Engineering Sustainability of Mechanical Recycling of Carbon Fiber Composite Materials

The high demand for carbon composite in many industries results in an increase in the embodied energy footprint of carbon composites. Recycling technologies for carbon composites are being developed to reduce the embodied energy footprint of the material. The purpose of this research is to analyze and estimate the specific energy consumption from mechanical recycling method, specifically a ball mill with an air-classifier, which is not yet widely applied. The milling process is the most important step in recycling composites. The input energy requirement on milling process is calculated theoretically based on industrial scale (18ft x 22ft) over-flow ball mill based on different feeds and product sizes. It was assumed that the recycling process rate was 2100 ton/year. The specific energy for recycling carbon fiber reinforced plastic (CFRP) was significantly less than the embodied energy of virgin CFRP. Although the energy consumption depends on the method of recycling CFRPs, the difference in embodied energy between virgin CFRP and recycled CFRP can be very significant. The result shows that there can be environmental benefit from utilizing carbon waste with relatively low milling consumption in mechanical recycling. This research can provide further direction on how to model a closed loop of the overall composite recycling process.