SECTION 3 Progressive Ply Failure and Delamination Modeling

Transcription

1 SECTION 3 Progressive Ply Failure and Delamination Modeling Composites Technology Day, January February 2012 S3-1

2 Composites Failure Modeling Look at types of problems you can solve today with MSC s composite failure technology Examples demonstrating how to apply this technology and how it works Composites Technology Day, January 2012 S3-2

3 Composite Fuselage Example Composite aircraft fuselage Light weight composite components Constructed from layered composite material Bonded and/or fastened together S3-3

4 A Closer Look Simulate delamination? Stringers Skin Frame Shear clips S3-4

5 Composites Damage and Manufacturing Defect Examples S3-5

6 Composites Failure Examples S3-6

7 First-Ply-Failure Analysis First-Ply Failure (FPF) Linear analysis based on failure theory Compute failure index or strength ratio for the ply material Optimization of ply angle/thickness Critical Margin of Safety S3-7

8 Going Beyond FPF Evaluate the load redistribution in a composite structure as the plies fail progressively Simulate delamination growth from initial flaw Study crack propagation to design for fail-safe structures S3-8

9 Going Beyond FPF Ply Material Failure Delamination VCCT CZM 9 PFA Delamination Breaking Glue S3-9

10 FAQ: What Element types are supported? Composite failure modeling is supported in both shell and solid elements Shell element Solid element Solid Shell element Layered Composite definition S3-10

11 Composites Failure Modeling - PFA VCCT CZM 11 PFA Delamination S3-11 Breaking Glue

12 Progressive Failure Analysis (PFA) Also known as Progressive Ply Failure (PPF) Select a failure criterion Select a degradation option The composite is failed on a layer by layer basis Upon failure, the elastic properties are scaled down Pin bearing on hole S3-12

13 Composite Failure Criteria Composite Failure Most of the criteria are semi-empirical in nature Composite Failure on Layer Basis Maximum Stress Maximum Strain Hill Hoffman Tsai-Wu Hashin Puck Hashin-Tape Hashin-Fabric User defined (UFAIL) S3-13

14 PFA Options Progressive Composite Failure options Flagged through the MATF entry (ITYPE = 2 or 3) Up to three failure criteria can be selected Only the primary failure criterion is used for PFA The other two are only used to calculate failure indices The behavior up to the failure point is linear elastic Upon failure When failure index is larger than one, degrade material moduli Selective degradation if matrix fails, do not change fiber properties Stiffness drops gradually or immediately S3-14

15 MSC Nastran Input Data Format ITYPE: 0 No PFA; 2 Gradual Selective; 3 Immediate Selective Criterion: 1 Max. Stress; 2 Max. Strain; 3 Hill; 4 Hoffman; 5 Tsai-Wu; 7 Hashin; 8 Puck; 10 Hashin-Tape;11 Hashin- Fabric; 13 User Subroutine S3-15

16 PFA Example Fuselage Damage Rigid elliptical cylinder hitting composite shell 5-layered composite Puck criterion, gradual option Damage of outer ply S3-16

17 PFA Example Wing Damage S3-17

18 Micromechanical Failure model Traditional approach computes composites failure based on ply-level failure properties The Micromechanical approach gets down to the fiber and matrix level and looks at the failure mechanism at the constituent level MSC has partnered with Firehole to bring the Helius MCT micromechanical failure technology to our users S3-18

19 Composites Failure Modeling - VCCT VCCT CZM 19 PFA Delamination S3-19 Breaking Glue

20 VCCT In linear fracture mechanics, a crack starts to grow when Total G > G c G is the energy release rate G c is the fracture toughness The VCCT is one of the methods used to compute the energy release rate. S3-20

21 VCCT (Virtual Crack Closure Technique) FEM approximation: Use consistent nodal force at tip and crack opening at first crack segment Energy release rate: G = Fu/2a Growth method Release glued contact Grow along element edge Remeshing Marc Only S3-21

22 VCCT Supported in both Marc and MSC Nastran Supported crack types are shown below line crack 2D or shell face crack shell to shell face crack 3D solid line crack shell edge to solid or shell face crack shell to solid S3-22

23 Modes of Crack Extension All three modes of crack extension are supported Mode I: Opening Mode II: Sliding Mode III: Tearing S3-23

