Analytical Study of Buckling of Hybrid Multilayer Plates

Thermal buckling behavior of hybrid multilayer plates was investigated in this paper. Different theories of plates taking into account or neglect the transverse shear are presented and the obtained results by these theories are compared. Nonlinear higher-order strain-displacement relations were considered. Using the principle of potential energy, the critical buckling temperatures are determined. Finally, a parametric study of the influence of various parameters such as: aspect ratios: b/a and a/h, thickness of metal, fiber angle and stacking sequence on the critical buckling temperature is shown and discussed. Numerical results indicate that the addition of metal to a composite material and the consideration of the transverse shear deformation have a significant effect on the thermal buckling behavior of simply supported hybrid multilayer plates

Buckling analysis of functionally graded carbon nanotubes reinforced composite (FG-CNTRC) plate.

In this work, buckling responses of functionally graded single-walled carbon nanotubes (SWCNT) reinforced composite plates with temperature dependent material properties are investigated. The effective material properties of the composite plates are obtained using simple rule of mixture by introducing the CNT efficiency parameter under different thermal environment. In the present analysis, a suitable finite element model of the SWCNT reinforced composite plate is developed using ANSYS parametric design language code in ANSYS environment using Block-Lancoz’s method. An eight noded serendipity shell element (SHELL281) has been used for the discretisation of the developed simulation model from the ANSYS library. The buckling responses of the SWCNT composite plate have been obtained and verified with those of the available published results. The non-dimensional critical buckling load parameters under uniaxial compression, biaxial compression and biaxial compression and tension have been obtained by varying different parameters like, CNT volume fraction, temperature, thickness ratio and support conditions. Finally, the detailed parametric study has been carried out to reveal the influence of different design parameters on the buckling responses through the simulation study

Experimental and numerical study on vibration and buckling characteristics of laminated composite plates

Composite materials are being increasingly used in automotive, civil, marine, and especially weight sensitive aerospace application, primarily because of its specific strength and stiffness. The present research is mostly experimental study based on vibration measurement and buckling behavior of industry driven woven fiber composite panels. The effects of different geometry, boundary conditions, aspect ratio and type of fiber and hygrothermal conditions on the natural frequencies of vibration and buckling of woven fiber composite panels are studied in this investigation. Experiments have also been conducted to study the vibration and buckling characteristics of carbon/glass hybrid plates for different lamination sequence and percentage of carbon and glass fiber. The finite element package, ANSYS 13.0 was used to obtain numerical results and validate the experimental results obtained. The free vibration characteristics are studied with FFT analyzer. The critical buckling load is determined using INSTRON 1195. From the results obtained it was observed that, the frequencies of vibration as well as critical buckling load increased with increase in thickness. As the conditioning temperature deviates from the manufacturing temperature, the natural frequencies decrease gradually. The increase in moisture concentration of the laminate results in decrease in the modal frequencies. The studies on hybrid plates show that they possess the advantages of both their constituent fibres and have properties intermediate to the properties of individual fibres. The effect of percentage composition and sequence of lamination of the fibres on vibrational and buckling characteristics of the composite plates were observed. It was observed that the failure due to tensile load in hybrids is governed by delamination between layers. The buckling results show that stiffer materials on outermost layer give maximum buckling strength compared to those with carbon fibres in inner layers

Thermal buckling analysis of sandwich plates with soft core and CNT-reinforced composite face sheets

Previous studies on the thermal buckling of sandwich plates with composite face sheets indicate that only thin skins with high stiffness and low coefficients of thermal expansion (CTE) can lead to the desired buckling temperatures. Thus, carbon nanotubes (CNTs) that can significantly enhance thermo-mechanical properties of fibre-reinforced polymer composites are used in the present study to increase the critical buckling temperature of sandwich plates with soft core and laminated composite face sheets. First, a comprehensive series of experimental tests are conducted to evaluate the effects of nanotubes on thermo-mechanical properties of the face sheets. The experimental results indicate that using only 0.3% CNTs considerably increases the longitudinal and transverse Young's modulus and shear modulus of the carbon fibre/epoxy composite face sheets. The obtained data also show that CNTs significantly decrease the CTE of composite skins. Subsequently, thermal buckling equations of sandwich plates with CNT-reinforced composite face sheets are derived based on piecewise low-order shear deformation theory (PLSDT). Three analytical, semi analytical, and numerical methods are used to investigate thermal buckling behaviour of the sandwich plates with various boundary conditions. To verify the results, several comparisons are performed, which show that the implemented methods can predict the buckling temperatures of sandwich plates with high accuracy. Finally, a parametric study is conducted to examine the effects of CNTs on the thermal buckling of sandwich plates for different length to thickness ratios, thicknesses of face sheets, stacking sequences of layers, and various types of boundary conditions. The results indicate that CNTs can increase the critical buckling temperature of sandwich plates by 22%-36%, based on the layup, geometrical parameters, and boundary conditions

