Influence of preparation parameters on the torsion performance and failure mechanisms of CFRP tubes

Carbon fiber reinforced polymers (CFRPs) are promising materials for tubular structures in wind energy systems. Although their torsional behavior has been widely studied, the coupled influence of diameter and ply orientation under different loading rates remains insufficiently understood. This study addresses this gap through static and dynamic torsion experiments using a custom-designed fixture that converts impact forces into controlled torsional loading, thereby overcoming the inability of conventional setups to measure dynamic torsional responses. In dynamic tests, ply orientation produces a pronounced effect; for example, the peak force of the 25-90-40 specimen is 17.2 % higher than that of the 25-45-40 specimen due to circumferential fiber alignment, which enhances hoop constraint and rate-dependent shear stiffness. Analysis of response histories and failure modes further reveals a clear rate-dependent diameter effect: smaller-diameter tubes show better stability under low incident energy, whereas larger-diameter tubes exhibit higher dynamic torsional resistance as the incident energy increases. These findings provide new insight into the torsional behavior of CFRP tubes under multi-rate loading.