Faculty Publications
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Item Mechanical behavior of 3D printed syntactic foam composites(Elsevier Ltd, 2020) Bharath, H.S.; Sawardekar, A.; Waddar, S.; Jeyaraj, J.; Doddamani, M.A three-dimensional printed (3DP), polymer based syntactic foams are developed using hollow glass micro balloons (GMB) dispersed in high density polyethylene (HDPE). This work presents the buckling and vibration response of 3D printed foams subjected to axial compression. The buckling load is estimated using Modified Budiansky Criteria (MBC) and Double Tangent Method (DTM) through the load–deflection plots. The first three natural frequencies and their mode shapes are computed as a function of axial compressive load. It is noted that the natural frequency reduces with an increase in axial compressive load. It is also observed that with an increase in GMB %, the natural frequencies and critical buckling load increases. In mode-1, the natural frequency decreases in pre-buckling regimes and increases exponentially in post-critical loading conditions. Analytical solutions obtained from the Euler-Bernoulli-beam theory are compared with experimental results. It is noted that the fundamental frequency approaches zero when the axial load is equal to the critical load. The critical buckling load is estimated through the vibration correlation technique and compared with the results obtained using DTM and MBC methods. The property map is plotted for buckling load against the density of various composites. © 2020 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 Ltd