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David Mollenhauer, Logan Ward Air Force Research Laboratory, USA Endel Iarve, Sirina Putthanarat, Kevin Hoos University of Dayton Research Institute, USA.

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Presentation on theme: "David Mollenhauer, Logan Ward Air Force Research Laboratory, USA Endel Iarve, Sirina Putthanarat, Kevin Hoos University of Dayton Research Institute, USA."— Presentation transcript:

1 David Mollenhauer, Logan Ward Air Force Research Laboratory, USA Endel Iarve, Sirina Putthanarat, Kevin Hoos University of Dayton Research Institute, USA Stephen Hallett, Xiangqian Li University of Bristol, United Kingdom C omp T est 2011 Lausanne, Switzerland February 2011 Simulation of Discrete Damage in Composite Overheight Compact Tension Specimens

2 Outline Motivation Background Numerical Model Details Results Blocked quasi-isotropic & cross-ply Statistical strength effects Dispersed ply quasi-isotropic Conclusion & Future

3 Motivation X Y No damage Extensive Damage Normalized Axial Strain from [0/45/90/-45] s Composite

4 Background Numerical Modeling Basis Goal: Discrete Modeling of Matrix Cracking and Delamination Networks [1]Van der Meer F P and Sluys L J, (2 nd ECCOMAS, 2009) [2]Qingda Yang and Brian Cox, (CompTest, 2008) [3] Iarve (AIAA 1998), Iarve (IJNM, 2003), Iarve et al. (Composites A, 2005; IJMS, 2007) [4]….. General approach based on X-FEM ideas Moes, et. al., 1999, IJNME Must accommodate cracking & delamination interaction Interaction of Matrix Cracking & Delamination

5 Background Numerical Modeling Basis Crack is modeled by adding degrees of freedom (element enrichment) Regularization means that the crack face step function is approximated by FEM H(x) is approximated by the same shape functions as displacements H=0 H=1 Iarve (IJNM 2003) H(x) is Heaviside step function With a jump over the crack surface Mesh Independent Crack (MIC) Modeling - A Regularization of X-FEM

6 Background Numerical Modeling Basis The original Gauss integration schema is preserved for any crack orientation Adjacent plies tied through node/and or surface element integration contact Propagation is through cohesive zone method MIC & Delamination Interaction and Propagation

7 General Modeling Flow 1.Step i=0 is thermal pre-stress 2.Add axial displacement increment 3.Perform Newton-Raphson iterations to converge damage variables in delam and MIC cohesive laws 4.Check matrix failure criteria 5.Add damage and repeat 2-5 Matrix Failure Criteria - Dávila, Camanho, and Rose, “Failure criteria for FRP laminates,” J. of Composite Materials, Vol Cohesive Zone Propagation - Turon, Camanho, Costa, and Dávila, “A damage model for the simulation of delamination in advanced composites under variable-mode loading,” Mechanics of Materials, Vol.38, Mesh Independent Cracks - Iarve, “Mesh independent modeling of cracks by using higher order shape functions,” Int. J. Num. Meth. Eng., Vol.56, Background Numerical Modeling Basis

8 Background Previous Experimental Effort Overheight Compact Tension specimens tested at the University of Bristol in the UK (Li et al, Composites Part A 40, 2009) Multiple stacking sequences of both dispersed & blocked plies Displacement-load, 2D X-ray, & c-scan measurements

9 Numerical Model Details Table 1. Properties for IM7/8552 Lamina Material PropertyValue E 11 (GPa) Ref E 22,E 33 (GPa) Ref G 12,G 13 (GPa) Ref G 23 (GPa) Ref ,  13 Ref Ref  1 (1/ ◦ C) 0.00  2 (1/ ◦ C) 3.00e-05 G IC (N/mm) Ref G IIC (N/mm) Ref Y T (MPa) 60.0 Y C (MPa) S (MPa) 90.0 In-house code BSAM (B-spline analysis method) used Geometry matched to Bristol’s test specimens Blocked Ply Specimens (IM7/8552) [45 2 /90 2 /-45 2 /0 2 ] s [0 4 /90 4 ] 2s Dispersed Ply Specimen (IM7/8552) [45/90/-45/0] 2s [1] Hallett, S.R., Jiang, W.G., Khan, B., and Wisnom, M.R., “Modeling the interaction between matrix cracks and delamination damage in scaled quasi-isotropic specimens,” Compos Sci Technol, 68(1): pp.80-89, 2008.

