Thermal postbuckling behavior of 3D braided beams with initial geometric imperfection under different type temperature distributions

Thermal postbuckling analysis for 3D (three-dimension) braided beams to initial geometrical imperfection in general modes subjected to uniform, linear and non-linear temperature distribution through the thickness are presented. The cross-section of 3D braided composite beam may be treated as a cell system and the geometry of each cell is deeply dependent on its position. A generic imperfection function for one-dimensional composite beam is introduced to model various possible initial geometrical imperfection including sine type, local type, and global type imperfections. Based on first-order shear deformation beam theory incorporating von Kármán nonlinear strain displacement relations, the governing equation is nonlinear integral–differential equations. An analytical solution for thermal postbuckling of 3D braided beams with and without imperfection obtained as a function of the applied thermal load is employed to determine buckling temperatures and postbuckling equilibrium paths of 3D braided beams. The results reveal that the temperature dependent properties, temperature distribution, geometric parameter, fiber volume fraction, initial geometrical imperfections and braiding angle have a significant effect on thermal postbuckling behavior of braided composite beams.