04_composites

Evaluating the Realistic Behavior of Laminated Composites

Copyright 2007 Dassault Systèmes

2

Industry trends • Composites usage is increasing in all industries • Aerospace • Boeing 787 – first large jet with a majority of composites by weight • Airbus 350WX - over 60% of airframe made of new materials • UAVs – primarily composite construction • Automotive • F1 race teams – composite shells • Toyota's Tundra pickup has a composite box • Nissan Concept uses carbon-fiber components • Civil • Composite-wrapped bridge structures • Dentistry • Fiber-reinforced composite dental bridges! Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

3

Industry needs • Current simulation methodology is not up to the task • Verification of composites relies on testing • Expensive, time consuming • Current methodology has not evolved since the 1980s • Typical simulation uses linear methods to estimate first failure • Current composites interfaces are not up to the task • It is very time consuming to define composites and post-process composites in today's CAE tools • Some CAD/CAE/PLM packages do not support progressive failure, delamination, or material damage • With linear methods, design margins for composite parts today are often too high – the part is too expensive and heavy as a result • This reduces the value of the use of composites and blunts the cost advantages that composites can provide to a product Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

4

Abaqus Composites Solution Our solution allows customers to: • Perform advanced composites simulations including static and dynamic analysis that includes linear, nonlinear, and damage / fracture / failure within a single environment • Predict the stiffness, first-failure, strength, and post-failure behavior at the component and full-vehicle structural scale of complex composite products • Simulate low- (from tool drop or hail), medium- (from runway debris), or high-velocity (ballistic penetration) events including Barely Visible Impact Damage (BVID) and Bird Strike • Have the very best in composite modeling, visualization, and postprocessing through Abaqus/CAE's new ply-based interfaces As a complete product for composites modeling & simulation, Abaqus has no peer. Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

5

Composites Technology and Features • Features • Ease-of-use and efficiency features • NEW interface for pre-processing • NEW post-processing options • NEW Interface to CATIA CPD • Technology • Abaqus can solve a variety of problems • Ballistic impact on unidirectional composite • Barely Visible Impact Damage (BVID) • Woven fabric composite beam crush • Composite plate post-buckling behavior • Skin-stringer debonding using VCCT • Delamination using cohesive elements • Draping simulation Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

6

NEW Interface for Definition of Composites • New forms… new graphics… new visualization

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

7

Modeling Composite Structures • In reality, composite structures are built by laying-up fabrics on top of each other in patterns to create the part

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

8

Modeling Composite Structures • In reality, composite structures are built by laying-up fabrics on top of each other in patterns to create the part • In the FEA world, users have to define various sections to represent the different regions of the composite • Time consuming and difficult for complicated components

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

9

Modeling Composite Structures • In reality, composite structures are built by laying-up fabrics on top of each other in patterns to create the part • In the FEA world, users have to define various sections to represent the different regions of the composite • Time consuming and difficult for complicated components • This also results in post-processing difficulties • Element layers and section points to not directly correspond to a consistent piece of material

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

10

In V6.7, Uses Can Now Model in Terms of Plies • Think in terms of “plies” • Representation of the materials as placed in a mold • User supplied ply name is available in ODB and Abaqus/Viewer for easy tracking in post-processing operations • Plies defined on picked regions or named sets of partitioned geometry or orphan mesh parts Ply-1

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

Ply-2

Ply-3

11

Composites Modeling in V6.7 • Composite Layup Object • Part level replacement for multiple sections, section assignments and material orientations for layered composites - in one dialog box • Advantages: • Ply-based • More intuitive definition of ply regions than “artificial” section assignments • Output requests can be defined by composite layup • Suppressible • Supports shell, layered continuum shell and layered solid elements Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

12 Composite Lay-up Creation: > Create new ply layer and select region for that ply

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

13 Composite Lay-up Creation: > Select material for the ply

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

14 Composite Lay-up Creation: > Set thickness and ply angle

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

15 Composite Lay-up Creation: > Define second ply layer

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

16 Composite Lay-up Creation: > Define third ply layer

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

17

Composite Plies Manager Options • Ply management via right mouse menu • Copy plies • Move plies • Delete plies • Invert plies • Read from and write to file • Ply patterning • Create symmetric layup • Copy plies multiple times

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

18 Composite Query Shows Lay-up Thicknesses, Fiber Directions, and Element Reference Plane

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

19

Ply-based Post-processing • Ply-based results • Choose particular ply for results • Element layer numbering is handled automatically • Works with the existing section points functionality • Can show contours on top, middle, bottom, or top and bottom

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

20

Envelope Calculations • Show ply names

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

21

Envelope Calculations • Show quilt plot of critical plies

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

22

Thru-Thickness Plots

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

23

All Composites Features Are Open for Scripting Full scripting support

def firstFail(criterion=['AZZIT','MSTRN', 'MSTRS', 'TSAIH', 'TSAIW',], saveHardcopy=1): print "\n\nSTARTING..."

