A Finite Element and Multi-body Model of the Pregnant Female Occupant for the Analysis of Restraint Effectiveness

A finite element model of a 7-month pregnant uterus was created and integrated into a multi-body human model. The uterine model contains 11,632 elements and 16,335 nodes. The pregnant occupant model was validated using known abdominal response corridors. Unrestrained, 3-pt belt, and 3-pt belt plus airbag tests were simulated at speeds ranging from 13 kph to 55 kph. Peak uterine strain was found to be a good predictor of fetal outcome (R²= 0.85). The strain in the uterine wall exceeded 60%, sufficient to cause placental abruption, in simulations of no restraint at 35 kph and 3-pt belt tests at 45 kph and 55kph. These tests represent a greater than 75% risk of adverse fetal outcome. For matched tests at 35 kph, strains of 60.8% for the unrestrained occupant, 52.6% strain for the 3-pt seatbelt and only 33.0% strain for the 3-pt seatbelt and airbag combination were recorded. The model proved successful at predicting risk of fetal demise and verified experimental findings noting the importance of proper restraint use for the pregnant occupant.