Friction induced damage: preliminary numerical analysis of stresses within painted automotive plastics induced by large curvature counterfaces

Surface damage to modern plastic automotive fasciae (bumpers) arises as a result of numerous physical ‘sliding’ contact scenarios. The most common tribological events include fascia contact with fifex obstacles, and fascia to fascia (vehicle to vehicle) sliding contact. The tribologically induced stresses may introduce abrasion, shear, tensile, and delamination failure in the paint and the plastic substrate layers. Subsurface stresses imparted by a large curvature counterface and a thin plastic substrate on a hard foundation are compared using both classic analytical methods and finite element analysis. This is the first quantitative study of its kind for aiding in the development of a friction induced damage (FID) testing device. Phenomenological insights into FID are presented. Relevant analysis methods for FID are also reviewed. Both methods investigate a cylindrical counterface and a painted plastic substrate on a stiff foundation. A thin polymer coating on the counterface imparts a sliding frictional coefficient, μ ∼ 1.0. Results of three-dimensional numerical analysis are presented for the transverse contact stresses between counterfaces of different curvature, friction coefficient, and normal force. The subsurface maximum stresses move toward the counterface as the curvature is reduced, and the numerical calculations for TPO-on-foam substrates indicate the likelihood that shear initiates the failure in the subsurface. Classic Hertzian calculations are inadequate particularly, when material yielding and shear failure are present.