Fabrication of SiCp/6092Al Graded Composite Materials Via ECAP Process

Objective To apply the hydroxyapatite/zirconium oxide(HA/ZrO2) gradient composite material by 3D printing technology, to analyze its ability to repair the defect of femoral shaft of beagle dogs. Methods Bone defect model was prepared in 6-month male beagle by truncating right leg femur after middle full-thickness 15 mm, which was put into the Micro CT scanned for volume, complete data collection, transformation and the post-processing. Then data were imported in CeraFab 7500 photocure 3D printer. Started to print program, formed a composite photosensitive resin in the early embryo, and the further defatted sintering and then used dip-coating HA/ZrO2 gradient composite materials according the parameters. The performance of the HA/ZrO2 gradient materials were taken scanning electron microscopy (SEM), X-ray diffraction analysis and biomechanical experiments. Prepared HA/ZrO2 gradient composite materials and cultured L929 mouse fibroblast cell lines, then MTT method was used to detect the HA/ZrO2 gradient composites cell toxicity in vitro. Sixteen dogs were divided into 4 groups, 4 dogs in each group. Group A: Dogs’ 15 mm middle femur were intercepted with no biological material implanted, as the blank control group; group B, C, D were truncated middle femoral 15, 25 and 35 mm made of bone defect model, and transferred into the corresponding specifications of the HA/ZrO2 gradient composite materials. X-ray scan was taken to observe implanted biomaterials combined with own bone and surrounding callus growth after operation of 2, 4, 8, 12 weeks. Animals were executed and captured the entire length of the femur, then observed specimens implanted in biological materials and the surrounding bone growth conditions after 12 weeks. New bone mass were measured and reconstructed by Micro CT scans. The compressive experiments of femoral specimens were used to measure the ultimate compressive strength. Results The SEM showed that nano HA/ZrO2 gradient composite material made by 3D printing technology had smooth surface and even stable structure. Composite material had a metallurgical bonding and there was no obvious boundary in fracture surface. XRD analysis showed an obvious peak, better crystalline degree and better purity. Mechanical text showed that the ultimate compressive strength was (43.37±2.31) MPa. MTT analysis proved that HA/ZrO2 gradient composite material had no cytotoxicity. Front and lateral X-ray examinations were taken at 2, 4, 8, 12 weeks after operation. In group A, bone nonunion was formed. In group B, continual bony callus were get through and there was no obvious boundary between artificial prosthesis and host bone. At 2, 4 and 8 weeks after operation, continuous callus and new bone growth in group C was slower than group B, but the gap between artificial prosthesis and broken ends was gradually filled with new bone, and the continual bony callus were got through at the week 12. In group D, new bone was formed in a lower speed, and appeared only around the broken ends. The specimens were taken at week 12 after operation, three-dimensional reconstruction of Micro CT showed that per unit volume new bone in group B, C, D were (238.55±19.11) mm3/cm3, (223.31±13.41) mm3/cm3 and (110.83±6.48) mm3/cm3, respectively. There were statistically significant differences among the three groups in statistics analysis (F=156.824, P 0.05). Conclusions The nano HA/ZrO2 gradient composite material artificial prosthesis made by 3D printing technology has reliable biocompatibility and biomechanics that fit the individual treatment principle in clinic. As an ideal substitute for bone tissue, it could well repair femoral bone defect in 35 mm in dogs. Key words: Tissue engineering; Hydroxyapatites; Zirconium; Three dimensional printing technology; gradient composite materials; Animal experimentation; Bone defects

