Air Bag System

Seminar report on airbag sysyem

1. AIRBAGS SYSTEM

Manav School Of Engg Page 1

CHAPTER 1


INTRODUCTION




























Fig no: 1.1 Driver and front passenger air bag


For many years, the trusty seat belt provided the sole form of passive
restraint in our cars. Seatbelts have been proven to be effective in saving lives
and preventing or lessening injuries in automobile accidents.. The first passive
restraints were modifications of seat belts themselves; the belts were
coordinated with operations of opening the car doors and starting the
automobile, which caused belts built into tracks in the doors to wrap around
the driver or passenger when the seat was occupied. Concurrently, the airbag
was devised as a secondary form of passive restraint during impact.

Air Bags have been under development for many years. They were
initially used and designed to be used in fighter planes during world war
second. In the 1980’s the first commercial air bags appeared in automobiles.
Since 1988, all new cars have been required to have air bags on both driver

2. AIRBAGS SYSTEM

Manav School Of Engg Page 2

and passenger sides. To date, Statistics show that air bags reduce the risk of
dying in a direct frontal crash by 30 present. Other than steering Wheel
mounted or Dash board mounted bags, there are seat-mounted and door
mounted side air-bags. Air bags were invented as the result of serious
government discussions and industry research and tests.

3. AIRBAGS SYSTEM

Manav School Of Engg Page 3

CHAPTER 2

LITERATURE REVIEW


2.1 OVERVIEW

Airbags are considered as passive device because no action by the
vehicle occupant is required to activate or use the airbag This is in contrast to
seat belts, which are considered active devices because the vehicle occupant
must act to enable them. Note that this is not related to active and passive
safety, which are, respectively, systems designed to prevent accidents in the
first place and systems designed to minimize accidents once they occur. For
example, the car's Anti-lock Braking System will qualify as an active-safety
device while both its seatbelts and airbags will qualify as passive-safety, which
are, respectively, systems designed to prevent accidents in the first place and
systems designed to minimize accidents once they occur. For example, the
car's Anti-lock Braking System will qualify as an active-safety device while
both its seatbelts and airbags will qualify as passive-safety devices. Further
terminological confusion can arise from the fact that passive devices and
systems those requiring no input or action by the vehicle occupant can
themselves operate in an active manner; an airbag is one such device. Vehicle
safety professionals are generally careful in their use of language to avoid this
sort of confusion, though advertising principles sometimes prevent such
syntactic caution in the consumer marketing of safety features. Various
manufacturers have over time used different terms for airbags. General Motors'
first bags, in the 1970s, were marketed as the Air Cushion Restraint System.
Common terms in North America include Supplemental Restraint System and
Supplemental Inflatable Restraint, these terms reflect the airbag system's
nominal role as a supplement to active restraints, i.e., seat belts.

4. AIRBAGS SYSTEM

Manav School Of Engg Page 4


2.2 HISTORY
The first concepts for an automatically inflating air cushion used as an impact
protection for car passengers were discussed in the sixties, approximately 10
years after corresponding patents had been granted . John HETRICK'S patent
describes a general airbag system in which a self-opening airbag is
automatically inflated following a sudden deceleration of the vehicle. In the
USA ordinances FMVSS 208 was passed in the middle of the sixties against
the background of increasing numbers of accidents, to improve vehicle safety,
thereby it called Safety Act. A bundle of new ordinances were planned to
improve safety in traffic. It was not until 1984, following long and
controversial discussions, that an agreement could be reached on the
introduction of a passive restraint system on September 1, 1989 for all new
vehicles registered in the USA. These automatic restraint systems could be
automatically closing seat belts or the airbag. In order to be able to comply
with the new ordinances (FMVSS 208) immediately after they come into
force, airbag developments were also initiated and intensified by European
automobile manufacturers; primarily by Mercedes-Benz. The basic
development of passive restraint systems stepped up at Mercedes-Benz from
1967 onwards. This first development stage from 1967 to 1972 is referred to as
the principle functional proof. However, General Motors has also introduced
its first airbags in the early 1970s but consumer did not readily accept them.
The market for airbag was assured by US when the Department of
Transportation (DOT) implemented the Federal Motor Vehicle Safety
Standards (FMVSS) 208inch 1984 as mention above. Because of this law, the
US leads the commercialization of airbag. The airbags of initial phase were
inflated using compressed-gas canisters. However, the pressure canisters could
only be accommodated in the instrument panel. Connection to the steering
wheel proved problematic since it could only be sealed with great difficultly.

