Making cars lighter to improve fuel economy and reduce CO2 emissions is a continuing challenge to automotive OEMs. Weight reduction efforts usually target body components as these typically have less demanding design and service load requirements than powertrain or chassis applications. Reducing unsprung mass in chassis application has the additional benefit of improving vehicle ride and handling and, while composite suspension components are common in motorsport, to date they have not been used in mainstream automotive applications. The CLASS project set out to investigate the potential benefits of doing so.
The tieblade-knuckle of a Ford Focus rear suspension system was selected as the demonstrator part for the CLASS project, funded by Innovate UK and led by Ford Motor Company, in partnership with WMG, Gestamp and GRM.
WMG carried out materials selection by moulding test plaques and measuring material performance characteristics. This was fed into the design of the part, carried out by Gestamp, before optimisation of the design, carried out by GRM. Additional moulding trials carried out by Ford and WMG using a surrogate geometry at Ford’s Research & Innovation facilities provided the required design for manufacture input which was used by Gestamp to further optimise the design. The complex part has a large number of attachments and must be able to withstand severe in-service and abuse loads. The final design utilised the performance and processing properties of combined continuous and discontinuous carbon fibre composite materials.
The optimised design and manufacturing process developed by WMG resulted in a single moulding, replacing the current multiple-piece fabricated steel component, and made a weight saving in excess of 4.5kg per vehicle, a 35% saving on the current part. This could result in a saving of CO2 over the lifetime of the vehicle and the technology is appropriate for much wider vehicle chassis and body applications.
Alan Banks, Commercial Vehicle Suspension Supervisor, Ford Motor Company