fracture behaviour of polymeric composites
TRANSCRIPT
Fracture behaviour of polymer and polymeric
composites.
Harish.L
AM13D025ME7190 Term paper presentation
16th April, 2014
Harish L (AM13D025) 16thApril, 2014 1 / 39
Outline
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 2 / 39
Introduction
Contents
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 3 / 39
Introduction
Introduction
Wind turbine blades are usually fabricated from fiber reinforcespolymeric composites.
Spiral Notch Torsion Test (SNTT)
The current standard fracture toughness test are not efficientunder mixed mode loading conditions, especially ModeI+ModeIII
Figure : Schematic diagram of SNTT
Harish L (AM13D025) 16thApril, 2014 4 / 39
Introduction
Introduction
Wind turbine blades are usually fabricated from fiber reinforcespolymeric composites.
Spiral Notch Torsion Test (SNTT)
The current standard fracture toughness test are not efficientunder mixed mode loading conditions, especially ModeI+ModeIII
Figure : Schematic diagram of SNTT
Harish L (AM13D025) 16thApril, 2014 4 / 39
Introduction
Introduction
Wind turbine blades are usually fabricated from fiber reinforcespolymeric composites.
Spiral Notch Torsion Test (SNTT)
The current standard fracture toughness test are not efficientunder mixed mode loading conditions, especially ModeI+ModeIII
Figure : Schematic diagram of SNTT
Harish L (AM13D025) 16thApril, 2014 4 / 39
Introduction
Introduction
Wind turbine blades are usually fabricated from fiber reinforcespolymeric composites.
Spiral Notch Torsion Test (SNTT)
The current standard fracture toughness test are not efficientunder mixed mode loading conditions, especially ModeI+ModeIII
Figure : Schematic diagram of SNTT
Harish L (AM13D025) 16thApril, 2014 4 / 39
Spiral Notch Torsion Test
Contents
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 5 / 39
Spiral Notch Torsion Test
SNTT
Only shallow surface notch is required for testing brittlematerials thus it significantly reducing specimen size.
Mode1 fracture toughness is obtained when cylindrical specimenhaving pitch angle 45o .
The SNTT test methods has advantages relative to bend-beamtesting, because
The size effect is minimisesNo free surface(normal to the specimen axis) exists in theSNTT specimen geometry under pure torsionMixed mode fracture toughness values can be easily obtained bychanging the pitch angle of the spiral line.
Harish L (AM13D025) 16thApril, 2014 6 / 39
Spiral Notch Torsion Test
SNTT
Only shallow surface notch is required for testing brittlematerials thus it significantly reducing specimen size.
Mode1 fracture toughness is obtained when cylindrical specimenhaving pitch angle 45o .
The SNTT test methods has advantages relative to bend-beamtesting, because
The size effect is minimisesNo free surface(normal to the specimen axis) exists in theSNTT specimen geometry under pure torsionMixed mode fracture toughness values can be easily obtained bychanging the pitch angle of the spiral line.
Harish L (AM13D025) 16thApril, 2014 6 / 39
Spiral Notch Torsion Test
SNTT
Only shallow surface notch is required for testing brittlematerials thus it significantly reducing specimen size.
Mode1 fracture toughness is obtained when cylindrical specimenhaving pitch angle 45o .
The SNTT test methods has advantages relative to bend-beamtesting, because
The size effect is minimisesNo free surface(normal to the specimen axis) exists in theSNTT specimen geometry under pure torsionMixed mode fracture toughness values can be easily obtained bychanging the pitch angle of the spiral line.
Harish L (AM13D025) 16thApril, 2014 6 / 39
Spiral Notch Torsion Test
SNTT Testing
A servo hydraulic axial/torsional testing machine was used toperform SNTT.
Figure : (a) machined epoxy samples and (b) SNTT testing setup
Harish L (AM13D025) 16thApril, 2014 7 / 39
Spiral Notch Torsion Test
SNTT Testing
A servo hydraulic axial/torsional testing machine was used toperform SNTT.
Figure : (a) machined epoxy samples and (b) SNTT testing setup
Harish L (AM13D025) 16thApril, 2014 7 / 39
Spiral Notch Torsion Test
Contd.
Samples were either fractured as machined or after cyclingfatigue with a fixed loading rate 4.52Nm/s.
The in situ fracture process of epoxy samples was examinedusing an infrared camera.
