Search Results for designing for repairability

This article discusses the requirements for designing repairable composite structures such as a honeycomb sandwich panel construction and integrally stiffened co-cured composite structures. It reviews the general and specific design guidelines for bolted or riveted repairs and adhesively bonded repairs of the composite structures. The article presents several examples to illustrate how these repairs can be achieved.

This article discusses three typical repair types for composite structures: temporary repairs, adhesively bonded repairs, and bolted repairs. It contains a table that lists general design requirements and considerations for the repair of composite structures. The article describes ten steps for an engineering repair approach to effectively restore structural integrity to damaged composite components. Management, validation and certification of repairs are also discussed. The article presents the design guidelines for analyzing the damage and possible strategies for making a repair. It reviews three repair schemes used in repair design analysis, namely, core replacement, adhesively bonded patch, and mechanically fastened patch. The article also emphasizes the various pitfalls and problems in repair design for composite structures.

This article describes the types of repair and presents reasons for avoiding damage to a structure or component during repair. It discusses the major standardization issues with emphasis on design, repair materials, repair techniques, and inspection.

This article provides a summary of the concepts discussed in the articles under the Section “Product Reliability, Maintainability, and Repair” in ASM Handbook, Volume 21: Composites. The Section covers a range of topics that include the general issues for reliability, maintenance, and repair of composite structures. Specific structural applications, including marine, infrastructure, and aircraft related issues, are discussed. Operators of equipment employing composite structures in primary load applications must understand the issues with respect to maintenance and repair action. The Section also provides information on these requirements.

This article begins with an overview of the various types of damage that take place in advanced composite components. These include holes and punctures, delaminations, disbonds, core and resin damage, and water intrusion. The article describes various damage detection techniques, such as visual inspection, tap testing, and ultrasonic inspection, in field conditions. Designing for repair involves various considerations including structure types and repair types. The types of repairs together with other issues surrounding advanced composite repair technology are discussed. The article also provides a discussion on the design considerations, instructions, and materials for repair. It explains various paint-removal methods for composites. The article concludes with a discussion on curing equipment such as portable repair systems, vacuum bags, and ovens and autoclaves.

Relatively limited effort has gone into developing repair processes and materials for composites, in contrast to the significant labor and expense that has gone into the development of these materials for numerous critical applications. As composites gain wider acceptance as aerospace materials, there is a need to understand the requirements of the end users regarding repair of these advanced materials. This article focuses on the repair of graphite-epoxy structures designed in a variety of forms for a wide range of load intensities. Five repair concepts developed for generic laminate repair have been validated in this article through the required environmental and load condition tests. These include bonded-scarf joint flush repair, double-scarf joint flush repair, blind-side banded-scarf repair, blind-side sandwich repair, and bonded external patch repair. A brief note on thermoplastic repair concepts is also provided in this article.

Maintainability is a function of the durability, damage tolerance, and repairability of a structure. This article discusses the configurations of composite structures, such as sandwich, stiffened-skin, and monolithic structures, used in commercial aircraft composites. It describes the considerations for maintainability of the composite structures during the conceptual design phase. Sources of the defects and damage, such as manufacturing defects and in-service defects, are reviewed. The article describes the nondestructive inspection methods that are used in the repair of composite structures to locate damage, characterize the extent of damage, and ensure post-repair quality. It lists suggestions that can be used as design guidelines for adhesive bonding, general composite structure, sandwich structure, material selection, and lightning-strike protection. The article also provides the basic considerations for personnel, facilities, and equipment during maintenance.

Composite bonded repair technology is based on the use of advanced composite repairs or reinforcements that are adhesively bonded to a damaged structure. This article discusses the key steps that are normally encountered in the design, certification, and application of an adhesively bonded repair. Some examples of successful repairs to military aircraft are also discussed.

It is recommended that repairs be made whenever damage consists of delamination cracks or broken fibers. This article provides an overview of the repair classification, characterization, and cycle of the composite ship structure. The methods outlined in this article, which covers gel coat repairs, patching, scarfing, and step repairs, have undergone extensive development and rigorous testing for use on composite ship structures. Resin infusion repair, which is a relatively new method for repairing marine composites, is also described.

This article provides non-proprietary and non-competition-sensitive information related to aircraft applications. It presents an overview of reliability and commonly used measurements. Failure modes that cause the negative performance are reviewed based on many types of sources. These include manufacturer service bulletins, reliability and customer service departments, literature reviews, demonstration programs, in-service evaluations, design guides, and surveys of commercial and military aircraft maintenance organizations. The article also describes lessons learned while attempting to avoid overlapping maintainability, reparability, and materials choice.

This article provides a discussion on the design, in-process, storage, and in-field problems and their considerations associated with armament corrosion with examples. Design considerations include geometry, material selection, assembly, pretreatment, coatings, and working and storage environments. In-process corrosion concerns include processing locations, in-process storage of parts, time between processing steps, and quality control of each processing step. The article also discusses the analysis of the in-field corrosion of the finished product, including physical environments, repair of corrosion-protective coatings, general corrosion-protection maintenance, and appropriate fixes and procedures that can be implemented by soldiers in-field to stop continued corrosion of armament equipment.

