Tee failure of carbon fibre reinforced plastic laminated plates under biaxial stresses

Abstract

A new biaxial test procedure, known as the 'plate bending method' is investigated for thin multilayered generally orthotropic laminated plate structures. The method is evaluated with reference to the four criteria for a satisfactory biaxial test. A number of experiments have been performed to determine the applicability of the criteria to the new method. Surface strains, transverse displacements and visual observations have been recorded, from which the bending behaviour and failure mechanisms in the experiments are examined. A classical 2-dimensional thin plate finite element analysis has been developed to predict the stresses generated in the small (linear) and large (non-linear) deformation domains. To minimise computing effort in the analyse of non-linear bending, the formulation omitted the effects of shear deformation, shear stresses, material non-linearities and the exact position of the neutral axis. The omission of these factors has been examined and it is shown that the individual errors are small. Analytical solutions for simple isotropic, and, where available, laminated plate bending examples, have been used to establish the limitations of the finite element analysis. Numerical results have been compared with the measured surface strains and transverse displacements. From the comparison it is shown that the plate bending method can be accurately modelled by the linear analysis. However, the non-linear analysis is shown to be inaccurate when predicting the measured bending for reasons which are discussed.