Short fibre reinforced composites (SFRC) are often used for high demanding technical parts. The advantages of these materials, e.g. a high freedom of design and low weight combined with the high speed of the injection moulding process, enables these composites to replace traditional materials. In technical components, ribs are used to provide additional strength or improved bending stiffness in order to obtain the structural demands. Also, by strategically adding ribs to the design, the part wall thickness can often be reduced. For non-fibre filled materials, design rules for rib geometries are widely available. However, when short fibres are added, the fibre orientation determines the local material properties, which on its turn defines the structural performance of the ribs. In this paper, the influence of the rib thickness on the strength of the rib and total injection moulded part is discussed. Therefore, ribbed plates with four different rib thicknesses are produced, by using a polypropylene with 30 % glass fibres. The effect of the local fibre orientation and fibre distribution is experimentally tested by applying a load to the ribs. Through injection moulding simulations with Moldflow Insight, the manufacturing process is simulated with the actual experimental processing settings. A coupling of the injection moulding process with a structural finite element analysis in Ansys is provided by using e-Xstream Digimat software. By mapping the local material properties to the structural mesh, a good correlation between experiments and numerical simulations is obtained.