Influence of selected process parameters on changes of the fiber orientation in unidirectional reinforced thermoplastics during a hot pressing process

The research described in this paper is part of SFB 639 “Textile‐reinforced composite components for function integrating multi‐material design in complex lightweight applications.” In this study, changes in fiber orientation of unidirectional (UD) aligned glass polypropylene hybrid yarn were investigated. A new model for simulating changes in fiber orientation of unidirectional reinforced thermoplastics during a hot pressing process was developed. The material observed during this study is a hybrid yarn made out of homogenous aligned glass and polypropylene filaments. The mechanistic model, which was used to simulate the fiber behavior, allows the user to define different input data, such as velocity, vorticity, and viscosity of the molten polymer as well as fiber radius, initial fiber positions and fiber stiffness to characterize material properties. To determine fiber orientations, a program was written in MATLAB. Hence, it is possible to calculate the angle of any desired segment at any point of time during the hot pressing process. Thereby, it was feasible to compare the numerical obtained changes in fiber orientation with those measured during the experiments conducted at the end of the research. The post‐processing algorithm was used to determine the effects of selected processing parameters and model parameters on the fiber behavior respectively. POLYM. COMPOS., 39:2241–2249, 2018. © 2016 Society of Plastics Engineers