Buckling and post-buckling behavior of shell type structures under thermo mechanical loads

The thermo mechanical buckling and post-buckling behavior of layered composite shell type structure are considered with the finite element method under the combination of temperature load and applied mechanical loads. To account for through-thickness shear deformation effects, the thermal elastic, and higher-order shear deformation theory is used in this study. The refined higher order theories, that takes into account the effect of transverse normal deformation, is used to develop discrete finite element models for the thermal buckling analysis of composite laminates. Attention in this study is focused on analyzing the temperature effects on buckling and post-buckling behavior of thin shell structural components. Special attention in this paper is focused on studying of values of the hole in curved panel on thermal buckling behavior and consequently to expend and upgrade previously conducted investigation. Using finite element method, a broader observation of the critical temperature of loss of stability depending on the size of the hole was conducted. The presented numerical results based on higher-order shear deformation theory can be used as versatile and accurate method for buckling and post-buckling analyzes of thin-walled laminated plates under thermo mechanical loads

Buckling and post-buckling behavior of shell type structures under thermo mechanical loads

The thermo mechanical buckling and post-buckling behavior of layered composite shell type structure are considered with the finite element method under the combination of temperature load and applied mechanical loads. To account for through-thickness shear deformation effects, the thermal elastic, and higher-order shear deformation theory is used in this study. The refined higher order theories, that takes into account the effect of transverse normal deformation, is used to develop discrete finite element models for the thermal buckling analysis of composite laminates. Attention in this study is focused on analyzing the temperature effects on buckling and post-buckling behavior of thin shell structural components. Special attention in this paper is focused on studying of values of the hole in curved panel on thermal buckling behavior and consequently to expend and upgrade previously conducted investigation. Using finite element method, a broader observation of the critical temperature of loss of stability depending on the size of the hole was conducted. The presented numerical results based on higher-order shear deformation theory can be used as versatile and accurate method for buckling and post-buckling analyzes of thin-walled laminated plates under thermo mechanical loads

Influence of carbon nanotubes on thermal expansion coefficient and thermal buckling of polymer composite plates: experimental and numerical investigations

The first aim of this article is to experimentally explore the effect of multi-walled carbon nanotubes (MWCNTs) on the coefficient of thermal expansion (CTE) of epoxy-based composites. Focusing on the obtained experimental data, two important conclusions can be drawn. (1) Though the CTE of carbon nanotubes (CNTs) is lower than that of neat epoxy, using more CNT does not necessarily decrease the CTE of epoxy polymer. (2) The optimum weight percentage of CNT is 0.3 which can reduce the CTE of epoxy up to 33%. As the second goal of the present research work, thermal buckling analysis of rectangular carbon-fiber-reinforced CNT/epoxy polymer (CFRCNTEP)-laminated composite plates is performed numerically. To this purpose, first, using the obtained experimental data and micro-mechanical models, the thermo-elastic properties of structure are calculated. Then, based on the first-order shear deformation theory (FSDT) and by means of generalized differential quadrature (GDQ) method, the influence of CNTs on the critical buckling temperature of CFRCNTEP composite plates is investigated. The numerical results reveal that MWCNTs can strongly affect thermal buckling behavior of composite plates. It is observed that by adding 0.3 wt. % CNTs into the matrix phase, the critical buckling temperature increases between 35 and 42%

Static and Dynamic Thermomechanical Buckling Loads of Functionally Graded Plates.

In the paper the buckling phenomenon for static and dynamic loading (pulse of finite duration) of FGM plates subjected to simultaneous action of one directional compression and thermal field is presented. Thin, rectangular plates simply supported along all edges are considered. The investigations are conducted for different values of volume fraction exponent and uniform temperature rise in conjunction with mechanical dynamic pulse loading of finite duration

A parametric study on the buckling of functionally graded material plates with internal discontinuities using the partition of unity method

In this paper, the effect of local defects, viz., cracks and cutouts on the buckling behaviour of functionally graded material plates subjected to mechanical and thermal load is numerically studied. The internal discontinuities, viz., cracks and cutouts are represented independent of the mesh within the framework of the extended finite element method and an enriched shear flexible 4-noded quadrilateral element is used for the spatial discretization. The properties are assumed to vary only in the thickness direction and the effective properties are estimated using the Mori-Tanaka homogenization scheme. The plate kinematics is based on the first order shear deformation theory. The influence of various parameters, viz., the crack length and its location, the cutout radius and its position, the plate aspect ratio and the plate thickness on the critical buckling load is studied. The effect of various boundary conditions is also studied. The numerical results obtained reveal that the critical buckling load decreases with increase in the crack length, the cutout radius and the material gradient index. This is attributed to the degradation in the stiffness either due to the presence of local defects or due to the change in the material composition.Comment: arXiv admin note: text overlap with arXiv:1301.2003, arXiv:1107.390