2. stargel - multi-scale

Multi-Scale Structural

Mechanics and Prognosis 18 March 2011

Dr. David Stargel

Program Manager

AFOSR/RSA

Air Force Office of Scientific Research

AFOSR

Distribution A: Approved for public release; distribution is unlimited. 88ABW-2011-0794

2

Structural Mechanics

• Structural Health Monitoring

• Non-destructive Evaluation

• Prognostics

• Physics-based Modeling

Thrusts

Novel Flight Structures

Multi-scale Modeling and Prognosis

• Morphing Aircraft

• Flapping Wing Air Vehicles

• Non-traditional Structural Configurations

Structural Dynamics

• Thermo-acoustic Response

• Space Structures

• Penetration Mechanics

ISHM Untested

Flight

System

Making Today’s

Technology Obsolete

3


• Uncertainty/Variability

• Probability of Detection

• Verification & Validation

• Time & Length Scale Couplings

Challenges

Novel Flight Structures

Multi-scale Modeling and Prognosis

• Multi-disciplinary Design Problems

• Non-traditional Structural Configurations

• Student Education

Structural Dynamics

• Computation Cost

• Non-linear Interactions

• Testing Environments

ISHM Untested

Flight

System

4

Novel Flight Structures: Fundamental Research Trends

• “Disruptive” new flight structures concepts and unprecedented

flight configurations

• Reconfigurable adaptive flight structures with on-demand shape

morphing for real-time responce to changing missions demands

and threats

• Hybrid flight structures of dissimilar materials (metallic,

composite, ceramic acting together) under dynamic loads, blast,

and sustained extreme environments:– Ceramic matrix composites

– Multi-material joints and/or interfaces

• Conventional strength-based analysis of metallic structures (TR)

• Multi-scale predictive modeling for combined design of

structures and materials

5

Structural Dynamics: Fundamental Research Trends

• Control of dynamic response of extremely flexible nonlinear flight

structures

• Modeling of unsteady energy flow in nonlinear flight structures at

various flight regimes

• Nonlinear dynamics of thin-wall structures of functionally-graded

hybrid materials with internal vascular networks under extreme

thermo-acoustic loading conditions

• Classical modal analysis and linear vibration control (TR)

• Nonlinear structural dynamics in interaction with air flow, unsteady

heating, directed energy, servo-controls at various regimes

• New modeling methods for guided wave propagation and nonlinear

vibrations (e.g., spectral finite elements; peridynamics; etc.)