Porous materials have excellent functions in filtration and purification, and gradient composite porous materials enrich the product types of porous materials in the same field. In the preparation of metal-ceramic gradient composite porous materials, the matching relationship between the pore morphology and pore size of the metal porous matrix and the coated powder particles will seriously affect the structure and performance of the ceramic membrane. This work mentions the different size range (60, 100, 200 and 400 mesh) of 316 L stainless steel powder particles as the raw materials which are at different sintering temperatures of 1170, 1200 and 1230 °C, the fabrication of porous 316 L stainless steel substrate which was made by hanging slurry preparation of precursor, at the same time using Ar protection at different sintering temperatures (650, 700, 750 and 800 °C) to the preparation of metal-ceramic composite gradient according to different matrix apertures of porous materials. The pore structure, microstructure and morphology characteristics of different samples both of matrix and functionally gradient composite were analyzed and characterized. On the basis of test of permeability of functionally gradient composite porous materials, this kind of composite gradient porous material can be excellent at part of permeability which matrix was made by 400 mesh 316 L stainless steel powder particles at sintering temperature of 1230 °C and then dealed with the process of hanging slurry to became the precursor which ceramic membrane was prepared at sintering temperature of 650 °C. Maximum aperture of the porous substrate filtration precision under the combination of ceramic membrane layer can be increased by 96.3%. By observing the change of pore morphology of porous matrix, this paper aims to make a research of influence of sintering temperature and powder particles size on permeability of the functionally gradient composite porous materials, and also provide a reference for improving the filtration accuracy of existing porous materials.

Modeling and stress analysis of aluminium alloy based composite pressure vessel through ANSYS software

Objectives: The objective of the present study is to prepare Al6061-Gr-SiChybrid composites by stir casting route and the effect of Equal Channel Angular Pressing (ECAP) on the microstructure and mechanical properties of Al6061-Gr-SiC hybrid composites will be evaluated. Methods: In the present study, Al6061 is selected as matrix material. The reinforcement materials chosen are graphite (Gr) and Silicon carbide (SiC) particles of 10-30 μm size. The hybrid composites have been prepared by stir casting route in which the amount of Gr particles are kept at 3wt% and SiC particles are varied from 2-10wt% in steps of 2wt% . The cast hybrid composites are subjected to annealing treatment at 400oC for 4 hours and specimens have been prepared from these composites for ECAP process. The ECAP process was carried out at room temperature using a die with channel angle of 120o and Bc route was adopted for successive passes. The influence of ECAP on microstructure and mechanical properties of Al-Gr-SiC hybrid composite was evaluated. Findings: The microstructural study revealed that the composites are free from defects and also the distribution of reinforcement particles in the matrix are fairly uniform. Significant improvement in micro hardness and tensile strength was observed as the wt% of SiCp increases in as cast Al6061-Gr- SiC hybrid composites. After ECAP process, the size and distribution of the reinforcement particles are not changed but significant reduction in the grain size of the matrix alloy was observed. The micro hardness and tensile test results revealed that, there is a significant improvement in the micro hardness and the Ultimate tensile strength of ECAP processed hybrid composites. The enhancement in mechanical properties are mainly attributed to the grain refinement of the matrix alloy and strain hardening of hybrid composite materials by ECAP process. Applications: The ECAP process had a profound effect in enhancing the mechanical properties of hybrid composites. These composite materials have great impact in automobile, military and aerospace industries.

Investigation of mechanical and erosive behaviour of the Al 6061-SiC composites fabricated by stir casting

Investigation on microstructure, mechanical, and tribological performance of Cu base hybrid composite materials

Aluminum (Al) matrix composite materials reinforced with graphite flakes (GF) and pitch-based carbon fibers (CF) were fabricated by solid–liquid phase sintering with a small amount of Aluminum–Silicon eutectic alloy (Al-12 wt%Si). The amount of Al–Si is optimized for a carbon content of 50 vol% in order to achieve, in the plane of GF reinforcement, a higher thermal conductivity (TC) and a lower coefficient of thermal expansion (CTE) compared to identical composite material fabricated by conventional powder metallurgy route. Al/(GF + CF) composite materials were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray microscopy and X-ray tomography in order to highlight the distribution of the Al–Si liquid phase and the formation of a carbon network in the aluminum matrix. A small amount of CF allows to control the through-plane CTE without affecting significantly the in-plane TC of the Al-C composites. The (GF + CF) mixture and the solid–liquid phase sintering allow to achieve a TC of 410 W/m K (in-plane direction) and a CTE of 2.4 × 10−6/K (trough-plane direction), which is, for example, applicable for lightweight heat sink material.

