Models for granular or polymer behavior

The behavior of granular and polymeric materials is complex. However, under essentially monotonic loading conditions rather simple constitutive models provide useful design information. These constitutive models are essentially pressure-dependent plasticity models that have historically been popular in the geotechnical engineering field. However, more recently they have also been found to be useful for the modeling of some polymeric and composite materials that exhibit significantly different yield behavior in tension and compression.

The following topics are discussed:

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Extended Drucker-Prager models


The models described here are extensions of the original Drucker-Prager model (Drucker and Prager, 1952). In the context of geotechnical materials the extensions of interest include the use of curved yield surfaces in the meridional plane, the use of noncircular yield surfaces in the deviatoric stress plane, and the use of nonassociated flow laws. In the context of polymeric and composite materials, the extensions of interest are mainly the use of nonassociated flow laws and the inclusion of rate-dependent effects. In both contexts the models have been extended to include creep.