Mechanism of Coupling Twist Angle and Projectile Radius on Ballistic Impact Performance of Bilayer Phosphorene Membranes.

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.