Supplementary file 1_Enhanced comfort and biomechanical performance of ejection seat cushions via optimal double-layer foam design.docx

IntroductionOwing to inherent structural limitations of conventional single-layer ejection seat cushions, particularly their limited capacity for pressure redistribution, prolonged missions may be associated with inadequate comfort and impaired circulatory function. To address this issue, this study proposed a double-layer cushion design approach and compared three thickness ratios (1:1, 1:2, 2:1) of fast-recovery (N1) and slow-recovery (N3) foam with a single-layer N3 cushion.
MethodsTwo experiments, a sitting comfort test and a material compression test, were conducted to evaluate comfort and mechanical performance. The comfort test (22 participants) collected subjective ratings and interface pressure metrics, while the compression test quantified deformation and load-bearing behavior, allowing comparison of comfort and support among the different cushion structures.
ResultsResults showed that as N3 thickness increased, maximum pressure (Pm) and average pressure (Pv) decreased while contact area (Ac), SPD%, and SAG factor rose; at the N1/N3 ratio of 1:2, these objective indicators reached optimal values, consistent with the highest subjective comfort ratings. In addition, the mechanical metrics matched those of the original cushion.
DiscussionOverall, the double-layer design achieves an optimal trade-off between comfort and support, with the N1/N3=1:2 prototype exhibiting the superior performance. These findings provide a practical optimization strategy for developing high-performance seating systems.