A Critical Review of Polymer-based

EngineeringComposite
ReviewAutomotive Bumper Systems

A Critical Review of Polymer-based Composite

Automotive Bumper Systems

S.M. Sapuan1*, N. Suddin1 and M. A. Maleque2

1
Department of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia,
43400 Serdang, Selangor, Malaysia
2
Department of Mechanical and Materials Engineering, University of Malaya,
50603 Kuala Lumpur, Malaysia

Received: 15th April 2002; Accepted: 10th July 2002

SUMMARY
An automobile bumper is a structural component, which contributes to vehicle
crashworthiness or occupant protection during front or rear collisions. The bumper
systems also protect the hood, trunk, fuel, exhaust and cooling system as well as safety
related equipments. A brief description of bumper components and a critical review of
polymer-based bumper systems with specific methodology are provided. This article
advocates proper bumper design and material selection. The authors also discuss bumper
components from the standpoint of the materials and their manufacturing processes.

1. INTRODUCTION Bumper systems have been changing drastically

over the last 20 to 30 years. More demanding
The aim of this article is to provide information about government safety regulations and different styling
scientific bumper systems and components and to concepts have resulted in new designs. For example,
offer a critical review of bumper materials. The
reinforcing beams covered by plastics fascias were
advantages and disadvantages of polymer-based
introduced in the early 1970’s. Styling fashion has
composite materials compared with traditional steel
changed and instead of almost 100% chrome-plated
materials are also discussed. A bumper is a shield,
face bars we have predominantly fascia system that
normally made of aluminium, steel, rubber, composite
are colour coordinated with the body. The growth of
or plastics and mounted on the front and rear of a
light trucks, minivans and sports utility vehicles has
vehicle. In some bumpers energy absorbers or brackets
created two classes of bumper systems in the eyes of
are used and others are made with foam cushioning
material. The car bumper is designed to absorb energy the engineering world: one for passenger cars and
and thus prevent or reduce physical damage to the another for light trucks. Safety concerns have resulted
front and rear ends of an automobile in low speed in the bumper beam becoming a part of the structural
collisions. Automobile bumpers are not usually load path2.
designed to be structural components that would
significantly contribute to vehicle crashworthiness There are several factors to be considered when
or occupant protection during front or rear collisions selecting a bumper system. The most important
at higher speeds. The bumper should be designed as consideration is the ability of the bumper system to
a safety feature, since it is intended to reduce the absorb enough energy to meet the original equipment
magnitude of deceleration during impact. The bumper manufacturers (OEM’s) internal bumper standard1.
systems are only designed to protect the hood, trunk, Another is the requirement to stay intact in high-
frame, fuel, exhaust and cooling system as well as speed impacts. Weight, manufacturing process-
safety related equipment, such as parking lights, ability and cost are also factors that have to be
headlamps and tail-lights in low speed collisions. considered during the design phase. Both initial
bumper cost and repair cost are important. The
formability of materials is important for high-sweep
* author to whom correspondence should be addressed bumper systems. Another factor considered at the

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 S.M. Sapuan, N. Suddin and M. A. Maleque

materials selection stage is recyclability, which is an 2.1 Metal Face Bar System
advantage for steel but yet the evolution of CO2
during recycling or re-melting of steel has to be A metal face bar system consists of a single metallic
taken into consideration. bumper that decorates the front or rear end of a
vehicle and acts as the primary energy absorber in
a collision. The bumper regulations in the United
2. A BRIEF DESCRIPTION OF BUMPER States require passenger cars to withstand a 4 km/
SYSTEMS AND COMPONENTS1 h impact at the curb position plus or minus 50 mm
There are four types of bumper systems commonly with no visual damage and no damage to safety
used in vehicles, as shown in Figure 1. A brief related items. The Canadian passenger car
description of each system is given below. regulations call for a 8 km/h impact, however
limited damage is permitted. The North American
OEMs voluntarily design their passenger car
Figure 1. Four different types of automotive bumper bumpers to withstand a 8 km/h impact with no
systems: a) Metal face bar system, b) Plastics fascia visual damage and no damage to safety items.
and reinforcing beam system, c) and d) Plastics
Current face bar systems can only withstand a 4
fascia, reinforcing beam and energy absorbers1.
km/h impact at the curb position plus or minus 50
mm with no visual damage and no damage to safety
items. For this reason, the use of current face bar
systems is restricted to light trucks. The aesthetics
of face bars matches the styling trend for full size
vans, pickups and sports utilities. Thus, most face
bars are presently being applied to these vehicles.