5. AIRBAGS SYSTEM

Manav School Of Engg Page 5

In the next development phase experiments were carried out with liquefied gas
and solid fuels. The solid propellant should supply the thermal energy needed
to expand the liquid Fringe. . The airbags of initial phase were inflated using
compressed-gas canisters. Although the necessary inflation time of 1/30
second was reached this system was still too heavy. A neoprene-coated
polyamide fabric was initially determined as a suitable material for the airbag.

After 1970, research concentrated on an inflator filled with solid fuel to
inflate the airbag. Together with development partners from the chemicals and
automotive industries, this method of producing the gas was perfected for
series production as of 1974. In December 1980, the first vehicle with a driver
airbag was launched by Mercedes Benz. Seat belt tensioned were also offered
for the driver and front seat passenger. As of 1988 front-seat passengers were
also protected by an airbag. Since the beginning of the nineties, all automobile
manufacturers have been offering airbags as a standard feature or optional
extra, even in compact class cars. . The airbags of initial phase were inflated
using compressed-gas canisters. However, the world-wide use of the airbag
system didn't proceed harmoniously since on the US-American market it is
specified as the only restraint system (passive system) whereas in Europe it has
been developed as an additional safety device (SRS: Supplemental Restraint
System) to the seat belt system. . The airbags of initial phase were inflated
using compressed-gas canisters. These different developments have affected
the size of the airbag and inflator. As a sole passenger protection system the
airbags must be much bigger and must inflate earlier since the unprotected
passenger collides faster with the instrument panel. The number of persons,
driver and passenger killed in traffic has dropped continuously since 1970.

6. AIRBAGS SYSTEM

Manav School Of Engg Page 6

Table no: 2.1 Showing the same statistics for belted, non-belted and over all






















As a result of which in fig no:2.1 air bag penetration in the market has also get
hiked from 1999 to 2005 . Airbag growth has also increased accordingly in
every region of the vehicle with the stringent demand of the safety






















Fig no: 2.1 Statistics for Airbag Application in Vehicles

.Thus development of Federal rules, increased public awareness for safety and
concern for safety has enhanced the growth of air bags in the market as shown
in fig no:2.2

7. AIRBAGS SYSTEM

Manav School Of Engg Page 7


2.3 CHEMISTRY OF AIRBAGS


Inside the airbag in fig no:2.3 is a gas generator containing a mixture of
NaN3, KNO3, and SiO2. When the car undergoes a head-on collision, a series
of three chemical reactions inside the gas generator produce gas (N2) to fill the
airbag and convert NaN3, which is highly toxic, to harmless glass. Sodium
azide (NaN3) can decompose at 300
o
C to produce sodium metal (Na) and
nitrogen gas (N2). The signal from the deceleration sensor ignites the gas-
generator mixture by an electrical impulse, creating the high-temperature
condition necessary for NaN3 to decompose. The nitrogen gas that is
generated then fills the airbag. The purpose of the


























Fig no: 2.3 Chemicals inside the airbags

KNO3 and SiO2 is to remove the sodium metal (which is highly reactive and
potentially explosive, by converting it to a harmless material. First, the sodium
reacts with potassium nitrate (KNO3) to produce potassium oxide (K2O),
sodium oxide (Na2O), and additional N2 gas. The N2 generated in this second
reaction also fills the airbag, and the metal oxides react with silicon dioxide
(SiO2) in a final reaction to produce silicate glass, which is harmless and

8. AIRBAGS SYSTEM

Manav School Of Engg Page 8

stable. (First-period metal oxides, such as Na2O and K2O, are highly reactive,
so it would be unsafe to allow them to be the end product of the airbag
detonation.)



