Subhankar Das
@upes.ac.in
Assistant professor, Department of Mechanical Engineering
University of Petroleum and Energy Studies
EDUCATION
PhD in Mechanical Engineering from NIT Silchar in the year 2019
Scopus Publications
Scopus Publications
Lakshi Nandan Borah, Subhankar Das, Pannalal Choudhury, and Sudipta Halder
Elsevier BV
Rahul Chamola, Subhankar Das, Dharamvir Singh Ahlawat, Yogendra Kumar Mishra, and M. S. Goyat
Springer Science and Business Media LLC
Nazrul Islam Khan, Sudipta Halder, M. S. Goyat, Lakshi Nandan Borah, and Subhankar Das
Royal Society of Chemistry (RSC)
The concept of using bio-inspired healing mechanisms in fiber-reinforced polymer (FRP)-based laminated composites is one of the trending areas of research for lightweight high-performance materials.
Konica Sharma, M. K. Malik, Amit Chawla, Subhankar Das, Dharamvir Singh Ahlawat, and M. S. Goyat
Springer Science and Business Media LLC
M. S. Goyat, Saksham Sharma, Subhankar Das, B. S. Tewari, Mukesh Kumar, Tejendra K. Gupta, and Charu Pant
Springer Science and Business Media LLC
Pannalal Choudhury, Sudipta Halder, and Subhankar Das
SAGE Publications
Optimized process parameters of a top–down approach via the ultrasonic dual-mode mixing process are adopted to disperse and exfoliate graphene nanoplatelets uniformly in the epoxy resin and fabricate hybrid GFRP laminates. The in-plane tensile and out-of-plane flexural behavior of the hybrid GFRPs made with different concentration of GNPs have been investigated. The test results show that ∼39.47% and ∼40.87% enhancement in tensile strength and flexural strength has been attained for the hybrid GFRPs made with 1 wt% of GNPs. In addition, the enhancement of ∼117% in absorbed failure energy and ∼28.56% in work of fracture is also achieved. Mori Tanaka Method has been used to calculate the modulus of the GNP-epoxy composite system, and these results are used further to predict the modulus of the hybrid GFRPs. The theoretical moduli so obtained are used to compare the experimental modulus of the hybrid GFRPs as a function of GNP concentration. Fractography examination of the fractured hybrid GFRPs reveals it reduced interlaminar delamination, which is governed by the effective load transferability of GNP-infused epoxy network.
Subhankar Das, Sudipta Halder, Bappi Paul, Nazrul Islam Khan, and M.S. Goyat
Elsevier BV
Dhritiman TALUKDAR, Sudipta HALDER, Subhankar DAS, M.S. GOYAT, and Abhishek Kumar MISHRA
Metallurgy and Materials Science Research Institute, Chulalongkorn University
Molecular dynamics simulations were performed to investigate the effect of fullerenes (C60) on the thermal and mechanical properties of a cross-linked epoxy system composed of epoxy resin DGEBA and curing agent DETA. Hence, a comparative investigation was performed on the thermal and mechanical properties of DGEBA/DETA reinforced with 2.3 wt% C60 and neat epoxy systems. Properties such as glass transition temperature (GTT), coefficients of thermal expansion (CTE), and elastic properties at different cross-linking densities. Simulation results indicated that the GTT of the epoxy increased by about 25 K due to the presence of C60. The effect of C60 on the CTE was very less, and at higher crosslinking densities, an increase in CTE before the glass transition was observed. It was also observed that the effect of C60 on mechanical properties is dependent on the crosslinking density. The young’s modulus of the epoxy/C60 system at a high strain rate showed a drastic decrease as compared to the neat epoxy system at higher crosslinking densities. The highest value of young’s modulus of the epoxy/C60 system was observed at 65% crosslinking density.