If the design standard for light truck bumpers were

to be raised to the 8 km/h voluntary passenger car
standard, then the face bar systems used on full size
vans, pickups and sport utilities would have to be
redesigned. For reasons of weight, such redesigns
would probably revert to systems that employ a
reinforcing beam1.

2.2 Plastics Fascia and Reinforcing

Beam System
This system consists of a plastics fascia and a
reinforcing beam, which is fastened directly to the
vehicle frame or motor compartment rails (Figure
1b). It is used primarily in Europe and Japan, where
bumper regulations are less stringent than those in
North America. On many vehicles in Europe and
Japan, the reinforcing beam in this system also
serves as the first structural cross-member. While
this arrangement leads to a small sacrifice in bumper
performance, it increases vehicle crashworthiness.
If the reinforcing beam is a part of the body-in-
white, the favoured material is steel because of the
structural requirements associated with a cross-
member. Also, steel is fully compatible with the
body in white E- coat and paint systems used by the
OEM’s plastics fascia, reinforcing beam and energy
absorption system.

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 A Critical Review of Polymer-based Composite Automotive Bumper Systems

2.3 Plastics Fascia, Reinforcing Beam and entering the engine compartment. It should be
Mechanical Energy Absorber System aesthetically pleasing to the consumer. A typical
fascia (as shown in Figure 3) is styled with many
Bumper systems with a plastics fascia, reinforcing curves and ridges to give the bumper dimension and
beam and energy absorption are shown in Figures 1c to distinguish vehicles from competing models.
and d. These readily meet the 8 km/h voluntary Another requirement of a bumper fascia is easy
bumper standard set by the North American OEMs. fabrication. It is also important for it to be light in
All passenger cars and most minivans around the weight. Virtually every fascia is made from one of
world have this type of system, with small variations three materials: polypropylene, polyurethane or
in the method of energy absorption. Energy can be polycarbonate1.
absorbed by a mechanical absorber (Figure 1c), foam
or honeycomb (Figure 1d), or by the reinforcing
beam itself1. 2.5 Energy Absorber
An energy absorber is designed to absorb a portion of
A bumper system consists of three components (as the kinetic energy from a vehicle collision. This is
shown in Figure 2), such as fascia, and energy absorber very effective in a low speed impact, where the
and bumper beam. A brief description of the bumper springs back to its original position. In order
to comply with U.S. federal regulations, manufacturers
components is furnished in the following sub-sections.
fit their bumpers with energy absorbers. Generally,
the energy absorber is mounted between the face bar/
2.4 Fascia bumper reinforcement and the frame.
A bumper fascia is designed to meet several
requirements. It must be aerodynamic to control the There are three types of energy absorbers. The most
flow of air around the car, and the amount of air common is similar to a shock absorber. The typical

Figure 2. Automotive bumper system components

Figure 3. Front view of a typical fascia

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 S.M. Sapuan, N. Suddin and M. A. Maleque

