The Structures & Materials Discipline within the NASA Subsonic Rotary Wing Project is focused on developing rotorcraft technologies. The technologies being developed are within the task areas of: 5.1.1 Life Prediction Methods for Engine Structures & Components 5.1.2 Erosion Resistant Coatings for Improved Turbine Blade Life 5.2.1 Crashworthiness 5.2.2 Methods for Prediction of Fatigue Damage & Self Healing 5.3.1 Propulsion High Temperature Materials 5.3.2 Lightweight Structures and Noise Integration The presentation will discuss rotorcraft specific technical challenges and needs as well as details of the work being conducted in the six task areas

Halbig, Michael C.

Johnson, Susan M.

NASA Technical Reports Server

NASA SUBSONIC ROTARY WING PROJECT - STRUCTURES 
AND MATERIALS DISCIPLINE 
 
Michael C. Halbig 
Army Research Laboratory, NASA Glenn Research Center 
Cleveland, OH, USA 
 
Susan M. Johnson 
NASA Glenn Research Center 
Cleveland, OH 
 
Abstract 
The Structures & Materials Discipline within the NASA Subsonic Rotary Wing Project is focused on developing 
rotorcraft technologies. The technologies being developed are within the task areas of: 
 5.1.1   Life Prediction Methods for Engine Structures & Components  
 5.1.2   Erosion Resistant Coatings for Improved Turbine Blade Life  
 5.2.1   Crashworthiness  
 5.2.2   Methods for Prediction of Fatigue Damage & Self Healing  
 5.3.1   Propulsion High Temperature Materials  
 5.3.2   Lightweight Structures and Noise Integration  
The presentation will discuss rotorcraft specific technical challenges and needs as well as details of the work being 
conducted in the six task areas. 
https://ntrs.nasa.gov/search.jsp?R=20130013122 2019-08-31T00:56:00+00:00Z
1Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
NASA Subsonic Rotary Wing Project -
Structures & Materials Discipline
Michael C. Halbig - Associate Principal Investigator (API)
Contact info: (216) 433-2651, Michael.C.Halbig@nasa.gov
Susan M. Johnson – Associate Project Manager (APM)
Contact info: (216) 433-2163, Susan.M.Johnson@nasa.gov
Fundamental Aeronautics Program Annual Meeting
Atlanta, GA, October 7-9, 2008.
2Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
 Project Structure and Technology Focus
 Tasks Areas
5.1.1   Life Prediction Methods for Engine Structures & Components (GRC)
5.1.2   Erosion Resistant Coatings for Improved Turbine Blade Life (GRC)
5.2.1   Crashworthiness (LaRC)
5.2.2   Methods for Prediction of Fatigue Damage & Self Healing (LaRC)
5.3.1   Propulsion High Temperature Materials (GRC)
5.3.2   Lightweight Structures and Noise Integration (LaRC/GRC)
 Collaboration Mechanisms and Current NRAs 
Outline
3Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
Exploration 
Systems
Mission 
Directorates
Aeronautics 
Research
Science Space 
Operations
Programs Airspace 
Systems
Fundamental 
Aeronautics
Aviation 
Safety
Aeronautics 
Test
Subsonic 
Fixed Wing
Subsonic 
Rotary Wing
Supersonics HypersonicsProjects
Disciplines
Acoustics Aeromechanics Propulsion
Flight 
Dynamics & 
Control
Experimental 
Capabilities
Structures & 
Materials
Multi-
Disciplinary 
Analysis and 
Technology 
Development
The Structures & Materials Discipline within SRW
4Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
The SRW Project Management Structure
SRW Principal Investigator
Susan Gorton 
Associate Project Managers
Associate Principal Investigators
Project Manager
Barbara Esker
Project Scientist
Isaac López
Odilyn Santa Maria Susan Johnson Dan Dugan
Fundamental Aeronautics 
Program Director
Dr. Juan Alonso
Acoustics
Dr. David D. Boyd
Experimental 
Methods
Luther Jenkins
Structures & Materials
Michael C. Halbig
Propulsion
Dr. Chris DellaCorte Flight Dynamics 
& Control
Bill Decker
Aeromechanics
Tom Norman
Bob Kufeld
Special Projects
DoD Liaison: Mike Watts
NRTC Liaison: Dan Dugan
Special Projects
JPDO Liaison: 
Odilyn Santa Maria
Business Team Deb FindleyLead Analyst Julie Fowler Sandra Young
NRA Manager:
Karen Crandall
Multi-Disciplinary 
Analysis & Technology
