Temperature influence on impact protection performance of steel-plastic structures – manifested by head impact against pillars of passenger car

Abstract Structures for impact protection often consist of multiple thin-walled sections with metallic and polymer-based materials for lightweighting. In the range of vehicle service temperature from -40 °C to 80 °C, mechanical properties of steels are not temperature sensitive while those of polymer-based materials may change as much as three times, causing different impact responses of steel-plastic structures in summer and winter. The temperature dependent structural behavior is further compounded by limited space for intrusion. Vehicle B-pillar has a thin-walled steel section for meeting its stiffness and strength requirements and a thin-walled plastic trim interior for occupant head impact protection. The structure has limited depth along the impact direction and its materials have different temperature properties, and therefore, it is a good example for analyzing temperature influence on impact response of steel-plastic structures. In this study, we have revealed that the impact response is highly temperature dependent and the mechanisms of causing downgrade protection performance are different in winter and summer. For head impact against vehicle B-pillar interior, at winter temperature, the plastic trim is harder, and thus the peak acceleration of the head is greater than that at room temperature, which is not good for protection. At summer temperature, the plastic trim is softer, and thus the head impact tends to bottom out the plastic trim and the residual kinetic energy would further deform the steel section, leading to higher peak acceleration and larger intrusion than that at room temperature.