Reaction 1 2NaN3

2Na + 3N2

Reaction 2
10Na +
2KNO3 K2O + 5Na2O + N2

Reaction 3
K2O + Na2O
+ SiO2

Na2K2SiO4 (alkaline silicate
glass)

9. AIRBAGS SYSTEM

Manav School Of Engg Page 9

CHAPTER 3

MAIN PARTS


The air bag system consists of three basic parts- an air bag module, crash
sensor and a diagnosis unit.

Some systems have ON/OFF switch to deactivate air bag system.




















Fig no: 3.1 ON/OFF switch of air bag system

10. AIRBAGS SYSTEM

Manav School Of Engg Page 10

3.1 AIRBAG MODULE

The air bag module fig no:3.1 contains both an inflator unit and the
lightweight fabric air bag. The driver air bag module is located in the steering
wheel hub, and the passenger air bag module is located in the instrument
panel. When fully inflated, the driver air bag is approximately the diameter of
a large beach ball. The passenger air bag can be two or three times larger since
the distance between the right-front passenger and the instrumental panel is
much larger than the distance between the driver and steering wheel

3.2 Air bag production process


Typical manufacturing line for air bag has been shown fig no:3.2.
Airbags can be manufactured by either of the mechanisms of fabric
manufacturing, weaving and non- woven fabric manufacturing process














Fig no: 3.2 Air bag fabric productions flow-chart

11. AIRBAGS SYSTEM

Manav School Of Engg Page 11

3.3 Raw materials used in air bag

Mostly used raw material as shown in table no:3.1 for the airbag fabric
is nylon 6, 6 yarns in the deniers ranging from 420 to 840. The side impact
airbags used 1880 D nylon- 6.6 .

Table no: 3.3 Properties of these commercially used fabrics












Table shows the important properties of these commercially used fabrics. They
are generally woven, with the construction of either 840 X 840 D, 98 X 98 /dm
plain weave, 60 width or 420 X 420 D, 193 X 193 /dm plain weave, 60 width
Usually Rapier with insertion rate of 400 m/min has been found most suitable
for weaving airbags. Since, it can maintain warp tension with accuracy of 1
can per war-p12-14. Even water jet and air jet with insertion rate of 600 m/min
are being used15. Commonly, the airbag made were coated by neoprene, but
recently silicon coated and uncoated varieties have become popular. Coated
airbag are generally preferred for driver seats. The weight per unit length
uncoated one is higher than coated bags, i.e. 244 - 257 Vs 175 g/m2. Today,
the latest research on potential airbag materials includes High tenacity
polyester, Nylon 4, 6, etc. apart from Nylon 6, 6. However Nylon 6, 6 has the
most superior quality in all. Air bag fabric has to keep a balance between two
extreme conditions . It has to be sufficiently flexible to fold into relatively

12. AIRBAGS SYSTEM

Manav School Of Engg Page 12

small volumes. At the same time it should be sufficiently strong to withstand
the deployment at high speed, e.g. under the influence of an explosive charge
and the impact of passengers or other influences when inflated. To play this
role successfully airbag fabric should possess following quality parameters

Small fabric thickness.



Low specific fabric weight.



High tenacity in warp and weft direction as well as toughness.



High tenacity for furthers tearing



High elongation.



Good resistance to aging.



Heat resistance up to 190 0C.



Good resistance to UV light.



Low and very even air permeability.



Reduced cost.



Precisely controlled gas permeability.



Excellent seam integrity.



Improved pliability and pack height



Reduced value or burn through resistance.



3.4 SENSORS

The crash sensors are located either in the front of the vehicle and/or in the
passenger compartment. Vehicle can have one or more crash sensors. The
sensors are activated by forces generated in significant frontal or near-frontal
crashes only and not during sudden braking or while driving on rough or
uneven pavement. By function, there are 2 types. Impact sensors and Sating
sensors. The forward sensors are located

in various locations forward of the passenger compartment. Some are located
inside the fenders, some are on the cowl, some are attached to the core support
in front of the radiator. Rear sensors are also known as sating sensors as their
function is to determine that a crash has occurred. Rear sating sensors are

