Abstract
This study investigated the coupling mechanism between interlayer twist angle and projectile size on the ballistic performance of bilayer phosphorene membranes, a topic essential for designing efficient nano-protective materials, yet still poorly understood. Using coarse-grained molecular dynamic simulations, we systematically explored how twist angles (0-90°) and projectile radii (2-10 nm) jointly influence impact response for membranes with a radius equal to 48 nm. We found that the effect of twist angle becomes significant only beyond a critical projectile size (~8 nm). Below this threshold, deformation remains local and twist-independent. However, for larger projectiles, the twist angle drastically alters wave propagation and failure modes. Specifically, a 90° twist induces severe wave reflection and interference, leading to a dramatic force amplification (up to 82%) and a 28% reduction in ballistic limit velocity, making it the most susceptible configuration. These results underline the critical role of twist-boundary-wave interaction in governing impact resistance and provide practical insights for the design of phosphorene-based nano-armor systems tailored to specific impact conditions.