Academic literature on the topic 'Toughening techniques'
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Journal articles on the topic "Toughening techniques"
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Clarke, D. R., and B. Schwartz. "Transformation toughening of glass ceramics." Journal of Materials Research 2, no. 6 (December 1987): 801–4. http://dx.doi.org/10.1557/jmr.1987.0801.
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The utilization of transformation toughening has hitherto been restricted to increasing the fracture resistance of polycrystalline ceramic materials. Although a number of investigators have attempted to extend the concept to toughening glasses and glass ceramics with tetragonal zirconia, no successful reports have been published. It is argued that the approaches employed are inevitably limited primarily because they do not take into account the necessity of nucleating the tetragonal-to-monoclinic transformation away from the crack tip itself. By concentrating on the nucleation event and using standard ceramic processing techniques, it has been demonstated that transformation toughening can be used to increase the toughness of glass-ceramic materials, and this approach is illustrated by increasing the fracture toughness of a cordierite glass ceramic.
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Shah, S. P., and C. Ouyang. "Toughening Mechanisms in Quasi-Brittle Materials." Journal of Engineering Materials and Technology 115, no. 3 (July 1, 1993): 300–307. http://dx.doi.org/10.1115/1.2904222.
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Fracture processes in cement-based materials are characterized by a large-scale fracture process zone, localization of deformation, and strain softening. Many studies have been conducted to understand the toughening mechanisms of such quasi-brittle materials and to theoretically model their nonlinear response. This paper summarizes two innovative experimental techniques which are being developed at the ACBM Center to better define the fracture process zone in cement-based materials. A brief summary is also given of two types of theoretical approaches which attempt to simulate some of the observed nonlinear fracture response of these materials.
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Gunnison, Katie E., Mehmet Sarikaya, and Ilhan A. Aksay. "Toughening mechanisms in abalone shell." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 196–97. http://dx.doi.org/10.1017/s0424820100174114.
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Abalone shell (Haliotis Rufescens) is a naturally ocurring ceramic/polymer composite material. The system displays a unique laminated structure of calcium carbonate (aragonite) crystals in a matrix of biological macromolecules. The CaCO3 crystals and the organic matrix are arranged in a miniature “brick and mortar” structure referred to as nacre. Figure 1 is a TEM bright field micrograph illustrating the high degree of order observed in this microstructure.Although the nacre region of the shell is more than 95% CaCO3 by volume, the natural matrix material and the arrangement of the microstructure lead to a substantial increase in the observed mechanical properties. Mechanical tests performed on the nacre region show a fifty-fold increase over that of pure bulk CaCO3 (Fig. 2), which also compares with other ceramic and cermet systems.Vickers microhardness testing was performed on samples polished for optical microscopy. Crack propagation features were observed by standard SEM techniques and analyzed in an attempt to identify the possible toughening mechanisms that are operating in the nacre structure. The cracks generally travel by a tortuous path, often displaying microcracks and crack branching. However, these mechanisms alone are not sufficient to account for the observed mechanical properties.
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McCoy, M. A. "Crystallization of MgO • Al2 • SiO2 • ZrO2 glasses." Proceedings, annual meeting, Electron Microscopy Society of America 44 (August 1986): 440–41. http://dx.doi.org/10.1017/s0424820100143778.
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Transformation toughening by ZrO2 inclusions in various ceramic matrices has led to improved mechanical properties in these materials. Although the processing of these materials usually involves standard ceramic powder processing techniques, an alternate method of producing ZrO2 particles involves the devtrification of a ZrO2-containing glass. In this study the effects of glass composition (ZrO2 concentration) and heat treatment on the morphology of the crystallization products in a MgO•Al2•SiO2•ZrO2 glass was investigated.
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Llanes. "In-Depth Understanding of Fatigue Micromechanisms in Cemented Carbides: Implications for Optimal Microstructural Tailoring." Metals 9, no. 9 (August 23, 2019): 924. http://dx.doi.org/10.3390/met9090924.
