Conference Papers

Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/28506

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Author: search.filters.author.Kulkarni, S.M.Subject: search.filters.subject.Epoxy

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    Bending strength of cenosphere foam cored jute/glass skin sandwiches
    (2004) Kulkarni, S.M.; Sandesh, S.; Sharnappa
    Sandwich construction is widely used in structural application because of its high bending stiffness coupled with lightweight. In design of sandwiches, skin made of high modulus of elasticity is used with core of high shear modulus. This balance is important so that neither material fails long before the other is stressed to accepted level. In the present study, experiments have been carried out on polymeric foam core sandwich beams with jute/epoxy faces. Syntactic polymeric foam cores, which have high compressive strength compared to open cell foams are made by mixing hollow fly-ash particles called cenospheres in a matrix material. The variable considered is the density of the core varied by differing the volume fraction of cenospheres. Cenospheres used in the present study are obtained from flyash, a waste byproduct of thermal power plants using a low cost separation process. Cores with four different volume fractions are prepared and sandwiched between a set of jute fabric layers. It is noticed that as volume fraction of cenospheres increased density is decreasing (1.12 to 0.98 g/cm3). The sandwich beams cut from the samples are tested using standard three-point bending procedure and the results obtained are compared with the results of glass skin sandwich with similar cores. Results showed a large difference in specific strengths of glass and jute skin sandwiches, which could be attributed to high tensile strength of glass fiber compared to jute fiber. There is a decrease of about 13% and 8% from the maximum specific strength for glass skin and jute skin sandwiches respectively at higher volume fractions of cenospheres. This could be traced to the failure of core well before the skin is stressed to accepted level in case of glass skin sandwiches. The jute skin sandwiches exhibited a little flatter specific strength response with respect to volume fraction of cenospheres indicating matching of the features pertaining to jute skin and the core properties. As the specific strength per unit cost of jute approaches that of glass, jute may be used to replace glass fiber with a significant cost advantage for less demanding applications.
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    Comparative study on energy absorbing behavior of stiff and flexible composites under low velocity impact
    (American Institute of Physics Inc. subs@aip.org, 2019) Mahesh, V.; Joladarashi, S.; Kulkarni, S.M.
    This paper deals with the comparative study on the energy absorbing behaviour of the flexible composites with that of stiff composites aiming at automobile cladding application. Two types of composites namely Jute-Epoxy (JE) laminate and Jute-Rubber-Jute (JRJ) sandwich are chosen for the purpose of study under impact velocity varying from 2.5 m/s to 10 m/s. The study is carried out using commercially available finite element simulation software. The energy absorption and damage behavior of both the composites are studied. From the results, it was found that JRJ sandwich absorbs almost 54%, 51.2%, 58.1% and 61.78% more energy compared to JE laminate for impact velocity of 2.5 m/s, 5 m/s, 7.5 m/s and 10 m/s respectively and exhibits compliant nature as opposed to JE laminate which exhibits brittle nature. The energy absorption ratio of JRJ sandwich is more compared to JE laminate. Thus, the JRJ sandwich composites are expected to provide better energy absorption, reduce damage propagation under low velocity impact, thereby making them a potential material for automobile structural protective claddings. © 2018 Author(s).
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    Study on ballistic characteristics of glass-epoxy-rubber sandwiches
    (Trans Tech Publications Ltd ttp@transtec.ch, 2020) Sangamesh, R.; Hiremath, H.; Ravishankar, K.S.; Kulkarni, S.M.
    This article focuses on the Finite Element (FE) analysis of the ballistic performance of the polymer composites. These 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 to forecast the energy absorption, ballistic limit velocity and failure damage mode of the target material. The significant influence of thickness, interlayers and sandwiching effect was studied: the lowest ballistic limit was obtained for 3 mm thick GE. The energy absorption capacity of GRE sandwich was highest among the natural rubber and GE. The work can be extended for the experimental validation purpose so that these polymer composite materials could be utilized in the defense sector for bullet-proofing. © 2020 Trans Tech Publications Ltd, Switzerland.