NASA/CR-20 11-217076

Structural Framework for Flight:

NASA’s Role in Development of Advanced Composite Materials for Aircraft and Space Structures

Darrel R. Tenney and John G. Davis, Jr.

Analytical Services & Materials, Hampton, Virginia

Norman J. Johnston

Technical Consultant, Buena Vista, Colorado R. Byron Pipes

Purdue University, West Lafayette, Indiana Jack F. McGuire

Technical Consultant, Seattle, Washington

May 2011

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NASA/CR-20 11-217076

Structural Framework for Flight:

NASA’s Role in Development of Advanced Composite Materials for Aircraft and Space Structures

Darrel R. Tenney and John G. Davis, Jr.

Analytical Services & Materials, Hampton, Virginia

Norman J. Johnston

Technical Consultant, Buena Vista, Colorado R. Byron Pipes

Purdue University, West Lafayette, Indiana Jack F. McGuire

Technical Consultant, Seattle, Washington

National Aeronautics and Space Administration

Prepared for Langley Research Center under Contract NNL09AA1Z

Langley Research Center Hampton, Virginia 23681-2199

May 2011

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Research at

, NASA Langley Research Center on Advanced Composite Materials

Structural Framework for Flight: NASA’s Role in Development of Advanced Composite Materials For Aircraft and Space Structures


Dr. Darrel R. Tenney, Dr. John G. Davis, Jr., Dr. Norman Johnston,

Dr. R. Byron Pipes, and Mr. Jack F. McGuire


The authors acknowledge the NASA Langley Research Center for its support of this effort. A special thanks to Dr. Charles E. Harris, Dr. Richard D. Young, and Karen S. Whitley of Langley Research Center for their support, critique, helpful suggestions, and technical input. A special thanks also to Ms. Jean Lankes of AS&M for her dedicated support in preparing this Monograph. Also, a special thanks to Dr. Jalaiah Unnam President of Analytical Services and Materials for his support and help in this effort.

A special thanks also to Dr. Joseph Heyman for drafting the NDE section and to Dr. William H. Prosser for his support of the effort to draft the NDE Section. Also, we acknowledge and thank Dr. Philip Young for his contributions to the chemical characterization parts of this monograph. Appreciation is also expressed to Mr. Kenneth Matthew Tappan for the excellent work and support he provided during the literature research phase of this effort.

I also want to acknowledge the dedicated support and hard work of the AS&M technical team that labored many hours to research and draft the different sections of this monograph. Team member included Dr. Darrel R. Tenney, Dr. John G. Davis, Dr. Norman Johnston, Dr. Byron Pipes and Mr. Jack McGuire. I want to especially express thanks to Dr. Norm Johnston for his many hours of work to document the excellent contributions made by the outstanding polymer chemist and processing engineers that pioneered the development of numerous innovations in resin and composite development.

Finally a tribute is given to all the NASA Langley Materials and Structures Scientist and Engineers, Aerospace Industry Contractors, and University Faculty and Students who contributed to the development of advanced composites in support of National Aeronautics and Space Administration Programs. Recognition also goes to the technicians who performed much of the experimental work, and to the shop personnel at Langley that fabricated composite test specimens and fixtures over the past four decades of composite development at NASA Langley Research Center.

Dr. Darrel R. Tenney Hampton, Virginia September 15, 2010

Copyright © 2011

The use of trademarks or names of manufacturers in this publication is for accurate reporting and does not constitute an official endorsement, either expressed or implied, of such products or manufacturers by Analytical Services & Materials, Inc., or the National Aeronautics and Space Administration.

Boeing photos on cover used with permission.

Structural Framework for Flight




This document is intended to serve several purposes. First, as a source of collated information on Composite Research over the past four decades at National Aeronautics and Space Administration (NASA) Langley Research Center, it serves as a key reference for readers wishing to grasp the underlying principles and challenges associated with developing and applying advanced composite materials to new aerospace vehicle concepts. Second, it identifies the major obstacles encountered in developing and applying composites on advanced flight vehicles, as well as lessons learned in overcoming these obstacles. Third, it points out current barriers and challenges to further application of composites to planned and future vehicles. This is extremely valuable for steering research in the future, when new breakthroughs in new materials or processing science may eliminate/minimize some of the critical barriers that have traditionally blocked the expanded application of composite to new structural or revolutionary vehicle concepts. Finally, a review of past work and identification of future challenges will hopefully inspire new research opportunities and development of revolutionary materials and structural concepts to revolutionize future flight vehicles. The specific objectives of this Structural Framework for Flight: NASA ’s Role in Development of Composite Materials for Aircraft and Space Structures monograph are:

1. Knowledge Capture - The intent is to capture and distill into one document, selected examples of the major advancements made to the composite materials knowledge base, generated in the nearly four decades of research performed at the Langley Research Center or under Langley-sponsored grants and contracts. From 1970 through 2010, NASA’s Structures and Materials research on composites was aimed at developing the foundational technologies required to mature composite materials to the point where they could be certified for primary load-carrying aircraft and spacecraft structures. The goal was to improve performance and reduce weight and cost of aerospace vehicles and spacecraft. Thousands of technical reports on the results of NASA’s research were published in the open literature, and many thousands of technical talks were presented at national and international meetings. These reports and talks were authored by: NASA researchers, academic researchers working on NASA-sponsored grants and cooperative agreements, research partners in other government research laboratories, and industry researchers working on NASA-sponsored contracts. Although several books have been published on NASA’s contributions to Aerodynamics and Flight Systems, this is the first attempt at performing and documenting a comprehensive knowledge capture of the Structures and Materials Research on Advanced Composite Materials performed and/or sponsored by Langley.

2. Lessons Learned - During the course of these forty years of research on composite, many lessons were learned on both the methods and approaches used in the conduct of the research, and the principal findings coming from this research. In this study, emphasis was placed on both identification of the lessons learned and on identifying the primary


Structural Framework for Flight


factors which either contributed to successful completion of research objectives or failure to meet planned milestones.

3. Assessment of Technology Readiness - The study assessed the technology readiness of composites for application to innovative new vehicle concept, and potential new uses for space exploration or new space science instruments. This information is valuable for selection of highest payoff projects for funding.

4. Identification of Grand Challenges for the Future - This study identified the major technical challenges remaining to be solved for expanded use of lightweight composite structures for future advanced concept air vehicles, advanced space launch vehicles, and high-performance space hardware for space science and space exploration missions.

This monograph is organized to look at: the successful application of composites on aircraft and space launch vehicles, the role of NASA in enabling these applications for each different class of flight vehicles, and a discussion of the major advancements made in discipline areas of research. In each section, key personnel and selected references are included. These references are intended to provide additional information for technical specialists and others who desire a more in-depth discussion of the contributions. Also in each section, lessons learned and future challenges are highlighted to help guide technical personnel either in the conduct or management of current and future research projects related to advanced composite materials.

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Executive Summary of Composite Research at NASA Langley

Executive Summary of Composite Research at NASA Langley

By all accounts the composite research conducted at Langley Research Center over the past four decades has been judged to be outstanding in its contributions to the application of advanced composite materials to aerospace systems and to the fundamental understanding that has enhanced application of composites to non-aerospace applications. In this document, the authors have attempted to identify the major contributions and lessons learned in the conduct of both focused and base research on composite materials and structures at Langley Research Center. Although this has been a daunting task, they have captured and distilled valuable information on the composites research programs implemented and the impact of this research. Some of this information comes from the collective experience of the authors, who spent much of their professional career either directly conducting research on composites or managing composite- related research projects and/or programs. Much additional insight was gained from an exhaustive study of the literature and contract reports generated on Langley-funded research projects. Also, valuable information and crucial insight was provided by retired and current researchers engaged in projects where composite structure was a key technology area.

The lessons learned in this section are presented in more detail in the different sections of the document. In most cases, the authors have attempted to synthesize the multiple lessons learned from all the different sections of this monograph into a higher-level look at the key knowledge gained from this study. However, these top-level comments are not intended to supplant the more detailed comments presented at the end of each section.

Based on the results of this examination of the composite materials and structures research, the grand challenges for the expanded utilization of advanced composites in near term vehicle applications and the longer-term application of advanced composite structures to revolutionary new aircraft and launch vehicle concepts, have been identified. These challenges are based upon lessons learned, and are intended to provide guidance to technical personnel and management in the planning and execution of current and future research projects related to advanced composite materials.