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The fatigue mechanics and mechanisms of cemented carbides (composites usually referred to as hardmetals) are reviewed. The influence of microstructure on strength lessening and subcritical crack growth for these ceramic-metal materials when subjected to cyclic loads are highlighted. The simultaneous role of the ductile metallic binder as a toughening and fatigue-susceptible agent for hardmetals results in a tradeoff between properties measured under monotonic and cyclic loading: fracture strength and toughness on one hand, as compared to fatigue strength and crack growth resistance on the other one. Toughness/fatigue–microstructure correlations are analyzed and rationalized on the basis of specific crack–microstructure interactions, documented by the effective implementation of advanced characterization techniques. As a result, it is concluded that the fatigue sensitivity of cemented carbides may be reduced if either toughening mechanisms beyond ductile ligament bridging, such as crack deflection, are operative, or strain localization within the binder is suppressed. In this regard, grades exhibiting metallic binders of a complex chemical nature and/or distinct microstructural assemblages are proposed as options for effective microstructural tailoring of these materials.
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Tatarko, Peter, Štefánia Lojanová, Ján Dusza, and Pavol Šajgalík. "Fracture Toughness of Si3N4 Based Ceramics with Rare-Earth Oxide Sintering Additives." Key Engineering Materials 409 (March 2009): 377–81. http://dx.doi.org/10.4028/www.scientific.net/kem.409.377.
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Fracture toughness of hot-pressed silicon nitride and Si3N4+SiC nanocomposites prepared with different rare-earth oxides (La2O3, Sm2O3, Y2O3, Yb2O3, Lu2O3) sintering additives have been investigated by Chevron Notched Beam, Indentation Strength and Indentation Fracture techniques. The fracture toughness values of composites were lower due to the finer microstructures and the lack of toughening mechanisms. In the Si3N4 with higher aspect ratio (Lu or Yb additives) crack deflection occurred more frequently compared to the Si3N4 doped with La or Y, which was responsible for the higher fracture toughness.
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Jervis, T. R., J.-P. Hirvonen, M. Nastasi, and H. Kung. "Tribology and mechanical properties of excimer laser-processed Ti–Si3N4 surfaces." Journal of Materials Research 10, no. 8 (August 1995): 1857–60. http://dx.doi.org/10.1557/jmr.1995.1857.
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Titanium films were mixed, using excimer laser radiation, into the surface of bulk Si3N4 materials. The tribological and mechanical properties of these surfaces were then evaluated using pin-on-disk and nanoindenter techniques, respectively. Reduced friction and a change in the wear mechanism that resulted in a more benign failure mode were observed. These results are interpreted as resulting from the establishment of a transfer film, changes in the compliance of the surface which reduces instantaneous stresses in the surface, and toughening of the surface, all results of the laser process.
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Zhang, Kai, Jing Hui Fan, and Yan Ma. "Preparation of Impact Resistance Epoxy Resin Encapsulating Materials." Applied Mechanics and Materials 327 (June 2013): 18–22. http://dx.doi.org/10.4028/www.scientific.net/amm.327.18.
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According to research requests of encapsulating materials used in anti-impact precision electron apparatus parts, the materials system was designed on the relation of mechanics performance and techniques properties. Then epoxy resin E-51 was toughening modified with a kind of self-synthesized polyester epoxy resin which had liquid crystal groups. The results showed that the optimized epoxy resin encapsulating materials has high compression strength and favorable operating properties. The impact strength of prepared epoxy resin encapsulating materials increased 4.0 times, and the gel time at room temperature was over 100 minutes.
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Xu, Yun Yun, Tao Zhang, Zhen Rong Lin, Shan Dan Zhou, and Xin Xu. "Advances in Research of Carbon Fiber Reinforced Composite Materials." Advanced Materials Research 332-334 (September 2011): 1607–10. http://dx.doi.org/10.4028/www.scientific.net/amr.332-334.1607.