6

Multi-scale modeling and prognosis: Fundamental Research Trends

• Stochastic prediction of the structural flaws distribution and

service-induced damage on each aircraft and at fleet level

• Probabilistic analysis that accounts for variability due to

materials, processing, fabrication, maintenance actions,

changing mission profiles typical of Air Force applications

• Conventional fatigue analysis of metallic structures for fixed-

life structural design/prognosis

• On-board health monitoring and embedded NDE of flight

structures: unprecedented sensing methods; compact

structures and material prognosis algorithms

• Prediction of flight structures “hot spots” prone to early in-

service failure and/or degradation

• Prognosis of advanced structures: simultaneous SHM/NDE

and analysis of the interacting material and structural

behaviors under long-term in-service conditions

7

Structural Mechanics Vision of Future Weapon Systems

Past Present Future

Few tests represent

aircraft fleet

CAE supplements

experimental fleet models

Each aircraft has its

own virtual twin

8


• NASA - Ed Glaessgen/Steve Smith

• ARO/ARL - David Stepp/Jim Chang

• ONR - Ignacio Perez/Liming Salvino/David Shifler

• NSF - Glaucio Paulino

• DTRA – Su Peiris

• MURI on Uncertainty – Fariba Fahroo

• Mathematics for Multi-Scale Modeling – Fariba Fahroo

• RB/RX Collaborative Lab Task –Ravi Chona/Tom Eason/Reji John

• MURI on Hybrid Structures –Joycelyn Harrison/Ali Sayir

Collaborations

9

AFOSR/NASA Space Act Agreement

10

Excerpt from NASA Roadmap –A Transition

Future


own virtual twin

Multi-Scale Simulation for Structural Reliability

AFOSR RB-RX Collaborative Lab Task: Proposal Plan

AFOSR Program: Multi-scale Structural Mechanics

Program Manager: Dr. David Stargel

28 January 2011

PIs: Ravi Chona*, Tom Eason* and Reji John**

Air Force Research Laboratory, AFRL

*Air Vehicles Directorate, **Materials & Manufacturing Directorate

Wright-Patterson Air Force Base, OH, 45433

Scientific Challenge and Impact

How can material-level damage evolution & accumulation best

inform structural-level reliability assessment … and vice versa?

Needed: A framework for propagating information across length scales

drilling down only as far as absolutely necessary

Fracture

surface

Secon

dary im

ages

Essential to realizing the Digital Twin vision

nano micro meso macro

Long-Term Goal and Objectives

• Goal

– Identify and optimize the linkage of robust models having the

appropriate volume element dimension to predict location

specific properties as a function of temperature, environment,

stress and time

• Objectives

– Explore the sensitivity of structural airframe component models

to the multiscale elements focused on the microscale structural

degradation mechanism

– Identify optimized triggering mechanisms leading to the

appropriate high fidelity model without drilling down to the

atomistic level (unless absolutely necessary)

– Demonstrate feasibility of approach and computational results

via experimental validation• FY17 - Simulate variability in structural scale predictions due to material scale

uncertainties

Accomplishments

FY09-FY10-FY11

A visco-plastic-damage mechanics model

incorporating the effects of oxygen concentration:

• Initiated development of a multiscale computational

framework (Variational Multi-scale Enrichment method)

– Efficient enrichment of structural scale simulations with

information from grain scale (micro-scale) simulations

• Characterized Oxygen enriched region in Ti-6242S at

anticipated use temperatures

– Up to 650°C (1200°F), 420 hours

– Limited data available in this range

• Developed 1D diffusion microstructure-sensitive model

incorporating partial O2 & temperature = f(time)

• Developed 2D microstructure-based finite element

diffusion analysis

– Actual microstructure from high resolution backscattered

image; Grain geometry represented explicitly in 2D

• Developed model to relate critical strain to onset of

widespread cracking under tensile loading

Next (Bridging) Steps

• FY12

– Integrate Oxygen ingress and tensile cracking models into the

Variational Multi-scale Enrichment (VME) method

– Validate ability to predict Oxygen ingress effects at micro and meso

scales

– Initiate development of a coupled isothermal crystal plasticity – oxygen

transport model

– Initiate investigation of effects of non-monotonic, repetitive loading on

Oxygen ingress induced damage

– Develop detailed research work plan for Way Forward

• FY17– Simulate variability in structural scale predictions due to material scale

uncertainties

– Conduct full-scale structural validation

AFOSR-MURI

Functionally Graded Hybrid Composites

17

Synthesis, Characterization and Prognostic

Modeling of Functionally Graded Hybrid

Composites for Extreme Environments

Principal Investigator

Dimitris C. Lagoudas

Department of Aerospace Engineering

Texas A&M University

College Station, TX 77843

Partner Universities

Texas A&M University

University of Illinois at Urbana-Champaign

Virginia Polytechnic Institute and State University

Stanford University

University of Dayton Research Institute

http://muri18.tamu.edu

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AFOSR-MURI


Goals

A comprehensive research program coupling thermal-

acoustic-mechanical flight loads to guide the design of

multi-functional Functionally Graded Hybrid Composite

(FGHC) systems with integrated sensing capabilities for

extreme environments.

multi-scale simulations

multi-scale characterization

Target operating environment: 250 °C - 1000 °C, with a durability

envelope of 1000 hours exposure at 550 °C and 300 thermal

cycles

18






AFOSR-MURI


Mn+1AXn Phases (n = 1, 2 and 3)

211 312 413

Easy to form and machine

Stiff (320 GPa) and tough

Good thermal and electrical conductor

Thermal shock and fatigue resistant

Oxidation resistant (in air up to 1400°C).

