Designing againstThermal Runaway: A DFSS-RSM-FMEAFramework Linking Battery Electrochemical Failure Thresholds to EVInterior Fire-Safety Materials

Abstract Electric vehicle (EV) battery fires pose acute occupant safety risks, yet no systematic Design for Six Sigma (DFSS) framework exists to optimize interior fire-safety barrier materials under simultaneous thermal, mass, and toxicological constraints. This study applies a full DMADV methodology to develop and verify a flame-retardant composite phase-change material (FR-CPCM) multilayer barrier for EV interior compartments. Voice-of-Customer inputs from UNECE R100 Rev.3, FMVSS 302, and automotive mass budgets were translated into five Critical-to-Quality targets: fire resistance duration tFR ≥ 18 min, areal density ρA ≤ 2.0 kg·m–2, thermal conductivity k = 0.50–0.65 W·m–1·K–1, hydrogen fluoride (HF) cabin concentration < 30 ppm, and recyclability ≥3/5. Twelve candidate material systems were screened using weighted composite scoring, and an aerogel–PCM–intumescent architecture with a halogen-free APP/EG/MDH flame-retardant system was selected. A three-factor, face-centered Central Composite Design (20 runs) was combined with Response Surface Methodology to model three performance responses simultaneously. Composite desirability optimization (D = 0.72) identified the optimal formulation: 32 wt % PCM, 20 wt % FR loading, and 12 mm barrier thickness. Verification confirmed tFR = 18 min (3.6× UNECE compliance margin), ρA = 1.80 kg·m–2, and k = 0.58 W·m–1·K–1. Failure Mode and Effects Analysis reduced the system risk priority number by 56% (400 → 176 across 12 failure modes). HF toxicological modeling identified a peak exposure of 240× the NIOSH-recommended exposure limit, establishing residual risk quantification as the primary future research priority, alongside full-scale UNECE validation and AI-assisted DFSS integration.