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The delamination buckling problem for a rectangular plate made of an orthotropic composite material is studied. The plate contains a band crack whose faces have an initial infinitesimal imperfection. The subsequent development of this imperfection due to an external compressive load acting along the crack is studied through the use of the three-dimensional geometrically nonlinear field equations of elasticity theory for anisotropic bodies. A criterion of initial imperfection is used in determining the critical forces. The corresponding boundary-value problems are solved by employing the boundary-form perturbation technique and the FEM. Numerical results for the critical force are presented. [ABSTRACT FROM AUTHOR]

The postimpact buck ling loads of E-glass/epoxy laminates have been measured. Composite samples with the stacking sequence [+45/−45/90/0]2s were subjected to low-speed impact loadings at various energy levels. The tests were conducted on a specially developed vertical drop-weight testing machine. The main impact parameters, such as the peak load, absorbed energy, deflection at the peak load, and damage area, were evaluated and com pared. The damaged specimens were subjected to compressive axial forces, and their buckling loads were determined. The relation between the level of impact energy and buck ling loads is investigated. [ABSTRACT FROM AUTHOR]

Two new hyperbolic displacement models, HPSDT1 and HPSDT2, are used for the buckling and free vibration analyses of simply supported orthotropic laminated composite plates. The models contain hyperbolic expressions to account for the parabolic distributions of transverse shear stresses and to satisfy the zero shear-stress conditions at the top and bottom surfaces of the plates. The equation of motion for thick laminated rectangular plates subjected to in-plane loads is deduced through the use of Hamilton’s principle. Closed-form solutions are obtained by using the Navier technique, and then the buckling loads and the fundamental frequencies are found by solving eigenvalue problems. The accuracy of the models presented is demonstrated by comparing the results obtained with solutions of other higher-order models given in the literature. It is found that the theories proposed can predict the fundamental frequencies and buckling loads of cross-ply laminated composite plates rather accurately. [ABSTRACT FROM AUTHOR]

Buckling around an interfacial crack in a clamped sandwich plate is studied. The layers of the plate are assumed to be linearly viscoelastic, isotropic, and homogeneous. The investigations are carried out within the framework of a piecewise homogeneous body model with the use of a three-dimensional linearized theory of stability. The corresponding boundary value problems are solved numerically by employing the FEM and the Laplace transform. The calculated critical times are presented for various problem parameters. In this case, the upper and lower layers are assumed to be viscoelastic and are described by Rabotnov operators, whereas the midlayer is regarded as purely elastic. The influence of rheological parameters on the critical time is also analyzed. [ABSTRACT FROM AUTHOR]