Low friction






AFOSR-MURI


Joining PMC

w/ GCMeC,

embedded

SHM sensors

Fundamentals of FGHC

Multi-scale

Characterization

Multiscale Structural

Modelling

Structural

Health

Monitoring

Fabrication

PMC

GCMeC

1000C

300-400C

• Initial material

parameters

• Validation

experiments






AFOSR-MURI

Functionally Graded Hybrid Composites21

Research Thrusts

Development and Fabrication Develop multifunctional FGHC

with multiple layers: a ceramic thermal barrier layer, a graded ceramic/metal

composite (GCMeC) layer and a high-temperature polymer matrix composite

(PMC) layer.

Multi-scale Characterization Develop and apply experimental

techniques to obtain mechanical andphysical properties of GCMeC and PMC

layers and of the hybrid interfaces.

Insitu NDE/SHM Integrate of SHM capabilities through networked

sensor/actuator arrays,diagnostic algorithm development, control theory and

fabrication optimization.

Multi-scale Modeling Develop of novel material systems for use in

extreme environments: design FGHC microstructure, develop experiments

and interpret data to obtain basic material properties.






Exciting New Initiatives

Transformation Computing in

Aerospace Science & Engineering

Future, 2025…

Tomorrow, 2015

Today, 2011

PMs: David Stargel & Douglas Smith

(T–CASE)

• To create transformational approaches in computing for aerospace science and engineering

• Multi-disciplinary approach including novel computer architectures, system software, and mathematical algorithms

• Emphasis on• Multi-scale modeling & structural

mechanics• Complex flow physics modeling & control

Novel micro-architectures?

Hybrid/complementary

photonic methods?

Quantum-based systems?

Bio-computing?

Neuro-morphic computing?

25

Structural Mechanics Summary

Past Present Future

Few tests represent

aircraft fleet

CAE supplements

experimental fleet models


own virtual twin

• Three core thrusts with the integrating vision of a

Virtual Twin Concept

•Vision is expanding across other organizations

• Program is coordinated and actively collaborating

with other government agencies and within AFOSR

• Joint Roadmap Development with NASA

• Exploring new transformational capabilities

• AFOSR is leading the way

• Questions??

BACKUP CHARTS

Initial Approach

• Explore the incorporation of

time and location specific

properties on component life

via modeling

• Investigate refining life

models using reasonable

multi-scale feedback /

communication approaches

• Validate results via sub-scale

laboratory structural testing

Define needed framework by identifying critical elements and the

interplay of sensitivity and triggering mechanisms

• Understand the role of

microstructure variation

• Develop damage evolution

physics and short crack growth

initiation and growth

understanding via the use of

limited laboratory sub-scale

coupon tests

• Enable subscale model feedback

mechanism from macroscopic

model

Demonstrate this framework using a metallic system (Ti-6242S)

subjected to thermal-mechanical fatigue

The Way Forward

• FY13– Develop a coupled isothermal crystal plasticity – oxygen transport model that

accounts for different phases (alpha, beta, grain boundary) and temperature

cycle effects

• FY14– Incorporate geometric nonlinearity into the Variational Multi-scale Enrichment

(VME) framework and implement highly-parallelizable computational strategies

– Understand effects of fatigue loading, tension vs. compression, partial O2

pressure on oxygen ingress

• FY15– Conduct structural scale isothermal validation

– Implement adaptive VME approach to track critical oxygen concentration front

– Develop 3D microstructure-based diffusion model

– Develop mechanistic model to predict remaining ductility and life

• FY16– Conduct structural scale thermal-mechanical fatigue validation

– Add field discontinuities (e.g., cracks) to VME framework

– Enhance oxygen ingress model to account for thermal cycles, gradients, stress

level, and presence of damage

• FY17– Simulate variability in structural scale predictions due to material scale

