Influence of Stacking Sequence on the Structural Performance and Failure Behaviour of Pultruded Glass Fibre-Reinforced Polymer Composites

Glass fibre-reinforced polymer composites have emerged as promising alternatives to traditional materials for transmission tower cross-arm structures, thanks to their high strength-to-weight ratio and corrosion resistance. However, their structural efficiency is strongly influenced by stacking sequence, which governs fibre orientation, stress distribution, and failure mechanisms. This study investigates the effect of stacking sequence on the tensile behaviour and energy absorption capacity of pultruded glass fibre-reinforced polymer (pGFRP) composites. Five laminate configurations (S3, S5, S7, S9, and S10) with varied orientations and layer counts were fabricated and tested under uniaxial tensile loading. Mechanical parameters, including density, fibre volume fraction (FVF), tensile strength, Young’s modulus, energy absorption, and failure properties, were evaluated. Results revealed a strong dependence on stacking sequence, such as the S9 configuration, with a balanced and symmetric sequence (0°/45°/0°/−45°/0°/−45°/0°/45°/0°), which achieved the highest tensile strength (551.94 MPa), maximum load (91,395 N), extension (9.05 mm), modulus (49.44 GPa), and energy absorption (458.71 J). Conversely, the S10 laminate, despite the highest FVF (68.16%), showed inferior strength (297.22 MPa) due to suboptimal fibre alignment that promoted stress concentration and inefficient load transfer. Density trends were nonlinear, with S9 (2.29 g/cm3) outperforming S10 (1.65 g/cm3), indicating better compaction and resin infiltration. Normalised analysis confirmed S9 laminate exhibits a superior strength-to-weight ratio. The findings demonstrate that an optimised stacking sequence is critical for enhancing tensile performance and durability of pGFRP composites, providing valuable guidance for the structural design of transmission tower cross-arms. Future work should explore fatigue resistance and environmental durability under long-term service conditions.