Damping Optimization Design of Plant Fiber-Reinforced Composites for Subway Interior Structures

The optimization of material design for subway interior structure is crucial for noise reduction and sustainability. Plant fiber-reinforced composites (PFRCs) used as interior structures offer both adequate load-bearing capacity and vibration reduction. In this study, a hybrid fiber technique was employed, integrating the Hashin failure criterion and complex eigenvalue method to investigate bending and damping performances of five distinct carbon/flax fiber-reinforced epoxy composite (CFFRC) stacking sequences (C80, C20F20C20, F15C20F15, F10C10F10C10F10, and F40) of an interior structure. The CFFRCs were fabricated via a hot press platen process with a consistent 60% overall fiber volume fraction. The experimental modal behaviors (damping ratios, frequencies, and mode shapes) were clarified by vibration tests using a non-contacting 3D Scanning Laser Doppler Vibrometer. The results revealed that hybrid composites can effectively balance the mechanical and damping properties. Hybrid composites with the flax fiber positioned in the outermost layer demonstrated superior damping performances. The optimal hybrid composite (F10C10F10C10F10) achieved a first-order modal damping ratio of 0.75% (numerically), which is significantly higher than the 0.30% observed for pure carbon fiber composites (C80). The numerical model’s validity was confirmed by a strong correlation with experimental results. It provides valuable parameters for designing safe and reliable subway interior structures, integrating load-bearing and damping capabilities.