Effect of microscopic damage events on static and ballistic impact strength of triaxial braid composites

Transcription

1 Astrct Sumitted to CompTest th Interntionl Conference on Composites Testing nd Model Identifiction Octoer, 2008 Dton, OH Effect of microscopic dmge events on sttic nd llistic impct strength of triil rid composites Justin D. Littell, Wieslw K. Biniend, nd Willim A. Arnold The Universit of Akron, Akron, OH Gr D. Roerts nd Roert K. Golderg NASA Glenn Reserch Center, Clevelnd, OH In previous work, the llistic impct resistnce of triil rided cron/epo composites mde with lrge flt tows (12k nd 24k) ws emined impcting 2 X2 X0.125 composite pnels with geltin projectiles. Severl high strength, intermedite modulus cron fiers were used in comintion with oth untoughened nd toughened mtri mterils. A wide rnge of penetrtion thresholds were mesured for the vrious fier/mtri comintions. However, there ws no cler reltionship etween the penetrtion threshold nd the properties of the constituents. During some of these eperiments high speed cmers were used to view the filure process, nd full-field strin mesurements were mde to determine the strin t the onset of filure. However, these eperiments provided onl limited insight into the microscopic filure processes responsile for the wide rnge of impct resistnce oserved. In order to investigte potentil microscopic filure processes in more detil, qusi-sttic tests were performed in tension, compression, nd sher. Full-field strin mesurement techniques were used to identif locl regions of high strin resulting from microscopic filures. Microscopic filure events ner the specimen surfce, such s splitting of fier undles in surfce plies, were esil identified. Susurfce dmge, such s fier frcture or fier undle splitting, could e identified its effect on in-plne surfce strins. Susurfce delmintion could e detected s n out-of-plne deflection t the surfce. Using this dt, filure criteri could e estlished t the fier tow level for use in nlsis. An nlticl formultion ws developed to llow the microscopic filure criteri to e used in plce of mcroscopic properties s input to simultions performed using the commercil eplicit finite element code, LS-DYNA. The test methods developed to investigte microscopic filure will e presented long with methods for determining locl filure criteri tht cn e used in nlsis. Results of simultions performed using LS-DYNA will e presented to illustrte the cpilities nd limittions for simulting filure during qusi-sttic deformtion nd during llistic impct of lrge unit cell size triil rid composites.

2 Effect of Microscopic Dmge Events on Sttic nd Bllistic Impct Strength of Triil Brid Composites CompTest Conference - Oct. 21, 2008 Dton, Ohio Justin Littell Ph.D. Student Universit of Akron Akron, Ohio Wieslw K. Biniend, Willim A. Arnold Universit of Akron, Akron Ohio Gr D. Roerts, Roert K. Golderg NASA Glenn Reserch Center, Clevelnd Ohio 1

3 Triil Brided Composite Mterils Ail Fier Direction -60 o Fier Direction +60 o Fier Direction Two dimensionl triil rid 24k wide il nd 12k wide is fier tows Lers of +60 o nd -60 o is fiers rided over 0 o il fier Qusi-isotropic rchitecture Lup of 6 Lers of rid, totl composite thickness Resin Trnsfer Molding process (RTM) Volume frction of 56% nominl 2

4 Mterils High Strength, Stndrd Modulus Fier Tor T700 Two resins Toughened Ctec Ccom PR520 Untoughened Hecel 3502 T700 / 3502 T700 / PR520 Presented s emples to cover rnge of mteril response 3

5 Model Development Testing nd modeling were done in prllel Test dt used opticl mesurement techniques to otin full field strin dt Qusi-sttic Testing B emining the test dt nd using clssicl composite theor, new pproch ws developed to model composites using novel Sucell pproch Modeling dt needs Composite section properties rid geometr Composite mteril properties test dt Models developed in LS-DYNA Trnsient, nonliner, eplicit finite element code Primril impct loding tht composites will e sujected 4

6 Photogrmmetr used for Dt Collection Locl Point Strin Glol stress vs. strin curves found creting digitl strin gge Mesures mteril response in specific res on specimen Seen noting lines of high loclized strin Locl filure mechnisms nd deformtions must e ccounted for when developing n nlticl method 5

