Postbuckling analysis of variable angle tow composite plates

Variable angle tow (VAT) placement techniques provide the designer with the ability to tailor the point-wise stiffness properties of composite laminates according to structural design requirements. Whilst VAT laminates exhibiting substantial gains in buckling performance have been shown previously, beneficial ways of using VAT techniques to improve structural performance of composite laminates in the postbuckling regime remain unclear. In the present study, a semi-analytical formulation based on a variational approach is developed and the Rayleigh–Ritz method is subsequently applied to solve the postbuckling problem of VAT plates. The generality of the proposed formulation allows effective modelling of the pure or mixed stress boundary conditions and also provides a computationally efficient means to determine the postbuckling strength of VAT plates. The proposed methodology is applied to the postbuckling problem of simply supported VAT plates under uniform edge displacement compression. To show the accuracy and robustness of the proposed approach, results are validated using finite element analysis. The postbuckling characteristics of VAT plates subject to different in-plane boundary conditions are analysed by studying their nonlinear load-end shortening and transverse deflection responses. Furthermore, a parametric study on the postbuckling response of VAT plates with linear variation of fibre angle is performed and the stiffness values of VAT plates in both pre- and postbuckling ranges are compared with the results of straight-fibre laminates.