bumper shock absorber is a cylinder filled with Current bumper systems employ steel to produce
hydraulic fluid. Upon impact, a piston filled with the bumper beam. Steel reinforcing beams are
inert gas is forced into the cylinder. Under pressure, stamped, roll formed or made by the Plannja process
the hydraulic fluid flows into the piston through a (hot stamping process).
small opening. The controlled flow of fluid absorbs
the energy of the impact. Fluid also displaces a
A stamped beam is advantageous in high-volume
floating piston within the piston tube, which
production and offers complex shapes. However, the
compresses the inert gas. When the force of the
stamping process is capital intensive and the process
impact is relieved, the pressure of the compressed gas
itself requires good formability from the steel. The
forces the hydraulic fluid out of the piston. The
Plannja process is a hot stamping process, which
compressed gas forces the hydraulic fluid out of the
results in high-strength beams and is relatively
piston tube and back into the cylinder. This action
expensive because of its low production rate. The
forces the bumper back to its original position. With
sheet steels are continuously fed into a gas fired
another energy absorber design, upon impact, fluid
flows from a reservoir through a metering valve into furnace and heated to austenitizing temperature,
an outer cylinder. When the impact forces are relieved, approximately 900 °C, in about 3 to 5 minutes. Then
a spring in the absorber returns the bumper to its the material is fed into a hydraulic press. The press
original position. cycles down, remaining in that position while the
dies quickly cool the formed sheets until the
temperature is approximately 40 °C, well below the
Another type of energy absorber is found on many martensite finish temperature. The time required to
light motors and sports car. Instead of shock absorbers, cool the parts in the dies is ~ 10 seconds per mm of
foam is mounted between the fascia and the face bar thickness. Roll formed beams account for the majority
or reinforcement bar, where a thick urethane foam of the steel reinforcing beams used today. Common
pad is sandwiched between an impact bar and a cross-sections of roll-formed beams are box, C or
plastics face bar or cover. On some vehicles the channel, and hat shapes. Typically, these cross-
impact bar is attached to the frame with energy- sections are made of ultra high-strength steels with
absorbing bolts. The bolts and brackets are designed very thin gauges. A back plate is sometimes welded
to deform during a collision in order to absorb some to an open channel or hat section to create a box
of the impact force. The brackets must be replaced in section. All the steel reinforcing beams have good
most collision repairs. corrosion resistance. Some are made from hot dip
galvanized or electro galvanized sheet. The zinc
In modern bumper systems a self-restoring elastomeric coating on these products is responsible for the
energy-absorbing unit is used. An elastomeric polymer excellent anti-corrosion properties.
material gives the energy absorber the ability to
deflect and return to its original position when the car 3. MANUFACTURE OF BUMPER SYSTEMS1
strikes a barrier at speeds of up to 8 km/h. The
elastomer is moulded into a hollow cylinder that In 1997, almost 28 million bumper units were supplied
surrounds the sliding central member of the energy to the North American OEMs1. Of these, 76% were
absorber. When the bumper is struck, the elastomeric steel, 17.6% composite and 6.4% aluminium. About
cylinder compresses, then buckles, providing both 1.5 million steel units were reinforcing beams covered
an energy absorbing and an energy-storing effect. by a plastics fascia, about 5.7 million steel units were
After the impact, the energy stored in the elastomeric chrome-plated face bars and the remaining 4.0 million
cylinder returns the unit and the bumper to their steel units were painted face bars. As far as the
original position. manufacturing process is concerned, approximately
60% of the steel units were stamped and 40% roll
formed. In total, about 300,000 tons of steel were
2.6 Bumper Beam consumed in the 1997 model year by the North
The reinforcing bumper beam is a key component of American bumper reinforcing beam and face bar
the bumper system that helps to absorb the kinetic market. In view of the importance of this activity,
energy from a collision and provide protection to government and non-government organizations/
the rest of the vehicle. By staying intact during a bodies should establish a bumper project group who
collision, the beam preserves the frame. Design will prepare technical information bulletins to provide
issues for the reinforcing beam include strength, fundamental background information on automobile
manufacturability, weight, recyclability and cost. bumper systems.

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 A Critical Review of Polymer-based Composite Automotive Bumper Systems

Materials have also changed dramatically. With development, prototype and testing of a front end
emphasis on vehicle performance, especially fuel bumper system assembly using composite materials.
economy, vehicle weight considerations are the first The materials selected for the energy absorber, and
design criteria on automotive engineers’ project lists. for the fascia and beam/support are urethane, using
High-strength and ultra high-strength steels have reaction reinforced injection moulding (RRIM) and
been developed, permitting designers to reduce sheet structural reinforced injection moulding (SRIM)
metal thickness, and hence weight. respectively.