# Use the output database displayed in the current viewport vp = session.viewports[session.currentViewportName] odb = vp.displayedObject if type(odb) != visualization.OdbType: raise 'An odb must be displayed in the current viewport.' # Find the maximum failure crits bigList = [] bigDict = {}

...

for j in range(totalPlies):

try: region1=p.sets[areaDic.get(areaId[j])] #This fields = odb.steps['Step-1'].frames[-1].fieldOutputs assumes the set exists! except: t01 = time.time() print "SERROR: Set name " + areaDic.get(areaId[j]) # counter = 0 + " does not exist in the model :(" for field in fields.keys(): # O(len(keys)) sys.exit() compositeLayup.CompositePly(suppressed=FALSE, plyName=plyName[j], region=region1, material=matDic.get(matId[j]), thicknessType=SPECIFY_THICKNESS, thickness=float(thk[j]), orientationType=SPECIFY_ORIENT, orientationValue=0.0, numIntPoints=3)

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

24

NEW Draping Technology • Simulayt’s “Composites Modeler for Abaqus” can be purchased as a module of Abaqus/CAE • Calculates local fiber directions when tape/cloth is draped over curved geometry • Predicts flat pattern to ensure proposed plies can be manufactured • Allows legacy lay-ups to be imported

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

25

NEW Link Between CATIA CPD and Abaqus

• Lay-up definitions in CATIA CPD can be passed to Abaqus/CAE • If lay-ups are modified in Abaqus/CAE, updated definitions are passed back to CATIA CPD

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

26

Composites Technology and Features • Features • Ease-of-use and efficiency features • NEW interface for pre-processing • NEW post-processing options • Interface to CATIA CPD composites • Technology • Abaqus can solve a variety of problems • Ballistic impact on unidirectional composite • Barely Visible Impact Damage (BVID) • Woven fabric composite beam crush • Composite plate post-buckling behavior • Skin-stringer debonding using VCCT • Delamination using cohesive elements Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

27

Unidirectional Composite VUMAT • Ballistic impact is a concern in many application areas, including road and runway debris, bird strike, and armor design • A unidirectional fiber composite damage and failure VUMAT for Abaqus/Explicit is available for high speed impact problems • Available in ABAQUS Answer 3123 • Elastic stress/strain relations are given by orthotropic damaged elasticity • Four damage variables are introduced, two associated with fiber tension and compression and two with matrix tension and compression • Damage modeling can be combined with cohesive elements to predict delamination

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

28

Unidirectional Composite VUMAT (cont’d) • This example shows ballistic impact onto unidirectional fiber composite plate

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

29

Barely Visible Impact Damage • Non-visible damage to composite structures is a significant concern in the aerospace industry • Issues such as maintenance tool drop, hail impact and other sources of damage must be dealt with as part of composite structure design • How much residual strength does a structure maintain when small flaws in the structure are present?

from McGowan, D.M., and Ambur, D.R., NASA TM-110303 Damage-Tolerance Characteristics of Composite Fuselage Sandwich Structures With Thick Facesheets

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

30

Barely Visible Impact Damage (cont’d) • ABAQUS/Explicit used to model low speed impact • Residual displacements used as initial condition in ABAQUS/Standard • Hashin damage model available in ABAQUS/Explicit

Crushing Force 200,000 Undamaged

180,000

Damaged

160,000

Load (lb)

140,000 120,000 100,000 80,000 60,000 40,000 20,000 0 0.00

0.02

0.04

0.06 Displacement (in)

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

0.08

0.10

0.12

31

Woven Fabric Composites VUMAT • Woven fabrics are used extensively in crashworthiness applications • Helicopter sub-floor systems make use of these materials • Automotive uses include steering column crash absorbers as well as front and rear crash boxes

from Kindervater, Christof The Crashworthiness of Composite Aerospace Structures, Workshop Crashworthiness of Composite Transportation Structures TRL, Crowthorne, 3rd October 2002

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

Steering column crash absorber

32

Woven Fabric Composites (cont’d) • Woven fabrics dissipate energy efficiently during crushing • Kinetic energy is converted into fracture energy, breaking fibers and crushing matrix material • This energy is absorbed by the vehicle structure rather than the pilot’s spine, or the driver’s sternum • Abaqus/Explicit can successfully model this behavior

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

33

Postbuckling Behavior of Composites • Buckling and postbuckling behavior of composite panels is an important design consideration in many industries • This example uses eigenvalue buckling and Riks analysis capabilities from Smith, F.A. and Hopkins, P.M., Boeing Rotorcraft, Philadelphia, PA, Non-linear Internal Loads Modeling Methods, ABAQUS User’s Conference 2006, Boston, MA

Post-buckled stiffness Buckling load

Pre-buckled stiffness

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

34

Postbuckling Behavior of Composites (cont’d) • The composite lay-up has a significant effect on the panel buckling behavior

