Automotive high-voltage busbars are critical electrical components in electric vehicle battery systems as they connect individual battery modules and form the connection to the vehicle’s powertrain. Therefore, a vehicle crash can pose a significant risk to safety by compromising busbar insulation, leading to electrical short circuits inside the battery. In turn, these can trigger thermal chain reactions in the cell modules of the battery pack. In order to ensure a safe design in future applications of busbars, this study investigated the mechanical behavior of busbars and their insulation. Our results indicated that crashlike compressive and bending loads lead to complex stress states resulting in failure of busbar insulation. To estimate the safety of busbars in the early development process using finite element simulations, suitable material models were evaluated. Failure of the insulation was included in the simulation using an optimized generalized incremental stress state dependent model (GISSMO). It was shown that sophisticated polymer models do not significantly improve the simulation quality. Finally, on the basis of the experimental and numerical results, we outline some putative approaches for increasing the safety of high-voltage busbars in electric vehicles, such as choosing the insulating layer material according to the range of expected mechanical loads.

Analyzing the impact of electrical aging on the lithium-ion cell’s mechanical behavior and safety is an important factor to assess the crash safety of electric vehicles during their lifetime. In this study, fresh and electrical aged state-of-the-art NCM pouch cells were investigated. Aged cells, which were cycled electrically to 90% state of health, under laboratory conditions in electric vehicle battery modules were used. The used charging/discharging strategy represents real customer behavior based on accelerated driving profiles. First, it is shown that electrical aging has a significant influence on the anodes’ and separators’ mechanical properties, which had a lower mechanical strength and stiffness under tension. Additionally, quasi-static cylindrical indentation and three-point bending tests were performed to investigate aging effects on cell level at varying state of charge (SOC). Aged cells with 0% SOC showed a right-shifted force–displacement curve and a 29% lower maximum force compared to fresh cells. Fully charged, aged cells reached a similar maximum force to fresh cells, but faster temperature increase and higher temperature peaks after internal short circuit. Inductively coupled plasma optical emission spectrometry analyses confirmed an increased lithium content on the anode surface, which is indicated in literature as a reason for the increased exothermic reaction of the aged cells. The results indicate a higher safety risk for the aged investigated pouch cells under mechanical loads based on their changed mechanical properties and thermal runaway behavior.

The knowledge about the influence of electrical aging on the behavior of lithium-ion cells under mechanical loads is of high importance to ensure a safe use of batteries over the lifetime in electric vehicles. In order to describe the mechanical behavior in relation to electrical aging, fresh and electrically aged NCM pouch cells were investigated under different mechanical crash loads. For the first time, the aged cells’ behavior under quasistatic lateral loading was taken into account. Aged cells showed lower maximum forces compared to the fresh cells. The reason of the changed mechanical cell behavior was explained with the different buckling behavior of fresh and aged cells by experimental images. Furthermore, quasistatic and dynamic crash tests in cell’s thickness direction were performed at varying state of charge (SOC) and compared to the results of a previously published study. Independently of the testing velocity, the electrically aged cells failed at increased deformation values. This observation was justified by an increased cell thickness due to an additional softer layer, formed on the aged graphite particle surface, which was observed by the means of scanning electron microscopy. Furthermore, the aged cells showed lower failure forces of up to −11% under quasistatic and dynamic loads at 0 SOC. It was also illustrated that electrical aging causes a deeper voltage drop after cell failure, which suggests a higher energy release after the internal short circuit. The investigations show that electrical aging has a significant influence on the mechanical properties of lithium-ion cells and must be taken into account in the safety assessment.

BAM Wegen constructed the first LEAB (in Dutch: Laag Energie AsfaltBeton; in English: Low Energy Asphalt Concrete) test sections in 2003 Compared to conventional hot produced asphalt mixes, the production temperature of LEAB reduced significantly using foamed bitumen. At first the LEAB concept was applied for asphalt concrete bind and base mixtures (AC bind and AC base mixtures). More recently also test sections with Porous Asphalt (PA) have been built with foamed bitumen. The mixture is called LEAB-PA. The slow lane average lifetime of PA16 in the Netherlands is approximately 11 to 12 years. The fast lane average lifetime is 16 years. The predominant damage of PA is ravelling, which is mainly caused by the ageing of the mortar in the PA mix by oxidation and UV light. The lower production temperature of the LEAB-PA procedure reduce the short term ageing of the mortar in the PA mix. Loss of mortar flexibility in the PA mix by ageing of the bitumen is the predominant factor for ravelling. It is expected that LEAB-PA will have a higher resistance to ravelling and a longer life span in comparison with hot produced PA mixes. Since 2010 different test sections with LEAB-PA are constructed combined with a section of conventional hot produced PA with the same mix composition as a reference. The shear moduli (mastercurve) of the mortar of the LEAB-PA and the conventional PA are monitored periodically using DSR tests. Also the penetration and softening point Ring & Ball of the bitumen are monitored. Additionally indirect tensile strength tests and CPX measurements for noise reduction have been executed. After 3 years of monitoring it is