Statement of Problem: In a previous study it was reported that a durable resin-ceramic tensile bond could be obtained by an appropriate silane application without the need for HF acid etching the ceramic surface. Evaluation of the appropriate application of silane by other test methods seems to be necessary.Purpose: The purpose of this study was to compare the interfacial fracture TOUGHNESS of smooth and roughened ceramic surfaces bonded with a luting resin.Materials and Methods: Ceramic discs of 10 mm in diameter and 2 mm in thickness were prepared.Four different surface preparations (n=10) were carried out consisting of (1) ceramic surface polished to a 1µm finish, (2) gritblasted with 50µm alumina, (3) etched with 10% HF for 2 min, and (4) gritblasted and etched. The ceramic discs were then embedded in PMMA resin. For the adhesive area, the discs were masked with Teflon tapes. A circular hole with diameter of 3 mm and chevron-shaped with a 90° angle was punched into a piece of Teflon tape. The exposed ceramic surfaces were treated by an optimised silane treatment followed by an unfilled resin and then a luting resin cylinder of 4mm in diameter and 11 mm in length was built. Specimens were stored in two different storage conditions: (A): Distilled water at 37°C for 24 hours and (B): Distilled water at 37°C for 30 days. The interfacial fracture TOUGHNESS (GIC) was measured at a cross-head speed of 1 mm/min. The mode of failure was examined under a stereo-zoom microscope and fracture surfaces were examined under Scanning Electron Microscope.Results: The mean interfacial fracture TOUGHNESS values were; Group A: 1) 317.1±114.8, 2) 304.5±109.2, 3) 364.5±169.8, and 4) 379.4±127.8 J/m2±SD. Group B: 1) 255.6±134.4, 2) 648.0±185.1, 3) 629.3±182.6 and 4) 639.9 ±489.0 J/m2±SD. One way Analysis of Variance showed that there was no statistically significant difference in the mean interfacial fracture TOUGHNESS for groups A1-A4 (P>0.05). However, the mean interfacial fracture TOUGHNESS for group B1 was significantly different from that for groups B2, B3 and B4 (P<0.05). Independent-ٍٍٍSamples T-Test results showed that there was a significant increase in the GIC mean value for groups B2 and B3 after 30 days water storage (P<0.05). The modes of failure were predominantly interfacial or cohesive within the resin.Conclusions: The fracture TOUGHNESS test method used in this study would be appropriate for analysis of the adhesive zone of resin-ceramic systems. From the results, it can be concluded that micro-mechanical retention by gritblasting the ceramic surfaces could be sufficient with no need for HF acid etching the ceramic surfaces when an appropriate silane application procedure is used.

Statement of Problem: Evaluation of fracture properties is a basic principle for true assessment of brittle materials’ properties. Resin–based composite materials are being used extensively in today’s dentistry. Fracture TOUGHNESS is considered an important parameter for providing useful information about material’s nature, properties and its resistance to fracture. Purpose: The purpose of this study was to evaluate the fracture TOUGHNESS of a resin composite produced in the country and to compare it with that of other standard materials. Materials and Methods: Four types of resin composite materials were used as follow to prepare 60 specimens (n=15 for each group), A) Tetric Ceram (Ivoclar–Vivadent); B) Brilliant (Coltene-Whaledent); C) SpectrumTPH (Dentsply); and D) Ideal Macoo (Ideal Macoo, Iran). Specimens of 5 mm diameter (± 0.1 mm) and 2 mm depth (±0.1 mm) were prepared in a central notch (90° notch angle) PTFE mold. Then specimens were light cured with two applications of overlapping exposures for a total of 120 s and were stored in distilled water at 37ºC for 48 hours, A cylindrical roller of 3 mm diameter was seated inside the V sections and fracture was accomplished in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed by one–way ANOVA and post-hoc paired Tukey HSD test with P<0.05 as the limit of significance. Results: The mean KIC and torque to fracture (T) values for each material tested were; A) 3.08±0.42, 16.99±2.34, B) 2.88±0.63, 16.04±1.98; C) 3.40±0.53, 18.75±2.93 and D) 2.87±0.46, 15.78±2.57 MN/m3/2±SD and N/mm±SD, respectively. Group C showed significantly the highest mean KIC and T values among groups tested which was significantly higher than that of group B and D (P<0.05). The mean KIC and T values for groups A, B, and D were not significantly different (P>0.05). Conclusion: From evaluating the fracture properties of materials tested in this study it was concluded that the mean fracture TOUGHNESS value for SpectrumTPH (Dentsply) was significantly higher than that of Ideal Macoo resin composite material (Ideal Macoo, Iran). The F.T value for Ideal Macoo was considered acceptable as it was not significantly different from that of other resin composite materials tested.  

