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1 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Integrity Service Excellence
Uncertainty Driven Engineering for Heterogeneous
Media & Structures
SIAM Annual Meeting 09-13 July 2012
Dr. Timothy D. Breitzman Composite Materials Branch
Air Force Research Laboratory Wright-Patterson AFB OH
2 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Air Force Research Laboratory Materials & Manufacturing Directorate
3 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Outline
• Motivation • State-of-the-Art Checkup
– Integrated Computational Materials Science & Engineering (ICMSE)
• Discussion on Probabilistics & Uncertainty • Concluding Remarks
4 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
The Widespread Need
“Since the 1980s, technological change and economic progress have grown ever more dependent on new materials developments.” – White House Office of Science & Technology Policy;
Materials Genome Initiative for Global Competitiveness, 2011
Materials can enable new performance, missions and platforms
Zero-CTE laminates >> dimensional stability Directional conductivity >> thermal management
…and the limitations of materials can translate into limitations of a platform
Melting/softening point >> use temperature & mission envelope Specific properties >> weight margins
5 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Representative Technology Selection Criteria
Initial R&D Lab Scale
Performance Evaluation Production Scale-Up
Design Properties
Testing
Examples of Why Tech Was Dropped: •Concept Not Valid •Deficiency Found •Not Amenable to Scale-Up •Program Need Goes Away •Niche Material •Missed Implementation Timing •High Cost
Technology Succeeds: •Valid Concept •Scale-Up Success •Funding Available •Real Problem Exists •Customer Acceptance •ROI Acceptable
Production & Implementation
6 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Why is Material Development the Rate-Limiting Step?
“Modern computational engineering tools generally have radically reduced the time required to optimize new products. However, analogous computational tools do not exist for materials engineering.” – National Materials Advisory Board;
Integrated Computational Materials Engineering, 2008
7 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Time from Material Invention to Widespread Use
Materials Technology Invention Widespread Commercialization
Vulcanized Rubber 1839 Late 1850s Low-Cost Aluminum 1886 Early 1900s Teflon 1938 Early 1960s Titanium (Structural Uses) Mid 1940s Early 1960s Velcro Early 1950s Early 1970s Polycarbonate (Bullet Proof Glass) 1953 Early 1970s Lithium Ion Battery Mid 1970s Late 1990s AFR-PE-4 High Temp Composite Early 1990s Early 2010s
Little improvement in the last 175 years!
8 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
State of the Art Checkup
• DoD structures certification – Building block approach – Certification by analysis – Lots of supporting tests
• Risk reduction (uncertainty)
•Risk averse aerospace industry – Favors use of previously
qualified materials – Stifles materials innovation
Design the structure based on limitations
of the material
ELEMENTS
DETAILS
COMPONENTS
SUB-COMPONENTS
COUPONS
Current Practice
9 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
How AFRL is Approaching the Problem
• What is it not? – Just more computer modeling
• What is it? – Systems engineering on the
materials development process
– Digitization of the development process
– Backbone architecture – Standards & protocols for
simulations, data, testing, etc. – Metadata
Component Testing
Qualification Certification
Manufacturing
Sustainment
M&P Research
M&P Development
Component Design
Digital DATA
Integrated Computational Materials Science & Engineering (ICMSE)
10 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Integrated Computational Materials Science & Engineering (ICMSE)
• Risk averse aerospace industry • Favors use of
previously qualified materials
• Stifles materials innovation
Design the structure based on limitations of
the material
• Reduce risk early in acquisition process via virtual composite design, manufacturing & qualification • Expand material
design/selection options
• Early resolution of mfg scaling issues
Design the material based on structural
requirements
COUPONS
ELEMENTS
DETAILS
COMPONENTS
SUB-COMPONENTS
Current Practice
DoD Certification of Composite Structures Based on Building Block Approach
Opportunity
ICMSE = Computationally based materials discovery, design, development & sustainment
11 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Probabilistics & Uncertainty
Building Block Approach
• Recognizes structure at many scales
• Designed to quantify and mitigate risk
• What does this mean for materials?
