Biomechanical and injury response to posterolateral loading from torso side airbags

Abstract

This study characterized thoracoabdominal response to posterolateral loading from a seat-mounted side airbag. Seven unembalmed post-mortem human subjects were exposed to ten airbag deployments. Subjects were positioned such that the deploying airbag first contacted the posterolateral thorax between T6 and L1 while stationary (n = 3 x 2 aspects) or while subjected to left lateral sled impact at ΔV = 6.7 m/s (n = 4). Chestband contours were analyzed to quantify deformation direction in the thoracic x-y plane (zero degrees indicating anterior and 180° indicating posterior), magnitude, rate, and viscous response. Skeletal injuries were consistent with posterolateral contact; visceral injuries consisted of renal (n = 1) or splenic (n = 3) lacerations. Deformation direction was transient during sled impact, progressing from 122 ± 5° at deformation onset to 90° following maximum deflection. Angles from stationary subjects progressed from 141 ± 9° to 120°. Peak normalized deflections, peak rates, and VCmax ranges were 0.075 - 0.171, 3.7 - 12.7 m/s, and 0.3 - 0.6 m/s with stationary airbag, respectively; ranges were 0.167 - 0.297, 7.4 - 18.3 m/s, and 0.7 - 3.0 m/s with airbag sled impact, respectively. Peak deflections were measured at angles between 99° - 135° and 98° - 125° for stationary and dynamic conditions, respectively. Because of deflection angle transience and localized injury response, both posterolateral and lateral injury metrics may be required for this boundary condition. Contrasted with flat rigid or anterolateral loading, biomechanical response to side airbag interaction may be augmented by peak normalized deflection or VCmax at 130°.

FIGURE 1

Bench seat apparatus with seat-mounted side airbag placement. Additional details provided in Yoganandan et al. (2007)

FIGURE 2

Chestband locations with respect to specimen anatomy and airbag module locations; only xyphoid chestband was placed on stationary test specimens.

FIGURE 3

RBandPC analysis methodology for chestband contour generation with side airbag boundary condition.

FIGURE 4

Chestband post-processing methodologies for oblique deflection analysis.

FIGURE 5

Stationary airbag deployment scenario.

FIGURE 6

Dynamic late deployment side airbag scenario: (a) prior to airbag activation, (b) posterolateral thoracoabdominal interaction with airbag inflation, and (c) load wall interaction with subject following airbag deployment.

FIGURE 7

Still frames from videography (frontal view) depicting variability in airbag deployment expansion for the four dynamic occupant tests. Duration following airbag activation is noted. Arrows indicate visible airbag fabric.

FIGURE 8

Rib fracture patterns observed during post-test necropsy as viewed from left (L), posterior (P) and right (R) aspects.

FIGURE 9

Chest contours from stationary airbag test demonstrating deformation pattern in posterolateral direction: (a) left aspect deployment (S-3) and (b) right aspect deployment (S-4).

FIGURE 10

Chest contours from dynamic test (D-1) demonstrating deformation pattern progressing from undeformed (U) to posterolateral airbag interaction (A) to maximum lateral deformation (M): (a) xyphoid and (b) axilla chestbands.

FIGURE 11

Grayscale palate representing plotting of oblique deflection measurements.

FIGURE 12

Exemplar normalized deflection traces for 90° through 140° vectors. Grayscale palate is depicted in Figure 11.

FIGURE 13

Exemplar deflection rate traces for θ = 90° through 140° vectors. Grayscale palate is depicted in Figure 11.

FIGURE 14

Exemplar unconstrained deflection plotted with deflections at θ = 90° through 140°.

FIGURE 15

Angle of deflection (θ) for stationary (a) and dynamic late deployment (b) airbag interaction. Shading denotes ± SD corridor.

FIGURE 16

Unconstrained deflection time traces for stationary airbag interaction. Left-aspect response is depicted on left; right-aspect response is depicted on right. Angle (°) at which peaks occurred is indicated by arrow.

FIGURE 17

Unconstrained deflection time traces from chestbands for dynamic close-proximity airbag interaction. Angle (°) at which peaks occurred is indicated.

FIGURE 18

Unconstrained deflection rate and the instantaneous rate of deflection measured at the deflection locus.

FIGURE 19

Deflection rate traces for stationary airbag interaction. Left-aspect response is depicted on left; right-aspect response is depicted on right. Angle (θ) at which peaks occurred is indicated.

FIGURE 20

Viscous response traces for stationary airbag interaction. Left-aspect response is depicted on left; right-aspect response is depicted on right. Angle (θ) at which peaks occurred is indicated.

FIGURE 21

Deflection rate traces for dynamic close-proximity airbag interaction. Angle at which peaks occurred is indicated.

FIGURE 22

Viscous response traces for dynamic close-proximity airbag interaction. Angle (θ) at which peaks occurred is indicated.

FIGURE 23

Angle of deflection (in degrees) for stationary airbag, dynamic airbag, flat rigid wall and oblique load wall configurations. Shading denotes ± SD corridors.

FIGURE 24

Angle of deflection (in degrees) for stationary airbag, dynamic airbag, flat rigid wall and oblique load wall configurations. Shading denotes ± SD corridors.

FIGURE 25

Posterior view of gross visceral anatomy in external context. Modified from Gray (1918).

FIGURE 26

Peak normalized deflection and corresponding maximum thoracoabdominal AIS for deflection angles 140°, 130°, 120°, 110°, 100°, and 90°.

FIGURE 27

Peak deflection rate and corresponding maximum thoracoabdominal AIS for deflection angles 140°, 130°, 120°, 110°, 100°, and 90°.

FIGURE 28

Peak viscous response and corresponding maximum thoracoabdominal AIS for deflection angles 140°, 130°, 120°, 110°, 100°, and 90°.