Major Contributions

1 . Flight Service - Langley provided leadership and stimulus to the commercial aircraft industry, airline operators, and the Federal Aviation Administration (FAA) for the application of advanced composites on commercial aircraft. This was accomplished through the building and long-term flight-testing of secondary structural components. A key element of this success was building a strong partnership between NASA, industry, and the FAA in the conduct of the research, and the validation of the flight- worthiness of composite structures in real flight service.

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Executive Summary of Composite Research at NASA Langley

2. Educated Workforce - Langley proactively worked with universities to develop composite education programs at the graduate level to provide an educated workforce in the emerging disciplines necessary to advance composite technologies. Graduates of these programs were hired by NASA, industry, and other government agencies, and became major contributors to the development of composites. A specific example of the success of this effort is the NASA-Virginia Tech Composites Program.

3. Foundational Technology Base - Langley Research and Development (R&D) Base and Focused programs were the primary source of the foundational technology base required to commit to the use of composites in aircraft and space launch vehicle primary structures. This included a fundamental understanding of materials behavior, fabrication technologies, test methods, inspection methodologies, structural analyses, and environmental effects. Testing articles ranged from coupons to built-up structural components as large as the 40-ft. semi-span wing.

4. Support for Development of Airworthiness - Solutions to technical problems that posed an issue for flight safety were developed by Langley in close cooperation with the FAA. This included development of test standards, inspection criteria, analyses codes, and other methodologies to insure airworthiness of composite structures. FAA composite specialists were included on NASA’s advisory committees and in working groups.

5. Methodology to Predict Failure - Langley pioneered development of global/local analysis procedures combined with a “building block” approach to understand and predict the initiation and propagation of damage in composites. The scope of this work ranged from molecular-level modeling to finite element modeling of stress gradients in large built-up structural components.

6. Damage Tolerance - Langley developed a fundamental understanding of the relations between impact events and residual strength of composites. The importance of non-visible impact damage on compression strength led to the development of toughened resin systems which are in use today. The transition from brittle epoxies to toughened resins systems overcame a major barrier to the utilization of composite in primary aircraft structures. Also, Langley’s pioneering work on stitching demonstrated that the damage tolerance of built-up structure could be significantly improved by utilizing through-the -thickness stitching to suppress delamination and stiffener pull-off.

7. Environmental Effects - Langley R&D Base and Focused Programs were a primary source of the foundational technology base required to predict the effects of moisture, fuels, fluids, UV, and lightening on composites. The scope of this research included short-term and multiyear exposure to ground, flight and space (LDEF) experiments, residual strength tests, and development of analytical models to predict effects on material properties.

8. Synthesis of High-temperature Resins and Adhesives - Langley pioneered development of resins and adhesives for potential application to space vehicles, supersonic and high-speed aircraft. The research included molecular modeling, formulation, processing studies, and characterization. Numerous formulations have been registered under LARC™ and several of the phenylethynyl-terminated imide (PETI) series are available from commercial sources.

Structural Framework for Flight


Executive Summary of Composite Research at NASA Langley

9. Crashworthiness - Langley, in conjunction with the U.S. Army-Aerostructures Directorate, led the research on energy absorption of composite structures in aircraft and rotorcraft. Lundamental failure and crushing modes for subfloor structure were identified and graphite/epoxy structures were shown to be more efficient energy absorbers than aluminum. Crash qualification tests of the Bell and Sikorsky Advanced Composite Airframe Program (ACAP) helicopters and several all- composite general aviation aircraft were conducted in the NASA Langley Research Center Impact Dynamics Research facility.

10. Automated Fabrication - NASA Langley provided leadership and support in the development and/or utilization of processes that lowered the costs and improved quality of composite structures. Major contributions included: development of the advanced stitching machine for the semi-span wing, use of textile weaving and braiding machines to build frames and panel inserts, modification of resin formulations to accommodate tow placement, and modeling of resin infusion processes. Methods used to fabricate parts of the B787 and A380 can be traced to these advancements.

1 1 . Quantitative Nondestructive Evaluation (NDE) - Langley has been a leader in this technical area and worked with Industry and the FAA to identify the appropriate NDE techniques to establish airworthiness of aircraft composite components. Langley pioneered the development of physics based modeling to enable predictive capability of NDE technologies in the fields of radiography, ultrasonics, thermography, electromagnetics, and optics. Langley established a microfocus X-ray CT system with 12.5pm pixel resolution for imaging and quantifying porosity, stitching materials, inclusion, debonding, material loss and other microscopic flaws.