Currently used discrete fillers of cast aluminum matrix composite antifriction materials in most cases are characterized by high hardness, leading to increased wear of steel pairs of friction, which makes the search for new fillers urgent. Due to the formation of titanium aluminosilicates in the Al-Ti-Si system and the insignificant solubility of silicon and titanium in aluminum, it was suggested that it is possible to obtain composite materials based on them by the in-situ method or by synthesizing reinforcing materials in a liquid metal matrix. The introduction of titanium in the amount of 10 wt. % into the melts of Al-10÷20 wt. % Si at 700, 800 and 900 °C and subsequent isothermal holding the composite materials are synthesized. By melting in the range of 1000-1100 °C the Al-10÷25 wt. % Si-5÷15 wt. % Ti materials are obtained The phase composition of these materials and the content of elements in the primary phases formed in the aluminum matrix, the hardness of materials obtained by melting is determined. Studies of the formation of phases in the Al-Si-Ti system showed that under the conditions of their synthesis in the liquid phase as a result of reaction-diffusion, a large spectrum of aluminosilicates is formed, which are characterized by a dispersed structure. Under such conditions, since the processes are far from equilibrium, the formation of phases that cannot form during crystallization from the melt under conditions of its cooling is possible. This makes it possible, by varying the synthesis temperature and composition of the charge materials, in wide intervals, to change the properties of the resulting aluminum-matrix composite materials. Similar composite alloys that form during crystallization from the melt are characterized by a more coarse-crystalline structure and a substantially smaller spectrum of silicides, which obviously impairs their properties. The tests of the composite material of composition 85 % Al-15 % Si – 10 % Ti for friction-wear showed that it is characterized by high tribological characteristics. A significant advantage of the materials of the Al-Si-Ti system is the absence of solid phases capable of damaging the surface of the counter body made of steel. This makes promising further studies of the tribotechnical characteristics of the composites of this system.

Research on preparation and characterization of Ti-Ti5Si3 gradient composite porous material via in-situ reactive process

The effectiveness of composite materials with the addition of activated carbon produced from biomaterial with a new application on aluminum-based composite materials was investigated in this study. Activated carbon was produced from the peanut shells via the chemical activation method and the obtained activated carbon was mixed with aluminum and composite material. For the characterization of the composite material obtained, XRD and SEM–EDS optical photographs were assessed in the experimental process. According to Vickers Hardness and Dynamic Micro Hardness results, the sample with the hardness value of 2% AC added had the highest hardness value. The value of the elastic modulus was found to be 9.59GPa with an increase of 3.4 times compared to aluminum with 2% activated carbon addition. This increases with activated carbon quantity, and weakens the composite structure due to weak van der waals interaction with aluminum, which reduces hardness; therefore, the best ratio of the activated carbon reinforcement to the aluminum matrix was obtained at 2% activated carbon addition.

Particle cracking is one of the key elements in the fracture process of particulate-reinforced metal-matrix composite (MMC) materials. The present study quantitatively examined the amount of new surface are created by particle cracking and the number fraction of cracked particles in a series of SiC-reinforced aluminum-matrix composite materials. These composite materials were fabricated by liquid-phase sintering and contained 9 vol pct of 23, 63, or 142 {micro}m SiC. The matrix properties were varied by heat treating to either an underaged or peak-aged condition. In general, the new surface area created by particle cracking (S{sub V}) and the number fraction of cracked particles (F{sub no}) were linearly dependent on the local strain along the tensile specimen. Multiple cracks were frequently observed in the composites containing large particles. It was found that the new surface area created by particle cracking per unit strain was higher for the case of high-strength matrices and was not systematically affected by particle size within the range studied. The number fraction of cracked particles was affected by both particle size and matrix strength. A higher number fraction of particles cracked in the composites reinforced with large particles and with high matrix yield strengths. These results are interpretedmore » in terms of the size of the particle defects, which is a function of particle size, and the critical flaw size necessary to crack a given particle, which is a function of the stress on the particle. The new surface area created by cracking and the fraction of cracked particles were related and are in good agreement for the large and medium sized particles.« less

