Recent developments in toughening of composites

Transcription

1 Recent develpments in tughening f cmpsites Ignaas Verpest Larissa Grbatikh, Yentl Swlfs Cmpsite Materials Grup, Department f Materials Engineering KU Leuven (Belgium)

2 Cmpsite Materials Grup Cmpsites n micr- and nan- level Larissa Grbatikh Prcessing and prduct develpment Jan Ivens Frederik Desplentere Cmpsites n macr- and mes- level Stepan Lmv, CMG crdinatr Physical chemistry f cmpsites David Seven Natural and bicmpsites Aart Van Vuure funded 1982, Prf Ignaas Verpest 2

3 Cntents f this lecture Tw research gals: Imprving tughness in fibre-dminated lading cnditins imprtance: - Increase wrk f (ttal) fracture - Influence ther in-service prperties like pen hle tensin.cmpressin, fatigue, impact, Slutins: 3 cncepts: Intra-layer Inter-layer fibre-by-fibre (intra-yarn) Imprving tughness in ther lading/stress cnditins imprtance: gradual damage develpment Slutins: - Hierarchical / nan-engineered cmpsites 3

4 Tughening & hybridisatin: the start 2003: discussin with Arn Detaeye, VP R&D f Samsnite: why are (almst) n cmpsites used in suitcases? Answer: yes, cmpsites are stiff, strng and light but t brittle Majr requirements fr luggage applicatins: Lightness, cmbined with reasnable stiffness Resistance against impacts (falling frm > 1m, in laded -12 C (carg bay cnditins) Ptential candidate: self-reinfrced PP Cmbines just OK stiffness (~= 4 GPa) With high tughness: Failure strain > 15% (CFRP ~= 1,5%) Penetratin impact resistance > 15 J/mm (CFRP < 5 J/mm) Jint Samsnite - KU Leuven develpment f Prcessing f wven tapes laminates cmpressin mulded shells Material ptimisatin leading t mst successful Samsnite suitcase line ever! 4

5 Tughening & hybridisatin: the start - 2 Next questin: can it be a little stiffer, withut lsing tughness? Answer: hybridisatin! 5

6 Our apprach: hybridizatin f SRPP with stiff/brittle fibers 3 hybrid types Swlfs et al Cmpsites A (2015)

7 Layer-by-layer hybrids: new results Fundamental differences in behavir f CF/SRPP hybrids based n cntinuus UD and discntinuus randm carbn fiber layers Fragmentatin + delaminatin Fragmentatin + tape debnding Pseud-ductile behavir! Swlfs et al., Cmpsite Structures 131 (2015) Selezneva et al., Prceedings ECCM-17 (2016) Cllabratins with Tray, University f Bristl and Leeds

8 Layer-by-layer hybrids: randm CF-PP Web 1 mm SRPP 10 mm 6 mm lng carbn fibres Plyprpylene (PP) films Carbn fibres Internal V f = 17 % Hybrid 2/2 twill PP tape fabric PP fabric PP films PP fabric 8

9 Layer-by-layer hybrids: randm CF-PP Pseud-ductility was achieved with V f < 7 % Stiffness x 3 Yield stress x 3 while maintaining tughness V f = 16.7 % (pure web) V f = 9.8 % V f = 8.6 % V f = 6.9 % V f = 4.4 % V f = 0 % (pure SRPP) 9

10 Layer-by-layer hybrids: randm CF-PP Pseud-ductile samples underg fragmentatin and develp checkered-pattern damage (a) 25 mm (a) (b) Web fragmentatin (b) Checkered-pattern 10

11 Tensile results failure mechanisms Checkered-pattern n the surface is related t Twill mes-structure f the material Debnding f the lngitudinal tapes 6 mm Size f SRPP unit cell Edge fr micrscpy Debnded tapes Debnding is arrested in these regin 11

12 Layer-by-layer hybrids with SRPP What we learned: Distinct fractures in UD-CF layer lead t saw-tth / unstable stress-strain curve Mre fuzzy fractures (either inside r due t fuzzy delaminatins) seem t lead t a smther stressstrain curve try t trigger mre gradual fracture f stiff&brittle layer by Intrducing discntinuities! 12