COUPONS
ELEMENTS
DETAILS
COMPONENTS
SUB-COMPONENTS
12 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
How a Designer Sees a Material
•Material allowable – Distribution-based – Environment-specific
• A-Basis Allowable – At least 99% of material values
meet or exceed with 95% confidence
– Single point catastrophic failure with no load redistribution
• B-Basis Allowable – At least 90% of material values
meet or exceed with 95% confidence
– Redundant load path with load redistribution
1. R. Rice, R. Randall, J. Bakuckas, S. Thompson., "Development of MMPDS Handbook Aircraft Design Allowables". Prepared for the 7th Joint DOD/FAA/NASA Conference on Aging Aircraft, September 8-11, 2003, New Orleans, LA.
2. DOT/FAA/AR-03/19, Final Report, "Material Qualification and Equivalency for Polymer Matrix Composite Material System: Updated Procedure" Office of Aviation Research, Washington, D.C. 20591, U.S. Department of Transportation Federal Aviation Administration, September, 2003.
13 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
How a Materials Scientist Sees a Material
Dis
cipl
ine
Mat
eria
ls S
cien
ce
Phy
sics
C
hem
istry
Eng
inee
ring
pm nm µm mm m Length Scale
Electronic
Atomistic
Micro
Macro
14 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
The Disconnect
• Material allowable
• Probability distribution function of responses
• Variability – Many batches – All environments
• Mean response
• Deterministic simulations
• Laboratory-scale – Often single batch &
few test specimens – Often single
environment
Designer Needs: Materials Scientist Provides:
15 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Task at Hand
• To decrease the materials development timeline, materials scientists must start delivering the information designers require. – This task requires quantifying the uncertainty at
all levels (Verification & Validation across scales) • Experimental uncertainty • Computational uncertainty • Material state uncertainty
– Polymer (or other) chemistry – Microstructure (functional definitions of RVEs & SVEs) – Outlier statistics – Statistical distributions of properties
» Efficient sampling » Generation of outlier realizations
16 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Statistical Variation
Molecular Micro / Meso Coupon Subcomponent
•Part Dimensions •Coupon Props.
•Free Volume •Porosity •Chemical Structure
•Micro Geometry •Fiber Diameter •Constituent Props.
•Lamina Props.
17 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Uncertainty in Microstructure
• How do we quantify the statistical nature of the microstructure? – What details are
important? • Volume fraction • Fiber spacing(?) • Correlation functions(?)
– How does “importance” depend on properties of concern?
– NEED functional definitions for RVE & SVE
Vf = 0.527
Vf = 0.526
Vf = 0.535
18 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
• Sample Size • Dense Sampling • Scale effects • Incorporation of
experimental data – Bayesian
Methods(?) – Markov Chain
Monte Carlo(?)
Population Sampling Strategies
actual damage pattern
statistical realization
Case 1
statistical realization
Case 4
Experimental Load-POD Curves
Simulation Load-POD Curves
19 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Concluding Remarks
•Lightweight, efficient structures & materials are critical for current & future air & space assets
•Future assets are both enabled & held back by new materials development
• We can utilize current simulation capabilities to guide experiments today for new materials development and for better understanding of today’s materials – 2D Laminates – Carbon Fiber, Epoxy, Bismaleimide, Cyanate Ester, etc.
20 Distribution A: Approved for Public Release. Case #: 88ABW-2012-1871
Concluding Remarks
Technical hurdles for complete utilization… •The robust computational framework being developed must address critical issues – Materials maturation timeline – Multifunctionality and blending of materials &
structures – Optimal design in high dimensional spaces with
sparse data (curse of dimensionality) – Uncertainty due to phenomena occurring
simultaneously at many scales
ICMSE – systems engineering on materials design and development for a streamlined, digitized process
21 Distribution Statement A. Approved for Public Release
Questions?