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Carbon fibers combine low weight and exceptional mechanical properties,making them ideal reinforcements forpolymer composite materials. An attempt has been made to review and analyze the development and problems made during last few decades in the field of carbon fiber reinforced polyamide composites. The recent advance of research, structure and property, the advanced techniques were summarized in this paper. In accordance with the hot spots of the research, the interface behavior, reinforcement and toughening of this type of material were expounded specially. Finally, the prospect and development of this composite were analyzed.
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Zhao, Hong Ping, Robert Kwok Yiu Li, and Xi Qiao Feng. "Experimental Investigation of Interlaminar Fracture Toughness of CFRP Composites with Different Stitching Patterns." Key Engineering Materials 297-300 (November 2005): 189–94. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.189.
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Through-thickness stitching is one of the most effective techniques to improve the delamination resistance of composite laminates. The effects of two different stitching patterns on the mode-I interlaminar fracture toughness of unidirectional carbon fiber reinforced plastics (CFRP) are examined experimentally in the present paper by using the double cantilever beam (DCB) test method. It is found that the zigzag stitching pattern results in a better toughening effect than the straight line pattern, and that the stitching density also has a considerable influence on the mode-I fracture toughness.
Books on the topic "Toughening techniques"
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Hayes, Brian S., and Luther M. Gammon. Optical Microscopy of Fiber-Reinforced Composites. ASM International, 2010. http://dx.doi.org/10.31399/asm.tb.omfrc.9781627083492.
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Optical Microscopy of Fiber-Reinforced Composites discusses the tools and techniques used to examine the microstructure of engineered composites and provides insights that can help improve the quality and performance of parts made from them. It begins with a review of fiber-reinforced polymer-matrix composites and their unique microstructure and morphology. It then explains how to prepare and mount test samples, how to assess lighting, illumination, and contrast needs, and how to use reagents to bring out different phases and areas of interest. It also presents the results of several studies that have been conducted using optical microscopy to gain a better understanding of processing effects, toughening approaches, defects and damage mechanisms, and structural variations. The book includes more than 180 full-color images along with clear and concise explanations of what they reveal about composite materials and processing methods. For information on the print version, ISBN 978-1-61503-044-6, follow this link.
Book chapters on the topic "Toughening techniques"
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Qing-Ping, Sun, Huang Yong, Lin Shu-Tian, and Si Wen-Jie. "Toughening Investigation of Mode III Crack by Holographic Interference Technique." In 4th International Symposium on Ceramic Materials and Components for Engines, 524–28. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2882-7_55.
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Wu, Jingshen, Chi-Ming Chan, and Yiu-Wing Mai. "Study on Morphology and Toughening Mechanisms in Polymer Blends by Microscopic Techniques." In Polymer Blends and Alloys, 505–48. Routledge, 2019. http://dx.doi.org/10.1201/9780203742921-18.
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Bogomol, Iurii, and Petro Loboda. "Directionally Solidified Ceramic Eutectics for High-Temperature Applications." In MAX Phases and Ultra-High Temperature Ceramics for Extreme Environments, 303–22. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-4066-5.ch010.
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The processing techniques, microstructures, and mechanical properties of directionally solidified eutectic ceramics are reviewed. It is considered the main methods for preparing of eutectic ceramics and the relationships between thermal gradient, growth rate, and microstructure parameters. Some principles of coupled eutectic growth, main types of eutectic microstructure and the relationship between the eutectic microstructure and the mechanical properties of directionally solidified eutectics at ambient and high temperatures are briefly described. The mechanical behavior and main toughening mechanisms of these materials in a wide temperature range are discussed. It is shown that the strength at high temperatures mainly depends on the plasticity of the phase components. By analyzing the dislocation structure, the occurrence of strain hardening in single crystalline phases during high-temperature deformation is revealed. The creep resistance of eutectic composites is superior to that of the sintered samples due to the absence of glassy phases at the interfaces, and the strain has to be accommodated by plastic deformation within the domains rather than by interfacial sliding. The microstructural and chemical stability of the directionally solidified eutectic ceramics at high temperatures are discussed. The aligned eutectic microstructures show limited phase coarsening up to the eutectic point and excellent chemical resistance. Directionally solidified eutectics, especially oxides, revealed an excellent oxidation resistance at elevated temperatures. It is shown sufficient potential of these materials for high-temperature applications.
