Thermoplastic composite and steel insert hybrid design approach: application to an automotive cross-member suspension system

L. Quagliato, Y. Kim, H. Sangun, J.H. Fonseca, H. Lee and N. Kim
Sogang University, Gyeonggi-do, South Korea

Keywords: Metal-polymer hybrid, Hybrid material design, Virgin-vs-recycled fibers analysis, Material characterization, Lightweight design.

This research highlights the design methodology and the performances assessment of a commercial vehicle cross-member designed with a steel inner frame and an injection molded outer skin. Firstly, the material characterization of the short carbon-fibers (CF) filled polyamide (PA) and polypropylene (PP), engineered considering both virgin and recycled carbon fibers, is presented and details: i) the influence of the extrusion process parameters on the injection molding pellets mechanical properties, ii) the influence of virgin and recycled carbon fibers on the mechanical properties and iii) the fatigue performances and damage evolution of PA-CF and PP-CF when subjected to cyclic loadings. Secondly, a design procedure for the steel insert and PA-CF skin cross-member is defined in order to optimize the component shape with the aim of granting same, or better, deflection and endurance performances in comparison to the original full steel component. The defined procedure allows to identify the region of the i-iteration model where a lower plastic skin is required and those where a higher thickness is required, allowing to smartly redeploy of it. According to the proposed methodology, the analyzed cross-member weight could be reduced of 15% granting an improvement in static deflection, endurance and dynamic response.