Dynamic characteristics of ship composite shaft with early-stage damage based on the CUF theory and experiment

This study investigates the dynamic characteristics of ship composite shaft with early-stage damage based on the Carrera Unified Formulation (CUF) theory, improved Camanho failure criterion and strain post-processing scheme. An analysis is conducted to examine the influence of damage type, location and size on the shaft natural frequency and strain distribution. The results show that: composite shaft natural frequency reduces slightly when early-stage damage occurs, making it insufficient as sensitive indicator for shaft early-stage damage identification. In contrast, in-plane strain demonstrates greater sensitivity to damage, particularly in cases of fiber fracture and matrix cracking. And when the damage occurs closer to the shaft modal peak position, the strain comes more pronounced. These findings are significant for composite shaft health monitoring.