Tensile performance and failure modes of continuous carbon nanotube yarns for composite applications

Carbon nanotube (CNT) yarns have demonstrated promising mechanical properties and scalability for composite applications. In this study, a commercially available continuous CNT yarn and two modified versions at large gauge lengths (~110 mm) were tested to reveal engineering properties. The as-received yarns with a large cross-section demonstrated the highest specific tensile strength (0.911 ± 0.137 N/tex), while the highly densified yarns showed the lowest specific tensile strength (0.337 ± 0.217 N/tex). Results suggest that alignment governs the ultimate tensile strength, while defects dictate how yarns fail and the harnessed strength potential. Of the two failure modes detected, brittle edge failures experienced greater ultimate tensile strengths ranging from ~8 to 20% depending on the yarn type. The test results were fitted to 2-parameter Weibull distributions to further confirm the failure behavior. These results indicate valuable properties for industrial CNT yarn applications and provide a baseline for large gauge length CNT studies.