fast generation of allowablemscsoftware.co.kr/upfile/conference_pdf/multi-scale modeling of...
TRANSCRIPT
Fast Generation of Allowable for CFRPAnthony CHERUET / e-Xstream Engineering
3
Overview
2
Virtual Allowable with Digimat VA
1 Digimat Technology
Challenges with Composites
4
3
From Coupon to Components
4
e-Xstream engineering
• The company• Founded in 2003
• Acquired by MSC Software in Sep 2012
• The Business: • 100% focused on material modeling
• A team of 50 people • 65% PhDs
• 25% MS & BS Engineering
• 10% Marketing, Finance & Admin
4
Louvain-la-Neuve
Bascharage
Munich
Belgium
Luxembourg
Germany
U.S.
E-Xstream Engineering
• More than 300 hundreds customers in the world: aerospace, automotive, materials suppliers and academics.
5
6
Digimat to simulate Multiple Types of Multi-Phase material with one Single Tool
• Digimat, Unique Solution for Multi-Materials
Short Fiber Reinforced Plastics Long Fiber ThermoplasticsWoven & Braided Composites
Hybrid Composites
Carbon Nanotubes
Mucell
Unidirectional fiber
sandwich panel
DFC
7
Multi-Scale Modeling Technology
• Prediction of Non-Linear Anisotropic Macroscopic behavior from constituents properties and microstructure
Semi-Analytical method
Mean-Field homogenization
• Mori-Tanaka
• Fast model preparation/solution
• Easy coupling with FE solver
RVE Direct Analysis method
Full-Field homogenization
• Build the accurate RVE geometry
• Compute it by FEM directly
8
Digimat, the multi-scale material modeling platform
Tools= knowledge transfer
Solutions• Workflow oriented• Integrated environments
eXpertise• Knowledge transfer
9
Overview
2
Virtual Allowable with Digimat VA
1 Digimat Technology
Challenges with Composites
4
3
From Coupon to Components
10
• The introduction Composites Materials required to re-scale completely the procedure of material testing
Insertion of Composites material relies on a Building Block Approach for Certification (by testing)
• First step of material characterization is done at the coupon level
• Required a very large experimental test matrix
• 1 to 2 years of testing
• cost in M$
• In 1980: Choices were limited
between few materials, mainly
Aluminum
• In 2000 : Introduction of
Composites materials has
enlarged the choice between
materials, combination of ply
stacking.
• The concern has also changed:
focus more on the damage
tolerance, effect of environment…
11
• TODAY: Generation of Allowable done by physical tests during long and costly campaign
• Need to cover different configurations
• Coupon type (UN, OH, FH, Bearing)
• Layup
• Environment conditions: RTD, ETW
• Need a lot of replicate to extract a statistical evaluation of the material properties (e.g. B-basis) accounting several sources of variability:
• Material Properties
• Process
• Experimental
Insertion of Composites material relies on a Building Block Approach for Certification (by testing)
12
• Substantial Time Savings
• High Quality Data Early in the Design Cycle
• Substantial Cost Savings
• Expansion of the Design Space
Why Not Use Virtual Testing?
Digimat VA is a Virtual Testing Solution for Laminate Allowable Computation
Productive Tools to Define, Solve and Post Process a complete test matrix for specific Standard Tests
Benefits
13
• At the opposite of metallic material which exhibit non-linear yielding, the only reliable and observable event in a CFRP test is the final failure
• Failure stress or strain are seen as the allowable of the composite, determined for a standard condition
Need 1: Progressive Failure Modeling to compute Allowable of CFRP
• Different failure modes appear depending on the angle between reinforcement and loading direction
• Fiber Breaking in longitudinal plies• Matrix Cracking in transverse plies
s
e
erupture
srupture
•Need for a Progressive Failure Modeling to simulate properly up to the final rupture of laminated structure
14
• Variability of the properties is also more important for composites than for metallic materials
Variability of Composite Materials
• Allowable:• A material property value that is statistically derived from test data coming from a stable process• Value that will be used for the design but that must be of confidence b-basis value
Materials (Constituents) Variability
Process Variability
Post-Process Variability
•Need for the definition of a test matrix allowing to capture the variability expected during manufacturing coming from several sources
15
Overview
2
Virtual Allowable with Digimat VA
1 Digimat Technology
Challenges with Composites
4
3
From Coupon to Components
16
Digimat VA is a vertical solution to efficiently set up and compute virtual allowables
1. Material
Calibration
2. Lay-up definition
3. Tests Geometry 5. Mesh Settings
6. Allowable
Computation
4. Variability
7. Statistical
Results
17
• Mean-field homogenization in a RVE to calibrate anisotropic stiffness of the ply
• Specific capabilities for UD and 2D woven (Basic and Advanced description of the weave pattern)
Progressive Failure Modeling in Digimat
Constituent materials Microstructure Anistropic properties of
the plyFiber
(transversly isotropic)
Resin (TD or TP)
Fibers
Volume fraction
Phases Properties were calibrated Volume Fraction is assumed to match the stiffness (for UD and woven)
Yarn
Weaving Pattern
18
• Definition of anisotropic damage evolution law at the ply level
Progressive Failure Modeling in Digimat
)1(
100
0)][1(
1
0)1(
1
12
222211
12
11
12
11
s
m
f
dG
EdE
EEd
S
Fiber Failure Matrix Failure
Hashin 2D criteria is used for UD
Multi-Components 2D is used for woven
