COMPOSITES

Composites Science and Technology 65 (2005) 2295–2299

SCIENCE ANDTECHNOLOGY

www.elsevier.com/locate/compscitech

Three decades of composites activities at US Air ForceMaterials Laboratory

Stephen W. Tsai *

Department of Aeronautics and Astronautics, Stanford University, Durand Building, Stanford 943054035, USA

Received 10 May 2005; accepted 10 May 2005Available online 2 September 2005

Abstract

In the decades of 1960s–1980s, Air Force Materials Laboratory pioneered many programs and training of personnel that led tomajor advances in the understanding and utilization of composite materials and structures. The early involvement of industryresulted in rapid identification of the advantages and technical hurdles to be overcome. Through extensive use of postdoctoralappointments, ROTC at universities, visiting and exchange scientists, the Laboratory was able to reach many talented young peoplewho in the years following have assumed leadership in teaching and research of composite materials worldwide. A recount of theactivities during these three decades is timely because most of the ‘‘young’’ men and women who had spent time at the Laboratorywill be ready to retire in the next few years.� 2005 Published by Elsevier Ltd.

Keywords: Composite materials and structures

1. Advanced composites

Project Forecast was an exercise conducted underGeneral Bernard Shriver, Commander of US Air ForceSystems Command at the beginning of 1960s. It was in-tended to assess the potential impact of boron fiber andits composite materials. Having a stiffness twice that ofsteel, the unidirectional composite would have a stiffnesshigher than steel but only 1/4 of the weight. Thatprompted a famous claim that building made with suchmaterial could be five times taller, and bridge span, fivetimes longer. Although this forecast has not come true,it did launch composite materials for serious aerospaceapplications. While glass has phenomenal strength itsstiffness is not sufficiently high to be used for load-carry-ing aircraft structures. Thus a new class of composites,dubbed advanced composites, based on boron fiber

0266-3538/$ - see front matter � 2005 Published by Elsevier Ltd.

doi:10.1016/j.compscitech.2005.05.017

* Tel.: +1 650 725 3305; fax: +1 650 725 3377.E-mail address: steve.tsai@mac.com.

and subsequently carbon fibers has been under intensivedevelopment ever since. Critical decades of the 1960sthrough the 1980s were the times when advanced com-posites emerged. The single most successful class ofcomposites from the standpoint of general acceptanceis carbon/epoxy composites. Many other compositeswere also pursued but have failed to achieve the promi-nence of CFRP.

The Air Force advanced development program oncomposites was conceived and implemented by AlanM. Lovelace, then the Chief Scientist and later theDirector of AF Materials Laboratory, near Dayton,Ohio, and his point person George Peterson, head ofthe advanced composites division. A deliberate decisionwas made to induce industrial participation in the begin-ning state of this new technology. Then viable infra-structure within each company in support of thistechnology could be developed concurrently rather thansequentially. Early pioneers from industry includedCharlie Roger of General Dynamics/Fort Worth, SamDastin of Grumman, and others at North American,

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Northrop, and McDonnell–Douglas for airframe, andPratt and Whitney and General Electric for aircraftengines. These industrial projects started in the mid1960s. The first demonstration was the F-111 horizontalstabilizer by General Dynamics. By the mid 1970s com-posite components for production began to appear inthe horizontal stabilizer of F-14, F-16 and F-15.NASA/Langley later joined the AF and started promot-ing the use of composites for commercial airplanes. AlLovelace later became NASA administrator and, afterretirement from government, was president of GeneralDynamics commercial launch service, and is now retiredliving in Florida. George Peterson retired from the AirForce and lives near Dayton, Ohio. Charlie Rogers re-tired and so did Sam Dastin. Charlie lives in Fort Wortharea and Sam in Las Vegas.

2. Mechanics of composites

Robert T. Schwartz was the head of nonmetallicmaterials at AFML that spearheaded in-house researchin fibers, matrices and their composites. He initiatedmicromechanics and many related in-house and contrac-tual programs. In 1966, Jim Whitney was a textile engi-neer trying to develop the first micromechanics analysis.He was later assisted by another newly hired, freshlyminted Ph.D from Drexel Nick Pagano. A contract pro-gram of the nonmetallic division with MIT had a grad-uate student Su Su Wang that performed mechanicsanalysis and testing of composites. Su Su later headedcomposites centers at the University of Illinois and isnow at the University of Houston.

