For the past decades researchers are showing immense interest to investigate the natural advantage of preparation of Composites from minerals such as Bauxite particles, and proved their effectiveness as cost effective reinforcing agents in fabrication of high performance Composites. This study, is a new attempt in using the Iraqi natural Bauxite powder with different proportions (2, 4 and 6 wt%) in preparation of aluminum metal matrix Composites (AMMCs) using Stir Casting and Mg additives. In experimental work, the Bauxite stones were crashed and milled, then the powder was fired at 1400 ○C. The powders were characterized using particle size, XRD and XRF analysis. The AMMCs casts were machined, polished, preheated, and their Properties were characterized using Hardness measurements, microstructural observations, and calculation of their Young's modulus, Poisson’s ratio and Fracture Toughness. Also, their Fracture Toughness were evaluated by means of Crack mouth Opening Displacement (CMOD) measurements from extensometer recordings. The results proved the successful production of AMMCs with improved Fracture Toughness, Hardness and elastic modulus Properties using Mg and Iraqi fired Bauxite added at 2 and 4 wt% by Stir Casting. Moreover, results from CMOD measurements showed the effect of addition Bauxite particles at 2 and 4 wt% in increasing "maximum load at failure" and "critical CMOD at critical load" of the matrix Materials to about " 25 and 44%" , and " 32 and 47%", respectively. Also, at these ratios, the calculated Fracture Toughness of the matrix Materials by means of KIC, and young modulus showed improvement at about “22 and 69%”, and “8 and 12%”, respectively. Addition of Bauxite at 6% could not give the required improvement in the Fracture Toughness despite its effects in recording the highest improvements in Hardness (57%)   and elastic modulus (22%) due to the brittle behavior of AMMCs at this ratio.

Bioactive glass-ceramic is used as a replacement Material for bone tissue due to its compatibility, bioactivity, and the ability to form a crystallized hydroxyapatite layer, which is similar in composition and structure to the inorganic component of the bone mineral phase. In this paper, bioglass-ceramic was toughened using zirconia to improve its Mechanical behaviour (i.e. Crack Opening dsplacement and Fracture Toughness). The Fracture Toughness of the bioactive glass cerami/zirconia Composite was measured using three-point bending technique. Digital Image Correlation (DIC) technique was utilized for visualized the Crack initiation and calculation the Crack Opening Displacement (COD) at the tip and mouth of the Crack and measuring of the Crack propagation of the bioactive glass cerami/zirconia Composite. The results indicated that the incorporation of the zirconia particles improved the measured Fracture Toughness of the BGC/ZrO2 Composite. The Toughness of Composite bioceramics is enhanced due to Crack branching and Crack deflection due to the presence of zirconia particles.

The Purpose of this study is fabrication aluminum matrix Composites reinforced with TiB2 in situ ceramic particles by the Stir Casting process. So, produce Composites with 2%, 4% and 6 wt% and contrast with AA5083 alloy of reinforcing particles without. In this study, in order to impurities and surface contamination cleanse and also water molecules contained in the powders of TiO2 and B2O3, preheating operation performed on them. Then milling operation done with speed 750 Rpm for 15 hours, in order to Mechanical activation and prevent performed of adverse reactions between the powders in during the Casting process. After preparing the powders, they are stoichiometric determined ratio to achieve values of 2%, 4% and 6wt% TiB2 phase were added to the AA5083 alloy molten and after Stirring for 15 minutes with speed 350 Rpm, the Casting was performed. At the end of in order to Properties improve of Casting specimens from used hot extrusion process. Then, using phase analysis (XRD), microstructure analysis (OM and SEM) and tensile, Hardness and density tests, production or non-production, distribution of reinforcing particles and Mechanical Properties investigated of samples. The ultimate goal of this research is, using a combined method to problems solve of cast aluminum matrix Composites and improving their Properties. The results showed an improvement in Mechanical Properties of samples with increasing reinforcing particles up to 4wt% after completion treatment. As the highest tensile strength and Hardness obtained at cast and extruded sample (at temperature of 330 ° C) AA5083/4% TiB2.

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.

Production of aluminum matrix Composites is widespread because these Material provide enhanced Mechanical Properties compared to aluminum. One the most important parameters of metal matrix Composite production is uniform distribution of reinforcing nanoparticles in matrices using the Stir-Casting method. Second is ensuring high wettability, which is determined by evaluating the Properties of Materials on a nano-scale. In this study, aluminum Composites were reinforced with titanium carbide nanoparticles coated with aluminum to increase wettability. Particles were prepared and added to a molten aluminum alloy. After Stirring the particle mixture as a variable parameter, Casting was conducted in a sand mold. To evaluate the Mechanical Properties of the Composite, the Brinell test was used to determine Hardness and the pin-on-disk test was used to measure wear rate and the friction coefficient. The results showed that the Hardness of the Composite increased from 84 BHN to 134 BHN as nanoparticles were added to the alloy. Additionally, as Stirring time increased, weight loss decreased with respect to the base alloy, while the coefficient of friction increased.

