Documentation:FIB book/Engineering Design Considerations of Frontal Airbags with a focus on deployment and inflation mechanics

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Overview

Background on Airbags

Airbags are essential safety devices in motor vehicles and when paired with seat belts help to reduce passengers’ injuries during accidents [1]. The introduction of airbags in cars has reduced the occurrence of serious injuries, such as head and facial injuries, in non-fatal motor vehicle collisions (MVCs) [2].  Frontal airbags saved 50,457 lives from 1987 to 2017, and 2790 lives in 2017 in the United States (U.S.)[3]. Airbags minimize injuries in collisions by creating a controlled stopping distance between the occupants and the car interior surfaces and distributing restraining forces over a large surface area to reduce high force concentrations on passengers’ bodies [2].

The airbag restraint system requires critical considerations such as the restraining force, inflation pressure, and contact area between the airbag and the occupant [2],[4]. The performance of an airbag restraint system depends on the deployment and inflation mechanics in a particular vehicle. Ineffective design considerations, such as inflation of airbags during low-severity crashes and inflation for children and small adults, can cause more harm than good, leading to special injury outcomes. Airbags have caused injuries by deploying with too much force or by deploying when a person is in the deployment zone [5]. The National Highway Traffic Safety Administration (NHTSA) has found over 290 deaths occurred between 1990 to 2008 as a result of frontal airbag deflation at low-speed crashes [6]. It should be noted that 90% of the deaths occurred in vehicles manufactured prior to 1998 which included first-generation frontal airbags. Efforts have been made to improve safety. Second generation airbags have been made by depowering inflators so that they inflate with less energy, which reduces the likelihood of injury to people who are positioned too close to the airbag prior to deployment [7]. Amendments to Federal Motor Vehicle Safety Standards (FMVSS) No. 208 were made over the early 2000s to require automotive vehicles to detect occupants that are of smaller weight or out-of-position and to reduce the force of deployment or suppress deployment entirely for these occupants [7]. This led to the development of third-generation airbags, which includes inflation suppression based on occupant size and position, severity and type of collision.

Controversy

In 2014, NHTSA began the largest auto recall in U.S. history, recalling airbags manufactured by Takata Corporation [8]. Approximately 70 million vehicles have been recalled across manufacturers such as BMW, Ford, Honda, and Toyota [4]. Some of the airbags would deploy explosively and send metal shrapnel into the face and neck of occupants. NHTSA found that moisture, aging, and high temperatures damaged the airbag's ammonium-nitrate propellant.

General Motors recalled 30 million cars beginning in 2014 for a defective ignition switch that caused 124 recorded deaths [9],[10],[11]. The ignition switch could be turned off by vibrations in the environment or a smaller-than-required ignition torque, which meant that the airbags could fail to deploy in collisions [12]. Performance tests and validation reports indicated the ignition switch did not meet minimum requirements as early as 2001; however, the problem was continually ignored. A combination of factors, including the cost of fixing the problem, and the view that the switch was a convenience and not a safety issue, lead to the approval of the switch for production [12].

Overview of How Airbags Work

The purpose of an airbag is to provide passive restraint to occupants in the motor vehicle during a collision. The collision between the occupant and the interior of the vehicle can cause fatal injuries to the occupant. Airbag restraint systems are installed in cars to rapidly prevent such severe injuries, primarily by preventing the head and abdominal region from striking the steering wheel and the instrument panel directly [13].

Airbags on the driver’s side are stored inside the steering wheel and those on the passenger’s side are stored inside the dashboard of the car in their deflated state [2].  During a moderate to severe frontal crash, a signal is sent from the deceleration sensor in the airbag systems’ Airbag Control Module (ACM) to an inflator inside the airbag module. (NHTSA defines moderate to severe crashes as “crashes that are equivalent to hitting a solid, fixed barrier at 8 to 14 mph or higher.”) This triggers an igniter inside the inflator to initiate a chemical reaction that produces an inert gas. This chemical reaction then causes the deflated airbag to rapidly inflate under high pressure within 50 ms [14],[15].