24 VCCT Example Release glued contact Skin-Stringer Delamination Wagner/Balzani, Computers & Structures 2008 Stringer glued to skin stringer initial crack front Initial delamination skin VCCT key ingredients: - Initial crack - Define crack front nodes fixed stringer S3-24 push skin downward

25 VCCT Example Release glued contact Animation shows glued region Animation shows region released from glued S3-25

26 VCCT Example Release glued contact Benchmark Problems DCB DCB DCB S3-26 SLB

27 VCCT Example Release glued contact 4-Ply Composite modeled with 2 layers of solid elements Defect between 3 rd and 4 th ply Embedded circular defect F Glue parts together, except at defect F Buckling Delamination S3-27

28 VCCT Example Release glued contact S3-28

29 VCCT Example Grow Along Element Edge Growth direction: maximum hoop stress criterion Initial crack clamped S3-29

30 VCCT Example Grow Along Element Edge Quad mesh Tria mesh Remesh S3-30

31 VCCT Example Crack Bifurcation New technology Crack tip automatically generated as the crack reaches the stiffener 8 layers 4 layers glued shell thickness with offsets elastic orthotropic material composite with four layers: [-45/90/0/45] S3-31

32 VCCT Example Crack Bifurcation Growth through composite skin with stiffeners S3-32

33 VCCT Example Crack Bifurcation Courtesy of Dr. Kim Parnell S3-33

34 Composites Failure Modeling - CZM VCCT CZM 34 PFA Delamination S3-34 Breaking Glue

35 Cohesive Zone Modeling (CZM) Cohesive Zone Modeling (CZM) is a technique used to simulate delamination growth. The implementation of CZM is based on: Library of special interface elements Material model to characterize the interface behavior Interface Element S3-35

36 Cohesive Zone Modeling (CZM) The constitutive behavior of these elements is expressed in terms of tractions versus relative displacements between the top and bottom edge/surface of the elements Top and bottom faces may coincide V is the effective opening displacement S3-36

37 Cohesive Zone Modeling (CZM) Material models Bilinear Exponential Linear-exponential Material behavior Initially reversible Irreversible if v > v c top face 4 7 n t top and bottom face may coincide (zero thickness) 6 2 s 3 bottom face S3-37

38 CZM Example Lap-Shear Joint: Plates Adhesive Region Reference: M.N. Cavalli, M.D. Thouless and Q.D. Yang, Cohesive-Zone Modeling of the Deformation and Fracture of Weld-Bonded Joints; Welding Journal Vol. 83, no. 4, 2004 S3-38

39 CZM Example Finite element model: Mesh plates and adhesive layer independently using higher order elements Utilize the contact option to glue the adhesive layer to the plates S3-39

40 CZM Example S3-40

41 Composites Failure Modeling Breaking Glue Contact VCCT CZM 41 PFA Delamination S3-41 Breaking Glue

42 Breaking Glued Contact Release glued contact when the following stress criterion is met User specified Use contact normal and tangential stresses User specified After break, do regular contact with friction and separation S3-42

43 Example - Breaking glued contact Coating debonding Load with rigid body S3-43

44 Example - Breaking glued contact Coating debonding Load with rigid body S3-44

45 Composites Failure Modeling Delamination (Marc only) VCCT CZM 45 Breaking Glue PFA Delamination S3-45

46 Delamination Split up mesh between materials or within a material when the following stress criterion is met Use stresses normal and tangential to interface S3-46

47 Delamination Examples S3-47

48 Delamination with CZM Option to insert interface element where mesh is split Fully automatic S3-48

49 Delamination Example: Plate impact Composite plate, 8 layers, [0/45/- 45/90] s Stacked solid shell elements One element per layer No double nodes Clamped edges, prescribed downward motion of circular region in the center S3-49

50 Delamination Example: Plate impact View quarter model Outline plot Delamination between layers (mesh splitting) Contact occurs between layers S3-50

51 Delamination Example: Plate impact Automatic insertion of interface elements Self contact not needed Show only interface elements S3-51

52 Summary Progressive Failure Analysis (PFA) Virtual Crack Closure Technique (VCCT) Fracture mechanics Cohesive Zone Model (CZM) Interface elements Breaking glued contact Stress Criterion 52 Delamination Stress Criterion S3-52

53 End of Section 3 S3-53