7 Triil Brided Model Methodolog Develop mcromechnicl finite element model cple of cpturing the rid rchitecture nd mteril properties of triill rided composites Lers of unidirectionl lmin stcked in Sucell configurtion Needs locl lmin level modulus nd filure properties Y X Y X Z -60 o 0 o +60 o Sucell A -60 o +60 o +60 o +60 o -60 o -60 o 0 o Sucell B Sucell C Sucell D Z X Y X X 6

8 Defining the Brid Geometr (Section) Ech prt hs unique section properties Ech section contins informtion out numer of lers (15) nd rid ngle (Θ) t ech ler Brid ws modeled s lers of unidirectionl lmin Shifted (Idelized) 7

9 A New Methodolog Developed for Implementtion of Mteril Properties Otin Fier, Mtri Properties Otin Composite stresses, strins From opticl mesurements Micromechnics - Develop effective lmin properties CLPT - Bck out effective lminte properties CLPT - Develop effective lminte properties Micromechnics - Bck out effective lmin properties Develop FEM (One ler, homogenized) Trditionl Approch (Bottom - Up) Items needed Fier properties - Assumed Mtri properties Stckup sequence Develop FEM (includes lers nd sucell props) New Approch (Top Down) Items needed COMPOSITE TEST DATA Stckup sequence 8

10 Mteril Crd MAT_RATE_SENSITIVE_COMPOSITE_FABRIC $$$$ USING AS TESTED T700s/PR520 Mteril Properties nd mt 158 *MAT_RATE_SENSITIVE_COMPOSITE_FABRIC $ MID RO EA EB (EC) PRBA TAU1 GAMMA E E E $ GAB GAC GCA SLIMT1 SLIMC1 SLIMT2 SLIMC2 SLIMS 2.75E6 1 $ AOPT TSIZE ERODS SOFT FS $ A1 A2 A3 Mteril Coordinte Definition $ D1 D2 D3 Propert $ E11C E11T E22C E22T GMS EA $ XC XT YC YT SC EB 5.469E E E E E+4 $ K 6.762E+6 PRBA Filure Properties Propert Nme Propert Vlue Mteril Response Properties GAB E11C Comp. strin (A.) XC Comp. strength (A.) E11T Tens. Strin (A.) XT Tens. Strength (A.) E22C Comp. strin (Trns.) YC Comp. Strength (Trns.) E22T Tens. strin (Trns.) YT Tens. Strength (Trns.) GMS Sher strin SC Sher Strength Controls elstic/plstic ehvior of filure Vlue Ail Modulus Trns. Modulus In Plne Poisson In Plne Sher Mod. 9

11 Clssicl Lminted Plte Theor (CLPT) Use in Reverse for Top-Down Approch Stresses/Surfce Trctions re relted to strins the following N A11 = N A [ N] [ A] = [ M ] [ B] A12 0 ε A22 0 ε 0 A66 0 [ B] [ ε ] [ D] [ γ ] Blnced nd Smmetric (B nd D mtrices, lso A16, A26 = 0) Where A11 0deg 0deg 60deg 60deg 60deg 60deg = Q11 = Q11 * t + Q11 * t + Q11 * t Q 11 = m Q11+ n Q22 + 2m n Q12 + 4m 2 n 2 Q66 E11 E22 v21* E11 Q 11 =, Q22 =, Q12 =, Q66 = G12 1 v12* v21 1 v12* v21 1 v12* v21 E11, E22, v12, v21, G12 re prmeters needed in LS-DYNA 10

12 Eqution Development Micromechnics of Composite Mterils ssumptions Trnsverse ASTM 3039 specimen V * N = V * N f f c N = N = N = N d Ail ASTM 3039 specimen c d N = N = N = N = 0 N = 0 = A12 * ε + A22 * ε 11

13 Developed Equtions (using Sucell Strins) Sucell B Sucell A Trnsverse Tensile Test Glol Ail Strin Locl Sucell Strins Strins re found using the opticl mesurement sstem In the end, there re 6 vriles (Q11,Q12,Q22,Q66,N,N ) nd 6 equtions 2 from TT Sucells A nd C (CLPT) 2 from TT Sucells B nd D (CLPT) 1 from volume frction verges (Micromechnics) 1 from AT Sucells A nd C (CLPT) Solve simultneousl 12

14 Ail Tensile (AT) Strength Assume tht in AT tests, the AT fier crries most of the lod E11T comes from ultimte strin t AT filure 13

