The Experts below are selected from a list of 69 Experts worldwide ranked by ideXlab platform
Dennis P. Roach - One of the best experts on this subject based on the ideXlab platform.
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Development and validation of bonded Composite Doubler repairs for commercial aircraft.
2007Co-Authors: Dennis P. Roach, Kirk A. RackowAbstract:Abstract A typical aircraft can experience over 2000 fatigue cycles (cabin pressurisations) and even greater flight hours in a single year. An unavoidable by-product of aircraft use is that crack, impact and corrosion flaws develop throughout the aircraft's skin and substructure elements. Economic barriers to the purchase of new aircraft have placed even greater demands on efficient and safe repair methods. The use of bonded Composite Doublers offers the airframe manufacturers and aircraft maintenance facilities a cost-effective method to safely extend the lives of their aircraft. Instead of riveting multiple steel or aluminium plates to facilitate an aircraft repair, it is now possible to bond a single Boron-Epoxy Composite Doubler to the damaged structure. The FAA's Airworthiness Assurance Center at Sandia National Labs (AANC), Boeing, and Federal Express completed a pilot programme to validate and introduce Composite Doubler repair technology to the U.S. commercial aircraft industry. This project focused on repair of DC-10 fuselage structure and its primary goal was to demonstrate routine use of this repair technology using niche applications that streamline the design-to-installation process. As Composite Doubler repairs gradually appear in the commercial aircraft arena, successful flight operation data is being accumulated. These commercial aircraft repairs are not only demonstrating the engineering and economic advantages of Composite Doubler technology, but they are also establishing the ability of commercial maintenance depots to safely adopt this repair technique. This report presents the array of engineering activities that were completed in order to make this technology available for widespread commercial aircraft use. Focused laboratory testing was conducted to compliment the field data and to address specific issues regarding damage tolerance and flaw growth in Composite Doubler repairs. Fatigue and strength tests were performed on a simulated wing repair using a substandard design and a flawed installation. In addition, the new sol–gel surface preparation technique was evaluated. Fatigue coupon tests produced sol–gel results that could be compared with a large performance database from conventional, riveted repairs. It was demonstrated that not only can Composite Doublers perform well in severe off-design conditions (low Doubler stiffness and presence of defects in Doubler installation) but that the sol–gel surface preparation technique is easier and quicker to carry out while still producing optimum bonding properties. Nondestructive inspection (NDI) methods were developed so that the potential for disbond and delamination growth could be monitored and crack growth mitigation could be quantified. The NDI methods were validated using full-scale test articles and the FedEx aircraft installations. It was demonstrated that specialised NDI techniques can detect flaws in Composite Doubler installations before they reach critical size. Probability of Detection studies were integrated into the FedEx training in order to quantify the ability of aircraft maintenance depots to properly monitor these repairs. In addition, Boeing Structural Repair and Nondestructive Testing Manuals were modified to include Composite Doubler repair and inspection procedures. This report presents the results from the FedEx Pilot Program that involved installation and surveillance of numerous repairs on operating aircraft. Results from critical NDI evaluations are reported in light of damage tolerance assessments for bonded Composite Doublers. This work has produced significant interest from airlines and aircraft manufacturers. The successful Pilot Program produced flight performance history to establish the durability of bonded Composite patches as a permanent repair on commercial aircraft structures. This report discusses both the laboratory data and Pilot Program results from repair installations on operating aircraft to introduce Composite Doubler repairs into mainstream commercial aircraft use.
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Design and Evaluation of Novel Composite Aircraft Repairs
SAE transactions, 2003Co-Authors: Nikhilesh A. Sheth, Dennis P. RoachAbstract:One of the most common damages occurred found on commercial airframes are dents and gouges. The usual repair for these damages includes installation of metallic Doublers with rivets or with hi-loks. Sometimes these Doublers are of complex design, because of multiple angles of the original damaged skin. Many times the damages are in hard to reach areas. In these cases the traditional metallic Doubler repairs are not only time consuming and but also expensive. As the numerous holes are be drilled through the original structure, its fatigue life is adversely affected. For airline operators, time is valuable and they cannot afford to lose revenue by spending longer time for repairs. The use of bonded Composite Doublers offers the airframe manufacturers and aircraft repair facilities an alternative repair process that alleviates the above-mentioned concerns. Instead of riveting multiple steel or aluminum plates to facilitate an aircraft repair, it is now possible to bond a single Boron-Epoxy Composite Doubler to the damaged structure.
