Sandwich Composite Shells Research Articles

Buckling of a sandwich composite cylindrical shell stiffened by rings under external pressure

A solution is presented for the problem of buckling of a sandwich composite cylindrical shell stiffened by rings and subjected to external pressure. The solution is obtained on the basis of the theory of stiffened composite shells taking into account the discrete position of the rings, the transverse shear deformation in the shell and rings, the laminated structure, and the orthotropy of the facing materials. The perturbed state of the stiffened shell is described by a semimembrane model. The prebuckling state of the structure is considered to be axisymmetric with allowance for prebuckling bending moments. It is assumed that the rings are deformed in their planes only and that the contact load between the rings and the shell is applied along the axis lying at the midsurface of the shell. The Dirac delta-function is used for the description of the distribution of contact forces acting between the shell and the rings. As an example, the critical external pressure has been obtained for a glass-epoxy structure of 5 m length, 1.25 m radius, and 0.12 m thickness stiffened by various numbers of rings.

Low velocity impact analysis of composite sandwich shells using higher-order shear deformation theories

In the present investigation, higher-order and conventional first-order shear deformation theories are used to study the impact response of composite sandwich shells. The formulation is based on Donnell’s shallow shell theory. Nine-noded Lagrangian elements are used for the finite element formulation. A modified Hertzian contact law is used to calculate the contact force. The results obtained from the present investigation are found to compare well with those existing in the open literature. The numerical results are presented to study the changes in the impact response due to the increase of core depth from zero to some specified value and the changes in core stiffness for a particular core depth.

Finite element impact response analysis of doubly curved composite sandwich shells Part-I: theoretical formulation

Abstract In the present part, higher-order and conventional first-order shear deformation theories in conjunction with nine-noded quadratic isoparametric Lagrangian elements are used to develop a finite element analysis procedure for studying the impact response of composite sandwich shells. The shell behaviour is based on the Donnell's shallow shell theory. The face thicknesses are assumed to be small compared to that of the core. For the computation of local indentation, the core beneath the impacting point is assumed to behave like an elastic foundation and is modelled employing twenty-noded isoparametric orthotropic brick elements. Numerical results are presented in the second part of the present paper.

Finite element impact response analysis of doubly curved composite sandwich shells Part-II : numerical results

Abstract In the present paper, numerical results are presented using the finite element code developed by Maiti and Sinha [1]. Numerical results depict the variation of impact response due to the change in the properties of the core and other parameters.

The postbuckling performance of sandwich and composite shells with in-plane shear nonlinearity and unsymmetric layers

We have used the natural approach to construct a curved triangular shell element NATCOP for analysis of sandwich and composite shells in previous work (see J. Zhu, Application of natural appraoch to nonliner analysis of composite and sandwich composite plates and shells, Comput. Methods Appl. Mech. Engrg. 120 (1995) 355–388). The sandwich and composite shells can be either symmetric or unsymmetric and the in-plane shear relation can be linear or nonlinear. In this paper, element NATCOP is used to analyse the postbuckling behaviors of some typical sandwich and composite plates and shells, in order to show the influence of the in-plane shear nonlinearity and unsymmetric layers on the buckling and postbuckling of the multilayered shells. The analysis results show that only slight influence has the nonlinearity of the in-plane shear on the buckling and post-buckling for the thin composite plates and shells, while for the thick and medium thick composite plates and shells with certain layup, the influence of the nonlinear in-plane shear relation is significant. The influence of asymmetry on the buckling and postbuckling of sandwich and composite shells is complicated and depends on the layup, the number of layers and the thickness.

Combined micro‐ and macromechanical considerations of layered composite shells

AbstractThis contribution deals with a computational treatment of the non‐linear behaviour of composite sandwich shells with extremely thin face layers and a relatively thick orthotropic core, and multi‐layered fiber reinforced polymer or metal matrix composite shells. Special emphasis is laid on algorithms which allow the consideration of local effects, like face layer wrinkling in sandwich shells and progressive damage or microplasticity in fibre composites, by semi‐analytical approaches implemented into a finite element formulation. This leads to the advantage that the shell structure must be discretized only up to an element mesh density which is sufficient for describing the global deformation and stability behaviour.

Stress-strain state and stability of composite sandwich shells with a scaling zone between the core and facings

A finite element model is presented for analyzing the strength and stability of sandwich shells of arbitrary configuration with an adhesion failure zone between the core and one of the facings. The model is based on the assumptions that both facings are laminated Timoshenko-type composite shells, only transverse shear stresses in the core and normal stresses in the thickness direction have nonzero values, a free slip in the tangential plane in the adhesion failure zone and unilateral contact along the normal are possible, and the prebuckling state in the stability problem is linear. Biquadratic nine-node approximations for all functions and numerical integration were used. The displacements and rotation angles of the normals toward the facings as well as stresses in the core are taken as global degrees of freedom. The algebraic problem is solved using a special step-by-step procedure of determining the contact area in the scaling zone and employing unilateral constraints for some of the unknowns. Numerical examples are also given.