Comparison of the tensile properties of 3D woven and plain woven composites

Transcription

1 Comparison of the tensile properties of D woven and plain woven composites Alexander Bogdanovich, Dmitry Mungalov, Tex, USA Dmitry S. Ivanov, Stepan V. Lomov, Ignaas Verpoest Department MTM, K.U. Leuven downloaded from: 1

2 Contents D glass fabric and plain woven laminate Test methodology and equipment Results Elastic constants and tensile diagrams Damage initiation and AE diagrams Conclusions downloaded from: 2

3 D glass fabric and plain woven laminate Test methodology and equipment Results Elastic constants and tensile diagrams Damage initiation and AE diagrams Conclusions downloaded from:

4 Problem statement Composites fabricated by VARTM technology with the use of relatively thick, single layer D woven preforms are gaining fast growing interest. It is now well understood and appreciated that this class of advanced composites provides efficient delamination suppression, damage tolerance, and is superior over 2-D fabric laminates in impact, ballistic and blast performance. However, one primarily important question has not been convincingly answered yet: how do the in-plane elastic and strength characteristics compare for -D woven composites and their laminated 2D fabric counterparts. downloaded from: 4

5 Aim Compare D woven composite and plain weave laminate basic in-plane elastic and strength properties: a single layer (unitary) D woven composite vs respective properties of 2D fabric laminate same glass rovings inside equivalent areal density; equivalent thickness and fibre volume fraction, fabricated by identical methods in the same laboratory conditions + provide validation data for WiseTex/TexComp, MOSAIC, FE modelling downloaded from: 5

6 Internal structure of D and plain weave composites Note: 1. Slight crimp of the fill caused by compaction in VARTM 2. Almost rectangular shape of the cross-sections Plain weave laminate Crimped warp/weft, nested plies downloaded from: 6

7 Parameters of D and plain woven fabric D GE044 Plain weave 4 plies: 0 /90 /90 /0 Fabric and composite plate 1 ply Fabric and composite plate 4 ply Areal density, g/m2 255 Areal density, g/m2 260 Thickness, mm 2.6 Thickness, mm 2.45 Ends (straight) per cm per layer 2.76 Ends per cm 5.08 Picks per cm 2.64 Picks per cm 6.19 Z-yarns per cm 2.76 VF, % 48.9 VF, % 52.4 Yarns tex Yarns tex Warp Warp and weft 2275 layer 1, 2275 layer Z-yarns 276 Fill (double yarns) layer 1, layer 2, 1470 Warp : Fill : Z = 49% : 48% : 2% downloaded from: 7

8 D glass fabric and plain woven laminate Test methodology and equipment Results Elastic constants and tensile diagrams Damage initiation and AE diagrams Conclusions downloaded from: 8

9 Tensile test with acoustic emission ASTM D09M 00 INSTRON 4505 Sample 250x25 mm (gauge 180 mm) Load cell 100 kn Speed 1 mm/min downloaded from: 9

10 Acoustic emission: Events and cumulative energy diagram 1.00E E E+07 H1 H2 1.00E+06 energy 1.00E E E E E E sig, MPa downloaded from: 10

11 Optical extensometer: LIMESS Vic2D ave H x H x x, y H Q ave y H H H y ave x ave y x, y Apart from the averaging, surface strain fields are available downloaded from: 11

12 Optical damage observation The samples were placed in between the lamp and the camera. The lamp was directed at a frame with Teflon sheet (to get homogeneous illumination), where the samples were fixed. Several images over the length of the samples were made. No cracks are found on the initial undeformed samples. Cracks could be seen on all the samples at H1 and H2 D sample loaded to H2 downloaded from: 12

13 Plan of the tests Fabric Direction Till failure Till eps2 Till eps1 Total GE044 MD 9 CD 9 BD 9 27 Plain weave MD 9 BD Young Poisson Ultimate H H downloaded from: 1

14 D glass fabric and plain woven laminate Test methodology and equipment Results Elastic constants and tensile diagrams Damage initiation and AE diagrams Conclusions downloaded from: 14

15 Elastic constants Moduli, Poisson coefficients E, Mpa GE044 PW Poisson GE044 PW Warp Fill 45 0 Warp Fill 45 - No difference in Young moduli - Decreased Poisson for the D fabric (inside the scatter?) downloaded from: 15

16 Tension diagrams Tension in warp/fill direction, Tension in 45 direction(up to failure) stress, MPa GEO44, warp GEO44, fill PW stress, MPa GEO44 PW strain, % strain, % - No difference in diagrams - Nonlinearity in fibre direction from eps1 downloaded from: 16

17 Strength Ultimate elongation Strength, MPa GE044 PW Strength, MPa GE044 PW Warp Fill 45 0 Warp Fill 45 D composite: higher strength (+10%), higher elongation downloaded from: 17

18 Damage thresholds Damage strain thresholds D composite: increase of damage initiation thresholds by 0.2% strain for loading in fibre direction Strain, % GE044, eps1 GE044, eps2 PW, eps1 PW, eps2 - advantage in fatigue life stress limit can be expected - lower damage thresholds for loading in bias direction 0 Warp Fill downloaded from: 18

19 AE diagrams Typical AE registration, warp/fill test direction 1.00E+09 - shift of the threshold strains AE energy 1.00E E E E+05 D_W_p1_1 events D_F_p1_4 events PW_W_p1_1 events - higher energy of the events for D composites 1.00E+04 Typical AE registration, 45 test direction 1.00E strain, % 1.00E E+08 AE energy 1.00E E E+05 D_45_p2_ events PW_45_p2_2 events 1.00E E strain, % downloaded from: 19

20 Damage development (loading in fibre direction) D warp D fill eps_1 eps_2 eps_ult plain weave downloaded from: 20

21 Damage development (loading in bias direction) D 45 eps_1 eps_2 eps_ult plain weave 45 downloaded from: 21

22 LIMESS strain field registration (to be further processed) D plain weave The red spots indicate the crack positions downloaded from: 22

23 D glass fabric and plain woven laminate Test methodology and equipment Results Elastic constants and tensile diagrams Damage initiation and AE diagrams Conclusions downloaded from: 2

24 Conclusions 1. D and 2D woven glass/epoxy composite mechanical properties and damage behaviour in tensile test have been compared in the equivalent composite parameters, production and testing conditions 2. Elastic constants of D and 2D woven composites are very close. D woven composites show increased strength and damage initiation thresholds then their 2D woven analogs 4. Damage development in glass/epoxy D woven composites conforms to the scheme established earlier for 2D woven, braided, non-crimp carbon/epoxy composites downloaded from: 24