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Title: Performance analysis of bonded composite doublers on aircraft structures

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 tomore » 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.« less
Authors:
Publication Date:
OSTI Identifier:
95298
Report Number(s):
SAND--95-1886C; CONF-950833--4
ON: DE95016737; CNN: Contract DTFA-03-91-A-0018
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: 10. international conference on composite materials, Vancouver (Canada), 14-18 Aug 1995; Other Information: PBD: [1995]
Research Org:
Sandia National Labs., Albuquerque, NM (United States)
Sponsoring Org:
USDOE, Washington, DC (United States);Federal Aviation Administration, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; 36 MATERIALS SCIENCE; COMPOSITE MATERIALS; MATERIALS TESTING; AIRCRAFT COMPONENTS; REPAIR; AIRCRAFT; CRACKS; REINFORCED MATERIALS; BORON; EPOXIDES; STRESS ANALYSIS; CRACK PROPAGATION; ALUMINIUM