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R D K Misra - One of the best experts on this subject based on the ideXlab platform.
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scratch deformation behavior of thermoplastic materials with significant differences in ductility
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: R S Hadal, R D K MisraAbstract:Abstract A comparative study of the scratch deformation behavior of neat ethylene–propylene copolymers and Polypropylene with significant differences in ductility is made by combining morphological examination by electron microscopy and scratch deformation parameters by atomic force microscopy. Also, the deformation behavior during scratch tests is examined for their respective long and short chain polymers. The ability of polymeric materials to resist scratch deformation under identical scratch test conditions follows the sequence (from maximum resistance to minimum resistance): short chain Polypropylene > long chain Polypropylene > short chain ethylene–propylene > long chain ethylene–propylene. The scratch tracks in ethylene–propylene copolymers were characterized by a consecutive parabolic pattern containing voids, while Polypropylenes exhibited zig-zag periodic scratch tracks. The greater plastic flow in ethylene–propylene copolymers is encouraged by the high ductility of the copolymer and the ability to nucleate microvoids. The quasi-static periodic scratch tracks are a consequence of sequential accumulation and release of tangential force and represents the stick–slip process. The susceptibility to scratch deformation is discussed in terms of modulus, elastic recovery, scratch hardness, and entanglement density of polymeric materials. A higher effective entanglement density and percentage crystallinity of short chain polymers is helpful in enhancing scratch resistance as compared to their respective long chain polymers.
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the influence of loading rate and concurrent microstructural evolution in micrometric talc and wollastonite reinforced high isotactic Polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: R S Hadal, R D K MisraAbstract:The paper describes the response of neat high isotactic Polypropylene (iPP) and talc (iPP-T) and wollastonite (iPP-W)-reinforced Polypropylenes to tensile loading rate and the evolution of microstructure during plastic deformation. Unreinforced and reinforced Polypropylene materials exhibit significant sensitivity to tensile loading rate (strain rate) and the change in strain rate sensitivity index parameter with strain signifies a change in the micromechanism of plastic deformation and mode of fracture. Plastic deformation in neat high isotactic Polypropylene is characterized by craze-tearing and brittle mode of fracture, while both talc- and wollastonite-reinforced Polypropylenes are characterized by wedge, ridge-tearing, fibrillation, and brittle fracture. The brittle fracture is associated with debonding of mineral particles from the Polypropylene matrix. However, yield stress of all the three materials exhibit similar dependence to loading rate and similar activation volume that suggests similarity in the onset of plastic deformation process.
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effect of wollastonite and talc on the micromechanisms of tensile deformation in Polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: R S Hadal, Aravind Dasari, J Rohrmann, R D K MisraAbstract:Abstract The work presented here describes the effect of wollastonite and talc on the micromechanisms of surface deformation and subsequent propagation into the bulk of low and high crystallinity Polypropylenes during tensile straining. The potential of high resolution electron microscopy is utilized to examine deformation processes, and develop deformation mechanism maps. While mineral-reinforced Polypropylenes exhibited an increase in tensile modulus, yield strength remained unaffected. Crystallization behavior indicated that the reinforcement minerals increase the rate of nucleation with consequent increase in percentage of bulk crystallinity. The reinforcement of Polypropylene with wollastonite or talc alters the primary micromechanism of deformation from deformation bands/crazing in neat Polypropylenes to wedge/ridge tearing in mineral-reinforced low crystallinity Polypropylene composites. However, wedges were absent in high crystallinity Polypropylene composites. The final fracture in reinforced Polypropylene occurs by a mixed mode consisting of fibrillation and brittle mode, while crazing–tearing and brittle deformation are fracture modes for neat Polypropylenes.