After SNTT testing, the fracture surface were examined byoptical microscopy, scannig electron microscopy, and white lightinferometer.
Harish L (AM13D025) 16thApril, 2014 8 / 39
Spiral Notch Torsion Test
Contd.
Samples were either fractured as machined or after cyclingfatigue with a fixed loading rate 4.52Nm/s.
The in situ fracture process of epoxy samples was examinedusing an infrared camera.
After SNTT testing, the fracture surface were examined byoptical microscopy, scannig electron microscopy, and white lightinferometer.
Harish L (AM13D025) 16thApril, 2014 8 / 39
Spiral Notch Torsion Test
Contd.
Samples were either fractured as machined or after cyclingfatigue with a fixed loading rate 4.52Nm/s.
The in situ fracture process of epoxy samples was examinedusing an infrared camera.
After SNTT testing, the fracture surface were examined byoptical microscopy, scannig electron microscopy, and white lightinferometer.
Harish L (AM13D025) 16thApril, 2014 8 / 39
Spiral Notch Torsion Test
SNTT Testing and Fractographic charecterisation
All epoxies samples exhibited linear elastic behaviour duringSNTT, it is expected for brittle materials such as epoxies.
Figure : Example loading curves during final fracture tests performed on epoxy samples in this study.
Different materials and different geometry exhibit differentbehaviour during SNTT testing.
Harish L (AM13D025) 16thApril, 2014 9 / 39
Spiral Notch Torsion Test
SNTT Testing and Fractographic charecterisation
All epoxies samples exhibited linear elastic behaviour duringSNTT, it is expected for brittle materials such as epoxies.
Figure : Example loading curves during final fracture tests performed on epoxy samples in this study.
Different materials and different geometry exhibit differentbehaviour during SNTT testing.
Harish L (AM13D025) 16thApril, 2014 9 / 39
Spiral Notch Torsion Test
Contd
Figure : IR Images of an epoxy sample during SNTT testing
The primary IR resultsverified that the notchgroove was subjected totensile states underSNTT pure torsionloading.
Harish L (AM13D025) 16thApril, 2014 10 / 39
Spiral Notch Torsion Test
Mode1 Fracture
Figure : Optical microscope images showing:(a) the crack plane and (b) the fracture surface of aMode1 sample fractured without fatigue pre-crack
Figure : Fracture surface of a mode1 sample fractured after cycling fatigue: (a) an optical microscopyimage and (b) a white light inferometry 3D
Harish L (AM13D025) 16thApril, 2014 11 / 39
Mixed mode
Contents
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 12 / 39
Mixed mode
Mixed mode fracture
This type of failure is difficult to simulate from the conventionalapproaches or testing methods.
But in SNTT it can be easily simulated by varying pitch anglesof spiral notch.
Figure : Samples with out fatigue showing fracture along (a) the 45o spiral plane(GB2-1) and (b) the36o spiral plane GB4-7
Crack deviated from notch root and propagated along 45o spiralplane.
Harish L (AM13D025) 16thApril, 2014 13 / 39
Mixed mode
Mixed mode fracture
This type of failure is difficult to simulate from the conventionalapproaches or testing methods.
But in SNTT it can be easily simulated by varying pitch anglesof spiral notch.
Figure : Samples with out fatigue showing fracture along (a) the 45o spiral plane(GB2-1) and (b) the36o spiral plane GB4-7
Crack deviated from notch root and propagated along 45o spiralplane.
Harish L (AM13D025) 16thApril, 2014 13 / 39
Mixed mode
Mixed mode fracture
This type of failure is difficult to simulate from the conventionalapproaches or testing methods.
But in SNTT it can be easily simulated by varying pitch anglesof spiral notch.
Figure : Samples with out fatigue showing fracture along (a) the 45o spiral plane(GB2-1) and (b) the36o spiral plane GB4-7
Crack deviated from notch root and propagated along 45o spiralplane.
Harish L (AM13D025) 16thApril, 2014 13 / 39
Mixed mode
Mixed mode fracture
Figure : Fracture surface of mixed mode of samples to fatigue loading (a) and (b) optical image and(c) a white light interferometry 3D
Harish L (AM13D025) 16thApril, 2014 14 / 39
Finite element analysis of epoxy material
Contents
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 15 / 39
Finite element analysis of epoxy material
Finite element analysis
1/8th of the SNTT sample were used in modeling due rotationalsymmetry in ABAQUS
crack tip area(A1) was meshed with wedge element C3D15. restareas (A2,A3 ) was meshed with C3020R elements.
