Browsing > By author > Braux Chloé

Predicting subcritical rupture of heterogeneous materials is an important subject in physics of ma-
terials. Subcritical rupture happens when a material is loaded at a constant force below its ultimate
tensile strength for a long time. This process ends with the ultimate failure that defines the lifetime of
the sample, τc. The lifetime is a scattered and hard to predict parameter. If we stop maintaining the
target force before the final rupture, we observe a relaxation of the force in the sample. This relaxation
can be fitted using a visco-elastic rheological model [1] which predicts a logarithmic decay of the force
with a characteristic time τ . The aim of our experiment is to measure the evolution of the relaxation
time, τ , during the subcritical rupture process. For this purpose, we use paper samples held in a tensile
stress apparatus controlling elongation and we impose a constant force with a feedback loop. In addition
to this constant force, we apply tiny force steps to probe the relaxation locally. The time between two
steps is proportional to the characteristic relaxation time. Experimentally, for paper samples, we observe
that this time τ increases linearly, indicating a slowing down in the subcritical rupture dynamics, then
fastly decreases at about 80% of the lifetime τc[2]. This behavior can be qualitatively explained by the
fiber bundle model [3] that describes the phenomenological rupture of a heterogeneous fibrous material.
Considering the strain of our sample, we recover behaviors already observed in other soft materials such
as protein gels [4]. When a constant force is applied, the strain rate first decreases with a power law then
increases sharply before the final rupture.
References
[1] Arthur Tobolsky and Henry Eyring. “Mechanical Properties of Polymeric Materials”. In: Journal
of Chemical Physics 11.3 (Mar. 1943), pp. 125–134.
[2] Juha Koivisto et al. “Predicting sample lifetimes in creep fracture of heterogeneous materials”. In:
Physical Review E 94.2 (Aug. 8, 2016), p. 023002.
[3] Jérôme Weiss and David Amitrano. “Logarithmic versus Andrade's transient creep: Role of elas-
tic stress redistribution”. In: Physical Review Materials 7.3 (Mar. 13, 2023). Publisher: American
Physical Society, p. 033601.
[4] Mathieu Leocmach et al. “Creep and Fracture of a Protein Gel under Stress”. In: Physical Review
Letters 113.3 (July 15, 2014). Publisher: American Physical Society, p. 038303.