• A high-fidelity finite element model of the human-seat cushion system was developed based on CT imaging, enabling integrated assessment of stress, dynamic response index, and injury probability.
• The double-layer cushion, combining high-rebound and slow-rebound materials, significantly reduced peak stresses in L4-L5 and L5-S1 intervertebral discs compared to a high-rebound cushion.
• The double-layer cushion lowered the Dynamic Response Index by 1.8% and reduced spinal injury probability by 10.6%, offering a higher safety margin under ejection conditions.
• A cross-validation pathway between static pressure distribution and dynamic response was established, enhancing the engineering applicability of the model conclusions.