In the years following, Jim earned his doctorate fromOhio State University and did a solution of unsymmet-ric laminates. Subsequently, he and a General Dynamicsengineer, Jim Ashton, coauthored a book on anisotropicplates. Among many of his accomplishments, he startedthe American Society for Composites in the 1970s. Jimretired from the Air Force and now teaches at the Uni-versity of Dayton.

In the mean time, Nick teamed up with another Gen-eral Dynamics engineer, Byron Pipes, and wrote a pio-neering paper on delamination of composites.Hundreds of papers have appeared since and, as of thisdate, delamination remains a favorite topic of manyresearchers. Nick is now retired and lives in Columbus.Byron moved from General Dynamics to Drexel Uni-versity to the University of Delaware (where he formedthe Composites Center) to RPI (as its president), theUniversity of Akron and now with Purdue University.

Through the years the mechanics tradition continuesat nonmetallic division of the Lab. The torch is beingcarried by Steven Donaldson, a Purdue graduate withsubsequent Ph.D from Stanford. He is assisted by AjitRoy, a Ph.D from the University of Minnesota, who

served as post doc with the Lab before eventually join-ing it. It has long been recognized that composite mate-rials and structures can be most effectively optimized bymechanics principles. They strive for realistic modelingof deformation and failure to supplement and reduceempiricism.

3. Young officers

AFMaterials Lab is often chosen by Reserve Officer�sTraining Corps (ROTC) graduates from universities.Among the successful ones include Al Lovelace andGeorge Peterson, mentioned earlier. Since the adventof advanced composites, several officers have madeimportant contributions. One was Robert Rapson whostarted working for George Peterson in his advancedcomposites division. Bob progressed in his career withthe Lab and is now the head of nonmetallic materials,headed by R.T. Schwartz when advanced compositeswas conceived.

John Halpin began his research in anisotropic behav-ior using rubber specimens. His experimental demon-stration of the shear coupling effect earned him adoctorate from the University of Akron. He also startedthe Halpin–Tsai equation and later was a proponent of awear out model to characterize composites durability.

Other officers include Larry Drzal who came to theLab with a doctoral degree from Case Western Reserve.He set up a surface science lab when he came in the early1970s. His pioneering work in interfacial strength ofcomposites and bonded joints has been well documentedand recognized. He left the AF Lab and started withMichigan State University where he still is a professorof chemical engineering. In recent years, Larry has ex-panded his composites research to include natural fibers.

Another officer, Karen Knoll, came from MIT. Shedesigned a Read Only Memory module for a hand heldcomputer (Texas Instrument TI-59). She was also instru-mental in writing operating instructions for classicallaminated plate theory and quadratic failure criteria. Itwas an exceptionally user-friendly tool by the standardof the late 1970s, an era before personal computers.After Materials Lab, Karen worked for industry inHouston and later in Florida.

Jocelyn Patterson was another MIT graduate thathelped the Lab to promote simplified design methodol-ogy of composites. She later went to Stanford and re-ceived her Ph.D and did her research in thermal/curing warping of composite components. She nowworks for Owens-Corning in Granville, Ohio.

Jerry Flanagan also came to the lab from MIT. Heworked with exchange scientists Dietmar Wurtzle fromthe German Aeronautics and Space Institute (DFVLR)in Stuttgart and Thierry Massard from the French Com-mission of Atomic Energy (CEA) in getting design

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methodology of composites on some earliest models ofpersonal computers in the early 1980s. Jerry left thelab and started working for Grumman for several yearsbefore he joined Material Sciences Corporation. One ofhis recent contributions is to manage Mil Handbook 17for the Department of Defense. Dietmar still works forDLR (a more recent name for DFVLR), and Thierry isone of the top managers at CEA.

Russ Kurtz joined the Lab from Purdue and went onto Pentagon and later became the commander of thehigh speed test track in New Mexico.

4. NRC Post doctorate program

The US National Research Council had an active postdoctorate and senior program with AF and NASA labo-ratories. Many young and senior Ph.D�s spent time at AFMaterials Laboratory. One of the earliest ones was H.Thomas Hahn, a Penn State graduate, in 1970. Heworked with Steve Tsai and coauthored their first book:Introduction to Composite Materials. Tom left the laband joint Livermore National Lab in late 1970s and thenwent on to Washington University, Penn State Universityand now with UCLA. He is active in a variety of researchtopics in composite materials behavior and manufactur-ing processes. He also took over as editor-in-chief of Jour-nal of Composite Materials from Steve Tsai.

