Test parameter sensitivity of the Lake-Yeoh cutting method for measurement of intrinsic strength of rubber

Abstract

The intrinsic strength of rubber, T₀ is one of the key parameters when describing fracture behaviour of elastomer because it is at this specific value of energy that crack growth initiates within loaded rubber material. The Coesfeld Intrinsic Strength Analyzer (ISA) has been established as the most efficient equipment to directly analyse T₀ for various rubber materials. However, to obtain the most reliable and reproducible results it is crucial to understand the influence of boundary conditions of the ISA measuring methodology. Therefore, in this study sets of boundary conditions were chosen to be analysed through mechanical response of reference EPDM material with known T₀ value. For the purposes of this study the effects of individual boundary conditions were compared through directly measured value of intrinsic cutting energy, S₀ which is proportional to T₀. Blade sharpness and geometry showed the greatest impact followed by repetition of blade and specimen milling direction whereas the relaxation time and number of measuring strains showed no significant influence. The results of this study show that the knowledge of blade micro-geometry is at its most importance during the T₀ analyses. Moreover, the data clearly indicates possible future modification of boundary conditions to achieve a very efficient testing procedure with significantly reduced time required for the analyses.