13. AIRBAGS SYSTEM

Manav School Of Engg Page 13

located in various locations in the passenger compartment depending on the
manufacturer. Some are integrated with the Control/Diagnostic Module. The
rear sating sensor must close before the forward sensors to avoid airbag
deployment in cases where the impact is not severe enough to cause
deployment. When the vehicle is parked with the ignition off deployment is
very unlikely because there is no power to the circuits for deployment. Airbag
impact sensors, sometimes colloquially called crash sensors, are important
safety features for your vehicle. These sensors, located throughout your
vehicle, detect a collision and trigger the airbags to go off. They are usually
found at the front of the vehicle, behind the front fender, to detect a frontal
impact, and in the side columns to detect a side impact. The exact number and
location of airbag sensors you have will vary from one model to another, but
those are the most frequently used locations.

3.5 Mass type sensor

An impact sensor in fig no:3.3 is normally fitted to the front of the
vehicle as this is where a collision is likely to occur. The sensor is positioned
inside the engine and a similar safety sensor is located inside the passenger
zone to the vehicle. This safety sensor is required to measure the intensity of
the collision to determine whether the impact is over a certain threshold to
justify release of an airbag. Both types of sensors (termed inertia sensors) work
on the principle of detecting a decrease in acceleration of a moving vehicle and
generate an electrical impulse. Figure is a schematic diagram of an inertial
sensor

14. AIRBAGS SYSTEM

Manav School Of Engg Page 14












Fig no: 3.5 Mass type sensor


3.6 Roller-type sensor

The roller-type sensor in fig no:3.4 involves a weight connected to a coil
spring component. Like the mass-type sensor, during impact with an oncoming
vehicle, the metal weight is forced forward which alters the tension on the coil
spring to manipulate the electrical circuit that closes off the sensor contact. It is
important to note that the impact and safety sensors must activate and close off
at the same time to allow for deployment of the airbag











Fig no: 3.6 Roller-type sensor

15. AIRBAGS SYSTEM

Manav School Of Engg Page 15

3.7 AIRBAG CONTROL UNIT


















Fig no: 3.7 Airbag control unit

The ECU in fig no: 3.5 is the main controlling unit or the brain of the
entire passenger safety system. The ECU not only sends the firing signal to all
the air bags, but in the case of a smart air bag system, it controls the force at
which some of those air bags are deployed. These control units are part of
more advanced smart system that can sense whether the front passenger seat is
empty, and if so, will keep the passenger air bag from deploying. The ECU
also sends the signal to seat belt pretension devices and the rollover protection
bars in convertibles. The control unit is constantly receiving sensory input
from sensors mounted around the vehicle and makes the necessary calculations
to allow it to deploy the appropriate safety systems. The ECU is typically
mounted in the centre of the vehicle in an area that provides the best
protection. Some of the first generation units had capacitors that could take
approximately 20 – 30 minutes for the power to drain after the 12 volt battery

16. AIRBAGS SYSTEM

Manav School Of Engg Page 16

was disconnected. Today’s vehicles, however, have capacitors that drain
within seconds. Care must still be taken, however, during extrication
operations to ensure that the ECU is not damaged; this could inadvertently
cause the ECU to deploy an air bag. An even more advanced system senses the
weight of the front seat passenger and can either deploy the air bag with more
or less force, depending on the passenger’s weight. One of the later
amendments to the Federal Motor Vehicle Safety Standard 208 requires that
all vehicles manufactured after 2007 are required to be equipped with this type
of system. The purpose of this type of system is to perform one of two
functions, depending on the vehicle: keep the front passenger air bag from
deploying if unoccupied, or sense the weight of the occupant in the front seat
and deploy the air bag with less force if the passenger is smaller or with
greater force for a larger person. Some systems are very simple and only sense
the presence of a person on the seat, others can differentiate between a child,
small adult or large adult. This type of system, called an Occupant
Classification System or smart system, uses sensors in the seat along with dual
stage or de-powered frontal air bags. This smart system can also sense the
severity of the crash using accelerometers, wheel speed indicators, brake
pressure sensors and impact sensors in the vehicles to deploy the air bags with
the appropriate force. Dual stage air bags are equipped two individual inflator
units that can be deployed individually or both at the same time. If the ECU
determines that the occupant is a heavier person or that the crash meets the
criteria for a severe crash, both inflator units will fire. If the occupant is a
smaller person or the crash is less severe, it only ignites one of the inflator
units, leaving the second inflator unit un-deployed and loaded.