Jonathan Awerbuch was a Technion graduate. Hedid ballistic penetration and acoustic emission. Subse-quently he joined Drexel University and is still there.Jack Weitsman was a senior post doc. He covered manytopics related to composites with special emphasis onnonlinear behavior of composites under loads and sub-jected to moisture absorption. He is now with the Uni-versity of Tennessee.

Ralph Nuismer was a Ph.D from the University ofUtah. He and Jim Whitney did the Nuismer–Whitneycriteria for stress concentration at the edge of an openhole. The average stress and point stress criteria appliedto the open hole stress concentration are still in use.

Michael Hyer of the University of Michigan spenttime at AF Materials Lab and has covered the behaviorof unsymmetric laminates more thoroughly than almostanyone in the world. He is now with Virginia Tech.

Ippei Susuki came to the lab to study, among manytopics related to metals and composites, failure criteriaand laminate optimization. Several years later he re-turned to the Lab for another summer visit. In Japan,he worked for Japan Aerospace Laboratory (ARL, re-cently renamed JAXA) where he built a combined stresstester from the ground up and made significant contri-bution in measuring composite laminates and highstrength metals subjected to combined stresses. Recentlyhe was in charge of the safety of launching the Japaneserocket. It was a successful launch.

Other notable post docs include Som Soni whostarted AdTech after he left Materials Lab. He didextensive graphical representation of failure criteria.As mentioned earlier, Ajit Roy came from the Univer-sity of Minnesota and worked on linear and nonlinearbehavior of composites. He is now a permanent memberof the Lab. Seng Tan was another post doc and solved awide variety of problems. He now heads a small com-pany named Wright Materials Research. Peter Sjoblomwas a graduate form the Technical Institute of Linkop-ing in Sweden and was involved in many compositesprograms including design software. He later joinedthe University of Dayton Research Institute and was amajor contributor to the determination of bird strikeresistance of gas turbine fan blades.

Prof. K.P. Rao from Indian Institute of Science inBangalore was a senior post doc. He contributed tothe study of waffle plates and developed a simplified de-sign program. He returned to Bangalore and has re-cently retired. He is now a consultant at Infosys inBangalore working on Boeing 787 and Airbus 380 pro-jects. Prof. T.S. Ramamurthy was another senior postdoc from the same institute and also retired. He didwork on bolted joints. N. Balasubramanian did failuretheory and retired from Everest Eternitt Company inBangalore. Prof. H.V. Lakshminarayana was involvedin fracture mechanics of composite structures, and hasnow retired from M.S. Ramaiah Institute of AdvancedStudies. All these outstanding people came from Banga-lore, more than 20 years before it became famous in theUS for its software and out-sourced service centers.

5. University of Dayton Research Institute

In-house research of AFML depended heavily on theclose working relation with the professional staff andtechnicians of UDRI. On top of the list of the profes-sional staff is Ran Kim who since the early 1970 hadbuilt a world-class testing facility. He provided continu-ity and upheld the technical integrity among governmentpersonnel, visiting and exchange scientists and postdocsthrough the years.

Other equally famous alumni of this group includedC. S. Hong, who later became the president of the KoreaAdvanced Institute of Science and Technology (KAIST)and is now serving as a legislator in the Korean govern-ment (National Assembly). Georges Verchery was also avisiting scientist. After his stay with the Lab, he held sev-eral teaching positions in France and was also the Sci-ence Attache of the French Embassy in Tokyo. WonJ. Park of Wright State University also participated ac-tively in simplified design of composites. He is now pro-fessor emeritus.

Antonio Miravete from Zaragoza, Spain, came as anewly wed. He did the laminate optimization and pre-

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sented stunning graphical representation of ply drops.He has been professor at the University of Zaragozafor nearly 20 years. Antonio chaired ICCM/9 in Madridin 1993. Norbert Himmel, also a newly wed, did three-dimensional elasticity solution for his doctoral thesis.He is now working for Institute of Composite Materials,in Kaiserslautern in Germany.

