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Nripati Ranjan Bose - One of the best experts on this subject based on the ideXlab platform.
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static and dynamic mechanical properties of vinylester Resin Matrix composites reinforced with shellac treated jute yarns
Industrial & Engineering Chemistry Research, 2006Co-Authors: Dipa Ray, A K Rana, Suparna Sengupta, Nripati Ranjan BoseAbstract:Natural fiber-reinforced composites are currently used for various types of applications. However, to improve the fiber/Resin bonding at the interface, some suitable chemical modification of the fibers is required. In the present study, an attempt has been made to use an inexpensive, easily available, and water-soluble (in alkaline medium) natural Resin shellac for the surface treatment of jute yarns. Jute yarns were treated with 1%, 2%, and 5% shellac solution, and these treated jute yarns were used as reinforcing material in vinylester Resin Matrix composites. The composites were subjected to flexural tests, and the flexural properties were found to be highest in the case of 1% treated composites. A dynamic mechanical study also showed the same trend, and the storage modulus was found to be highest for the 1% treated composites at room temperature. The fractured surfaces of the composites, as observed by SEM, were correlated with the mechanical properties.
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impact fatigue behaviour of vinylester Resin Matrix composites reinforced with alkali treated jute fibres
Composites Part A-applied Science and Manufacturing, 2002Co-Authors: Bijit Kumar Sarkar, Nripati Ranjan BoseAbstract:Abstract An impact fatigue study has been made for the first time on 35% jute/vinylester composites containing both untreated and alkali treated fibres. Longer alkali treatment removed the hemicellulose and improved the crystallinity and gave better fibre dispersion. The flexural strength properties of the composites made from treated fibre were superior. 4 h alkali treated jute fibres gave the optimum combination of improved interfacial bonding and fibre strength properties. However this was not reflected in their impact fatigue behaviour. On the contrary, the composites reinforced with 8 h alkali treated fibres displayed superior impact fatigue properties. Here, the fibres suffered catastrophic fracture with microfibrillar pull-out at some places and improved the fatigue resistance property of the composites as evident from SEM micrographs.
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impact fatigue behaviour of vinylester Resin Matrix composites reinforced with alkali treated jute fibres
Composites Part A-applied Science and Manufacturing, 2002Co-Authors: Bijit Kumar Sarkar, Nripati Ranjan BoseAbstract:Abstract An impact fatigue study has been made for the first time on 35% jute/vinylester composites containing both untreated and alkali treated fibres. Longer alkali treatment removed the hemicellulose and improved the crystallinity and gave better fibre dispersion. The flexural strength properties of the composites made from treated fibre were superior. 4 h alkali treated jute fibres gave the optimum combination of improved interfacial bonding and fibre strength properties. However this was not reflected in their impact fatigue behaviour. On the contrary, the composites reinforced with 8 h alkali treated fibres displayed superior impact fatigue properties. Here, the fibres suffered catastrophic fracture with microfibrillar pull-out at some places and improved the fatigue resistance property of the composites as evident from SEM micrographs.
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The mechanical properties of vinylester Resin Matrix composites reinforced with alkali-treated jute fibres
Composites Part A-applied Science and Manufacturing, 2000Co-Authors: Bijit Kumar Sarkar, A K Rana, Nripati Ranjan BoseAbstract:Jute fibres were subjected to alkali treatment with 5% NaOH solution for 0, 2, 4, 6 and 8 h at 30°C. The modulus of the jute fibres improved by 12, 68 and 79% after 4, 6 and 8 h of treatment, respectively. The tenacity of the fibres improved by 46% after 6 and 8 h treatment and the % breaking strain was reduced by 23% after 8 h treatment. For 35% composites with 4 h-treated fibres, the flexural strength improved from 199.1 to 238.9 MPa by 20%, modulus improved from 11.89 to 14.69 GPa by 23% and laminar shear strength increased from 0.238 to 0.283 MPa by 19%. On plotting different values of slopes obtained from the rates of improvement of flexural strength and modulus, against NaOH treatment time, two different failure modes were apparent before and after 4 h of NaOH treatment. In the first region between 0 and 4 h, fibre pull out was predominant whereas in the second region between 6 and 8 h, transverse fracture occurred with minimum fibre pull out. This observation was well supported by the SEM investigations of the fracture surfaces.
Bijit Kumar Sarkar - One of the best experts on this subject based on the ideXlab platform.
