Please find the early work of Prof. Zhigang Suo in Harvard University

I assume (but I am not sure) you are referring to materials which contain nanoparticles, like polymers where nanomaterials are incorporated into in order to modify the polymer properties. If so, then you first want to understand how the nanoparticles interact with the (polymer) matrrix and what kind of structures are built, here is 1 example:

https://www.researchgate.net/publication/229816762_Electrical_conductivity_in_heterogeneous_polymer_systems._V_%281%29_Further_experimental_evidence_for_a_phase_transition_at_the_critical_volume_concentration

Here I described a model for the brittle-to-tough transitio in polymer systems:

https://www.researchgate.net/publication/229762491_Nonequilibrium_thermodynamical_description_of_heterogeneous_polymer_systems_%28viii%29_New_concept_for_understanding_brittletotough_transition_in_polymer_blends?ev=srch_pub&_sg=iLWiOqeQsNHe7H6o0lXGz7De72txtDbPdrxfaDRQNDS4L%2BPIurld17OhxsucPYqt_oQeh0F5mvCYzeiY1%2FYBkQlrcVSBGTIkq%2FOd%2B1beqHF7jfW97RkPnCgCGfHtgKy0G_aNYMJU1VghOt8WLaEnVcaOrxrKRDTdxD9y8VEyh7TzIqTXmESnJZDlrS8o%2F%2BgBIa

Article Electrical conductivity in heterogeneous polymer systems. V ...

Article Non‐equilibrium thermodynamical description of heterogeneous...

Cracks are dependent of porous content and the forces involved due to the smallest size. I suggest that you study the papers of Wander L. Wasconcelos of Federal Universit of Minas Gerais for more if your study was about silica gels.

Crack growth rate is largely controlled by how sharp the crack tip is, due to stress concentration near the tip.  When a crack tip hits a nano-particle, the radius of the crack tip can become much larger, thus reducing the stress concentration and slowing (or stopping) the crack growth.  This is especially true if the nano-particle is not too strongly tied to its matrix.  For references, I'd start with a search on crack propagation or fracture mechanics.