Subhankar Das, Debabrata Gayen, Saurabh Kumar, and Abhishek Joshi
Elsevier BV
Saurabh Kumar, Subhankar Das, Debabrata Gayen, and Ankita Joshi
Elsevier BV
Nazrul Islam Khan, Sudipta Halder, Subhankar Das, and Manjeet S. Goyat
Wiley
Nazrul Islam Khan, Sudipta Halder, Nabajyoti Talukdar, Subhankar Das, and M.S. Goyat
Elsevier BV
Abstract A simplistic and economical process was employed for the oxidation of graphite nanoplatelets (GNPs) using concentrated HNO3, followed by their surface modification by amine functionalization via silanization with 3-aminopropyltriethoxysilane (APTES). The impact of the oxidation time of the GNPs (varied from 12 h to 72 h) and their surface functionalization was studied with respect to the change in thermo-mechanical and mechanical properties of the GNPs/epoxy nanocomposites. The degree of oxidation and functionalization of the GNPs was characterized using field emission scanning electron microscope (FESEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and thermo-gravimetric analysis (TGA). The optimized oxidation time (60 h) and surface functionalization of the GNPs resulted in the significant improvement in the storage modulus (~176%), glass transition temperature (Tg) (~15 °C), tensile strength (~98.71%) and tensile modulus (~142.66%) of the GNPs/epoxy nanocomposites as compared the to neat epoxy (NE) system. Such tremendous enhancement in the material properties by a facile and economical approach can exhibit an inordinate potential to replace the costly multistep oxidation methods of fabrication of graphene/epoxy nanocomposites at industrial scale.
Ankush Nandi, Subhankar Das, Sudipta Halder, Anirban Chakraborty, and Muhammad A Imam
SAGE Publications
The performance of fiber-reinforced composites significantly relies on the microstructure and properties of the fiber–matrix interface. Escalating the aspect ratio of the fiber surface by coating with nanoparticles is a proven technique for improving the fiber/matrix adhesion. Subsequently, improved adhesion between epoxy and fiber, which is ascribed due to improved interfacial friction, chemical bonding, and resin toughening would enhance the interfacial strength of such laminated composites. Here, graphite nanoparticles were oxidized, and these charged particles were coated onto the carbon fibers (CFs) surface using ultrasonically assisted direct current electrophoretic deposition. Functionalization of the graphite nanoparticle upon oxidation was confirmed through dispersion analysis, Fourier transformed infrared spectroscope, thermogravimetric analysis, and field emission scanning electron microscope. The CFs fabrics were grafted with different sets of samples prepared by varying voltage and deposition time. The deposition of oxidized graphite nanoparticle over the CFs was authenticated through field emission scanning electron microscope. A transverse fiber bundle test was carried out to assess interfacial strength between CF and epoxy matrix. The transverse fiber bundle test strength is found 113% higher for CF coated with oxidized graphite nanoparticles at 50 V for 5 min compared to that of as-received sized CF composites. Field emission scanning electron microscopy analysis of transverse fiber bundle test fractures samples identified multiple crack propagation zone owing to the presence of graphite nanoparticle on CF.
Subhankar Das, Sudipta Halder, Nazrul Islam Khan, Bappi Paul, and M.S. Goyat
Elsevier BV
Abstract In GFRP laminated composites, matrix-fiber delamination is almost unavoidable and a serious problem that significantly hampers the mechanical properties of the composites. This work presents the use of cost-effective silanized milled graphite nanoparticles (GrNPs) to mitigate matrix-fiber delamination in GFRP laminated composites. FESEM and TEM analysis of pristine GrNPs exhibit porous structure consisting of stacked and randomly oriented planes with a large number of defect sites. The silanization of GrNPs (SGrNPs) results in the covering of pores or defect sites and produces the rough surfaces. The SGrNPs (0.5 wt%) reinforced GRFP laminated composites reveal the enhancement in the mechanical properties such as tensile strength (~33%), tensile modulus (~21%), toughness (~35%), flexural strength (~42.6%), work of fracture (~57%), and short beam strength (~23%), respectively. The improvement in the mechanical properties of the composites is due to the mitigation of matrix-fiber delamination by SGrNPs.
