Sudip Dey

Dynamic analysis of delaminated composite conical shells under low velocity impact

The dynamic response of graphite-epoxy delaminated cross-ply composite shallow conical shells subjected to low velocity normal impact is investigated using the finite element method. An eight-noded isoparametric plate bending element is employed in the formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin’s theory. In the time integration, Newmark constant average acceleration method in conjunction with an efficient iteration scheme is used. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the time-dependent equations. Numerical results present the histories of contact force, deflection/thickness and impactor’s displacement for centrally impacted delaminated cross-ply composite cantilevered conical shells.

Effect of oblique angle on low velocity impact response of delaminated composite conical shells

This paper presents the effect of oblique impact angle on low velocity transient dynamic responses of delaminated composite pretwisted shallow conical shells. An eight-noded isoparametric quadratic plate bending element is employed in the finite element formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin’s theory. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time-dependent equations are solved by Newmark’s time integration scheme. A comparative study is carried out on torsion stiff, cross-ply, and bending stiff laminates to investigate the effects of triggering parameters like angle of twist, plate displacement, striker’s velocity, and displacement for graphite-epoxy composite laminate subjected to low velocity oblique impact at the center.

Free Vibration Characteristics of Multiple Delaminated Cross-ply Composite Conical Shells

This paper investigates the free vibration of multiple delaminated graphite-epoxy cross-ply composite pretwisted rotating conical shells. The generalized dynamic equilibrium equations are derived from Lagranges equation, neglecting the Coriolis effect for moderate rotational speeds. The formulation is based on Mindlins theory considering an eight-noded isoparametric plate-bending element. The multipoint constraint algorithm is employed and a QR iteration algorithm is utilized to solve the standard eigenvalue problem. The mode shapes for a typical laminate configuration are also depicted. Numerical results obtained are the first known value, which could serve as reference solutions for future investigators.

Finite Element Transient Dynamic Analysis of Delaminated Composite Conical Shells Subject to Low Velocity Impact

This paper investigates on the transient dynamic response of delaminated composite pretwisted shallow conical shells subjected to low velocity normal impact. Turbomachinery blades with low aspect ratio could be idealized as twisted rotating cantilever composite conical shells. To derive the dynamic equilibrium equation, Lagrange’s equation of motion is used for moderate rotational speeds neglecting the Coriolis effect. An eight noded isoparametric plate bending element is employed in the finite element formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin’s theory. To satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front a multipoint constraint algorithm is incorporated which leads to unsymmetric stiffness matrices. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark’s time integration algorithm. Parametric studies are conducted in respect of triggering parameters like location of delamination, angle of twist and velocity of impactor for the centrally impacted graphite-epoxy torsion stiff composite conical shells.Copyright