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Saitta, Lorena, Eugenio Pergolizzi, Claudio Tosto, Claudia Sergi, and Gianluca Cicala. "Fully-Recyclable Epoxy Fibres Reinforced Composites (FRCs) for Maritime Field: Chemical Recycling and Re-Use Routes." In Progress in Marine Science and Technology. IOS Press, 2022. http://dx.doi.org/10.3233/pmst220010.
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The maritime transport is guilty for about 2.5% of global greenhouse gases emission, since 940 million tonnes of CO2 are emitted around every year. Moreover, even though now the 96% of ships can be recycled, current recycling practices cause negative environmental impacts. Indeed, researches carried out on ‘ships graveyard’ showed a concentration of petroleum hydrocarbons 16,793% higher than at the control. Epoxy Fibres Reinforced Composites (FRCs) are sustainable candidates in this field. In fact, having the FRCs structures a light weight, fuel-efficient ships can be built. The global epoxy composites market size was valued at USD 25.32 billion in 2019 and is expected to expand at a compound annual growth rate (CAGR) of 6.2% from 2020 to 2027. In this sense, in the next few years, the market is expected to rapidly replace conventional materials with epoxy composites in several fields, including the marine one. However, concerns about their non-recyclability are rising more and more. In this study, by following a twofold “design for recycling” and “design from recycling” approach the chemical recycling process for thermoset polymer composites developed by Connora Technologies (California, USA) was considered as solution to overcome this issue. Moreover, the adoption of natural fibres, i.e. flax, and bio-based epoxy resin was used as environmentally-friendly solution to even avoid the use of petroleum based raw materials. To follow the first approach, i.e. “design for recycling”, Flax FRCs with bio-epoxy matrices were first produced via hand lay-up with vacuum bagging. Next, they were chemically treated to obtain a recycled thermoplastic (rTP). Then moving on the “design from recycling” approach, a reuse strategy was developed by exploiting the Electrospinning technique and producing electrospun fibers suitable for the interlaminar toughening of composite laminates.
Conference papers on the topic "Toughening techniques"
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Tiano, Thomas, Margaret Roylance, Benjamin Harrison, and Richard Czerw. "Intralaminar Reinforcement for Biomimetic Toughening of Bismaleimide Composites Using Nanostructured Materials." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81689.
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Many conventional composite materials are composed of multiple layers of continuous fiber reinforced resin produced by lamination of b-staged prepreg and subsequent cure. These materials exhibit very high strength and stiffness in the plane, dominated by the properties of the fibers. The Achilles heel of such composites is the interlaminar strength, which is dependent on the strength of the unreinforced resin, often leading to failure by delamination under load. Current methods for increasing the interlaminar shear strength of composites consist of inserting translaminar reinforcement fibers through the entire thickness of a laminated composite, such as z-pin technology developed by Foster-Miller [1]. While effective, this technique adds several processing steps, including ultrasonic insertion of the z-pins into the laminate, subsequently causing a significant cost increase to laminated composites. Described in this paper is a process utilizing single-walled carbon nanotubes (SWNTs) and vapor grown carbon nanofibers as reinforcing elements promoting interlaminar shear strength and toughness in carbon fiber/bismaleimide (BMI) resin composites. The resulting composites mimic the natural reinforcing mechanism utilized in insect cuticles. Three different methods of increasing the affinity of these carbon nanofillers for the BMI matrix were explored. The mechanical properties of these composites were assessed using end notch flexure testing. The results indicated that including nanofiller at the laminae interface could increase the interlaminar shear strength of carbon fiber/BMI composites by up to 58%. SEM micrographs revealed that the nanofiller successfully bridged the laminae of the composite, thus biomimicking the insect cuticle. Composite fabrication techniques developed on this program would have a wide variety of applications in space and aerospace structures including leading and trailing edges of aircraft wings.
