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Some highly-filled energetic materials exhibit a concrete-like
microstructure, and behave accordingly. Under moderate (quasi-static or
dynamic) confining pressures, their tendency towards strain localization is
inhibited. During deformation, micro-cracking occurs in the largest grains, and
frictional sliding induces an apparent elasto-plastic behavior. In the dynamic
case, this process also produces strong local heating that may lead to ignition.
The present work aims at modeling this two-fold phenomenology by proposing a
thermodynamics-based multi-scale approach. The macroscopic material is seen
as a statistical distribution of unit cells containing a (cracked) grain embedded in
an elastic mortar-like matrix. A (mesoscopic) unit cell model is first developed
under confined shear. Owing to the high volume fraction of filler, care must be
taken in the meso to macro transition, i.e., the assembling process.
The resulting model captures the essential trends of the mechanical behavior of
the materials under consideration. Its thermodynamic ingredients allow for the
derivation of the dissipated power and the heat flux on sliding crack lips, thus
providing a useful tool towards predicting ignition.