12. Graphite Fiber Risk Analyses - Langley led a national program to assess the potential impact of graphite fibers that could be released from a civil aircraft accident. The potential commercial, legal, and military effects were thought to be enormous and had the potential to prevent the future application of composites to civil aircraft. Langley staff conducted a three-year analytical and experimental investigation that provided sound scientific bases which indicated that the threat was not a problem.

Major Lessons Learned

Langley conducted an extremely productive R&D program on advanced composite materials over the past forty years. Following are the major lessons learned .

1 . Leadership - Key leaders at Langley (Richard Heldenfels) and NASA Headquarters (Allen Lovelace) had the foresight to recognize that in 1970, composites was a revolutionary new technology (a new S Curve) with the potential to significantly improve the performance of aerospace structures. They also made a commitment of a critical mass of personnel and resources to a new emerging technology. Both of these actions were essential to making significant contributions in a timely manner.


Structural Framework for Flight

Executive Summary of Composite Research at NASA Langley

2. Sustained Commitment - Langley was able to sustain a healthy R&D program in composites for nearly four decades by:

a) Having an excellence in research and a long track record of positive accomplishments

b) Engaging in industry, universities and other government agencies as partners in planning and implementing the research

c) Practicing excellent project management: meeting milestones and deliverables on time and within budget

d) Working with NASA-level advisory committees to achieve agency budget priority and technical level advisory committees for guidance and technical critique of work

3. Model for Success - An implementation model for success was a sustaining Research and Technology (R&T) base program combined with focused technology projects. The combination of base and focused projects allowed the long-term problems to be addressed in the base program and the near-term higher Technology Readiness Level (TRL) R&D to be implemented with industry in the focused programs. The combination promoted an efficient use of funding, facilities, and personnel.

4. Proactive Education and Training - A proactive education (NASA-Virginia Tech Composites Program plus others) and training thrust was a critical ingredient in advancing a new technology area. Langley personnel actively engaged in the formation and execution of new technical societies and technical subgroups to advance discipline-specific areas.

5. Multidisciplinary Research - A multidisciplinary approach was used to solve tough technical issues typically beyond the scope of any single discipline. In particular, the interaction between polymer chemistry and structural mechanics proved to be very successful in solving damage tolerance issues.

6. Building Block Approach - This approach was used to accurately predict failure of complex built up structure. The combination of analytical modeling to predict failure and experimental validation tests was a critical ingredient in the success of the building block approach championed by Langley.

7. Structural Analyses - Development of new analyses codes and capabilities were a critical ingredient in gaining new insights and fundamental understanding of new phenomena in a new technology area. Executing existing codes was no longer sufficient. Projected future increases in computational power and speed will enable development of new analyses codes to address ever more complex stress states.

8. Bridging Technologies - Synergy with neighboring disciplines proved to be a successful approach for integrating new ideas and solutions into the composite research. Specific examples include the use of algorithms developed by the pharmaceutical industry for molecular modeling and the use of technologies


Structural Framework for Flight

Executive Summary of Composite Research at NASA Langley

developed by the textile industry for the weaving, braiding, and stitching of graphite preforms.

9. Uncertainty Planning - None of the composite projects were fully funded to the original plan. Major intermediate milestones need to be planned with this in mind so that major accomplishments can still be made if the projects gets re-planned or terminated. These accomplishments can provide a basis for future planning and advocating for additional funding.

10. Archiving Data - A plan and process to secure and archive key data needs to be an integral part of any project plan. The common practice of “handing off’ key data, test procedures, or other critical information to the next researcher on the project was not effective for archiving data. Changes in personnel assignments, transfers, and periodic “building clean-up” lead to loss of data, test specimens, and in some cases, test fixtures.

1 1 . Personnel Mobility - An environment that encourages movement of researchers to and from base and focused R&D programs without prejudice is needed.

12. New Challenges - Langley must reenergize the structures and materials research disciplines to meet future challenges and opportunities associated with the stringent performance and safety requirements of tomorrow’s revolutionary vehicle concepts. A “Grand Challenges” planning team needs to search out new technologies for the next “S Curve” opportunity and identify payoff necessary to advocate for new initiatives.

