Multifunctional Polymers and Composites for Aerospace ... · Insulation Materials / Advanced Air...

National Aeronautics and Space Administration

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Multifunctional Polymers and Composites for Aerospace Applications

Tiffany S. Williams, Ph.D.Materials Chemistry and Physics Branch

NASA Glenn Research [email protected]

https://ntrs.nasa.gov/search.jsp?R=20190026444 2020-04-01T13:58:57+00:00Z


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Typical System Needs and Challenges in Aeronautics and Space

• System Challenges in Space

– Efficiency (mass and volume reduction)

– Degradation in harsh space environments

• Needs

– Lightweight materials and structures

– Materials and structures that can perform reliably in extreme environments

– Multi-functionality

• Radiation protection

• Impact resistant

• Smart materials

• System Challenges in Aeronautics

– Efficiency (power, cost)

– Mass, noise, emissions reduction

• Needs

– Higher strength and stiffness lightweight composites

– High temperature, toughened composites

– Thermal management

– Multi-functionality

• Morphing structures

• Electrically conductive composites

Min, J., Williams, T. et al, AIAA 2016-1501

Multi-functional structure with energy

storage capability

Shape Changing SMA - PMC Fan Blade

PM blade

blade tip t-dgc

M

l

10· •


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Novel Electrical Insulation

3


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Polymeric Materials for High Power Density Electric Motors• Benefits:

– Fuel Savings

– Noise Reduction

– Carbon and NOx Reduction

• Electrical Insulation Development• System need: Better thermal management for MW class,

high power density (>13 kW/kg) electric machines

• Thermally conductive electrical insulation necessary to optimize engine performance in hybrid electric motors

• Thermal conductivity of most electrical insulators: ~0.1 –0.2 W/mK

• Goal: ~1 W/mK thermal conductivity

• System challenges

• Pre-mature electrical insulation failure due to excessive heating and corona discharge

• Higher operating voltages, temperatures, and frequencies

Lightweight power transmission system

X-57 Maxwell all-electric


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Thermally Conductive Electrical Insulation

Dry spots

Breakdown voltage decreased by as much as 61% after large volume of additives were mixed with polymer

• Thermally Conductive, Electrical Insulation Needed• Copper wire

• Slot liner

• Potting material

• Incorporate conductive fillers to increase thermal conductivity of polymer insulation

• Adding dissimilar materials typically negatively impact insulation performance– Lower dielectric strength

– Higher chances of charge build up

– Decreased flexibility

– More interfacial polarization

• Grains and grain boundaries

> ~

QJ tlO C1J ...... 0 >

18 I - Neat siloxane

16 - 56 wt% filler/ 44 wt% siloxane

14 - 63 wt% filler/ 37 wt% siloxane

12

10

8

6

4

2

0

0:00:00 0:00:09 0 :00:17

Time (s)

I I I I I I I I I I I

6.0kV 8.0mm x150 SE(M) 4/21/2016 300um

0:00:26 0:00:35 ----------------


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Twin Screw Extrusion to Develop Thermally Conductive Electrical Insulation

• Advantages

– Improved polymer orientation

– Better filler dispersion and distribution

– Preferred filler directionality and alignment

– Capable of extruding large volumes of thin films and wire coating

• Process parameters

– Nanofillers? Micro-fillers? Nano/ micro- fillers?

– Effect of particle concentration

– Effect of filler material

• BN

• Mica

– Effect of filler geometry

• Sheets/platelets

• Particles

• Strand extrusion can be used for additive manufacturing

High temperature extruder

Extruded wire coating


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Characterizing Novel Electrical Insulation Candidates for Electric Machines

• Dielectric Analysis (DEA): Correlates chemical structure and end-use performance

– Thermal analysis tool traditionally used in manufacturing to optimize processing conditions and reduce scrap

– Provides information about dipole orientation and molecular relaxations, magnitude of conductivity, and magnitude of energy loss

• Electrical properties + molecular activity better understanding of thermo-electrical properties and chemistry to help design better insulation materials

Capacitance

Conductance

Phase shift

VOLTAG£

I CAPACITIVE

Time

loss angle

I

I MEASUR ED

phase angle

CONDUCTIVE

C (faJads) = I measured

V X applied

l /R (mhos) = I

measured X V

applied

sin e

2rcf

cos e


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DEA: Performance Prediction of Novel Electrical Insulation Candidates• What can DEA data tell us?

