Stick-slip dynamics in an interleaved system with self-amplified friction

TL;DR

This study investigates how complex assemblies with multiple contact surfaces exhibit stick-slip dynamics, revealing how normal compression and internal stress distribution influence force peaks and system stiffness.

Contribution

It presents the first systematic analysis of stick-slip behavior in a multi-contact system with friction amplification, linking force measurements to internal stress distribution and effective stiffness.

Findings

Peak force and amplitude decrease with detachment velocity.

Normal compression influences the effective stiffness of the system.

Spatial distribution of forces affects the mechanical response.

Abstract

Understanding how stick-slip dynamics manifests in diverse physical conditions is a crucial topic in tribology. Although it has been extensively studied in simple frictional configurations, the characterization of stick-slip behavior in complex assemblies is challenging. This work presents the first systematic investigation of stick-slip dynamics in a system with multiple contact surfaces undergoing friction amplification through conversion of traction forces into normal compression. Using interleaved paper blocks as a model system, we combine force measurements and image processing to characterize stick-slip events occurring when the two blocks are pulled apart at different detachment velocities. We find that both the peak force and the amplitude of the stick-slip events decrease along with the system's detachment. By combining a previously designed model for friction amplification and the stick-slip dynamics predicted by a simple frictional spring-block system, we link the observed behavior to the evolving normal compression within the assembly. Through force measurements and imaging, we extract the effective stiffness of the system from stick-slip events at low velocities and relate it to the system's normal compression. We then predict the observed decrease of the global stiffness as function of the detachment by considering the spatial distribution of normal forces within the assembly, which determines an effective number of sheets contributing to the system's mechanical response. Our findings reveal a non-trivial interplay between internal stress distribution and mechanical response mediated by frictional forces, with implications for granular materials, textiles, fibrous systems, and mechanical metamaterials.