Refined structural modeling of thick-walled closed section composite beams

Abstract

An analytical theory, based on Vlasov theory, is developed that accurately models the cross-sectional elastic properties of thick-walled composite multi-celled closed section beams. The model includes a correction to the shear strain equation to account for the nonuniform distribution of the shear strain through the wall thickness. A higher order transverse shear theory is also incorporated into the plate segment equations. The refined model is validated against three-dimensional solid finite element results. The validation studies reveal that the baseline Vlasov theory does not accurately capture the thick-walled effects (as much as a 24% error) while the results generated by refined theory closely match (less than 4% error) the finite element results. Parametric studies are conducted to determine the limits of Vlasov theory in predicting the crosssectional properties of thick-walled beams. Because of the shear strain related effects, differences in baseline Vlasov theory and the refined theory start to become noticeable (10% error) at wall thickness to depth ratios of approximately 20% and become significant (greater than 25% error) at thickness ratios of 30%. Results show that neglecting transverse shear in the plate segments has a noticeable effect (10% error) on transverse shear stiffness and lateral deflections of uniform lay-up beams of ply angle range 15°-45°, for thickness to depth ratios larger than 25%.

Nonlinear Composite Beam Theory

“…(1.2). Among the most commonly held misconceptions is that one always improves a beam theory by adding more deformation variables in the beam equations, some theories having as many as nine; see, for example, Chandra and Chopra (1992b) and Centolanza and Smith (1998). However, results obtained from a correct classical theory are frequently as good or better, as shown by Volovoi et al (2001).…”

Aeroelastic Analysis of Rotor Blades Using Three Dimensional Flexible Multibody Dynamic Analysis

“…1.3, several beam elements with different number of degrees of freedom have been developed with different levels of refinement ; Yuan, P.P. Friedmann (1995); Kim and White (1997); Centolanza and Smith (1998)]. The performance of a beam theory has been attributed to the accuracy of the computed cross section properties [Volovoi (2001)].…”