An Innovative Approach to Fatigue Cracking in Elastomers

Abstract

A methodology to analyze fatigue cracking in elastomers is pre sented. A fundamental equation and the basic principles of fracture mechanics are used to extract parameters characteristic of the material's resistance to cracking. These parameters are the specific energy of damage, γ*, and the dis sipative characteristic of the material, β. The basic formalism expresses the rate of crack propagation as: where dAldN is the cyclic rate of fatigue crack propagation, J is the energy release rate, and R, is the resistance moment that accounts for the amount of damage associated with the crack advance. The utilization of the proposed methodology has been demonstrated in view of experimental data generated for two different elastomers—a rubber com pound and a medically implantable polyurethane. The practical significance of the proposed methodology is apparent. It provides a basic rationale upon which the resistance to crack propagation of elastomers can be evaluated. On this basis microstructure-resistance to crack propagation relationships can be con structed. Also, it aids in lifetime assessment of load bearing structural compo nents manufactured from these materials.