Experimental and numerical study of the effect of surface patterning on the frictional properties of polymer surfaces

TL;DR

This study investigates how laser patterning on polyethylene surfaces influences frictional behavior, revealing decreased friction and altered stick-slip dynamics, with humidity playing a significant role, supported by experiments and simplified numerical modeling.

Contribution

It provides new insights into how surface patterning and environmental factors affect polymer friction, validated by experiments and a simplified spring-block model.

Findings

Patterned surfaces show reduced dynamic friction.

Humidity increases friction and promotes stick-slip events.

Numerical model qualitatively matches experimental results.

Abstract

We describe benchmark experiments to evaluate the frictional properties of laser patterned low-density polyethylene as a function of sliding velocity, normal force and humidity. The pattern is a square lattice of square cavities with sub-mm spacing. We find that dynamic friction decreases compared to non-patterned surfaces, since stress concentrations lead to anticipated detachment, and that stick-slip behavior is also affected. Friction increases with humidity, and the onset of stick-slip events occurs in the high humidity regime. Experimental results are compared with numerical simulations of a simplified 2-D spring-block model. A good qualitative agreement can be obtained by introducing a deviation from the linear behavior of the Amontons-Coulomb law with the load, due to a saturation in the effective contact area with pressure. This also leads also to the improvement of the quantitative results of the spring-block model by reducing the discrepancy with the experimental results, indicating the robustness of the adopted simplified approach, which could be adopted to design patterned surfaces with controlled friction properties.