Analytical and experimental behaviour of laminated panels with rectangular opening under biaxial tension, compression and shear loads

The strain distribution around a rectangular opening of an infinite anisotropic plate has been derived by using Lekhnitskii's theory and using the complex variable method. The testing machine was implemented in order to simultaneously apply uni and biaxial tension or compression combined with shear loading. The strain distribution was recorded in several points of a composite panel, with the presence of the rectangular cutout, in order to emphasize the effect of stress concentrations. A good agreement has been obtained between the analytical and the experimental results; several original results are reported in the paper for laminated panels under combined biaxial and shear loading. Under uniaxial load, a very high strain concentration was measured in the transverse direction along the cutout end; the introduction of the transverse and shear load greatly reduced the longitudinal and transverse strain levels along both the sides and ends of the cutout; a very high strain level was recorded in the cutout corner when the three loads were applied simultaneously. A FEM analysis was carried out, obtaining a good agreement with the experimental results also as far as the buckling behaviour is concerned. The buckling load was not affected very much by the presence of the opening, except when shear load was applied.