Use of micromechanical modelling in the material characterisation of overinjected thermoplastic composites

The issue addressed in this paper is the specification of both mechanical and thermal material properties over a range of temperatures associated with the processing of thermoplastic components. The particular process is one of overinjection whereby a short glass fibre reinforced rib section is injected onto a preheated woven glass fibre reinforced base. A major contribution of this research is to show how a variety of micromechanical models may be used to supplement the very inadequate data provided by material suppliers and reduce the need for costly experiments. A total of 31 mechanical and thermal properties over the processing range of 20-260 °C are developed. Finally, these data are used in a finite element based simulation of the manufacturing steps, and numerical results for distortion levels of the component are shown to compare favourably with experimental data obtained from limited tests.