Dr. Gloria Yamauchi
5Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
Unique Structures and Materials Issues For Rotorcraft
• Propulsion system
– Turboshaft engines vs emphasis on turbofans for fixed wing
– Higher temperature materials for improved efficiency, higher horsepower, reduced weight, and reduced 
emissions
– Engine mission cycle
• Short duration flight with hover and lift requirements (low cycle fatigue)
• Low altitude flight with take-off from unimproved sites (erosion)
• Airframe
– Unique durability and damage tolerance requirements 
• Local skin buckling is allowed in normal operation to minimize weight
– Crashworthiness
• Seats and other energy absorbing structures contribute significantly to human occupant survivability
• Must limit cabin volume reduction caused by heavy engine/transmission located on top of fuselage 
structure
• Propulsion/airframe integration
– Interior cabin noise caused by structure-born vibration from the gearbox
• Main rotor structures
– High axial loads combined with bending
– Particulate and rain erosion
– Challenges with fabrication and integration of controls and data acquisition systems
6Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
 Project Structure and Technology Focus
 Tasks Areas
5.1.1   Life Prediction Methods for Engine Structures & Components (GRC)
5.1.2   Erosion Resistant Coatings for Improved Turbine Blade Life (GRC)
5.2.1   Crashworthiness (LaRC)
5.2.2   Methods for Prediction of Fatigue Damage & Self Healing (LaRC)
5.3.1   Propulsion High Temperature Materials (GRC)
5.3.2   Lightweight Structures and Noise Integration (LaRC/GRC)
 Collaboration Mechanisms and Current NRAs 
Outline
7Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
• Objective
– Identify, evaluate and model key variables controlling fatigue life of rotary wing superalloy turbine 
disks:
• Non-metallic inclusions
• Machining damage
• Approach
– Experimental
• Study machining parameters of broaching speed, tool life (sharpness), and post-processing surface 
treatments
• Determine the effect of extrusion and forging strains on the size and shape of inclusions
• Perform LCF testing on realistic forging shapes
– Computational
• Development of the Probabilistic Life Prediction Model to Account for presence of inclusions in Nickel 
Powder Metallurgy (P/M) Turbine Components
• Integrate NASA GRC developed probabilistic life prediction method into the DARWIN probabilistic 
damage tolerance based life prediction code
• Current collaborations
– Honeywell - contract for machining study
– Southwest Research Institute - implementation of probabilistic life prediction methodology into the 
Darwin code
SRW Discipline: Structures & Materials
5.1.1 Life Prediction Methods for Engine Structures & Components (GRC)
POC: Jack Telesman, GRC
8Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
• Ceramic inclusions are the primary flaw in powder metallurgy superalloys
• Processing affects the local alloy microstructure and flaw distribution
• Surface defects occur as a result of machining, finishing, and damage
The probability of failure depends on materials, processing, 
damage, design, and engine operating conditions
SRW Discipline: Structures & Materials
5.1.1 Life Prediction Methods for Engine Structures & Components (GRC)
POC: Jack Telesman, GRC
Broach slot indicating regions of interest 
for microstructural evaluation and 
residual stress determination.
Stress distribution in a sector model of 
a stage two gas generator turbine disk.
Disk Stress ModelingMachining Studies and Stress Analysis
9Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
• Objectives
– Develop erosion models for realistic engine conditions in the turbine
– Develop thermal barrier coatings with improved erosion resistance
• Approach
– Experimental
• Add oxides to zirconia-yttria ceramic coatings to improve toughness
• Perform erosion tests at U of Cincinnati and at NASA
– Computational
• Develop a mechanics-based erosion model that accounts for sintering of the coating
• Current collaborations
