Structural Crashworthiness and Safety
Aluminum vehicle structures absorb energy exactly the same way as steel: by the deformation, folding, and concertinering of the front longitudinal-box structural beam members. The amount of energy absorbed is related to the yield strength of the material, its thickness, and the rate at which the material work hardens as it is deformed. The aluminum can be in the form of sheet structural assemblies, extruded beams, or even as ductile castings.
Comparative tests with steel show that a spot welded and bonded aluminum box beam will absorb as much energy as a similar steel beam at 55 percent of steel's weight. This same relationship applies for bending collapse. Also, just as with steel, the geometric design and dimensioning of the energy absorption members are critical to ensuring that folding collapse develops and that premature buckling does not occur at the base of these units.
One very significant advantage of aluminum is that a light car does not have to be a small car. Therefore, by using aluminum, it is possible to provide large front and rear crush zones for protection of the passenger compartment without incurring corresponding weight penalties.
Proof that aluminum can do the job includes the following examples:
- The GM EV1, with a full aluminum frame, has been successfully designed to meet U.S. Federal Motor Vehicle Safety Standard impact requirements at a gross vehicle weight of almost 3,000 lbs, even though it is a car with short front and end crumple zones.
- In 35 mph barrier impact testing done by Ford, the aluminum-intensive Taurus/Sable AIV performance generally matched or exceeded that of the equivalent steel production Taurus DN5 model. Both vehicles comfortably exceeded the National Highway Traffic Safety Administration (NHTSA) test criteria.
- Audi has published impressive figures on the crash performance of the A8's aluminum spaceframe. In this vehicle, extruded aluminum tubular front end energy absorption members have been designed so that, after an accident involving the collapse of these tubes, they can be replaced without disturbing the bulk front end structure.
Frontal Barrier Crash Results for Ford DN5 Steel /AIV Vehicles
Frontal Barrier Crash Results for Ford DN5 Steel /AIV Vehicles
| (Driver side safety belt and airbag)* |
| AIV | Steel | NHTSA Req. |
| Dynamic Crush (in) | 30.8 | 28.4 | — |
| Head Injury Criteria | 549 | 524 | 1000 |
| Chest Acceleration (g) | 37 | 53 | 60 |
| Chest Displacement (in) |
1.4 | 1.4 | 3.0 |
| Torso Belt Load (lbs) |
1219 | 1686 | — |
| Left Femur (lbs) | 697 | 1644 | 2250 |
| Right Femur (lbs) | 906 | 1092 | 2250 |
| *Provided by the Ford Motor Co., Dearborn, MI |
Crash Performance of the Audi A8
Crash Performance of the Audi A8
| Driver | Passenger | Limit Values |
| Head Injury Criteria HIC |
531 | 424 | up to 1250
1250-1500 | Green*
Orange* |
| Resultant Head Acceleration (g) |
61 | 54 | up to 90
91-110 | Green
Orange |
| Head Pitch Angle |
40 | 50 | — | — |
| Resultant Chest Acceleration (g) |
56 | 57 | up to 60
61-70 | Green
Orange |
| Resultant Pelvis Acceleration (g) |
61 | 66 | up to 55
56-77 | Green
Orange |
| Force on Thighs (lbs) |
530 | 587 | up to 1349
1350-2248 | Green
Orange |
| Trip Time after Impact (ms) |
15 | 23 | — | — |
*Green= low injury risk
*Orange= medium injury risk |