• Influence of crystallinity

• Cure-related information (kinetics, rheology)

• Frequency and temperature-dependent changes

• Changes in electrical properties due to environmental exposure (thermal breakdown, defects, moisture)

• Information Pertinent to Insulation Performance

• εʹ (relative permittivity)

• ε ʺ

• tan δ

• Ionic conductivity

• ε * (complex permittivity)

No applied field ----< 1----<--~1---· • · • · • • -------------------------<-~----•~<~~-----

• • • --------(£,-------.... Applied field

Pinduced = aE Induced dipole moment= polarizability x electric field


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DEA: Moisture and Thermal Effects on Dielectric Properties in Polyimide (PI)

Mass loss due to water loss

indiscernible in TGA • Water uptake in submerged

polyimide was ~2.1 wt%according to mass measurements

• Three commercial polyimide films investigated: (1) As received (AR); (2) Oven-dried; (3) Submerged in water

More polarizability in water submerged samples

Kapton

Frequency: 4 kHz AR PI Permittivity

Dry PI Permittivity

Submerged PI Permittivity

AR PI Ionic Conductivity

Dry PI Ionic Conductivity

Submerged PI Ionic Conductivity

Frequency Sweeps

‡Trade names and trademarks are used in this report for identification only. Their usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration.

120

100

80

e +-' ..c 60 -~ Q)

s 40

- Dry Pl (Air)

20 - AR Pl (Air)

- Submerged Pl (Air)

0

0 200 400 600 800 Temperature (Celsius)

-3 .5 -3.3 ,,l

,;I' ,,.

3 .1

·w

2.9

2.7 1 · ~

2.5

30 80 130 180 Temperature {Celsius)

60

soo ::I ;;:;· n

40g c.. -C n w -30~: ~ -'O

203 :::r 0 ..._ n

102,.

0

0

+< 0

3.5

3.3

3.1

2.9 0~ 2.7

2.5 L

:

0 I

(-0-o-Ot 0

• AR Pl (RT}

-.-AR Pl (100C}

• AR Pl (200C}

:: : 1 10 100 1goo 10000

Frequency \Hz) 100000


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DEA: Thermal Aging Effects on Dielectric Properties

Insulation Materials / Advanced Air Transport Technology Project / Advanced Air Vehicles Program 10

As-received PI film

Aged at 275°C (530°F) for 190 hours

• Thermal aging carried out to evaluate changes in chemical structure at potential operating temperatures

• Frequency sweeps on DEA performed at ambient temperature

• Polyimide Tg = ~381°C

Relative permittivity decrease suggests more rigid network formation during aging

2.9

2.8

2.7

2.6 w

2.5

2.4

2.3 1 10

• Aged 0 Days -+-Aged 8 Days + Aged 14 Days • Aged 21 Days

100 lQ0Q Frequency (Hz)

10000 100000


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Self-healable Electrical Insulation• Challenge: Polymeric aircraft electrical insulation is highly prone to damage by:

– Corona discharge at altitude

– Abrasion and cuts (maintenance)

– Damage to electrical insulation leads to electrical shorts and/or fires

• Need: Increase aircraft safety and longevity of electrical insulation over state-of-the-art insulation through self-healing

• State-of-the-Art Insulation: Polyimides

• Advantages

• Low dielectric constant and high dielectric breakdown voltage

• High thermal stability

• Disadvantages

• Moisture absorbance Electrical fires

11

Micro-cracks in polyimide after dielectric failure


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Typical Self-healing Mechanisms in Polymers

12

Extrinsic Healing Intrinsic “Reversible” Healing

Embedded microcapsules filled with healingagents that flow and polymerize when cracksare formed.

Microvascular networks filled with healing agentsthat flow and polymerize when cracks are formed.

Ionic clusters and other bonds that canbreak and reform

The number of healing cycles is limited with extrinsic healing approaches

• • • • • • • • • •••• • • •

·-·----------------·-·-----------------


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Ionically-crosslinked Polymers for Self-healable Electrical Insulation

Damaged Healed

SurlynIonomer

Damaged SurlynIonomer

Healed SurlynIonomer

Average Breakdown Voltage (kV)

16.8 ± 1.09 ~9.7 ~15.7

ε 1.567

Na+ ionomer achieved ~93% recovery in dielectric strength after healing. Over 85% recovery in mechanical strength.

No visible scars(full recovery not achieved)

Extended temperature dwell allows rearrangement of ionic networks

Material not suitable for applications with high operating temperature.

‡Trade names and trademarks are used in this report for identification only. Their usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration.

Na+ coo-

-----(CH2CHl -L6- cH 1-)x \ I 2 / .

CH3 y

Sodium lonomer

2.5

2

cil.5 Q.

