Faculty Publications

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Delamination analysis in drilling process of glass fiber reinforced plastic (GFRP) composite materials
(2007) Mohan, N.S.; Kulkarni, S.M.; Ramachandra, A.
Machining processes are generally used to cut; drill, or contour composite laminates for building products. In fact, drilling is one of the most commonly used manufacturing processes to install fasteners for assembly of laminate composites. The material anisotropy resulting from fiber reinforcement heavily influences the machinability during machining. Machining of fiber reinforced plastic (FRP) components is often needed in spite of the fact that most FRP structures can be made to near-net shape and drilling is the most frequently employed secondary machining process for fiber reinforced materials. Therefore, the precise machining needs to perform to ensure dimensional stability and to obtain a better productivity of the component. The drilling parameters and specimen parameters evaluated were speed, feed rate, drill size and specimen thickness. A series of experiments were conducted using TRIAC VMC CNC machining center to machine the composite laminate specimens at various cutting parameters and material parameters. The measured results of delamination at the entry and exit side of the specimen were measured and analyzed using commercial statistical software MINITAB14. The experimental results indicated that the specimen thickness, feed rate and cutting speed are reckoned to be the most significant factors contributing to the delamination. A signal-to-noise ratio is employed to analyze the influence of various parameters on peel up and push down delamination factor in drilling of glass fibre reinforced plastic (GFRP) composite laminates. The main objective of this study is to determine factors and combination of factors that influence the delamination using Taguchi and response surface methodology and to achieve the optimization machining conditions that would result in minimum delamination. From the analysis it is evident that among the all significant parameters, specimen thickness and cutting speed have significant influence on peel up delamination and the specimen thickness and feed have more significant influence on push down delamination. Confirmation experiments were conducted to verify the predicted optimal parameters with the experimental results, good agreement between the predicted and experimental results obtained to be of the order of 99%. © 2007 Elsevier B.V. All rights reserved.
Instrumented ballistic performance of jute/epoxy sandwich with functionally graded rubber core
(Inderscience Publishers, 2012) Doddamani, M.R.; Kulkarni, S.M.
The qualitative analysis of instrumented ballistic impact for jute-epoxy sandwiches with fly ash reinforced functionally graded (FG) flexible, compliant rubber core is presented. An attempt is made to study the influence of fly ash weight fraction, jute orientation and core to total thickness (C/H) of sandwich on ballistic performance. Experiments are designed based upon L9 orthogonal array. Analysis of variance (ANOVA) is performed on recorded data to investigate the influence of parameters on ballistic response. An optimal parameter combination is determined leading to higher energy absorption and lower energy required for skin pullout by the bullet. A correlation derived from the results of Taguchi experimental design is proposed as a predictive equation for estimation of energy absorption of sandwiches. Furthermore, for arresting bullet optimum stack thickness of sandwich configuration is presented. Finally, the potential benefits for using such materials as a replacement for sand bags in guarding posts is highlighted. Copyright © 2012 Inderscience Enterprises Ltd.

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