uncertainties

– Conduct full-scale structural validation

AFOSR-MURI

Functionally Graded Hybrid Composites29

Multi-scale Characterization

INTERFACES AND BONDED JOINTS

Thermal Impedance

Interfacial Delamination

cm

nm

mm

mm

Graded Ceramic/Metal Matrix Composites

Polymer/Matrix Composites

Local Strain Fields/Damage Initiation

CHARACTERIZATION OF COMPOSITE LAYERS

STRUCTURAL PERFORMANCE

Impact Response

Vibration Analysis






AFOSR-MURI


High Temperature SHM/NDE

In-situ characterization of the integrity of FGHC

Sensors & Sensing Network

Diagnostic Algorithms

Modeling

Integration & Characterization






AFOSR-MURI


Multi-scale Modeling Wide Range of Scales

Expedite mechanical & thermal design

Predict performance of material & components

Develop strategies for joining parts

Define in-flight mechanical & thermal loads






AFOSR-MURI


SPARK PLASMA SINTERING SYSTEM

Impact on the MURI project:

• Rapid synthesis of GCMeC;

• Better control of phase distribution in GCMeC;

• Lowering the co-sintering temperature of GCMeC;

• Gradual phase transition in GCMeC;

• Homogeneous and fully dense GCMeC;

• SPS has been proven to be successful technique for

co-sintering composites and functionally graded

composites with MAX phases.

Ti2AlC-TiAl composite

fabricated by SPS1.

1Y. M. Luo, P. Wei, S. Q. Li, R. G. Wang, J. Q. Li, Materials Science and Engineering A, 2003, 345, 99.

2 B. Mei, o. Y. Miya, Materials Chemistry and Physics 2002, 75, 291.


fabricated by SPS2.






AFOSR-MURI


MATERIALS

Ceramic MAX Phase Metal Composites

Ti2AlC

Ti – Ti2AlC

Ni50Ti50 - Ti3SiC2(Ti2AlC)

GCMeC

PROCESSING & CHARACTERIZATION

Karaman, Radovic, Lagoudas

MODELING Lagoudas, Whitcomb, Gao, Reddy, Ochoa






AFOSR-MURI


Mn+1AXn Phases (n = 1, 2 and 3)

211 312 413

Easy to form and machine

Stiff (320 GPa) and tough

Good thermal and electrical conductor

Thermal shock and fatigue resistant

Oxidation resistant (in air up to 1400°C).

Low friction






AFOSR-MURI


Powder Mixing

Cold Pressing

Sintering at 1400 OC – 4 hrs

Sintered Ti2AlC

Sintering of Ti2AlC CeramicsPorosity of Ti2AlC samples after sintering at

1400°C for 4 hrs Under 96% H2, 4%Ar

Porosity due to pressure-less sintering






AFOSR-MURI


Oxidation of Ti2AlC

Oxide Layer

XRD and EDS analysis on the oxidized surfaces

show formation of mainly protective Al2O3 with

some traces on TiO2 on the surface, which

subsequently controls further oxidation

Oxidation kinetics of the self-healing protective oxide on ceramic

Ti2AlC

Oxidation in air

1200°C 72 hrs

Al

C

O

Ti

EDS Map 0

200

400

600

800

1000

1200

1400

20 30 40 50 60In

ten

sit

y (

a.u

.)

2Theta

0

500

1000

1500

2000

2500

20 30 40 50 60

Inte

nsi

ty (

a.u

.)

2Theta

TiO2

Ti3AlC2

Ti2AlC

TiC

Al2O3

Oxide Surface

0

300

600

900

1200

1500

20 30 40 50 60

In

ten

sit

y (

a.u

.)

2Theta

0

500

1000

1500

2000

2500

20 30 40 50 60

Inte

nsi

ty (

a.u

.)

2Theta

TiO2

Ti3AlC2

Ti2AlC

TiC

Al2O3

Oxide layer after slight surface

grinding

TiO2

Ti3AlC2

Ti2AlC

TiC

Al2O3

TiO2

Ti3AlC2

Ti2AlC

TiC

Al2O3






AFOSR-MURI


500 mm

100% Ti2AlC100% Ti

Graded Ti – Ti2AlC Composite

Sintered at

1000OC for

4 hours

* The color figure is optical

image, and the grayscale

figures are BSE






AFOSR-MURI


Processing Porous MAX Phase

PreformsTi2AlC-35%

Porous

Disadvantages of processing porous MAX

samples without pore formers:

• Small pore size.

