title: Determining the slow crack growth parameter and Weibull two-parameter estimates of bilaminate disks by constant displacement-rate flexural testing.
abstract: OBJECTIVE
  This study examined the influence of displacement-rate and relative layer heights (RLH) on the slow crack growth exponent and Weibull two-parameter estimates of bilayered ceramic composite disks composed of In-Ceram Alumina and Vitadur Alpha porcelain.
  
  
  METHODS
  Equibiaxial disks were fabricated with RLH of 1:2, 1:1 and 2:1, for In-Ceram Alumina and Vitadur Alpha porcelain, respectively. Ninety specimens each (30 1:2, 30 1:1, and 30 2:1) were tested in an equibiaxial ring-on-ring testing apparatus at displacement-rates of 0.127, 1.27 and 12.7 mm min(-1).
  
  
  RESULTS
  Weibull parameters were statistically significantly affected by changes in RLH at a constant displacement-rate and the slow crack growth parameters were significantly affected by RLH. Many specimens exhibited nonbrittle failure modes. Nonbrittle failures usually exhibited a fall, followed by a rise in load prior to catastrophic failure, and most occurred in specimens with thicker cores at low displacement-rates.
  
  
  CONCLUSIONS
  Geometries of layered materials may affect their reliability and longevity.
authors.affiliation: US Army Dental Research Detachment, 310B B Street, Building 1-H, Great Lakes, IL 60088-5259, USA. geoffrey.thompson@na.amedd.army.mil
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Thompson
mesh_terms: D000537:Aluminum Oxide; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D004548:Elasticity; D008422:Materials Testing; D018583:Pliability; D016019:Survival Analysis
chemical_list: C483026:In-Ceram Alumina; C483027:vitadur alpha; D003776:Dental Porcelain; D000537:Aluminum Oxide