In recent years, metallic multilayer Materials have been the focus of many researchers and different industries. Cold roll bonding is one of the methods for producing layered Composites which, compared to other Composite manufacturing methods is more economic and has the ability to produce layered Composite with different Material. In this research, for the first time and according to ASTM-E561 and using compact tension specimens, plane stress Fracture Toughness for thin three-layer Al/Cu/Al Composite sheets produced by Cold Roll Bonding Process was investigated. The Fracture Toughness is an important parameter in the design and their analysis can predict Crack growth and life for Material that has Crack. In addition to the Fracture Toughness, Mechanical Properties and tensile Fracture surfaces were evaluated by using uni-axial tensile test, micro Hardness and scanning electron and optic microscopy, respectively. Results showed the value of tensile strength, micro Hardness and Fracture Toughness for Al/Cu/Al layered Composite compared to initial Al 5052 and pure Cu increased, the main cause of this increase is applied high strain and cold working. Value of Fracture Toughness for Al/Cu/Al layered Composite received 38.7MPa.m1.2 that compared to initial Al5052 and pure Cu, 81% and 165% enhanced, respectively. Results of SEM demonstrated that ductile Fracture mechanism were observed for Al/Cu/Al Composite such as initial samples, but the difference is that dimples for Composite layers are shallower and smaller compared to initial samples.

This study investigated the effect of adding boron carbide microparticles (B4C) and titanium diboride nanoparticles (TiB2) on the microstructure, tensile strength, and Hardness of A356 aluminum Composite. In so doing, 2.5, 5, and 7.5 vol.% B4C reinforcements and 2.5 vol.% TiB2 reinforcement were added to the field by Stir Casting at 1000 °C using in situ process. The TiB2 nanoparticles were processed in situ by cryolite precursors (Na3AlF6), titanium oxide (TiO2), and potassium tetrafluoroborate (KBF4) in aluminum melt, and B4C microparticles were added directly into the melt. X-ray diffraction (XRD), optical microscope (OM), and scanning electron microscope (SEM) were used to investigate the microstructure and failure mechanism of the samples. Also, Hardness and tensile tests were carried out to test Mechanical Properties. The results showed that addition of B4C first decreased and then increased the ultimate tensile strength compared to the sample without reinforcement. Moreover, the highest value of tensile strength was for the sample containing 2.5 vol.% of B4C and 2.5 vol.% TiB2, which showed a 235% improvement compared to the sample without an amplifier. However, the tensile strength of the sample containing 2.5 vol.% of B4C was reduced by 35% compared to the sample without reinforcement. The results of the Hardness test showed a drop in Properties of the samples containing 2.5% of B4C reinforcement. the highest value of tensile strength was for the sample containing 2.5 vol.% of B4C and 2.5 vol.% TiB2, which showed a 33% improvement compared to the sample without reinforcement.

The low cost Stir Casting is one of the most applicable methods to fabricate Aluminum metal matrix Composites. In this study, Stir Casting technique is utilized to produce Silicon carbide/Aluminum alloy Composite. To achieve a homogeneous and suitable distribution, reinforcing particle surface Properties is investigated by applying various thermal and Mechanical treatments. SiC Oxidation performed at 950˚ C for 1 hour and keeping at 650˚ C for 2 hours as heat treatment. Mechanical treatment comprised milling aluminum and SiC powder. 10% vol. fraction Silicon carbide particles with average size of 2, 10 and 40 microns were gradually added to the aluminum matrix Stirring at 640˚ C. After Stirring, the Composite was cast at 700˚ C in a steel mold. Observing the Composite microstructure using OM and SEM reveals that reinforcing particles are dispersed in the matrix. However, heat treated reinforcing particles at 950˚ C and keeping at 650˚ C leads to fabricate a more homogenous Composite of a specified percentage of reinforcing particles in which particles could be easily wetted by the matrix. In samples with SiC particles milled with Al powder, particles were not desirably bounded and disturbed in the matrix. Oxidation at 950˚ C and keeping at 650˚ C Shows better wettability and distribution of particles. This specimen also has the highest Hardness of 139 HV, indicating the proper bonding of particles and their uniform distribution in the matrix.

In this investigation‚ the Fracture Toughness of A356 containing 15% SiC Composite was studied. Al/SiC Composites have been considered because of their Mechanical and erosion Properties .Low Fracture Toughness in Al/SiC as compared with Aluminium alloys is one of its disadvantage. In this study at first A356 alloy was melted in a smelting electrical furnace then poured into the mould. A356-15% SiC were composed by melting method and mixing continuously (in order not to precipitate SiC to the bottom) in the presence of a nature gas. The melt was poured in a metallic mould, then specimens were cut from the products bars in order to calculate Fracture Toughness according to ASTM. Obtained results for different specimens compared together. In this study Crack Opening Displacement (COD) is used to determine Fracture Toughness rate. KIc was calculated in Composites and compared with that of base alloy. As a result KIc in Composite samples were decreased significantly, debris, Cracks, gas cavity.