Interaction law and solution procedure

A local/global interaction relation must be imposed to relate the average mechanical behavior of each composite inclusion to the macroscopically imposed boundary conditions. The collective plastic deformation of aggregates, such as grains in a polycrystalline assembly, has been the subject of many studies on the crystal 

The idealization of the two coupled crystalline and amorphous components of HDPE as joined sandwich elements and their interactive plastic deformation by crystal plasticity and amorphous flow comes close to the assumptions of the Sachs model of interaction. Thus, the composite model employing a Sachs-type interaction law does indeed result in quite satisfactory predictions both for the stress-strain curve and for the texture development in plane-strain compression flow and even in other modes of deformation (Lee et al. 1993b). In the following sections we discuss the application of the composite model to plane-strain compression flow and compare the findings of the model with results from corresponding experiments. 

For the common strain-rate-sensitivity exponent, the value of n = 9 comes close to representing the behavior of both phases at 295 K, according to the measurements of G Sell and Dahoun (private communication in 1993). A typical level of crystallinity of commercial HDPE is 0.7, giving/ = 0.3. 

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