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the role of micrometric wollastonite particles on stress whitening behavior of Polypropylene composites
Acta Materialia, 2004Co-Authors: Aravind Dasari, R D K MisraAbstract:The micromechanism and susceptibility to stress whitening during tensile straining of micrometric wollastonite mineral-reinforced Polypropylenes is studied by electron microscopy and compared with unreinforced neat Polypropylenes. Mineral-reinforced Polypropylene composite exhibit significantly reduced susceptibility to stress whitening, and are characterized by lower gray level in the plastically deformed stress whitened zone. This behavior is attributed to the effective reinforcement of Polypropylene by wollastonite that acts in concert increasing the tensile modulus of the composite and restricts plastic deformation of the matrix. The increase in tensile modulus is explained in terms of a three-phase model involving matrix, particle, and interface zone. Furthermore, isothermal crystallization indicated that the reinforcement mineral increases the rate of nucleation with consequent increase in % bulk crystallinity. The reinforcement of Polypropylene alters the primary micromechanism of stress whitening from deformation bands/crazing in neat Polypropylenes to wedge/ridge-tearing in mineral-reinforced Polypropylene composites. The final fracture in reinforced Polypropylene occurs by a mixed mode consisting of fibrillation and brittle mode, while crazing-tearing and brittle deformation are fracture modes for neat Polypropylene.
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on the scratch deformation of micrometric wollastonite reinforced Polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Aravind Dasari, J Rohrmann, R D K MisraAbstract:Scratch deformation characteristics of neat and wollastonite-containing Polypropylenes under identical test conditions are examined by electron microscopy and atomic force microscopy techniques. The study indicates that the severity of plastic deformation during scratch deformation in filled Polypropylenes is a strong function of the debonding/detachment of wollastonite mineral particles from the Polypropylene matrix. Scratch resistance is evaluated in terms of scratch hardness, scratch depth, average scratch roughness, thickness and density of the scratch tracks. Atomic force microscopy suggests the presence of a localized region surrounding the reinforcement particle that is characterized by enhanced crystal nucleation in which the local chain conformation and kinetics are likely to be different from regions that are a significant distance away from the mineral particle.
R S Hadal - One of the best experts on this subject based on the ideXlab platform.
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scratch deformation behavior of thermoplastic materials with significant differences in ductility
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: R S Hadal, R D K MisraAbstract:Abstract A comparative study of the scratch deformation behavior of neat ethylene–propylene copolymers and Polypropylene with significant differences in ductility is made by combining morphological examination by electron microscopy and scratch deformation parameters by atomic force microscopy. Also, the deformation behavior during scratch tests is examined for their respective long and short chain polymers. The ability of polymeric materials to resist scratch deformation under identical scratch test conditions follows the sequence (from maximum resistance to minimum resistance): short chain Polypropylene > long chain Polypropylene > short chain ethylene–propylene > long chain ethylene–propylene. The scratch tracks in ethylene–propylene copolymers were characterized by a consecutive parabolic pattern containing voids, while Polypropylenes exhibited zig-zag periodic scratch tracks. The greater plastic flow in ethylene–propylene copolymers is encouraged by the high ductility of the copolymer and the ability to nucleate microvoids. The quasi-static periodic scratch tracks are a consequence of sequential accumulation and release of tangential force and represents the stick–slip process. The susceptibility to scratch deformation is discussed in terms of modulus, elastic recovery, scratch hardness, and entanglement density of polymeric materials. A higher effective entanglement density and percentage crystallinity of short chain polymers is helpful in enhancing scratch resistance as compared to their respective long chain polymers.
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the influence of loading rate and concurrent microstructural evolution in micrometric talc and wollastonite reinforced high isotactic Polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: R S Hadal, R D K MisraAbstract:The paper describes the response of neat high isotactic Polypropylene (iPP) and talc (iPP-T) and wollastonite (iPP-W)-reinforced Polypropylenes to tensile loading rate and the evolution of microstructure during plastic deformation. Unreinforced and reinforced Polypropylene materials exhibit significant sensitivity to tensile loading rate (strain rate) and the change in strain rate sensitivity index parameter with strain signifies a change in the micromechanism of plastic deformation and mode of fracture. Plastic deformation in neat high isotactic Polypropylene is characterized by craze-tearing and brittle mode of fracture, while both talc- and wollastonite-reinforced Polypropylenes are characterized by wedge, ridge-tearing, fibrillation, and brittle fracture. The brittle fracture is associated with debonding of mineral particles from the Polypropylene matrix. However, yield stress of all the three materials exhibit similar dependence to loading rate and similar activation volume that suggests similarity in the onset of plastic deformation process.