• Low green body strength of the samples

sintered at lower temperatures.






AFOSR-MURI


Highly Reflective TBCof Nano-Porous Aluminum Oxide

M∞

x

Emission and reflection

Thermal

radiation from

hot gas

Blunt body

Bow shock

Th

erm

ally

gro

wn

oxid

e

Bo

nd

co

at

Functionally

graded material

Incident

radiation

Convection

Absorption

Reflection and

emission

Conduction

Ceramic

coating

Transmission

Multi-layer coating to increase

reflectivity TBC

Supersonic

flow

High radiative and convective heat flux on high speed airplane structures

Thermal barrier coating (TBC) with high reflectivity and low thermal

conductivity protects the base structure






AFOSR-MURI


Ni50Ti50 - Ti3SiC2 or Ti2AlC Composite

Ni50Ti50

Interface ~20 mm

Ti₃SiC₂

controlling the interface thickness

Ti₃SiC₂

Ni50Ti50

Interface ~50 mm

Ti2AlC

4

5

6

7

8

9

Interface ~20 mm0

5

10

15

20

Hardness(GPa)

Interface

NiTi

Ti3SiC2 1

2

3

4710

1316

19






AFOSR-MURI


Polyimid Based

Actively Cooled

MATERIALS

High Temperature

Polymer Matrix Composites


Ounaies, Sottos, White

MODELING

Geubelle, Ochoa






AFOSR-MURI


Ti-Polyimide Adhesion

Joining GCMeC and PMC: Focus on Titanium and

Polyimide as a first step

In order to achieve favorable adhesion the following parameters

are investigated with SLS tests

Cure cycle of polyimide

Surface treatment of Ti

Substrate Length = 4” (100.16mm)

Substrate

Thickness =

0.063” (1.6mm)

Overlap Length =

1” (2.54mm)

Adhesive Thickness =

10-30 μm






AFOSR-MURI


Curing Effect on SLS Results

Cure Cycle Max Load /

Area

Standard 409.4 psi

Short B-Stage 334.4 psi

Long B-Stage 254.6 psi

•Standard cure was chosen as curing method.

•B-Stage cure can be used to minimize thermal residual stresses.

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0.000 0.050 0.100 0.150 0.200 0.250

Fo

rce (

N)

Displacement (mm)

Standard Cure - B

5 hour) D

12 hour) A






AFOSR-MURI


Etching Effect on SLS Results

The acid etching increased the maximum tensile force

that an SLS sample could sustain before failing.

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0.000 0.100 0.200 0.300 0.400 0.500 0.600

Fo

rce (

N)

Displacement (mm)

0 min. Acid Etch

30 min. Acid Etch1 hour Acid Etch

0

100

200

300

400

500

600

700

800

900

1000

0 minutes 30 minutes 1 hour 6 hourA

vera

ge M

ax S

tress (

psi)






AFOSR-MURI


AC-PMC

Sacrificial fibers in red integrated within the 3D preform weave

are removed during post-cure to form microvascular networks

Active cooling is provided by coolant flow through embedded

network

Concept of Active Cooling






AFOSR-MURI


Evacuated Microchannel

Solid Fiber

Development of SF Prototypes

Embedding Fibers Fiber Evacuation

1-D Specimen Mold

2-D Specimen Mold

Shell Wall of Evacuated Microchannel

100%

Evacu

atio

n

Curing Process

1-D and 2-D molds for

embedding sacrificial fibers

Fiber evacuation by two step

heating at 220°C (12 hrs) and

250°C (2 hrs) in vacuum

Material System

EPON 828/EPIKURE 300

Ratio { 100 : 22.7 }

Room temperature

curing for 24 hours

followed by curing for

90 mins at 82°C and

90 mins at 150°C

Chloroform can clean residue in the channels






AFOSR-MURI


3-D Woven Composite Prototype

with embedded microchannels

a) 3-D woven glass fiber mat containing sacrificial PLA fibers (pink)

a) Optical image of evacuated microchannels partially filled with

fluid (blue) (scale bar = 5 mm)

a) MicroCT image showing 3D microstructure of embedded

microchannels in a 3D woven composite (scale bar = 10 mm)






AFOSR-MURI


Analysis Tools

FEM Solution +

Genetic Algorithms (NSGA-II)

conduction

qm.