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thermal behavior of vinyl ester Resin Matrix composites reinforced with alkali treated jute fibers
Journal of Applied Polymer Science, 2004Co-Authors: Bijit Kumar Sarkar, R K Basak, A K RanaAbstract:The thermal behavior of vinyl ester Resin Matrix composites reinforced with jute fibers treated for 2, 4, 6, and 8 h with 5% NaOH was studied with Thermo-gravimetric analysis and differential scanning calorimetry. The moisture desorption peak shifted to a higher temperature, from 37 to 58.3°C, for all the treated-fiber composites because of improved wetting of the fibers by the Resin and stronger bonding at the interface. The degradation temperature of the vinyl ester Resin in the composites was lowered to 410.3°C from that of the neat Resin, 418.8°C. The X-ray diffraction studies showed increased crystallinity of the treated fibers, which affected the enthalpy of the α-cellulose and hemicellulose degradation. The hemicellulose degradation temperature remained the same (299.7°C) in all the treated-fiber composites, but the enthalpy associated with the hemicellulose degradation showed an increasing trend in the treated composites with a small increase in the weight loss. This could be attributed to the increased hydrogen bonding between the more accessible OH groups of the hemicellulose in the noncrystalline region of the jute fiber and the Resin. The degradation temperature of α-cellulose was lowered from 364.2 to 356.8°C in the treated composites. The enthalpy of α-cellulose degradation showed a decreasing trend with a lowering of the weight loss. The crystalline regions of the fiber, consisting of closely packed α-cellulose chains, were bonded with the Resin mainly on the surface through hydrogen bonds and became more resistant to thermal degradation; this reduced the weight loss. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 123–129, 2004
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dynamic mechanical and thermal analysis of vinylester Resin Matrix composites reinforced with untreated and alkali treated jute fibres
Composites Science and Technology, 2002Co-Authors: Dipa Ray, Bijit Kumar Sarkar, Siddhartha Das, A K RanaAbstract:Abstract Vinylester-Resin-Matrix composites reinforced with untreated and 5% NaOH treated jute fibres for 4 and 8 h with different fibre loading were subjected to dynamic mechanical and thermal analysis to determine their dynamic properties as a function of temperature. For all the composites the storage modulus, E′, decreased with increase in temperature, with a significant fall in the temperature range 110°–170 °C. For the treated composites, the rate of fall, dE′/dT, had an inverse relationship with the defect concentrations in the composites. The lowest defect concentrations in the 4 h treated composites corresponded to the highest rate of fall. The glass transition temperature, Tg, of the unreinforced Resin, corresponding to the loss modulus peak, was 101.2 °C, whereas that of the composites increased by nearly 28 °C on account of the restricted mobility of the Resin molecules in the presence of the fibres. In the case of the treated composites, the Tg value showed a decreasing trend (128 to 125 °C). Unlike the plain Resin, a tiny hump was observed in the loss modulus, E″, curves of all the composites around 166 °C, which became broader and more prominent with increase in the jute fibre content. The very high tanδ value of the Resin decreased in the composites, indicating that the addition of the fibres lowered the damping capacity of the composites.
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impact fatigue behaviour of vinylester Resin Matrix composites reinforced with alkali treated jute fibres
Composites Part A-applied Science and Manufacturing, 2002Co-Authors: Bijit Kumar Sarkar, Nripati Ranjan BoseAbstract:Abstract An impact fatigue study has been made for the first time on 35% jute/vinylester composites containing both untreated and alkali treated fibres. Longer alkali treatment removed the hemicellulose and improved the crystallinity and gave better fibre dispersion. The flexural strength properties of the composites made from treated fibre were superior. 4 h alkali treated jute fibres gave the optimum combination of improved interfacial bonding and fibre strength properties. However this was not reflected in their impact fatigue behaviour. On the contrary, the composites reinforced with 8 h alkali treated fibres displayed superior impact fatigue properties. Here, the fibres suffered catastrophic fracture with microfibrillar pull-out at some places and improved the fatigue resistance property of the composites as evident from SEM micrographs.
