• Physique/Mécanique/Mécanique des solides
  
• Physique/Matière Condensée/Mécanique statistique
  
• Physique/Physique
  
• Chimie/ou physique
  
• Physique/Mécanique/Mécanique des matériaux
  
• Sciences de l'ingénieur/Mécanique/Mécanique des matériaux
  
• Sciences de l'ingénieur/Mécanique/Mécanique des solides
  
• Physique/Matière Condensée/Science des matériaux
  
• Physique/Mécanique/Matériaux et structures en mécanique
  
• Sciences de l'ingénieur/Matériaux
  
• Sciences de l'ingénieur/Mécanique/Génie mécanique
  
• Sciences de l'ingénieur/Mécanique/Mécanique des fluides
  

We present a simulation method to assess the quasistatic fracture resistance of materials. Set within a semi-grand-canonical Monte Carlo (SGCMC) simulation environment, an auxiliary field—the bond rupture potential—is introduced to generate a sufficiently large number of possible microstates in the semi-grand-canonical ensemble, and associated energy and bond fluctuations. The SGCMC approach permits identifying the full phase diagram of brittle fracture for harmonic and nonharmonic bond potentials, analogous to the gas-liquid phase diagram, with the equivalent of a liquidus line ending in a critical point. The phase diagram delineates a solid phase, a fractured phase, and a gas phase, and provides clear evidence of a first-order phase transition intrinsic to fracture. Moreover, energy and bond fluctuations generated with the SGCMC approach permit determination of the maximum energy dissipation associated with bond rupture, and hence of the fracture resistance of a widespread range of materials that can be described by bond potentials.

Using a 3D mean-field lattice-gas model, we analyze the effect of confinement on the nature of capillary phase transition in granular aggregates with varying disorder and their inverse porous structures obtained by interchanging particles and pores. Surprisingly, the confinement effects are found to be much less pronounced in granular aggregates as opposed to porous structures. We show that this discrepancy can be understood in terms of the surface-surface correlation length with a connected path through the fluid domain, suggesting that this length captures the true degree of confinement. We also find that the liquid-gas phase transition in these porous materials is of second order nature near capillary critical temperature, which is shown to represent a true critical temperature, i.e., independent of the degree of disorder and the nature of the solid matrix, discrete or continuous. The critical exponents estimated here from finite-size scaling analysis suggest that this transition belongs to the 3D random field Ising model universality class as hypothesized by F. Brochard and P.G. de Gennes, with the underlying random fields induced by local disorder in fluid-solid interactions.

During cement hydration, C–S–H nanoparticles precipitate and form a porous and heterogeneous gel that glues together the hardened product. C–S–H nucleation and growth are driven by dissolution of the cement grains, posing the question of how cement grain surfaces induce spatial heterogeneities in the formation of C–S–H and affect the overall microstructure of the final gel. We develop a model to examine the link between these spatial gradients in C–S–H density and the time-evolving effective interactions between the nanoparticles. Using a combination of molecular dynamics and Monte Carlo simulations, we generate the 3D microstructure of the C–S–H gel. The gel network is analyzed in terms of percolation, internal stresses, and anisotropy, and we find that all of these are affected by the heterogeneous C–S–H growth. Further analysis of the pore structure encompassed by the C–S–H networks shows that the pore size distributions and the tortuosity of the pore space show spatial gradients and anisotropy induced by the cement grain surfaces. Specific features in the effective interactions that emerge during hydration are, however, observed to limit the anisotropies in the structure. Finally, the scattering intensity and specific surface area are computed from the simulations in order to connect to the experimental methods of probing the cement microstructure.

The aggregation of colloidal clay mineral particles plays an important role in controlling the mechanical and transport properties of soils. Interactions and aggregation of plate-like montmorillonite particles were previously studied with the help of Molecular Dynamics (MD) simulation. This paper investigates the aggregation of cylindrical imogolite-like phyllosilicate nanotubes. Nano-scale MD simulations are carried out to find the potential of mean force between two nanotubes. This PMF is then used in a mesoscale simulation that represents interactions between elemental nanotubes through coarse-graining. We investigate the distribution of water molecules around the curved surfaces, and the effects of the surface charge density and tube length on aggregation. Shorter nanotubes were found to form larger stacks.

Capillary effects, such as imbibition drying cycles, impact the mechanics of granular systems over time. A multiscale poromechanics framework was applied to cement paste, which is the most common building material, experiencing broad humidity variations over the lifetime of infrastructure. First, the liquid density distribution at intermediate to high relative humidity is obtained using a lattice gas density functional method together with a realistic nanogranular model of cement hydrates. The calculated adsorption/desorption isotherms and pore size distributions are discussed and compare well with nitrogen and water experiments. The standard method for pore size distribution determination from desorption data is evaluated. Second, the integration of the Korteweg liquid stress field around each cement hydrate particle provided the capillary forces at the nanoscale. The cement mesoscale structure was relaxed under the action of the capillary forces. Local irreversible deformations of the cement nanograins assembly were identified due to liquid–solid interactions. The spatial correlations of the nonaffine displacements extend to a few tens of nanometers. Third, the Love–Weber method provided the homogenized liquid stress at the micrometer scale. The homogenization length coincided with the spatial correlation length of nonaffine displacements. Our results on the solid response to capillary stress field suggest that the micrometer-scale texture is not affected by mild drying, while nanoscale irreversible deformations still occur. These results pave the way for understanding capillary phenomena-induced stresses in heterogeneous porous media ranging from construction materials to hydrogels and living systems.