Research and/or engineering questions/objectives (100 words): Substantial research has been dedicating to investigating new materials to replace GCI brake rotors to offer a reduction in emissions, wear, and corrosion. However, these may give rise to other problems, such as worsened environmental impacts at manufacturing phase. This research applies a developed Life Cycle Assessment model to quantify the environmental impacts of a lightweight PEO aluminium alloy rotor compared to GCI across the full life cycle. The objective is to assess the benefits of weight reduction within a braking system from an environmental viewpoint, as well as ensuring no problem shifting occurs. 

Methodology: Life Cycle Assessment (LCA) is a cradle-to-grave methodology to assess and quantify the environmental impacts of a product. The LCA has been applied to a Lightweight PEO Aluminium Alloy rotor and a traditional uncoated GCI rotor for a baseline comparison. The serviceability of the rotors is defined using a functional unit for a fair comparison. This is the decelerating of a vehicle over a specified lifetime based on the WLTP cycle. The emissions and impacts are allocated by mass of the products/by-products. 

Results: A self-built Matlab model has been used to produce the results, making it forwards compatible with testing other brake rotor materials and adjusting to new legislation. This paper presents the results for the full life cycle of both rotors, indicating the benefits of lightweight rotor materials. These results provide a breakdown as to how the environment is affected at each stage of the life cycle, displaying a detailed overview of how problem shifting can be avoided to ensure the full life cycle offers reductions in environmental impacts. The potential benefits of recycling a rotor through recoating can also be demonstrated to reduce impacts associated with manufacture. 

Limitations of the study: The main limitation of any LCA study is data availability. A big restriction is the confidentiality and complexity of the constituents that go into making a brake pad. Due to the emissions and performance being very dependent on the frictional interface the pad was included within the study. Assumptions are made that the manufacturing phase of the pad is consistent between rotors in terms of energy usage and emissions. Therefore, with this being a comparative study these can be assumed to be same between the two rotors and so omitted. The section of life cycle where they will differ is during use. With the testing having been done in house at University of Leeds, data is not an issue for both components here. 

What does the paper offer that is new in the field in comparison to previous research: There has been significant research investigating the benefits of new materials within a braking system to overcome the drawbacks of GCI and to meet new legislation. However, investigation into the whole life cycle is limited. The benefit of this is to understand, if any, problem shifting occurs between life cycle phases. Currently the existing LCA applications have been limited to coated GCI rotors and do not investigate the benefits of a lightweight material. This paper also builds on previous research by the same authors that focused on the development of the methodology for a brake rotor application. The methodology has now been applied on the full life cycle of both rotors, providing a detailed breakdown of environmental impacts at each stage. 

Conclusion: Results show a detailed breakdown of environmental Impacts at each stage of the life cycle. These results indicated the potential environmental benefits of a lightweight material for a brake rotor as well as those associated with the ability for closed loop recycling through recoating rotors.

Matthew Currie, David Barton, Yue Huang, Peter Brooks, Suman Shrestha