In addition to the deployment and inflation mechanics of the airbag system, occupant anthropometry also plays a role in determining the airbag’s effectiveness.  The deceleration force generated by the airbag depends on the inflation pressure of the airbag and the contact area between the airbag and the occupant. Therefore, the design dilemma of airbags results from the need to inflate quickly to the appropriate level of pressure and to produce appropriate pressure-related restraints for occupants of all sizes and weights [2].  

Airbag Deployment

Mechanics

Punch out forces (shown in Red arrows) acting of the thoracic region of a dummy

The airbag deployment mechanics involves two types of forces: (i) punch-out and (ii) membrane forces. Punch-out forces as shown in Figure 1, occur when the occupant is within the airbag deployment zone. The forces are related to internal bag/module pressure, the folded bag’s projected packaged area, and the travel distance of the bag before it unfolds circumferentially. The punch-out loading mechanism could occur while the bag is still inside the inflator module if the occupant’s body is directly against the cover [2].

Fig. 2 Membrane forces (shown in Red Arrows) acting on a dummy as the airbag inflates outside of the airbag module

On the other hand, membrane forces, as shown in Figure 2, occur some seconds after the bag deployment from the module container, while the passenger is still close to the module. This means that the airbag wraps around the body region that is close to the module, usually the chest or the head/neck. When the airbag engulfs the body part, it produces a positive bag pressure and a tensile stress in the bag material. While the bag is being inflated, the membrane forces rise and produce high loads on the enveloped body region which also accelerate the occupant rearward out of the bag [2].

Fig. 3 Six phases of airbag deployment

As shown in Figure 3, airbag deployment is divided into six phases: trigger, time to first gas, unfolding begins, complete unfold, full inflation, and restraint phase [16]. The occupant detection sensor system detects the position of the occupant and adjusts the restraining effect of the airbag.  Another attempt to do that is by having a parallel plate fixed capacitive sensor. That would be installed outside the airbag and measure the passenger’s position and speed. Alternatively, a sensor measuring distance can be placed inside the vehicle compartment. Combining this sensor with the occupant weight sensor, would give the position of the occupant. Each phase affects those sensors as they can change the dielectric value or their capacitance [16]. The three sensing systems, vision-sensing, weight-sensing, and crash-sensing systems, are integrated into the hardware platform and system interface program. Then, that data is processed in the ACM to make the most optimal airbag deployment decision [17].

Deployment Engineering Design Considerations

Designing the airbag deployment system involves consideration of the deployment criteria and deployment time. Deployment criteria refer to the assessment of various crash test sensors to determine if a collision is of a severity that requires deployment [18]. These sensors include accelerometers, impact sensors, brake pressure sensors, and seat occupancy sensors. In particular, there are safing sensors located near the vehicle’s control module to minimize false negatives of deployment during high delta-V collisions [19]. There are also discriminatory sensors near the impact site to minimize false positives during low delta-V collisions. ACM integrates these sensors and utilizes an airbag deployment algorithm [20] which determines whether a crash had enough delta-V to require deployment. The threshold for deployment is not regulated by the FMVSS, but the suggested range is between 16-18 mph (25-29 kmh). This ensures airbags are deployed in moderate to severe crashes [5]. More advanced airbags will consider the weight of the occupant in the airbag deployment algorithm. For small-stature passengers or children, airbag deployment can be suppressed as the risks associated with deployment can be greater than the benefits [21]. Airbag deployment must occur prior to the maximum engagement in a collision before inertia causes an occupant to slide forward into the airbag deployment zone. The ACM continually samples sensors so that the decision to deploy can be made within 45 to 50 ms of a frontal collision [22]. The acceleration and jerk (the third derivative of position over time) are used to predict the severity of a collision, and whether the deployment is necessary [23].

There are many limitations to airbags themselves. Airbag deployment is a one-time mechanism and the airbag must be replaced after deployment. The airbag may not adequately protect the occupant if there are multiple collisions. Deployment when the occupant is out of position, such as when they are too close to the steering wheel, can cause injury [2]. Airbags offer limited protection of the head during underride collisions, in which the platform of a trailer or other elevated vehicle crashes through the windshield of a lower elevated car [24].