→

convection

Objective functions:

Maximum solid temperature

Void volume fraction

Pressure drop

Constraint:

Connected networks

Fluid temperature

Analysis Options:

Constant inflow rate

Constant power

Constant inflow rate design sample

Constant power design sample

Design of Micro channels






AFOSR-MURI


Impact of Cooling






AFOSR-MURI


FUNCTIONAL INTEGRATION


Chang, Lafdi, Lagoudas, Seidel,

MODELING

Chang, Lagoudas, Ochoa, Seidel, Whitcomb

SHM Network

Sensors

Interfaces






AFOSR-MURI


High Temp In-Situ SHM/NDE

Development of high temperature sensors and sensor networks (maximum

temperature 1000°C)

Manufacturing of hybrid composites (IM7 or IM6) integrated with our sensor

network (maximum temperatures 300°C)

Diagnostics

Develop a sensor network that can be fabricated at the micro-scale

and be expanded to the macro-scale and that can stand working

temperatures up to 1000C

+-+ ++--






AFOSR-MURI


Diagnostics

Input Signal Output SignalSimulation

Wave propagation simulation using

SEM

Adhesive layer

PZT

Modeling of PZT and adhesive layer

Future steps: Test panels to examine signals at elevated temperatures (below

maximum temperature that the network can stand)






AFOSR-MURI


Developing HT Sensors

With proper tolerance factors, perovskite structures around

morphortropic phase boundary can exhibit both high Tc and high

piezoelectric properties.

(1-x) BiScO3 – x PbTiO3 (x~0.63), which has a relatively high

piezoelectric coefficient and high thermal depoling resistance, can be a

good candidate for the SHM sensor network.

Use screen printer to fabricate thin (10~100 μm) BSPT high Tc

piezoelectric sensors

Control the grains/domains of these thin BSPT sensors






AFOSR-MURI


ABO3

High Piezoelectric Effect :

Perovskite Structure

Perovskite Tolerance Factor

of ABO3:

(1-x) ABO3-(x) PbTiO3

Another morphortropic

phase boundary (MPB) A

O B

ri : ionic radius of atom i

Perovskite structures with composition

around MPB exhibit high piezoelectric

properties!






AFOSR-MURI


Thermal Depoling Test

Fabricated ultrasonic sensors BS-PT (x=0.63) and compared with PZT.

All samples were measured at room temperature after a 2-hour exposure at specific

set temperatures.






AFOSR-MURI


CNT Based Fuzzy Interface

6mm

Ceramics

Metal

Composite

Aligned CNT

Fuzzy Fiber

SHM

Curly CNT






AFOSR-MURI


Sensor Development: Fuzzy Fiber

Conductivity changes

Strain, damage

CNTinclude viscoelastic effects and

damping frequency response

CVD CNT grown on

glass & carbon fiber






AFOSR-MURI


Wedge RVE for Glass-CNT Fiber

wedge of the full volume

apply a combination of

periodic and symmetry

boundary conditions

Obtain effective properties

to compare with those

acquired by multi-layer

composite cylinder method.






AFOSR-MURI


CNT on T650-8H Fabric LayerFracture Toughness

Fabricated laminates

with fuzzy midplane

Conducted DCB tests

Improvement is 2X

over traditional (w/o FF)






AFOSR-MURI


CNT grown on Ti






AFOSR-MURI


CNT - Thermal Impedance Study the effect of thermal contact resistance on heat transfer

capability and the effectiveness of CNT as thermal interface materials.

