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DAMAGE IN TEXTILE LAMINATES OF VARIOUS INTER-PLY SHIFT Dmitry S. IVANOV, Yao DING, Larissa GORBATIKH, Stepan V. LOMOV, Ignaas VERPOEST Katholieke Universiteit Leuven, Belgium Department of Metallurgy and Materials Engineering Composite

SLIDE 1

DAMAGE IN TEXTILE LAMINATES OF VARIOUS INTER-PLY SHIFT

08.06.2010 ECCM 2010

1 Dmitry S. IVANOV, Yao DING, Larissa GORBATIKH, Stepan V. LOMOV, Ignaas VERPOEST

Katholieke Universiteit Leuven, Belgium Department of Metallurgy and Materials Engineering Composite Materials Group

SLIDE 2

Outline

Numerical expectations Effect of stacking sequence: experiments

–

Thermal crack

–

Acoustic emission: energy, events

–

Crack density

–

Macro properties

2

Mechanisms of deformation: FE analysis

–

Numerical expectations

–

New modelling concept for modelling arbitrary stacking

–

Results

SLIDE 3

Numerical expectations

Strain at… , % Periodic Step Stairs Symmetric Intra-yarn crack, Puck criterion, weft 0.15 0.19 0.22 0.26 Intra-yarn crack, Puck criterion, warp 0.25 0.33 0.37 0.38 Inter-yarn delamination

nset, Mohr-Coulomb

0.34 0.48 0.70 0.86 Fibre failure, Max- 1.13 0.95 0.89 0.87

init

3 Fibre failure, Max- Stress, warp 1.13 0.95 0.89 0.87

Unbalanced twill carbon-epoxy composites, 6 plies

SLIDE 4

Mechanisms of deformation

4 Uniaxial stress state within the 0-yarns Strong shear in the intra-yarn space = higher probability for inta-ply matrix failure Tensile + local shear in the 0- yarns = higher stress along fibres Zero shear in the intra-yarn space

SLIDE 5

Outline

Numerical expectations Effect of stacking sequence: experiments

–

Thermal crack

–

Acoustic emission: energy, events

–

Crack density

–

Macro properties

5

Mechanisms of deformation: FE analysis

–

Numerical expectations

–

New modelling concept for modelling arbitrary stacking

–

Results

SLIDE 6

Stacking effects: manufacturing

Glass plain weave, 850 g/m2, RTM, epoxy, 4 plies, t=3.1 mm 16×17 mm unit cell, Maximum inclination = 9.4°

6 In-phase = periodical stacking Out-of-phase = symmetrical stacking

SLIDE 7

Stacking effects: manufacturing

Glass plain weave, 850 g/m2, RTM, epoxy, 4 plies, t=3.1 mm 16×17 mm unit cell, Maximum inclination = 9.4°

7 In-phase = periodical stacking Out-of-phase = symmetrical stacking

SLIDE 8

Stacking effects: Thermal cracks

Thermal cracking

8 Presence of the intra-yarn cracks: out-of phase only (at the outer plies – through the yarn width)

ut-of phase

in-of phase

SLIDE 9

Stacking effects: Acoustic emission events

50 100 150 200 250 300 1,0E+01 1,0E+02 1,0E+03 1,0E+04 1,0E+05 1,0E+06 1,0E+07 1,0E+08 1,0E+09

Stress [MPa] Energy [eu]

In-phase: periodic stacking

Energy Cumulative Stress

50 100 150 200 250 300

number of events

in-phase

ut-of-phase

ε1 ε2

9

1,0E+00 0,00E+00 5,00E-03 1,00E-02 1,50E-02 2,00E-02 2,50E-02 3,00E-02

Strain

Stress

50 100 150 200 250 1,0E+00 1,0E+01 1,0E+02 1,0E+03 1,0E+04 1,0E+05 1,0E+06 1,0E+07 1,0E+08 0,00E+00 5,00E-03 1,00E-02 1,50E-02 2,00E-02 2,50E-02

Stress [MPa] Energy [eu]

Strain

Out-of-phase, symmetric stacking

Energy Cumulative Stress

between ε1 and ε2 after ε2 Total number of events before ε1

Big difference in the number

f AE events:

In-phase>>Out-of phase ε1 ε2

SLIDE 10

Stacking effects: Acoustic emission energy

1,0E+05 1,0E+06 1,0E+07 1,0E+08 1,0E+09 1,0E+10

nergy(eu)