The danger with this type of system is that if only one of the frontal air bag
inflator units has been deployed, rescuers can falsely assume that that both air
bags are no longer a threat. The fact is, we can have an inflator that is still

17. AIRBAGS SYSTEM

Manav School Of Engg Page 17

loaded and ready to deploy the air bag. The typical extrication scenario has one
of the two front seats empty. A rescuer, seeing a deployed air bag, thinks that
the vehicle is safe and enters the vehicle. The rescuer then places his or her
knee on the unoccupied seat. Now the ECU senses the rescuer’s weight and
arms the second un-deployed inflator. The air bag, even though it has already
deployed, is now ready to deploy for a second time into the unsuspecting
rescuer. For this reason, it is especially important to disable the entire system
by disconnecting the 12 volt battery. Even if rescuers are able to disable the
system, we must make every effort to keep ourselves and any patients out of
all air bag deployment zones.
Upon signal of a collision, the controller interprets the electrical input and
measures the level of collision to determine release of an airbag. In the event
of one impact sensor and safety sensor being closed, an electrical current is
transmitted to an airbag module which contains the airbag and inflator
assembly. Activation of the airbag results in an ignition that produces an
electrical transmission between a pair of metal pins. The electrical arc created
between both pins activates a propellant (made up of sodium azide) that
starts to burn and give off nitrogen gas, and it is this gas that starts to fill the
airbag. The Volvo V40 model takes airbag technology to a new level by
deploying a pedestrian airbag upon impact on the bumper to this car. Similar
airbag control units currently on the market include a model introduced by
TRW. This integrated control module detects vehicle impact by using an
occupant dynamic-based algorithm, which meets all North American and
European regulations with a rollover sensor adapting a functional system
similar to the type discussed in this article. The idea of an integrated airbag
control unit has many advantages:

18. AIRBAGS SYSTEM

Manav School Of Engg Page 18


 Increased sensitivity of the moving vehicle by placing the
integrated control module in the vehicle’s centre of gravity

 Integrated crash sensors diversifies the diagnostics on a collision

 Increased precision of the integrated sensor technology to allow for
better safety

 Cost-effective if all crash sensor systems are integrated into one module.

19. AIRBAGS SYSTEM

Manav School Of Engg Page 19

CHAPTER 4

WORKING


The first stage of the airbag deployment is the accident itself. The
collision, be it frontal or lateral, activates an array of sensors in the vehicle,
including accelerometers, impact sensors, side pressure sensors, brake pressure
sensors, and seat occupancy sensors. All these sensors are in intimate
connection with the ACU (Airbag Control Unit). The unit decides if and how
to deploy the airbags. When the ACU detects that the deployment threshold
has been reached, it initiates the inflation stage. As the compressed air system
would have been impractical and quite inefficient, engineers came up with an
idea quite similar to the working principle of the solid rocket booster.
Each airbag incorporates a pyrotechnic device, known as an initiator or
electric match, consisting of an electrical conductor cocooned in combustible
material. A current pulse heats up the conductor, which in turn ignites the
combustible material. This igniter triggers the chemical reaction that actually
fills the nylon fabric airbag with gas. The large volume of gas then forces the
airbag out of the steering wheel and/or dashboard at a speed of up to 200 mph
or 322 mph, the whole process taking about 0.04 seconds. Considering that the
blink of an eye is approximated at 0.2 seconds, one could say it's quite a
speedy process The last stage of the airbag process is the deflation, which
occurs almost immediately after the inflation is completed. The gas escapes
through special vents. They also prevent the occupants from suffering major
impact injuries. Another effect of the deflation is the release of dust-like
particles, mostly cornstarch and talcum powder that are used to lubricate the
airbag. Small amount of Sodium hydroxide may initially be present. This
chemical can cause minor irritation to the eyes and/or open wounds; however,
with exposure to air, it quickly turns into Sodium bicarbonate (common baking

20. AIRBAGS SYSTEM

Manav School Of Engg Page 20

soda). Depending on the type of air bag system, potassium chloride (a table
salt substitute) may also be present. Initially, the chemicals used in airbags
were a major health concern, but present systems will only produce a mild
irritation of the throat and eyes for most people, as an outcome of dust
released. Generally, these minor irritations continue up to the time occupant
remains in the vehicle with the windows closed and no ventilation. Once
deployed, the air bag cannot be reused and should be replaced by an authorized
service department.

