Modelling of bonded multilayered disks subjected to biaxial flexure tests

Biaxial flexure tests have been used extensively for the strength measurements of monolithic brittle materials. However, despite the increasing applications of multilayered structures, characterization of their strengths using biaxial flexure tests is unavailable. This is because the analytical description of the relation between the strength and the fracture load for multilayers subjected to biaxial flexure tests is nonexistent. To characterize the biaxial strength of multilayers, an analytical model is developed in the present study to derive the general closed-form solutions for the elastic stress distributions in thin multilayered disks subjected to biaxial flexure tests. To verify the analytical solutions, finite element analyses are performed on trilayered disks subjected to ring-on-ring tests. Good agreement is obtained between analytical and numerical results. The present closed-form solutions hence provide a basis for evaluating the biaxial strength of multilayered systems. Depending upon the strength of the individual layers and the stress distribution through the thickness of the multilayer during testing, cracking can initiate from any layer under tension.