Epoxy resin fatigue

The early aerospace adhesives were primarily based on epoxy resin chemistry. However, unique applications requiring high temperatures and fatigue resistance have forced the development of epoxy-phenolic, epoxy-nitrile, epoxy-nylon, and epoxy-vinyl adhesives specifically for this industry. The aerospace industry has led in the development and utilization of these epoxy-hybrid adhesives. 

The highest-MW DGEBA epoxy resins are termed phenoxy resins. They are highly linear molecules that are used primarily as thermoplastic coating resins. However, they can be blended with lower-MW epoxy resins for the improvement of specific properties such as flexibility, impact and fatigue resistance, and thermal cycling. Phenoxy resins are sometimes used alone as a thermoplastic hot melt adhesive generally in film form. 

VERs are available as both rigid and flexible epoxy resins. The flexible epoxy resins generally have a depressed glass-transition temperature, Tg, and inferior chemical resistance. Nitrile-rubber-modified VER (I) appeared on the market in the mid- to late 1970s. These elastomer-modified VERs show improved fatigue resistance over unmodified VER (2). 

Yam Yamamoto, I., Higashihara, T., Kobayashi, T. Effect of silica-particle characteristics on impact/usual fatigue properties and evaluation of mechanical characteristics of silica-particle epoxy resins. JSME Intern. J. 46 (2003) 145-153. 

Mays, G.C. Fatigue and Creep Performance of Epoxy Resin Adhesive Joints, To be published in TRRL Contractors Report Series, 1990. 

Figure 17.60 S-N fatigue data for unidirectional cfrp showing the iimited effect of different fibers with the same epoxy resin. Source Reprinted with permission from Curtis PT, RAE Technical Report TR82031, FtAE, Farnborough (now DFIA), 1982, Curtis PT, RAE Technical Report TR86021, RAE, Farnborough, 1986. Copyright 1986, QinetiQ Ltd.

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