Testing and Simulation for Infinite Life Design for Rubber Products

A rubber compound’s intrinsic strength has great utility for rubber product developers. By keeping tearing energy at all times below the intrinsic strength, a developer can assure indefinite life with minimum effort. Additionally, fatigue crack growth rate behavior can be rapidly approximated from knowledge of tear strength and intrinsic strength.

The intrinsic strength is measured using a cutting method developed originally by Lake and Yeoh, and implemented on the Coesfeld Intrinsic Strength Analyser. The method minimizes crack tip process zone viscoelastic dissipation and therefore indicates the bare-minimum energy required to propagate a crack by breaking polymer chains.

The intrinsic strength can be utilized in combination with critical plane analysis to compute a worst-case safety factor relative to the fatigue limit. Several examples are presented, including:

• a grommet sizing application
• a tire belt compounding application
• a squeeze pump hose

In each example, simulation is used to compute the fraction of loading reserve (ie safety factor) relative to the experimentally determined intrinsic strength.