title: Creep-assisted slow crack growth in bio-inspired dental multilayers.
abstract: Ceramic crown structures under occlusal contact are often idealized as flat multilayered structures that are deformed under Hertzian contact loading. Previous models treated each layer as linear elastic materials and resulted in differences between the measured and predicted critical loads. This paper examines the combined effects of creep (in the adhesive and substrate layers) and creep-assisted slow crack growth (in the ceramic layer) on the contact-induced deformation of bio-inspired, functionally graded multilayer (FGM) structures and the conventional tri-layers. The time-dependent moduli of each of the layers were determined from constant load creep tests. The resulting modulus-time characteristics were modeled using Prony series. These were then incorporated into a finite element model for the computation of stress distributions in the sub-surface regions of the top ceramic layer, in which sub-surface radial cracks, are observed as the clinical failure mode. The time-dependent stresses are incorporated into a slow crack growth (SCG) model that is used to predict the critical loads of the dental multilayers under Hertzian contact loading. The predicted loading rate dependence of the critical loads is shown to be consistent with experimental results. The implications of the results are then discussed for the design of robust dental multilayers.
authors.affiliation: Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA; The Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, Princeton, NJ 08544, USA. Electronic address: jingdu@alumni.princeton.edu.
authors.forename: Jing
authors.initials: J
authors.lastname: Du
authors.affiliation: Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong, China. Electronic address: xinrui.niu@cityu.edu.hk.
authors.forename: Xinrui
authors.initials: X
authors.lastname: Niu
authors.affiliation: Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA; The Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, Princeton, NJ 08544, USA. Electronic address: soboyejo@princeton.edu.
authors.forename: Wole
authors.initials: W
authors.lastname: Soboyejo
mesh_terms: D000268:Adhesiveness; D032701:Biomimetics; D002516:Ceramics; D003442:Crowns; D003764:Dental Materials; D004548:Elasticity; D020342:Finite Element Analysis; D005898:Glass / Q000737:chemistry; D008422:Materials Testing; D055595:Mechanical Phenomena; D011076:Polycarboxylate Cement / Q000737:chemistry; D014783:Viscosity
chemical_list: D003764:Dental Materials; D011076:Polycarboxylate Cement; C005506:polycarbonate
keywords: Creep; Dental multilayers; Hertzian contact; Slow crack growth