15 Trnsverse Tensile (TT) Strength Look t fier splitting on TT specimen Lod t first split will e YT SLIMT will e set to 1 E22T will e set to filure strin of test YT Stress EB SLIMT = 1 Strin E22T Fiers Strt Splitting E22T =

16 Compressive Strin/Strength Mteril ehves s homogenous Use strength t filure for oth Ail nd Trnsverse tests Use strin t strength for oth Ail nd Trnsverse tests Ail Compression Trnsverse Compression 15

17 Sher Strength Using Modified Sher Specimen Design sed on Kohlmn ASTM 5379 P, N is for ech of the integrtion lers Cn e directl implemented for sher strength LS-DYNA needs ε for GMS Y X P Z X -60 o 0 o +60 o +60 o +60 o +60 o 0 o -60 o -60 o -60 o P 16

18 Finite Element Models Unit Cell Unit Cell Both Ail nd Trnsverse Specimens were developed using ASTM D3039 specimen geometries Fied end oundr conditions were used to simulte the fied grip Loding ws pplied t the opposite end using enforced displcement 17

19 Sttic Results T700 / PR520 T700 / 3502 Ail Tension % Error Strength 12% Modulus 7% % Error Strength 10% Modulus 4% Trnsverse Tension % Error Strength 8% Modulus 9% % Error Strength 25% Modulus 6% 18

20 Determintion of T700 fier / PR520 Resin Impct Chrcteristics Simultions were completed Spring 2008 Showed penetrtion threshold t 630 ft / sec Used s strting point for impct tests Impct tests conducted Summer 2008 Penetrtion threshold ws etween 609 nd 637 ft / sec 19

21 Limittions: Delmintions for T700 fier / 3502 resin OOP displcements verified NDE Glol Mteril response curves ecome non-liner fter delmintions occurred Due to the nture of integrtion point formultion, cnnot simulte ultimte filure vlues etween lers 20

22 Limittions: FEM cnnot simulte fier undle splitting Ail Tension (il strin) Trnsverse Tension (il strin) Opticl Mesurements LS-DYNA Opticl Mesurements LS-DYNA 21

23 Conclusion Stndrdized test methods in conjunction with n opticl mesurement sstem hve een used to collect mteril propert dt for triil rided composite mterils Glol mteril response curves Locl trnsverse fier undle splitting Locl susurfce delmintions A hrid micro-mcromechnicl computer model hs een developed Incorportes rid rchitecture Incorportes tested mteril propert dt Comprisons etween test nd simultion show good greement 10% in sttic simultions Penetrtion threshold in impct simultions Fctors seen in the test dt cnnot e simulted s of now Ongoing work 22

24 Bckup 23

25 Eqution Development Trnsverse Tensile Testing A B C D P, Use ASTM 3039 Trnsverse Tensile coupon geometr N Clssicl composite uniform stress/uniform strin ssumption ields (Prllel to loding) (Perpendiculr to loding) N = N = N = c N d V * N = V * N f f 24

26 Rewriting the equtions for ech Sucell (Trnsverse Tensile Testing) Sucell A N is pplied lod nd ll strins re found from opticl mesurement sstem N = A11 * ε + A12 * ε N = A12 * ε + A22 * ε Sucell B N is pplied lod nd ll strins re found from opticl mesurement sstem N = A11 * ε + A12 * ε N = A12 * ε + A22 * ε Four Equtions 25

27 Eqution Development Ail Tensile Testing P, N Clssicl composite lminte micromechnics ssumptions ield N N = = N = N c = N d = 0 0 = A12 * ε + A22 * ε 26

28 Advnced Dt Anlsis Toughened Fier Bundle Splitting Trnsverse Testing Locl Strin vs Glol Stress T700s Fier / PR520 Resin Toughened Ail Identif locl filure strin Locl filure initition correltions to glol nonlinerities Stress (MP) Trnsverse Strin % 27

29 T700 Fier / PR520 Resin Sttic Results Ail Tension Ail Tension Modulus (psi) Ail Tension Strength (psi) Test 6.8E6±1.6E5 1.52E5±4.9E3 LS-DYNA 7.4E6 1.31E5 % Error 7% 12% Trnsverse Tension Trnsverse Tension Modulus (psi) Trnsverse Tension Strength (psi) Test 6.2E6±2.3E5 8.69E4±4.3E2 LS-DYNA 5.6E6 9.38E4 % Error 9% 8% 28