21. AIRBAGS SYSTEM

Manav School Of Engg Page 21


CHAPTER 5

AIRBAG TYPES


With each new generation of vehicles coming out on the market,
rescuers are finding that these vehicles are being equipped with more airbags.
All of these air bags are designed with a specific purpose and function but
when used in conjunction with the other safety systems, increase the
survivability of all occupants involved in a vehicle accident. In this section, we
will discuss the different types of air bags, the intended function and the
danger that they present to rescuers.

5.1 FRONTAL AIR BAGS












Fig no: 5.1 Driver side airbag

These are the most prevalent and familiar air bags on vehicles. Fig no:5.1
shows Driver side airbag This is the only type of air bag that is on every
vehicle that is equipped with air bags. There may not be a head curtain air bag
or side impact bags, but if the vehicle has air bags, it will be equipped with
frontal air bags. The purpose of the frontal air bag is to prevent any front seat

22. AIRBAGS SYSTEM

Manav School Of Engg Page 22

occupant from impacting the steering wheel or dash board in the event of a
frontal collision. The first version of the frontal air bag was a single stage air
bag with only one firing unit. It provided an added measure of safety for all
passengers but created a hazardous situation for shorter drivers. In order for
the frontal air bag to be effective, it has to have enough room to fully deploy
prior to the driver impacting the bag. This ensured that the air bag’s
deployment energy was completely dissipated before the patient came into
contact with the airbag. Obviously, a shorter driver has to move the driver’s
seat closer to the steering wheel in order to drive. This proved to be very
dangerous and sometimes fatal. The driver usually made contact with an air
bag prior to complete deployment and absorbed a lot of the energy. This is the
point where injuries and fatalities occurred, usually due to brain damage or
fractured cervical vertebrae. Another danger with first generation frontal air
bags is that they were extremely unreliable. That, coupled with the fact that
some did not have any labelling or identification gave Resc-uses the idea that
these airbags were not present. If the 12 volt battery was not disconnected, the
system remained armed. To combat these hazards, an amendment to FMVSS
208 mandated that vehicles manufactured in 2007 and later be equipped with
an Occupant Classification System to work in conjunction with dual stage or
de-powered frontal air bags, as discussed before in the Electrical Control Unit
section. Some older model vehicles were equipped with this system long
before the standard dictated. These air bags, however, are difficult if not
impossible to differentiate from single stage air bags. The rescuer will not
know whether the deployed frontal air bag is a single or dual stage type. The
following pictures illustrate some frontal airbags. Here we have a typical un-
deployed steering wheel mounted single stage frontal air bag.

23. AIRBAGS SYSTEM

Manav School Of Engg Page 23











Fig no: 5.2 shows the deployed first stage of a air bag

5.2 HEAD PROTECTION BAGS

One of the first types of head protection to be introduced in the US was
the (HPS) Head Protection System in the 1998 BMW, also known as the (ITS)
Inflatable Tubular Structure. These are much different than the curtain airbags
we see in most vehicles. This tube is anchored at the pressurized cylinder that
is mounted on the lower portion of the post and at the rear to the roof rail
behind the post, allowing it to deploy diagonally across the window opening.
The bag is stored inside the trim of the post, along the headliner trim over each
door. When un-deployed, the only identifying markings are the letters 'HPS'
embedded in the trim cover at the top of the posts. Unlike other airbags, the
tubular bag consists of a specifically designed material that is woven in a
pattern that expands as the bag deploys to form an airtight tube. Also unlike
most airbags, the tube does not deflate; there are no vent holes that allow the
gas to escape. The tube will actually remain inflated for hours after the
collision. The tube remains firmly inflated to offer head protection from
rebound forces, which are common in side impacts and rollovers. Once the
door is opened, rescuers can safely puncture the tube and cut the mounting
strap at the post to get the bag out of their way. The bag is approximately 38

24. AIRBAGS SYSTEM

Manav School Of Engg Page 24

inches long and 5 inches in diameter when inflated. Nylon web straps are sewn
into each end of the bag to attach it to the vehicle.









