Quantitative methods of materials substitution: Application to automotive components

Two quantitative methods of materials substitution are presented. The first method, performance/cost, allows the designer to either look for a substitute material of similar performance at a lower cost or for a material with better performance but at a higher cost. The second method, compound objective function, allows the designer to develop different substitution scenarios based on the relative weights allocated to the different performance requirements. Using the two methods to examine the case of material substitution for interior motorcar panels yielded consistent results. Composites of polypropylene reinforced with 40% hemp or flax fibres rank highest when cost is important, while wood and cork rank highest when aesthetics and comfort are emphasized. These results are consistent with the current trends in industry.