Analytical Failure Modeling of Thermal Interface Material in High Voltage Battery Modules in Electric Vehicle Crash Scenario

Battery Electric Vehicles (BEVs) are becoming more competitive day by day to achieve maximum peak power and energy requirement. This poses challenges to the design of Thermal Interface Material (TIM) which maintains the cell temperature and ensure retention of cell and prevent electrolyte leak under different crash loads. TIM can be in the form of adhesives, gels, gap fillers. In this paper, TIM is considered as structural, and requires design balance with respect to thermal and mechanical requirements. Improving structural strength of TIM will have negative impact on its thermal conductivity; hence due care needs to be taken to determine optimal strength that meets both structural and thermal performance. During various crash conditions, due to large inertial force of cell and module assembly, TIM is undertaking significant loads on tensile and shear directions. LS-DYNA® is used as simulation solver for performing crash loading conditions and evaluate structural integrity of TIM. Prior literature discuss usage of MAT138 (Cohesive mixed mode), MAT169 (Arup adhesive) for modeling TIM adhesive failure. To generate such material models, there is extensive coupon level testing needs to be performed. In early development of battery module design, such sophisticated failure models are not feasible to implement. To overcome this challenge, TIE BREAK contacts in LS-DYNA® are leveraged to define interface failure for quick turnaround. TIE BREAK is penalty-based contact definition which allows to model both tensile and compressive forces until failure on adhesive/glue. Variation studies could be performed in short time for designing the required TIM strength before generating detailed material models. Various techniques available in TIE BREAK contacts such as failure initiation (force based/stress based), shell offset and critical parameters are iterated to arrive at more appropriate modeling considerations. In this paper, contact-based failure is compared with various material-based failure models to gain confidence and simplify design iterations for selection of appropriate TIM.