This thesis deals with the performing a simulation model for predicting thermomechanical behaviour of short fibre reinforced composites. For this thesis a multi scale simulation has been performed to predict orthotropic thermal expansions in short fibre reinforced polymers, employing Mori-Tanaka first order homogenization scheme. For evaluating the simulation, several short fibre reinforced polymers have been chosen (PP-GF35, PP-GF40, PP-GF50, PA6-GF50, PPA-GF50, PEEK-CF30, PEEK-GF30). The specific heat capacity of the chosen composites as well as their thermal conductivity was measured by performing several differential scanning calorimetry (DSC) and light flash analysis (LFA) test. Thermal strains of the chosen composites have been measured in two directions in the highest possible operating temperature range with an optical digital image correlation (DIC) setup. The highest observed deviation between the simulation and measurements of thermal strains for PP-Based material, belongs to PP-GF35 with about 35% in at 100°C in transversal direction. For PA6-GF50 the maximum deviation between simulation and measurements of thermal strains occurs at 150°C and is about 20%. The highest deviation between simulated and measured thermal strains for PPA-GF50 is about 29% and occurs at 120°C (around the PPA glass transition temperature). For PEEK-GF30 and PEEK-CF30 the maximum deviation between simulation and measurements of thermal strains are 29% and respectively 40% at 200°C. However for both of the PEEK-Based materials there were no remarkable deviation observed up to the glass transition temperature of PEEK.