Fracture control is a systematic process to prevent fracture during operation that depends on the criticality of the component, the economic consequences of the structures being out of service, and the damage that would be caused by a fracture failure. This article describes the key principles of fracture control and reviews the concepts of damage tolerance analysis. It further presents practical guidelines to obtain useful and reasonable answers from damage tolerance analysis. The article concludes with information on fracture mechanics and fatigue design.

This article describes the commonly observed forms of airplane corrosion, namely: general corrosion, exfoliation corrosion, pitting corrosion, microbiologically induced corrosion, galvanic corrosion, filiform corrosion, crevice corrosion, stress-corrosion cracking, and fretting. It discusses the factors influencing airplane corrosion from the manufacturing perspective: design, manufacturing, and service-related factors. The article explains the collection of corrosion data and provides an overview of the implementation and evolution of airline corrosion prevention and control programs and directions being considered in the design for corrosion prevention of airplanes.

Composites, particularly fiber-reinforced polymer materials, are increasingly being adopted or considered as alternatives to conventional materials for civil infrastructure applications, such as bridges, buildings, waterfront structures, waste treatment facilities, and facilities for transmission and transport of utilities. This article provides information on seismic retrofit applications and discusses the repair and strengthening of components, such as beams, slabs, large-diameter pipes, and bridge decks.

The combination of high strength-to-weight ratio, excellent mechanical properties, and corrosion resistance makes titanium the best material choice for many critical applications. This article commences with a description of the historical perspective of titanium casting technology. It discusses the various types of molding methods, namely, rammed graphite molding, and lost-wax investment molding. The article provides information on the casting design, melting, and pouring practices, and describes the microstructure, hot isostatic pressing, heat treatment, and mechanical properties of Ti-6AI-4V alloy. It also talks about the chemical milling and weld repair, and describes the product applications of titanium alloy castings. Tensile properties, standard industry specifications, and chemical compositions of various titanium alloy castings are tabulated.

This article begins with discussion on forgeability and the factors affecting the forgeability of aluminum and aluminum alloys. It describes the types of forging methods and equipment and reviews critical elements in the overall aluminum forging process: die materials, die design, and die manufacture. The article discusses the critical aspects of various manufacturing elements of aluminum alloy forging, including the preparation of the forging stock, preheating stock, die heating, lubrication, trimming, forming and repair, cleaning, heat treatment, and inspection. It concludes with a discussion on the forging of advanced aluminum materials and aluminum alloy precision forgings.

Titanium alloys are forged into a variety of shapes and types of forgings, with a broad range of final part forging design criteria based on the intended end-product application. This article begins with a discussion on the classes of titanium alloys, their forgeability, and factors affecting forgeability. It describes the forging techniques, equipment, and common processing elements associated with titanium alloy forging. The processing elements include the preparation of forging stock, preheating of the stock, die heating, lubrication, forging process, trimming and repair, cleaning, heat treatment, and inspection. The article presents a discussion on titanium alloy precision forgings and concludes with information on the forging of advanced titanium materials and titanium aluminides.

Joining is key to the manufacture of large or complex devices or assemblies; construction of large and complex structures; and repair of parts, assemblies, or structures in service. This article describes the three forces for joining: physical, chemical, and mechanical. It provides an overview of the joining processes, namely, mechanical fastening, integral attachment, adhesive bonding, welding, brazing, and soldering. The article concludes with information on the various aspects of joint design and location that determine the selection of a suitable joining method.

Electron beam welding (EBW) can produce deep, narrow, and almost parallel-sided welds with low total heat input and relatively narrow heat-affected zones in a wide variety of common and exotic metals. This article focuses on essential parameters of EBW, namely, weld and surface geometry, part configuration, melt-zone configuration, weld atmosphere (vacuum and nonvacuum), and joint design. It describes various aspects considered in EBW of thin and thick metal sections and poorly accessible joints. An overview of scanning and joint tracking techniques for inspection of electron beam-welded joints is also included. The article concludes with discussions on EBW defects, the use of filler metal for weld repair, and the control plans, codes, and specifications of the EBW process.

This article describes some examples of the different welding processes for gray, ductile, and malleable irons. These processes include fusion welding, repair welding, shielded metal arc welding, gas metal arc welding, flux cored arc welding, gas tungsten arc welding, submerged arc welding, oxyfuel welding, and braze welding. The article discusses various special techniques, such as groove-face grooving, studding, joint design modifications, and peening, for improving the strength of a weld or its fitness for service. The article describes other fusion welding methods such as electrical resistance welding and thermite welding. It reviews thermal spraying processes, such as flame spraying, arc spraying, and plasma spraying, of a cast iron.