**4. Injury analysis for the side-facing seated occupant**

The results in Section 3 show that a side facing seated occupant could have high risk of head and chest injuries even at a moderate severity frontal crash. Our other previous study [84] concluded that as a frontal crash severity increased above 40 kph or 25 mph delta velocity, the estimated injury risks for the body regions of head, chest, abdomen, pelvis, and knee-thigh-hip of the side-facing seated occupant increased significantly.

In real-world vehicle crashes, a lateral-facing seated occupant could also be exposed to various impacts other than a frontal crash, such as the oblique, side, and rear vehicle crashes. In this study, we investigated a mid-size male occupant on a 2nd row side-facing seat in a minivan subject to various crash pulses from the current US regulatory vehicle crash tests. The objective was to better understand the body injury risks and restraint protection effectiveness for such a side-facing seated occupant.

The general approach went through the three phases: 1) selected the vehicle crash test cases, collected the test data, and performed the vehicle crash test simulations; 2) performed the occupant simulations and injury analysis; 3) developed new restraint concepts for the occupant protection (the methods and results from this phase will be summarized in Section 5).

### **4.1 Methods**

In this study, the case vehicle was a US minivan with redesigned seating arrangement for a conceptual automated vehicle.

Eight US regulatory vehicle crash tests for the minivan were considered, as listed in **Table 3**, including the US NCAP rigid barrier frontal crash (FC-RB), the IIHS 40% offset deformable barrier frontal crash (FC-ODB), the IIHS small overlap rigid barrier frontal crash (FC-SOB), the US NCAP moving deformable barrier near side crash (NS-DB), the IIHS moving deformable high barrier near side crash (NS-IDB), the US NCAP moving deformable barrier far side crash (FS-DB), the IIHS moving deformable high barrier far side crash (FS-IDB), and the NHTSA rear crash sled test (RC-RL).

The vehicle side crash tests listed in **Table 3** were simulated. The vehicle FE model was originally obtained from the public resource hosted by George Washington University National Crash Analysis Center (NCAC). Further updates were made on the side door structures of the minivan model. Correlation of the maximum side door


#### **Table 3.**

*The US regulatory vehicle crash tests for the minivan investigated in this study.*

structure deformation against the measured data were achieved. The updated vehicle FE model consisted of 572,555 elements, 604,821 nodes and 694 parts. **Figure 8** shows the vehicle crash simulation model setup for the four side crash tests, in which coupled vehicle crash and occupant simulations were performed.

For simulations of the vehicle frontal, oblique and rear crash tests listed in **Table 3**, a simplified vehicle FE model with 148,437 elements, 153,155 nodes and 47 parts was developed from the original NCAC model. The vehicle crash pulses from the frontal and oblique tests were collected and applied to the vehicle model, as shown in **Figure 9**.

For the occupant simulations, the GHBMC M50-OS v1.8.4 model (updated internally) was used to represent a 50th%ile male occupant. **Figure 10** shows the occupant model setup with the interior seating configuration of the minivan. The occupant restrained with a 3-point seatbelt was placed on a concept bench seat (case seat) on the frontal right side in the middle of the vehicle, surrounded by a 1st row right hand side (RHS) seat on his right, a 2nd row rear-facing seat on his front, and the rear-seat on his left.

The case seat model consisted of the cushion, seat pan and seatback. The material models of the cushion foam and the cover fabric were carried over from the validated mechanical properties of a passenger seat. The 1st row RHS seat was represented by a validated production passenger seat FE model as a surrogate.

The occupant seating under gravity was simulated initially. Each simulation run through 150 msec of termination time. The final occupant seating position and posture were then defined along with the seat cushion and seatback geometry profiles from the seating simulation at the time when the occupant achieved his equilibrium seating position.

For each of all the US regulatory vehicle crash tests listed in **Table 3**, the vehicle and occupant simulations were conducted. From the occupant simulation results, we analyzed the occupant kinematic and kinetic response, as well as the injury measures and risks estimated from the injury risk functions summarized in **Table 2**.
