Friction Dynamics of Foams under Nonlinear Motion

Foams are viscoelastic soft materials with complexmechanical properties. Here, we evaluated the friction dynamics offoams between acrylic plates using a sinusoidal motion frictionevaluation system and we found some interesting characteristicsunder accelerated conditions. On a typical solid surface, asymmetrical friction profile, in which static and kinetic frictions areobserved, is obtained under reciprocating nonlinear motion.Meanwhile, significant lubricant effects and velocity-dependentfriction profiles without static friction were observed in foams. Thefriction force in foams increased in proportion to the power ofvelocity, with a power index of <1. These characteristic and dynamicphenomena in foams were observed in this study. They had beencaused by the formation of a thick lubricantfilm and variousdissipative modes including surfactant diffusion, viscous dissipation, and wall slip of bubbles. Moreover, the addition of a thickenerincreased the friction force and the delay time of friction response and improved the foam durability against normal force and shear.Thesefindings are useful for understanding dynamic phenomena in soft materials.

Automated summary

Friction dynamics of foams between acrylic plates were evaluated under accelerated conditions, revealing significant lubricant effects and velocity-dependent friction profiles, with friction force increasing proportionally to the power of velocity.