Development of a New Flammability Test Method: Enabling Material-Level Evaluation of Polymeric Materials for Electric Vehicle Battery Enclosures

The need to reduce weight and cost of battery systems for electric vehicles has led to continued interest in metal-to-plastic substitution and mixed-material designs for battery enclosures. However, the ever-increasing performance requirements of such systems pose a challenge for plastic materials to meet. In an effort to design a cost-effective, lightweight next-generation battery enclosure while meeting the latest requirements, a new thermal runaway test method was developed, and several materials were screened. The objectives of this development project were twofold. The first was to develop a small-scale test method representative of real-world thermal runaway conditions that could be used early in the design process. The second was to demonstrate the capability of the test method as a materials screening tool, and to provide a comprehensive set of test data that could inform material selection and design of next-generation battery enclosures based on performance requirements and assembly architecture. For this project, the test matrix included both thermoplastic and thermoset materials, with discontinuous and continuous glass fiber reinforcement. Preliminary tests have shown promising results, determined by yield at peak pressure, indicating that both thermoplastic and thermoset materials could meet performance requirements depending on additional system features such as seals, vents, and assembly free volume. This test set-up has demonstrated a capable and repeatable new method to efficiently screen material-level performance that can correlate to the expected performance of an assembly-level test.