Investigation of the Effect of CNTs on the Mechanical Properties of Biaxial Weft-knitted Thermoplastic Composites

Within the scope of experiments, three kinds of biaxial weft-knitted (BWK) fabrics with various loop lengths (8.0, 9.2 and 10.5 mm) and multi walled carbon nanotubes (MWCNTs) (0 and 1.7 wt%) were used as reinforcement systems to fabricate MWCNTs integrated thermoplastic composites with polypropylene (PP) resin yarn/glass fiber (GF). The mechanical properties of the composites were investigated by conducting the three-point bending and Charpy impact tests on the specimens. The specimens with the 10.5 mm loop length and 1.7-wt% MWCNTs showed the highest values of flexural strength properties with an improvement of about 15 % in the flexural strength compared to the specimens with the 10.5 mm loop length and without MWCNTs in 0 degrees direction. The specimens with the 8.0 mm loop length and 1.7-wt% MWCNTs showed the highest values of the Charpy impact energy properties with an improvement of about 23 % in Charpy impact energy compared to the specimens with the 8.0 mm loop length and without MWCNTs in 90 degrees direction. The improvement in the bending and impact properties of the composites can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbon nanotubes.