CVD on quartz-- aligned CNTs with

thickness ranging from several micrometers

to about 200 um with a narrow diameter

distribution around 10 nm






AFOSR-MURI


Damping & Modulus of Ti2AlCOberst Beam Method

62

Almost doubles the damping

Determined material and

damping properties of Ti2AIC on

an Al substrate (ASTM Standard E756-05)

estimated static Young’s

modulus of 5.52 GPa

loss factor of 0.0349






AFOSR-MURI


MULTI-SCALE

STRUCTURAL RESPONSE

CHARACTERIZATION

Goulbourne, Inman, Lafdi, Ochoa, Lagoudas

MODELING

Inman, Whitcomb, Lagoudas, Reddy, Cizmas,

Ochoa






AFOSR-MURI


3-D X-ray Tomography & FEA

Obtain microstructure

images

Porous NiTi

GCMeC

Translate into FE mesh

Study of failure of metal-ceramic composite with

detailed consideration of microstructure

Ti-Ti2AlC composite

(2D SEM image)

Porous SMA

(3D CT image)

finite element analysis of

representative volume elements

of metal-ceramic composites

under tension, compression and

shear loading






AFOSR-MURI


Simulation of Ceramic Phase with SMA

Porous NiTi images were used as a base

Pores changed to be ceramic content

Some pores along the edges were not

converted

Mesh is created directly from image voxels

• Linear, 8-node elements

Each voxel is 9.8μm 0

50

100

150

200

250

300

350

400

450

0 0.01 0.02 0.03 0.04 0.05 0.06

Stre

ss (M

Pa)

Strain ε (%)

20:1 Small

15:1 Small

20:1 Large

15:1 Large






AFOSR-MURI


Employing a cubic RVE containing a tetrakaidecahedral cell or a 4-strut reinforcing sub-unit:

Using variational bounding theoremsmodified micromechanics results and FEM Validated by comparing with each other Applied to al matrix with alumina reinforcing phase

-

MICROMECHANICS MODELS FOR GCMEC

Interpenetrating Phase Composite

1.12E+11

1.22E+11

1.32E+11

1.42E+11

1.52E+11

1.62E+11

1.72E+11

1.82E+11

0 0.05 0.1 0.15 0.2 0.25 0.3

Volume Fraction

Eff

ective

Yo

un

g's

Mo

du

lus

Voigt

Reuss

FEM-Unit cell

FEM-Ey of four

strut modelFEM-Ex of four

strut modelHS upper bound

1HS lower bound

1Tuchinskii upper

boundTuchinskii lower

boundshear lag model






AFOSR-MURI


Simpleware Mesh from

Synthesized μCT Data

Synthesized μCT slices of plain

weave textile

Simpleware mesh using upcoming

mesh decimation algorithm

Typical hex mesh

of plain weave unit cell

(in-house code)






AFOSR-MURI


Oxidation Progression through

Plain-Weave Composite

GoalsPrediction of oxidation progression

Precursor to predicting mechanical response of an

oxidized configuration






AFOSR-MURI


Integrally woven stringer-stiffened panel

Microstructure

Macroscopic deformationmodes

Local failure analysis

Material or structural redesign

Micromechanics

Structural analysis

Effective properties

Macro elements

Integrated Multiscale FE Analysis






AFOSR-MURI


Impact Response of Novel Materials

SEM Image of

Ti2AlC

Fragment






AFOSR-MURI


Impact and DIC Measurements

2.5 3 3.5 4 4.5 5 5.5

x 10-3

0

500

Conta

ct

Forc

e (

N)

time (s)

shot_04 Impactor Contact Force Trace, Muzzle Velocity = 13.8566 m/s

2.5 3 3.5 4 4.5 5 5.5

x 10-3

0

5Z

Dis

p (

mm

)

Contact Force

Displacement

Force and displacement data during impact

via accelerometer [Impactor velocity: 14 m/s]






AFOSR-MURI


Impact Loading

Multilayer Polymer Plates

PC/TPU/PMMA samples were instrumented

with piezoelectric transducers, then

impacted at progressively increasing speeds

using gas gun. Impedance measurements

were taken before and after each impact






AFOSR-MURI


Measuring Damage from

Consistent Force Impacts

Successive

Impacts

Increasing

Damage

Impact 1

Number of Spars 4

Max Spar-Spar Length 0.8 "