Airbag Inflation

Airbag Inflation Mechanics

The deployment and inflation of airbags is driven by the chemical decomposition of sodium azide (NaN3) which is necessary to inflate the airbags within 50 ms [14],[25],[26]. Sodium azide is a highly toxic yet commonly used industrial substance for explosive detonators and propellants[25]. Cars with airbags have a compressed air cylinder inflation module which contains compressed pellets of about 60% weight concentration of sodium azide [25] along with potassium nitrate (KNO3) and silicon dioxide (SiO2) [26]. Upon collision, the ACM enables an electromechanical trigger to thermally decompose NaN3 into nitrogen gas (N2) which quickly and momentarily inflates the airbag to a precalculated volume within the required timeframe[25],[26]. Equations 1 to 3 describes the complete chemical reactions of airbag inflation:

However, significant drawbacks to the use of sodium azide are its environmental impacts and toxicity to humans. Azide is especially hazardous in aqueous environments as it is readily protonated, resulting in volatile hydrazoic acid (HN3) which is also an airborne hazard[25]. Azide is also a potent biocide comparable to cyanide and sulfide[25]. As there does not exist regulations to mandate the recycling of airbag inflators, airbag inflators often end up in scrap yards[26]. In the United States, 10-11 million vehicles are annually retired to junkyards with each vehicle containing an average of 300 g of NaN3 [26].

Inflation Engineering Design Considerations

Fig. 4 Force distribution of the airbag on occupant body (Left: Side view, Right: Top view)

The design of airbag inflation mechanisms has the following key considerations: inflation and deflation rates, pressure exerted onto the occupant, airbag volume, and airbag geometry. These design specifications are crucial to ensure that the force distribution of the airbag (see Figure 4) adequately protects the occupant during a collision while limiting the risk of airbag inflation injuries. Airbag designs must also fall within the injury targets for major frontal loading conditions outlined by the US FMVSS 208 regulation [27]. Additionally, car manufacturers may also design airbags accordingly to achieve a high US-NCAP rating score through reducing the risks and severity of head, neck, chest, and femur injuries for frontal impact loading [27].

Inflation & Deflation Time

Designing an appropriate inflation time is critical for safety. Airbag inflation needs to take enough time to not cause inflation injury to the occupants while being short enough so that the occupant does not interact with the interior of the car [2]. Airbags must deploy and inflate in 50ms during a car crash to prevent injury to the occupants [14]. The inflation time is also confirmed by Omura and Shimamura as they graphed the pressure waveform and concluded that the time at which the airbag is fully inflated is less than 50 ms [28]. The inflation time and volume of the airbag are closely correlated to provide timely occupant restraint [2]. The deflation time is also an important characteristic of airbags. One paper’s graph depicts that the airbag deflation time is around 150 ms when the airbag pressure reaches 0 ms again [28].

Pressure

The pressure waveform of the airbag outlines the pressures of the airbag at different times during inflation[28]. The pressure waveform changes based on gas flow characteristics from an inflator, gas exhaust characteristics from the bag vent, and the volume of the bag[28]. The changes to the pressure waveform can affect how the occupant interacts with the airbag and their deceleration times[28]. Additionally, the airbags need to supply the correct pressure restraint for the occupant[2]. This incorporates challenges into the design of airbags as a smaller occupant will receive greater restraint forces whereas a larger occupant will not receive enough restraint force as the airbag was initially tested with a 50th percentile male[2],[29].