Harish L (AM13D025) 16thApril, 2014 16 / 39
Finite element analysis of epoxy material
Finite element analysis
1/8th of the SNTT sample were used in modeling due rotationalsymmetry in ABAQUS
crack tip area(A1) was meshed with wedge element C3D15. restareas (A2,A3 ) was meshed with C3020R elements.
Harish L (AM13D025) 16thApril, 2014 16 / 39
Finite element analysis of epoxy material
Figure : Displacement countours of epoxy SNTT sample GB3-1 (a) the cylindrical coordinatedefinition (b) radial displacement vector (c) axial displacement vector
Harish L (AM13D025) 16thApril, 2014 17 / 39
Finite element analysis of epoxy material
Figure : von Mises contour of epoxy SNTT sample GB3-1: (a) the deformed cylinder and (b) vonMises stress contour around the deformed spiral notch tip
The Stress concentration could be observed around spiral notch
The butter fly plastic zone was also captured with in the wedgemesh area.
Harish L (AM13D025) 16thApril, 2014 18 / 39
Finite element analysis of epoxy material
Figure : von Mises contour of epoxy SNTT sample GB3-1: (a) the deformed cylinder and (b) vonMises stress contour around the deformed spiral notch tip
The Stress concentration could be observed around spiral notch
The butter fly plastic zone was also captured with in the wedgemesh area.
Harish L (AM13D025) 16thApril, 2014 18 / 39
Testing and analysis of composite materials
Contents
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 19 / 39
Testing and analysis of composite materials
materials and samples
SNTT samples were obtained from composite plates fabricatedusing the vaccume assisted infusion technique.
Figure : (a) Vacuume assisted infusion process for composite fabrication and (b) a finished compositeplate
The infused plates were cured at 70oC for 8hrs
Harish L (AM13D025) 16thApril, 2014 20 / 39
Testing and analysis of composite materials
materials and samples
SNTT samples were obtained from composite plates fabricatedusing the vaccume assisted infusion technique.
Figure : (a) Vacuume assisted infusion process for composite fabrication and (b) a finished compositeplate
The infused plates were cured at 70oC for 8hrs
Harish L (AM13D025) 16thApril, 2014 20 / 39
Testing and analysis of composite materials
Depending on the relative orientations between the samples andthe fibers, three types of samples were fabricated
Figure : (a) The schematic showing the orientations of three types of SNTT samples; and picture of(b) typeA,(c)typeB and (d)typeC samples
Harish L (AM13D025) 16thApril, 2014 21 / 39
SNTT testing and fracture surface characterisation
Contents
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 22 / 39
SNTT testing and fracture surface characterisation
A-type samples
Figure : Infrared images obtained during the testing of an A-type sample (A-13). The images weretaken: (a) at the start of the testing, (b) at the crack initiation, (c) during the crack propagation, and(d) after the complete separation of the sample.
Bright spot was observed along the spiral notch during tesing
Crack propagated along the notch and large amount of surfaceenergy was released.
Harish L (AM13D025) 16thApril, 2014 23 / 39
SNTT testing and fracture surface characterisation
Loading curve
Figure : Typical loading curve A,B and C-type samples
linear elastic behaviour was observed until failure occured.
All A and C samples were completely separated into halves afterSNTT testing.
Due to fiber strengthening B samples were not separated andshowed consistent resistence.
Harish L (AM13D025) 16thApril, 2014 24 / 39
SNTT testing and fracture surface characterisation
Figure : Images showing: (a) a failed A-type sample (A-1) and (b) its fracture surface. Note: thelength unit of the ruler is inch.
Figure : SEM images of the fracture surface of a failed A-type sample (A-1) taken at: (a) lowmagnification and (b) high magnification.
Fracture occured along the spiral notch
Crack propagation direction was parallel to the fiber orientation.
Harish L (AM13D025) 16thApril, 2014 25 / 39
SNTT testing and fracture surface characterisation
The fiber surfaces were very smooth and interfacial debondingoccurs.
River lines were observed in the resin region which were evidenceof crack propagation through the matrix.