10 Numerical Model Details X-ray Close-up

11 Shifted Results Specimen One Stacked X-Ray POD = 2.11 mm [45 2 /90 2 /-45 2 /0 2 ] s Specimen Matrix Damage Comparison Blocked Quasi

12 45 2 /90 2 Interface90 2 /-45 2 Interface-45 2 /0 2 Interface Specimen 1 POD ~ 2.12 mm Specimen 1 POD ~ 2.12 mm Specimen 1 POD ~ 2.12 mm POD ~ 2.11 mm Matrix Damage Comparison Blocked Quasi

13 [45 2 /90 2 /-45 2 /0 2 ] s Specimen POD vs Load Comparison Blocked Quasi

14 [45 2 /90 2 /-45 2 /0 2 ] s Specimen Matrix Damage Evolution Blocked Quasi

15 Simulations are symmetric in-plane as well as out-of-plane to aid damage stability. Matrix Damage Blocked Cross-Ply

16 [0 4 /90 4 ] 2s Specimen Movie has been mirrored about symmetry plane Matrix Damage Evolution Blocked Cross Ply

17 Matrix Damage Blocked Quasi – with Statistical Variation Case 0 Case 1 Case 2 Case 3 Case 4 Five different statistical variations of matrix strengths were simulated.

18 POD vs Load Comparison Blocked Quasi – with Statistical Variation

19

20 P. Maimi, P. P. Camanho, J. A. Mayugo, C. G. Davila, A continuum damage model for composite laminates: Part I constitutive model, Mechanics of Materials,39 (10) (2007) P. Maimi, P. P. Camanho, J. A. Mayugo, C. G. Davila, A continuum damage model for composite laminates: Part II computational implementation and validation, Mechanics of Materials 39 (10) (2007) C=(1-d)C 0 C 0 – initial stiffness d – damage variable For 1 mm 3 volume Continuum Damage Model for Fiber Failure IM7/8552 XTXT G XT f XT f GT 3136 N/mm n/mm – characteristic length of the FE

21 [45/90/-45/0] 2s Specimen Matrix & Fiber Damage Dispersed Quasi Continuum damage mechanics routine used for fiber damage courtesy of Carlos Davila of NASA LaRC simulation damage pattern experimental X-ray

22 [45/90/-45/0/45/90/-45/0] s Matrix & Fiber Damage Dispersed Quasi Image from Test Specimen #3

23 [45/90/-45/0/45/90/-45/0] s Matrix & Fiber Damage Dispersed Quasi Image from Test Specimen #3

24 [45/90/-45/0/45/90/-45/0] s Matrix & Fiber Damage Dispersed Quasi Image from Test Specimen #3

25 [45/90/-45/0/45/90/-45/0] s Matrix & Fiber Damage Dispersed Quasi Image from Test Specimen #3

26 [45/90/-45/0/45/90/-45/0] s Matrix & Fiber Damage Dispersed Quasi Image from Test Specimen #3

27 [45/90/-45/0/45/90/-45/0] s Matrix & Fiber Damage Dispersed Quasi Image from Test Specimen #3

28 [45/90/-45/0/45/90/-45/0] s Matrix & Fiber Damage Dispersed Quasi Image from Test Specimen #3

29 Conclusions & Future Concusions: Simulated load-displacement behavior correlates well with actual specimen behavior Simulated discrete damage patterns correlate extremely well with X-ray CT images At similar applied load levels Predicted complex specimen behavior obtained using only lamina-level, measurable properties and application of “simple” descriptions of damage. Future Efforts: Validate current fiber failure methodology Implement alternative fiber failure methodology

30 Acknowledgements Partial funding for this work from NASA AAD-2 (NNX08AB05A-G) and AFRL (FA D-5052) Many thanks to Dr Cheryl Rose and Dr Carlos Davila of NASA LaRC for collaboration and advice. The authors also wish to acknowledge their collaboration with Anoush Poursartip, Reza Vaziri, and Navid Zobeiry at the University of British Columbia in conducting the OCT experimental testing

31

32 imaging panel X-ray Top View imaging panel X-ray Side View Image i X-Ray Computed Tomography OCT Specimen 3D “voxel” data visualizing internal specimen structure

33 imaging panel X-ray Top View imaging panel X-ray Side View Image j X-Ray Computed Tomography OCT Specimen 3D “voxel” data visualizing internal specimen structure

34 imaging panel X-ray Top View imaging panel X-ray Side View Image k X-Ray Computed Tomography OCT Specimen 3D “voxel” data visualizing internal specimen structure

35 X-Ray Computed Tomography Specimens sectioned to increase magnification Damage enhanced with zinc iodide solution Cracks appear as discrete white lines Delaminations appear as lightening of background Delamination front is brighter

36 Ply Thickness mm Voxel Dimension 0.06 mm voxel crack delam X-Ray Computed Tomography A “voxel averages the X-ray density across its volume Some will span ply interfaces Beam hardening effects further smear results

37 Experimental Results Load Displacement Results from the [45 2 /90 2 /-45 2 /0 2 ] s Specimen Data shifted to extrapolate linear portion to zero Coarse X-ray CT results at POD = 1.74, 2.12, & 2.26 mm Detailed X-ray CT results at POD = 1.74 mm & 2.26 mm Original Results from Li et al Shifted Results

38 -45 2 /0 2 Interface Specimen 1 POD ~ 2.12 mm Blunt Notch POD ~ 2.11 mm Matrix Damage Comparison Blocked Quasi

39 45 2 /90 2 Interface Specimen 1 POD ~ 2.12 mm Blunt Notch POD ~ 2.11 mm Matrix Damage Comparison Blocked Quasi


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