Aerospace structures adhesives

In the following sections/ we shall discuss adhesion chemistry/ adhesion physics / radiation-curable adhesiveS/ high-temperature adhesiveS/ anaerobic and structural adhesiveS/ hot-melt adhesives/ film adhesiyes/ waterborne adhesives/ aerospace structural adhesiveS/ conventional sealants/ advanced aerospace sealants/ and adhesives and sealants for solar collectors. 

The properties of several typical high-temperature adhesives are listed in Table 2 (59). Note that one listed is PM-34 condensation polyimide from the Bloomingdale Division of American Cyanamid Company. The contributions of the above high-temperature adhesives to the aerospace structural adhesives will be discussed later. 

The increasing amount of research in waterborne systems should some day overcome technological difficulties. Howeverr the change-over from some solvent-borne to waterborne systems has presented difficulties (107), for exampler poor coating quality, excessive foam, insufficient water resistance, and even some corrosion and clean-up problems. Despite the problems, some waterborne systems have already been adopted for the manufacture of PSA s, contact adhesives, laminating adhesives, and wood adhesives. However, few applications of the waterborne systems as structural adhesives, especially as aerospace structural adhesives have been found. 

A special study on aerospace structural adhesives was conducted in 1976 by the National Materials Advisory Board of the National Research Council. The final report was published as one of the series in Treatise on Adhesion and Adhesives (108). That report discussed primarily phenolic and epoxy-based mate rials, e.g., vinyl-phenolics, n itr ile-phenolics, epoxy-phenolics, nylon-epoxies, and elastomer-epoxies. Polyimide and polybenzamidazole adhesives were barely mentioned. Most of the high-temperature adhesives discussed in one of the preceding sections were either not invented or not developed at that time. 

McDonnell Aircraft Company, "Acceptance Criteria for Aerospace Structural Adhesives," AFML-TR-78-53, Final Report, 5/1978. 

A series of nitrile-phenolics, e.g., J-01, J-02, J-03, J-04, J-15, JX-9, JX-10, KH-506, were developed for aerospace structural adhesives (19). In addition, an epoxy-phenolic, J-44-1 (20) was supplied to adhere polyimide (Nomex) film to honeycomb structures. Thus, their structural adhesive line appears to be quite complete. 

David A. Wangsness obtained his B.A. in Chemistry from Luther College in Iowa in 1961 and attended graduate school at the University of North Dakota in 1962. He joined 3M in 1962 as a Chemist and worked on the development of aerospace structural adhesives. Presently, he is Manager of the Aerospace Products Laboratory at 3M. 

The performance of the classifier has been verified using a number of practical applications, such as civil engineering [3], inspection of aerospace composite structures, ball bearings and aircraft multi-layer structures. Here we present shortly some results, focusing on detection of disbonds in adhesively joint multi-layer aerospace structures using Fokker Bond Tester resonance instrument, details can be found in [1]. 

Allbericci, P, Aerospace applications. In Kinlock, A.J. (Ed.), Durability of Structural Adhesives. Applied Science Publishers, London, 1983, Ch. 8. 

The aerospace field is a broad one and has a complex history. A comprehensive review of structural adhesive applications on currently flying aerospace vehicles alone could fill its own book. Hence this chapter will concentrate on the aerospace commercial transport industry and its use of adhesives in structural applications, both metallic and composite. Both primary structure, that is structure which carries primary flight loads and failure of which could result in loss of vehicle, and secondary structure will be considered. Structural adhesives use and practice in the military aircraft and launch vehicle/spacecraft fields as well as non-structural adhesives used on commercial aircraft will be touched on briefly as well. 

National Materials Advisory Board, National Research Council, Structural Adhesives with Emphasis on Aerospace Applications. Marcel Dekker, Inc., New York, 1976. 

Following this initial period of polyimide development, interest reached a steady-state and remained there until the late 1970s. During this time a major impetus to the polyimide area was provided by the aerospace industry. The need for composite matrix resins as well as structural adhesives with excellent oxidative and thermal stability appeared to be at least partially met by polyimide type resins. Ultimately, requirements of high flow and low void content in relatively thick parts directed these efforts into different directions. Another upswing occurred in the early 1980s with the potential application of... 

Epoxy adhesives have become the most recognizable structural adhesive type. They have found commercial success in demanding industries such as aerospace, automotive, building and construction, and electrical and electronic. Their ease of use has also encouraged their commercialization in the do-it-yourself markets, which has added to the exemplary reputation of epoxy adhesives. 

Aircraft and Aerospace. Adhesives have always played a significant role in the aircraft and aerospace industries primarily because they offer a low-weight, fatigue-resistant, and aerodynamically sound method of assembly. Adhesive bonding is also less labor- and costintensive when applied to large structures such as those commonly utilized in the aerospace industry. Structural adhesives account for the greatest market share of all the adhesives used in aerospace applications. 

In the aerospace market a distinction is made between primary and secondary structural applications. Joint failure in a primary structure will result in the loss of the aircraft, whereas failure in a secondary structure will result in only localized damage. Structural adhesives are used in both applications. Figure 1.4 illustrates the degree to which adhesive bonding is used in modem aircraft. 

Boeing Company, Seattle, WA also in Politi, R. E., Structural Adhesives in the Aerospace Industry, Handbook of Adhesives, 3d ed., I. Skiest (ed.), van Nostrand Reinhold Publishing, New York, 1990. 

Savia, Epoxy Resin Adhesives, and Politi, Structural Adhesives in the Aerospace Industry. ... 

One of the most popular uses of radiant curing is the advancement (viscosity increase) or crosslinking of pressure-sensitive adhesives. These applications have been satisfied mostly with acrylate-based adhesive systems. With epoxy-based adhesives, the main applications are electrical and electronic components, the bonding of large aerospace structures such as composites, and the bonding of transparent substrates such as glass and plastic. 

Epoxy structural adhesives are used in an extraordinarily wide range of applications. They are available in essentially all of the forms discussed above, except for primer—liquid combinations or as room temperature curing liquids. The liighest technology7 application for epoxies is in aerospace structural... 

Phenolic resins are the oldest form of synthetic structural adhesives. Usage ranges from bonding automobile and other types of brake linings to aerospace applications. These adhesives have a reputation for providing the most durable structural bonds to aluminum. Because of volatiles, however, and the need for high pressures, the phenolic resins are used less as adhesives than the epoxy resins. 

Major polymer applications aerospace, electronics (mostly films and coatings), photosensitive materials for positive imaging, solar cells, hollow fiber membranes, composites. unclear power plants, space shuttle, microprocessor chip carriers, structural adhesives... 

Highly cross-linked epoxy resins combine high strength stiffness thermal, chemical, and environmental stability adhesion low weight processability excellent creep resistance and favorable economics. These resins are widely applied as coatings, casting resins, structural adhesives, and matrix resins of advanced composite materials. The broad spectrum of applications ranges from the automotive and aerospace industries to corrosion protection and microelectronics. 

Thermosets are often used in intimate contact with materials of much lower coefficient of linear thermal expansion p. A thermoset film may be coated on a surface, or sandwiched between two surfaces as an adhesive. A thermoset matrix may be filled with high-modulus fibers in aerospace structural materials and in other composite materials. A residual stress other material(s) to changes in temperature. The value of or typically reflects the balance between the driving force to produce residual stresses due to differential shrinkage upon cooling and the temperature-dependent capacity to relax these stresses. The worst such effects... 

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