Hamed Akhavan

A review on the mechanical behaviour of curvilinear fibre composite laminated panels

A review on works that investigate the mechanical behaviour of variable stiffness composite laminated panels is carried out in this paper. The review mostly focuses on buckling, failure and vibrations in laminates reinforced by curvilinear fibres, although other issues related to variable stiffness laminates are also addressed. The peculiarities in the formulation of curvilinear fibre reinforced plates are briefly described. As an illustration, the natural frequencies of vibration of variable stiffness composite laminated plates with curvilinear fibres are computed by an h-version type finite element code and are compared with the ones calculated using another model, based on a Third-order Shear Deformation Theory. Areas of research to explore on variable stiffness composite laminates are suggested.

Composite laminates with linearly varying fiber angles under static and dynamic loads

In this paper, natural frequencies, large deflections and failure safety factors of variable stiffness composite laminate (VSCL) plates with curvilinear fibers are studied. In each ply of these rectangular VSCLs, the fiber-orientation angle changes linearly with respect to the horizontal coordinate. To carry out the static and dynamic analysis of the laminates, a new p-version finite element, which follows third-order shear deformation theory, is employed. Large deflections are considered, hence, the analysis is in the non-linear regime. To predict the failure onset, Tsai-Wu criterion is used. Taking into account manufacturing restrictions regarding the fiber curvatures, natural frequencies, deflections, and failure safety factors of some VSCL plates are determined. These results are compared with natural frequencies, deflections, and failure safety factors of constant stiffness composite laminate (CSCL) plates.

FLUTTER ANALYSIS OF COMPOSITE LAMINATES WITH CURVILINEAR FIBRES

Abstract. In this investigation, the authors intend to study the dynamic instability (flutter) of variable stiffness composite laminates (VSCLs) in the presence of supersonic flow. In the type of VSCL considered here, plies have curvilinear fibres and, consequently, the stiffness is variable in a macroscopic view. The plates considered are rectangular. In each ply, a reference fibre path, represented by a function of horizontal coordinate x, is defined. The reference fibre path orientation changes linearly from T0 at the centre to T1 at both vertical edges of the ply; the other fibre paths are defined shifting the reference path in direction y. The displacement and rotations are defined using a Third-order Shear Deformation Theory, and then they are discretised by a p-version finite element model that applies to VSCL plates. Piston theory is employed to model the aerodynamic force of the upstream flow in direction x. Flutter airspeeds are investigated for VSCL plates with different fibre angles. Changes of flutter speed are evaluated in two different regimes of steady and unsteady flow.