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Damage. Visco-elastic. Visco- plastic. L. Rozite and R. Joffe Luleå University of Technology, S-97187 Luleå, SWEDEN. www.ltu.se roberts.joffe@ltu.se. - PowerPoint PPT Presentation
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Analysis of the nonlinear behavior of bio-based polymers reinforced with flax fibers
L. Rozite and R. Joffe Luleå University of Technology, S-97187 Luleå, SWEDEN
The Objective of this study was to analyze nonlinear behavior of flax fiber bio-based polymers composites. Influence of moisture also has been analyzed.
Acknowledgment
Financial support by EU sixth framework programme project “New class of engineering composite materials from renewable resources”, BIOCOMP. Specimens were supplied by Tecnaro (Germany).
17th International Conference on Mechanics of Composite Materials, May 8 – June 1, 2012, Riga, Latvia
www.ltu.seroberts.joffe@ltu.se
Materials
Scanning electron microscope images for PLA-NF10 (left), Lignin/FL30 (middle) and for comparison viscose fiber composite PLA-VF5 (right)
Summary
Material model was developed assuming that possible sources of the observed behavior may be microdamage related stiffness reduction, nonlinear viscoelasticity as well as viscoplasticity. The model was rewritten in an incremental form where stress is a function
of strain to simulate strain controlled tests. The simulated stress-strain curves in tensile test showed satisfying agreement with experimental data. Increase of moisture level in material decreases mechanical properties of composite.
Damage Visco-elastic Visco-plastic
td
d
gdSgd VP
t
,2
010max
Material model
Notation Matrix Fibers/length/ weight fraction
PLA-NF10 PLA Flax/1 mm/10%
Lignin/FL30 Lignin Flax/1mm/30%
PLA-VF5 PLA Viscose/2 mm/5%
Mechanical behaviorStress-strain curves
0
5
10
15
20
25
30
35
0.00 0.01 0.02 0.03 0.04 0.05
Strain (mm/mm)
Str
ess
(MP
a)
PLA-VF5
PLA-NF10
LIGNIN/FL30
PLA-NF10
0
5
10
15
20
25
30
35
0.00 0.01 0.02 0.03 0.04 0.05
Strain (mm/mm)
Str
ess
(MP
a)
RH =34%
RH=66%
RH (%) Material E, (GPa) εmax, (%) σmax, (MPa) εfail, (%) σfail, (MPa)
34
PLA-NF10 3.05 (0.11) 1.50 (0.05) 29.5 (1.0) 4.1 (0.6) 25.4 (1.5)
PLA-VF5 2.35 (0.06) 1.40 (0.05) 26.8 (0.4) 2.8 (0.6) 21.4 (1.2)
LIGNIN/FL30 6.54 (0.41) 0.40 (0.01) 22.1 (1.2) 0.8 (0.3) 21.1 (1.5)
66
PLA-NF10 2.60 (0.24) 1.41 (0.03) 26.1 (0.2) 2.6 (0.7) 21.8 (1.0)
PLA-VF5 2.30 (0.08) 1.37 (0.03) 25.0 (0.1) 2.9 (0.9) 17.3 (0.8)
LIGNIN/FL30 5.99 (0.16) 0.41 (0.01) 20.3 (0.1) 1.3 (0.4) 18.8 (0.3)
E Damage
Lignin FL30, RH=66%
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
5 10 15 20 25
Stress (MPa)
No
rmal
ized
mo
du
lus
max
0max
E
Ed
Visco-plasticityLignin FL30, RH=34%
0
0.2
0.4
0.6
0.8
0 5000 10000 15000 20000 25000
Time (s)
Str
ain
(%
)
16 MPa
15,5 MPa
15 MPa
14 MPa
12 MPa
Lignin FL30, RH=34% (m=0.6)
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0 0.2 0.4 0.6 0.8 1 1.2 1.4t/t*
Str
ain
(%
)
16 MPa
15,5 MPa
15 MPa
14 MPa
Visco-elasticityLignin FL30, RH=34%
0
0.2
0.4
0.6
0 2000 4000 6000 8000 10000
Time (s)
Str
ain
(%
)
16 MPa
15.5 MPa
15 MPa
14 MPa10 MPa
6 MPa
SimulationStress-strain curves
0
5
10
15
20
25
30
0 0.2 0.4 0.6 0.8 1 1.2
Strain (%)
Str
ess
(MP
a)
experimental curves
modeling curve
elastic response
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