Volume

The maximum volume of the airbag can be approximated by the chemical reaction that initiates airbag inflation by producing nitrogen gas[25]. However, airbag volumes can differ depending on several factors including the model of the inflator, type of airbag, airbag unfolding process, car geometry, occupant anthropometry, and occupant position. As well, the airbag on the driver's side is substantially smaller in volume than on the passenger side due to the presence of the steering wheel. The passenger side frontal airbag is also designed considering lower injury tolerances since the passenger occupant is primarily modeled by the Hybrid III 5th percentile female Anthropometric Test Device (ATD)[27]. The 5th percentile female ATD is more sensitive to injury, particularly neck injuries, compared to the Hybrid III 50th percentile male ATD which is most commonly used to model the vehicle driver[27]. An inflator on the driver’s side yields approximately 28-45 L of N2 while a passenger’s side yields approximately 140 L[25]. This volume is determined by the amount of NaN3 that is converted to N2 where each gram of NaN3 generates 0.56 L of nitrogen gas at standard ambient temperature and pressure[25]. Once inflated and makes contact with the occupant, the airbag rapidly deflates through vents in the airbag to ensure a cushioning impact[15].

Shape

Frontal airbag geometry is designed according to the vehicle interior, particularly the A-pillar section of the car which is the structure of the car that partially frames the windshield [27]. Park describes the important considerations of the width and depth of the frontal airbag [27]. For example, the longitudinal distance, or depth, of the airbag must ensure that the airbag does not come into contact with the occupant before it is fully deployed while also sufficiently protecting the occupant from extensive neck flexion. The width must also proportionally cover the A-pillar section of the car such that the occupant head does not come into contact with the vehicle interior. The geometry must also ensure that the airbag fits snuggly such that it does not wiggle or rotate. Fully deployed airbag shapes may also differ slightly from the designed airbag geometry as the fabric material of airbag cushions also stretch during deployment [27]. As well, some airbags contain internal tethers to control the fully deployed shape [27].

Airbag Inflation Methods and Limitations

Due to the rapid inflation and deflation of airbags during a collision, it is difficult to determine the precise airbag volume and pressure at a specific time during a crash sequence. As crashes also differ in car model, airbag model, occupants, and collision events, airbag volumes as a function of time would also differ from crash to crash. Throughout the last few decades, several approaches have been developed to better model airbag inflation.

High-Speed Cameras

One of the methods of observing airbag inflation and deflation is using high-speed cameras with optical markers on the airbags [15]. For example, Anliot used a camera system to develop a visual hull method of reconstructing and estimating airbag inflation and deflation [15]. However, Anliot found that the analyses are time and resource extensive due to a full camera setup and  full visibility proved difficult to achieve especially within a vehicle in the presence of a vehicle occupant. Studies with high-speed cameras are also not easily repeatable as camera configurations and visibility may vary widely.

Numerical Models

More recent approaches have used computational numerical models. The most popular approach is the control volume (CV) mathematical model as it offers simple modeling and fast calculations [30]. This model assumes that the gas is uniformly distributed within the inflated bag and thus, assumes the airbag is subject to uniform pressure [30]. More recently developed algorithms include the Arbitrary Lagrangian-Eulerian (ALE) method and Corpuscular Particle method (CPM) which can more accurately simulate high-speed airflow effect during the initial unfolding stage of airbags. However, these numerical models require higher computer resources [30]. Hu and Huang (2012) and Kaika (2013) compared these three methods and found that the CV method was most suitable for airbag modeling when the occupant is in position, while ALE and CPM  are better suited to analyze airbag deployment and inflation when occupants are out of position [31],[32].

Computer Aided Engineering (CAE) Simulations

Lastly, studies have used CAE to simulate occupant responses to airbag inflation. CAE simulation software includes MADYMO, LS-DYNA, PAM-CRASH, and MSC/DYTRAN and typically employs the numerical models discussed above [32]. For example, Park uses LS-DYNA to simulate sled testing to optimize the passenger airbag design to achieve the five-star US-NCAP performance for frontal crashes [27]. CAE offers advantages such as repeatability, low cost, and limited required resources such as physical ATDs. CAE can also model occupant impact responses to predict occupant injuries [32].