This paper presents the results of investigation carried out to improve the mechanical TOUGHNESS of cement mortar. TOUGHNESS is a basic parameter which has to be improved in brick walls, concrete roads, machine foundations, dams etc. Materials fails due to an impact force and vibrations resulting in minor cracks and bonding failure between bricks, it leads to failure of the structure. In order to avoid the failure TOUGHNESS has to be enhanced and this can be done by modifying the cement mortar. In this project recycled glass is used in the form of powder less than 45 μ m as replacement of cement. Also natural rubber latex is added as 20% replacement of water. Three mortar mix are considered, namely 1: 3, 1: 4, 1: 5. The compressive strength of mortar cubes, and flexural strength are done to determine the strength and TOUGHNESS of the mortar. Results showed that fracture TOUGHNESS increased to considerable amount.

Epoxy resins (ER) are considered as one of the most important classes of thermosetting polymers and are extensively used in various applications. But they are very brittle, with poor resistance to crack propagation and have low impact strength. In the present work, a series of hydroxyl terminated polybutadiene (HTPB) was directly dispersed in the epoxy resin. Then, the dispersed phase was cross-linked by divinylbenzene (DVB) that was previously added to HTPB. Different content of DVB and HTPB are evaluated for effecting on the most of physico-chemical properties of the epoxy resin. The FTIR analysis evidenced the occurrence of a chemical reaction between HTPB and DVB and also ER which was led to improved compatibility. The DMTA analysis of samples indicated different Tg for HTPB/DVB and ER in the mixture and explaining the phase separation between rubber and matrix phases. On adding DVB the stress-at-break increased accompanied by an increase in the elongation-at-break value. Maximum impact strength is obtained by adding 20 phr of DVB and 5 phr HTPB. Finally, SEM analysis showed that modified rubber particles’ diameter is about 5 mm (corresponding to maximum of TOUGHNESS).

Fracture TOUGHNESS is usually used as a generic term for measures if materials resistance to expansion of a crack in engineering applications such as petrochemical industries and oil and gas pipelines. The concept of fracture TOUGHNESS received profound importance in engineering design and applications, after the destruction of liberty ships in the World War II. In this paper, fracture TOUGHNESS test methods, evaluation and standardization of metal materials are reviewed based on linear elastic and elastic-plastic fracture mechanics. The general principles and methods of testing developed by the American Society for Testing and Materials are explained. The main parameters of fracture mechanics such as elastic energy release rate (G), stress intensity factor (K), J integral, crack tip opening displacement (CTOD) and crack tip opening angle (CTOA) are defined. Finally, the scientific and computational foundations of the two factors (K) and CTOD, as the most widely used industrial factors will be examined in detail.

The effects of carbon equivalents of 2.3, 3.3 and 4.3% on the microstructure, hardness and fracture TOUGHNESS of a low alloyed ductile cast iron in as cast, annealed, normalized and austempered conditions have been investigated. Fracture TOUGHNESS was measured using a plain-strain fracture TOUGHNESS (kIc) test and also J-Integral approach. The results show that the pearlite content increases as the CE decreases from 4.3 to 2.3% The nodularity and nodule count also decrease with decreasing the CE%. The annealed samples show a predominantly ferritic structure. Iron with 2.3 CE% shows pearlitic microstructure. The austempered microstructure contains bainitic ferrite and retained austenite at all carbon equivalents. The fracture TOUGHNESS value (kQ and kIc) of ductile iron increases with increasing the CE% in all conditions and a maximum value is obtained in austempered condition. The hardness decreases with increasing CE% and an maximum value of 526 HV50 can be obtained at 2.3 CE% in a austempered condition. The SEM study shows that all the fractures of austempered specimens are ductile in nature whilst all that of normalized condition are brittle. Fracture behavior of 4.3 CE% ductile iron in as cast and annealed conditions are ductile where those of 2.3% are brittle. The iron with 3.3% shows a brittle fracture in as cast condition and a ductile fracture in annealed condition. The results show that J. integral approach can be used in measuring of kIc, particulary if the kIc values can not be achieved.