This paper discusses the fact that the cured shape of thin unsymmetric laminates do not conform to the predictions of classical lamination theory. Rather than being saddle shaped, as predicted by the classical theory, the paper shows that thin unsymmetric laminates cure into a shape of a right circular cylinder. This anomalous behavior has been observed by many but the paper serves to quantify the effect and to inspire investigators to begin thinking about using the phenomenon to advantage. The paper indicates that the anomalous behavior is repeatable and that thicker laminates con form to the predictions of the classical theory. Laminates of the [0/902 /θ ]T, [02 /θ2 ] T and [04 /θ4 ] T families are investigated for this be havior and it is shown the principal curvature directions of the cylindrical shapes are predictable.

Some Observations on the Cured Shape of Thin Unsymmetric Laminates

A new trigonometric shear deformation theory for isotropic, laminated composite and sandwich plates

A summary of the recent developments in the analysis of laminated beams and plates with an emphasis on vibrations and wave propagations in presented. First, a review of the recent studies on the free-vibration analysis of symmetrically laminated plates is given. These studies have been conducted for various geometric shapes and edge conditions. Both analytical (closed-form, Galerkin, Rayleigh-Ritz) and numerical methods have been used. Because of the importance of unsymmetrically laminated structural components in many applications, a detailed review of the various developments in the analysis of unsymmetrical ly laminated beams and plates also is given. A survey of the nonlinear vibrations of the perfect and geometrically laminated plates is presented next. It is seen that due to the bending-stretching coupling, the nonlinear behavior of the unsymmetrically laminated perfect and imperfect plates, depending upon the boundary conditions, may be hardening or softening type. Similar behavior also is observed for imperfect isotropic and laminated plates. Lastly, the developments in studying the wave propagation in laminated materials are reviewed. It is seen that a significant effort has been spent on developing appropriate continuum theories for modeling the composite materials. Some recent studies on the linear and nonlinear transient response of laminated materials also are described.

Recent Advances in Analysis of Laminated Beams and Plates, Part II: Vibrations and Wave Propagation

A new shear deformation theory for sandwich and composite plates is developed. The proposed displacement field, which is “m” parameter dependent, is assessed by performing several computations of the plate governing equations. Therefore, the present theory, which gives accurate results, is relatively close to 3D elasticity bending solutions. The theory accounts for adequate distribution of the transverse shear strains through the plate thickness and tangential stress-free boundary conditions on the plate boundary surface, thus a shear correction factor is not required. Plate governing equations and boundary conditions are derived by employing the principle of virtual work. The Navier-type exact solutions for static bending analysis are presented for sinusoidally and uniformly distributed loads. The accuracy of the present theory is ascertained by comparing it with various available results in the literature.

A new higher order shear deformation theory for sandwich and composite laminated plates

Impact behaviour of fibre-reinforced composites Recent developments in impact damage assessment of fibre composites Modelling impact of composite structures using small specimens Impact damage - tolerant composite structural design Damage resistance and tolerance of thick laminated woven roving GFRP plates subjected to low-velocity impact Elastic impact stress analysis of composite plates and cylinders Impact behaviour and analysis of CFRP laminated plates Perforation of FRP laminates and sandwich panels subjected to missile impact High velocity impact damage to polymer matrix composites

Impact behaviour of fibre-reinforced composite materials and structures

Using a Fourier series method, a solution is obtained to the governing equations of simplysupported laminated plates in which coupling occurs between bending and in-plane extension. Results are presented for bending under transverse load, natural frequencies of flexural vibrations, and buckling under uniform biaxial compression. Coupling is shown to reduce the effective stiffness of a laminate compared to analogous homogeneous orthotropic plates.

J. M. Whitney

Papers

Analysis of a simply supported laminated anisotropic rectangular plate