Materials and Processes for New Propulsion Systems with Reduced Environmental Impact

National Aeronautics and Space Administration

Materials and Processes for New Propulsion Systems

with Reduced Environmental Impact

Joseph Grady, Craig Robinson, Gary Roberts, Sandi Miller, Michael Halbig, Michael Pereira & Charles Ruggeri NASA Glenn Research Center Cleveland, Ohio Lee Kohlman NASA Ames Research Center Mountain View, California for presentation at th the 24 conference of the International Society for Air Breathing Engines in Canberra, Australia on September 22 - 27, 2019 www.nasa.gov

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NASA Glenn Core Competencies

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Presentation Topics

• Ceramic Matrix Composites

- CMC development & characterization - Environmental Barrier Coatings

• Polymer Matrix Composites

- Toughening for fan blade application - Lightweight hybrid Composite/Metal gear

• Additive Manufacturing Applications

- Ceramic Matrix Composites - High Power Density Electric Motors www.nasa.gov 3

National Aeronautics and Space Administration NASA 2700 ° F CMC combines three technology advancements • Creep-resistant Sylramic-iBN SiC fiber • Advanced 3D fiber architecture CVI SiC • Hybrid CVI-PIP SiC matrix PIP SiC www.nasa.gov 4 4

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Creep and fatigue tests demonstrated durability

of 3D hybrid-matrix CMC at 2700ºF (1482ºC)

Creep Rupture Challenge Durable 2700°F Ceramic Matrix Composites will reduce cooling air required for turbine engine components, increasing engine efficiency and reducing fuel burn and emissions Approach Characterize mechanical properties and durability of TTT-developed CMC at 2700 º F Fatigue (SPLCF)

CMC shows 1000 hours durability

at 2700ºF and 20 ksi (138 MPa)

in creep and fatigue

Contact: Ramakrishna.T.Bhatt@nasa.gov www.nasa.gov 5

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Environmental Barrier Coatings are needed

Higher temperature capability

• Mechanical properties (creep rupture, fatigue) • Oxidation resistance • Reduced cooling and/or higher turbine inlet temperature

Lightweight

• 1/3 of Ni-based superalloys

Performance Benefits

• Reduced fuel Consumption • Higher Thrust • Reduced Nox and CO emissions

SiC materials limited by water vapor attack

• SiO scale reacts w/ H O to form hydroxide species 2 2 • Results in severe recession of component

EBC

Bond Coat Without EBC, SiC matrix material reacts

with H O to cause recession and failure

SiC/SiC CMC

of SiC-based CMC

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Progress toward a durable 2700ºF CMC / EBC system

Durable CMC / EBC

APS Yb Si O EBC

2 2 7

PS-PVD & Slurry Coat

demonstrated in 2700ºF

Modified for Long Life

Process for Turbine Airfoils

turbine environment

• TGO is life-limiting failure mechanism for SOA 2400 F EBC  Gen 2 – Si/YbDi  H O primary Ox  TGO from Si BC • Al O /TiO known to reduce diffusivity in 2 3 2 SiO • Investigate effect of modifier oxides on TGO growth rates in Yb Si O 2 2 7 2400°F Steam Cycle Oxidation (90%) Cooled CMC / EBC Airfoils Slurry provides economical, non- Evaluated in Turbine Rig Tests line of sight, and chemistry friendliness. PS-PVD is a hybrid process (plasma and/or vapor) that • Synergy of failure mechanisms • (3) Test Articles, 45 hours total provides variable microstructure • Compared in-house against along with non-LOS .

commercial EBCs • Modified EBCs reduced TGO by 80% • ~20x life to reach TGO t fail • Hypothesis: modifiers dissolve in SiO TGO, modify structure, decrease Ox • Patents & more studies ongoing www.nasa.gov

National Aeronautics and Space Administration Fundamental Durability Tests Characterize EBC Failure Modes damage mechanisms are incorporated into life prediction models Thermomechanical CMAS Attack Steam Oxidation Durability & Infiltration Si(OH) H O Erosion and FOD Hydroxide Formation/Recession www.nasa.gov 8 K. N. Lee, “Environmental Barrier Coatings for CMC’s”; in Ceramic Matrix Composites , Wiley, New York (2015)

National Aeronautics and Space Administration Polymer Matrix Composites: Fan Blade

Fan Blade Application

Test Article Challenge : reduce impact damage without sacrificing in-plane properties or manufacturability Tapered cross section www.nasa.gov 9

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Thermoplastic Veil Interleave

• Melt-spun thermoplastic polyurethane veil was procured from Hills Inc, of Melbourne, FL.

