In this study, the free vibration characteristics of variable stiffness laminated composite shells is numerically studied using a higher-order accurate theory. The unique feature of the variable stiffness composites is that the fiber orientation within the lamina changes continuously leading to spatial variation of stiffness of the resulting laminate. A systematic parametric study is conducted to bring out the influence of fiber orientation within and across the laminae, shell geometry and the structural theory on the fundamental frequency. The influence of environmental factors such as the temperature and the presence of moisture is also considered. It is inferred that the spatial variation of stiffness due to curvilinear fibres introduces additional flexibility in designing structures made of such materials. © 2018 Elsevier Ltd

Sundararajan Natarajan

Department of Mechanical Engineering

Venkatachari A

Ganapathi M

Fibers

Laminating

Shells (structures)

Stiffness

vibration analysis

CURVILINEAR FIBERS

Cylindrical shell

Higher-order

SHEAR FLEXIBLE ELEMENTS

Spherical shell

Variable stiffness

Laminated composites

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It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Composite Structures

Investigation of thermo-elastic buckling of variable stiffness laminated composite shells using finite element approach based on higher-order theory

Materials Today Communications

Thermal buckling behaviour of variable stiffness laminated composite plates

In this paper, we study the free vibration characteristics of curvilinear fibre composite laminates exposed to hygrothermal environment. The formulation is based on the transverse shear deformation theory and it accounts for the lamina material properties at elevated moisture concentrations and thermal gradients. A 4-noded shear flexible quadrilateral plate element based on extended finite element approach is employed for the spatial discretization. The effect of a centrally located cut-out, modelled within the framework of the extended finite element method, is also studied. A detailed parametric investigation by varying the curvilinear fibre angles at the centre and at the edge of the laminate, the plate geometry, the geometry of the cut-out, the moisture concentration, the thermal gradient and the boundary conditions on the vibration characteristics is numerically studied and it is hoped that this detailed study will help the designers in optimizing such structures under dynamic situation. © 2015 Elsevier Ltd.

Composites Part B: Engineering

Environmental effects on the free vibration of curvilinear fibre composite laminates with cutouts

In this paper, we study the buckling characteristics of curvilinear fibre composite laminates exposed to hygrothermal environment. The formulation is based on the transverse shear deformation theory and it accounts for the lamina material properties at elevated moisture concentrations and thermal gradients. A 4-noded enriched shear flexible quadrilateral plate element is employed for the spatial discretization. The effect of a centrally located cut-out, modelled within the framework of the extended finite element method, is also studied. A detailed parametric investigation by varying the curvilinear fibre angles at the centre and at the edge of the laminate, the plate geometry, the geometry of the cut-out, the moisture concentration, the thermal gradient and the boundary conditions on the buckling characteristics is numerically studied. © 2015 Elsevier Ltd.

Mechanical buckling of curvilinear fibre composite laminate with material discontinuities and environmental effects

This paper presents a layup optimisation algorithm for composite marine propellers, including the hygrothermal effects, using Non-Uniform Rational B-Splines (NURBS) based FEM coupled with real-coded Genetic Algorithm (GA). The use of Iso-Geometric Analysis (IGA) enables accurate representation of complex marine propeller blades, coupled with GA for both continuous and mixed integer ply angle optimisation. The optimisation scheme was further investigated multi-objective, multi-material and multiple layer thickness optimisation scenarios. Furthermore, the IGA-FEM solver was constructed based on constitutive equations that take into account the hygrothermal effects that must be addressed to enable the optimisation of non-symmetric layups. Such non-symmetric layup patterns are proposed to be used to create extension-twist coupling to gain further control in layup optimisation. The optimisation technique is presented here as a method to widen the efficiency envelope of marine propellers. However, the same approach can potentially be adopted to cater many other practical applications such as composite wind turbine blades, aircraft propellers and other general composite ply angle optimisation scenarios. The paper discusses the proposed framework for optimisation of marine propeller, numerical tools used in the process and results under different conditions. © 2014 Elsevier B.V.

Computer Methods in Applied Mechanics and Engineering

Isogeometric analysis and genetic algorithm for shape-adaptive composite marine propellers

In this paper, the performance of different structural models based on global approach in evaluating the static response of curvilinear fibre composite laminates is analyzed. A Co shear flexible Quad-8 element developed based on higher-order structural theory is employed for the present study. The structural theory accounting for the realistic variation of displacements through the thickness and the possible discontinuity in the slope at the interface is considered. Four alternate discrete structural models, deduced from the generic structural model by retaining various terms in the displacement functions are examined for their applicability. The accuracy of the present formulation is demonstrated considering the problems for which analytical solutions are available. A systematic numerical study, assuming different ply-angle and lay-up, is conducted in bringing out the influence of various structural models on the static response of composite laminates with curvilinear fibres. © 2014 Elsevier Ltd.

Fulltext

Assessment of certain higher-order structural models based on global approach for bending analysis of curvilinear composite laminates

Isogeometric analysis of large-deformation thin shells using RHT-splines for multiple-patch coupling

Variable stiffness laminated composite shells – Free vibration characteristics based on higher-order structural theory

Journal	Data powered by TypesetComposite Structures
Publisher	Data powered by TypesetElsevier Ltd
ISSN	02638223
Open Access	No