Buckling optimization of composite cylinders for axial compression: A design methodology considering a variable-axial fiber layout

Abstract Fiber steering is an outstanding capability for producing composite structures with spatially tailored properties. The ability of tailoring the reinforcement arbitrarily in the space generates laminate with variable-stiffness, possessing substantial scope for outperforming traditional constant-stiffness laminates. This investigation presents a methodology to optimize composite cylinders with a variable-axial (also known as variable angle-tow and variable-stiffness) layout under axial compression for the adopted design space, loads and boundary conditions, using a novel optimization concept based on the manufacturing characteristics of the Tailored Fiber Placement (TFP) process. Next, a post-buckling analysis is carried out in order to make a first assessment of the imperfection sensitivity of the cylinders. The current approach locally optimizes both thickness and fiber angle of each finite element (FE), where thickness accumulation is reached through a smooth overlapping of rovings, a typical characteristic of TFP process. The optimized cylinders have significantly higher linear buckling loads than the corresponding initial layouts and are less sensitive to affine initial geometrical imperfections. The current work on optimization of the linear buckling behavior of variable-axial (VA) shells shows both the potential of using VA-configurations to exploit their tailoring ability and the capabilities of the current optimization framework to improve and optimize the behavior of VA structures.