Fragmentation Processes in Polystyrene Films Under Sliding Conditions

Fracture processes of thin (10–100 μm) polystyrene films on PMMA substrates have been investigated within macroscopic single-asperity sliding contacts with rigid spherical counterfaces. Using the resources of in situ contact visualisation, the development of cracks has been analysed for various values of the ratio of the contact radius to the film thickness. Damage mechanisms were dominated by the formation of a network of regularly spaced cracks at the leading edge of the contact. These processes were analysed in the light of a fragmentation model based on contact mechanics simulations of the stress field induced within cracked films. It emerged from the simulations that the mean spacing between adjacent cracks can be correlated to the strength of the polymer coating.