Buckling and Dynamic Characteristics of Non-Uniformly Heated FGCNT Polymer Nanocomposite Plate

Abstract

Nature of temperature variation influences buckling and dynamic behaviour of structures under thermal load. However, studies on buckling and dynamic behaviour of non-uniformly heated structures are very limited. In present work, influence of non-uniform temperature variation on buckling strength of beams made of aluminium and laminated glass-epoxy materials are investigated experimentally. A novel experimental set-up, built in-house, is developed to perform this investigation. The load vs deflection curve obtained experimentally is used to predict the thermal buckling strength using inflection point method. Non-linear finite element analysis, considering the initial geometric imperfection, has been carried out to compare the experimentally obtained typical load-deflection curve. Experimental and numerical results revealed that critical buckling temperature of the non-uniformly heated beam greatly differs from the uniformly heated beam. It is also observed that different locations of heat source and resulting non-uniform temperature variations influence the critical buckling temperature significantly depending on the location of heat source. With the confidence gained from the results obtained from experimental investigation, a detailed numerical investigation is carried out on Functionally Graded Carbon Nanotube (FG-CNT) reinforced polymer composite plate to obtain the influence of non-uniform heating on the buckling, free vibration and forced vibration response. The effective material constants of the plate are obtained using the extended rule of mixture along with efficiency parameters of the CNT (to include geometry-dependent material properties). Influence of boundary conditions, iiaspect ratio, functional grading of the CNT, non-uniform heating on thermal buckling, free and forced vibration behaviour of the heated plate are analysed. The acoustic response of the plate is analysed by solving the Rayleigh integral. It is observed that temperature fields and functional grading of CNTs influences the critical buckling temperature of the plates. Further, nature of functional grading showed significant change in buckling mode shapes irrespective of the boundary conditions. The first few natural frequencies of the plate under thermal load decreases as the temperature increases and they are influenced significantly by the nature of temperature field. The free vibration modes of the rectangular plates are sensitive to the nature of temperature field whenever there is a free edge associated with the boundary condition. It is observed that, the plates with FG-X type CNT distribution showed better thermal buckling strength and free vibration characteristics in comparison to other types of functional grading. The resonant amplitude of vibration and acoustic response are significantly influenced by the nature of different functional grading and rise in thermal load. This reflects in the band wise calculation of sound power also which recommends the CNT functional grading with X distribution along the thickness direction for lower frequency level. Considerable increase in sound power level has been observed with increase in thermal load in the lower frequency range due to the variation in the stiffness associated with the plate. Similar variation in vibroacoustic response has been observed with increase in the CNT loading also.