This paper addresses the finite element-based modelling and experimental validation of the flow behaviour of a glass mat reinforced thermoplastic (GMT). In addition, the interaction of GMT and unidirectional (UD) tape inserts is investigated. The simulation model is set up in LS-Dyna. To model the high degree of deformation of the GMT, the smooth particle hydrodynamics (SPH) method is used. A viscoplastic material model is applied to account for strain rate as well as strain hardening flow behaviour. For the experimental validation of the numerical investigations, a heated plate die was designed, which contains two internal pressure sensors as well as a temperature sensor. With the help of this experimental setup it is possible to investigate the pressure increase, pressure differences and surface temperatures of the GMT as well as the time-dependent position of the flow front. In addition to the pressure differences across the contact area between the die and GMT, there are differences in wall thickness, fibre orientation and fibre matrix separation as a function of the flow path.