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further evolution of Composite Doubler aircraft repairs through a focus on niche applications
International Conference on Composites in Engineering Denver CO (US) 07 02 2000--07 08 2000, 2000Co-Authors: Dennis P. RoachAbstract:The number of commercial airframes exceeding twenty years of service continues to grow. A typical aircraft can experience over 2,000 fatigue cycles (cabin pressurizations) and even greater flight hours in a single year. An unavoidable by-product of aircraft use is that crack and corrosion flaws develop throughout the aircraft's skin and substructure elements. Economic barriers to the purchase of new aircraft have created an aging aircraft fleet and placed even greater demands on efficient and safe repair methods. The use of bonded Composite Doublers offers the airframe manufacturers and aircraft maintenance facilities a cost effective method to safety extend the lives of their aircraft. Instead of riveting multiple steel or aluminum plates to facilitate an aircraft repair, it is now possible to bond a single Boron-Epoxy Composite Doubler to the damaged structure. The FAA's Airworthiness Assurance Center at Sandia National Labs (AANC) is conducting a program with Boeing and Federal Express to validate and introduce Composite Doubler repair technology to the US commercial aircraft industry. This project focuses on repair of DC-10 structure and builds on the foundation of the successful L-1011 door corner repair that was completed by the AANC, Lockheed-Martin, and Delta Air Lines. The L-1011 Composite Doubler repair was installed in 1997 and has not developed any flaws in over three years of service, As a follow-on effort, this DC-1O repair program investigated design, analysis, performance (durability, flaw containment, reliability), installation, and nondestructive inspection issues. Current activities are demonstrating regular use of Composite Doubler repairs on commercial aircraft. The primary goal of this program is to move the technology into niche applications and to streamline the design-to-installation process. Using the data accumulated to date, the team has designed, analyzed, and developed inspection techniques for an array of Composite Doubler repairs with high-use fuselage skin applications. The general DC-10 repair areas which provide a high payoff to FedEx and which minimize design and installation complexities have been identified as follows: (1) gouges, dents, lightning strike, and impact skin damage, and (2) corrosion grind outs in surface skin. This paper presents the engineering activities that have been completed in order to make this technology available for widespread commercial aircraft use.
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Full-Scale Structural and NDI Validation Tests of Bonded Composite Doublers for Commercial Aircraft Applications
1999Co-Authors: Dennis P. Roach, P WalkingtonAbstract:Composite Doublers, or repair patches, provide an innovative repair technique which can enhance the way aircraft are maintained. Instead of riveting multiple steel or aluminum plates to facilitate an aircraft repair, it is possible to bond a single Boron-Epoxy Composite Doubler to the damaged structure. Most of the concerns surrounding Composite Doubler technology pertain to long-term survivability, especially in the presence of non-optimum installations, and the validation of appropriate inspection procedures. This report focuses on a series of full-scale structural and nondestructive inspection (NDI) tests that were conducted to investigate the performance of Boron-Epoxy Composite Doublers. Full-scale tests were conducted on fuselage panels cut from retired aircraft. These full-scale tests studied stress reductions, crack mitigation, and load transfer capabilities of Composite Doublers using simulated flight conditions of cabin pressure and axial stress. Also, structures which modeled key aspects of aircraft structure repairs were subjected to extreme tension, shear and bending loads to examine the Composite laminate's resistance to disbond and delamination flaws. Several of the structures were loaded to failure in order to determine Doubler design margins. Nondestructive inspections were conducted throughout the test series in order to validate appropriate techniques on actual aircraft structure. The test results showed that a properly designed and installed Composite Doubler is able to enhance fatigue life, transfer load away from damaged structure, and avoid the introduction of new stress risers (i.e. eliminate global reduction in the fatigue life of the structure). Comparisons with test data obtained prior to the Doubler installation revealed that stresses in the parent material can be reduced 30%--60% through the use of the Composite Doubler. Tests to failure demonstrated that the bondline is able to transfer plastic strains into the Doubler and that the parent aluminum skin must experience significant yield strains before any damage to the Doubler will occur.