The Lab was also benefited by having several stu-dents during summer vacation from Purdue and theUniversity of Michigan. Steve Wanthal was one ofthem. After having received his Ph.D from Purdue un-der Prof. Henry Yang, he started his work with McDon-nell–Douglas in St. Louis and is now in charge of theirComposites Affordability Initiative.

6. Exchange scientists

There were a number of exchange scientists workingin composite materials at the Materials Lab. Jan Erik-son from the Swedish defense research institute (FOA)spent many months working with Tom Hahn on the fa-tigue of composites. Thierry Massard from Francehelped in introducing personal computers for compos-ites design. He and Jerry Flanagan worked tirelesslyin programming many tools including an automatedlaminate optimization. Our division chief at the timewas upset by how much time Thierry and Jerry sat infront of monitors. He had no idea that the majorityof the workforce today, including students and facultyat colleges and universities, are spending more time infront of computer monitors or screens than any otheractivity. Thierry and Jerry were just 20 years ahead oftime.

Thierry returned to France and steadily moved on themanagement chain of the Commission on Atomic En-ergy of France. He also ran International Conferenceon Composite Materials in Paris (ICCM/12) in 1999.

There were three exchange scientists from the Ger-man Research Institute of Space and Aeronautics(DFVLR) in Stuttgart. Rodolfo Aoki was the first oneand was instrumental in testing and evaluation of com-posites; Dietmar Wurzel was interested in novel designof composites; and Christopher Kindervater was intocrash worthiness of composite structures with specialemphasis on helicopters. All three are still employedby the successor of organization called German Aero-nautics Research (DLR). Rodolfo and Chris remain inStuttgard, while Dietmar is in Brussels as DLR repre-sentative at European Community.

7. Famous sponsored programs

Two very important sponsored programs during the1970s and 1980s were performed by George Springer

at the University of Michigan and later at StanfordUniversity.

The first was the moisture absorption and its impacton properties of composites. He not only set this area ofresearch on a solid foundation in his innovative treat-ment of the boundary conditions of a diffusion processbut also provided data to validate the analytic predic-tions. For the last 30 years, research on the moisture ef-fect has assumed a life of its own. It refuses to die.Nearly all subsequent efforts were variations of George�sinitial effort.

Another equally important program was the curemodeling of composites. This too was done by George.Up till then (and to some extent it still is) curing was re-garded as an art, purely empirical. George was able tosystematically model the processes of heating, consolida-tion, void migration and residual stress upon cooling.Once the processes were modeled, optimization becamestraightforward. He later extended the work to includethermoplastic, microwave cure, and ‘‘smart cure’’ by ex-pert system. Among many of his students, Al Loos andWoo Il Lee are still active in the field. Al is now a profes-sor at Michigan State University after having stayed atVirginia Tech for many years. Woo Il Lee is a professorof mechanical engineering at Seoul National University.

8. Workshops

Many of us were involved in many workshops pro-moting the use of composites. Dozens were held in theUS, nine European and six Far Eastern countries. Manypeople who were connected with AFML in variouscapacities were contributors to these workshops.

The longest lasting one was at the University of Cal-ifornia, Berkeley, where 17 workshops were held over aspan of 20 some years. The attendance varied from 40 to140. Hundreds of students participated in this series.Many recall the instructions, software practice sessions,wine tasting and Chinese dinners.

Another few workshops were sponsored by SAMPE.In 1989, it was attended by over 300 and the year afterwas over 400. It did not take a rocket scientist to figureout that there was a lot of money to be harvested. SoSAMPE decided to have more than one workshop. Inthe years that followed, there are 10 workshops pre-sented each year.

9. Reflection

It was clear that AFML through its programs andpersonnel put advanced composites on their way to suc-cess. Many applications of composites for military andcommercial aircraft can be traced to the investmentmade by the Lab. While other agencies and companies

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around the world all made their marks, AFML stoodout as a source of ideas and experts. It is amazing howmany of their people are still active in composites, mostof them in universities around the world. While GeneralShriver�s prediction of tall building and long bridgespans might not be precisely right, the foresight andimplementation by Lovelace, Peterson and Schwartzmade a difference. For all the engineers who have passedthrough AFML, we appreciate their contributions andlasting commitment to stay with this technology. Their

students and colleagues will no doubt carry the torchto see composites reach another plateau.

Acknowledgement

This writing is written based on memory. When peo-ple and activities are cited, omissions would be unavoid-able. Please accept apologies for my less-than-perfectmemory.