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effect of wollastonite and talc on the micromechanisms of tensile deformation in Polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: R S Hadal, Aravind Dasari, J Rohrmann, R D K MisraAbstract:Abstract The work presented here describes the effect of wollastonite and talc on the micromechanisms of surface deformation and subsequent propagation into the bulk of low and high crystallinity Polypropylenes during tensile straining. The potential of high resolution electron microscopy is utilized to examine deformation processes, and develop deformation mechanism maps. While mineral-reinforced Polypropylenes exhibited an increase in tensile modulus, yield strength remained unaffected. Crystallization behavior indicated that the reinforcement minerals increase the rate of nucleation with consequent increase in percentage of bulk crystallinity. The reinforcement of Polypropylene with wollastonite or talc alters the primary micromechanism of deformation from deformation bands/crazing in neat Polypropylenes to wedge/ridge tearing in mineral-reinforced low crystallinity Polypropylene composites. However, wedges were absent in high crystallinity Polypropylene composites. The final fracture in reinforced Polypropylene occurs by a mixed mode consisting of fibrillation and brittle mode, while crazing–tearing and brittle deformation are fracture modes for neat Polypropylenes.
Aravind Dasari - One of the best experts on this subject based on the ideXlab platform.
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effect of wollastonite and talc on the micromechanisms of tensile deformation in Polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: R S Hadal, Aravind Dasari, J Rohrmann, R D K MisraAbstract:Abstract The work presented here describes the effect of wollastonite and talc on the micromechanisms of surface deformation and subsequent propagation into the bulk of low and high crystallinity Polypropylenes during tensile straining. The potential of high resolution electron microscopy is utilized to examine deformation processes, and develop deformation mechanism maps. While mineral-reinforced Polypropylenes exhibited an increase in tensile modulus, yield strength remained unaffected. Crystallization behavior indicated that the reinforcement minerals increase the rate of nucleation with consequent increase in percentage of bulk crystallinity. The reinforcement of Polypropylene with wollastonite or talc alters the primary micromechanism of deformation from deformation bands/crazing in neat Polypropylenes to wedge/ridge tearing in mineral-reinforced low crystallinity Polypropylene composites. However, wedges were absent in high crystallinity Polypropylene composites. The final fracture in reinforced Polypropylene occurs by a mixed mode consisting of fibrillation and brittle mode, while crazing–tearing and brittle deformation are fracture modes for neat Polypropylenes.
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the role of micrometric wollastonite particles on stress whitening behavior of Polypropylene composites
Acta Materialia, 2004Co-Authors: Aravind Dasari, R D K MisraAbstract:The micromechanism and susceptibility to stress whitening during tensile straining of micrometric wollastonite mineral-reinforced Polypropylenes is studied by electron microscopy and compared with unreinforced neat Polypropylenes. Mineral-reinforced Polypropylene composite exhibit significantly reduced susceptibility to stress whitening, and are characterized by lower gray level in the plastically deformed stress whitened zone. This behavior is attributed to the effective reinforcement of Polypropylene by wollastonite that acts in concert increasing the tensile modulus of the composite and restricts plastic deformation of the matrix. The increase in tensile modulus is explained in terms of a three-phase model involving matrix, particle, and interface zone. Furthermore, isothermal crystallization indicated that the reinforcement mineral increases the rate of nucleation with consequent increase in % bulk crystallinity. The reinforcement of Polypropylene alters the primary micromechanism of stress whitening from deformation bands/crazing in neat Polypropylenes to wedge/ridge-tearing in mineral-reinforced Polypropylene composites. The final fracture in reinforced Polypropylene occurs by a mixed mode consisting of fibrillation and brittle mode, while crazing-tearing and brittle deformation are fracture modes for neat Polypropylene.
