1/27 COMPTEST’2006 – 10 to 12 of April of 2006 – University of Porto – Portugal Experimental and numerical studies of mode I,II, III and mixed-mode I-II energy release rate in laminates EXPERIMENTAL AND NUMERICAL STUDIES OF MODE I, II, III AND MIXED-MODE I-II ENERGY RELEASE RATE IN LAMINATES Rosa Marat-Mendes, Manuel de Freitas [email protected]
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COMPTEST’2006 – 10 to 12 of April of 2006 – University of Porto – PortugalExperimental and numerical studies of mode I,II, III and mixed-mode I-II energy release rate in laminates
EXPERIMENTAL AND NUMERICAL STUDIES OF MODE I, II, III AND MIXED-MODE I-II
Experimental ProcedureMode IMixed Mode I-IIMode IIMode III
ResultsExperimentalAnalytical
Conclusions
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IntroductionLamination of composite structures is one of the most common manufacturing techniques used in the construction of composite components. One of the limiting factors of laminated structures is a failuremode known as delamination, which is the separation of individual layers of the laminated structure.There are three fundamental fracture modes for the crack propagation:
Mode I Mode II Mode III
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IntroductionIn reality delamination can occurs with a sobrepositionof the three modes. The Mixed Mode Bending (MMB) test combines the mode I (DCB) and the mode II (ENF) tests.In this work it is used the mode I, the mode II, the mode III separately and also a combined test of the two modes I and II to predict the delamination in mixed mode I-II.
+ =
Mode I(DCB)
Mode II(ENF)
Mixed Mode I-II(MMB)
L La
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The material used was a UE400 REM GLASS UD PREPREG from SEAL.- epoxy resin ET443- reinforced with unidirectional E glass fibers
The artificial pre-crack has been achieved inserting a single 13μm thick Teflon-foil Type A-FEP from Dupont in the mid plane of the specimens.
No standardizationUse of standard D6671-01 ASTM (Mixed Mode I-II) with c=0
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Mode III (ECT)ECT – Edge crack torsion
No standardizationBased on Lee (1993)
Support Pins
Specimen
Loading Pin
Specimen
Guide Pins
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Experimental ProcedureAn Instron 5544 with a load cell of 2kN was used, with software Merlin.The samples were loaded continuously in displacement control with a rate of 0.5mm/min. The Load-displacement plot was recorded during the test.
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Experimental Results – Mode I and Mode IILoad-Displacement for Mode I (DCB) - UD_V_01_2
0
20
40
60
80
100
120
140
160
0 2 4 6 8 10 12
Dispalcement [mm]
Apl
ied
Load
[N]
Load-Displacement for Mode I (DCB) - UD_V_01_1
0
20
40
60
80
100
120
140
160
0 3 6 9 12 15
Displacement [mm]
Apl
ied
Load
[N]
Load-Displacement for Mode II (ENF) - UD_V_01_5
-1300
-1100
-900
-700
-500
-300
-100
-7-6-5-4-3-2-10
Displacement [mm]
Aplie
d Lo
ad [N
]
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Experimental Results – Mixed Mode I-II and Mode III
Load-Displacement for Mixed Mode I+II (MMB) UD_V_01_6
-280
-230
-180
-130
-80
-30
-11-9-7-5-3-1
Displacement [mm]
Aplie
d Lo
ad [N
]
Load-Displacement for Mixed Mode I+II (MMB) UD_V_01_7
-250
-200
-150
-100
-50
0-11-9-7-5-3-1
Displacement [mm]
Aplie
d Lo
ad [N
]
Load-Displacement for Mixed Mode I+II (MMB) UD_V_01_4
-450-400-350-300-250-200-150-100-50
0-10.0-8.0-6.0-4.0-2.00.0
Displacement [mm]
Aplie
d Lo
ad [N
]
Load-DIsplacement for Mode III (ECT) - UD_V_04
-2500
-2000
-1500
-1000
-500
0-11-9-7-5-3-1
Displacement [mm]
Aplie
d Lo
ad [N
]
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Results – Numerical SimulationFinite Element Analysis using ANSYS® with solid elements 46 Layered.
Mode I – DCB
Mode II – ENF
Mixed Mode I-II – MMB
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Results – Numerical Simulation
Mode III – ECT
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Results FEM – Strain energy release rate
DCB Test with VCCT (UD_V_01_1i)
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
0 0.2 0.4 0.6 0.8 1
x/L
G [J/mm2] GI
GII
GIII
ENF Test with VCCT (UD_V_01_5b)
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0 0.2 0.4 0.6 0.8 1
x/L
G [J/mm2]GI
GII
GIII
MMB Test with VCCT (UD_V_01_8g)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0 0.2 0.4 0.6 0.8 1
x/L
G [J/mm2]
GI
GII
GIII
ECT Test with VCCT (UD_V_04_19A)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 0.2 0.4 0.6 0.8 1
x/L
G [J/mm2] GIGIIGIII
Load Point Support Point
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Strain energy release rate – Mode I
GI for UD_V_01
0
0.2
0.4
0.6
0.8
1
1.2
1.4
30 35 40 45 50 55 60 65 70 75 80
a [mm]
GI [J/mm2]
Experimental MBTExperimental CCExperimental MCCBeam Theory MBTBeam Theory CCBeam Theory MCCVCCT
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Strain energy release rate – Mode II
GII for UD_V_01_5
0.00.20.40.60.81.01.21.41.61.8
20 30 40 50 60 70
a [mm]
G [J/mm2]
Experimental
Beam Theory
VCCT
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Strain energy release rate – Mixed Mode I-II
Gc=GI+GII for UD_V_01_8
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
0 10 20 30 40 50 60 70 80
a [mm]
Gc [J/mm2]
Experimental
Beam Theory
VCCT
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Fracture Toughness vs Mode Mixture
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mixed Mode ratio GII/Gc
Gc
[J/m
m
2 ]
ExperimentalBeam theoryVCCT
DCB, Pure Mode I MMB, Mode I and II ENF, pure Mode II
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Strain energy release rate – Mode III
GIII for UD_V_04
0.0
1.0
2.0
3.0
4.0
5.0
6.0
12.0 14.0 16.0 18.0 20.0 22.0 24.0
a [mm]
G [J/mm2]
GIIIc (NL) exp
GIIIc (5%) exp
GIIIc (5%) VCCT
GIII (NL) VCCT
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Mode I, Mode II, Mode III
0
0.5
1
1.5
2
2.5
3
3.5
4
G [J/mm2]
GI VCCTGII VCCTGIII VCCT
0
0.5
1
1.5
2
2.5
3
3.5
4
G [J/mm2]
GI ExpGII ExpGIII Exp
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ConclusionsAn analytical and experimental investigation was carried out on a glass/epoxy laminates to evaluate the Double cantilever beam (DCB), the End notch flexure (ENF), the Mixed mode bending (MMB) and the Edge crack torsion (ECT) interlaminar fracture toughness tests for laminated composites.
The mixed mode I-II procedure permits the simulation of delamination initiation in mode I and mode II simultaneous.
A three dimensional finite element analysis was used to compare the results calculated by the beam theory and by the VCCT technique with the experimental values.
The experimental results determined for mode I, mode II and mixed mode I-II are very close to the Finite Element using either Beam Theory and VCCT.
Using ECT test it can be obtained pure mode III at the middle ofthe specimen length away from both ends.
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THANK YOU
Rosa Marat-Mendes wishes to thank the support from the FCT (Fundaçãopara a Ciência e Tecnologia) for the PhD grant no. SFRH/BD/25561/2005.