Materials Science Forum Vol. 978

Abstract: The basic aim in using the waste is to reduce the level of pollution that harms the environment. However a proper approach to manage waste or reduce the level of waste helps in conservation of resources for the succeeding generation and contributes to a healthy, clean and pollution free environment. In recent years, control on two major ecological issues such as waste disposal and noise pollution can help in achieving a green and healthier environment. For disposal, waste tires are normally burnt. Extinguishing fire from tire is very difficult. The fire develops a thick, dark smoke which contains CO₂, SO_2, cyanide, and products of butadiene & styrene. This study focuses on the fabrication of composites from epoxy-waste tire crumb by hand lay-up method and the investigation of its acoustical property by Impedance tube method using LABVIEW. In the present work three different materials such as PVC, Stainless Steel and Glass has been used to prepare impedance tube as per ASTM standards. All the sound testing has carried out at a frequency range of 500 Hz to 5000 Hz. This study clearly shows a promising waste management for tyres by developing a cost effective composite and thus contributing to a sustainable waste granule (waste tyre) reinforced polymer composite industry.

Abstract: Polymer composites are gaining attention due to their superior thermal properties. Especially carbon black /carbon nanotubes/ graphene filled polymer composites are used in energy harvesting, thermal actuators and MEMS. The coefficient of thermal expansion (CTE) is one of the most important properties in the polymer composite. In the present study, thermal expansion of polydimethylsiloxane (PDMS) matrix is filled with carbon black particle of varied volume fraction is modeled. Two-dimensional finite element (FE) model is computed in order to explain the thermal expansion behavior of the polymer composite and same is carried out for ambient to 70 K temperature. A 2D regular arrangement of circular particle packing model is set up and simulated. The FE model predicts that filler geometry has a little effect on the thermal expansion than the percentage of filler in the composite. Thermal expansion of composite is compared with the theoretical model. It shows that the CTE of composite reduces as the filler percentage increase, also gives good agreement in the both models. Hence, it is found that the addition of carbon black to the polymer composite could make it perform significantly better in thermal expansion.

Abstract: This article focuses on the Finite Element (FE) analysis of the ballistic performance of the polymer composites consisting of natural rubber (NR), glass-epoxy (GE) and glass-rubber-epoxy (GRE) sandwich of different thicknesses (3, 6 and 9 mm) under the impact of the conical nose projectile for a velocity variation of (180, 220 and 260 m / s). FE modeling was carried out in direction to forecast the energy absorption, ballistic limit velocity and failure damage mode of the target materail. The significant influence of thickness, interlayer and sandwiching effect was studied: the lowest ballistic limit was obtained for 3 mm thick GE. Energy absorption capacity of GRE sandwich was highest among the natural rubber and GE. In future, the work can be extended for the experimental validation purpose, so that these polymer composite materials could be utilized to defence sector for bullet-proofing.

Abstract: This study was designed to examine the consequences of lamination sequence, fiber orientation and hybridization on tensile, flexural, physical, and inter-laminar properties of Jute-epoxy laminated composites and its hybrid. These laminates are partially biodegradable hence environment-friendly. Here six laminated specimens were fabricated using hand lay-up techniques with 4 layers of fiber or 40% fiber loading as per the ASTM standard. Samples were prepared with three different orientation of 0⁰, 30⁰ and 60⁰ to the loading direction. The experimental outcome revealed that composite with 30⁰ fiber orientation gives a better result in flexural, microhardness, and interlaminar shear strength. Generally, Final failure was due to delamination, fiber pull-out, fiber failure or matrix cracking. Scanning electron micrographs were used for improved understanding of fracture mechanics. A substantial quantity of voids, improper alignment, fiber waviness and heterogeneous interface were found resulted in premature failure.

Abstract: FRP laminates are used in several industries such as automobile, aircraft’s, spacecraft’s, defense and etc.., where high strength-to-weight ratio is the primary criteria. FRP laminates offer high design and material tailoring properties but are highly susceptible to delamination and debonding under out-of-plane low velocity impact which induces barely visible impact damage (BVID) inside the structures. A lot of research investigation is going on related to damage resistance behavior of FRP laminates under out-of-plane impact loading. But very less concentration is paid to the FRP laminates behavior under in-plane low impact loading. In this numerical analysis in-plane low velocity impact loading is carried out on a bidirectional plain woven glass fiber reinforced epoxy laminate (GFRP) using LS-DYNA. A hemispherical impactor of mass 5kg and diameter of 10mm is impacted at 0.5, 1.0 and 1.5m/sec velocity on [(0⁰/90⁰)/(+45⁰/-45⁰)/(+45⁰/-45⁰)/(0⁰/90⁰)]_S layup design. Two boundary conditions complete edge and corner constraining boundary conditions are considered for numerical analysis. Force vs. time, energy vs. time, displacement vs. time plots are used to evaluate the analysis.

