Applied Mechanics and Materials Vols. 766-767

Abstract: Self-healing composite materials possess healing agent which fills up the crack when ruptured and heals the crack by becoming a tough polymer when stimulated by a catalyst. Dicyclopentadiene (DCPD) in its monomer form is microencapsulated in the shell of Urea Formaldehyde (UF) under different agitation rates to acquire microcapsules of different diameters. The distribution of particle size, surface morphology and the presence of various chemical constituents in the microcapsules were analysed using optical microscopy, SEM and EDAX respectively. An agitation rate of 300 rpm, yielded capsules of diameters ranging from 800μm to 1700μm and at 900rpm the diameters were less than 300μm. Spherical shaped free flowing microcapsules were obtained through insitu polymerisation of dicyclopentadiene in Urea Formaldehyde.

Abstract: This work includes design, fabrication and comparative vibration analysis of multi-layered filament wound composite cylinders of S-Glass epoxy and Basalt epoxy of 500mm length, 100mm diameter and 3mm thickness. The Vibration analyses were done separately on both the cylinders for various end conditions viz., free-free, fixed-free, and fixed-fixed. The natural frequencies of two materials are compared experimentally. Natural frequencies varies with end conditions, material properties, proportions of constituent materials present in the composites, geometrical parameters etc.The natural frequencies of all such parameters were determined using experimental setup which consists of a exciter, accelerometer and DAQ (DEWESOFT 7.0.5 software).

Abstract: Composite structures are used in many critical engineering applications. In the recent times the research has been increased to identify the damage through the vibrational characteristics of the structure. There have been many theoretical and analytical studies on detection of damage involving analysis of the measured modal parameters, mainly the frequencies. The main objective of this paper is to use coupled response techniques for detecting damages in laminated composite cantilever beams with edge cracks using theoretical harmonic analysis. One method to observe the coupled modes is through the emergence of extra new peaks on a frequency response function plot that can be obtained by using standard vibration testing tools. An attempt has been made to develop a methodology by using coupled response measurements and this will happen to appear only when the structural member contains damage. Therefore, the coupled response can be used to monitor and it can be used to determine the damage existence. The frequency response plots are the only possible method to observe coupled response. The new resonance peaks are correlated to the coupled modes and the appearance of these peaks is the damage identification. The finite element analysis software application package ANSYS 12.0 has been used to obtain the new resonance peaks by using harmonic analysis of undamaged and damaged structures to enable comparisons that throw light on the presence of damages in the structure.

Abstract: Constructions of pressure vessels like rocket launch vehicles, missiles, rocket propellant tanks, and filament wound pipes for civil and military applications are made out of high strength, high stiffness and light weight composites filaments. Filament winding techniques are used for fabrication of such cylinders and pipes. Many materials like glass fibers, carbon fibers and Kevlar fibers are used due to their good strength when it is subjected to internal pressure as well as external pressure. Basalt fibers are new materials that are fabricated from hard dense basalt rocks. Basalt fibers can be used in the place glass fibers due to their good mechanical behavior when subjected to internal pressure. Plates and beams generally resists bending loads and pipes and tube structures resists internal forces developed through internal and external pressure. This work concentrates the fabrication of filament wound pipes using filament wound techniques and the burst pressure test is carried out. In fuel tanks of rockets, If any one of the layer fails due to internal pressure, there will be mild leakage. For this reason it is mandatory to find out the ply by ply failure. The first ply failure of basalt filament wound pipes subjected to internal pressure is calculated using Finite element analysis. Then the stress and progressive failure analysis was carried out. Maximum stress failure criterion is used for the finite element analysis.

Abstract: Thermoplastic materials gain their characteristic properties because of their ability to crystalline from the melt i.e. liquid to semi crystalline solids. Many authors have made several efforts in blending of various systems viz. binary, tertiary etc. to be compatible with each other to achieve enhancement of target properties. In this connection ABS, PC and its blends are studied for various applications starting from compact disc to various parts for automobiles. But there is a never ending challenge in selecting the suitable compatibilizer for two or more materials which are to be blended. Due to the recycle ability of thermoplastic materials like Acrylonitrile Butadiene Styrene, Poly Ethylene, Poly Propylene polycarbonate invites the development of their blends/composites which will fulfill day-to-day needs of present and future generations. Hence an attempt is made in the present paper to do review on the mechanical properties viz. tensile, flexural and impact of a novel blended materials i.e. polycarbonate, glass filled polycarbonate and their blends along with the results exist in the literature.

Abstract: This study targets on wear and frictional characteristics of hybrid polymer. Experiments are carried out on hybrid polymers using reciprocating wear testing machine by sliding against mating steel plate. General purpose resin is blended with Cashew nut shell is used as test specimen. The values of frictional force, frictional coefficient and wear were measured to study the influence of accelerated wear.

Abstract: In the present study, the aluminum based hybrid composite with Silicon Carbide (SiC) and Boron Carbide (B₄C) particles are prepared through the stir casting process and subjected to Abrasive Water Jet Machining (AWJM). The pressure, standoff distance and traverse speed are considered as the input process parameters and the output response such as Kerf angle, Material Removal Rate (MRR) and Surface Roughness (Ra) are measured and optimized using Grey Relational Analysis (GRA). The Analysis of Variance (ANOVA) and the F-test are performed to understand the contribution and the significant level of importance of each input parameter over the output response. The experimental result shows that the traverse speed and the standoff distance contributed more on affecting the performance, with a contribution of 62.14% and 18.43% respectively.

Abstract: The desire of weight reduction and improved damage tolerance characteristics of the aircraft structures throws a light on the development on Fiber Metal Laminates (FML), one of the hybrid composites, with the combination of metallic and non-metallic layers. In this study, laminates of alternating layers of aluminium (metal) and glass fibers with Woven Roving mat is fabricated. Tensile test based on ASTM standard are then conducted on the laminates to study their yield properties. The interfacial bonding between the layers are analyzed using the Scanning Electron Microscopy of tested specimens.

Abstract: Since the last ten years, research happenings in the field of nanomaterials have been increased dramatically. Materials scientists and researchers have realized that the mechanical properties of materials can be altered at the fundamental level, i.e. at the atomic-scale. Carbon nanotubes have been well recognized as nanostructural materials that can be used to modify mechanical, thermal and electrical properties of polymer-based composite materials, because of their excellent properties and perfect atom arrangement. In geneal, scientific research related to the nanotubes and their co-related polymer based composites can be distinguished into four particular scopes: (i) production of high purity and well-regulated nanotubes, in terms of their size, length and chiral arrangement; (ii) enhancement of interfacial bonding strength between the nanotubes and their surrounding matrix; (iii) control of the dispersion properties and alignment of the nanotubes in nanotube/polymer composites and (iv) applications of the nanotube in real life. Research shows that addition of resin with nanoclays permits to retain stiffness without losing toughness, and also improving barrier and thermal properties. Dynamic Mechanical Analysis (DMA) studies revealed that filling the carbon nanotube into epoxy can produce a 90% enhancement in storage modulus and a 22°C increase in Tg. Addition of nanoclay and epoxy with nanotubes forms a hybrid nanocomposite.