Nazrul Islam Khan, Sudipta Halder, Subhankar Das, and Jialai Wang
Elsevier BV
Abstract Effective functionalization of graphitic nano-fillers for better exfoliation and interfacial interaction with epoxy matrix is highly desirable for fabrication of high-performance laminated composites. This paper demonstrates the level of exfoliation of low cost aggregated graphitic nanoplatelets (GNPs) through a facile oxidation method and their amine functionalization to use as reinforcement in hybrid carbon fiber reinforced polymer (CFRP) composite with improved interfacial properties. The morphologies, surface functional groups, surface topography, surface elements, structural information of amine functionalized GNPs were characterized by FESEM, FT-IR, AFM, XPS, Raman analysis respectively. The hybrid CFRPs reinforced with 60 h of oxidized followed by silanized GNPs (OSG-60) demonstrated significant improvement in tensile strength (∼97%), flexural strength (∼62.3%) and interlaminar shear strength (∼27.42%) with respect to the control. Topographic investigation of OSG-60 demonstrates exfoliation of graphene sheets up to ∼2 to 3 layers along with uniformly decorated amine based silane moieties after silanization. Assessing the interfacial nanomechanical properties of hybrid CFRP having OSG-60 through nanoindentation, we found ∼33.41% enhancement in interfacial stiffness at the juncture of the fibers within the inter-ply region. Thus, this work provides a clear insight of an industrial ready method for delivering a durable and high-performance hybrid CFRP composites.
Subhankar Das, Sudipta Halder, and Nazrul Islam Khan
Elsevier BV
Abstract This study demonstrates the effect of pristine and oxidized fullerene dispersion on the mechanical properties of fullerene C60-epoxy nanocomposite. Fullerene was dispersed in the epoxy system by ultrasonic mixing. Results reveal that incorporation of pristine fullerene in epoxy system enhances the tensile strength and Young’s modulus by ∼13% and ∼16.5% respectively with respect to neat epoxy system, whereas oxidized fullerene enhances the same by ∼23% and ∼46%, respectively. However, the percentage elongation and toughness got reduced, whereas, the fracture toughness and strain energy release rate got enhanced by ∼101.35 % and ∼85.14 % due to the incorporation of oxidized fullerene.
Animesh Sinha, Nazrul Islam Khan, Subhankar Das, Jiawei Zhang, and Sudipta Halder
SAGE Publications
The effect of reactive (polyethylene glycol) and non-reactive (toluene) diluents on thermal and mechanical properties (tensile strength, hardness and fracture toughness) of diglycidyl ether of bisphenol A epoxy resin (cured by triethylenetetramine) was investigated. The thermal stability and mechanical properties of the epoxy resin modified with reactive and non-reactive diluents at different wt% were investigated using thermo-gravimetric analyser, tensile test, hardness test and single-edge-notched bend test. A minor variation in thermal stability was observed for epoxy resin after addition of polyethylene glycol and toluene at 0.5 wt%; however, further addition of reactive and non-reactive diluents diminished the thermal stability. The addition of 10 wt% of polyethylene glycol in epoxy resin significantly enhances the tensile strength (∼12%), hardness (∼14%) and fracture toughness (∼24%) when compared to that of neat epoxy resin. In contrast, major drop in mechanical performance was observed after addition of toluene in epoxy. Furthermore, fracture surfaces were investigated under field emission scanning electron microscope to elucidate the failure mechanism.
Subhankar Das, Sudipta Halder, Arijit Sinha, Muhammad Ali Imam, and Nazrul Islam Khan
American Chemical Society (ACS)
Fullerene (C60) is used to prepare a high-performance epoxy nanocomposite having enhanced antiscratch performance. Herein, C60 was oxidized and then silanized using 3-aminopropyltriethoxysilane. Oxidation disaggregates the C60 to form three-dimensional interconnected chainlike networks. These networks were concealed after silanization. The formation of active functional groups on silanized C60 regulated the polymer assembly and its coordination that enhances scratch recovery index (∼32%), wear resistance (∼57%), and microhardness (∼19%) of epoxy composites. Interestingly, dual advantage due to significant enhancement in mechanical and fracture properties uplifts the potential use of silanized C60 as nanoreinforcement in epoxy. The tensile strength, elastic modulus, and fracture toughness were enhanced by ∼28%, ∼30%, and ∼67.5%, respectively, for the epoxy nanocomposites. We provide fundamentals combined with the insight into the nature of toughening due to stiffness modulation by silanized C60 that delibe...