– University of Cincinnati (NRA, PIs: Tabakoff and Hamed) - “Experimental and Numerical 
Simulation of TBC Erosion in Gas Turbines”
– Aviation Applied Technology Directorate - blades and lead for possible future engine test
– Howmet: PVD doped zirconia TBCs
– Army SBIR Phase II with Directed Vapor Technologies International, Inc. - collaboration and 
integration 
– Engine companies - contacts and possible supply of new scrap blades
SRW Discipline: Structures & Materials
5.1.2 Erosion Resistant Coatings for Improved Turbine Blade Life (GRC)
POC: Bob Miller and Dongming Zhu, GRC
10Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
Erosion resistance of turbine blade thermal barrier coatings
• Ingested particulates and carbon particles cause erosion
• The best (lowest thermal conductivity) coatings have poor erosion resistance
• Erosion models currently do not account for thermally-induced material changes
• The burner erosion rig can be run in the coatings screening mode or the model validation mode
Mach 0.3 - 1.0 burner erosion rig at NASA GRC
Candidate Thermal Barrier Coatings for Turbine 
Blade Applications are Doped Zirconia-Yttrias
SRW Discipline: Structures & Materials
5.1.2 Erosion Resistant Coatings for Improved Turbine Blade Life (GRC)
POC: Bob Miller and Dongming Zhu, GRC
11Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
• Objectives
– Demonstrate advanced structural concepts for crash energy management
– Improve predictive capabilities for structural impact and multi-terrain impact
• Approach
– Demonstrate energy absorbing concepts by component crash testing
– Validate advanced simulation methods through component and full scale testing
• Tests to evaluate HeloWerks skid gear are completed 
• Crash tests of two MD 530 helicopters are planned – one with external airbags and the second with 
a deployable energy absorber
• Current collaborations
– U.S. Army Aviation Applied Technology Directorate (AATD) – Survivable, Affordable, 
Repairable Airframe Program (SARAP) test
– Bell Helicopter, Sikorsky, Boeing - Information exchange on future crash testing
– Stanford (NRA, PI: Fu-Kuo Chang) – “Crash Energy Absorption of Composite Rotorcraft 
Structures”
SRW Discipline: Structures & Materials
5.2.1 Crashworthiness (LaRC)
POC: Karen Jackson, LaRC
12Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
LS-DYNA shell skid gear 
analysis model and test article.
Test article.
Composite fuselage section shown 
in the load test machine at AATD.
Vertical Drop Test of the Sikorsky 
Test Validation Article (TVA) 
– Survivable, Affordable, 
Repairable Airframe Program 
(SARAP)
WASP Skid Gear
SRW Discipline: Structures & Materials
5.2.1 Crashworthiness (LaRC)
POC: Karen Jackson, LaRC
Linear deployment Radial deployment
Fuselage retrofit LS-DYNA model
Deployable Energy Absorber (DEA) 
concept developed at NASA LaRC
13Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
• Objective
– Improve the durability and damage tolerance of composite rotorcraft structure
• Approach
– Perform fatigue tests on stiffened thin skin specimens to determine if z-pinning combined 
with a self healing matrix can reduce delamination and improve fatigue life
– Measure residual compressive strength of impacted sandwich structures
• Identify failure modes
• Develop new analytical techniques to predict residual strength
– Use flex beam specimens (high axial loading with bending) to evaluate the effect of 
embedded sensors on fatigue life in rotor structures
• Current collaborations
– Center of Rotorcraft Innovation (CRI) - SAA through NASA Aircraft Aging and Durability 
Project, “Development of a Delamination Fatigue Methodology for Composite Structures”
– Bell Helicopters – Supplier of flex beams with embedded sensors
SRW Discipline: Structures & Materials
5.2.2 Methods for Prediction of Fatigue Damage & Self Healing (LaRC)
POC: Kevin O’Brien, LaRC (ARL/VTD)
14Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
Approaches for improved durability and damage tolerance
Flex beam specimen test
 
