Sustainable bamboo–nettle hybrid polymer composites: advances in fiber modification, fabrication, and property optimization

Natural-fiber-reinforced polymer composites are gaining traction as sustainable alternatives to glass- and carbon-fiber systems, yet bamboo and nettle two agriculturally advantageous, mechanically promising fibers, remain comparatively underexplored as a hybrid reinforcement pair. This review consolidates recent advances in bamboo–nettle hybrid polymer composites, synthesizing evidence on raw fiber properties, polymer matrix compatibility, interfacial surface modification, fabrication technologies, hybridization architectures, and resulting structure–property relationships. Hybridization is reported to yield tensile, flexural, and impact improvements in the general range of 20–40% over single-fiber laminates through synergistic stress transfer, although this range is drawn predominantly from bamboo-glass, flax-glass, and other analogous natural–natural and natural–synthetic hybrid systems rather than from bamboo–nettle laminates specifically, while alkali and other chemical/physical surface treatments improve fiber–matrix adhesion and reduce moisture-related degradation. Vacuum-assisted fabrication routes outperform conventional hand lay-up by minimizing voids and improving resin distribution, and comparative benchmarking of bamboo and nettle against established bast fibers suggests these systems could approach the mechanical performance of glass-fiber-reinforced polymer at lower density. Despite this progress, challenges persist in property variability, standardization, long-term environmental durability, and scalable manufacturing. Future work should prioritize bio-based matrix development, advanced surface engineering, automated fabrication, and computational/machine-learning-assisted design to enable structure–property optimization.