Life cycle assessment of carbon fiber-reinforced polymer composites

Abstract

The use of carbon fiber-reinforced polymer matrix composites is gaining momentum with the pressure to lightweight vehicles; however energy intensity and cost remain major barriers to the wide-scale adoption of this material for automotive applications. This study determines the relative life cycle benefits of two precursor types (conventional textile-type acrylic fibers and renewable-based lignin), part manufacturing technologies (conventional SMC and P4), and a fiber recycling technology. A representative automotive part, i.e., a 30.8-kg steel floor pan having a 17% weight reduction potential with stringent crash performance requirements, has been considered for the life cycle energy and emissions analysis. Four scenarios—combinations of the precursor types and manufacturing technologies—are compared to the stamped steel baseline part. The analysis finds the lignin-based part made through P4 technology to offer the greatest life cycle energy and CO2 emissions benefits. Carbon fiber production is estimated to be about 14 times more energy-intensive than conventional steel production; however, life cycle primary energy use is estimated to be quite similar to the conventional part, i.e., 18,500 MJ/part, especially when considering the uncertainty in LCI data that exist from using numerous sources in the literature. The sensitivity analysis concludes that with a 20% reduction in energy use in the conversion of lignin to carbon fiber and no energy use incurred in lignin production since lignin is a by-product of ethanol and paper production, a 30% reduction in life cycle energy use could be obtained. A similar level of life cycle energy savings could also be obtained with a higher part weight reduction potential of 43%.