High specific strength, stiffness, excellent environmental fatigue resistance and low weight remain the winning alliance that impels fibrous composite materials into new arenas, but other properties are also equally important. Fibrous reinforced plastics (FRPs) offer good vibrational damping and a low coefficient of thermal expansion, characteristics that can be engineered for specialized applications. Commercial composites are used in large markets such as automotive components, boats, consumer goods, and corrosion-resistant industrial parts. Advanced composites, initially developed for military aerospace applications, offer performance superior to that of conventional structural metals and now find applications in satellites, aircraft, and sporting goods and in the energy sector in oil and gas exploration and wind turbine constructions. Cryogenic applications of polymeric fiber composites are mainly in superconductivity, space technology, and handling of liquefied gases. By contrast, because of the heterogeneous nature and anisotropic behavior of FRPs, a structural designer faces challenges in predicting the integrity and durability of FRP laminates during service periods. Polymer composites soften, creep, and distort when heated to high temperatures (>100 °C), accompanied by collapse of free volume as the molecular adjustments take place. This can result in buckling and failure of load-bearing composites structures. Severe environmental exposure affects the physical and mechanical properties of polymeric composite materials, resulting in an undesirable degradation and damage.

At present, the growing needs and design requirements with significant weight savings as well as high strength-to-weight ratio as compared to conventional materials raised a growing interest towards composite materials. Metal matrix composites (MMCs) are extensively used in fields like aerospace, automobiles and army-defence applications due to their high specific strength, low coefficient of thermal expansion, wear resistance, high durability, excellent physical and mechanical properties. The filler reinforcements like SiC, TiC, Al2O3 improve the stiffness, specific strength, creep properties of MMCs, but the presence of such hard reinforcements makes MMCs difficult to machine through conventional machining processes. Wirecut electrical discharge machining (WEDM) is highly precise thermoelectrical process and is considered ideal for machining very hard materials, intricate geometries and tooling. This paper reviews the researches in WEDM of metal matrix composites and the relation between different process parameters like pulse on time, pulse off time, wire feed rate,voltage, wire tension, dielectric flow rate on the machining performances such as material removal rate (MRR), Kerf widthand surface roughness (SR). The future trends in WEDM researches were also recommended in this paper.

Composite materials are often utilized in weight-critical applications, owing to their higher specific strength\stiffness characteristics. In addition, composite materials also possess qualities such as better corrosion resistance, lower coefficient of thermal expansion, etc., which makes them a potential material choice for riser systems in high pressure and high temperature environments. However, design certification of risers using the finite element method requires modeling and analysis techniques, centric to the multi-layered nature of composite structures. Riser systems, owing to their high aspect ratios, have traditionally been modeled with beam elements. The methodology for extracting the stress results and certifying a metallic riser is well established in the Oil and Gas industry. However, for analyzing a composite riser, three-dimensional shell or hexahedral elements are generally required to capture the through-the-thickness (or pipe cross-sectional) variation of structural response, especially in critical regions such as touchdown point, pipe-intersection zones, etc. In this paper, a method for analyzing a detailed local model (discretized with shell\hexahedral elements) driven by results from a global model (meshed with beam elements) is presented. The global model captures the structural response whereas the local model provides cross-sectional stress\strain information for individual layers. Although the method is illustrated for a composite riser, it is also applicable to metallic structures.

The researches on the development of composite material propeller with outstanding damping effects have been actively attempted for the reduction of radiation noise of underwater vehicle propeller. Composite material suitable for the flexible propeller has the following advantages, such as high specific strength and specific stiffness, low thermal expansion coefficient, high resistance against environmental deterioration, low possibility of corrosion due to cavitation, nonoccurrence of rapid fracture due to fatigue, easy molding of complicated shape, easy repair maintenance and low production costs, etc. For the confirmation of optimal fiber array structures of composite material for the production of the flexible propeller blades, in this study, mechanical characteristics of its specimens according to materials were obtained and structural characteristics of propeller blade were also examined according to materials and stacking fiber arrays.