Cumulative Energy-Strain

In1_2 In1_3 In1_4

ε2 ε1

10

1,0E+00 1,0E+01 1,0E+02 1,0E+03 1,0E+04 0,002 0,004 0,006 0,008 0,01 0,012 0,014 0,016

En Strain

In1_4 In2_1 In2_2

ut1_3
ut1_4

Out1_5

εmin

Big difference in the energy of AE events: In-phase>>Out-of phase

SLIDE 11

Stacking effects: Crack density

0,8 1 1,2 1,4 1,6 1,8

k distance (mm)

Distance between the cracks:

11

0,2 0,4 0,6

crack in-phase

ut-of-phase

in-phase_CNTs

Higher crack density (factor 2) in: In-phase >> Out-of phase

SLIDE 12

Stacking effects: Strength/ ultimate strain

50 100 150 200 250 300 1,4 1,8 2,2 2,6 3

Stress (MPa) Strain (%) In-phase Out-of-phase In-phase-CNTs

12

1 Strain Strength

Out-of-phase

Slightly lower strength for out-of phase

± !

!"±# $"±! %&

'±#("

"±(! ±'( )*&* + ("!±( # ("±(! (#±($ *&* (!'±( ($ ±( (##±(

SLIDE 13

Comparison of 1-ply and 4-ply composites

MPa , σ

4-ply composite Approaching of 4-ply composite curve to the 1-ply composite curve: effect of delaminations

13 % , ε

1-ply composite

NB: a different glass-epoxy PW composite

SLIDE 14

Outline

Numerical expectations Effect of stacking sequence: experiments

–

Thermal crack

–

Acoustic emission: energy, events

–

Crack density

–

Macro properties

14

Mechanisms of deformation: FE analysis

–

Numerical expectations

–

New modelling concept for modelling arbitrary stacking

–

Results

SLIDE 15

Superposition of periodic profiles

To set the correct boundary conditions we have to predict the laminate deformed shape Periodic profile. Ply 1 Periodic profile. Ply 2 “Step”

∞ z

u ~

∞ z

u ~

15 Superimposed profile Deformed profile of a textile laminate can be presented as a arithmetic average of periodic profiles for each of the plies

( ) ( )

∑

= ∞

+ =

N i i z s z

s x u N x u

~ 1 ~

SLIDE 16

Actual and predicted profiles

m uz µ , ~ mm x ,

Superimposed/predicted profile “Step”-wise shift

16 Average profile in the laminate Profiles along the inter-layer boundaries Predicted and average profiles are proportional ⇒ ⇒ ⇒ ⇒ Energy-based scaling is also applicable here The scatter of the profiles is bigger than in the periodic stacking

SLIDE 17

New BC’s

( )

inner inner

uter
uter

N E

11 11 11 11

2 2 ε σ ε σ − + =

( )

inner ij ij

uter

ij ij H

N E ε σ ε σ 2 2 − + = Energy of effective medium Energy of heterogeneous medium Outer and inner unit cells

17 ( )

E H

E E E − = ∆ λ

Number of the plies, N 2 3 4 5 6 Reference solutions 1.725 1.383 1.273 1.210 1.160 Numerical procedure 1.709 1.375 1.253 1.190 1.153 Deviation from the balance Minimisation of the deviation Optimum scaling coefficients

SLIDE 18

Results: FFE vs. ply solution

Layer position

Outer Outer Outer Inner Inner Inner

Configur ation

Step Stairs Periodic Step Stairs Periodic

Transverse stress, warp, [MPa] FFE 60.3–157.6 84.1–161.5 47.1–132.3 74.0–145.8 103.2-169.4 59.5-123.1 UCA 65.3–153.9 100.2–167.1 46.8 – 130.2 78.1–144.4 111.3–170.1 54.8 – 121.2 Transverse stress, weft, [MPa]

σ y σ yz σ

18

Transverse stress, weft, [MPa] FFE 3.7 – 15.1 3.2 – 12.7 3.2 – 15.1 4.7 – 12.3 4.3 – 10.7 3.9 – 15.7 UCA 2.6 – 13.2 3.2 – 11.4 3.4 – 14.7 3.1– 13.9 5.3 – 12.4 3.5 – 15.6 Out-of plane shear stress, weft, [MPa] FFE

5.3–5.9
3.5 – 3.6
8.6–8.6
6.0 – 6.0
2.4 – 2.1
9.5 – 9.5

UCA

6.4–6.4
2.8 – 2.8
8.9–8.9
6.6 – 6.6
2.2 – 2.2
9.7 – 9.7

Good coincidence of the reference full scale solution with “the one-ply +BC” approach

SLIDE 19