Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
7 results
Search Results
Item Influence of axial compressive loads on buckling and free vibration response of surface-modified fly ash cenosphere/epoxy syntactic foams(SAGE Publications Ltd info@sagepub.co.uk, 2018) Waddar, S.; Jeyaraj, P.; Doddamani, M.This work deals with experimental buckling and free vibration behavior of silane-treated cenosphere/epoxy syntactic foams subjected to axial compression. Critical buckling loads are computed from compressive load–deflection plots deduced using universal testing machine. Further, compressive loads are applied in the fixed intervals until critical loading point on different set of samples having similar filler loadings to estimate natural frequency associated with the first three transverse bending modes. Increasing filler content increases critical buckling load and natural frequency of syntactic foam composites. Increasing axial compressive load reduce structural stiffness of all the samples under investigation. Syntactic foams registered higher stiffness compared to neat epoxy for all the test loads. Similar observations are noted in case of untreated cenosphere/epoxy foam composites. Silane-modified cenosphere embedded in epoxy matrix registered superior performance (rise in critical buckling load and natural frequencies to the tune of 23.75% and 11.46%, respectively) as compared to untreated ones. Experimental results are compared with the analytical solutions that are derived based on Euler–Bernoulli hypothesis and results are found to be in good agreement. Finally, property map of buckling load as a function of density is presented by extracting values from the available literature. © The Author(s) 2018.Item Buckling and free vibration behavior of cenosphere/epoxy syntactic foams under axial compressive loading(ASTM International, 2018) Waddar, S.; Jeyaraj, P.; Doddamani, M.; Gupta, N.The buckling and free vibration behavior of cenosphere/epoxy syntactic foams under axial compressive loading are investigated experimentally in this work. The buckling load is obtained from the load-deflection curve based on the Double Tangent Method (DTM) and Modified Budiansky Criteria (MBC). Furthermore, the influence of an axial compression load on the natural frequencies associated with the first three transverse bending modes is analyzed. Finally, the buckling loads predicted using DTM and MBC are compared to the buckling load calculated based on the vibration correlation technique. It is observed that the buckling loads predicted through the three different methods are in close agreement. The experimental results revealed that the buckling load and natural frequency of the syntactic foams increase with the cenosphere volume fraction. It is observed that the natural frequencies reduce with increases in the axial compression load for all the modes. However, a rapid increase in the fundamental frequency is observed when the compressive load is near and beyond the critical buckling load. © © 2018 by ASTM International.Item Buckling and vibration behaviour of syntactic foam core sandwich beam with natural fiber composite facings under axial compressive loads(Elsevier Ltd, 2019) Waddar, S.; Jeyaraj, P.; Doddamani, M.; Barbero, E.An experimental study of buckling and dynamic response of cenosphere reinforced epoxy composite (syntactic foam) core sandwich beam with sisal fabric/epoxy composite facings under compressive load is presented. Influence of cenosphere loading and surface modification on critical buckling load and natural frequencies of the sandwich beam under compressive load is presented. The critical buckling load is obtained from the experimental load-deflection data while natural frequencies are obtained by performing experimental modal analysis. Results reveal that natural frequencies and critical buckling load increase significantly with fly ash cenosphere content. It is also observed that surface modified cenospheres enhance natural frequencies and critical buckling load of the sandwich beam under compressive load. Vibration frequencies reduce with increase in compressive load. Fundamental frequency increases exponentially in post-buckling regime. Experimentally obtained load-deflection curve and natural frequencies are compared with finite element analysis wherein results are found to be in good agreement. © 2019 Elsevier LtdItem Effect of axial compression on dynamic response of concurrently printed sandwich(Elsevier Ltd, 2021) Bharath, H.S.; Waddar, S.; Bekinal, S.I.; Jeyaraj, J.; Doddamani, M.In this work, the sandwich is concurrently realized using high density polyethylene (HDPE) skins and syntactic foam core through three-dimensional printing (3DP). Syntactic foam core is printed using lightweight feedstock filaments having glass microballoons (GMBs) by 20–60 vol% embedded in HDPE. These lightweight filaments are used as feed material in FFF (fused filament fabrication) based three-dimensional printer. The concurrently printed sandwich is loaded axially in a compressive mode for investigating the influence of GMB loading on buckling and natural frequency. The experimental load–deflection data and modal analysis