~

0.5

0

0 1

- As-received Surlyn

- Healed

- Healed 70C 1 hr dwell

- Healed 70C 24 hr dwell

2 Strain%

3 4


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Textiles and Nano-reinforcement


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Structural Nanocomposites: Lightweight Structures• PMCs continue to play a significant role with reducing mass of aerospace structures• Objective: Determine if nanocomposites are a viable alternative to CFRP for composite overwrap

pressure vessels (COPVs)• Challenges with nanocomposites:

• Synthesis• Processing properties

• Goals:• Develop carbon nanotube (CNT) reinforced composites with 1.5 to 2x’s specific strength of

conventional carbon fiber composites• Improve strength of bulk CNT reinforcement through processing and post-processing

methods• Validate materials by design, fabrication, ground and flight testing of nanocomposite

overwrap pressure vessel

Split D-ring Mechanical Testing

COPV tank with nanocomposite overwrap

Williams, T., et. al, ACS Appl. Mater. Interfaces 2016, 8, 9327-9334

Flight-test preparation:Nanocomposite overwrap scale-up and burst-testing

c:7000.00

~6000.00-<

esooo.oo

·"' ~4000.00-

-64.14--=~ -~~----------~ ·20.14 300.00 600.00 900.00 1200.00 1500.00 1800 .00

PSI

350

'B'300

---~250 0.

~200 .c ti'o150 C ., t; 100 u -= so ·u ., a. 0 "'

(a) 0 As received O HEA X APA

~ ~ I

' ¢ Q)

4 0 5 10 15 20

Irradiation dose (x 1016 e/cm2) 25

7 (b) O As received

u 6 O HEA

1 u

--- X APA 00 --... 5 Ill 0.

f s 4 VI l ::,

3 D :5 $ ,:,

+ I

0 E 2 u -= 1 ¢ ·u .,

0 <D <D 0 a. "'

0 5 10 15 20 25 Irradiation dose (x 1016 e/cm2)


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SUCCESSES– Developed scalable processes to impregnate,

filament wind, and cure CNT composites– Over 2 km of prepreg processed and filament

wound during materials development stage– After 2017 flight test, nano-COPV effort led to

Phase III SBIR with Nanocomp to further improve CNT yarn and tape to reduce mass in aerospace structures

16

CNT Yarn Prepregger

Four axis CNC controlled Filament Winder

CNT COPV Manufacturing: CNT Overwrap Development via

Prepreg Filament Winding

Rings of CNT prepreg on mandrel

Autoclave-cured CNT overwrap

Spool of CNT yarn prepreg


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Tailorable Textiles: Hybrid Reinforcement with Increased Toughness

Hybrid textiles enable integration of functional fibers into conventional reinforcement

Carbon Fiber/ Epoxy Control

CNT Yarn – Carbon Fiber/Epoxy Hybrid

Resin Impregnated Tows Max Load (N) Tex Value (g/km) Density Increase (%)

Control 282.6 ± 73.1 392.6 ± 24.0 0.0

Hybrid A 445.1 ± 43.8 505.9 ± 46.5 28.8

Hybrid B 521.6 ± 60.0 543.0 ± 52.0 38.3

Hybrid C 494.9 ± 56.2 582.6 ± 45.2 48.4

Hybrid D 541.9 ± 13.5 675.5 ± 14.7 72.1

PMCs are limited in their ability to provide adequate toughness for some aerospace applications• Resin modifiers and additives• Nanostructures grown on reinforcement• Ply Stitching

Challenges • Toughened resins: $$$$ and difficult to process• Lack of controlled nanoparticle synthesis methods• Ply stitching damages carbon fibers

Tensile Failure of Fiber Tows

-

~ ---=-~...-:-- ---=----.. , ~"~--~ .... ..__________ - -

700

600

500

z 400 -0

"' _g 300

10

200

0

0

-

Tow splitting

Strategic placement of more ductile fibers in reinforcement could

minimize areas of high axial strains

" (b)

Full field strain DIC data NASA/TM-2015-218814

- HS 6 -- HS 9 -- CF_7 - CF 10 -

0

- HS 7 - HS 8 - -- HS - 10 - CF_6 - CF_8 - CF_9

1000 2000

Extension (mm)

1.2

1 x

QJ

?0.8 ..c t'!> ~ 0 .6 Vl u '5 0.4

QJ 0..

Vl

0 .2

3000 40 0 Control Hybrid A Hybrid B Hybrid C Hybrid D


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Tailorable Textiles: Toughened Hybrid Reinforcement

IM7 Carbon Fiber Control Braid

Braid speed (rpm)Mandrel speed (in./min)

𝛼

2= 𝑡𝑎𝑛−1

𝑅Ω

𝑉

R: Mandrel radiusΩ: Rotational speed of braidingV: Translational mandrel speed

Triaxial braid – A&P Technologies

2D Circular Braider

Carbon Fiber-CNT Yarn Hybrid Braid

28" long

(-)

Coverage Factor (C.F.)

