Slow cracks, creep, and fatigue in heterogeneous materials

Full description

From a cracked windshield to the collapse of buildings, material failure can poison, degrade, or even devastate our everyday lives. Predicting when and how it will occur is no easy task! Indeed, stress concentration at crack tips makes the macroscopic behaviour of materials highly sensitive to microscopic-scale heterogeneities. Furthermore, the slow dynamics sometimes observed – illustrated, for instance, by the time that may elapse between the initiation of a crack in a windshield and its final failure – further complicate fracture phenomena, making them even more difficult to predict.

These inherently statistical aspects are, by their very nature, at odds with the principle of determinism, a cornerstone of engineering. However, they exhibit certain generic, universal features that have attracted considerable interest within the statistical physics community over the past two decades. In particular, it has been proposed that the fracture of heterogeneous materials can be described in terms of a depinning transition. This paradigm, which has been used to describe a wide variety of phenomena, ranging from the motion of a three-phase contact line (wetting) to that of a magnetic domain wall, explicitly accounts for material heterogeneities and the statistical variability of fracture processes, thereby offering new perspectives for predicting and controlling the associated risks. However, this theoretical framework is, so far, restricted to so-called athermal conditions and cannot describe thermally activated fracture phenomena, such as those encountered in fatigue and creep. A major challenge in this context is to obtain reliable, statistically representative datasets from a well-controlled experimental system, which can then be used to guide and validate theoretical developments.

This is precisely the objective of the internship project proposed here. The first step will be to fabricate a model material with a tunable microstructure, obtained by sintering polymer beads (PMMA and/or polystyrene) under controlled temperature and pressure conditions. The next step will be to perform fracture experiments on these materials while controlling the stress intensity factor, which characterizes the loading applied at the crack tip. Finally, the experimental data will be analysed and interpreted using a model of thermally activated depinning of an elastic manifold in a random potential.

This internship is part of the ANR-funded DISCreep project. Interactions with the various members of the project consortium are expected. The project lies at the interface between experimental mechanics, statistical physics and materials science. The successful candidate will therefore have the opportunity to work with both the theoretical and experimental tools used in these different fields.

Location

France

Internship conditions

• Internship duration: 6 months
• Level of study: Bac+5
• Training: Ingenieur/Master
• Continuation in PhD thesis: No
• Application deadline: 1 mars 2026

Useful methods and technics:
Experimental mechanics, imaging, statistical analysis

Computer languages and software:
Python

Supervisor

Daniel BONAMY
Phone: +33 1 69 08 21 14
Email :

Head of the laboratory SPEC / SPHYNX

Phone: