Serious injuries are caused to the chest and thoracic organs both in front and side automobile collisions, and statistical surveys indicate that overall chest injuries are the third most frequent after head and the lower limbs. For safer design of restraint systems and vehicle interiors experimental data has to be obtained to establish chest injury criteria. Unembalmed human cadavers were used to conduct nine frontal and fourteen lateral impacts including four with a simulated arm rest. All impacts used a six inch (15.2 cm) diameter impactor with impact velocities ranging from 12 mph (19.3 kph) to 20 mph (32.2 kph). Chest impacts were also conducted on rhesus monkeys and baboons to establish primate-human injury scaling criteria. Four human volunteers were used to obtain static load deflection curves in the lateral and frontal directions.
The results of the above experiments and those conducted by other investigators are presented and analyzed. The results indicate that muscle force and breath holding in live humans tends to make their chests stiffer than those of unembalmed human cadavers. Maximum forces ranged from five hundred (2225 N) to fourteen hundred pounds (6230 N), maximum deflection from 1.9 in (4.8 cm) to 3.2 in (8.1 cm) and pulse duration from 10 to 47 milliseconds. Rib fractures were observed at the higher velocities around 29.3 fps (8.9 mps). The results of dynamic as well as static tests indicated that maximum deflection and not maximum force is the determining factor for rib fractures. Both in the static and dynamic tests, rib fractures were more frequent at chest deflections of over 3 in (7.6 cm), whereas none occurred at deflections less than 2.3 in (5.8 cm).
In this analysis the above results have been used to suggest chest impact protection criteria both from the standpoint of restraint systems design and vehicle interior design for front and side collisions.