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impact fatigue behaviour of vinylester Resin Matrix composites reinforced with alkali treated jute fibres
Composites Part A-applied Science and Manufacturing, 2002Co-Authors: Bijit Kumar Sarkar, Nripati Ranjan BoseAbstract:Abstract An impact fatigue study has been made for the first time on 35% jute/vinylester composites containing both untreated and alkali treated fibres. Longer alkali treatment removed the hemicellulose and improved the crystallinity and gave better fibre dispersion. The flexural strength properties of the composites made from treated fibre were superior. 4 h alkali treated jute fibres gave the optimum combination of improved interfacial bonding and fibre strength properties. However this was not reflected in their impact fatigue behaviour. On the contrary, the composites reinforced with 8 h alkali treated fibres displayed superior impact fatigue properties. Here, the fibres suffered catastrophic fracture with microfibrillar pull-out at some places and improved the fatigue resistance property of the composites as evident from SEM micrographs.
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The mechanical properties of vinylester Resin Matrix composites reinforced with alkali-treated jute fibres
Composites Part A-applied Science and Manufacturing, 2000Co-Authors: Bijit Kumar Sarkar, A K Rana, Nripati Ranjan BoseAbstract:Jute fibres were subjected to alkali treatment with 5% NaOH solution for 0, 2, 4, 6 and 8 h at 30°C. The modulus of the jute fibres improved by 12, 68 and 79% after 4, 6 and 8 h of treatment, respectively. The tenacity of the fibres improved by 46% after 6 and 8 h treatment and the % breaking strain was reduced by 23% after 8 h treatment. For 35% composites with 4 h-treated fibres, the flexural strength improved from 199.1 to 238.9 MPa by 20%, modulus improved from 11.89 to 14.69 GPa by 23% and laminar shear strength increased from 0.238 to 0.283 MPa by 19%. On plotting different values of slopes obtained from the rates of improvement of flexural strength and modulus, against NaOH treatment time, two different failure modes were apparent before and after 4 h of NaOH treatment. In the first region between 0 and 4 h, fibre pull out was predominant whereas in the second region between 6 and 8 h, transverse fracture occurred with minimum fibre pull out. This observation was well supported by the SEM investigations of the fracture surfaces.
Dipa Ray - One of the best experts on this subject based on the ideXlab platform.
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thermal and electrical behavior of vinylester Resin Matrix composites filled with fly ash particles
Polymer Composites, 2008Co-Authors: Dipa Ray, Sourish Banerjee, Amar K. Mohanty, Manjusri MisraAbstract:Vinylester Resin Matrix composites were fabricated with 30, 40, 50, and 60% fly ash loading by room temperature casting method. The composites were subjected to thermogravimetric analysis. The 30 and the 60% composites showed a faster degradation at a lower temperature, whereas, the 40 and the 50% composites showed a higher onset temperature. The activation energy was calculated following Broido's equation and was found to be lowered in all the composites compared to the unfilled Resin. The residue increased in all the composites proportionately with the increase in the fly ash content. The temperature variation resistance of the unfilled Resin, 30 and 60% filled composites were measured and all the samples showed semi conducting nature in 40–60°C temperature range. POLYM. COMPOS., 29:58–62, 2008. © 2007 Society of Plastics Engineers
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static and dynamic mechanical properties of vinylester Resin Matrix composites filled with fly ash
Macromolecular Materials and Engineering, 2006Co-Authors: Dipa Ray, Debadrita Bhattacharya, Amar K. Mohanty, Lawrence T Drzal, Manjusri MisraAbstract:Vinylester Resin Matrix composites were prepared with a fly ash loading of 30, 40, 50 and 60 wt.-%. Flexural properties of the composites were investigated. It was found that the flexural strength was lowered in all the filled composites, but the flexural modulus showed a significant increase of 10, 57, 112% in case of 30,40 and 50 wt.-% fly-ash-loaded composites respectively, compared to the neat Resin. However, there was a decrease in the mechanical properties in case of 60 wt.-% fly-ash-filled composites. The dynamic mechanical analysis was carried out to obtain information about the Matrix-filler interaction at the interface. The storage modulus value at room temperature was highest for the 50 wt.-% fly-ash-filled composites, corroborating with the observed flexural modulus value. The fractured surfaces were examined under SEM and were correlated with the mechanical properties.
