Micromechanics-based estimates on the macroscopic fracture toughness of micro-particulate composites

•We upscale the global fracture properties of multi-scale materials.•The local morphology and elasticity govern the macroscopic fracture behavior.•Our theory is validated on microparticulate polymer composites and porous ceramics.•Scratch tests provide a powerful means to assess the fracture toughness.

We investigate the macroscopic fracture toughness of multi-phase materials within the framework of fracture mechanics and micromechanics. Starting with the Eshelby inclusion problem, we provide estimates on the critical energy release. We take into account the elastic and fracture properties of the micro-constituents, the microstructure and the phase volume fractions by considering three schemes: dilute, Mori–Tanaka and generalized self-consistent. In turn, the theoretical model is validated by scratch tests experiments conducted on glass-reinforced polymer composites. We also apply our theoretical framework to porous clay-based ceramics. In both cases, the agreement between experiments and theory is excellent.