ABSTRACT
In table tennis recently, complex racket designs are used consisting of a wooden or glass or carbon fiber reinforced racket frame with multi-layer rubber/foam covers with special top surface properties. Various rubber compounds and glues (adhesives) are applied in the build up of the multi-layer rubber foam cover to impart greater spin or speed onto the celluloid ball. In terms of material characteristics, important aspects of a successful table tennis racket design are related to the elasticity and damping of the entire sandwich system and the specific surface properties that generate the spin of the celluloid ball upon the impact contact with the rubber surface. Despite the high interest of applying scientific concepts to table tennis, there is currently no widely accepted methodology available to characterize and to determine the performance profile of table tennis rackets as a whole or of individual or combined polymeric material layers in terms of their viscoelastic properties and property functions (Harrison and Gustavsen, 2002). On the other hand, materials science based concepts and criteria are necessary not only to objectively characterize the performance profile of new sandwich rubbers but also to study the change of materials properties over the playing time and to estimate the potential lifetime of sandwich rubber sheets. In systematically characterizing table tennis racket materials, various aspects need to be considered. The commonly used subjective ranking parameters (i.e. control, speed, catapult and spin) are a complex combination of two basic material property groups. In general, both bulk and surface properties will play an important role in racket performance. Moreover, the sandwich rubber is highly anisotropic (i.e. properties depend on the loading direction), and the bulk material properties are affected by the behavior of the pimple-in or pimple-out rubber cover sheet and the cellular rubber (sponge). With similar bulk properites of rubber sheets, pimple-in and pimple-out rubbers reveal characteristicly different surface properties. For pimple-in rubbers the friction properties are of special importance, which are a complex product of the adhesion capability and the surface deformation behavior (Chamet et al., 1999).
