Slow Crack Propagation in Heterogeneous Materials

TL;DR

This paper presents a theoretical study of crack nucleation and slow propagation in heterogeneous materials with defects, revealing mechanisms for crack arrest and increased fracture toughness.

Contribution

It introduces a generalized Griffith criterion-based model that accounts for thermal noise, dissipation, and defect-induced forces affecting crack dynamics.

Findings

Defects cause long-range interactions leading to crack arrest.

Heterogeneous materials contain many microcracks that are arrested.

Fracture toughness is significantly enhanced in such materials.

Abstract

Statistics and thermally activated dynamics of crack nucleation and propagation in a two-dimensional heterogeneous material containing quenched randomly distributed defects are studied theoretically. Using the generalized Griffith criterion we derive the equation of motion for the crack tip position accounting for dissipation, thermal noise and the random forces arising from the defects. We find that aggregations of defects generating long-range interaction forces (e.g., clouds of dislocations) lead to anomalously slow creep of the crack tip or even to its complete arrest. We demonstrate that heterogeneous materials with frozen defects contain a large number of arrested microcracks and that their fracture toughness is enhanced to the experimentally accessible time scales.