21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-4.4.2

EXPERIMENTAL BEHAVIOR OF GRAPHITE / EPOXY PANELS WITH CUT-OUTS UNDER BIAXIAL TENSION, COMPRESSION AND SHEAR LOADS

Romeo G., Frulla G.
Turin Polytechnical University, Italy

Keywords: graphite / epoxy panels, cut-outs, biaxial tension, compression and shear loads

The behavior of graphite/epoxy panels with rectangular cutouts subjected to uniaxial and combined biaxial tension and shear loadings has been investigated. The testing machine, already manufactured for biaxial compression and shear loads, has been in fact modified making possible to apply, also in the longitudinal direction, a tension load up to 400 kN. The strain distribution has been recorded in several points· of a composite panel, due to the presence of the rectangular cutout, in order to emphasize the effect of stress concentrations. The strain. Distribution around an oval cutout, very close to the rectangular opening, of an infinite anisotropic plate has been derived by the lekhnitskii's theory obtaining a good agreement, in several cases, with the experimental results. Under uniaxial load, a very high strain concentration has been measured in the transverse direction along the cutout end; the introduction of the transverse and shear load, greatly reduce the longitudinal and transverse strain level along both sides and ends of the cutout; indeed, a very high strain level has been recorded in the cutout corner, at 45 degree of direction, when the three loads are applied simultaneously. A FEM analysis has also been carried out for the uniaxial test, obtaining a good agreement with the experimental results.

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