Following the effect of braid architecture on performance and damage of carbon fibre/epoxy composite tubes during torsional straining
Yuan Chai, Ying Wang, Zeshan Yousaf, Malte Storm, Nghia T. Vo, Kaz Wanelik, Timothy L. Burnett, Prasad Potluri, Philip J. Withers
Abstract
The torsional performance of bi-axially braided carbon fibre reinforced polymer (CFRP) tubes as a function of braid architecture is investigated. It is found that for a given braid pattern, the 45° braided CFRP tubes have higher shear moduli and lower shear strength than the 35° braids. In general, 2/2 (regular) braided CFRP tubes exhibit both higher shear strength and higher shear modulus than 1/1 (diamond) braids. However, beyond the peak load, the shear strength of 2/2 braided CFRPs exhibits sudden and steep drops, resulting in a lower remnant shear strength than 1/1 structures after the shear strain exceeds 4.5%. Moreover, the damage evolution is monitored in-situ by synchrotron X-ray computed tomography during torsional straining. It shows that for a 2/2 structure, inter-tow debonded regions are vertically interconnected allowing rapid crack propagation and strength drops, whereas for the 1/1 braid they are distributed in a chequer board pattern causing a more gradual loss of strength. The fibre/matrix interfacial strength and tow cross-over density play key roles in the torsional failure of 1/1 and 2/2 braided CFRP tubes, as the former controls damage initiation and the latter controls damage propagation.