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development and validation of nondestructive inspection techniques for Composite Doubler repairs on commercial aircraft
Other Information: PBD: May 1998, 1998Co-Authors: Dennis P. Roach, P WalkingtonAbstract:Composite Doublers, or repair patches, provide an innovative repair technique which can enhance the way aircraft are maintained. Instead of riveting multiple steel or aluminum plates to facilitate an aircraft repair, it is possible to bond a single boron-epoxy Composite Doubler to the damaged structure. In order for the use of Composite Doublers to achieve widespread use in the civil aviation industry, it is imperative that methods be developed which can quickly and reliably assess the integrity of the Doubler. In this study, a specific Composite application was chosen on an L-1011 aircraft in order to focus the tasks on application and operation issues. Primary among inspection requirements for these Doublers is the identification of disbonds, between the Composite laminate and aluminum parent material, and delaminations in the Composite laminate. Surveillance of cracks or corrosion in the parent aluminum material beneath the Doubler is also a concern. No single nondestructive inspection (NDI) method can inspect for every flaw type, therefore it is important to be aware of available NDI techniques and to properly address their capabilities and limitations. A series of NDI tests were conducted on laboratory test structures and on full-scale aircraft fuselage sections. Specific challenges, unique to bondedmore » Composite Doubler applications, were highlighted. An array of conventional and advanced NDI techniques were evaluated. Flaw detection sensitivity studies were conducted on applicable eddy current, ultrasonic, X-ray and thermography based devices. The application of these NDI techniques to Composite Doublers and the results from test specimens, which were loaded to provide a changing flaw profile, are presented in this report. It was found that a team of these techniques can identify flaws in Composite Doubler installations well before they reach critical size.« less
Rhys Jones - One of the best experts on this subject based on the ideXlab platform.
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Bonded Composite Repair of Representative Multi-site Damage in a Full-scale Fatigue-test Article
1993Co-Authors: R.a. Bartholomeusz, R. Kaye, J. Roberts, Rhys JonesAbstract:This paper describes an experimental and numerical investigation into the ability of a bonded Composite Doubler to restore the fatigue performance of lap-joints in aircraft skin containing multi-site damage. A series of representative lap-joint specimens were fatigue tested to failure in the first row of rivets in the upper skin. Additional damage was introduced to the lower skin at the third row of rivets. In all cases the repaired specimens survived in excess of 200,000 cycles without failure and with no apparent degradation of the Doubler. Following this study, two Doublers were applied to representative multi-site damage in the lap-joint of a full-scale fatigue-test article. These Doublers will be evaluated over the life of the fatigue test.
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Crack growth and repair of multi-site damage of fuselage lap joints
Engineering Fracture Mechanics, 1993Co-Authors: Loris Molent, Rhys JonesAbstract:Abstract A fatigue test program was conducted to investigate multi-site damage of commerical wide-bodied aircraft fuselage lap joints. Crack growth data were generated using specimens representative of a typical lap joint. It was also demonstrated that a boron/epoxy Composite Doubler, bonded over the joint, could significantly increase the fatigue life of such structures.
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Environmental evaluation of repairs to fuselage lap joints
Composite Structures, 1992Co-Authors: Loris Molent, N. Bridgford, D. Rees, Rhys JonesAbstract:Abstract This paper presents the results of a fatigue test programme undertaken to investigate repairs to multi-site damage in aircraft fuselage lap joints. It is demonstrated that a boron/epoxy Composite Doubler bonded over the joint should significantly increase the fatigue life of the structure and that environmental effects are negligible.
Roberto Lopezanido - One of the best experts on this subject based on the ideXlab platform.