Business management practices have changed. In A composite material bumper system has been made
the past, the vehicle assemblers (OEMs) produced using sheet moulding compound (SMC) with random
most of the bumper systems, with only a handful of chopped glass fibres3. Mechanical properties such as
relatively small independent stampers tensile strength, tensile modulus and hardness were
supplementing the capacity. Now the OEMs are a measured to see whether the performance of the
minor manufacturing players, relying heavily on a material was acceptable. Minaudo et. al.4 developed
growing specialist industry, devoted in some cases a one-piece, injection moulded, thermoplastics rear
to producing nothing but bumper components and bumper system with pole impact protection. The
systems. In fact, most of these independent authors also described the bumper’s design,
manufacturers supply all of the design details and development, and validation process along with the
verification testing. The OEMs supply the big picture results achieved to date. It is the first single piece, rear
requirements, i.e., how the bumper system fits into bumper system injection moulded from an
the overall vehicle appearance, how it will be affixed engineering thermoplastics material and provides 8
to the vehicle, weight limitations, outer boundary km/h pole impact resistance as well as meeting the
size limitations, etc. Federal Motor Vehicles Safety Standard (FMVSS)
protection requirements for a small passenger vehicle.
The bumper offers a 1.5 kg mass saving compared
Bumper systems, like all other automotive
with conventional aluminium and polypropylene.
components, are still subject to constant change. The
shift from face bars to fascia-covered reinforcing
beam systems continues in the light truck area. The The technologies for recycling Reaction Injection
shift back to steel from more costly aluminium and Moulded (RIM) polyurethane polymers have been
composite systems continues, as does the trend to refined to the stage of commercial reality. The process
higher yield strength steel. There is more integration allows the recycling of painted and unpainted process
with fog lamps, headlights, turning lights and grills. scrap, and potentially post customer scrap, for use in
The OEMs are increasingly relying on their bumper the same application without loss of surface quality
suppliers to provide technical innovations. For or polymer performance. This will affect the particle
reasons of cost, lightweight steel is a better choice for size and moisture content, and the effect of painted
bumper systems. Furthermore, even though the market scrap on the polymer performance has to be
is undergoing constant change, steel is strengthening considered. Morgan et. al.8 have discussed the details
its position. Steel’s market share is forecast to increase of the “three streams” RIM process. Although there
from 76.0% in the 1997 model year to 84.2% in the are other alternatives for recycling RIM thermoset
2001 model year. Over this same period, the use of polymer, such as chemolysis and hot compression
aluminum is expected to drop from 6.4% to 1.9% and moulding, the “three streams” RIM regrind process
the use of composites has decreased from 17.6% to holds a potential cost advantage over the other recycle
13.9% tonnage1. route.

4. REVIEW OF POLYMER-BASED Recent demands have led to the development of

COMPOSITE BUMPER SYSTEM lightweight polyurethane elastomers for automotive
fascias. These material can offer the automotive fascia
Current designs of bumper systems employ steel for moulder the advantages of reinforced RIM
the bumper beam. As the function of a bumper system polyurethane elastomer in a very competitive package.
is to absorb kinetic energy during a collision, the use Current refinements developed in filler packages
of composite materials to replace steel has been tried. now allow for the application of reinforced RIM
Considerable effort has been devoted to the systems that exhibit improved surface quality.
development of composite bumper systems2-7. Kelman Moreover, the use of microspheres offers control over
et. al. 2 described research into the design, the shrink and green strength of moulded parts.

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 S.M. Sapuan, N. Suddin and M. A. Maleque

