Cavitation in rubber: an elastic instability or a fracture phenomenon?

It is by now well established that loading conditions with suffi ciently large triaxialities can induce the suddenappearance of internal cavities within elastomeric (and other soft) solids. The occurrence of such a phenome-non, commonly referred to as cavitation, can be attributed to the growth of pre-existing defects into fi nite sizes.In the fi rst part of this discussion, I will present a new theory within the context of nonlinear elasticity to study thephenomenon of cavitation in rubber that contrary to earlier approaches: (i) allows to consider general 3D loadingconditions with arbitrary triaxiality; (ii) applies to general classes of nonlinear elastic solids; and (iii) incorporatesdirect information on the initial shape, spatial distribution, and mechanical properties of the underlying defects atwhich cavitation can initiate. The basic idea is to fi rst cast cavitation in elastomeric solids as the homogenizationproblem of nonlinear elastic materials containing random distributions of zero-volume cavities, or defects. Then, bymeans of a novel iterated homogenization procedure, exact solutions are constructed for such a problem. Theseinclude solutions for the change in size of the underlying cavities as a function of the applied loading conditions,from which the onset of cavitation – corresponding to the event when the initially infi nitesimal cavities suddenlygrow into fi nite sizes – can be readily determined. In the second part of the discussion, I will confront the theorywith a variety of cavitation experiments with the objective of establishing whether the phenomenon of cavitationis an elastic instability (and hence depends only on the elastic properties of the rubber), or, on the other hand, afracture process (and hence depends on the fracture properties of the rubber). REFERENCES[1] Lefèvre, V., Ravi-Chandar, K., Lopez-Pamies, O. Cavitation in rubber: An elastic instability or a fracture phenomenon?International Journal of Fracture. 2014. Submitted.[2] Lopez-Pamies, O., Nakamura T., Idiart, M.I. Cavitation in elastomeric solids: I – A defect growth theory. Journal of theMechanics and Physics of Solids. 2011, 59, 1464–1487.[3] Lopez-Pamies, O., Nakamura T., Idiart, M.I. Cavitation in elastomeric solids: II – Onset-of-cavitation surfaces forNeo-Hookean materials. Journal of the Mechanics and Physics of Solids. 2011, 59, 1488–1505.