Prediction of impact response of delaminated pretwisted stiffened shell

ABSTRACT

The dynamic response of delaminated twisted stiffened cylindrical shell under low-velocity impact of multiple masses is presented. The impactors are considered to impact at two arbitrary locations simultaneously or at different time, wherein the contact forces of the impactor are computed by using the modified Hertzian contact law. Multipoint constraint algorithm is used to create rectangular inter-ply delamination. An eight-noded isoparametric shell element is combined with a three-noded isoparametric beam element to model the stiffened panel. The governing equations are derived from Lagrange’s equation of motion and solved by Newmark’s constant acceleration algorithm to perform the parametric study.

KEYWORDS:

• Stiffener
• delamination
• multiple impacts
• cylindrical shell
• Hertz contact

Nomenclature

$L,b$	=	Length and width of cylindrical shell, respectively
$h$	=	Thickness of shell
$\mathrm{\Phi }$	=	Twist angle of the shell
$d$	=	Distance of centre of delamination from fixed end
$a$	=	Length of delamination
$h^{\prime }$	=	Distance of delamination across the thickness from top ply
$\rho$	=	Mass density of the shell and stiffener
$b_{st},d_{st}$	=	Width and depth of stiffener, respectively
$n_x,n_y$	=	Number of stiffeners in x- and y- direction, respectively
vi	=	Initial velocity of impactor
nl	=	Number of layers in the laminate

Disclosure statement

No potential conflict of interest was reported by the authors.