13 Mes-scale discntinuities t intrduce ductility 13

14 Micr-scale discntinuities yield a mre gradual transitin a cmbinatin f aligned shrt carbn fibre/pp prepregs (frm Bristl) with wven SRPP n lad drps, mre gradual transitin frm CF-failure t SRPP failure 14

15 Frm discntinuus layers t intra-yarn hybrids Micr-discntinuities Lead t mre gradual transitin frm CF-failure t SRPP failure UD-layers almst lk like fine arrays f individually brken fibres Investigate ptential f fibre-by-fibre hybridisatin (very) thin layer hybridisatin try t understand their effect by mdelling 15

16 Tughening in thin ply / fibre-by-fibre hybrids A versatile mdel t predict strength f (carbn/glass) hybrids Single fibre layer Tw fibre layer Fur fibre layer Eight fibre layer One f the cnclusins: Thin layer hybrids lead t a higher hybrid effect than cmingled nes. Swlfs et al., Cmpsites: Part A 69 (2015)

17 Validatin f the mdels fr 1 fibre cmpsites Synchrtrn radiatin cmputed tmgraphy data Understanding frmatin f fiber breaks and their clustering Cllabratin with University f Suthamptn (H. Mrtn, A.E. Sctt, P.A.S. Reed, I. Sinclair, S.M. Spearing) Swlfs et al, Cmpsites A 2015

18 What is next? Innvative Training Netwrk FiBreMD Fibre break mdels fr Designing nvel cmpsite micrstructures and applicatins Starting date: Octber 1 st 2016 Partners: T advance state-f-the-art cmpsite failure mdels t reach the required levels f accuracy and t develp characterizatin techniques fr measuring the input data.

19 Cntents f this lecture Tw dmains: Imprving tughness in fibre-dminated lading cnditins Slutins: - 3 cncepts: Intra-layer Inter-layer fibre-by-fibre (intra-yarn) Imprving tughness in ther lading/stress cnditins imprtance: gradual damage develpment Pssible slutin: - Hierarchical / nan-engineered cmpsites 19

20 Anther tughness, anther apprach Tughness is mre than stress/strain/energy up t ttal failure nset and develpment f damage is smetimes equally/mre imprtant! Mes-level Micr-level 20

21 The next level f engineering is at the nanscale Ways t include CNTs in cmpsites

22 Carbn fiber and carbn nanstructure develpment Grbatikh et al, MRS Bulletin, September issue,

23 Understanding thrugh mdelling: transverse lading Versatile tw-scale mdels Strng hetergeneity in stress fields Dispersed CNTs Agglmerated CNTs Randm CNT frests Aligned CNT frests Rmanv et al, CSTE 2015 Rmanv et al., Carbn 2015 Rmanv et al, Cmp A, 2014 Rmanv et al, Cmp structures, 2015

24 Cmpsites with CNT reinfrced matrices

25 Effect f nantubes agglmeratins Create additinal and exacerbate existent μ-scale stress cncentratins

26 Stresses at the fiber/matrix interface Rmanv et. al. (2014), Cmpsite Structures Larger size Higher density Pr dispersin higher μ-scale stress cncentratins

27 Develping experimental tls at the micr-scale Micrscpic fibers tgether with nantubes Matlab cde Spline: CNT in 3D Output: crdinates f pints Pythn script ABAQUS CNTs - curved 3D slid r hllw cylinders Rmanv et. al. (2015), Carbn

28 Effect f nantubes n stresses High stress hetergeneity Suppressin f interface stresses High stresses in matrix rich znes Rmanv et al. (2015), Cmpsite Science and Technlgies

29 Cnclusin Tw appraches: Imprving tughness in fibre-dminated lading cnditins Slutins: 3 cncepts fr stiffening SRPP while keeping tughness Intra-layer Inter-layer fibre-by-fibre (intra-yarn) Investigate ptential t transfer cncepts t CFcmpsites!? Imprving tughness in ther lading/stress cnditins Slutins: - Hierarchical / nan-engineered cmpsites Cntrl f CNT-dispersin is crucial!