These microspheres may be solid or hollow, rigid or absorbers and explored the potential of this new
flexible, and they range in size from 1 micron to 300 prototype as an alternative to expanded polypropylene
microns. All these systems exhibit processing (E) foam. They reviewed of the simulated performance
characteristic similar to those of established RRIM of a prototype energy absorber and compared its
products, they pass the car performance tests, and actual test result in 8 km/h FMVSS impacts to the
they compete successfully with the best lower cost performance of E foam packaged in the same
fascia material. Hurley et. al.9 reviewed the benefits environment. Kelly and Rucker17 developed and
and deficiencies of these various RIM-Lite filler described a new series of polyurethane foams and
packages. Recommendations are made for the polymers, designed to protect the occupant of a
optimum density reduction and cost savings. This vehicle during a collision. These new energy absorbing
review covers solid and hollow microspheres of both polymers are being developed with a unique chemistry
inorganic and polymeric composition. that yields a semi-rigid thermoformable foam with
enhanced energy absorbing characteristics. This
chemistry when combined with a revolutionary new
Reaction injection moulded polyurethane chemistry
manufacturing process yields a series of urethane
has evolved to provide improved properties and
polymers with unique properties. They concluded
processing while meeting competitive cost pressures.
that new polyurethane polymers offer promise in
The concept of making parts thinner to reduce mass,
providing energy absorbing systems for meeting
and thus costs, has been introduced previously and
FMVSS 201.
has been commercially reduced to practice. Now, the
incorporation of lightweight micro- spheres into RIM
parts has lowered the density of that of thermoplastics Sounik et. al.18 studied the head impact testing of
olefin (TPO), i.e. about 0.92 g/cm3. Meeting performance polyurethane energy absorbing foams. They
requirements with thinner and lighter RIM materials demonstrated the utility and versatility of an in-
while retaining the superior paintability and design house impact tester, which can reliably measure the
flexibility of RIM has now been demonstrated. A new head impact performance of a variety of energy
understanding of polymer performance and continued absorbing materials. They found that polyurethane
development of filler technology have made these foams were very effective for absorbing energy and
unique and effective composites possible. Berg10 has were capable of providing significant head impact
discussed their properties and processing, and the protection. Compared to other energy-management
available field experience. The ability of RIM fascias to materials, polyurethane foams can offer the following
be made both thin and light has been demonstrated by advantages to the OEM: tailorable foam properties -
reducing wall stock and incorporating microspheres. rigid or recoverable, isotropic properties, foam in
Initial evaluation by OEMs indicates that requirements phase capability, a low tendency towards squeaks
for painted appearance, durability, and performance and rattles, and recyclability.
can be met. For these reasons, RIM fascia moulders and
automotive OEMs are facilitating the development
Modern vehicles incorporate deformable energy
and commercialisation of lightweight RIM fascia.
absorber structures within the vehicle structure to
Thermoplastics olefins for automotive bumpers have
manage the collision energy and slow the deceleration,
poor paintability and 1-1-1-trichoroethane-vapour
which in turn can lower the occupant velocity relative
treatment is applied in order to improve the paintability.
to the vehicle. Syrowik et. al.19 described an energy
The 1-1-1-trichoroethane not only degreases, but also
management system based on polyurethane foam,
etches and swells the substrate. Many approaches
designed to improve the crash signature of light–duty
have been developed to modify the TPO surface to
truck and multipurpose passenger vehicles (MPVs).
allow conventional coating materials with stronger
The design and development requirements for this
bonding11, 12. Komatsu et. al.13 has introduced an
system are detailed complete with materials
alternative technology using a TPO modified substrate
evaluation and full scale impact testing. The
with a functional group. Clair14 has developed new
development of polyurethane materials to meet the
coating resins instead of modifying the TPO substrate.
design requirement is also outlined. The test result
They adhere well to unmodified polyolefin. The key
demonstrates that vehicle crashworthiness can be
component of these coatings is a new polyolefin diol15.
improved by using energy absorbing polyurethane
foam to modify a vehicle’s crash signature. To design
Evans and Morgan16 addressed an alternative to a cost, weight, and energy absorption efficient bumper
bumper energy absorber systems. They also reviewed foam energy absorber, it is important to consider
the industry trends associated with bumper energy optimising the shape of coring employed. Frederick

