Abstract
Commingling is becoming an important method for developing thermoplastic composites, which demonstrate significant advantages over thermoset composites in several applications including aerospace, marine, sporting, and automotive industries. Although the commingling technique has a very high potential to produce towpregs with a good blending of matrix and reinforcing fibers, it has been reported that these towpregs tend to de-mingle due to nonuniform stretching during textile and other preforming processes, leading to the segregation of stiffer reinforcing fibers and matrix-forming fibers, which in turn results in poor mechanical properties. Therefore, the current research focuses on the enhancement of stability and homogeneity of commingled yarns during subsequent processing. An attempt has been made to study the effect of the commingling process variables, namely air pressure and volume fraction of matrix-forming fibers on the structure and properties of Glass/Polypropylene, Glass/Polyester, and Glass/Nylon commingled yarns. In this paper, nips are classified into different categories based on their structure. The causes of occurrence and their effect on the commingled yarn properties are identified. Other parameters including nip frequency, nip length, and degree of interlacing are also studied in relation to the process parameters. The results show that commingling process parameters as well as the type of matrix-forming fibers significantly affect the structure and properties of commingled yarns.