Airbag Inflation Injuries

Airbags have the potential to cause serious injuries to occupants. Occupants can accelerate rearward by the force applied by the airbag and experience head and neck injuries[2][15]. This may happen if the forces inside the airbag inflate the airbag incorrectly in a concave saddle shape, rather than a convex saddle shape or if the bag wraps around the chest and head or neck[15]. NHTSA describes 3 injury patterns from inflation-induced injuries[15]:

  1. Multiple bilateral rib fractures, and thoracic organ injuries with AIS >=4
  2. Basilar skull fractures, cervical spine trauma
  3. Serious cardiac injuries

Injuries to the thoracic and abdominal regions are also reported due to incorrect occupant position[15]. Other injuries can be caused by the airbag hitting the arm or leg of an occupant once it has already interacted with the car’s interior surface[2],[15].

Future Developments of Airbag Mechanisms

Future developments of airbag deployment include pre-collision deployment and additional placements. Pre-collision deployment can be achieved through a pre-crash algorithm which detects the trajectories of incoming frontal objects and behavior of the host vehicle to then estimate an impending crash scenario[33]. Pre-collision deployment would allow the airbag to inflate over a longer period of time, reducing inflation-induced injuries. Obtaining inputs for a pre-crash algorithm would require several sensors installed in a vehicle’s ESP (electronic stability program) system such as: wheel speed, yaw rate, steering angle, lateral acceleration, and radar sensor [33].

Another improvement is to add airbags in additional places in the vehicle. Mercedes-Benz is developing airbags that could be deployed from underneath the car. This could stop a vehicle before it crashes when the car’s sensors determine that an impact is inevitable. The underneath airbag would have a friction coating to help the car slow down, double their stopping power, and prevent a collision from occurring. This improvement counters the car’s dipping motion during braking, prevents passengers from sliding under their seat belts, and improves bumper-to-bumper contact [34]. Airbags should evolve with the advancement of autonomous vehicles and protect occupants who may have greater degrees of freedom and thus more potential seating positions that would put them out of position of a conventional frontal airbag [35].

Preventing airbag deployment when the occupant is too close to the bag module can prevent inflation-induced injuries. This can be achieved by using ultrasonic, weight-based, and capacitance sensors [2].

