Failure Mechanisms of Short Fiber Reinforced Composite Materials Subjected to Dynamic Loading

The mechanical behavior of short carbon fiber reinforced polylactic acid (SCF/PLA) composites fabricated by fused deposition modeling (FDM) is crucial for engineering applications, yet their strain‐rate dependence is not fully understood. This study aims to investigate the tensile response and fracture mechanisms of SCF/PLA under varying strain rates. Dog‐bone specimens were tested under quasi‐static (10 −4 s −1 ) and dynamic loading up to 50 s −1 , and fracture surfaces were analyzed via scanning electron microscopy (SEM). Results indicate clear strain‐rate sensitivity: Young's modulus increased from 2.1 to 2.4 GPa, and fracture strength followed a power‐law relationship ( σ = 38· ε̇ 0.065 ). SEM observations reveal a transition from flat fracture surfaces dominated by matrix cracking and fiber/matrix debonding at low rates to rougher surfaces with increased fiber pull‐out, fiber fracture, and matrix cracking at high rates. The number of exposed fibers increased while their pull‐out length decreased, suggesting enhanced interfacial shear strength. These findings demonstrate pronounced rate‐dependent mechanical and microstructural behavior, providing essential insights for designing FDM‐printed SCF/PLA components in dynamic applications.