Ford, Warwick Manufacturing Group (WMG), Autotech and GRM Consulting have developed a composite rear suspension knuckle for a C-segment vehicle.

According to Ford, a combination of unique carbon fiber deployment and a bespoke manufacturing process results in a 50% weight reduction compared to the current fabricated steel component. The processing technology introduced in the project is said to be the first of its kind and offers a cycle time of less than 5 minutes. The design of the part is complete and manufacturing trials of the component are currently ongoing to develop the full-scale mass production process.

Collaboration is essential

The automotive industry across the globe is pushing for tighter mass targets to satisfy the ever-increasing stringency over emissions, concern of depleting fossil fuels and customer demand for extended range of electric vehicles. Ford’s global Research and Advanced Engineering group teamed up with Chassis Engineering in the UK to redesign a serial steel suspension component to enable its manufacture as a lightweight composite component. The weight saving in this un-sprung component increases the effectiveness of the springs and dampers, leading to enhanced passenger comfort and driver handling. The newly developed composite part proved appropriate for a high-performance C- segment vehicle.

The two-year project, Composite Lightweight Automobile Suspension System (CLASS), was part-funded by Innovate UK.

WMG used its extensive knowledge of material behavior and state-of-the-art manufacturing cells to enable chassis manufacturer Autotech to design a component that meets the required functional requirements. GRM Consulting, which develops predictive tools for carbon fiber structures in the motorsport industry, made a significant contribution to the project by reducing the amount of physical testing required.

Design approach

During the project, the design of the composite part evolved from a single material part to a multi-material design. Initial surveys indicated that a composite lightweight knuckle could be realized by single material – sheet molding compound (SMC). However, rigorous in-house testing of SMC samples highlighted two drawbacks, namely longer cure times and lack of mechanical properties to meet the load requirements. These issues led the design engineering team toward a multi-material system, where layers of prepreg give the required mechanical properties and co-molding of SMC allows the complicated geometric profiles. Such a technology has been proposed in academia and in the aerospace industry, however the requirements for automotive applications are different and this project is likely to be the first time such technology is implemented. This has been possible as prepreg manufacturing costs are being reduced globally. The approach of combining uni/biaxial prepreg with SMC suggested that the composite component could satisfy the majority of the mechanical strength targets. The design was finalized after extensive simulation and experimental work, which involved optimization for OEM durability and NVH targets.