Now showing 1 - 10 of 10
  • Placeholder Image
    Publication
    Enhancing the material properties of carbon fiber epoxy composite by incorporating electrospun polyacrylonitrile nanofibers
    (01-01-2022)
    Vijay Kumar, Vishnu
    ;
    Ramakrishna, Seeram
    ;
    ;
    Composite materials are a superior class of material used in almost every field of engineering like construction, military, aerospace, ocean structures, communication, and various other high-performance applications owing to their high specific strength and modulus, increased design flexibility, desirable thermal expansion characteristics good resistance to fatigue and corrosion, and economic efficiency. However, their ply-by-ply nature makes them susceptible to delamination, which originates from the propagation of microcracks in the weak resin-rich layers. Many attempts have been made to address the lack of mechanical properties of this weak interlaminar region. A particularly promising approach involves the incorporation of nanofibers between the reinforcement layers as the composite is laid up. This work involves studying the property improvements in carbon fiber epoxy composite by interleaving electrospun polyacrylonitrile (PAN) nanofibers. Experimental testing involving Tensile, Izod, Charpy and high velocity impact tests showed improved material properties for the PAN nano-interleaved composite. These improvements achieved by nanofiber interleaving shows a greater potential in addressing major concerns for critical application of composite materials in future.
  • Placeholder Image
    Publication
    Life-cycle cost (LCC) based design procedure to determine the optimal design parameters and target reliability under nonlinear deformation for marine installations
    (01-01-2021)
    Vishnu, M.
    ;
    This study proposes a procedure to determine the optimal design parameters and target reliability based on Life cycle cost (LCC) based analysis. An iterative design procedure is performed for different levels of reserve strength ratio (RSR), and LCC is calculated. A case study is carried out for installation of the bottom fixed jacket support structure for offshore wind turbines (OWT) system subjected to extreme loading condition. To determine the ultimate capacity of the structure, static pushover analysis is integrated with the proposed design methodology. An evolutionary based particle swarm algorithm is selected for the structural design optimization of offshore jackets. The RSR evaluated from pushover analysis assists to determine the probability of failure based on the first order reliability method (FORM). Based on a set of LCC values, which are the collective sum of capital expenditure (CAPEX), operational cost (OPEX), and risk cost (RISKEX), the optimal design is reached.
  • Placeholder Image
    Publication
    Enhancing the properties of Carbon fiber thermoplastic composite by nanofiber interleaving
    (01-01-2022)
    Kumar, Vishnu Vijay
    ;
    ; ;
    Ramakrishna, Seeram
    Thermoplastic composites have growing significance due to the rising demand for cost-effective and lightweight materials with high structural endurance and recyclability. The composition of composites is altered to enhance their overall properties. Electrospun Polyacrylonitrile nanofiber interleaving in Carbon fiber thermoplastic composite is investigated in this paper. Material properties are estimated using Tensile, Izod, Charpy, and Ballistic testing. Experimental results suggest that the nanofiber interleaving resulted in a composite with enhanced properties. The study can be further extended in investigating the effect of nanofibrous addition in various composites.
  • Placeholder Image
    Publication
    LASER SPECTROSCOPIC ANALYSIS AND CHARACTERIZATION STUDIES OF MARINE BIOFOULING
    (01-01-2023)
    Thomas, Della
    ;
    ;
    Marine biofouling refers to the undesirable growth and adhesion of marine organisms such as barnacles, macro-algae, microbial slimes etc. on immersed structures. Tropical ocean environment teems with microorganisms, of which some adhere, both to the static ship hull and while en-route to the destination increasing roughness1. A laboratory-scale LIBS technique was used to analyse biofouling samples and its constituent common water-borne algae and bacterial species2. Biofouling composition was determined by collecting samples from marine structures and vessels and analysing them in laboratories. Biofouling characterization tests were also done such as SEM analysis. The Quanta 200 FEG Scanning Electron Microscope (SEM) was used for obtaining the SEM images. The structure of quartz crystal in the biofouling samples was also determined.
  • Placeholder Image
    Publication
    Fatigue crack behaviour of composite- and mono-coated marine structural components
    (01-01-2022)
    Manjunath, G. L.
    ;
    In this study, experimental and numerical studies of fatigue crack growth (FCG) mechanisms in coated and uncoated structural components of EN8 steel (EN8) and aluminium alloy 6063 (AA6063) samples were compared. Electroplating (EP) (of nickel (Ni) and chromium (Cr)) and physical vapour deposition technique (PVD) (of aluminium nitride (Al-N) and nanocrystalline layers of titanium aluminium nitride (Ti-Al-N)) methods were used for mono and composite metallic coatings of EN8 and AA6063. The present study focuses on the implications of the coating-substrate interface during FCG initiation and propagation by considering the loading-bearing ability of the coating. Fatigue cracking mechanism depends on coating fracture toughness (FT) at the interface of mono-composite coating and its thickness. In comparison, composite-coated PVD samples proved better than mono-coated electroplated samples due to the delayed plastic deformation process on the surface of the substrate sample.
