Published: Jan 1993
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Tapered double cantilever beam specimens produced from two sheet molding compounds (SMC) with different glass contents were subjected to static loading in an environment of 1 M hydrochloric acid (HCl). The nature of the resulting crack growth was observed and the rate of crack growth was measured as a function of applied stress intensity, KI. Both direct visual observation of the crack length and indirect crack length estimations via compliance measurements were used to follow the failure of the specimen. It was discovered that slow crack growth occurs, producing an irregular and diffuse crack, until the total cracked area ahead of the original notch exceeds a distance equal to a characteristic length that is constant for each SMC. This cracked length may be determined in separate fracture mechanics testing of the materials in the absence of the environment. Once the critical crack length is achieved, the rate of crack growth increases. Both the time to achieve the critical cracked length and the subsequent rate of crack growth are functions of the applied stress intensity, KI.
sheet molding compound, SMC, stress corrosion, characteristic dimension, crack growth, fracture toughness, environmental effects
Research student, Scientific Studies and Research Center, Allepo,
Senior lecturer, Queen Mary and Westfield College, University of London, London,