Slow crack growth : models and experiments

TL;DR

This paper presents a combined theoretical and experimental study of slow crack growth in brittle materials, proposing a thermally activated rupture model and validating it with experiments on paper sheets.

Contribution

It introduces a new model based on thermal noise and stress fluctuations for slow crack growth, supported by experimental validation.

Findings

The model accurately predicts crack growth and rupture times.

Experimental results on paper sheets agree with theoretical predictions.

Stress fluctuations at the microfibril scale trigger rupture events.

Abstract

The properties of slow crack growth in brittle materials are analyzed both theoretically and experimentally. We propose a model based on a thermally activated rupture process. Considering a 2D spring network submitted to an external load and to thermal noise, we show that a preexisting crack in the network may slowly grow because of stress fluctuations. An analytical solution is found for the evolution of the crack length as a function of time, the time to rupture and the statistics of the crack jumps. These theoretical predictions are verified by studying experimentally the subcritical growth of a single crack in thin sheets of paper. A good agreement between the theoretical predictions and the experimental results is found. In particular, our model suggests that the statistical stress fluctuations trigger rupture events at a nanometric scale corresponding to the diameter of cellulose microfibrils.