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static and dynamic mechanical properties of vinylester Resin Matrix composites filled with fly ash
Macromolecular Materials and Engineering, 2006Co-Authors: Dipa Ray, Debadrita Bhattacharya, Amar K. Mohanty, Lawrence T Drzal, Manjusri MisraAbstract:Vinylester Resin Matrix composites were prepared with a fly ash loading of 30, 40, 50 and 60 wt.-%. Flexural properties of the composites were investigated. It was found that the flexural strength was lowered in all the filled composites, but the flexural modulus showed a significant increase of 10, 57, 112% in case of 30,40 and 50 wt.-% fly-ash-loaded composites respectively, compared to the neat Resin. However, there was a decrease in the mechanical properties in case of 60 wt.-% fly-ash-filled composites. The dynamic mechanical analysis was carried out to obtain information about the Matrix-filler interaction at the interface. The storage modulus value at room temperature was highest for the 50 wt.-% fly-ash-filled composites, corroborating with the observed flexural modulus value. The fractured surfaces were examined under SEM and were correlated with the mechanical properties.
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static and dynamic mechanical properties of vinylester Resin Matrix composites reinforced with shellac treated jute yarns
Industrial & Engineering Chemistry Research, 2006Co-Authors: Dipa Ray, A K Rana, Suparna Sengupta, Nripati Ranjan BoseAbstract:Natural fiber-reinforced composites are currently used for various types of applications. However, to improve the fiber/Resin bonding at the interface, some suitable chemical modification of the fibers is required. In the present study, an attempt has been made to use an inexpensive, easily available, and water-soluble (in alkaline medium) natural Resin shellac for the surface treatment of jute yarns. Jute yarns were treated with 1%, 2%, and 5% shellac solution, and these treated jute yarns were used as reinforcing material in vinylester Resin Matrix composites. The composites were subjected to flexural tests, and the flexural properties were found to be highest in the case of 1% treated composites. A dynamic mechanical study also showed the same trend, and the storage modulus was found to be highest for the 1% treated composites at room temperature. The fractured surfaces of the composites, as observed by SEM, were correlated with the mechanical properties.
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dynamic mechanical and thermal analysis of vinylester Resin Matrix composites reinforced with untreated and alkali treated jute fibres
Composites Science and Technology, 2002Co-Authors: Dipa Ray, Bijit Kumar Sarkar, Siddhartha Das, A K RanaAbstract:Abstract Vinylester-Resin-Matrix composites reinforced with untreated and 5% NaOH treated jute fibres for 4 and 8 h with different fibre loading were subjected to dynamic mechanical and thermal analysis to determine their dynamic properties as a function of temperature. For all the composites the storage modulus, E′, decreased with increase in temperature, with a significant fall in the temperature range 110°–170 °C. For the treated composites, the rate of fall, dE′/dT, had an inverse relationship with the defect concentrations in the composites. The lowest defect concentrations in the 4 h treated composites corresponded to the highest rate of fall. The glass transition temperature, Tg, of the unreinforced Resin, corresponding to the loss modulus peak, was 101.2 °C, whereas that of the composites increased by nearly 28 °C on account of the restricted mobility of the Resin molecules in the presence of the fibres. In the case of the treated composites, the Tg value showed a decreasing trend (128 to 125 °C). Unlike the plain Resin, a tiny hump was observed in the loss modulus, E″, curves of all the composites around 166 °C, which became broader and more prominent with increase in the jute fibre content. The very high tanδ value of the Resin decreased in the composites, indicating that the addition of the fibres lowered the damping capacity of the composites.
Manjusri Misra - One of the best experts on this subject based on the ideXlab platform.
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thermal and electrical behavior of vinylester Resin Matrix composites filled with fly ash particles
Polymer Composites, 2008Co-Authors: Dipa Ray, Sourish Banerjee, Amar K. Mohanty, Manjusri MisraAbstract:Vinylester Resin Matrix composites were fabricated with 30, 40, 50, and 60% fly ash loading by room temperature casting method. The composites were subjected to thermogravimetric analysis. The 30 and the 60% composites showed a faster degradation at a lower temperature, whereas, the 40 and the 50% composites showed a higher onset temperature. The activation energy was calculated following Broido's equation and was found to be lowered in all the composites compared to the unfilled Resin. The residue increased in all the composites proportionately with the increase in the fly ash content. The temperature variation resistance of the unfilled Resin, 30 and 60% filled composites were measured and all the samples showed semi conducting nature in 40–60°C temperature range. POLYM. COMPOS., 29:58–62, 2008. © 2007 Society of Plastics Engineers
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static and dynamic mechanical properties of vinylester Resin Matrix composites filled with fly ash
Macromolecular Materials and Engineering, 2006Co-Authors: Dipa Ray, Debadrita Bhattacharya, Amar K. Mohanty, Lawrence T Drzal, Manjusri MisraAbstract:Vinylester Resin Matrix composites were prepared with a fly ash loading of 30, 40, 50 and 60 wt.-%. Flexural properties of the composites were investigated. It was found that the flexural strength was lowered in all the filled composites, but the flexural modulus showed a significant increase of 10, 57, 112% in case of 30,40 and 50 wt.-% fly-ash-loaded composites respectively, compared to the neat Resin. However, there was a decrease in the mechanical properties in case of 60 wt.-% fly-ash-filled composites. The dynamic mechanical analysis was carried out to obtain information about the Matrix-filler interaction at the interface. The storage modulus value at room temperature was highest for the 50 wt.-% fly-ash-filled composites, corroborating with the observed flexural modulus value. The fractured surfaces were examined under SEM and were correlated with the mechanical properties.