Fiber/resin interfacial debond and resin matrix cracking aredominant failure mechanisms
Harish L (AM13D025) 16thApril, 2014 26 / 39
SNTT testing and fracture surface characterisation
B-Type samples
Figure : IR images showing the loading of a B-type sample (B-12): (a) when a crack initiated and (b)further propagated.
The primary cracks in B type sample could not propagatethrough the center of the sample.
Cracks runnig parallel to the sample axis.
Harish L (AM13D025) 16thApril, 2014 27 / 39
SNTT testing and fracture surface characterisation
Figure : Pictures of a failed B-type sample (B-2) showing: (a) the front view, (b) the back view, and(c) the cross-section view. Note: the length unit of the ruler is inch.
Multiple delaminations occured internally and interfacial regionsseemed to be the most vulnerable in this sample geometry.
Harish L (AM13D025) 16thApril, 2014 28 / 39
SNTT testing and fracture surface characterisation
C-Type samples
Figure : IR images showing the loading of a C-type sample (C-10): (a) when a crack initiated and (b)further propagated.
Figure : Pictures of a failed C-type sample (C-2) showing: (a) the separated two halves and (b) thecurved fracture surface. Note: the length unit of the ruler is inch.
curvature was observed on the fracture surface but in A typesample are flat.
Harish L (AM13D025) 16thApril, 2014 29 / 39
SNTT testing and fracture surface characterisation
Effect of loading rates
Figure : Failure loads of composite SNTT samples
There is no significant difference in failure torques among thesame type of samples tested with range of loading rates.
Harish L (AM13D025) 16thApril, 2014 30 / 39
FEA of composite materials
Contents
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 31 / 39
FEA of composite materials
Figure : Composite materials in SNTT model with different fiber orientations: (a) a schematic ofcomposite fiber orientations, (b) A-type sample, (c) B-type sample, and (d) C-type sample.
Concentrated torque was applied in one side and x,y translationson the other end were fixed.
Displacement contours of all composite samples are similar tothose obtained from epoxy samples.
Harish L (AM13D025) 16thApril, 2014 32 / 39
FEA of composite materials
von Mises stress contours
Figure : von Mises stress contour of A, B and C-type samples with a scale deformed factor of 20: (a)sample A6, (b) sample B4, (c) sample C6, (d) sample A6 crack tip, (e) sample B4 crack tip, and (f)sample C6 crack tip (unit: Pa).
Harish L (AM13D025) 16thApril, 2014 33 / 39
FEA of composite materials
Figure : Energy replease rate of composite SNTT samples.
Time dependent effect was not significant in energy release rateof composite SNTT samples.
Harish L (AM13D025) 16thApril, 2014 34 / 39
Suggestions for future work
Contents
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 35 / 39
Suggestions for future work
Suggestions for future work
Extend the SNTT Method to investigate the fracture behaviourfor the brittle materials and composite plys
Harish L (AM13D025) 16thApril, 2014 36 / 39
References
Contents
1 Introduction
2 Spiral Notch Torsion Test
3 Mixed mode
4 Finite element analysis of epoxy material
5 Testing and analysis of composite materials
6 SNTT testing and fracture surface characterisation
7 FEA of composite materials
8 Suggestions for future work
9 References
Harish L (AM13D025) 16thApril, 2014 37 / 39
References
References
1 Araki W, Nemoto K, Adachi T, Yamaji A. Fracture toughness for
mixed Mode of epoxy resin. Acta Mater 2005;53:86975.2 Selby K, Miller LE. Fracture toughness and mechanical behaviour of
an epoxy resin. J Mater Sci 1975;10:1224.3 Plangsangmas L, Mecholsky JJ, Brennan AB. Determination of
fracture toughness of epoxy using fractography. J Appl Polym Sci
1999;72:25768.4 Wang JA, Liu KC, McCabe DE, David SA. Using torsional bar testing
to determine fracture toughness. Engng Mater Struct 2000;23:4556.5 Ting Tan , Fei Ren , John JyAn Wang , Edgar Lara Curzio ,
Pancasatya Agastra, John Mandell, Williams D. Bertelsen , Carl M.
LaFrance Investigating fracture behavior of polymer and polymeric
composite materials using spiral notch torsion test,Volume
101,March 2013, Pages 109-128.
Harish L (AM13D025) 16thApril, 2014 38 / 39
Thank You
Harish L (AM13D025) 16thApril, 2014 39 / 39