Paper number 571


John A. Nairn and Man-Hee Ha

Materials Science and Engineering, University of Uta
122 Central Campus Dr Rm 304, Salt Lake City, UT, 84121-0560, US

Summary Two polyimide-matrix systems were subjected to a series of hygrothermal aging experiments at various temperatures and relative humidities. For each aging condition, we measured the microcracking fracture toughness as a function of aging time. The toughness decreased with time. The rate of decrease increased with temperature and relative humidity. All experimental results could be fit to a simple fiist-order kinetics analysis where the degradation rate was assumed to be proportional to the, total exposure to water above a threshold level below which no degradation occurs. The kinetics analysis was used to construct a hygrothermal aging master plot that can be used to make predictions of toughness degradation due to arbitrary hygrothermal environments. The master plot can be constructed from a few experiments on specimens immersed in water and thus is a potential accelerated test method for characterizing hygrothermal stahility
Keywords Microcracking, hygrothermal aging. durability. environmental effects, hydrolysis, accelerated test methods, polyimide matrix, fracture toughnes

Theme : Mechanical and Physical Properties ; Damage Mechanics

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