a b s t r a c tThis paper studies a three-dimensional buckling delamination problem for a rectangular plate made from elastic and viscoelastic composite material. It is assumed that the plate contains a rectangular band-crack (Case 1) and a rectangular edge-crack (Case 2) and that the edge-surfaces of these cracks have an initial infinitesimal imperfection. The evolution of this initial imperfection with an external compressive loading, acting along the crack (for an elastic composite) or with duration of time (for a viscoelastic composite under fixed external loading) is investigated within the framework of three-dimensional geometrically non-linear field equations of the theory of the viscoelasticity for anisotropic bodies. To determine the values of the critical force or critical time as well as the buckling delamination mode, the initial imperfection criterion is used. The corresponding boundary-value problems are solved by employing boundary form perturbation techniques, Laplace transform and FEM (Finite Element Method). The influence of the materials and/or the geometrical parameters of the plate on the critical values are discussed. In particular, it is established that for the considered change range of the problem parameters, the buckling form depends only on the initial infinitesimal imperfection mode of the crack edges.

No abstract

No abstract

The present study investigates the non-linear behavior of spherical shells under the influence of static circular ring loads. It is assumed that the material is isotropic and linearly elastic. The differential equations comprising the equilibrium equations, constitutive laws and kinematic equations are converted into non-linear algebraic equations by employing the method of finite differences. Respective non-linear algebraic equations are solved numerically by using the Newton–Raphson Method. The curves pertaining to the circular ring load versus the deflection at the application point of the ring load and the circular ring load versus the deflection at the apical point of the shell are plotted and compared for various shell radius/thickness ratios and parallel circle radii values.

Snap-through buckling behaviour of rigid vinly polyethlene shallow spherical shells, undergoing large displacements, subjected to static ring loads is investigated by using finite differences and Newton-Raphson Method. The load-deflection diagrams corresponding to various values of thickness, depth and ring diameter of the shell with simply supported and clamped edges are drawn and compared. The accuracy of the used algorithm and the prepared computer program are tested by comparing some of the numerical results obtained in this study with those obtained by an experimental study, available in the relevant literature. Further steps on the concerning subject are achieved.