Composite Chronicles: a Study of the Lessons Learned in the Development, Production, and Service of Composite Structures
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NASA Contractor Report 4620 Composite Chronicles: A Study of the Lessons Learned in the Development, Production, and Service of Composite Structures Louis F. Vosteen Analytical Services & Materials, Inc. • Hampton, Virginia Richard N. Hadcock RNH Associates • Huntington, New York National Aeronautics and Space Administration Prepared for Langley Research Center Langley Research Center • Hampton, Virginia 23681-0001 under Contract NAS1-19317 November 1994 This publication is available from the following sources: NASA Center for AeroSpace Information National Technical Information Service (NTIS) 800 Elkridge Landing Road 5285 Port Royal Road Linthicum Heights, MD 21090-2934 Springfield, VA 22161-2171 (301) 621-0390 (703) 487-4650 TABLE OF CONTEN_I'S Section Title Page Section Title Page Introduction Quality Control 23 General 23 Organizational Issues 2 Nondestructive Inspection 23 Organizational Barriers 2 Effects of Defects 23 Organizational Needs 2 Lessons Learned 23 Technology Transfer 3 Lessons Learned 4 Supportability 24 General 24 Structural Design, Analysis, and Test 5 In-Service Damage & Repair 24 Design and Certification Requirements 5 Lessons Learned 25 Structural Design 7 Structural Analysis 11 Conclusions and Recommendations 25 Structural Test 11 Cost Considerations in Design 12 Appendix 27 Design R&D Needs 13 Lessons Learned 14 Military Aircraft 27 Commercial Transport Aircraft 35 Materials & Processes 15 General Aviation 40 Materials 15 Remotely Piloted Research Vehicles and Processes 16 Drones 43 Joints and Attachments 17 Helicopter Applications 44 Lessons Learned 17 Observations and Conclusions 48 Manufacturing and Tooling 18 References 51 Manufacturing 18 Tooling 20 Acknowledgments 54 Lessons Learned 22 LIST OF FIGURES Figure Number Title Page 1. Organization of structures Design Build Team. 3 2. Current FAA damage tolerance design requirements. 8 3. Revised damage tolerance requirements. 8 4. Example of process description from shop manual. 18 LIST OF TABLES Table Number Title Page 1. Civil aircraft in use by US military and the certificating country and agency. 6 2. Examples of moldform tooling used on some past and current programs. 21 m-1. Composite components on military aircraft. (a) 1960-1979 29 (b) 1980-1995 30 36 m-2. Composite components on commercial transport aircraft. A-3. Boeing composite component suppliers. 37 A-4. Airbus composite component suppliers. 38 A_5. Composite components on business aircraft. 39 A-6. Composite components on private, trainer, competition, RPV, and drone aircraft. 42 A-7. Composite components on Helicopters. 45 iii COMPOSITE CHRONICLES: A STUDY OF THE LESSONS LEARNED IN THE DEVELOPMENT, PRODUCTION, AND SERVICE OF COMPOSITE STRUCTURES Louis F. Vosteen Analytical Services & Materials, Inc. and Richard N. Hadcock RNH Associates INTRODUCTION The major issues today are associated with the materials, manufacturing, and repair costs and not with structural performance. The The development of advanced fiber structural problems and failures that have composites in the 1960's brought aircraft occurred were primarily caused by deficien- designers a new material option comparable to cies in the detail design of joints, cut-outs, and the introduction of aluminum some 40 years discontinuities, designs that did not make earlier. Carbon fibers, with moduli and proper allowance for the lack of ductility and strengths comparable to steel and a density anisotropic mechanical properties of the half that of aluminum, created visions of 50% composite materials. Other problems were weight saving for airframe structure. Although associated with communications between such weight savings have been achieved on a engineering and manufacturing personnel, few specific components, the added weight especially when the people and facilities were associated with load introduction, the need to located hundreds of miles apart. In most satisfy multiple design conditions, design and instances, design changes corrected the struc- producibility requirements that usually require tural problems and most companies are now a balance of in-plane properties, accessibility using the "Concurrent Engineering" approach for maintenance, inspection, and damage with collocated design-production teams to repair, and production cost constraints have improve communications. made weight savings of 15-30% a more realis- tic and achievable goal. Given the problems and failures that have occurred, and are still occurring, one As typically happens with the introduc- must ask whether the problems experienced tion of new technologies, advanced fiber are similar and inherent in the nature of ad- composites have had their share of