Numerical analysis of occupant injuries in reclined postures during car frontal impact

The results of numerical analysis of the behavior of a human body model in reclined postures are presented. This study explored the effects of seatback angles of 25°, 35°, 45°, and 55° as well as seat pan tilt angles of 5° and 10° on the trend of neck and lumbar injuries in occupants at different collision angles of 0°, 25°, 35°, and 45°. The risk of neck injury for occupants decreases by up to 56.81% with increasing seatback inclination angle, as indicated by N ij for the neck, conversely, the risk of lumbar injury maximum increases by up to 48.96% with increasing seatback inclination angle, as indicated by the lumbar tensile bending moment M y . In addition, as the seatback inclination increases, the forward displacement of the occupant’s head decreases, which alters head kinematics and may reduce or exacerbate head injury risk depending on the collision scenario. Except for the fully frontal collision condition, the upward tilt of the seat pan increases the risk of neck injury for occupants in a high angle seating posture, with a maximum increase of 38.89% in neck N ij and a decrease in lumbar injury risk. The maximum tensile bending moment of the lumbar decreases by 28.28%. The upward tilt of the seat pan in a fully frontal collision condition increases the risk of lumbar injury, with a maximum increase of 15.35% in the lumbar tensile bending moment M y . Meanwhile, altered head dynamics in reclined postures due to reduced forward excursion may lead to increased risk of head-to-structure contact. The results offer a theoretical foundation for exploring occupant neck and lumbar injuries while utilizing reclined seats and intelligent cockpits.