientl investigtion of penetrtion filure odes in coposite lintes 4 Results nd Discussion 4.

For specien nottions, the first word, i.e. thin (thick), represented the thickness of.4 (4.8) speciens.

4 ] s while the lst nuber ws seril nuber of the speciens.

nd 50% re rrested within the bounds of the speciens.

Under this condition, the projectile reins ebedded within the specien, yet visible when viewed fro the rer

This ens the bullet did not penetrte the speciens nd return to the front of the speciens fter ipct due to the

The bullet velocity is t criticl velocity of penetrtions. And Figs 1-14 re coplete penetrtion.

In spite of siilr ipct energies, those frctured in significntly different filure odes.

13), cler squre nd circulr hole were observed on the front surfce, respectively.

3 An experientl investigtion of penetrtion filure odes in coposite lintes 4 Results nd Discussion 4.1 Filure Mode Figs show typicl iges for the front nd rer surfces of the speciens ipcted. For specien nottions, the first word, i.e. thin (thick), represented the thickness of.4 (4.8) speciens. The second nuber 0 stood for stcking sequence [(0/45/90/-45) ] s ([(0/45/90/-45) 4 ] s ) nd 45 for [(45/-45) 4 ] s while the lst nuber ws seril nuber of the speciens. The bllistic liit velocity denoted by v 50 is the threshold velocity t which 50% of the projectiles penetrte, nd 50% re rrested within the bounds of the speciens. We hve considered v 50 s the velocity t which the projectile hs lost eerged fro the rer surfce of the specien. Under this condition, the projectile reins ebedded within the specien, yet visible when viewed fro the rer surfce. Figs.6-8 re rebound cses for three kinds of stcking sequence speciens ipcted. This ens the bullet did not penetrte the speciens nd return to the front of the speciens fter ipct due to the ipct velocity is less thn bllistic liit speed. Figs.9-11 re insert or prtil penetrtion cses. The bullet velocity is t criticl velocity of penetrtions. And Figs 1-14 re coplete penetrtion. In this cse, residul velocity of the bullet cn be esured by the lser velocity surveying pprtus. In spite of siilr ipct energies, those frctured in significntly different filure odes. In both lintes Thin (Fig. 1) nd Thin-0-14 (Fig. 13), cler squre nd circulr hole were observed on the front surfce, respectively. For both lintes, however, delintion ll occurred on the rer surfce in fiber directions, i.e., in horizontl direction for Thin-0-14 nd in 45 0 direction for Thin Fig. 7. Postorte observtions on Thin-0-3 Fig. 8. Postorte observtions on Thick-0-1 Fig.9. Postorte observtions on Thin-45-4 Fig. 10. Postorte observtions on Thin-0-6 Fig. 6. Postorte observtions on Thin-45-3 Fig. 11. Postorte observtions on Thick-0-3 3

GUIPING ZHAO, Zhengho Wng, Jinxin Zhng, Chongdu Cho energy ong speciens. The thickness (Fig.16) nd stcking sequence (Fig.

Postorte observtions on Thin-45-14 () [(0/45/90/-45) ] s nd [(0/45/90/-45) 4 ] s Fig. 13. Postorte observtions on Thin-0-14 Fig. 14. Postorte observtions on Thick-0-8 4.

dditionl dge. The energy bsorption nd projected dge were xiized t this condition.

This ethod ws not cceptble for esuring the exit velocity, v r, s the projectiles exited the lintes t different ngles nd did not lwys pss through the nrrow perture of the

15 shows striking velocities nd bsorbed kinetic energies histogr. In Fig. 15, V s is striking velocity nd K is kinetic energy bsorbed.

