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 degrees 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. (c) 2006 Elsevier B.V. All rights reserved.