scholarly journals Design Equations for Mixed-Mode Fracture of Dental Ceramic-cement Interfaces Using the Brazil-nut-sandwich Test

2021 ◽  
pp. 1-33
Author(s):  
David Manan ◽  
Jeongho Kim ◽  
Renata Marques de Melo ◽  
Yu Zhang
Keyword(s):  
Fracture Toughness ◽  
Mixed Mode ◽  
Interfacial Fracture ◽  
Mixed Mode Fracture ◽  
Interfacial Fracture Toughness ◽  
Brazil Nut ◽  
Modulus Ratio ◽  
Dental Ceramic ◽  
Interfacial Cracks ◽  
Practical Guidance

Abstract Dental interfaces are subject to mixed-mode loading. This study provides a practical guidance for determining interfacial fracture toughness of dental ceramic systems. We address interfacial fracture of a composite resin cement sandwiched between two dental ceramic materials. Emphasis is placed on sandwich disc specimens with cracks originating from elliptical-shaped flaws near the center, for which analytical fracture mechanics methods fail to predict. The interaction integral method is used to provide accurate finite element solutions for cracks with elliptical-shaped flaws in a Brazil-nut-sandwich specimen. The developed model was first validated with existing experimental data, and then used to evaluate three most widely used dental ceramic systems: polycrystalline ceramics (zirconia), glass-ceramics (lithium disilicate), and feldspathic ceramics (porcelain). Contrary to disc specimens with ideal cracks, those with cracks emanating from elliptical-shaped flaws do not exhibit a monotonic increase in interfacial toughness. Also, interfacial fracture toughness is seen to have a direct relationship with the aspect ratio of elliptical-shaped flaws and an inverse relationship with the modulus ratio of the constituents. The presence of an elliptical-shaped flaw significantly changes the interfacial fracture behavior of sandwich structures. Semi-empirical design equations are provided for fracture toughness and stress intensity factors for interfacial cracks. The developed design equations provide a practical guidance for determining interfacial fracture toughness of selected dental ceramic material systems. Those equations take into account four critical factors: size of the elliptical flaw, modulus ratio of constituent materials, loading angle and applied load.

An experimental study on interfacial fracture toughness of 3-D printed ABS/CF-PLA composite under mode I, II, and mixed-mode loading

2019 ◽  
pp. 089270571987486 ◽  
Author(s):  
Abdul Samad Khan ◽  
Aaqib Ali ◽  
Ghulam Hussain ◽  
Muhammad Ilyas
Keyword(s):  
Fracture Toughness ◽  
Mixed Mode ◽  
Interfacial Fracture ◽  
Mode I ◽  
Mode Ii ◽  
Interfacial Fracture Toughness ◽  
Fused Deposition ◽  
Specimen Test ◽  
Nozzle Temperature ◽  
Printing Speed

Multimaterial structures made using fused deposition modeling (FDM) offer an attractive prospect for enhancing their mechanical properties and functionality. In this study, the interfacial fracture toughness of a unidirectional hybrid composite fabricated by FDM was studied through mechanical testing. The composite structure comprises acrylonitrile butadiene styrene and carbon fiber-reinforced polylactic acid. Since, de-adhesion or bond failure at the interface can occur under a combination of the different fracture modes, therefore, interfacial fracture toughness, in terms of the critical energy release rate, was characterized using double cantilever beam specimen test for mode I, end-notched flexural specimen test for mode II, and mixed-mode bending specimen test for mixed-mode I/II. Effects of varying process parameters, like printing speed and nozzle temperature, on the interfacial fracture toughness in mode I and II were also investigated. It was found that increasing the nozzle temperature and printing speed enhance the fracture toughness, both in mode I and II, but the effect of increasing nozzle temperature on mode II fracture toughness was quite significant.

