Desenvolvimento de Multifilamentos de Nanotubos de Carbono e Avaliação de seu Comportamento em Condições de Fluência e Fadiga

Abstract

Carbon nanotubes (CNT) are structures that present extraordinary mechanical properties, representing a discovery with great potential in the most diverse fields. One of the macrostructures formed by CNTs are yarns, which have been highly studied in recent decades, and can be applied as sensors, actuators, artificial muscles, among others. CNT yarns were manufactured from highly aligned forests, by forest spinning method, with five layers of CNTs film. Preliminary tensile tests and the morphological characteristics observations of the yarns were carried out to determine the ideal number of torsions. Specimens were manufactured with 2000 torsions per meter and had their tensile strength and morphological characteristics analyzed, as well as industrial produced CNT yarns. Scanning microscopy images showed that the yarns maintained their torsion after tensile tests. The manufactured yarns presented 317 ± 56 MPa of breaking strength, while the industrial ones presented 850 ± 71 MPa. Then, the industrial yarn was creep tested at one load level (70%) and the manufactured yarns, made with multiple layers, were tested with three different loads, based on the percentage of the Yarn Breaking Load (YBL) obtained in the tensile tests: 50%, 70% and 80% of the YBL. The industrial yarn had a creep life of 0.1 hour, while the manufactured yarn resisted for 254 hours. At lower loads, the multilayer yarns appear to have three creep cycles, appearing partial breakage followed by yarn regeneration. The yarns were also tested on fatigue, after defining the test parameters empirically. The yarns were tested in tension-tension fatigue. The industrial yarn was tested between 20 and 80% of the YBL and the multilayer yarn between 20 and 70% of the YBL. industrial yarn resisted for 27999 cycles and multilayer yarn had its test interrupted at 106 cycles. After the fatigue cycling, the multilayer yarn was taken to rupture, presenting a breaking strength higher than that presented in the test before the fatigue cycles.