Analytical theory for an approach calculation of non-balanced composite box beams

For aeroelastic problems, optimization of the behavior of box beams, carrie d out in composite materials, can lead to the construction of structures wh ose longitudinal axis is not necessarily the orthotropic axis of the materi als. These beams present couplings such as Flexion-Torsion or Traction-Tors ion. In this study, we propose an analytical theory which allows these stru ctures to be dimensioned with extreme accuracy and without using complicate d calculations. The method developed, based on a weak hypothesis on the fie ld of deformations, makes it possible to obtain from simple analytical calc ulations, the stresses and displacement in a cross-section for normal load (F) over right arrow (x), flexion moments (M) over right arrow (y), M-z and torsion moments (M) over right arrow (x). it is then possible using the la minated plates theory, to determine the stresses in each layer. The results obtained correspond perfectly to those found in a 3D Finite Element model, calculated using CATIA-ELFINI software. On the central part of the beams, the relative differences noticed between these two methods on the calculati on of stress, strain and rigidities are negligible. Near the embedded secti on, warping is very important and the relative error is great. (C) 2001 Els evier Science Ltd. All rights reserved.