S Das, N Islam Khan, and S Halder
IOP Publishing
Epoxy composites were prepared using surface silanized chopped carbon fibers (CCFs). Silanized CCFs were synthesized from industrial waste carbon fibers. This work demonstrates the capability of surface silanized chopped carbon fibers to enhance the thermo- mechanical stability of the epoxy composites. The surface silanization of the CCFs to amend the interfacial interaction with epoxy network was done by attaching siloxane functional groups onto CCFs surfaces. Epoxy composites blended with 0.5 and 1 wt % of siloxane decorated CCFs showed a tremendous enhancement in storage modulus in comparison to neat epoxy. This enhancement of composites properties opens up the scope to utilize CCFs for high performance and cost effective epoxy composites. This study opens up the use of juvenile CCFs from waste carbon fibers for their utilization in next generation composites.
Nazrul Islam Khan, Sudipta Halder, Subhankar Das, and M.S. Goyat
Elsevier BV
Abstract In this study, the self-healing epoxy-filled microcapsules were synthesized using solvent evaporation technique. Poly(methylmethacrylate) (PMMA) was chosen as a shell material. The size of self-healing microcapsules was controlled by amending the sodium dodecyl sulphate (SDS) emulsifier concentration and agitation speed during the synthesis. The morphology, core content and molecular architecture of microcapsules were characterized by FESEM, solvent extraction technique and FTIR spectroscopy respectively. For microcapsules, the reduced size and shell wall thickness with enhanced core content showed a noticeable improvement escalating their potential use as self-healing agent in polymer composites.
Subhankar Das, Sudipta Halder, Jialai Wang, M.S. Goyat, A Anil Kumar, and Yi Fang
Elsevier BV
Abstract This study demonstrates the ability of functionalized chopped carbon fibers (CCFs) chosen from industrial waste to improve the thermo-mechanical properties of CCFs/epoxy composites. The defect sites onto the CCFs were created by their oxidation and the oxidized CCFs were covalently linked with siloxane functional groups to conceal their defects. The surface functionalization of CCFs was characterized by a simple chemical route, FTIR and TGA analysis, respectively. The surface morphology of functionalized CCFs showed the generation of highly dense networked globules. Epoxy composites filled with 0.5 wt% of siloxane attached CCFs (S-CCFs) showed a tremendous enhancement in storage modulus (∼376%) without sacrificing their thermal stability. Furthermore, the S-CCFs reinforced epoxy composites demonstrate a significant improvement in the tensile and fracture properties. Such enhancement in the mechanical properties can open up the scope for the utilization of CCFs as a potential cost-effective candidate for high-performance next generation structural composites.
Bappi Paul, Debraj Dhar Purkayastha, Siddhartha Sankar Dhar, Subhankar Das, and Sudipta Haldar
Elsevier BV
Abstract The present work reports about one-pot hydrothermal synthesis of a composite of Ag/Fe2O3 anchored on reduced graphene oxide (rGO) via homogeneous chemical precipitation of Fe(OH)3 and simultaneous reduction of Ag(I). The pristine aqueous suspension of graphene oxide (GO) synthesized by Hummers method is mixed with Fe(NO3)3·9H2O, AgNO3, urea and polyethylene glycol (PEG 4000). The mixture under hydrothermal conditions transforms into Ag/α-Fe2O3-rGO nanohybrid. Here PEG 4000plays dual role of surfactant as well as reducing agent for Ag(I). The synthesized Ag/Fe2O3-rGO nanocomposite was used as magnetically recoverable catalyst for room-temperature chemoselective reduction of aromatic nitro groups to the corresponding amines.
Pannalal Choudhury, Subhankar Das, Sudipta Halder, and Krishna Murari Pandey
Springer Science and Business Media LLC
Finite element analyses of laminated composites were done in the present study with respect to suppression of free edge delamination by an innovative technique. Wrap-around configuration was considered to determine its effectiveness over the wrapper-less laminated configuration on laminated composites. Nodal stresses were generated ahead of the crack tip through finite element analysis. This was used for determining interlaminar normal stress and inter laminar shear stress distributions at the critical interface. Later virtual crack closure technique was used to estimate the strain energy release rate components for several sizes of virtual crack extensions through a single finite element analysis. Computational analysis predicts Mode-I delamination as dominant mode of failure. This mode of delamination was significantly suppressed with wrap-around configuration on laminated composites.