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on the scratch deformation of micrometric wollastonite reinforced Polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Aravind Dasari, J Rohrmann, R D K MisraAbstract:Scratch deformation characteristics of neat and wollastonite-containing Polypropylenes under identical test conditions are examined by electron microscopy and atomic force microscopy techniques. The study indicates that the severity of plastic deformation during scratch deformation in filled Polypropylenes is a strong function of the debonding/detachment of wollastonite mineral particles from the Polypropylene matrix. Scratch resistance is evaluated in terms of scratch hardness, scratch depth, average scratch roughness, thickness and density of the scratch tracks. Atomic force microscopy suggests the presence of a localized region surrounding the reinforcement particle that is characterized by enhanced crystal nucleation in which the local chain conformation and kinetics are likely to be different from regions that are a significant distance away from the mineral particle.
J Purnima - One of the best experts on this subject based on the ideXlab platform.
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development of glass fiber wollastonite reinforced Polypropylene hybrid composite mechanical properties and morphology
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Joshi Himani, J PurnimaAbstract:Hybridization with small amounts of mineral fibers makes these glass fiber composites more suitable for technical applications. This study focused on the performance of injection molded short wollastonite fiber and chopped glass fiber reinforced hybrid Polypropylene composites. Results showed that hybridization of glass fiber and wollastonite was found to be comparable to that of Polypropylene glass fiber composites. Analysis of fiber length distribution in the composite and fracture surface was performed to study fiber breakage fracture mechanism. The simultaneous compounding of Polypropylene with two fillers was done to obtain a hybrid composite. The mechanical properties of hybrid, injection molded, chopped glass fiber/wollastonite/Polypropylene composites have been investigated taking into account the effect of hybridization by these two types of fillers. This system is expected to have considerable mechanical properties, good surface finish and low cost. It has been found that the tensile, flexural, and impact properties of the filled Polypropylene were higher than those of unfilled Polypropylene. The hybrid effects of the tensile strength and modulus were studied by the rule of hybrid mixtures (RoHM) using the values of single fiber composites.
J Rohrmann - One of the best experts on this subject based on the ideXlab platform.
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effect of wollastonite and talc on the micromechanisms of tensile deformation in Polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: R S Hadal, Aravind Dasari, J Rohrmann, R D K MisraAbstract:Abstract The work presented here describes the effect of wollastonite and talc on the micromechanisms of surface deformation and subsequent propagation into the bulk of low and high crystallinity Polypropylenes during tensile straining. The potential of high resolution electron microscopy is utilized to examine deformation processes, and develop deformation mechanism maps. While mineral-reinforced Polypropylenes exhibited an increase in tensile modulus, yield strength remained unaffected. Crystallization behavior indicated that the reinforcement minerals increase the rate of nucleation with consequent increase in percentage of bulk crystallinity. The reinforcement of Polypropylene with wollastonite or talc alters the primary micromechanism of deformation from deformation bands/crazing in neat Polypropylenes to wedge/ridge tearing in mineral-reinforced low crystallinity Polypropylene composites. However, wedges were absent in high crystallinity Polypropylene composites. The final fracture in reinforced Polypropylene occurs by a mixed mode consisting of fibrillation and brittle mode, while crazing–tearing and brittle deformation are fracture modes for neat Polypropylenes.
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on the scratch deformation of micrometric wollastonite reinforced Polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Aravind Dasari, J Rohrmann, R D K MisraAbstract:Scratch deformation characteristics of neat and wollastonite-containing Polypropylenes under identical test conditions are examined by electron microscopy and atomic force microscopy techniques. The study indicates that the severity of plastic deformation during scratch deformation in filled Polypropylenes is a strong function of the debonding/detachment of wollastonite mineral particles from the Polypropylene matrix. Scratch resistance is evaluated in terms of scratch hardness, scratch depth, average scratch roughness, thickness and density of the scratch tracks. Atomic force microscopy suggests the presence of a localized region surrounding the reinforcement particle that is characterized by enhanced crystal nucleation in which the local chain conformation and kinetics are likely to be different from regions that are a significant distance away from the mineral particle.