• Veil areal weight: 15 gsm Photo courtesy of • Average diameter on the sub- interleave www.hillsinc.net/Fibers micron scale. (70 – 150 nm) • Benefit to veil approach: Reinforcement is placed where it provides the most benefit.

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Toughened Fan Blade Has Reduced Impact Damage

Baseline IM7/8551-7 Test article toughened with test article leading edge thermoplastic polyurethane damage after impact veil between plies www.nasa.gov

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Post-impact thermography

impact location toughened test article baseline test article (IM7/8551-7) (w/ thermoplastic veil) bottom side top side Thermoplastic veil interleave distributes impact energy more effectively in toughened composite (right side) www.nasa.gov

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Toughness vs. strength tradeoff

Tension and Compression Noveon TPU interleave resulted Data shows a drop of in-plane in a 7- fold increase in Mode II performance with increasing fracture toughness.

areal weight of veil www.nasa.gov

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Hybrid Composite-Steel Gear for Rotorcraft

Objective: Replace steel web helicopter gear with composite to reduce weight and noise due to vibration.

Challenge: Hybridization of dissimilar materials without sacrificing performance “hybrid” gear (15% weight reduction) Challenges: • Processing considerations at the flange in particular- low void, low wrinkling.

• Ensure high quality laminates in complex architectures • Reduce processing time and cost while maintaining aerospace grade performance.

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Additive Manufacturing: GRC Composites Research

ExOne M-Flex Binder Jet machine: Powder bed process with tailored binders and chopped fibers for CMC fabrication n-Scrypt direct printing machine: • Multi-material systems • Ceramic pastes, electronic pastes, adhesives, solders, plastics Multi-material stator for high power density electric motor www.nasa.gov 15

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The first CMC turbine engine components

by additive manufacturing

first stage nozzle segments high pressure turbine nozzle segments cooled doublet nozzle sections contact: michael.c.halbig @nasa.gov SiC/SiC CMCs have 20% chopped SiC fiber www.nasa.gov

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Densification of Binder Jet Fabricated SiC

Binder Jet Machine Density of Green Printed SiC PIP Densification Contact: Craig.E.Smith@nasa.gov www.nasa.gov 17

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Additive Manufacturing for Electric Motor Fabrication

Objective: Use additive manufacturing methods to fabricate electric motors with higher efficiency and power density Approach: • Use Direct Printing and Electron Beam Freeform processes to build lightweight and compact rotor, stator & motor housings for advanced motors • Measure improvements in motor efficiency and power density compared to baseline SOA motor Urban Air Mobility Application AM motor design enables a 2x increase in power density (8 kW/kg) Baseline Motor : Advanced Motor Design with AM components 7.5-inch diam and 4 lbs www.nasa.gov Contact: Michael.C.Halbig@nasa.gov

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Motor components optimized for power density

using Additive Manufacturing methods

Baseline motor: reduced weight of power density = 4 kW/kg structural housing 67% power density doubled to 8 kW/kg using Additive Mfg methods to fabricate motor components optimized fabrication process integrated airfoil-shaped for wire-embedded stator cooling fins into motor housing www.nasa.gov 19

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Summary

NASA Glenn Research Center has recently demonstrated a range of new high temperature and lightweight materials technologies to enable reduced emissions and fuel burn in aircraft engines, including: • Ceramic Matrix Composites and Environmental Barrier Coatings for 2700 º F turbine operation, reducing the need for cooling air and increasing engine efficiency • A toughened Polymer Matrix Composite that significantly reduces impact damage in fan and nacelle structures • A hybrid composite/steel gear concept that reduces gear weight by 15%, demonstrating feasibility of multi-speed drive systems for power transmission in rotorcraft • New Additive Manufacturing processes to fabricate components that double the SOA power density (to 10 kW/kg) of UAV electric motors www.nasa.gov 20