1 3D crack network during the scratching of a polymer: comparison between experimental results and localized multigrid X-FEM M.C Baietto Dubourg 1 , J. Rannou 1 , A. Gravouil 1 , H. Pelletier 2 , C. Gauthier 2 , R. Schirrer 2 1 LaMCoS CNRS UMR 5259 Villeurbanne, France; 2 ICS CNRS UPR 22 Strasbourg, France Abstract Attempts have been made to correlate the scratch behavior and basic material properties of polymers and a correlation has been established between the scratch damage, the bulk response and the friction coefficient. The scratch behavior of a thermoset solid polymer exhibiting brittle behavior in tension was investigated to determine how the behavior of the bulk material affects the scratch resistance. The surfaces were scratched under progressive scratch loading and an imaging system was used to record real time photographs of the in-situ contact area and scratch damage corresponding to cracking near the rear edge of the contact. The 3D crack pattern has been analyzed using fluorescence confocal laser scanning microscopy. A finite element simulation gave an estimation of the contact loading used as input data for the 3D crack network onset and development analysis based on 3D localized multigrid X-FEM techniques. The level sets functions are defined from the measured crack geometry. A set of 11 localized multigrid meshes are used to focus on the cracked and contact areas. The accurately computed stress distributions within the 3D cracked are of great interest to understand the crack network formation observed during the experiments. This combined approach opens the way for identifying and even validating 3D crack propagation modeling. 1 Introduction Many authors have studied damage to polymeric surfaces during scratching [1], [2],[3], [4] and it has been found to take the form of open or closed cracks. The assumption generally retained to explain this cracking is the existence of tensile stress at the rear edge of the contact. The diversity of the damage nevertheless suggests that it does not occur through a single mechanism. In addition, no clear relationship has been established between the bulk response and scratch damage. The scratch behavior of solid polymers was therefore investigated to determine how the behavior of the bulk material affects the scratch resistance. To enhance the understanding and to get a more systematic predictive approach, experimental tests and a numerical approach are combined. A CR39 polymer is chosen for this comparison as it displays brittle tension behavior. An accurate experimental in-