  • Placeholder Image
    Publication
    Nanosecond laser induced breakdown spectroscopy for biofouling analysis and classification of fouling constituents
    (01-06-2020)
    Thomas, Della
    ;
    ;
    Marine biofouling refers to the undesirable growth and adhesion of marine organisms such as barnacles, macroalgae and microbial slimes on immersed structures. Biofouling composition is determined by collecting samples from marine structures and vessels and analyzing them in laboratories. Alternatively, an approach of online sensing based on Laser Induced Breakdown Spectroscopy (LIBS), which consists of analysis of the spectral emission from laser-induced plasma, can be considered for the elemental composition of biofouling. The study of marine biofouling using LIBS has not been attempted previously. In the present work, a laboratory-scale LIBS technique is used to analyze biofouling samples and its constituent common water-borne algae and bacterial species. First, LIBS database is created under controlled conditions for the selected biofilm constituent algae (Nitzschia sigma and Chaetoslorenzianus) and bacterial (Pseudomonas aeruginosa, Bacillus subtilis, E.coli) species. LIBS spectra are also acquired for Biofilm samples grown on Fiber Reinforced Plastic (FRP) and Stainless steel (SS) 316 L substrates suspended at a depth of 1 m in the tropical Indian Ocean. The studies are carried out for fouling growth period of 5, 10, 15 and 20 days in the intertidal region at a distance of 480 m from the shore. The study shows that the LIBS technique combined with the Principal Component Analysis (PCA) can be used for acquiring the spectra of biofouling species, its rapid classification and studying the growth characteristics. The LIBS database would serve as a means for early identification of marine fouling bacteria and algae species.
  • Placeholder Image
    Publication
    Laser Spectroscopy for Marine Biofouling Analysis
    (05-10-2020)
    Thomas, Della
    ;
    ; ;
    Sriyuthamurthy, P.
    In the present study, femtosecond Laser Induced Breakdown Spectroscopy LIBS technique has been used to investigate the growth of biofouling on Fiber Reinforced Plastic (FRP) panels submerged in the Indian Ocean for various stages of growth. The coupons were suspended in the Indian Ocean at a depth of 1m at a distance of 480 m from the shoreline. The panels were recovered from the sea at regular intervals of 5, 10, 15 and 20 days. Growth of fouling panels were monitored and related with contact angle measurements. Elemental characterization conducted with Femtosecond LIBS indicated the presence of the elements Al, Ca, N, Ba, and Na. The study would help in creating a database for marine biofouling.
  • Placeholder Image
    Publication
    Flammability and Fire Retardancy of Composites
    (01-01-2022)
    Kumar, Vishnu Vijay
    ;
    ;
    Nikhil, N. S.
    ;
    Ramakrishna, Seeram
    ;
    George, Gibin
    ;
    Tran, Thang Q.
    The low thermal resistance of composite materials poses a major hindrance in using them for various applications. These limitations are subdued by flame and fire retardants, which when added into polymers and composites provides an enhanced thermal and flame resistance. In this review, the various methods of improving the fire retardancy of composite materials are discussed along with a description of widely used flame retardant additives. The recent progress in the field of flammability and flame retardancy of composite materials is the main focus of this article and considered only recently published works. Additionally, the mechanism of combustion with an emphasis on the flammability of polymer composites is deliberated. The basic idea of improving the fire retardancy of composite is either by enhancing the composite constituents-reinforcement and matrix or by providing a coating to the composite. The flame retardancy mechanism and the methods to improve them are the hot topics for research as the light weight polymer composites are replacing metallic structures. Treatment of reinforcement, matrix, along with the various commonly used flame retardant additives are studied in this article. The circularity, sustainability, and environmentally friendly aspects of composites need to be taken care while considering waste management in the near future.
  • Placeholder Image
    Publication
    Biomolecule Characterization Using Laser Induced Breakdown Spectroscopy
    (01-01-2021)
    Thomas, Della
    ;
    ;
    In the present study, LIBS spectra of biomolecules have been analyzed. The basic biomolecules considered for the analysis were Carbohydrates, Protein and Nucleic acids. It was possible to detect the characteristic emission lines of C, H, N, O, S etc. in the above biomolecules. The samples were prepared for laser ablation as biofilms on glass slides. Interference from substrate was observed in the LIBS spectra of samples. Raman spectra would also be acquired in future studies to obtain molecular information for the biomolecules.
  • Placeholder Image
    Publication
    High velocity impact behavior of Hybrid composite under hydrostatic preload
    (01-01-2022)
    Kumar, Vishnu Vijay
    ;
    ;
    Balaganesan, G.
    ;
    ;
    Selvan, Arul
    ;
    Ramakrishna, Seeram
    The Hybridization concept creates a niche within the composite segment to customize materials for specific applications with reduced cost without sacrificing strength and durability. The composite structures develop strain during continuous operation, and any sudden impact on these preloaded parts might result in catastrophic accidents. Studying impact response during such conditions is essential in designing and developing structures. This study experimentally investigates the high velocity impact response of Hybrid (Carbon-Glass) composite under normal and hydrostatic preload conditions. Mechanical tests involving Tensile, Izod, and Charpy are conducted. High velocity impact testing is carried out with a vertical single-stage gas gun with additional provision for hydrostatic preloading. An oscilloscope with a laser source measures the initial velocity, and Photogrammetry using a high-speed camera measure the residual velocity of a projectile. The mechanical test results suggest that Hybridization resulted in a significant property enhancement. The high velocity impact resistance and energy absorption are higher for Hybrid under both normal and preloaded impact.