Grand Challenges

Section 1 8 of this monograph contains a discussion of nine different “Grand Challenges” which include:

1 . Certification by analyses

2. Materials by design: multi-scale modeling and measurements

3. High fidelity failure prediction: micro and nanoscopic mechanisms

4. Realize benefits of nanocomposites: multifunctional materials systems

5. Intelligent materials and structures: larger, more integrated structure

6. Pervasive composite knowledge and learning: isotropic plasticity thinking

7. Reliability-based design

8. Non-autoclave, low pressure material systems

9. Research in the “Google Age”

Additional study of these challenges is recommended to identify the highest priority for advocating a new initiative in Structures and Materials. This initiative needs to be bold and offer a revolutionary advancement in structures for tomorrow’s air and space vehicles. A funding level of $40-50M/yr is required to aggressively pursue revolutionary new technology advancements with a critical mass of personnel and facilities.

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Executive Summary of Composite Research at NASA Langley

Having stated that additional study is required on each of the above Grand Challenges, it is the belief of our team that Intelligent Nanoreinforced Composites is a strong candidate for the next major advancement in composites technology. Nanoreinforcement has the potential to increase mechanical properties by orders of magnitude. Nanoelectronics is an emerging new area and molecular computation is on the horizon. It is envisioned that the polymer matrix could contain “smart segments” that are capable of sensing, feeling, thinking, storing data, and reacting to changes in the environment. Composites could have smart skins that are capable of detecting even the slightest impact event and could record the magnitude of the event and transmit this data to an onboard smart system if significant damage begins to initiate and propagate from the impact site. The composite is not only a load carrying structure, it is a smart-sensing, responding structural system that enhances the performance and safety of the system as a whole. The leap from composites as we know them today to intelligent nanoreinforced composites is a new technology “S Curve” that Langley is well positioned to advocate and champion. This would reenergize the materials and structures disciplines in a way that is reminiscent of the radical transformation that occurred when Langley stopped work on aluminum structures to launch a major new effort to exploit the potential of graphite-reinforced resins in the early 1970s.

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Acknowledgements ii

Preface iii

Executive Summary of Composite Research at NASA Langley v

Contents xi

1. Introduction 1

2. Success Stories and NASA LaRC’s Role 3

2.1. Commercial T ransport Aircraft 3

2.2. General Aviation Aircraft 8

2.3. Military Fighter Aircraft 9

2.4. Military Transports 13

2.5. Rotorcraft 14

2.6. Earth and Space Science Aircraft 1 8

2.6.1 Environmental Research Aircraft and Sensor Technology 18

2.6.2 Helios Failure Investigation 20

2.6.3 Mars Aircraft 22

2.7. Space Launch Vehicles 24

2.8. Space Structures 25

3. NASA’s Engagement in Composites Research 27

3.1. Major Drivers for Langley’s Composites Research Programs 27

3.1.1 Impact of National and World Events on National Science and

Technology Policy 27

3.1.2 NASA Priorities and Programs in Response to OSTP Guidance 28

3.2. Base and Focused R&D Projects that Funded Composites Research at NASA

Langley 31

3.3. NASA and FAA Cooperative Research 34

3.4. Graduate Education Composites Program 35

3.5. NASA Langley Programmatic Lessons Learned 39

4. Subsonic Transport Aircraft Research 43

4. 1 . Composites Environmental Exposure Program 43

4.2. Aircraft Energy Efficiency Composites Program 53

4.3. Graphite Fiber Risk Analyses Program 68

4.4. Textile Composites 71

4.5. Advanced Composites Technology (ACT) Program 76

4.5.1 ACT Transport Wing 81

4.5.2 ACT Fuselage Program 94

4.5.3 ACT Cost Modeling (COSTADE) 97

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4.5.4 Recent Advancement in Stitched Composites 98