Fig 5.3 Head protection airbags

All side impact airbags these cannot deploy a second time. If the tube is not
deployed rescuers must not only stay out of the deployment zone of the tube,
but the whole door area. These tubes are always used in conjunction with a
torso type door or seat mounted airbag. The gas inflator is located at the front
end of the system. The canister which is filled with nitrogen, argon or other
inert gas is mounted in the dash at the lower pillar area. These systems will
deploy if the sensor experiences an impact of about 12 mph or above. As
stated before the cylinder of a tube can always be found in the lower portion of
the post. This location is in close proximity to where we will make relief cuts
for the different dash displacement evolutions. It is imperative that we make
sure to peel all the plastic from this area to ensure that we do not cut through
these cylinders.

5.3 Side curtain airbags

The two most commonly used curtain airbags are the front window type
and the full length type. The front window curtain usually extends from the

25. AIRBAGS SYSTEM

Manav School Of Engg Page 25

post to post and extends down from the roof to about the top of the door panel
.The full length curtain usually extends from just behind the A post to post and
extends from the roof to the top of the door panel also. Like the head
protection tube, both of these are hidden behind the trim panels and head liner,
when undeployed they can only be detected by small emblems embedded in
the trim panels. Rescuers must be aware that these emblems only indicate the
presence of a head curtain bag, not the location. These bags are deployed by
small stored gas inflators that can be located at the front, centre, rear, or
anywhere along the support system. They are found in the post, along the roof
rails, in the posts and some even over the rear glass. It is extremely important
that these inflators be visually located before any extrication procedures begin.
Unlike the solid propellant gas canister built into the passenger’s frontal
airbag, these inflators have no protection around them; they are simply a long
thin tube that is filled with a compressed inert gas.









Fig no: 5.3 Side curtain airbags

Some vehicles, such as the Volvo XC90, Infinity QSX, Nissan Pathfinder,
Armada and Quest minivan, and Ford Excursion have head curtains in two
sections, requiring two cylinders to deploy the curtain. Again, it becomes

26. AIRBAGS SYSTEM

Manav School Of Engg Page 26

extremely important to expose as much of the plastic as possible prior to
beginning any evolutions.

5.4 SIDE IMPACT AIRBAGS








Fig no: 5.4 Side impact airbags

Side impact air bags fig no:5.5 are designed to protect a passenger’s
head and thorax with some style of bags or just the thorax with another type of
bag. Some of these bags are designed to help keep an occupant from being
ejected from a vehicle in a roll over. Like the frontal airbags; side impact
airbags must have a crash sensor to recognize that a crash has occurred. These
sensors are usually mounted in the front door, the post, or most are located
inside the rocker panel just below the post.
The cylinders for these bags can be mounted in the post and also underneath
the folded air bag in the seat back. Some older vehicles used the same
chemical propellant, sodium aside, used in frontal air bags. The air bags can be
mounted in one of two locations: the door or the out board side of the seat
back. The door mounted bags can either mounted on the inside of the door and
deploy from a blow out panel. Some newer door mounted bags pop up, like a
toaster, from the top of the door. The 2010 Volvo C70c1920c on vertible has

27. AIRBAGS SYSTEM

Manav School Of Engg Page 27

an air bag that extends the entire length of the passenger compartment, from
the post to the rear of the passenger compartment

5.5 OCCUPANT POSITIONING AIR BAGS

Occupant positioning air bags are different bags placed throughout the
vehicle that work together, along with the seat belt and pretension, and have
the sole purpose of keeping front seat occupants from sliding out of the seat in
a front end collision. In this type of collision, a person in the front seat usually
slides out of their seat and is thrown under the dash if this system is not in
place. This is known as submarine and usually meant significant injury or
death to the occupant. Some vehicles may have some or all of these types of
bags and some vehicles may not be equipped with any at all. All of these bags
present their own unique dangers that we will now discuss.

