Vibration, buckling and dynamic stability of fiber metal laminated plates

Prasad, Elluri Venkata (2019) Vibration, buckling and dynamic stability of fiber metal laminated plates. PhD thesis.

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Abstract

The present study deals with vibration, buckling and parametric resonance characteristics of woven fiber metal laminated plates. Besides this, the tension-tension fatigue behavior of the woven fiber metal laminates is also examined. The numerical analysis for vibration and buckling of fiber metal laminated plates are performed based on finite element method(FEM). Experimental studies are also conducted for vibration and buckling behavior of fiber metal laminated (FML) plates. The parametric resonance characteristics of FML plates subjected to in-plane periodic loading are studied numerically using Bolotin’s technique and FEM. The influences of different parameters viz. aspect ratio, side-to-thickness ratio, number of layers, ply orientation, boundary conditions, static load and dynamic load coefficients on vibration, buckling and parametric instability behavior of fiber metal laminated plates are thoroughly examined in the present study. Tension-tension fatigue characteristics of FMLs are studied through experimental investigations. The effect of incorporation of different weight percentages of nano-alumina on fatigue performance of FMLs is examined by establishing stress to number of cycles to failure (S-N) curves. The micro (through SEM) and macro (hysteresis loops) behavior of nano-modified FMLs is also investigated. Based on first order Reissner–Mindlin theory, the fiber metal laminated plate model is developed to investigate vibration and stability analyses of FML plates. In the present finite element formulation, a four node isoparametric element with five degrees of freedom per node is considered. The primary instability zones are constructed with the help of Mathieu-Hill equation using Bolotin’s method. Eigenvalue solution is performed for vibration, buckling and dynamic stability analysis. The elastic stiffness matrix, geometric stiffness matrix due to applied in-plane load and mass matrix are derived based on minimum potential energy principle. A MATLAB code is developed for parametric investigation on vibration, buckling and dynamic stability behavior of FML plates incorporating both metal and fiber laminated properties. Series of experiments is performed to determine the natural frequencies of FML plates using FFT analyzer with PULSE software under various boundary conditions. The critical buckling loads of FML plates are evaluated experimentally using universal testing machine Instron 8862. The effects of different factors such as aspect ratio, side-to-thickness ratio, boundary conditions and ply orientation on natural frequencies and buckling loads of
FML plates are reported. To investigate the fatigue performance of FMLs, low cycle
tension-tension fatigue tests are conducted at a constant frequency 0.5 Hz and stress ratio of 0.1 using fatigue testing system with WaveMatrix platform. The micro and macro analysis has been carried out to understand the interfacial bonding and hysteresis loop bahavior of nano-modified fiber metal laminates. The experimental and numerical results show that there is significant variation in the
natural frequency and buckling load of FML plates with increase in aspect ratio and side-to-thickness ratio. A good agreement is observed between the experimental and
numerical results for vibration and static stability of FML plates. With increase in plyorientation, there is a reduction in natural frequency and buckling load but the reduction is insignificant. The parametric resonance characteristics of woven FML plates subjected
to in-plane harmonic loading using numerical technique are evaluated and concluded that with the increase of aspect ratio and side-to- thickness ratio, the origin of instability zone shifts to higher natural frequencies and the width of instability region gets increased. With the increase of the static load coefficient, the onset of instability zones moves to lower excitation frequencies and the width of the instability zone become wider. The fatigue life enhancement in FMLs is achieved through nano-modified epoxy. It is clearly observed that with the addition of different weight percentages of nano-alumina to epoxy, the fatigue life gets increased as compared to FML with out nanofiller, this is due to nano particles enhanced the wettability between Aluminum-composite interface. It is found that at 0.1 weight percentage, the FML shows higher fatigue life as compared to 0.2 and 0.3 weight percentage of nano-alumina FMLs. Based on the test results, 0.1 percentage by weight of nano-alumina is the optimum content to get the required tensile strength and fatigue life for the fiber metal laminated plates.

Item Type:Thesis (PhD)
Uncontrolled Keywords:FML plate; Vibration; Buckling; Dynamic instability; Fatigue life; Hysteresis loops
Subjects:Engineering and Technology > Civil Engineering > Structural Engineering
Divisions: Engineering and Technology > Department of Civil Engineering
ID Code:10096
Deposited By:IR Staff BPCL
Deposited On:05 Jun 2020 15:34
Last Modified:05 Jun 2020 15:34
Supervisor(s):Sahu, Shishir Kumar

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