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structural health monitoring of marine Composite structural joints using embedded fiber bragg grating strain sensors
Composite Structures, 2009Co-Authors: Rodrigo Silvamunoz, Roberto LopezanidoAbstract:This paper presents a method for the health monitoring of Composite joints based on strain measurements using distributed embedded fiber Bragg grating (FBG) sensors. Secondary bonded woven E-glass/vinyl ester Composite Doubler plate joints were subjected to fatigue tension loading to induce stable crack propagation. A finite element (FE) model was developed to correlate experimental strain measurements prior to cyclic loading with the numerical predictions and to determine the sensitivity of the sensors to changes in longitudinal strain due to crack growth. Initial quasi-static tension tests demonstrated satisfactory correlation between the strains from the FBG sensors and FE predictions. The changes in longitudinal strain distribution during the fatigue tests were correlated with crack growth. A progressive shift in the strain distribution in the vicinity of the crack was observed. The experimental results demonstrated that a strain-based methodology can be utilized to detect crack propagation in this type of Composite joints.
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monitoring of marine grade Composite Doubler plate joints using embedded fiber optic strain sensors
Journal of Advanced Materials, 2008Co-Authors: Rodrigo Silvamunoz, Roberto LopezanidoAbstract:The objective of this paper was to develop a methodology for the structural health monitoring of Composite joints based on strain measurements using distributed embedded fiber optic strain (FOS) sensors of the fiber Bragg grating (FBG) type. Secondary bonded woven E-glass/vinyl ester Composite Doubler plate joints were subjected to fatigue tension loading. The feasibility of monitoring delamination using embedded sensors was investigated. The fatigue experimental plan, the finite element (FE) modeling of the experiment, and the fabrication methodology of the Composite joints through Vacuum Assisted Resin Transfer Molding (VARTM) processing are presented. Initial quasi-static tension tests showed a good correlation between the longitudinal strain measurement from the FOS sensors and finite element model predictions. The majority of the embedded sensors survived the fatigue loading and provided robust strain measurements. A progressive shift in the strain distribution in the vicinity of the crack was observed in most of the coupons. The experimental results, as well as the numerical study conducted prior to cyclic loading, showed that a strain-based methodology can be utilized to detect crack propagation in this type of Composite joints. The proposed methodology allows detecting a one quarter inch delamination length, which is the criterion adopted by the U.S. Navy for damage tolerance in service conditions.
Rodrigo Silvamunoz - One of the best experts on this subject based on the ideXlab platform.
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structural health monitoring of marine Composite structural joints using embedded fiber bragg grating strain sensors
Composite Structures, 2009Co-Authors: Rodrigo Silvamunoz, Roberto LopezanidoAbstract:This paper presents a method for the health monitoring of Composite joints based on strain measurements using distributed embedded fiber Bragg grating (FBG) sensors. Secondary bonded woven E-glass/vinyl ester Composite Doubler plate joints were subjected to fatigue tension loading to induce stable crack propagation. A finite element (FE) model was developed to correlate experimental strain measurements prior to cyclic loading with the numerical predictions and to determine the sensitivity of the sensors to changes in longitudinal strain due to crack growth. Initial quasi-static tension tests demonstrated satisfactory correlation between the strains from the FBG sensors and FE predictions. The changes in longitudinal strain distribution during the fatigue tests were correlated with crack growth. A progressive shift in the strain distribution in the vicinity of the crack was observed. The experimental results demonstrated that a strain-based methodology can be utilized to detect crack propagation in this type of Composite joints.
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monitoring of marine grade Composite Doubler plate joints using embedded fiber optic strain sensors
Journal of Advanced Materials, 2008Co-Authors: Rodrigo Silvamunoz, Roberto LopezanidoAbstract:The objective of this paper was to develop a methodology for the structural health monitoring of Composite joints based on strain measurements using distributed embedded fiber optic strain (FOS) sensors of the fiber Bragg grating (FBG) type. Secondary bonded woven E-glass/vinyl ester Composite Doubler plate joints were subjected to fatigue tension loading. The feasibility of monitoring delamination using embedded sensors was investigated. The fatigue experimental plan, the finite element (FE) modeling of the experiment, and the fabrication methodology of the Composite joints through Vacuum Assisted Resin Transfer Molding (VARTM) processing are presented. Initial quasi-static tension tests showed a good correlation between the longitudinal strain measurement from the FOS sensors and finite element model predictions. The majority of the embedded sensors survived the fatigue loading and provided robust strain measurements. A progressive shift in the strain distribution in the vicinity of the crack was observed in most of the coupons. The experimental results, as well as the numerical study conducted prior to cyclic loading, showed that a strain-based methodology can be utilized to detect crack propagation in this type of Composite joints. The proposed methodology allows detecting a one quarter inch delamination length, which is the criterion adopted by the U.S. Navy for damage tolerance in service conditions.