Abstract: This paper presents a free vibration analysis of un-damped woven roving laminated composite plate using Classical Laminate Plate Theory (CLPT), for different boundary conditions. The fiber glass/epoxy woven roving laminated composite plates have been prepared using hand layup method. Three different fiber orientations have been considered for the fiber glass/epoxy laminated composite plate, having 50% each percentage by volume of glass and epoxy. Effects of fiber orientation on different mechanical properties such as density, hardness, impact strength and impact strength have been studied. Finite element modeling of the composite plates has been performed using different boundary conditions such as CCCC, CFCF, and CFFF and the fundamental frequencies obtained from the computational modeling have been compared with the available literature.

Abstract: The present work reports the influence of various Electric-Discharge Machining (EDM) process parameters on the surface morphology and EDM characteristics of thixoformed A356-5TiB₂ in-situ composites. The important EDM parameters such as pulse current, pulse-on time, Duty Cycle, etc. on Surface morphology and Material removal rate of the thixoformed A356-5TiB₂ in-situ composites have been investigated. Further, the machining parameters were optimized using Fuzzy-logic and grey relational analysis approach. The effect of EDM parameters and their interactions on the erosion behavior of A356-5TiB₂ in-situ composites on various aspects of surface integrity and Material Removal rate (MRR) is reported. The surface integrity during EDM was characterized by Scanning Electron Microscope and analyzed from the machinability point of view. Thus, this work is an attempt to study the machinability behavior of thixoformed A356-5TiB₂ in-situ composites.

Abstract: Fiber reinforced polymeric (FRP) composite materials are currently used in numerous structural and materials related applications. But, during their in-service period these composites were exposed to different changing environmental conditions. Present investigation is planned to explore the effect of thermal shock exposure on the mechanical properties of nanoTiO₂ enhanced glass fiber reinforced polymeric (GFRP) composites. The samples were conditioned at +70°C temperature for 36 h followed by further conditioning at – 60°C temperature for the similar interval of time. In order to estimate the thermal shock influence on the mechanical properties, tensile tests of the conditioned samples were carried out at 1 mm/min loading rate. The polymer phase i.e. epoxy was modified with different nanoTiO₂ content (i.e. 0.1, 0.3 and 0.5 wt. %). The tensile strength of 0.1 wt.% nanoTiO₂ GFRP filled composites exhibited higher ultimate tensile strength (UTS) among all other composites. The possible reason may be attributed to the good dispersion of nanoparticles in polymer matrix corresponds to proper stress transfer during thermal shock conditioning. In order to access the variations in the viscoelastic behavior and glass transition temperature due to the addition of nanoTiO₂ in GFRP composite and also due to the thermal shock conditioning, dynamic mechanical thermal analysis (DMTA) measurements were carried out. Different modes of failures and strengthening morphology in the composites were analyzed under scanning electron microscope (SEM).

Abstract: The exceptional and distinctive properties of the allotropes of carbonaceous nanomaterials like carbon nanotubes and graphene have attracted many researchers and engineers to enhance the performance of fibrous polymeric composites. This article extrapolates the synergetic impact of carbon nanotube (CNT) and multi-layered graphene (MLG) reinforcement onto the mechanical performance of glass fiber/epoxy composites. Magnetic stirring and ultra-sonication process have been carried out under optimized parameters for incorporation of CNT-MLG into the epoxy polymer. Incorporation of 0.1wt% of carbon nanotube to the glass fiber/epoxy composites enhances a flexural strength of 10% and addition of 0.1 wt. % of multi layered graphene to the glass fiber/ epoxy composites enhances a flexural strength of 6% when differentiated with neat GE. Embodiment of 0.1 wt. % CNT and MLG to the glass fiber/epoxy composites in three different ratios like 1:1, 1:2 and 2:1 showcases a 13%, 12.25% and 14.7% enhancement in the flexural strength respectively with respect to the neat glass fiber/epoxy composites when tested at room temperature. Among them, the ratio 2:1(CNT: MLG) contributes higher strength due to the combined action of high aspect ratio of CNT and higher specific surface area of multi-layered graphene thus, facilitating efficient stress transfer from matrix to the reinforcements. Thermal characterizations have been carried out using differential scanning calorimetry (DSC). The fractography of the samples is examined through the scanning electron microscope.

Abstract: Natural fibres have gained popularity due to their use in fabrication of biodegradable polymer composites which are not only non-polluting but are also light weight and inexpensive. Abaca fibres are known for their remarkable properties for which their polymer composites are used in automotive applications. However, hydrophilicity and compatibility with polymer matrices are the two major drawbacks of natural fibres which restrict their use as reinforcements in polymer composites. Therefore, present study deals with the surface modifications of abaca fibre using potassium permanganate and sodium hydroxide solutions to enhance crystallinity and reduce hydrophilicity of abaca fibres. Further, the surfaces of untreated and treated fibre were investigated with the help of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. Surface treatment of abaca fibre led to the removal of unwanted wax, and other amorphous materials which was confirmed through FTIR analysis. Crystallinity index was found to be 57%, 59% and 61% for untreated, NaOH treated and KMnO₄ treated abaca fibre respectively.