References

  1. ↑ H. Shirzadi, H. Zohoor, and S. Naserkhaki, “Biomechanical simulation of eye-airbag impacts during vehicle accidents,” Proceedings of the Institution of Mechanical Engineers, vol. 232, no. 7, pp. 699–707, Jul. 2018, doi: 10.1177/0954411918778063.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 J. W. Melvin and H. J. Mertz, “Airbag Inflation-Induced Injury Biomechanics,” in Accidental Injury: Biomechanics and Prevention, 2nd ed., New York: Springer-Verlag, 2002, pp. 198–206. Accessed: Sep. 28, 2022, doi: 10.1007/978-0-387-21787-1
  3. ↑ National Center for Statistics and Analysis, “Occupant protection in passenger vehicles: 2018 data,” National Highway Traffic Safety Administration, DOT HS 812 967, Jun. 2020. Accessed: Nov. 10, 2022. [Online]. Available: https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812967.pdf
  4. ↑ 4.0 4.1 “Airbags,” IIHS-HLDI crash testing and highway safety.  Accessed: Nov. 10, 2022. [Online]. Available: https://www.iihs.org/topics/airbags
  5. ↑ 5.0 5.1 M. P. McKay and B. T. Jolly, “A Retrospective Review of Air Bag Deaths,” Academic Emergency Medicine, vol. 6, no. 7, pp. 708–714, 1999, doi: 10.1111/j.1553-2712.1999.tb00439.x.
  6. ↑ “Occupant protection in passenger vehicles: 2015 data,” National Highway Traffic Safety Administration, Washington, DC, DOT HS 812 374.  Accessed: Nov. 10, 2022. [Online]. Available: https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812967.pdf
  7. ↑ 7.0 7.1 N.K. Greenwell, “Evaluation of the Certified-Advanced Air Bags,” National Highway Traffic Safety Administration, DOT HS 811 834, Sep. 2013. [Online]. Available: https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/811834
  8. ↑ “Takata Recall Spotlight | NHTSA.” Accessed: Nov. 10, 2022. [Online]. Available:  https://www.nhtsa.gov/equipment/takata-recall-spotlight
  9. ↑ “GM agrees $900m settlement for faulty ignition switches,” BBC News, Sep. 17, 2015. Accessed: Nov. 10, 2022. [Online]. Available: https://www.bbc.com/news/business-34276419
  10. ↑ “GM Ignition-Switch Review Complete: 124 Fatalities, 274 Injuries,” Car and Driver, Aug. 03, 2015. Accessed: Nov. 10, 2022. [Online]. Available: https://www.caranddriver.com/news/a15353429/gm-ignition-switch-review-complete-124-fatalities-274-injuries/
  11. ↑ N. Feeney, “GM Disputes Report Tying Ignition Switch Problem to 74 Deaths,” TIME, Jun 3, 2014. Accessed: Nov. 10, 2022. [Online]. Available:  https://time.com/2819690/gm-recall-deaths-ignition-switch/.
  12. ↑ 12.0 12.1 A. Shaout and C. Dusute, “Where did general motors go wrong with the ignition switch recall?”  IIUM Engineering Journal, vol. 15, no. 2, Art. no. 2, Nov. 2014, doi: 10.31436/iiumej.v15i2.522.
  13. ↑ H. A. Deery, A. P. Morris, B. N. Fildes, and S. V. Newstead, “Airbag Technology in Australian Passenger Cars: Preliminary Results from Real World Crash Investigations,” Journal of Crash Prevention and Injury Control, vol. 1, no. 2, pp. 121–128, Sep. 1999, doi: 10.1080/10286589908915749.
  14. ↑ 14.0 14.1 14.2 “Air Bags | NHTSA.” Accessed: Nov. 10, 2022. [Online]. Available: https://www.nhtsa.gov/equipment/air-bags
  15. ↑ 15.0 15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8 L. Wallis and I. Greaves, “Injuries associated with airbag deployment,” Emergency Medical Journal, vol. 19, no. 6, pp. 490–493, Nov. 2002, doi: 10.1136/emj.19.6.490. Cite error: Invalid <ref> tag; name ":12" defined multiple times with different content
  16. ↑ 16.0 16.1 N. Shirur, C. Birkner, R. Henze, T. M. Deserno, and D. Dudhat, “Effect of Airbag Deployment Phases on Tactile Occupant Detection Sensor,” in 2020 XII International Science-Technical Conference Automotive Safety, Oct. 2020, pp. 1–5. doi: 10.1109/AUTOMOTIVESAFETY47494.2020.9435283.
  17. ↑ M. A. Hannan, A. Hussain, and S. A. Samad, “Decision Fusion via Integrated Sensing System for a Smart Airbag Deployment Scheme,” Sensors and Materials, vol. 23, no. 3, pp 179–193, Jul 16, 2010.
  18. ↑ R. Eppinger, “Occupant Restraint Systems,” in Accidental Injuries, 2nd ed., 2002, pp. 187–197, doi: 10.1007/s00414-004-0475-y