4 GUIPING ZHAO, Zhengho Wng, Jinxin Zhng, Chongdu Cho energy ong speciens. The thickness (Fig.16) nd stcking sequence (Fig.16b) of linted coposites re of iportnt roles tht ffected ipct perfortion behvior of the crbon fiber reinforced coposites. Fig. 1. Postorte observtions on Thin () [(0/45/90/-45) ] s nd [(0/45/90/-45) 4 ] s Fig. 13. Postorte observtions on Thin-0-14 Fig. 14. Postorte observtions on Thick Absorbed nergy Once coposite linte ws perforted, ny excess ipct energy would be retined s kinetic energy in the ipctor except tht n insignificnt ount would be converted into dditionl dge. The energy bsorption nd projected dge were xiized t this condition. Hence, perfortion threshold ws n iportnt preter in chrcterizing the ipct response of coposite lintes. The incident velocity, v s, ws esured using chronoscope. This ethod ws not cceptble for esuring the exit velocity, v r, s the projectiles exited the lintes t different ngles nd did not lwys pss through the nrrow perture of the chronoscope. A high speed cer ws lso used to esure the dynic delintion res nd to investigte the pth of the issile through the linte. Fig. 15 shows striking velocities nd bsorbed kinetic energies histogr. In Fig. 15, V s is striking velocity nd K is kinetic energy bsorbed. We could recognize cler differences in the bsorbed (b) [(0/45/90/-45) ] s nd [(45/-45) 4 ] s Fig. 15. Striking velocities nd bsorbed kinetic energies Fig.16. Kinetic energy bsorbed by the coposites A coprison of the effect of ipct velocity on the kinetic energy bsorbed by Thin-45, Thin-0 nd Thick-0 coposites is presented in Fig. 16. It is cler fro the experientl results tht Thick-0 coposites exhibit better projectile energy bsorption cpbility thn the Thin-45 nd Thin-0 coposites.

5 An experientl investigtion of penetrtion filure odes in coposite lintes The bsorbed kinetic energy,, the ipct nd the residul kinetic energies re linked by the eqution, 1 1 = vs v r (1) For the trget, when the shpe nd teril of the projectile re unchnged the bllistic liit velocity is constnt. In other words, when bullet ipcts trget t the bllistic liit velocity v 50, the kinetic energy of the bullet is bsorbed entirely by the trget. 1 1 = v50 () Beyond the bllistic liit, the bsorbed kinetic energy increses with incresing ipct velocity. The difference between nd 1 is ssued to be function of striking velocities of the bullet s following. 1 = f ( vs) (3) Bsed on the experientl results, the expression of f(v s ) cn be obtined experientilly s = f v = v +c (4) ( ) 1 s s where nd c re constnts. Different trgets hve different nd c. The forultion described the reltion of 和 v s cn be expressed by sttisticl dt fro experients. = + (5) 0.041vs = vs = vs (5b) (5c) qs.(5), (5b) nd (5c) re foruls of energy bsorption for coposite lintes Thin-45, Thin-0 nd Thick-0, respectively. Inserting qs. (5), (5b) nd (5c) into q. (1), n experientil forul predicting residul velocity cn be expressed s q.(6) for the linted coposites Thin-45, Thin-0 nd Thick-0, respectively vr = vs (6) v v r r = vs (6b) = vs (6c) 5 Sury Filure echniss nd odes of the crbon/epoxy coposite lintes were observed experientlly during high velocity ipct. The thickness nd stcking sequence of linted coposites re of iportnt roles tht ffected ipct perfortion behvior of the crbon fiber reinforced coposites. In spite of siilr ipct energies, coposite lintes frctured in significntly different filure odes. In stcking sequence [(0/45/90/-45) ] s ([(0/45/90/-45) 4 ] s ) nd [(45/-45) 4 ] s, cler circulr nd squre hole were observed on the front surfce, respectively. The velocity of bllistic liits for the crbon/epoxy lintes ipcted by the projectiles ws predicted using current experientil forul (6) by setting v r equl to zero. Acknowledgeents The uthors wish to thnk the Ntionl Bsic Reserch Progr of Chin through Grnt No. 006CB6010, the Ntionl Science Foundtion of Chin (Grnt No ) nd the Ntionl Science Foundtion (eronuticl joint fund) of Chin (Grnt No ) for finncil support of this work. References [1] Morye S., Hine P. nd et l. Modeling of the energy bsorption by polyer coposites upon bllistic ipct. Coposites Science nd Technology, Vol. 60, pp , 000. [] Liu D., Rju B. nd Dng X. Ipct Perfortion Resistnce of Linted nd Assebled Coposite Pltes. Int. J. Ipct ngineering, Vol. 4, pp , 000. [3] Mines R., Roch A. nd Jones N. High Velocity Perfortion Behvior of Polyer Coposite Lintes. Int. J. Ipct ngineering, Vol., pp ,

NONLINEAR CONSTANT LIFE MODEL FOR FATIGUE LIFE PREDICTION OF COMPOSITE MATERIALS

18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS NONLINEAR CONSTANT LIFE MODEL FOR FATIGUE LIFE PREDICTION OF COMPOSITE MATERIALS T. Prk 1, M. Ki 1, B. Jng 1, J. Lee 2, J. Prk 3 * 1 Grdute School,