      
    
Z-pin reinforced composite 
flange
SRW Discipline: Structures & Materials
5.2.2 Methods for Prediction of Fatigue Damage & Self Healing (LaRC)
POC: Kevin O’Brien, LaRC (ARL/VTD)
Micro-encapsulation 
technique for self-
healing
Self healing matrix combined with through 
thickness reinforcement to improve fatigue life
Failure modes and analysis methods for alternative  
sandwich structures and core materials
Effect of embedded sensors on 
fatigue life of rotor structures
15Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
• Objectives
– Determine advantages of substituting metallic material with monolithic ceramics (i.e. 
Si3N4) and fiber reinforced ceramic matrix composites (CMCs) (i.e. SiC/SiC) for:
• turbine engine components 
• transmission components.
• Approach
– Perform engine system analysis and trade-off studies to determine the feasibility and 
benefits of using advanced monolithic and CMC in a T-700 engine. 
– Design and predict stress in turbine components of advanced materials.  
– Develop joining technology for fabricating complex shaped ceramic components and for 
integration with dissimilar materials (i.e. metal alloy).
– Fabricate/procure and test components.
• Current collaborations
– Coatings for silicon nitride
• Ceramatech (coating development)
• Cleveland State University (coating development and modeling) 
SRW Discipline: Structures & Materials
5.3.1 Propulsion High Temperature Materials (GRC)
POC: Mike Halbig, GRC
16Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
x
SRW Discipline: Structures & Materials
5.3.1 Propulsion High Temperature Materials (GRC)
POC: Mike Halbig, GRC
The stages of a T700 turbo-shaft engine.  Note: HP-High pressure; 
HPT-High pressure turbine, S-Stator (Vane), R-Rotor (Blade)
For case of no LPT bleed and T4 matching, 
uncooled LPT components offer: 
• 31% increase in turbine shaft power 
• 11% decrease in BSFC
Polished cross-sections of Si3N4 joined to Si3N4 
using Ticusil braze (left), and Si3N4 using Copper-
ABA braze (right), and  Inconel 625 using Ticusil 
braze (below).
Joining and Integration of CeramicsTrade Study for Using Uncooled Ceramics in the 
Power or Low Pressure Turbine (LPT)
17Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
• Objectives
– Develop lightweight materials and structures for cabin treatment
– Develop methods for improved passive and active control of noise and vibration
• Approach
– Develop low density open cell absorber/core materials (polyimide foam, aerogels, hybrids)
– Provide composite materials to the Acoustics Discipline for vibration testing and modeling
– Review past work in passive and active control of noise and vibration and assess the 
potential for improvement with current materials and structures technology
• Current collaborations
– Polyumac Inc. (licensed NASA LaRC polyimide foam technology)
– Patz Materials and Technologies (SBIR) - “Optimized Cellular Core for Rotorcraft”
– Bell - Informal discussions on composite panel design for vibration testing and modeling
– Ohio State University’s Smart Vehicle Concept Center – assessment of the state of the art in 
active and passive noise control
SRW Discipline: Structures & Materials
5.3.2 Lightweight Structures and Noise integration (LaRC/GRC)
POC: Rob Bryant, LaRC; Chris Johnston, GRC
18Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
Lightweight hybrid foam concept
Goal is to reduce cabin noise without 
increasing weight
• Current work is focused on development of lightweight bulk 
absorbing materials and controlling the open cell structure to 
optimize sound absorption at specific frequencies
• Acoustic materials testing is used assess material performance 
and to provide inputs for the acoustic models
SRW Discipline: Structures & Materials
5.3.2 Lightweight Structures and Noise integration (LaRC/GRC)
POC: Rob Bryant, LaRC; Chris Johnston, GRC
GRC acoustic property screening lab consisting of:
- a modular acoustic impedance tube
- a flow resistance rig
At LaRC, detailed acoustic testing is done to obtain 
acoustic parameters for model development 
19Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
SRW Discipline: Structures & Materials
NRA (Round 1) – Experimental and Numerical Simulation of TBC Erosion 
in Gas Turbines, University of Cincinnati, Prof. Tabakoff and Prof. Hamed 
Goals:
– Measure erosion rate in properly 
simulated aero-thermal environment
– Assess advances in TBC erosion 
resistance
– Predict TBC erosion 
pattern on Turbine blades
10 mils TBC Cumulative Erosion Test Results
(T = 1800 F, V = 1000 ft/s , β = 90o & Total Qp = 15 g)
Sample ID
Winitial
(g)
Wfinal
(g)
∆W
(mg)
Qp
(g)
ε
(mg/g)
1a 6.9369 6.8134 123.5 5 24.70
1b 6.8134 6.6962 117.2 +5 23.44
1c 6.6962 6.5786 117.6 +5 23.52
Effect of Particle Size on 
Trajectories Through Rotor
30μ particles 1500μ particles
High Temperature 
Erosion Tunnel
20Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
SRW Discipline: Structures & Materials
NRA (Round 1) - Crash Energy Absorption of Composite Rotorcraft Structures, 
Stanford University. Prof. Fu-Kuo Chang
Tasks:  - Analysis to develop relevant damage modes and material response.
- Implementation of a dynamic material model into a commercial FEM code.
- Study of relevant parameter and improvements for energy absorption.
Test, Data, and Modeling at 650 LBS Load
Load - Displacement Diagram
0
200
400
600
800
1000
1200
0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45
Displacement [mm]
La
od
 [l
bs
]
650 lbs
Load - Displacement Diagram
0
200
400
600
800
1000
1200
0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45
Displacement [mm]
La
od
 [l
bs
]
450 lbsFour-point 
bend test 
with built-in 
acousto-
ultrasound 
sensors to 
monitor 
damage 
growth
Acoustic 
sensor 
data for 
unfolded 
tube
FEM 
model of 
four-point 
test
Load and 
displacement 
diagram at 
450 lbs (650 
lbs diagram 
not available)
21Fundamental Aeronautics Program Annual Meeting, October 7-9, 2008 Subsonic Rotary Wing Project
Summary
 The Structures & Materials Discipline is focused on technology areas 
that are most relevant to rotary wing applications.
 Resources are directed toward tasks where we can have the most 
significant impact on the structures and materials within the 
propulsion system and the airframe.
 Development of the technologies is leveraged with NRAs, SBIRs, 
SAAs, academic programs, and collaborations.
 The discipline is interested in continued collaboration and industry 
perspective on critical technology areas.


NASA Subsonic Rotary Wing Project - Structures and Materials Discipline

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