5.6 Knee bags or bolsters

These bags fig no:5.6 deploy exactly where their name suggests. They are
usually placed under the steering column and under the passenger side dash
board. They function not only as part of the Occupant Positioning System, they
also reduce the severe knee and hip injuries that normally occur During a front
end collision.
These bags, as well as the others we will discuss, work in conjunction to keep
the occupant in their seat. There are two basic types of bags: the knee bag and
the knee bolster. Both serve the same purpose. The knee bag is just a simple
air bag that deploys outward from the dash toward the front edge of the seat.
propellants (sodium-acid) as the frontal air bags and are usually identified on
the blow out panel. The picture shows an identification stamp. On the right is a
picture of a deployed knee bag.

28. AIRBAGS SYSTEM

Manav School Of Engg Page 28

CHAPTER 6

AIRBAG RISKS



6.1 AIR BAG CONTACT INJURIES


Air bags must inflate very rapidly to be effective, and therefore come
out of the steering wheel hub or instrumental panel with considerable force,
generally at a speed over 100 mph. Due to this very high initial force, contact
with a deploying air bag may cause injury. Properly restraint occupant along
with applied due seat belt receives very minor abrasion or burns. However,
very serious or fatal injuries can occur when someone is very close to, or in
direct contact with an air bag module when the air bag deploys. Even never
attach objects to an air bag module or place loose objects on or near an air bag
module, since they can be propelled with great force by a deploying air bag,
potentially cause serious or fatal injuries. Thus safety restraint system must be
utilized with due care and regulation to get best results. An unrestrained or
improperly restraint occupant can be seriously injured or killed by a deploying
air bag. The National Highway Traffic Safety Administration (NHTSA)
recommended certain rules for the safety of occupant and passengers. They are
as follows:
 Never put a rear-facing infant restraint in the front seat of a vehicle with
a front passenger air bag.

 Children of age 12 and under should be properly restrained in a rear
seat.
 
 Driver should sit with at least 10 inches between the centre of their chest
bone and the steering wheel.

 Always apply seat belt, it retain occupant and passenger rightly
positioned and minimizes risk of serious injuries.


29. AIRBAGS SYSTEM

Manav School Of Engg Page 29

CHAPTER 7

CONCLUSION

The air bags are of greater importance in today’s vehicles since safety of
human life is of prior importance. Since the count of automobiles is increasing
tremendously on our roads, the probability of accidents is also more. So far a
safe riding and for saving the precious life the safety bags must be
implemented. Today it is the privilege of the high class people who own high
priced cars. Let’s hope every automobile manufacturer implement the same
since safety for life is inevitable. The number of persons killed or injured in
traffic has dropped continuously since the development of air bag system.
Over the time, the development of seat belt becomes an indisputable matter of
course. Today, the 3-point automatic seat belt, seat belt tensioner and airbag
constitute a carefully matched passenger protection system. Implementation of
these safety restraint systems with due care and regulation can further drop the
fatality rate and serious injuries at the time of road accidents





30. AIRBAGS SYSTEM

Manav School Of Engg Page 30

REFERANCE

[1] Panchal. M, Dayaramani. A ,Project done by DKTE students,2004,
online launched on, http://www.textilepapers.tripod.com , vol 3.

[2] Goltner .W , Fabric for airbag US5236775 A patent published in
Aug 17,Gogle patent , 1993 ,vol 1
[3] Khan. M. S, project done by DTE students, Textile 2001
learnerAir-bag for automobiles,
http://www.textilelearner.blogspot.com , vol 1

[4] Dupont , Sun. J, Barnes J. A, Airbag End-Use Technology,1999,
Marerial selection for Air-bags , vol 7
[5] C. Bastien, M. V. Blundell, D. Stubbs, J. Christensen, J.
Hoffmann, M. Reisinger, R. Van Der Made, , Correlation of Airbag
Fabric Material Mechanical Failure Characteristic for Out of Position
Applications, 2010, proceedings of isma 2010 including usd vol 1