Fatigue limit of Y-TZP reinforced with carbon nanotubes (original) (raw)
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Y-TZP reinforced with carbon nanotubes: Synthesis, microstructure and flexural strength
Dental Materials, 2014
The aim of the study was to investigate the flexural and impact strength of 3 commercially available denture base resins after reinforcing them with single walled carbon nanotubes (SWCNT'S). Each acrylic resin was first solubilised in Tetrahydrofuran (THF) and then carbon nanotubes were added in different percentages respectively. A total of 50 specimens were made from each material (Eclipse, Triad Visible light cure (VLC) and Lightplast) following the International Standard Organization (ISO; 1567:1999). Carbon nano tubes were chemically incorporated into the polymer. Charpys impact test and flexural strength analysis was made. Data were analyzed using one way-ANOVA for comparisons. The results revealed a significant rise (p<0.05) in the impact strength and flexural strength of Eclipse (12.5 kj/mm , 128MP) when compared with Triad Visible light 2 cure (VLC) and Lightplast at 2% addition. The flexural strength of each material also increases gradually with increasing percentage of SWCNT's addition. In terms of impact and flexural strengths Eclipse denture base showed better results when compared with the other light cured reinforced denture base acrylic resin. Higher standard deviation values were seen for Eclipse. Reinforcing the acrylic resin is beneficial and significantly affects the material properties.
Ceramics International
Titanium dioxide (TiO 2) nanotubes have been applied to enhance the mechanical and biological properties of dental materials. Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) have been increasingly used in dentistry as a substructure for crowns and fixed partial prostheses. Aside from its optimal clinical results, Y-TZP is prone to failures due to microstructure-related defects introduced in the manufacturing process that may lower its structural and clinical reliability. The purpose of this study was to evaluate the role of the manufacturing process of blanks as well as their original composition modification by addition of TiO 2 nanotubes (0%, 1%, 2% and 5% in volume) while controlling all manufacturing steps. Materials were subjected to a biaxial flexural strength test, a fractographic qualitative analysis by scanning electron microscopy (SEM), a microstructure evaluation in field emission-SEM and X-ray diffraction. Values of flexural strength were subjected to ANOVA, Tukey (α = 0.05) and Weibull statistics. Grain size values were subjected to Kruskal-Wallis and Dunn tests (α = 0.05). Highlights of the results include that for experimental Y-TZP added 2% vol TiO 2 nanotube ceramics presented flexural strength values at 577 MPa and Weibull modulus (m) at 8.1. The addition of TiO 2 nanotubes in different blends influenced experimental Y-TZP properties, leading to lower flexural strength, although they presented higher m than the commercial Y-TZP. Nanotubes also led to bigger grain sizes, more pores and a slight increase in the monoclinic phase, influencing the microstructure of Y-TZP. Y-TZP blank manufacturing control as well as addition of TiO 2 nanotubes led to higher m values and, hence, greater structural reliability.
Yttria-stabilized zirconia (YSZ) is a potential thermal insulating ceramic for high temperature applications (>1000 C). YSZ reinforced with multi-walled carbon nanotubes (MWNTs) was processed via spark plasma sintering to produce dense, crack-free homogeneous sample and avoid any degradation of MWNTs when sintered using conventional routes. Despite porosity, the addition of MWNT has a profound effect in improving the damage tolerance of YSZ by allowing the retention of tetragonal phase. However, at some instances, the crack lengths in the MWNT reinforced YSZ matrices have been found to be longer than the standalone counterparts. Therefore, it becomes inappropriate to apply Anstis equation to calculate fracture toughness values. In this regard, a combined analytical cum numerical method is used to estimate the theoretical fracture toughness and quantitatively analyze the mechanics of matrix cracking in the reinforced composite matrices incorporating the effects of various factors (such as far-field stresses, volume fraction of MWNTs, change in the modulus and Poisson's ratio values along with the increase in porosity, and bridging and phase transformation mechanism) affecting the fracture toughness of YSZ-MWNT composites. The results suggest that the incorporation of far-field stresses cannot be ignored in estimating the theoretical fracture toughness of YSZ-MWNT composites. Published by AIP Publishing. https://doi.org/10.1063/1.4990731
Ceramic Engineering and Science Proceedings, 2010
High temperature mechanical spectroscopy measurements were conducted on carbon nanotubereinforced fine-grained 3Y-TZP ceramics processed by conventional (CS, grain size ~ 350 nm) and spark plasma (SPS, grain size ~ 100 nm) sintering. The mechanical loss spectra are composed of a peak and an exponential background appearing at low frequencies or high temperatures. The SPS samples showed a much higher level of internal friction and lower creep resistance, which can be attributed to the easier grain boundary sliding in nanosize-grained specimens. The addition of carbon nanotubes resulted in a decrease in damping with respect to the high purity of zirconia powder and possibly in a reduction of creep.
