Lateral Torsional Buckling of FRP Beams; Effect of Fiber Orientation and Stacking Sequence

Abstract

This study investigates the influence of fiber orientation and stacking sequence on the lateral-torsional buckling (LTB) behavior of FRP I-beams. The assessment of LTB capacity of beams was conducted using a validated 3D numerical model that allows for varying the stacking sequence and fiber orientation. Several stacking sequences are examined by varying the angles of the fibers. Beams with unidirectional fiber laminates exhibited optimal LTB resistance when the flange fibers aligned with the longitudinal axis (0°) and the web fibers inclined at 45°. Deviations from these angles led to a substantial reduction in LTB capacity. Stacking sequences incorporating a combination of cross-ply and angle-ply layers demonstrated superior LTB performance compared to purely angle-ply configurations. The study further explores the impact of fiber orientation on the required flange thickness to achieve a specific LTB load. Results indicate that lower inclination angles in the flanges allow for thinner flange designs. These findings emphasize the importance of optimizing fiber orientation and stacking sequence during the design of FRP beams to maximize their LTB resistance and achieve efficient load-carrying capacity.