4.6. Structures Investigation of the American Airlines Flight 587 Accident 1 04

4.6.1 Introduction 105

4.6.2 Review of Airbus A300-600 Certification 105

4.6.3 Model Development and V alidation 106

4.6.4 Failure Scenario Development and Validation 108

4.6.5 Confirmation of Most Likely Failure Scenario 116

4.6.6 Failure Sequence Analysis 120

4.6.7 Conclusions 123

4.7. Lessons Learned and Future Direction 124

5. Commercial Transport Application of Composite Materials 126

5.1. Lessons Learned 126

5.1.1 Design 126

5.1.2 Manufacturing 128

5.1.3 Airline Operations 130

5 .2. Major Recent Advancements 131

5.3. Emerging Challenges 133

5.4. Future Directions 136

6. Supersonic Transport Research 137

6. 1 . Historical Background 137

6.2. SCAR Program 141

6.3. High Speed Research (HSR) Program 150

6.3.1 Introduction 151

6.3.2 Resin/Composite Development 152

6.3.3 Scale-up Application and Test 153

6.3.4 Aging Studies 154

6.3.5 Structures 160

6.4. Fundamental Aero Supersonic Project 1 66

6.5. Lessons Learned and Future Direction 169

7. General Aviation 170

7.1. B eech Starship 170

7.2. Advanced General Aviation Transport Experiments Composites 171

7.3. Lesson Learned and Future Direction 1 80

8. Rotorcraft 181

8.1. Crashworthiness 181

8.2. Energy Absorption Materials and Concepts 1 83

8.3. Lessons Learned and Future Direction 188

9. Launch Vehicles 189

9. 1 . Shuttle Cargo Bay Doors 1 90

9.2. Composite for Advanced Space Transportation Systems (CASTS) 191

9.3. Composite Cryotanks 195


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9.3.1 State-of-the-Art USAF DC-X and NASA Contributions with the

DC-XA 196

9.3.2 NASA Technology Development Structural Tests Related to Use of

Composites on a Future RLV 196

9.3.3 The NASA X-33 Vehicle and Composite Cryotanks 198

9.3.4 Failure of the Composite Cryotank: Microcracking and Other

Causes 201

9.4. Ares I and Ares V Launch Vehicles 206

9.5. Composite Crew Module 212

9.6. Lessons Learned and Future Direction 215

10. Space Materials and Structures 216

10.1. Space Materials Development 216

10.2. Space Structures 217

10.3. Space Environmental Effects 218

10.4. Dimensional Stability of Composites 220

10.5. The Long Duration Exposure Facility (LDEF) 222

10.6. Lessons Learned and Future Direction 227

11. High-Temperature Polymer Technology Developed at NASA Langley 228

11.1. Fiber and Resin Development Timelines 228

1 1 .2. Early Days and the Building of a New Group 230

1 1 .3. Background in High-temperature Polymers 233

1 1 .4. Pursuit of Thermally Stable Polymers at LaRC: The Start 237

1 1.5. Composite Matrix Research: Successes and Failures! The Continuation 241

11.5.1 Linear Thermoplastics 242

1 1 .5.2 Lightly Cross-Linked Thermoplastics 257

1 1.5.3 Heavily Cross-linked Thermosets 260

1 1.6. High Speed Research Program: Resins and Composite Development: The

Fulfillment 264

11.6.1 Introduction and Target Properties 264

1 1 .6.2 Initial Candidates and Screening Protocol 266

1 1.6.3 The Early PETI Candidates: LARC™-PETI-1 and LARC™-PETI-2 ....269

1 1 .6.4 The Candidates: LARC™-PETI-4, LARC™-85 1 5, and LARC™-

PETI-5 271

1 1 .6.5 Fabrication Processes for LARC™-PETI-5 281

11.6.6 HSR Adhesives 284

11.6.7 HSR Databases 287

11.7. Adhesives and Other Applications 288

11.8. Polymer Characterization: 1962-1995 290

1 1 .9. Lessons Learned and Future Direction 298

1 1 .9. 1 Lessons Learned 298

1 1 .9.2 Future Activities 299

12. Composite Fabrication Technology 311

12. 1 . Fabrication Technology Timeline and Overview 3 1 1

12.2. Variables in the Fabrication of High-performance Composites 312


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12.3. Liquid Molding or Resin Infusion Processes for Epoxies 313

