We explore fracture nucleation and propagation within a transparent polydimenthylsiloxane elastomer using the “poker-chip” specimen. Global measurements are correlated with optical visualization at high spatial and adequate temporal resolution to identify the sequence of events; this is augmented with interrupted tests and x-ray computed tomography scans to probe the three dimensional geometry of the nucleation and growth of cracks. The experimental results are used to identify the different types of response, ranging from growth of surface cracks, to interior nucleation and growth of a single crack, to a completely nucleation dominated response. The dependence of the response on the specimen constraint, characterized by the specimen thickness, is explored through simulations within a finite deformation framework; a preliminary criterion for nucleation of cracks under multiaxial loading is proposed.
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