Improving the fatigue life of composite by using multiwall carbon nanotubes
Open Engineering, 2023
The fatigue life of polymer materials like epoxy can be improved by using stiffeners such as carbon fiber and/or adding multiwall carbon nanotubes (MWCNTs). This article studies the effect of adding MWCNTs with different ratios (0.5, 1, and 2 wt%) to epoxy and composite (epoxy + 30% carbon fibers). The experimental results of the fatigue test with fully reversed bending stress (with R = −1) showed a maximum increase of 788% in fatigue life when adding 1 wt% MWCNTs to epoxy, while the maximum improvement ratio reaches 2,500% when adding 1 wt % MWCNTs to composite. The best results of fatigue life improvement were observed for samples with MWCNTs of 1 wt%. The material will be transferred from low cycle fatigue (less than 10 5 cycles) to high cycle fatigue (more than 10 5 cycles) by adding 1 wt% of MWCNTs. At the same time, the ratio of MWCNTs of more than 1 wt% (such as 2 wt%) will decrease the fatigue life due to the agglomeration of nanotubes inside the resin and reduce the positive effect of it. These agglomeration points work as a barrier to load transfer and stress concentration points. The numerical model was built to simulate the fatigue test and compare the results with the experimental with a discrepancy value of 7.5%.
Improving Fatigue Performance of GFRP Composite Using Carbon Nanotubes
Fibers, 2015
Glass fiber reinforced polymers (GFRP) have become a preferable material for reinforcing or strengthening reinforced concrete structures due to their corrosion resistance, high strength to weight ratio, and relatively low cost compared with carbon fiber reinforced polymers (CFRP). However, the limited fatigue life of GFRP hinders their use in infrastructure applications. For instance, the low fatigue life of GFRP caused design codes to impose stringent stress limits on GFRP that rendered their use non-economic under significant cyclic loads in bridges. In this paper, we demonstrate that the fatigue life of GFRP can be significantly improved by an order of magnitude by incorporating Multi-Wall Carbon Nanotubes (MWCNTs) during GFRP fabrication. GFRP coupons were fabricated and tested under static tension and cyclic tension with mean fatigue stress equal to 40% of the GFRP tensile strength. Microstructural investigations using scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy were used for further investigation of the effect of MWCNTs on the GFRP composite. The experimental results show the 0.5 wt% and the 1.0 wt% MWCNTs were able to improve the fatigue life of GFRP by 1143% and 986%, respectively, compared with neat GFRP.
Computational Materials Science, 2014
Carbon nanotubes (CNTs) possess extremely high stiffness, strength and resilience, and may provide ultimate reinforcing materials for the development of nanocomposites. CNT reinforced composite materials (CNTRC) can be effectively used in aircraft structures, due to their high strength to weight ratio. Accordingly, several experimental and analytical studies have been performed for evaluating effective mechanical properties of CNT-reinforced polymer matrix. However, several complex issues including sizes and forms of CNTs dispersed in a matrix, their distribution and orientation in the matrix make the simulations of the mechanical behaviour of these composites extremely complicated. One such issue is assessing the effect of nanotube curvature since embedded CNTs seldom remain straight inclusions. Nanotube curvature is often characterized by means of the waviness that accounts for the deviation from the straight particles assumption. In this paper, the effect of waviness of CNT is analyzed using a 3-D nanoscale representative volume element (RVE) based on continuum mechanics, and effective elastic modulus is calculated for two cases namely, a RVE with long CNT (CNT throughout the length of RVE) and a RVE with short CNT (CNT completely inside the RVE). Finite element method is used for the analysis. Further, a theoretical model based on the micromechanics of multi-phase composite and energy principles has also been developed to evaluate effective elastic constants of these RVEs. It is found that the reinforcing capacity of the CNTs reduces drastically even with a small waviness as compared to the straight CNTs. The effect of waviness is much more pronounced in case of long wavy CNT than short wavy CNT. The analysis is finally extended to predict the effective moduli of these composites embedded with completely randomly oriented CNTs of different waviness.
Effect of waviness on the mechanical properties of carbon nanotube based composites
Physica E: Low-dimensional Systems and Nanostructures, 2011
Carbon nanotubes have been regarded as ideal reinforcements of high performance composites with enormous applications. In this paper, effects of wavy carbon nanotubes on mechanical properties such as elasticity and strength aspects are investigated for nanocomposites using a 3-D representative volume element with long and short wavy carbon nanotubes. The carbon nanotube is modeled as a continuum hollow cylindrical shape elastic material with some curvature in its shape. The effect of the waviness of the carbon nanotubes and its parameters are studied. Numerical equations are used to extort the effective material properties for the different geometries of representative volume elements, under axial loading for straight carbon nanotubes. It is observed that waviness significantly reduces the effective reinforcement of the nanocomposites. The effective moduli are very sensitive to the waviness and this sensitivity decreases with the increase of the waviness. In the case of short carbon nanotubes, increasing trend is observed up to a specific value of waviness index. Tensile strength analysis shows a decreasing trend of the strength against the increasing the values of waviness indices. Geometry of the RVE is also found to be affecting the strength of the carbon nanotube reinforced composites. Simulation is applied on the straight carbon nanotubes with the hexagonal representative volume element, and the results are found to be consistent with the rule of mixtures results, which validate the proposed model.