The crack growth resistance of human dentin was characterized as a function of relative distance from the DEJ and the corresponding microstructure. Compact tension specimens were prepared from the coronal dentin of caries-free 3rd molars. The specimens were sectioned from either the outer, middle or inner dentin. Stable crack extension was achieved under Mode I quasi-static loading, with the cr...

The structure of human cortical bone evolves over multiple length scales from its basic constituents of collagen and hydroxyapatite at the nanoscale to osteonal structures at near-millimeter dimensions, which all provide the basis for its mechanical properties. To resist fracture, bone's toughness is derived intrinsically through plasticity (e.g., fibrillar sliding) at structural scales typical...

Crack propagation of PMMA in some liquid environments is described for various testing conditions, such as fixed load, fixed displacement and monotonically increasing displacement. Fracture mechanics concepts have been used successfully in analysing the results. When continuous stable cracking is achieved, values of fracture toughness (R) for PMMA under these loading conditions are obtained as ...

This report presents the results obtained by the five U.S. participating laboratories in the Versailles Advanced Materials and Standards (VAMAS) round-robin for fracture toughness of advanced ceramics. Three test methods were used: indentation fracture, indentation strength, and single-edge pre-cracked beam. Two materials were tested: a gas-pressure sintered silicon nitride and a zirconia tough...

Veneering ceramics designed to be used with modern zirconia framework restorations have been reported to fracture occasionally in vivo. The fracture toughness of such veneering ceramics was measured and compared to that of conventional feldspathic porcelain veneering ceramics for metal framework restorations. The fracture toughness of the leucite free veneer was measured to be 0.73 MPa m ± 0.02...

Al2O3 ceramic reinforced with 4-wt% multiwalled carbon nanotube (CNT) is plasma sprayed for improving the fracture toughness of the nanocomposite coating. Two different methodologies of CNT addition have been adopted in the powder feedstock to assist CNT dispersion in the nano-Al2O3 matrix. First, spray-dried nano-Al2O3 agglomerates are blended with 4 wt% CNT as powder-feedstock, which is subse...

The present study is devoted to the problem of enhancing fracture toughness of ZrO2 ceramic materials through the formation of composite structure by addition of Al2O3 and NiO particles. In this paper, we analyzed the general and distinguished features of microstructure of both composite materials and its effect on fracture toughness of materials. In this paper, we used the XRD, SEM, and EDS me...

Quantitative assessment of the strength and toughness of bone has become an integral part of many biological and bioengineering studies on the structural properties of bone and their degradation due to aging, disease and therapeutic treatment. Whereas the biomechanical techniques for characterizing bone strength are well documented, few studies have focused on the theory, methodology, and vario...

We present a model for the brittle–ductile transition in ferritic steels based on two dimensional discrete dislocation simulations of crack-tip plasticity. The sum of elastic fields of the crack and the emitted dislocations defines an elasto–plastic crack field. Effects of crack-tip blunting of the macrocrack are included in the simulations. The plastic zone characteristics are found to be in a...

Bioactive glass ionomer cements (GICs) have been in widespread use for ∼40 years in dentistry and medicine. However, these composites fall short of the toughness needed for permanent implants. Significant impediment to improvement has been the requisite use of conventional destructive mechanical testing, which is necessarily retrospective. Here we show quantitatively, through the novel use of c...