1 2.4. Placement Methods for Prepregging Continuous Fiber 313

12.5. Out-of-Autoclave Placement Methods: Robotic Dry Tape/Tow Placement 315

12.6. Powder-Coating[34 64] 321

12.7. Powder-coated Textile Forms1-65'721 325

12.8. Ribbonizing[82' 1 02] 327

12.9. E-beam Curing With Automated Tow Placement1403'1051 33 1

12.10. Induction Heating^8'1 141 334

12.11. Cost Factors in ATP 336

12.12. Miscellaneous Processing Techniques 338

12.13. Resin Infusion Processing of Polyimides 339

12.13.1 Background, Tooling, and Resin Requirements 339

12.13.2 Initial Research 342

12.13.3 New HT-VARTM Resins 342

12.14. Fiber Metal Laminates 346

12.15. Lessons Learned and Future Directions 347

13. Nanotechnology 357

13.1. Nanoreinforced Composites 357

13.2. Nanoreinforced Composites 358

13.3. Boron-nitride Nanotechnology - Recent Advancements 367

13.4. Fesson Feamed and Future Direction 369

14. Non-Destructive Inspection 372

14. 1 . Evolution of Non-Destructive Investigation of Composites 372

14.2. NDE Research at NASA Langley 374

14.2. 1 Development of the Nondestructive Evaluation Science Branch 374

14.2.2 LaRC Contributions to Quantitative NDE 375

14.2.3 Recent NDE Programs 381

14.3. Fessons Fearned and Future Directions 383

15. Damage Tolerance 386

15.1. Understanding Damage Tolerance 386

15.2. Damage Tolerance Research at Langley Research Center 389

15.2.1 Effect of Impact on Compression Strength 389

15.2.2 Role of Resin Modulus; Desired Properties 399

15.3. Delamination Mechanics 401

15.4. Progressive Failure Analyses Methodology 407

15.5. Fessons Learned and Future Directions 407

16. Materials and Structural Mechanics 411

16.1. Historical Perspective of Composite Failure Analyses 411

16.2. Multi-scale Modeling 417

16.3. Buckling and Post-buckling Behavior 419

16.4. Lessons Learned and Future Direction 426

17. Structural Analyses 429

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17.1. F inite Element Methods 429

17.2. Tribute to Dr. James H. Starnes, Jr 433

1 7.3. Lessons Learned and Future Direction 434

18. Grand Challenges in High-Performance Composite Materials and Structures

Technology 437

18.1. Certification by Analyses 437

18.2. Materials by Design: Multi-scale Modeling and Measurements 437

18.3. High-fidelity Failure Prediction: Micro and Nanoscopic Mechanisms 438

18.4. Realize Benefits of Nanocomposites: Multifunctional Materials System 440

18.5. Intelligent Materials and Structures: Larger, More Integrated Structure 442

18.6. Pervasive Composites Knowledge and Learning: Isotropic Plasticity

Thinking 443

18.7. Reliability-based Design 445

18.8. Non-autoclave, Low Pressure Material Systems 446

18.9. Research in the “Google” Age 446

19. About The Authors 448

20. Appendix 451

20. 1 . Appendix 1 . Selected Examples of the Productivity of One of the Premier

Branches Doing Composites Research at NASA Langley, The Advanced Materials and Processing Branch (AMPB) 451

20. 1 . 1 Technical References/Publications/Books 45 1

20. 1 .2 Patents and Invention Disclosures 452

20. 1 .3 Industrial Research R&D- 1 00 Awards 453

20.1.4 Commercial Licensed Patents 454

20. 1 .5 Short Courses 454

20. 1 .6 Gordon Research Conferences (GRC) 455

20. 1.7 NASA Commercial Invention of the Year 455

20. 1 .8 Other Miscellaneous Awards, Activities, and Memberships121 455

20.2. Appendix 2. Selected Reviews/Symposia by AMPB Authors on Polymer

Chemistry, Adhesives and Adhesive Properties, Composites and Composite Properties 456

20.2. 1 Polymer Chemistry 456

20.2.2 Adhesives 458

20.2.3 Composites 459

20.2.4 Polymer Characterization 461

20.2.5 Symposia and Workshops on Polymer Chemistry, Adhesives and

Adhesive Properties, Composites and Composite Properties organized by NASA LaRC personnel; NASA and non-NASA presenters 461

20.3. Appendix 3 AMPB Patents and Invention Disclosures 462

20.3.1 Patents (in order by number) 462

20.3.2 Invention Disclosures 471

20.4. Appendix 4 NASA-Virginia Tech Composite Program Students, Research

Topics, and Advisors 475

Structural Framework for Flight



1. Introduction






Vertical Stabilizers





Tank Structure


DC 10 Rudder and Vertical Elevator stabilizer


Shuttle - Cargo Bay Doors

Beech Star Ship

t L 1011 Aileron B737 Hor. Stab.

