fractuurproceszone

A fracture process zone (FPZ) is the region surrounding the tip of a propagating crack in which the material undergoes irreversible deformation and irreversible damage before the crack finally propagates. The FPZ captures phenomena that lie outside the assumptions of ideal linear elastic fracture mechanics, where stresses are considered singular and the material obeys Hookean behaviour up to cracking.

Within the FPZ, localised plastic deformation, microcracking, void nucleation and growth, and other damage mechanisms such as fibre pull‐out in composites or grain crushing in rocks occur. The extent of the FPZ depends on material constitution, loading rate and environmental conditions; it may be micrometre to centimetre scale in engineered materials and several metres in geological formations. The zone can be characterised through acoustic emission, micro‑seismic monitoring, digital image correlation and scanning electron microscopy, enabling measurement of damage density and crack tip velocity.

The size and behaviour of the FPZ are critical to predicting when a crack will accelerate, transition to unstable propagation, or arrest. In engineering, understanding the FPZ informs fracture toughness assessment, structural health monitoring and the design of fracture‑tolerant composites. In geophysics, the FPZ model helps explain the widening of fault cores, the slow nucleation phase of earthquakes, and the variation of seismic‑radiation characteristics. As research progresses, multi‑physics modelling of FPZ behaviour continues to improve the reliability of predictive tools in both materials science and tectonic engineering.