Brittle-to-ductile fracturing transition: A chemo-mechanical phase-field framework

TL;DR

This paper introduces a chemo-mechanical phase-field model to study how chemical reactions influence fracture behavior in geomaterials, revealing a transition from brittle to ductile failure modes driven by chemical and mechanical timescales.

Contribution

The study develops a novel coupled chemo-mechanical phase-field framework that captures the interplay between mineral dissolution and fracture propagation, highlighting the brittle-ductile transition.

Findings

Chemical dissolution enlarges fracture process zones and blunts crack tips.

Ductile failure occurs when chemical degradation timescales dominate mechanical loading.

Acidic environments promote ductile fracture, while rapid loading favors brittle failure.

Abstract

In chemically reactive environments, the mechanical integrity of geomaterials is fundamentally compromised by solid matrix dissolution. In this study, we propose a fully coupled chemo-mechanical phase-field framework to capture the dynamic interplay between mineral dissolution and fracture propagation. A key feature of the proposed model is the dynamic coupling of local mass removal to the fracture length scale, while also incorporating the damage-accelerated reaction-diffusion processes. Our results capture the development of an enlarged fracture process zone driven by chemical mass removal. This chemically induced widening blunts the sharp crack tip, alleviating the near-tip stress concentrations and causing a pronounced degradation in material stiffness before failure. Furthermore, we reveal a distinct ductilization effect, characterized by a more gradual accumulation of damage and a delayed onset of macroscopic failure. We show that the transition between brittle and ductile failure modes is dictated by the competing timescales of chemical degradation and mechanical deformation. Highly acidic environments enhance matrix dissolution and promote ductile fracture, whereas rapid mechanical loading limits chemical interaction and preserves brittle failure mode.