in-plane shear-axial strain coupling formulation for shear-‎deformable composite thin-walled beams

This paper presents an improved description of the inplane strain coupling in librescutype sheardeformable composite thinwalled beams (ctwb). based on existing descriptions for eulertype ctwb, an analogous formulation for sheardeformable ctwb is here developed by building, via the mindlin–reissner theory and an orthotropic constitutive law of the shell wall, an alternate equation for the inplane shear force which effectively couples the axial and shear inplane strains. it is observed that this strain coupling formulation includes some of the transversal (outofplane) shear strain terms, thus also functioning as a path for transferring transversal shear energy to the inplane strain field and therefore improving sheardeformability. the performance of the new ctwb model is compared against that of previously available cwtb (i.e. eulertype with strain coupling and timoshenkotype without strain coupling) for several aspect ratios, fibreorientations and laminate types. error measures are calculated by comparing several relevant stiffness coefficients and displacement shapes to reference results provided by corresponding 3d shellbased ansys finiteelement models. results indicate that for cases involving significant shear energy (i.e. short aspect ratios) and/or inplane shearaxial strain coupling (i.e. offaxis or asymmetric/unbalanced laminates), the new ctwb model proposed in this work can attain an accuracy level comparable to that associated to more sophisticated models, two to three orders of magnitude larger, at a fraction of the computational cost.