Presentation on theme: "David Mollenhauer, Logan Ward Air Force Research Laboratory, USA"— Presentation transcript:
1 Simulation of Discrete Damage in Composite Overheight Compact Tension Specimens David Mollenhauer, Logan WardAir Force Research Laboratory, USAEndel Iarve, Sirina Putthanarat, Kevin HoosUniversity of Dayton Research Institute, USAStephen Hallett, Xiangqian LiUniversity of Bristol, United KingdomCompTest 2011Lausanne, Switzerland14-16 February 2011
4 Background Goal: Numerical Modeling Basis Discrete Modeling of Matrix Cracking and Delamination NetworksMatrix Cracking & DelaminationInteraction ofGeneral approach based on X-FEM ideasMoes, et. al., 1999, IJNMEMust accommodate cracking & delamination interaction Van der Meer F P and Sluys L J, (2nd ECCOMAS, 2009) Qingda Yang and Brian Cox, (CompTest, 2008) Iarve (AIAA 1998), Iarve (IJNM, 2003), Iarve et al. (Composites A, 2005; IJMS, 2007) …..
5 Background Numerical Modeling Basis Mesh Independent Crack (MIC) Modeling- A Regularization of X-FEMCrack is modeled by adding degrees of freedom (element enrichment)Regularization means that the crack face step function is approximated by FEMH=0H=1H(x) is Heaviside step functionWith a jump over the crack surfaceH(x) is approximated by the sameshape functions as displacementsIarve (IJNM 2003)
6 Background Numerical Modeling Basis MIC & Delamination Interaction and PropagationThe original Gauss integration schema is preserved for any crack orientationAdjacent plies tied through node/and or surface element integration contactPropagation is through cohesive zone method
7 Numerical Modeling Basis BackgroundNumerical Modeling BasisGeneral Modeling FlowStep i=0 is thermal pre-stressAdd axial displacement incrementPerform Newton-Raphson iterations to converge damage variables in delam and MIC cohesive lawsCheck matrix failure criteriaAdd damage and repeat 2-5Matrix Failure Criteria - Dávila, Camanho, and Rose, “Failure criteria for FRP laminates,” J. of Composite Materials, VolCohesive 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, 2006.Mesh Independent Cracks - Iarve, “Mesh independent modeling of cracks by using higher order shape functions,” Int. J. Num. Meth. Eng., Vol.56, 2003.
8 Previous Experimental Effort BackgroundPrevious Experimental EffortOverheight 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 pliesDisplacement-load, 2D X-ray, & c-scan measurements
9 Numerical Model Details Table 1. Properties for IM7/8552 Lamina In-house code BSAM (B-spline analysis method) usedGeometry matched to Bristol’s test specimensBlocked Ply Specimens (IM7/8552)[452/902/-452/02] s[04/904] 2sDispersed Ply Specimen (IM7/8552)[45/90/-45/0] 2sTable 1. Properties for IM7/8552 LaminaMaterial PropertyValueE11 (GPa) Ref 1161.0E22,E33 (GPa) Ref 111.38G12,G13 (GPa) Ref 15.17G23 (GPa) Ref 13.98n12, n13 Ref 10.32n23 Ref 10.44a1 (1/◦C)0.00a2 (1/◦C)3.00e-05GIC (N/mm) Ref 10.2GIIC (N/mm) Ref 11.0YT (MPa)60.0YC (MPa)275.0S (MPa)90.0 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.
13 POD vs Load ComparisonBlocked Quasi[452/902/-452/02] s Specimen
14 Matrix Damage Evolution Blocked Quasi[452/902/-452/02] s Specimen
15 Matrix Damage Blocked Cross-Ply Simulations are symmetric in-plane as well as out-of-plane to aid damage stability.
16 Matrix Damage Evolution Blocked Cross Ply[04/904] 2s SpecimenMovie has been mirrored about symmetry plane
17 Blocked Quasi – with Statistical Variation Matrix DamageBlocked Quasi – with Statistical VariationFive different statistical variations of matrix strengths were simulated.Case 0Case 1Case 2Case 3Case 4
18 POD vs Load Comparison Blocked Quasi – with Statistical Variation
19 POD vs Load Comparison Blocked Quasi – with Statistical Variation
20 Continuum Damage Model for Fiber Failure – characteristic length of the FEIM7/8552XTGXTfXTfGT3136 N/mm281.5 n/mm0.20.4C=(1-d)C0C0 – initial stiffnessd – damage variableFor 1 mm3 volumeP. 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)
21 simulation damage pattern Matrix & Fiber DamageDispersed Quasi[45/90/-45/0] 2s Specimenexperimental X-raysimulation damage patternContinuum damage mechanics routine used for fiber damage courtesy of Carlos Davila of NASA LaRC
22 Matrix & Fiber Damage Dispersed Quasi [45/90/-45/0/45/90/-45/0] s Image from Test Specimen #3
23 Matrix & Fiber Damage Dispersed Quasi [45/90/-45/0/45/90/-45/0] s Image from Test Specimen #3
24 Matrix & Fiber Damage Dispersed Quasi [45/90/-45/0/45/90/-45/0] s Image from Test Specimen #3
25 Matrix & Fiber Damage Dispersed Quasi [45/90/-45/0/45/90/-45/0] s Image from Test Specimen #3
26 Matrix & Fiber Damage Dispersed Quasi [45/90/-45/0/45/90/-45/0] s Image from Test Specimen #3
27 Matrix & Fiber Damage Dispersed Quasi [45/90/-45/0/45/90/-45/0] s Image from Test Specimen #3
28 Matrix & Fiber Damage Dispersed Quasi [45/90/-45/0/45/90/-45/0] s Image from Test Specimen #3
29 Conclusions & Future Concusions: Future Efforts: Simulated load-displacement behavior correlates well with actual specimen behaviorSimulated discrete damage patterns correlate extremely well with X-ray CT imagesAt similar applied load levelsPredicted complex specimen behavior obtained using only lamina-level, measurable properties and application of “simple” descriptions of damage.Future Efforts:Validate current fiber failure methodologyImplement alternative fiber failure methodology
30 AcknowledgementsPartial 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
35 X-Ray Computed Tomography Specimens sectioned to increase magnificationDamage enhanced with zinc iodide solutionCracks appear as discrete white linesDelaminations appear as lightening of backgroundDelamination front is brighter
36 X-Ray Computed Tomography A “voxel averages the X-ray density across its volumeSome will span ply interfacesBeam hardening effects further smear resultsdelamPly Thickness mmVoxel Dimension 0.06 mmcrackvoxel
37 Original Results from Li et al Experimental ResultsLoad Displacement Results from the [452/902/-452/02] s SpecimenData shifted to extrapolate linear portion to zeroCoarse X-ray CT results at POD = 1.74, 2.12, & 2.26 mmDetailed X-ray CT results at POD = 1.74 mm & 2.26 mmOriginal Results from Li et alShifted Results