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Recovery of residual scratch groove

Mechanisms of recovery of a deformed or even damaged of polymeric functionalized surfaces after static and dynamic contact with a harder and rough surface are important scientific and industrial keypoints for improving the tribological and adhesive properties as a function of their physical and chemical properties. In order to improve understanding of the viscoelastic and viscoplastic behaviours detailed knowledge of the contact mechanics of polymeric are required and some developments of experimental dedicated tools are needed.

Based on the Micro Visio Scratch developed in the lab to study the different transitions of mechanical behaviours from elastic to fully plastic and damaged contacts during scratch as a function of experimental conditions, new equipment has been set up. With this original and unique apparatus, we are able to study the deformation of the tested surface during static contact (indentation) and dynamic contact (scratch) as a function of the loading conditions but also during recovery with time and temperature.

After an important step that allows the identification of the viscoelastic and viscoplastic properties of polymeric materials using macroscopic creep and relaxation test in compression at different imposed strains and temperatures, indentation and scratch experimental tests are reproduced by finite element modelling both during contact and then recovery phases. FEM results provide some information about stress-strain fields under the contact and in the residual groove that may explain non linear behaviour observed experimentally.

This opens up possibilities to study relaxation processes leading to recovery and/or reconstruction of surfaces (containing hard and soft polymers, polymers filled with nanoparticles, semi-crystalline polymers…), e.g. applicable in the context of self healing functionnalized surfaces and dry self-lubrication. News bulk and coating polymeric materials are developed by the Freiburg Materials Research Center (Pr. Rolf Mülhaupt) that has to synthesize mixed macromolecular systems with surface active components which can re-organize at surfaces after deformation.