Experimental and predictive analysis of the molding behavior of a PA6 glass mat thermoplastic (GMT)

The material targeted in this study is TEPEX® flowcore, a long glass fiber mat reinforced polyamide (PA6/GF) manufactured by Lanxess. The material is classified experimentally on coupon level, and the kinetic behavior is analyzed through standard and flash DSC analyses. Subsequently, results from experimental molding trials are investigated concerning material forming and material flow. Finally, molding behavior is analyzed on a predictive basis using a thermokinetic and a rheological model. It is found that molding of the PA6 GMT comprises the sequential stages of material forming and material forming, in combination with the respective defects wrinkling and incomplete mold filling. Flowability is found to be rather limited, given the usually adopted thin stacking heights (≲8mm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lesssim 8 \, \text {mm}$$\end{document}), a minimum achievable part thickness (>3mm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$> 3 \, \text {mm}$$\end{document}), and a maximum specific pressure (<500bar\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$< 500 \, \text {bar}$$\end{document}). Finally, it is shown that the experimentally observed no wall slip results from an instant solidification of the sheet surface due to the significant difference in mold wall and charge temperature.