  19. ↑ H. Komaki, M. Wakamoto, H. Konishi, T. Nioka, and S. Kuroda, “Development of the electronic safing system for airbag ECUs.” [Online]. Available: https://www.denso-ten.com/business/technicaljournal/pdf/24-3.pdf. [Accessed: 06-Dec-2022].
  20. ↑ H. C. Gabler and J. Hinch, “Evaluation of Advanced Air Bag Deployment Algorithm Performance using Event Data Recorders,” Annals of Advances in Automotive Medicine, vol. 52, pp. 175–184, 2008
  21. ↑ S. Anishetty, M. Murphy, C. Tieman, and C. Caruso, “Suppression Technologies for Advanced Air Bags,” SAE International, Warrendale, PA, SAE Technical Paper 2000-01-C037, Nov. 2000. Accessed: Nov. 10, 2022. [Online]. Available: https://www.sae.org/publications/technical-papers/content/2000-01-C037/?PC=DL2BUY
  22. ↑ H. Chan et al., “Frontal Air Bag Deployment in Side Crashes,” presented at the International Congress & Exposition, Feb. 1998, p. 980910. doi: 10.4271/980910.
  23. ↑ R. Robertson, C. De Melo, and S. Kodsi, “Acceleration Rate, Change of Acceleration Rate, and Airbag Deployment,” Accident Reconstruction Journal, vol. 27, no. 6, Nov. 2017, [Online]. Available: https://trid.trb.org/view/1514523
  24. ↑ “Fatalities in Frontal Crashes Despite Seat Belts and Air Bags,” National Highway Traffic Safety Administration, DOT HS 811 202, Sep. 2009. Accessed: Nov. 10, 2022 [Online]. Available: https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/811102
  25. ↑ 25.0 25.1 25.2 25.3 25.4 25.5 25.6 25.7 25.8 E. A. Betterton, “Environmental Fate of Sodium Azide Derived from Automobile Airbags,” Critical Reviews in Environmental Science and Technology, vol. 33, no. 4, pp. 423–458, Oct. 2003, doi: 10.1080/10643380390245002.
  26. ↑ 26.0 26.1 26.2 26.3 26.4 A. Madlung, “The Chemistry behind the Air Bag: High Tech in First-Year Chemistry,” Journal of Chemical Education, vol. 73, no. 4, p. 347, Apr. 1996, doi: 10.1021/ed073p347.
  27. ↑ 27.0 27.1 27.2 27.3 27.4 27.5 27.6 27.7 27.8 W. Park and NHTSA, “A Study of Airbag Design & Optimization Methodology,” General Motors, USA, 17–0365, 2017. Accessed: Nov. 10, 2022 [Online]. Available: https://www-nrd.nhtsa.dot.gov/departments/esv/25th/
  28. ↑ 28.0 28.1 28.2 28.3 28.4 H. Omura and M. Shimamura, “Analysis of Airbag Inflation,” SAE Transactions, vol. 98, pp. 297–306, 1989.
  29. ↑ E. R. Braver, S. Y. Kyrychenko, and S. A. Ferguson, “Driver Mortality in Frontal Crashes: Comparison of Newer and Older Airbag Designs,” Traffic Injury Prevention, vol. 6, no. 1, pp. 24–30, Feb. 2005, doi: 10.1080/15389580590903140.
  30. ↑ 30.0 30.1 30.2 Y. Cheng, Y. Li, and C. Yang, “The Design of an Airbag Automatic Inflator and the Simulation Analysis of Airbag in the Unfolding Process,” in 2020 5th International Conference on Mechanical, Control and Computer Engineering (ICMCCE), Dec. 2020, pp. 961–965. doi: 10.1109/ICMCCE51767.2020.00210.
  31. ↑ C. Kaikali and W. Meison, “Comparison on three methods for simulating safety airbag deployment,” Automotive Safety and Energy, vol. 4, no. 3, pp. 250–256, 2013.
  32. ↑ 32.0 32.1 32.2 J. Huang and L. Hu, “A Comparative Study on Airbag Inflation Properties Using CV and ALE-Based Approaches,” in 2012 Third International Conference on Digital Manufacturing & Automation, Jul. 2012, pp. 17–20. doi: 10.1109/ICDMA.2012.5.
  33. ↑ 33.0 33.1 K. Cho, S. B. Choi, and H. Lee, “Design of an Airbag Deployment Algorithm Based on Precrash Information,” IEEE Transactions on Vehicular Technology, vol. 60, no. 4, pp. 1438–1452, May 2011, doi: 10.1109/TVT.2011.2126614.
  34. ↑ V. Kuiper, “Airbags of the Future Will Prevent Accidents,” Mike’s Auto Body, Dec. 01, 2014. Accessed: Nov. 10, 2022. [Online]. Available: https://mikesautobody.com/airbags-future-will-prevent-accidents/
  35. ↑ N. Yang, J. Wang, and T. Liu, “Comparison of the effectiveness of rotating seats in autonomous vehicles and airbags in traditional vehicles to minimize head injuries in frontal crash,” Computer Methods in Biomechanics and Biomedical Engineering, pp. 1–11, Sep. 2022, doi: 10.1080/10255842.2022.2122819.


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