Performance of hybrid GFRP–CFRP tubes as UV-exposed structural components: influence of layer configuration

• Layer sequencing significantly affects the post-UV compressive strength of hybrid FRP tubes. • FTIR analysis revealed distinct chemical degradation patterns in different configurations. • SEM imaging confirmed higher resin degradation in GFRP layers compared to CFRP. • Alternating layer configurations offered more consistent UV resistance than 50–50 layouts. Fibre hybridisation offers a pathway to reduce the high cost of carbon fibres while improving the limited durability of glass fibres. This study provides the first systematic investigation into how layer configuration governs UV-induced degradation and residual compressive performance of filament-wound hybrid glass/carbon fibre reinforced polymer (HFRP) tubes. Four configurations were fabricated: two with 50% GFRP and 50% CFRP in inner–outer placements, and two with alternating sequences. Specimens were subjected to accelerated UV exposure for 720, 1440, and 2160 h, simulating up to 3 years in Melbourne, Australia. Residual properties were evaluated using compression tests, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Results show that alternating configurations exhibited only 15–17% strength reduction after 2160 h, while 50–50% tubes with CFRP outer layers retained about 82% of their strength compared with up to 30% loss when GFRP was exposed. Elastic modulus decreased less significantly, with maximum reductions of 12%. Two-way ANOVA confirmed that exposure duration was the dominant factor (ηp² = 0.801, large effect), while layer configuration also had a meaningful impact (ηp² = 0.582, moderate effect). SEM and FTIR analyses confirmed that CFRP layers mitigated resin oxidation and microcracking, whereas GFRP outer layers accelerated interfacial degradation. These findings highlight that UV degradation is governed not only by the exposed fibre type but also by the internal stacking sequence. Alternating configurations effectively distribute damage and reduce reliance on the outermost ply, while CFRP outer layers significantly enhance durability. This work demonstrates that tailoring layer configuration is a simple yet powerful design strategy to optimise the long-term serviceability of hybrid FRP composites in outdoor structures