are utilized for estimating critical buckling load and natural frequencies, respectively, under axial compression. Increasing GMB content enhances load to buckle and frequency of the printed sandwiches. The natural frequency decrease with higher compressive loads. Furthermore, the fundamental natural frequency increases exponentially when these printed sandwiches are subjected to axial compression loads that are higher than the load required for critical buckling. The load–deflection data and frequency obtained experimentally are compared with numerical predictions deduced using finite element analysis (FEA), which are noted to match well. © 2020 Elsevier LtdItem Dynamic behavior of concurrently printed functionally graded closed cell foams(Elsevier Ltd, 2021) Dileep, B.; Prakash, R.; Bharath, H.S.; Jeyaraj, J.; Doddamani, M.In this work, functionally graded foams (FGFs) of closed cell types are three-dimensionally printed (3DP) concurrently. These closed cell syntactic foams are manufactured by reinforcing 20, 40, and 60 vol% hollow glass microballoons (GMBs) in the high density polyethylene (HDPE) matrix and are investigated for their mechanical buckling and free vibration response. The critical buckling load (Pcr) of the FGFs are evaluated using the Double Tangent Method (DTM), Modified Budiansky Criteria (MBC), and Vibration Correlation Technique (VCT). It is observed that Pcr evaluated by all three methods are in good agreement. Among all FGFs, FGF-2 exhibited higher buckling strength with 22–26% higher than FGF-1 and FGF-3. Under no-load and uniaxial compressive loads, the first three natural frequency of FGFs and their corresponding damping factors are evaluated. At first mode, the natural frequency of FGFs decreases in the pre-buckling zone and started increasing in the post-buckling zone. Damping factor exhibited reverse trend compared to the trend shown by the natural frequencies. Among all FGFs, FGF-2 (20-40-60 GMB gradation) exhibited better natural frequency. Experimental results are compared with a finite element based simulation results. © 2021 Elsevier LtdItem Buckling and dynamic responses of 3D printed nanocomposites and their graded variants(Elsevier Ltd, 2023) Kumar, S.; Ramesh, M.R.; Jeyaraj, P.; Doddamani, M.The experimental and numerical investigations are carried out for buckling and vibration of 3D printed functionalized MWCNTs/HDPE based nanocomposite (NC) and their functionally graded nanocomposite (FGNC) variants. Pcr(critical buckling load) is computed through MBC (modified budiansky criteria) and DTM (double tangent method) techniques. It is observed that Pcr of the 3D printed NCs and FGNCs increases with the functionalized MWCNTs content. The Pcr values for the NCs (H0.5-H5) computed using DTM and MBC increased in the range of 16–79%, while for FGNC-1 (H0.5-H1-H3) and FGNC-2 (H1-H3-H5), the Pcr increased from 54 to 91% compared to HDPE. Further, it is observed that the natural frequency of the NCs and FGNCs increases with the functionalized MWCNTs loading while decreases with rise in compression. The natural frequency of the NCs (H0.5-H5) and FGNCs increased up to 41% than HDPE. The highest Pcr and the natural frequency is noted for H5 and FGNC-2 prints. The experimental and numerical results showed good agreement. © 2023 Elsevier LtdItem Dynamic response of 3D printed functionally graded sandwich foams(Emerald Publishing, 2023) Bonthu, D.; Bharath, B.; Bekinal, S.I.; Jeyaraj, J.; Doddamani, M.Purpose: The purpose of this study was to introduce three-dimensional printing (3DP) of functionally graded sandwich foams (FGSFs). This work was continued by predicting the mechanical buckling and free vibration behavior of 3DP FGSFs using experimental and numerical analyses. Design/methodology/approach: Initially, hollow glass microballoon-reinforced high-density polyethylene-based polymer composite foams were developed, and these materials were extruded into their respective filaments. These filaments are used as feedstock materials in fused filament fabrication based 3DP for the development of FGSFs. Scanning electron microscopy analysis was performed on the freeze-dried samples to observe filler sustainability. Furthermore, the density, critical buckling load (Pcr), natural frequency (fn) and damping factor of FGSFs were evaluated. The critical buckling load (Pcr) of the FGSFs was estimated using the double-tangent method and modified Budiansky criteria. Findings: The density of FGSFs decreased with increasing filler percentage. The mechanical buckling load increased with the filler percentage. The natural frequency corresponding to the first mode of the FGSFs exhibited a decreasing trend with an increasing load in the pre-buckling regime and an increase in post-buckled zone, whereas the damping factor exhibited the opposite trend. Originality/value: The current research work is valuable for the area of 3D printing by developing the functionally graded foam based sandwich beams. Furthermore, it intended to present the buckling behavior of 3D printed FGSFs, variation of frequency and damping factor corresponding to first three modes with increase in load. © 2023, Emerald Publishing Limited.