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In order to design machinery such as extruders, pelletizers, cubers and briquetters used to compact biological materials such as fibrous agricultural residues, it is necessary to have some knowledge about the mechanical behavior of such materials at all stages of their process. These materials posses mechanical properties which are dependent on the applied stress and strain, strain rate, humidity content, temperature, amongst other parameters. In this study two models were used to explore the behavior of these materials, namely, the Maxwell model and the crushable foam model.

The first analysis was performed considering a piecewise linear viscoelastic behavior and to determine the model parameters. A comparison with experimental results showed differences of the order of 3.5 % for both axial and transverse stresses.

On the other hand, the crushable foam model which uses the concept of a yield surface which is dependent on the dilatational deformation. Comparison of the crushable foam model with experimental results for axial stresses have differences of the order of 1%, but it overestimates the lateral stresses for relative densities lower than 1.0 for a 50% approximately.