Fracture and fatigue of bonded rubber blocks under compression

Fracture and fatigue failure of bonded rubber cylinders are discussed. Under large compressive forces, two modes of fracture are possible: splitting open of the free surface and tearing at or near the bonded edges; tearing energy T for the latter case is estimated. Under cyclic compression, the probable fracture mode of rubber is by crack propagation, leading to the bulged volume breaking away. The corresponding tearing energy is calculated. To predict the fatigue life, the rate of crack growth dc/dn is assumed to be proportional to T². A life prediction equation is thus obtained, of the form: load cycle N = (K/g)⁵, where K is a constant, about 10 for a typical soft natural rubber compound, and g is the maximum shear strain set up at the edges of the bonded surfaces.