Measurements of the Adhesion Strength of Cu/Epoxy Interfaces

1999 ◽  
Vol 586 ◽  
Author(s):  
H. Y. Lee ◽  
Jin Yu
Keyword(s):  
Fracture Toughness ◽  
Mixed Mode ◽  
Loading Condition ◽  
Double Cantilever Beam ◽  
Mixed Mode Loading ◽  
Interfacial Fracture Toughness ◽  
Brazil Nut ◽  
Molding Compound ◽  
Failure Path ◽  
In The Beginning

ABSTRACTCopper-based leadframe sheets were oxidized in a black-oxide forming solution, molded with epoxy molding compound (EMC), and the interfacial fracture toughness was measured using sandwiched double cantilever beam (SDCB) and sandwiched Brazil-nut (SBN) specimens.Results showed that pebble-like Cu2O precipitates on the leadframe had almost no adhesion to EMC while the opposite was true of the acicular CuO precipitates. Thus, the fracture toughness of the leadframe/EMC interface was close to zero in the beginning but rapidly increased to ˜100 J/m2 as acicular CuO nucleated on the smooth-faceted Cu2O layer. Under the mixed Mode loading the fracture toughness increased parabolically with the phase angle (ψ) with minimum at ψ = 0°. For ψ < -340, interface crack kinked into EMC. Fractography analyses based on XRD, SEM and AES studies showed that the failure path along the leadframe/EMC interface varied significantly with the loading condition and the crack speed.

Numerical Analysis of Three-Dimensional Semi-Elliptical Interfacial Cracks Subjected to Indentation Load

2014 ◽  
Vol 627 ◽  
pp. 289-292 ◽  
Author(s):  
N. Kurihara ◽  
Masayuki Arai
Keyword(s):  
Fracture Toughness ◽  
Three Dimensional ◽  
Analytical Formula ◽  
Interfacial Crack ◽  
Indentation Test ◽  
Interfacial Fracture ◽  
Indentation Load ◽  
J Integral ◽  
Interfacial Fracture Toughness ◽  
Interfacial Cracks

The aim of this study is to show elastic J-integral needed to evaluate the interfacial fracture toughness of bi-material in indentation test. Three dimensional J-integrals along the crack front tip in semi-elliptical crack lying on the interface were analyzed using domain integral technique installed in commercialized finite element code MARC. The J-integral was calculated under several kind of aspect ratio of semi-elliptical cracks. In order to have to evaluate the interfacial fracture toughness from interfacial crack length and indentation load obtained in indentation tests, the analytical formula for two dimensional interfacial crack J-integral under plane stress, which had been introduced by J. R. Rice and G. C. Sih, was modified in reflecting upon the three dimensional effect. Finally, the indentation test was conducted for Aluminum alloy/ PMMA combination sample, and the associated fracture toughness was evaluated.Fig.1 Schematic illustration of indentation testFig.2 Schematic illustration of analysis mode

scholarly journals An Improved Cohesive Zone Model for Interface Mixed-Mode Fractures of Railway Slab Tracks

2021 ◽  
Vol 11 (1) ◽  
pp. 456
Author(s):  
Yanglong Zhong ◽  
Liang Gao ◽  
Xiaopei Cai ◽  
Bolun An ◽  
Zhihan Zhang ◽  
...  
Keyword(s):  
Interface Crack ◽  
Cohesive Zone ◽  
Mixed Mode ◽  
Cohesive Zone Model ◽  
Complex Loading ◽  
Bending Test ◽  
Mixed Mode Fracture ◽  
Zone Model ◽  
Slab Track ◽  
Interfacial Cracks

The interface crack of a slab track is a fracture of mixed-mode that experiences a complex loading–unloading–reloading process. A reasonable simulation of the interaction between the layers of slab tracks is the key to studying the interface crack. However, the existing models of interface disease of slab track have problems, such as the stress oscillation of the crack tip and self-repairing, which do not simulate the mixed mode of interface cracks accurately. Aiming at these shortcomings, we propose an improved cohesive zone model combined with an unloading/reloading relationship based on the original Park–Paulino–Roesler (PPR) model in this paper. It is shown that the improved model guaranteed the consistency of the cohesive constitutive model and described the mixed-mode fracture better. This conclusion is based on the assessment of work-of-separation and the simulation of the mixed-mode bending test. Through the test of loading, unloading, and reloading, we observed that the improved unloading/reloading relationship effectively eliminated the issue of self-repairing and preserved all essential features. The proposed model provides a tool for the study of interface cracking mechanism of ballastless tracks and theoretical guidance for the monitoring, maintenance, and repair of layer defects, such as interfacial cracks and slab arches.

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