This is an interesting question.

Due to the fact, that the mass of a car influences all driving resistances, excepted aerodynamic drag forces, lightweight design plays an important role for increasing driving performance and reducing fuel consumption. Some information about driving resistances and their different influencing factors can be found in:

https://www.researchgate.net/publication/280303367_Basics_of_longitudinal_vehicle_dynamics

In general, different materials are used in automotive body and chassis structure: Steel, high-strength steel, aluminum, plastics (e.g. as body panels) and carbon fibre. The decision, which material is the optimal one for a certain car model is influenced by different factors, e.g. design-related aspects, safety aspects, lightweigt requirements, connection technology, number of production per year, existing production facilities, investment costs, costs per unit, and life-cycle related aspects.

As a rought estimation, the followign lightweigt potential is provided by alternative materials in comparison with standard steel: high-strengh steel (10% weight reduction), aluminum (30-40% reduction), carbon fibre (50% reduction). Out of cost, production and safety reasons (e.g. crash behavior), combinations of the materials are used in some BiW design, which leads to reduced reduction of lightweight potential.

Different materials have varying deformation behavior, which influences the characteristics in case of a crash. In this context, steel has some advantages, but also aluminum can be used for bumber and crash box design. Carbon fibre are topic of research in this area.

Kind regards,

Mario

Conference Paper Basics of longitudinal vehicle dynamics