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SHEPHERD, MEGAN, KAMRAN MAKARIAN, GIUSEPPE PALMESE, NICHOLAS BRUNSTAD, and LESLIE LAMBERSON. "FRACTURE ANALYSIS OF RUBBER TOUGHENED ADDITIVELY MANUFACTURED THERMOSETS." In Thirty-sixth Technical Conference. Destech Publications, Inc., 2021. http://dx.doi.org/10.12783/asc36/35808.
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This study explores the role of rubber toughening on the dynamic fracture behavior of additively manufactured (AM) high-performance thermosetting polymers formed through digital light processing (DLP). Using DLP to create these polymers allows for rapid, agile manufacturing of prototypes meeting the lightweight and building speed requirements of relevance to military mission applications. This method also provides flexibility in part complexity while maintaining relatively high isotropy compared to traditional AM techniques. Previous work has demonstrated a dependence of these DLP specimens on print layer orientation and loading rate, prompting further investigation into other manufacturing parameters to improve toughness [1]. This study examines the role of rubber toughening on the quasi-static and dynamic fracture behavior of bis-GMA thermosets. Current literature largely reports on quasi-static behavior of DLP specimens, although dynamic conditions are more applicable to many realistic loading scenarios and extreme environments often seen in defense applications. Dynamic experiments leverage a unique long bar striker device that impacts a specimen opposite a pre-crack, sending a stress-wave driven load to initiate a dynamic Mode-I (opening) fracture event. Full-field displacement data ahead of the propagating crack is obtained using ultra high-speed imaging combined with 2D digital image correlation (DIC). An elastodynamic solution following the principles of dynamic fracture mechanics extracts the stress intensity factor (SIF) using a least squares fit at crack initiation and a Newton-Raphson scheme for crack propagation. The rubber toughened thermosets in this study exhibited a rate dependence in fracture toughness with the quasi-static SIF being 1.20 MPa and the dynamic SIF being 0.41 MPa .
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Neufuss, E., Turunen Dyshlovenko, T. Varis, J. Keskinen, T. Fäll, and S.-P. Hannula. "Improved Mechanical Properties by Nanoreinforced HVOF-Sprayed Ceramic Composite Coatings." In ITSC2006, edited by B. R. Marple, M. M. Hyland, Y. C. Lau, R. S. Lima, and J. Voyer. ASM International, 2006. http://dx.doi.org/10.31399/asm.cp.itsc2006p0531.
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Abstract HVOF thermal spraying has been developed to deposit dense ceramic coatings with improved protective properties for various applications. Even though HVOF coatings are much denser as compared to ordinary plasma sprayed coatings, the coating properties are inferior as compared to bulk ceramics because of pores and microcracks, which influence adversely the coating properties, i.e. toughness, hardness and wear resistance. One strategy to improve the properties of the coatings is to decrease the grain size of the ceramic phase and to add toughening elements to the microstructure. Nanocrystalline coatings have been found to offer better thermal shock resistance, lower thermal conductivity and better wear resistance than their conventional counterparts. In this paper we describe the development of nanocrystalline ceramic composite coatings, where the grain size of ceramic has been decreased and a few percents of alloying element has been added in order to toughen the coating. Dense nanostructured alumina coatings alloyed with Ni and ZrO2 nanosized particles were manufactured by HVOF spraying by using HV2000 spray gun. Mechanical properties, especially elastic modulus and relative fracture toughness were studied. Used techniques were instrumented nanoindentation and KIC evaluation. As a result coatings with nearly 100% improvements in relative fracture toughness were produced for nanoreinforced alumina composite coating. Results are compared with the microstructure, hardness and abrasive wear resistance of the coatings.
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Zhao, J., and X. Ai. "Failure Modes and Mechanisms of Functionally Gradient Ceramic Tools With High Thermal Shock Resistance." In ASME 2006 International Manufacturing Science and Engineering Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/msec2006-21056.
