Effect of disorder on the failure of frictional interfaces – DisRuptInt

The onset of sliding of a frictional interface is due to a propagating rupture front, which breaks the contacts resisting to shear. The rupture is a brittle shear crack driven by singular fields and propagating within an effectively homogeneous medium. Indeed, a frictional interface is intrinsically disordered, from the micro-contacts to the macroscopic scale, e.g. seismic faults. But the interface discreteness is hidden in the dissipative zone surrounding the rupture tip. An elusive question is how the failure mechanisms are affected by disorder when the interfacial structures become too large to be averaged by the propagating rupture.
Our goal is to develop a comprehensive description of friction based on fracture mechanics for any type of interface. We want to study the effect of interfacial disorder (roughness, composite material, foreign particles) on the rupture dynamics. Experimentally, we will consider an interface made of successive homogeneous and disordered sections to disentangle rupture nucleation and propagation processes. Strain measurements near the interface, optical measurements of the real area of contact and particle tracking at the interface will be performed.
We will first establish the limit of validity of brittle fracture mechanics to describe friction. Beyond validity, we will characterize the failure modes, based on fracture models of heterogeneous solids. We want to find a signature of the interface composition in the dynamic elastic fields surrounding the rupture tip. We will then understand the mechanisms giving rise to the shear resistance of a macroscopic system. Frictional resistance is determined by the shear stress at which a rupture nucleates. Disordered interface sections will be used to control rupture nucleation.
This project aims at providing new insights into the physics of frictional processes, but not only. We want to show that friction provides a versatile platform for studying fracture of heterogeneous materials and mechanical singularities. Beyond physics, solid friction is a challenge for earthquake mechanics, from the seismic faults characterization to the fault monitoring strategy. To control the frictional properties of solid systems is also a technological challenge. We are currently developing national and international collaborations with experimentalists, theoreticians and geodesists. The ANR support would greatly strengthen our joint efforts and bring our consortium at the forefront of the friction science.