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static and dynamic mechanical properties of vinylester Resin Matrix composites filled with fly ash
Macromolecular Materials and Engineering, 2006Co-Authors: Dipa Ray, Debadrita Bhattacharya, Amar K. Mohanty, Lawrence T Drzal, Manjusri MisraAbstract:Vinylester Resin Matrix composites were prepared with a fly ash loading of 30, 40, 50 and 60 wt.-%. Flexural properties of the composites were investigated. It was found that the flexural strength was lowered in all the filled composites, but the flexural modulus showed a significant increase of 10, 57, 112% in case of 30,40 and 50 wt.-% fly-ash-loaded composites respectively, compared to the neat Resin. However, there was a decrease in the mechanical properties in case of 60 wt.-% fly-ash-filled composites. The dynamic mechanical analysis was carried out to obtain information about the Matrix-filler interaction at the interface. The storage modulus value at room temperature was highest for the 50 wt.-% fly-ash-filled composites, corroborating with the observed flexural modulus value. The fractured surfaces were examined under SEM and were correlated with the mechanical properties.
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the influence of fibre treatment on the performance of coir polyester composites
Composites Science and Technology, 2001Co-Authors: J Rout, Manjusri Misra, S. S. Tripathy, Sanjay K. Nayak, Amar K. MohantyAbstract:Abstract Surface modifications of coir fibres involving alkali treatment, bleaching, and vinyl grafting are made in view of their use as reinforcing agents in general-purpose polyester Resin Matrix. The mechanical properties of composites like tensile, flexural and impact strength increase as a result of surface modification. Among all modifications, bleached (65°C) coir-polyester composites show better flexural strength (61.6 MPa) whereas 2% alkali-treated coir/polyester composites show significant improvement in tensile strength (26.80 MPa). Hybrid composites comprising glass fibre mat (7 wt.%), coir fibre mat (13 wt.%) and polyester Resin Matrix are prepared. Hybrid composites containing surface modified coir fibres show significant improvement in flexural strength. Water absorption studies of coir/polyester and hybrid composites show significant reduction in water absorption due to surface modifications of coir fibres. Scanning electron microscopy (SEM) investigations show that surface modifications improve the fibre/Matrix adhesion.
A K Rana - One of the best experts on this subject based on the ideXlab platform.
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static and dynamic mechanical properties of vinylester Resin Matrix composites reinforced with shellac treated jute yarns
Industrial & Engineering Chemistry Research, 2006Co-Authors: Dipa Ray, A K Rana, Suparna Sengupta, Nripati Ranjan BoseAbstract:Natural fiber-reinforced composites are currently used for various types of applications. However, to improve the fiber/Resin bonding at the interface, some suitable chemical modification of the fibers is required. In the present study, an attempt has been made to use an inexpensive, easily available, and water-soluble (in alkaline medium) natural Resin shellac for the surface treatment of jute yarns. Jute yarns were treated with 1%, 2%, and 5% shellac solution, and these treated jute yarns were used as reinforcing material in vinylester Resin Matrix composites. The composites were subjected to flexural tests, and the flexural properties were found to be highest in the case of 1% treated composites. A dynamic mechanical study also showed the same trend, and the storage modulus was found to be highest for the 1% treated composites at room temperature. The fractured surfaces of the composites, as observed by SEM, were correlated with the mechanical properties.