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As cutting tool materials, ceramics posses high hardness, wear resistance, heat resistance and chemical stability, with less deformation or dissolution wear in cutting processes. In spite of the advances in strengthening and toughening of ceramic tool materials as well as the improved processing techniques, their applications in intermittent cutting operations are still restricted by their intrinsic drawbacks such as lower strength, lower fracture toughness and lower thermal shock resistance. The introduction of the concept of functionally gradient materials (FGM) into the design and fabrication of ceramic cutting tool materials provides an approach to improving the thermomechanical properties of ceramic tool materials. However, the investigations on the thermal shock resistance evaluation of FGMs for cutting tool applications have been very few, with most work concentrating on the design, fabrication and evaluation of heat-shielding FGMs for space applications. A strength-based fracture criterion for thermal shock resistance evaluation of FGM ceramics is formulated in the present paper, based on which the design rules for FGM ceramics with high thermal shock resistance are presented. An Al2O3/TiC and an Al2O3/(W, Ti)C functionally gradient ceramic tool materials were consequently designed and fabricated by using hot pressing technique. Their cutting performance, failure modes and mechanisms were investigated via a series of intermittent cutting experiments in comparison with those of common ceramic tools. The results revealed improved tool lives of the FGM tools over that of the corresponding common ceramic tools with the same composition systems. The FGM tools exhibited similar wear and chipping characteristics to that of common ceramic tools at initial and normal cutting stages, but different failure modes from that of common ceramic tools. The failure of common ceramic tools was mainly caused by thermal shock and thermal fatigue, whereas the failure mechanisms of the FGM tools were mainly the mechanically induced wear and mechanical fatigue in virtue of their improved thermal shock resistance.
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Moshkelgosha, Ehsan, and Mahmood Mamivand. "Anisotropic Phase-Field Modeling of Crack Growth in Shape Memory Ceramics: Application to Zirconia." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-11695.
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Abstract Shape memory ceramics (SMCs) are promising candidates for actuators in extreme environments such as high temperature and corrosive applications. Despite outstanding energy dissipation, compared to metallic shape memory materials, SMCs suffer from sudden brittle fracture. While the interaction of crack propagation and phase transformation in SMCs have been subject of several experimental and theoretical studies, mainly at macroscale, the fundamental understanding of the interaction of crack propagation dynamics with evolving martensitic transformation is poorly understood. In this work we use the phase field technique to fully couple the martensitic transformation to the variational formulation of brittle fracture. The model is parameterized for zirconia which experiences tetragonal to monoclinic transformation during crack propagation. For the mode I of fracture, opening mode, crack shows an unusual propagation path which indicates the effect of phase transformation on crack path. The model is efficiently capable of predicting the crack initiation as well as propagation. The results show the dramatic effect of phase transformation on fracture toughening and crack propagation path.
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Wu, Shih-Jeh, Ching-An Jeng, and Chen-Ming Kuo. "Ultrasonic Evaluation of Ceramics With Micro-Cracks." In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1961.
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Materials used in high-pressure vessels may be subjected to rapid temperature change, which may induce micro-cracks on the surface and into material. The growth of micro-cracks is detrimental to facility life. Chromium carbide (Cr3C2) has been proved to be a potential structural material for toughening alumina in biomedical and industrial applications because of its high Young’s modulus and erosion resistance. On the other hand, TiC/Al2O3 composite has been used as a magnetic head slider due to its good wear resistance and mechanical strength, and potentially could be an excellent lining material. In this study we thermally shocked ceramic material in disc shape to create different degrees of micro-cracking and use ultrasound attenuation technique to evaluate the damage. This includes narrow band tone burst at different frequency. The results showed significant dependence between ultrasonic attenuation and shock temperature. Corresponding SEM pictures show although the size of micro-crack doesn’t change, the depth of the micro-cracks increases. It is demonstrated that ultrasonic attenuation proves to be a reliable tool for evaluating micro-fractures in solids.