Radial Diameter -

Impact 2

Number of Spars 5


Radial Diameter 0.137”

Impact 3

Number of Spars 5


Radial Diameter 0.141"

Impact 4

Number of Spars 5

Max Spar-Spar Length 0.9"

Radial Diameter 0.171"

Crack

Characteristics

8 m/s, cracking, no delamination

8 m/s, cracking, delamination

8 m/s, cracking and

delamination growth






AFOSR-MURI


High Order Finite Elements of

Spectral/hp Type

Finite element approximation of variable u in two dimensions

e

1

ˆ in,,,

m

j

j

e

jhp yxuyxu

-1 -0.5 0 0.5 1-0.5

0

0.5

1

Multi-dimensional interpolation functions constructed from tensor

products of 1-D Lagrange interpolation functions of spectral type






AFOSR-MURI


Least-Squares Finite Element

Solution of FSI Problem

Results at t=0.25, 0.50 and 0.70 (a) velocity component vx (b) velocity component vy






AFOSR-MURI


Aerothermoelastic Response

Developed, verified and validated an efficient structural nonlinear beam

model that retains all cubic nonlinear terms

Predict the structural stresses and deformations that functionally-graded

hybrid composite (FGHC) materials would be subjected to due to

aerodynamics, inertial and thermal loads.

First eight frequencies of a 45 deg sweep wing

computed with Abaqus and the nonlinear beam model.






AFOSR-MURI


Collaborations In Place

AFRL/RX Hybrids Branch Jeff Baur

Benchmark IM7-BMI 5250 Panels for common tests

Fiber Metal Laminates interface-joining study

HT Polymer guidance

AFRL/RB Vehicles Directorate Thomas Eason

Structural –Thermal Loads

Boeing Gail Hahn, Kay Blohowiak

TiGr, HT Polymer-metal adhesion MOA signed






AFOSR-MURI


DURIP: ACQUISITION OF MECHANICALLY

ASSISTED SPARK PLASMA SINTERING SYSTEM

FOR ADVANCED RESEARCH AND EDUCATION ON

FUNCTIONALLY GRADED HYBRID MATERIALS

Investigators:

Dimitris Lagoudas, Aerospace Engineering, Texas A&M University

Miladin Radovic, Mechanical Engineering, Texas A&M University

Ibrahim Karaman, Mechanical Engineering, Texas A&M University

Zoubeida Ounaies, Aerospace Engineering, Texas A&M University






AFOSR-MURI



The spark plasma sintering (SPS) is a low pressure

sintering method . During the process, electrical

energy pulses is applied to the gaps between powder

materials and effectively utilizes the high energy of

the spark plasma generated momentarily between

powder particles by spark discharges to achieve

thermal and field diffusion. The pulsed current causes

melting and evaporation of surface of powder

particles without heating the particle interior.

Advantages:

- Better control of microstructure and grain growth

rate while obtaining a near theoretical density than

other sintering techniques.

- Sintering time is very short, in the order of few

seconds.

- Lower sintering temperature!






AFOSR-MURI



Impact on the MURI project:

• Rapid synthesis of GCMeC;

• Better control of phase distribution in GCMeC;

• Lowering the co-sintering temperature of GCMeC;

• Gradual phase transition in GCMeC;

• Homogeneous and fully dense GCMeC;

• SPS has been proven to be successful technique for

co-sintering composites and functionally graded

composites with MAX phases.


fabricated by SPS1.

1Y. M. Luo, P. Wei, S. Q. Li, R. G. Wang, J. Q. Li, Materials Science and Engineering A, 2003, 345, 99.

2 B. Mei, o. Y. Miya, Materials Chemistry and Physics 2002, 75, 291.


fabricated by SPS2.






AFOSR-MURI



Current status:

• Negotiations with 3 major SPS

manufactures are finished;

• Texas A&M provided adequate space –

plans for infrastructure needed for SPS in

progress.

• Expected installation – 6-7 months after

funds become available.






AFOSR-MURI


THANK YOU!








2. stargel - multi-scale

Documents