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thermal behavior of vinyl ester Resin Matrix composites reinforced with alkali treated jute fibers
Journal of Applied Polymer Science, 2004Co-Authors: Bijit Kumar Sarkar, R K Basak, A K RanaAbstract:The thermal behavior of vinyl ester Resin Matrix composites reinforced with jute fibers treated for 2, 4, 6, and 8 h with 5% NaOH was studied with Thermo-gravimetric analysis and differential scanning calorimetry. The moisture desorption peak shifted to a higher temperature, from 37 to 58.3°C, for all the treated-fiber composites because of improved wetting of the fibers by the Resin and stronger bonding at the interface. The degradation temperature of the vinyl ester Resin in the composites was lowered to 410.3°C from that of the neat Resin, 418.8°C. The X-ray diffraction studies showed increased crystallinity of the treated fibers, which affected the enthalpy of the α-cellulose and hemicellulose degradation. The hemicellulose degradation temperature remained the same (299.7°C) in all the treated-fiber composites, but the enthalpy associated with the hemicellulose degradation showed an increasing trend in the treated composites with a small increase in the weight loss. This could be attributed to the increased hydrogen bonding between the more accessible OH groups of the hemicellulose in the noncrystalline region of the jute fiber and the Resin. The degradation temperature of α-cellulose was lowered from 364.2 to 356.8°C in the treated composites. The enthalpy of α-cellulose degradation showed a decreasing trend with a lowering of the weight loss. The crystalline regions of the fiber, consisting of closely packed α-cellulose chains, were bonded with the Resin mainly on the surface through hydrogen bonds and became more resistant to thermal degradation; this reduced the weight loss. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 123–129, 2004
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dynamic mechanical and thermal analysis of vinylester Resin Matrix composites reinforced with untreated and alkali treated jute fibres
Composites Science and Technology, 2002Co-Authors: Dipa Ray, Bijit Kumar Sarkar, Siddhartha Das, A K RanaAbstract:Abstract Vinylester-Resin-Matrix composites reinforced with untreated and 5% NaOH treated jute fibres for 4 and 8 h with different fibre loading were subjected to dynamic mechanical and thermal analysis to determine their dynamic properties as a function of temperature. For all the composites the storage modulus, E′, decreased with increase in temperature, with a significant fall in the temperature range 110°–170 °C. For the treated composites, the rate of fall, dE′/dT, had an inverse relationship with the defect concentrations in the composites. The lowest defect concentrations in the 4 h treated composites corresponded to the highest rate of fall. The glass transition temperature, Tg, of the unreinforced Resin, corresponding to the loss modulus peak, was 101.2 °C, whereas that of the composites increased by nearly 28 °C on account of the restricted mobility of the Resin molecules in the presence of the fibres. In the case of the treated composites, the Tg value showed a decreasing trend (128 to 125 °C). Unlike the plain Resin, a tiny hump was observed in the loss modulus, E″, curves of all the composites around 166 °C, which became broader and more prominent with increase in the jute fibre content. The very high tanδ value of the Resin decreased in the composites, indicating that the addition of the fibres lowered the damping capacity of the composites.
-
The mechanical properties of vinylester Resin Matrix composites reinforced with alkali-treated jute fibres
Composites Part A-applied Science and Manufacturing, 2000Co-Authors: Bijit Kumar Sarkar, A K Rana, Nripati Ranjan BoseAbstract:Jute fibres were subjected to alkali treatment with 5% NaOH solution for 0, 2, 4, 6 and 8 h at 30°C. The modulus of the jute fibres improved by 12, 68 and 79% after 4, 6 and 8 h of treatment, respectively. The tenacity of the fibres improved by 46% after 6 and 8 h treatment and the % breaking strain was reduced by 23% after 8 h treatment. For 35% composites with 4 h-treated fibres, the flexural strength improved from 199.1 to 238.9 MPa by 20%, modulus improved from 11.89 to 14.69 GPa by 23% and laminar shear strength increased from 0.238 to 0.283 MPa by 19%. On plotting different values of slopes obtained from the rates of improvement of flexural strength and modulus, against NaOH treatment time, two different failure modes were apparent before and after 4 h of NaOH treatment. In the first region between 0 and 4 h, fibre pull out was predominant whereas in the second region between 6 and 8 h, transverse fracture occurred with minimum fibre pull out. This observation was well supported by the SEM investigations of the fracture surfaces.