Hydraulically pumped cone fracture in bilayers with brittle coatings

An earlier finite element modeling analysis of inner cone cracks in monolithic brittle solids subject to cyclic indentation in liquids is extended to include the case of a brittle layer bonded to a compliant substrate, using a model glass/polycarbonate bilayer system as an illustrative case study. Provision is made for incorporation of plate flexure stresses, along with hydraulic pumping stresses, into the Hertzian contact field. Tensile flexure stresses ultimately accelerate inner cone cracks through the lower halves of the glass plates to unstable failure. The analysis accounts for the experimentally observed trends in the inner cone crack evolution in cyclic contact fatigue.