Activation Energy Approach to Creep Rupture

The creep behavior of many materials including most metals and thermoplastic polymers is often described as given in Fig. 11.18 and contains 

Taking logarithms of both sides and converting to base 10 logarithms gives. 

The Larson-Miller and other similar methods have been widely used for metals but here it is important to note that difficulties arise for fiber reinforced composite laminates because the constants are only valid for one configuration of the plies and a more general approach is needed. Dillard (1981) developed an incremental viscoelastic time dependent lamination theory approach that included the Tsai-Hill failure law modified to account for delayed failures using the Zhurkov time dependent failure model that will be discussed in the next section. The advantage of the Dillard approach is that information on the viscoelastic behavior as well as the delayed failure behavior of 0°, 10° and 90° plies can be used to predict the behavior of general laminate configurations. 

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