Enhancing composite material structures simulation with multi-scale approach

Global automotive industry is strongly driven by innovation necessities to comply with fuel economy regulations, emissions, performance and recyclability, so that the interest and utilization of composite materials is very high due to their unique mix of characteristics. This opportunity is taken in many parts of the car to ensure low weight, corrosion resistance, good energy, complex shape molding and vibration absorption; given these advantages, there are also drawbacks related to manufacturing cost optimization and process complexity which, by the way ,largely affects also the mechanical properties of the component: fiber orientation, presence of weld lines and defects play a major role in the final strength of the part and in damage onset. This latest aspect is of paramount importance considering that at present day numerical simulation accuracy is mandatory to optimize structural performances to reach targets and that classical numerical models should be enhanced and refined to comply with composite materials peculiarities with respect to classical ones. This treatment aims precisely to verify the improvement in finite element analysis representativeness of the component by exploiting the so called “multiscale” approach, which means considering and implementing properties belonging to micro-material level up to full component level. Describing the complete microstructural evolution is not a viable path due to computational cost, instead homogenization techniques have increasingly gained in importance to couple the micro scale to the macro output and for such reason several algorithms and commercial software doing this job are on the market. In order to verify the improvement in FEA by using multiscale approach at first a test campaign on experimental specimens, all made of thermoplastic glass fiber reinforced Polypropylene, is done to fine tune the ability to model the composite material in a proficient way in a multiscale methodology chain and to verify correlation between the new advanced finite element coupled analysis and experimental results. As a further step, multiscale approach is used on a more complex structure like an omega beam, where the variability on fiber orientations and inputs coming from the manufacturing process is greater, in order to appreciate the representativeness improvement of the model over the standard method.