D Roach - One of the best experts on this subject based on the ideXlab platform.
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Chapter 35 – Case History: Repair Applications on DC-10/MD-11 Aircraft
Advances in the Bonded Composite Repair of Metallic Aircraft Structure, 2020Co-Authors: D RoachAbstract:Publisher Summary The pilot program installations on FedEx aircraft allowed the FAA Long Beach Aircraft Certification Office to properly direct the use of DC-10/MD-11 commercial aircraft repairs. Six Composite repairs were installed on DC-10/MD-11 aircraft. The repairs are being closely monitored for one year and inspections occurred every D-check thereafter. During the first year of operation, the Doublers are being inspected at 60 day, six month, and one year intervals. A quality assurance inspection was also conducted immediately after each Doubler was installed. In preparation for these aircraft repairs, appropriate installation and nondestructive inspection training was conducted with FedEx's Composite and NDT shops. All aspects of the Composite Doubler fabrication, installation, and quality assurance measures were incorporated into a Federal Express engineering order (EO). The EO generates all job cards needed to build, install, and inspect the repairs at the FedEx maintenance depot. The pilot program and associated manual revisions represent a major milestone in the evolution and application of Composite Doublers. This effort is validating Composite Doublers for a number of high use applications. It is also streamlining the design-to-installation process to make the technology more amenable to wide scale use.
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case history Composite Doubler installation on an l 1011 commercial aircraft
Advances in the Bonded Composite Repair of Metallic Aircraft Structure, 2002Co-Authors: D RoachAbstract:Publisher Summary This chapter presents a series of full-scale structural and nondestructive inspection (NDI) tests that were conducted to investigate the performance of boron-epoxy Composite Doublers under realistic flight conditions. Full-scale tests were conducted on fuselage panels cut from retired aircraft. These full-scale tests studied stress reductions, crack mitigation, and load transfer capabilities of Composite Doublers using simulated flight conditions of cabin pressure and axial stress. Nondestructive inspections were conducted throughout the test series to validate appropriate techniques on actual aircraft structure. The test results showed that a properly designed and installed Composite Doubler is able to enhance fatigue life, transfer load away from damaged structure, and avoid the introduction of new stress risers (i.e., eliminate global reduction in the fatigue life of the structure). Aircraft repair practices must be continuously revisited and expanded to take advantage of new materials, new processes, and new techniques that offer both engineering and economic advantages. Through the steady and comprehensive introduction of test data, analyses, and in-service Composite Doubler installations on commercial aircraft a critical database is being assembled to accurately guide enhancements to formal maintenance programs. This is an important step in the evolution of Composite Doubler applications since it will eventually eliminate the need for each bonded Composite repair to be preceded by a lengthy research and testing program.
