Nonclassical Behavior of Thin-Walled Composite Beams with Closed Cross Sections

摘要

This paper focuses on two nonclassical effects in the behavior of thin-walledcomposite beams: elastic bending-shear coupling and restrained torsional warping. These nonclassical effects are clarified and analyzed in some simple examples involving cantilevered beams. First, elastic bending-transverse shear coupling is shown to be important in the analysis of beams designed for extension-twist coupling. It is found that the lateral deflections can be off by more than a factor of two if this coupling is ignored. This coupling stems from plies with off-axis fibers in the beam. The presence of these plies affects significantly the modeling approach (i.e., determination of the constitutive equations) in that transverse shear must appear in the kinematics so that its coupling with bending will be exhibited in the elastic constants. This finding is in accord with 'exact' beam theories which develop the beam displacement and cross sectional orientation in terms of six kinematical variables instead of the three or four found in some previously published works on composite blade modeling. (JES)