Although there has been immense amount of study concerning the fracture of crowns, the bulk of the work reported in the literature has focused on model flat ceramics/polymer bilayers loaded on the top surface with a spherical indenter. Full-coverage ceramic dental restorations (crowns) are a special case in point. These radial cracks can propagate rapidly to the margins, the flat edges of the bisecting plane, under cyclic loading at relatively low loads, owing to mechanical fatigue and a greater spatial range of tensile stresses in curved structures.īrittle layers on polymeric substrates are relevant to a wide range of engineering structures, including biomedical prostheses. Flexural radial cracks require a higher load to initiate in the curved specimens relative to flat structures. Our findings showed that cone cracks form at lower loads, and can propagate through the quartz layer to the quartz/polymer interface at lower number of cycles, in the curved specimens relative to their flat counterparts. Flat quartz glass plates on polymer substrates were tested as a control group. Critical loads and number of cycles to initiate and propagate near-contact cone cracks and far-field flexure radial cracks to failure were recorded. The resulting hemi-cylindrical glass shells were bonded internally and at the edges to polymeric supporting structures and loaded axially in water on the outer circumference with a spherical tungsten carbide indenter. Specimens were fabricated by bisecting cylindrical quartz glass hollow tubes. Damage response of brittle curved structures subject to cyclic Hertzian indentation was investigated.
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