A Strength of Materials Formulation for Thin Walled Composite Beams with Torsion

Abstract

A simple methodology for the analysis of thin walled composite beams subjected to bending, torque, shear, and axial forces is developed. Members with open or closed cross section are considered. The cross section is modeled as a collection of flat. arc-circular, and concentrated area segments. Each laminated segment is modeled with the constitutive equations of classical lamination theory accounting for a linear distribution of normal and shear strains through the thickness of the walls, thus allowing for greater accuracy than classical thin walled theory when the walls are moderately thick. The geometric properties used in classical beam theory such as area, first moment of area, center of gravity, etc., are no longer used because of the variability of the materials properties in the cross section. Instead, mechanical properties such as axial stiffness, mechanical first moment of area. mechanical center of gravity, etc., are defined to incorporate both the geometry and the material properties. Warping, restriction to warping, and secondary stresses are considered. Failure predictions are made with customary failure criteria. Comparison with experimental results are presented.