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

35

Debonding Using VCCT • Boeing selected SIMULIA to commercialize their proprietary implementation of the Virtual Crack Closure Technique (VCCT) • SIMULIA has productized Boeing’s technology for commercial usage based on the existing debonding functionality (2D and extended for 3D) • Apply linear elastic fracture mechanics to bondlines and interfaces •2D and 3D delaminations •Propagation •Mode separation

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

•Multiple cracks •Non-linear behavior (e.g., postbuckling) •Composite structure

36

Debonding Using VCCT • VCCT for Abaqus • Runs during an Abaqus analysis • Utilizes the existing “debond” contact architecture in Abaqus/Standard, suitably extended • Does not utilize overlapped user elements as the basis for the implementation • Does not require matched meshes across bonded surfaces • Includes post-failure ramp-down of crack tip force • Includes post-failure penetration prevention • Includes post-processing capabilities within Abaqus/Viewer • Includes analysis stabilization algorithms to help stabilize running cracks in Abaqus/Standard • Is compatible with existing Abaqus elements and material, incrementation and convergence controls, and stress-based procedures Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

37

Debonding Using VCCT (Skin-Stringer Example)

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

38

Delamination with Cohesive Elements

GT C

 Typical traction-separation response 7

Shear mode

6 5

GTC

• Delamination applications • Traction separation law • Typically characterized by peak strength (N) and fracture energy (GTC) • Mode dependent • Linear elasticity with damage • Available in both Abaqus /Standard and /Explicit • Modeling of damage under the general framework used for other material models in Abaqus • Damage initiation • Traction or separationbased criterion • Damage evolution • Removal of elements

T N

Normal mode

4 3 2 1 0 0

0.2

0.4

0.6

0.8

1

Mode Mix

Dependence of fracture toughness on mode mix Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

39

Delamination with Cohesive Elements (cont’d) • Cohesive elements have the benefit of not requiring the specification of crack initiation within the structure • Therefore, initiation of delamination can be modeled • An example is given here of a skin/stiffener debonding. The example is available as Problem 1.4.5 in the Abaqus Example Problems manual • Results of interest include stress concentrations at stiffener terminations, residual thermal strains at the interface, effects of residual strains on debonding, and how delamination propagates

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

40

Delamination with Cohesive Elements (cont’d) • Angle beam with three layers connected with adhesive

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

41

Summary The Abaqus Composites Solution allows customers to: • Perform advanced composites simulations including static and dynamic analysis that includes linear, nonlinear, and damage / fracture /failure within a single environment • Predict the stiffness, first-failure, strength, and post-failure behavior at the component and full-vehicle structural scale of complex composite products • Simulate low- (from tool drop or hail), medium- (from runway debris), or high-velocity (ballistic penetration) events including Barely Visible Impact Damage (BVID) and Bird Strike • Have the very best in composite modeling, visualization, and postprocessing through Abaqus/CAE's new ply-based interfaces As a complete product for composites modeling & simulation, Abaqus has no peer. Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

Case Study

Copyright 2007 Dassault Systèmes

43

Example (Payload Fairing) • “The payload fairing is the equipment used to protect the spacecraft and the upper stage during the early portion of the boost phase when the aerodynamic forces from the atmosphere could affect the rocket,” NASA.com. • The image here shows the payload fairing for the NASA Mars Exploration Rover mission

Image courtesy of NASA Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

44

Example (Payload Fairing) • Composite Aeroshell Model (built in CAE v6.7PR4) • Aluminum ribs / stiffeners shown in purple • Composite sections showing local reinforcement regions around access doors

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

45

Example (Payload Fairing)

New Composite Layup GUI

Side-doubler region

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

46

Example (Payload Fairing)

Query on panel shows composite layup, thicknesses, and orientations in /Viewer

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

47

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

48

Example (Payload Fairing) • Pressure load = 20 x (cos2psi under side only

Note: strain discontinuities in doubler region

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

49

Example (Payload Fairing) • Ply-based post-processing in /Viewer

Ply : CLOTH-1

Ply : CLOTH-3

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

50

Example (Payload Fairing) Max Principal Envelope Contour

Max Principal Envelope Ply ID where MAX occurs

Envelope plots to view which layer has the peak strain

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

51

Example (Payload Fairing) • Composites supported in both Abaqus/Standard and /Explicit Abaqus/Standard (20 psi)

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

Abaqus/Explicit (20 psi)

52

Example (Payload Fairing) • Composites supported in both Abaqus/Standard and /Explicit Abaqus/Standard (20 psi)

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes

Abaqus/Explicit (20 psi)

53

Example (Payload Fairing) • Analysis in Abaqus/Explicit carried out to collapse of structure Applied Load = 50 psi over 1.0 second

P = 42.5 psi (t = 0.85)

Nose Tip Displacement

Realistic Simulation of Composites Copyright 2007 Dassault Systèmes