19
• Digimat-VA creates multiscale material models based on composite datasheet
Digimat Material Definition
Based on NCAMP datasheet template, Digimat VA performs automatically a material calibration, builda micro-mechanical model and adds the Progressiv
e Failure Behavior of the Ply
Input Data per NCAMP format
Import Exp. Data
Constituent Properties Calibration
20
Definition of the test matrix
Definition of the Layup• Can be Hybrid Layup
Definition of Parameterized tests (ASTM)(UNT, UNC, OHT, OHC, FHT, FHC (protusion and countersunk)
21
Definition of the test matrix
Definition of the Mesh Settings and pre-vizualisation
22
Digimat-VA turns a test matrix into FEA runsto obtain virtual allowables
Raw stress-strain
B-basis com
putation
Coupon simulation
• Embedded FEA solver
• Digimat Progressive Failure
• Micro-level variability
Test matrix definition
• Parameterized
Standard Tests
Virtual allowables
• Mean, B-basis, A-basis
• Root-cause analysis
23
Progressive failure predicts a realistic strengthin a straightforward way
Matrix Failure located in 90 plies (D22)
[45/0/-45/90]2s
[45/0/-45/90]2s
Fiber Failure located in 0 plies (D11)
Reference Value = 47.6 ksi
Composites strength will be the maximum of the curve
Visualization of the Failure Pattern
• Example on OHT with quasi-isotropic layup of AS4/8552 (NIAR Report)
24
A Digimat Progressive Failure model is valid acrossdifferent layups and coupon types
Material: Hexcel 8552 / IM7
25
Validation case using Plain Weave AS4/8552
• NIAR provided experimental results to validate the implementation of the wovenreinforcement within Digimat
26
• New filled hole test
• Bolt/countersunk fastener
• Tension & compression tests
• Smart analysis stop beyond load drop
• AS4/8552 UD validation based on NCAMP data
Digimat-VA opens up to filled hole test
27
Overview
2
Virtual Allowable with Digimat VA
1 Digimat Technology
Challenges with Composites
3
B-basis generation
4 From Coupon to Components
28
• Thanks to microscopic description of the composite, variability can be introduced at several levels
Introduction of Variability for Statistical Analyses
29
• Insertion of Material (Constituent) variability
Computation of the Stiffness and Strength Ply properties with variability
Method 1: Coefficient of variability can be introduced directly based on the in
-house experience or provided by Materials Suppliers
Method 2: Build a methodology to reverse engineer the variability of the Fiber
and Resin knowing the variability observed experimentally at the lamina level
1. Determine constituents variabilities to converge towards the
experimental lamina b-basis
2. Re-use this variability when the lamina is used in a laminate
A complete case study has been realized based on the UD AS4/8552 Statistical
Analysis Report provided by the NIAR (NCAMP databasis) – Methodology
presented at NAFEMS, CAM-X, SAE, webinar.
30
• Using this methodology, we identify the variability of the fiber and the resin that allow to reproduce correctly the variability at the lamina level
• With Digimat VA, we simulate 4 standard tests on a single ply, respecting the test matrix (nb batches * nb panels * nb coupons)
Prediction of b-basis at the lamina level
The prediction of the b-basis are correct too
31
• Tests are then run with the calibrated material model including the variability and the default settings of Digimat VA
• Mean values are predicted within 10%, except for OHT3, OHC2 and UNC2
Running the test matrix accounting variability
Layup: 0/45/90• Layup 1: 25/50/25
• Layup 2: 10/80/10
• Layup 3: 50/40/10
Experimental Ply Variability
Identify Fiber/Resin Variability
Verify Ply Variability
Apply Fiber/Resin variability for Laminate
Allowable
32
Effect of Defects due to Manufacturing in Digimat VA
• Need for new methodologies enabling to take into account micro or macro-scopic effect of defect coming from the manufacturing
• Methodologies that mix Material Engineering and Allowable Computation
• Effect of %, size distribution of Porosity on
mechanical stiffness and strength of Lamina
― Combination of Digimat VA micro-mechanics
material model and FE modeling of RVE
using Digimat FE
• Effect of Presence of Gaps on the
Laminate Strength
– Introduction of resin rich area
– Mapping of defect
33
Overview
2
Virtual Allowable with Digimat VA
1 Digimat Technology
Challenges with Composites
4
3
From Coupon to Components
34
Digimat Technology is available at each step of the Design Process
Material Engineering using Digimat FE & MF
Calibrations using Digimat-MF
e
Allowable Generation Design and Stress AnalysesMaterial Engineering
35
Prediction of Failure Mode/Loads of a Hybrid Laminate in Pin-loaded joint configuration
Material: Graphite/Epoxy (UNS12) UDGraphite/Epoxy (DMS2288) Wovens
Stacking:[( 45)3/90/( 45)2/04/90/04/( 45)2/90/[( 45)3]
36
Prediction of Failure Mode/Loads of a Hybrid Laminate in Pin-loaded joint configuration
Net Tension
Shear Out
Bearing
37
Conclusion
• Digimat-VA sets a first milestone for a Virtual Testing Solution
dedicated to the productive generation of virtual allowables
including variability
– Validated cases exist for UD and 2D woven
– Bearing will be the next test integrated
• Material Model can be used at the component level through coupled
analysis with any FEM solver
• Virtual Testing and Material Engineering must be used to speed-up
material development and to complement the test process
– Test Smarter: Save time and reduce test matrix
– Investigate design space: non-standard laminate, effect of defects