Pre-twisted carbon fibers reinforced polymer composites and the unique clockwise and counterclockwise torsion behaviors

Twisting can enhance the interaction forces between fibers in bundles, improving the mechanical properties of fiber-reinforced composites. This study employs the thermosetting method to fabricate pre-twisted carbon fiberreinforced polymer (CFRP) composites. The effects of twist on resin impregnation were qualitatively and quantitatively investigated by measuring the contact angle and analyzing thermogravimetric data. The torsional strength and modulus of CFRP were measured using a customized torsion testing apparatus to study its torsional behavior. Additionally, finite element analysis was conducted to examine the mechanical characteristics of varying twist levels (0-300 T/m) under the combined effects of tension and torsion, elucidating the reinforcement mechanism of twisting in fiber-reinforced composites. The results indicate that pre-twisted CFRP exhibits distinctly different behavioral characteristics during anti- and clockwise torsion. The composite with 100 T/m twist exhibits the highest clockwise torsional strength (1608 MPa), which is twice that of untwisted CFRP; The 300 T/m CFRP achieves an anticlockwise torsional angle of 18,000 degrees (three times that of untwisted CFRP) and exhibits unique stability over a broad range. The experimental results and theoretical models presented in this study offer valuable guidance for enhancing the mechanical properties of twisted carbon fiber composites under torsional loading conditions.