S.A. fiber C.F.=----

S. A. mandrel

Carbon fiber - CNT Yarn Hybrid Triaxial Braided Tube

50 55

Braid A 60 ng/e


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Tailorable Textiles: Durable Electrically Conductive Textiles (E-textiles)

• E-textile uses in aerospace • Spacesuits• Sensors• Inflatables• Blankets• Health monitors

• Production• Screen printing with conductive polymers• Embroidery and stitching

• Stainless steel fibers• Metallic coating on non-conductive fibers

• Fabrics

Axial Axial

Braidingyarn

(warp)

Braidingyarn

(weft)

HybridTow

HybridTow

CarbonFiber

Carbon Fiber

Enhanced toughness

HybridTow

HybridTow

CarbonFiber

Carbon Fiber

Electrical conductivity

• Challenges with e-textiles• Durability• Reliability• Manufacturing challenges• Reparability• May not have good flexibility depending

on method

CNT yarn stitched circuit on ballistic Kevlar


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Tailorable Textiles: Shear Thickening Fluid (STF)– Enhanced Fabrics for Impact Energy Dissipation

• STFs are dilatant, colloidal suspensions that behave like a solid above a critical shear rate

• Hydrodynamic interactions between nanoparticles lead to stiffness increase

• STF-treated fabrics have been used as effective, puncture-resistant textiles for flexible body armor (Army Research Lab/ Univ. of Delaware)

• Can STFs provide protection against micro-meteor impacts in space?

Goal: Develop lightweight, flexible, impact-resistant textiles for inflatable habitat shells to provide protection against micro-meteoroid orbital debris fewer redundant layers mass reduction

Impact-resistant habitat shells and spacesuits

Cubic nanoparticles create stronger hydrodynamic interactions than spherical nanoparticles

Tailorable Text·les: Shear hicken·ng Fluid (STF)- Enhanced Fabrics for Impact E ergy Dissipation

l.0E+07

l.0E+06

l.0E+0S

'0'1.0E+04 C1J a.. ';:l.0E+03 --~ U')

8 l.0E+02 U')

> l.0E+0l

l.0E+00

l.0E-01

l.0E-02

• RT • 0C ••• •• -20C • -40C

• •

•• •• • ••••• •• ••• ...... :•,.

• • •••••• ••• • • • • • • • • •••••• • •

0.001 0.01 0.1 1 10 100 1000 Shear rate {1/s)


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Textiles: Shear Thickening Fluid – Enhanced Fabrics

Torsional Rheology of STF-treated Fabrics

• Torsional rheology of STF-treated fabrics showed slight increase in shear stress at higher frequencies

• Preliminary results from impact tests did not show improvement in energy absorption in STF-treated fabrics• Fabric too concentrated• Layup not ideal• Mixing/test methods not optimized

• Need better understanding of shear thickening mechanism in STF-treated textiles

Impact Testing STF-treated Fabrics30

25

--,

:;20 <].)

..c ,._ 0 ~ 15 ro > e_D <].) 10 C:

LU

5

• • •

::::~·.·.·:::~·.·.-::::·:::::·::::::·::::,, .. __ ,,, ... ·.:::::.·.t .. •

• • 7 layer weave STF • 7 layer weave AR RT

• • •

•··· Linear (7 layer weave STF)

0 L Linear (7 layer weave AR RT)

1000 1500 2000 2500 3000 Impact Velocity (ft/s)

Untreated Weave Impact velocity: 2350 ft/s

(Back)

1.40E+07

1.20E+07

- 1.00E+07 ro a..

~ 8.00E+06 ~ .....

V')

,._ 6.00E+06 ro <].)

..c V') 4.00E+06

-a-Kevlar Plain Weave - RT

..-1 to 1 Weave - RT

• 2 to 1 Weave - RT

2.00E+06

0.00E+00

.---.It--___ ...... r_, . ...---a • ..-------.11 • .--- •

• • • • 0

STF-treated Weave Impact velocity: 2401 ft/s

(Back)

25

• • • so 75 100 125


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Summary

• Polymers play an important role in multifunctional materials developmentmany projects are ongoing

• Mature polymer and composites processing and characterization methods are still viable to develop multi-functional materials

– Extrusion

– Filament winding/ prepreg production

– Braiding

– DEA

• Lots of potential to integrate multifunctionality into textiles

22


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Acknowledgements• Aeronautics Research Mission Directorate

– Advanced Air Transport Technology Project (AATT)

– Convergent Aeronautics Solutions Program CAS

• Space Technology Mission Directorate

– Center Innovation Fund

– STMD Game Changing

• Linda McCorkle: Microscopy and rheology

• Dan Scheiman: Thermal analysis

• John Thesken: NanoCOPV Flight test lead

• Brad Lerch: Mechanical testing facilities lead

• Dan Gorican: Filament winding

• Paula Heimann: Filament winding and CNT composites processing

• Nathan Wilmoth and Andrew Ring: CNT ring mechanical testing

• Chuck Ruggeri: Impact testing

• NASA Internship Program

• Industrial Partner: Nanocomp Technologies

23


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Multifunctional Polymers and Composites for Aerospace ... · Insulation Materials / Advanced Air...

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