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damage tolerance assessment of bonded Composite Doubler repairs for commercial aircraft applications
Advances in the Bonded Composite Repair of Metallic Aircraft Structure, 2002Co-Authors: D RoachAbstract:The Federal Aviation Administration has sponsored a project at its Airworthiness Assurance NDI Validation Center (AANC) to validate the use of bonded Composite Doublers on commercial aircraft. A specific application was chosen in order to provide a proof-of-concept driving force behind this test and analysis project. However, the data stemming from this study serves as a comprehensive evaluation of bonded Composite Doublers for general use. The associated documentation package provides guidance regarding the design, analysis, installation, damage tolerance, and nondestructive inspection of these Doublers. This report describes a series of fatigue and strength tests which were conducted to study the damage tolerance of Boron-Epoxy Composite Doublers. Tension-tension fatigue and ultimate strength tests attempted to grow engineered flaws in coupons with Composite Doublers bonded to aluminum skin. An array of design parameters, including various flaw scenarios, the effects of surface impact, and other off-design conditions, were studied. The structural tests were used to: (1) assess the potential for interply delaminations and disbonds between the aluminum and the laminate, and (2) determine the load transfer and crack mitigation capabilities of Composite Doublers in the presence of severe defects. A series of specimens were subjected to ultimate tension tests in order to determinemore » strength values and failure modes. It was demonstrated that even in the presence of extensive damage in the original structure (cracks, material loss) and in spite of non-optimum installations (adhesive disbonds), the Composite Doubler allowed the structure to survive more than 144,000 cycles of fatigue loading. Installation flaws in the Composite laminate did not propagate over 216,000 fatigue cycles. Furthermore, the added impediments of impact--severe enough to deform the parent aluminum skin--and hot-wet exposure did not effect the Doubler`s performance. Since the tests were conducting using extreme combinations of flaw scenarios (sizes and collocation) and excessive fatigue load spectrums, the performance parameters were arrived at in a conservative manner.« less
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damage tolerance assessment of bonded Composite Doubler repairs for commercial aircraft applications
Other Information: PBD: Aug 1998, 1998Co-Authors: D RoachAbstract:The Federal Aviation Administration has sponsored a project at its Airworthiness Assurance NDI Validation Center (AANC) to validate the use of bonded Composite Doublers on commercial aircraft. A specific application was chosen in order to provide a proof-of-concept driving force behind this test and analysis project. However, the data stemming from this study serves as a comprehensive evaluation of bonded Composite Doublers for general use. The associated documentation package provides guidance regarding the design, analysis, installation, damage tolerance, and nondestructive inspection of these Doublers. This report describes a series of fatigue and strength tests which were conducted to study the damage tolerance of Boron-Epoxy Composite Doublers. Tension-tension fatigue and ultimate strength tests attempted to grow engineered flaws in coupons with Composite Doublers bonded to aluminum skin. An array of design parameters, including various flaw scenarios, the effects of surface impact, and other off-design conditions, were studied. The structural tests were used to: (1) assess the potential for interply delaminations and disbonds between the aluminum and the laminate, and (2) determine the load transfer and crack mitigation capabilities of Composite Doublers in the presence of severe defects. A series of specimens were subjected to ultimate tension tests in order to determine strength values and failure modes. It was demonstrated that even in the presence of extensive damage in the original structure (cracks, material loss) and in spite of non-optimum installations (adhesive disbonds), the Composite Doubler allowed the structure to survive more than 144,000 cycles of fatigue loading. Installation flaws in the Composite laminate did not propagate over 216,000 fatigue cycles. Furthermore, the added impediments of impact--severe enough to deform the parent aluminum skin--and hot-wet exposure did not effect the Doubler`s performance. Since the tests were conducting using extreme combinations of flaw scenarios (sizes and collocation) and excessive fatigue load spectrums, the performance parameters were arrived at in a conservative manner.
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Performance analysis of bonded Composite Doublers on aircraft structures
1995Co-Authors: D RoachAbstract:Researchers contend that Composite repairs (or structural reinforcement Doublers) offer numerous advantages over metallic patches including corrosion resistance, light weight, high strength, elimination of rivets, and time savings in installation. Their use in commercial aviation has been stifled by uncertainties surrounding their application, subsequent inspection and long-term endurance. The process of repairing or reinforcing airplane structures is time consuming and the design is dependent upon an accompanying stress and fatigue analysis. A repair that is too stiff may result in a loss of fatigue life, continued growth of the crack being repaired, and the initiation of a new flaw in the undesirable high stress field around the patch. Uncertainties in load spectrums used to design repairs exacerbates these problems as does the use of rivets to apply conventional Doublers. Many of these repair or structural reinforcement difficulties can be addressed through the use of Composite Doublers. Primary among unknown entities are the effects of non-optimum installations and the certification of adequate inspection procedures. This paper presents on overview of a program intended to introduce Composite Doubler technology to the US commercial aircraft fleet. In this project, a specific Composite application has been chosen on an L-1011 aircraft in order to focus the tasks on application and operation issues. Through the use of laboratory test structures and flight demonstrations on an in-service L-1011 airplane, this study is investigating Composite Doubler design, fabrication, installation, structural integrity, and non-destructive evaluation. In addition to providing an overview of the L-1011 project, this paper focuses on a series of fatigue and strength tests which have been conducted in order to study the damage tolerance of Composite Doublers. Test results to-date are presented.