An evaluation of three different techniques for melt impregnation of glass fiber bundles with polyamide 12

In this research, three different techniques for melt impregnation of glass fiber bundles with polyamide 12 are assessed with the aim of creating a high strength and modulus material suitable for extrusion based additive manufacturing. Impregnation quality of three production techniques: “Pultrusion”, “PassivePin”, and “ActivePin” were analyzed using three methods: matrix material mass fraction ( M m ) determination, scanning electron microscopy of composite fracture surfaces and optical microscopy of polished composite cross sections. Pultrusion material has an overall poor impregnation degree ( D i ) and fiber distribution and dispersion, the specimens lack mechanical strength and show fiber pull‐out due to the excessive voids in the matrix. The PassivePin material has a significantly higher D i and a better fiber distribution, which results in less voids in the matrix and limited fiber pull‐out. Finally, the ActivePin material scores significantly higher in D i and shows an excellent fiber distribution. As a consequence, very limited voids are observed and an even fracture surface without fiber pull‐out is obtained. It is concluded that the ActivePin technique would be a great choice for application in an extrusion‐based AM process, this method could allow for production of high strength and stiffness objects. POLYM. ENG. SCI., 58:601–608, 2018. © 2017 Society of Plastics Engineers