Honda Jet Composite Fuselage

Material Systems





Application of Composites on Flight Vehicles


1. Fiber-reinforced composites are being used in primary structures of flight vehicles ranging from small unmanned aircraft to space launch vehicles.

2. The percentage of structural weight made from composite materials has grown from less than 1% to more than 50% over the past four decades.

3. Primary drivers for expanded use of composites has been weight reduction, stealth for military aircraft, and cost for commercial aircraft.

4. Composites offer the ability to tailor directional properties and to encompass built-in actuators and sensors for multifunctional structures.

5. NASA has pioneered research and development of composites ranging from synthesis of advanced resins to a fundamental understanding of composite performance in complex service environments.

6. NASA has developed test methods, analyses codes, and structural concepts; and has worked with the FAA to establish the science underpinning for airworthiness certification of aircraft.

Structural Framework for Flight



Composite materials have emerged as the materials of choice for increasing the performance and reducing the weight and cost of military aircraft, general aviation aircraft, transport aircraft, and space launch vehicles. Major advancements have been made in the ability to design, fabricate, and analyze large complex aerospace structures. Many different organizations worldwide have conducted research on composites over the past several decades. In the United States, research on composites has been a combined effort of government laboratories, universities, and industry. The development of high-performance composites for aerospace applications has been spearheaded by the major airframe companies (Boeing, Lockheed, Northrop Grumman, McDonald Douglass (now Boeing), General Dynamics, and others), and by NASA and DOD, with the FAA playing a critical role in the certification requirements for composite flight structures. Within NASA, Langley Research Center had the lead role for development of composites for airframe applications, and NASA Glenn had the lead role for development of high-temperature composites for aircraft engine applications. Development of composites for space structures has been worked by Langley, Glenn, Marshall Space Flight Center, Johnson Space Flight Center, Jet Propulsion Laboratory (JPL), and Goddard Space Flight Center. For space launch vehicles, Marshall, Langley, Glenn, Johnson Space Center (JSC), and Stennis Space Center have all participated in different aspects of the programs. However, in all of these programs, Langley had the lead role in the development of foundational composites technologies required to mature and identify high payoff applications for composites in air vehicle structures. The majority of this foundational technology development work was funded by the aeronautics program because of the demand to reduce both weight and cost of airframe structures for all classes of flight vehicles. The highlights of this research, along with selected examples to illustrate the major accomplishments, are presented in this monograph.

Before discussing the NASA composite projects and the major accomplishments of those projects, a brief synopsis of different uses of composites in the aerospace sector are presented. The examples in the following section are for the purpose of illustrating the many successful applications of composites in commercial aircraft and space launch vehicles that were enabled in part by outstanding research performed by NASA Langley Research Center and its partners. The use of composites, to reduce the weight and cost of commercial aircraft structures and to improve the performance of military aircraft, is a great success story.

Structural Framework for Flight


Success Stories and NASA LaRC’s Role

2. Success Stories and NASA LaRC's Role

2.1. Commercial Transport Aircraft

The recent efforts by Boeing and Airbus to incorporate composites into primary load-carrying structures of large commercial transports and to certify the airworthiness of these structures is evidence of the significant advancements made in the understanding and use of these materials in real world aircraft. The weight fraction of the structure made with composites is 50% for the new Boeing 787 - 100% composite on the “wet” or outer windswept surface. Figure 2.1-1 shows the percent of the structural weight built with composites for commercial transport aircraft.





% 15














in a

A321 0 * * A33




m 777


1 U w

W ill


» A300-600







747-400 4

I MD904



B -7






| ^ IViUOw

1965 1970 1975 1980 1985 1990 1995 2000

Figure 2.1-1: Composites in Commercial Transport Aircraft

The Boeing 787 shown in Figure 2.1-2 is the first full-size commercial aircraft with composite wings and fuselage. The 787 features lighter-weight construction. Its materials (by weight) are: 50% composite, 20% aluminum, 15% titanium, 10% steel, 5% other (Figure 2.1-3).[1] Composite materials are significantly lighter and stronger than traditional aircraft materials, making the 787 a very