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Hossain, Mohammad K., Md Mahmudur R. Chowdhury, Kazi A. Imran, Mahmud B. Salam, Mahesh Hosur, and Shaik Jeelani. "Durability Study of Low Velocity Impact Responses of Conventional and Nanophased CFRP Composites Exposed to Seawater." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65671.
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The effect of nanoclay on the degradation of low velocity impact responses of carbon fiber reinforced polymer (CFRP) composites manufactured by the vacuum assisted resin transfer molding (VARTM) process is experimentally investigated with and without exposure to seawater for marine applications. Nanoclay was dispersed into the matrix by using magnetic stirring. Samples (100 mm by 100 mm) exposed to seawater for 0, 6, and 12 months in laboratory conditions were impacted at 20, 30, and 40 J energy levels using a Dynatup8210. The damage sustained by the samples was evaluated by a thermographic imaging technique. Comparisons between conventional and nanophased CFRP composites both in conditioned and unconditioned cases were made in terms of peak force, absorbed energy, deflection, delamination area, and specific delamination energy. Water absorption was observed to be reduced due to nanoclay infusion. After 12 months of exposure to seawater 2% nanophased samples absorbed 0.39% moisture whereas control samples absorbed 0.67% moisture. Impact strength, toughness, and energy absorption decreased with increasing conditioning time by weakening the bond between the fiber and matrix and softening the matrix materials. However, reduction in properties is significantly extenuated by the incorporation of nanoclay in the matrix. Specific delamination energy (SDE) is observed to be higher in the nanophased CFRP compared to that of the conventional one at different aging periods indicating an enhanced toughness in the nanophased composites. The larger and stronger interfacial area produced by the nanoclay inclusion has been found to facilitate more energy absorption in the nanophased sample compared to the conventional one. Furthermore, nanoclay reduced the development of delamination by arresting the crack propagation path or by toughening the matrix. It is concluded that the excellent barrier capacity, higher surface area, and high aspect ratio of nanoclay are responsible for the superior performance of CFRP composites, which in turn, enhances the durability of composites.
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John, Mathew, Raghu V. Prakash, and Raman Velmurugan. "The Inter-Laminar Fracture and Mechanical Behavior of Nano-Alumina Modified Glass Fiber/ Epoxy Composite." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-87791.
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This paper presents the effect of addition of nano-alumina particles on the fracture properties of glass fiber reinforced plastic (GFRP) composite laminates. Epoxy resin is the most commonly used polymer matrix for advanced composite materials in view of its ability to adhere to a wide variety of fillers; on curing, they provide excellent stiffness and dimensional stability. However the highly cross linked epoxy often behaves undesirably brittle, because, plastic deformation is constrained, leading to poor resistance to crack initiation and propagation. Hence it is necessary to improve the toughness without sacrificing the other important mechanical and thermal properties. In this work, glass-fiber-reinforced composite with nano-alumina modified epoxy matrix was successfully produced with a hand lay-up process and characterized by EDAX and XRD technique for its composition. The experimental results show that the composites exhibited improvements in inter-laminar toughness values (GIC and GIIC) along with improvements in other mechanical properties, especially in toughness related properties. The Mode-I interlaminar fracture toughness for 2 phr (per hundred gram resin) nano-alumina was 2.5 times higher than that of unfilled epoxy and the Mode-II inter-laminar fracture toughness improved by 37%. The significant increase in Mode-I fracture toughness and improvement in Mode II inter-laminar fracture toughness resulting from the nano-particle modification, indicates a pronounced increase in matrix toughness. Impact tests suggest that the energy absorption capability of the GFRP considerably improved with the addition of equi-axed nano-alumina particles with epoxy resin. The laminate and fracture surface morphology analysis was done to understand the fracture and toughening mechanisms behind these property changes. The bending characteristic such as ILSS and Flexural properties recorded the maximum improvements of 14% and 17% respectively for the laminate with nano-alumina modified epoxy. A significant improvement in flexural modulus of over 37% was noticed with respect to unmodified epoxy. The experimental results show that the tensile modulus exhibited 15% improvement compared to laminate without nano-alumina, while, a modest change was observed in the tensile strength.