difficulties vanced composites or whether new problems along with many notable successes. A few continually arise because of lack of technical programs involving utilization of composites understanding of the materials and their have experienced unforeseen problems and behavior. Furthermore, when programs are premature failures during development testing. successful, is there an underlying reason that Many more have been very successful, have should be recognized, understood, and applied provided significant weight savings, and in the future? service experience has been excellent. Thou- sands of safety-of-flight components are in In an effort to find answers to these production and are providing excellent service questions, NASA Langley Research Center on more than forty different US and foreign contracted with Analytical Services and military and civil fixed-wing aircraft and Materials to conduct a study of past composite twenty different helicopters. Most of these aircraft structures programs and determine the composite components, as well as components lessons learned during the course of those on technology development and demonstrator programs. The study was focused on finding aircraft, are identified in the Appendix to this major underlying principles and practices that report. experience showed could have a significant effecton thedevelopmentprocessandshould saving potential of composites. Twenty years berecognizedandunderstoodby thoserespon- later, there are still some senior corporate siblefor makingeffectiveuseof composites executives and engineers who feel that com- for aircraftstructures.Publishedinformation posites have no place in airframes. A senior on programswasreviewedandinterviews government representative suggested that top wereconductedwith personnelassociatedwith management education in composites is more currentandpastmajordevelopmentprograms. necessary now than ever. Management should In all, interviewswereconductedwith about understand that problems invariably arise in 56peoplerepresenting32organizations.Most composites structures programs, but these of thepeopleinterviewedhavebeeninvolved problems have generally been resolved satis- in theengineeringandmanufacturingdevelop- factorily. mentof compositesfor thepasttwentyto twenty-fiveyears.Severalof thepeople interviewedwereretiredfrom prominent ORGANIZATIONAL NEEDS positionsin governmentandindustry.Their insightsandreminiscencesof lessonslearned, "Concurrent Engineering", whereby a andsometimesforgotten,areinvaluable. new product or system is developed jointly and concurrently by a team composed of designers, stress analysts, materials and pro- ORGANIZATIONAL ISSUES cesses, manufacturing, quality control, and support engineers, as well as cost estimators, has generally become the accepted approach to The various organizational issues, needs improve the quality and performance and and barriers associated with transfer of com- reduce the development and production costs posites technology were discussed at many of of complex systems. the meetings. There was general agreement about the needs, but some differences of Most of the aerospace companies have opinion about barriers, some of which are implemented concurrent engineering ap- dependent on company organization and vary proaches in one form or another. Boeing, for from company to company. example, has formed "Design Build Teams" (DBTs) for development of the Boeing 777. The DBT hierarchy for a typical major struc- ORGANIZATIONAL BARRIERS tural component is shown in Figure 1. The Boeing structures teams are composed of ten When advanced composite materials first to twenty people from the various engineering, became available during the late 1960's, and manufacturing, quality control, and cost when the Air Force, Navy and NASA began to estimating departments. Where necessary, fund the first advanced composites develop- teams also include people from Boeing pro- ment programs, there was considerable lack of curement and from subcontractors and suppli- support and skepticism of the projected ben- ers. The teams, each of which are collocated, efits and usefulness of composites for aircraft are responsible for producing a final design, structures by industry. cost estimates, production planning, etc. of the structural components-and subcomponents. All The companies which were most suc- drawings and interfaces with other teams and cessful had a few senior corporate executives subcontractors are made using the Boeing who became champions for composites. These computer network. companies assigned some of their most ca- pable people to composites development Lockheed, GD, Northrop, Vought and programs and set up teams to work with and other companies have all implemented similar respond to the Government's initiatives. Even systems for new programs. The Grumman though significant advances