P S Shivakumar Gouda

Studies on effect of pre-crack length variation on Inter-laminar fracture toughness of a Glass Epoxy laminated composite

Laminates of fiber reinforced polymer composites are good in in-plane properties and inherently weak in through thickness direction. To address this through thickness properties, the inter-laminar fracture toughness (GIc and GIIc) of a unidirectional (UD) Glass epoxy composite laminates were subjected to Mode-I and Mode-II loadings. Experiments were conducted using Double cantilever beam (DCB) and End notch flexure (ENF) specimens with varying pre-crack lengths. Mode I energy release rate (GIc) were also evaluated with modified beam and modified compliance theories. The experimental results reveal that, GIc fracture toughness increases with increasing in pre-crack length, where as in GIIc the effect of increase in pre-crack length exhibits reduced fracture toughness.

Fracture Toughness of Glass Epoxy Laminates Using Carbon Nano Particles and ETBN Rubber

Fiber-reinforced laminated composites have excellent mechanical properties along the fiber in-plane direction. However, they do not have very good properties in the transverse direction. The objective of this research is to deal with this problem by using graphene oxide (GO), plasma-treated multiwall carbon nanotubes, and nanodiamond extra pure powder with epoxy-terminated butadiene nitrile liquid rubber to improve the through-thickness fracture toughness of glass/epoxy unidirectional pre-preg laminates. The experimental results show that by adding carbon nanoparticles with rubber in small quantities, the mode-I interlaminar critical energy release rate can be improved by 50 to 103 %. Furthermore, it was observed that there was an increase in flexural stiffness by 15 % with the addition of nanodiamond extra pure powder to rubber. However, when GO was used, the mode-I interlaminar fracture toughness improvement was reduced as compared to other nanoparticles modified by glass/epoxy fiber laminates. The fracture surfaces were analyzed using scanning electron microscopy to understand the increase in toughness in modified glass epoxy pre-peg laminate system.

Investigation on pseudo-ductility to improve mechanical behavior in glass-cellulose epoxy composites

Nowadays composite materials exhibit sudden and catastrophic failure, which is undesirable for several applications. A new class of hybrid laminates was prepared using semi-automated draw down coating method with varying surface coating densities on unidirectional (UD) Glass fiber. Cellulose particles were coated on UD Glass fiber to investigate the effect of pseudo-ductility to improve mechanical behavior. Glass Cellulose epoxy hybrid laminate was fabricated with 5%, 7.5% and 10% of cellulose. Coating with 5% Cellulose produces a coating density of 319.08 g/m2 and exhibits the appreciable pseudo ductile tensile stress-strain behavior with a non-linear variation at second part followed by linear variation at initial region. The response of tensile stress had shown 27% improvement in tensile modulus (330MPa) as compared to neat glass epoxy laminate with 0.04% of pseudo ductile strain. Further, flexural strength and inter-laminar shear strength of each specimen configuration were calculated and found good improvement in flexural strength with cellulose coated samples as compared to Glass-Epoxy laminate.

Thermal analysis on x-ray tube for exhaust process

It is great importance in the use of X-rays for medical purposes that the dose given to both the patient and the operator is carefully controlled. There are many types of the X- ray tubes used for different applications based on their capacity and power supplied. In present thesis maxi ray 165 tube is analysed for thermal exhaust processes with ±5% accuracy. Exhaust process is usually done to remove all the air particles and to degasify the insert under high vacuum at 2e-05Torr. The tube glass is made up of Pyrex material, 95%Tungsten and 5%rhenium is used as target material for which the melting point temperature is 3350°C. Various materials are used for various parts; during the operation of X- ray tube these waste gases are released due to high temperature which in turn disturbs the flow of electrons. Thus, before using the X-ray tube for practical applications it has to undergo exhaust processes. Initially we build MX 165 model to carry out thermal analysis, and then we simulate the bearing temperature profiles with FE model to match with test results with ±5%accuracy. At last implement the critical protocols required for manufacturing processes like MF Heating, E-beam, Seasoning and FT.

Artificial Neural Networks for the Prediction of Wear Properties of Al6061-TiO2 Composites

The exceptional performance of composite materials in comparison with the monolithic materials have been extensively studied by researchers. Among the metal matrix composites Aluminium matrix based composites have displayed superior mechanical properties. The aluminium 6061 alloy has been used in aeronautical and automotive components, but their resistance against the wear is poor. To enhance the wear properties, Titanium dioxide (TiO2) particulates have been used as reinforcements. In the present investigation Back propagation (BP) technique has been adopted for Artificial Neural Network [ANN] modelling. The wear experimentations were carried out on a pin-on-disc wear monitoring apparatus. For conduction of wear tests ASTM G99 was adopted. Experimental design was carried out using Taguchi L27 orthogonal array. The sliding distance, weight percentage of the reinforcement material and applied load have a substantial influence on the height damage due to wear of the Al6061 and Al6061-TiO2 filled composites. The Al6061 with 3 wt% TiO2 composite displayed an excellent wear resistance in comparison with other composites investigated. A non-linear relationship between density, applied load, weight percentage of reinforcement, sliding distance and height decrease due to wear has been established using an artificial neural network. A good agreement has been observed between experimental and ANN model predicted results.

Interlaminar Fracture toughness in Glass-Cellulose Reinforced Epoxy hybrid composites

Laminates of fibre reinforced compositesare weak in through thicknessbut strong in fibre direction, this lead to development of hybridizationconcept in polymer composites. In this work a new method of disperssing cellulose micro particleson unidirectional (UD) Glass fibre epoxy composite using semi-automated draw down coating technique was adopted to enhance fracture toughness.Test results show that by adding cellulose increases the load carrying competency by 32% in mode-I as compare to Glass- Epoxy composite samples. Imrovement in interlaminar critical energy release rates (GiC and GnC) up to 55% in Mode -I and 19 %in Mode -II respectively was also observed. This enahancement in fracture toughnees is due to the amount of fiber bridging seen during crack initiation and propagation.

Design, analysis and testing of x-ray tube for next generation x-ray machines

A conceptual design of x-ray metal tube frame assembly is done to establish the technical feasibility and characterize the performance of a base design of x-ray metal tube frame assembly to meet the experimental critical to qualities (CTQs) of x-ray tube at 72 kW for 20 seconds. Experimental test configuration with linear variable differential transformers (LVDTs) & thermo-couples is set to study the thermal prediction of x-ray tube with model results. Graphs of temperature versus time and deflection versus time shows curve shape magnitudes within 5% and 1%. A thermal - structural analysis is considered in analyzing the thermal - structural behavior in x-ray metal tube by considering worst protocol as 3.2 kW in steady state condition and 14.4 kW in transient state condition for 30 seconds. This analysis is done by doing a conceptual design of x-ray metal tube frame assembly with major modifications in frame and electron collector based on thermal - structural results. 3D modelling of x-ray metal tube frame assembly is done in Creo parametric 2.0 CAD software and analysis is done in ANSYS 16.1 simulation software. FEA results of conceptual design are in good agreement with CTQs results of x-ray tube at 72 kW for 20 seconds.