Lightweight solutions for vehicle frontal bumper: Crash design and manufacturing issues

Vehicle impact on the environment is one of the main concerns in recent years and is encountered in several ways throughout vehicle life cycle. On one hand, fossil fuels are still the main energy source for automobiles and this results in a very large amount of global emissions of Green-House-Gasses (GHG) and in particular of CO2. A large contribution to the noxious gas emission reduction can come from vehicle lightweight design, through the adoption of lighter material solutions. On the other hand, the request of material recycling at the vehicle end-of-life is growing and it is clearly not sufficient to recycle only its metallic part. Therefore, lightweight design together with end-of-life recyclability are the major challenges for car manufactures and have leaded law makers to set even stricter rules and legislations to contribute to protect the environment. Vehicle fuel consumption and, consequently, noxious gas exhaust are directly depending on the vehicle weight, automakers are developing advanced technologies to tackle the issue. This includes improvements to engines, drive trains, transmissions and body aerodynamics of the cars but also the utilization of hybrid or full electric power systems or traditional internal combustion engines operated with alternative fuels. However one of the fundamental and effective means to reduce CO2 emission and end life issues comes through the use of novel lightweight and easily recyclable materials such as composite, particularly composite with thermoplastic matrix as the recyclability of thermo-set resin is still relatively complex. In this work, an automobile bumper subsystem is considered for material substitution and innovative design. A number of different composite material types are examined together with two related manufacturing technologies, namely pultrusion and die forming, pointing out the advantages that can come from each alternative. Finally a novel beam-crash box integrated bumper subsystem made from the selected lightweight materials through die forming process is designed and analysed numerically. The comparison made with the reference steel material solution shows that, through proper geometry optimization, the proposed composite material solution can substitute the current steel solution with a significant weight reduction and comparable or even better performance.