632 Polymers & Polymer Composites, Vol. 10, No. 8, 2002

 A Critical Review of Polymer-based Composite Automotive Bumper Systems

et. al.20 studied a number of foam coring patterns physical testing. He made recommendations on the
using both empirical and analytical methods. The technique for use in future feasibility studies of
size and shape of the proposed core designs were thermoplastics bumper systems. The new
studied with consideration given to several different polypropylene glass mat thermoplastics (GMT) use
densities of E foam. Finite element analysis was precise directional glass fibre reinforcement; one
used to determine the stress distributions during the part of the fibre is laid unidirectionally, precisely
deformation of foam structures and to optimize the lengthwise across the bumper, and random fibres
shape of the polypropylene. Several coring patterns give consistent distribution of the thermoplastics
were considered and recommended for bumper matrix in the flow regions. A multi-layer structure
foam core design, based on high-energy absorption was specially developed for this application. The
efficiency and low tear stress. They found that front and back layers were GMT with horizontally-
coring can improve the efficiency of the bumper laid fibres about 1800 mm long. Between these are
foam energy absorber. laid GMT cut pieces with vertically-arranged fibres.
In –filled pieces with fibres horizontally arranged
were introduced in the center of the component.
5. MATERIALS FOR COMPOSITE The part was moulded in a fully-automatic plant,
BUMPER BEAMS heating the blanks to over 200 °C, placing them in
the press by robot, and moulding at about 1700 tons
Maahs and Janowiak21 studied some of the materials
pressure. The beam gained further absorption
available for manufacturing composite bumper beams.
strength from four polyurethane core units, with
They carried out a material selection procedure to
three items behind and one in front. Finally, the
decide the most suitable materials for bumper beams,
structure was clad with a shell of R-RIM, using a
which are categorized in three major groups, namely
glass fibre reinforced paintable PUR system. Gilliard
thermosetting, thermoplastics and structural reaction
et. al.27 developed an I-section beam with 40%
injection moulding (SRIM). Finite element analysis
chopped fibreglass GMT. They found that an I-
and cost estimates were also carried out to identify
section bumper design has improved static load and
the most suitable materials. Mohan22 discussed the
dynamic impact performance as a result of using
use of SRIM composite in an automobile bumper
lower cost mineral filled/chopped fibreglass GMT.
beam. The material used was glass fibre reinforced
polypropylene. The tooling cost was lower than that
of metal processes because of the low moulding Front and rear bumper impact beams are generally
pressure used. Much work has been done to establish made of 60% glass vinyl ester sheet moulding
the technical feasibility and economic advantages of compound (SMC), reinforced with a newly developed
the SRIM process for high volume production7. chopped and continuous strand glass fibre giving
strength in all directions. The SMC beam has been
designed to reduce the number of parts, cutting
Clark et. al.23 described their extensive work on
assembly time from 33.7 to 14.5 minutes. The weight
bumper beams using glass fibre reinforced plastics to
of the beam was 6.4 kg with 4-8 mm wall thickness
study the stress contour in the component. Three and it was moulded on a standard compression
dimensional models were developed and the analysis moulding machine. Morgan et. al.5 developed a
was performed using ABAQUS software. The material moulded bumper beam with angled barrier protection.
selected was a 40 % glass fibre reinforced A new front bumper, blow moulded using engineering
polypropylene. Dubensky et. al.24 described the thermoplastics, was used to provide full 8 km/h
process-driven design of a plastics bumper beam, federal pendulum and flat barrier impact protection,
mentioning the benefits of this technique. It has been as well as angle barrier protection, on a small passenger
used to accelerate the process to complete a bumper car. The low extrusion bumper was compatible with
beam concept analysis for a proposed design within the vehicle’s single-sensor airbag systems. They
a very short time. Cheon et. al.25 developed the concluded that a new combination of design,
composite bumper beam for a passenger car. The materials, and tooling used to create a blow moulded
material used was glass fibre fabric epoxy composite bumper beam from engineering thermoplastics had
material, except for the elbow section. The elbow helped to decrease vehicle mass, reduce part count,
section was made of carbon fibre epoxy composite and reduce cost for assembly and labour. It also
materials. Rawson26 described the steps used in allowed for single sensor airbag deployment, and met
designing the bumper, beginning with hand all applicable federal impact performance
calculations and detailed finite element analysis, requirements. The stiffness of randomly oriented
comparing the results obtained to those from actual glass mat thermoplastics (GMT) composites with a

Polymers & Polymer Composites, Vol. 10, No. 8, 2002 633

 S.M. Sapuan, N. Suddin and M. A. Maleque

polypropylene matrix can be increased in the 3-point The literature presented here indicates the polymer-
loading test through the selective use of a co-mingled based composite materials that are available for
E-glass and polypropylene filament thermoplastics bumper systems with manufacturing processability.
prepreg28. Bumper beams for a typical midsize vehicle It is clear that not all materials and/or techniques are
made from combinations of these two materials were suitable for specific bumper components.
moulded and tested using a static bumper test set up, Information on these areas will provide a better
with the load being measured as a function of understanding of the bumper system, materials used
deflection. This led to follow-up tests of materials for it, and processability.
and design strategies for selectively increasing the
stiffness of the GMT composites at selected locations
in the bumper beam. The results showed that the 6. ADVANTAGES AND DISADVANTAGES
GMT materials bore a higher static load than standard OF POLYMER-BASED COMPOSITE
GMT materials. Unidirectional thermoplastics prepreg AND STEEL MATERIALS FOR
offers local reinforcement improvements to glass mat BUMPER SYSTEM
thermoplastics composites29.
The advantages and disadvantages of polymer-based
composite and traditional steel materials for bumper
Rawson29 evaluated the performance of polyolefin in systems are explained in a tabular form in Table 1.
comparison with engineering thermoplastics for blow
moulded bumper beams for mid-sized vehicles. The
author compared the performance of polycarbonate/ 7. CONCLUDING REMARKS
polybutylene terephthalate (PC/PBT) alloys and • It is important to continue to improve bumper
polyolefins for impact protection, weight, and systems to enable them to contribute to vehicle
processing performance. A structural RIM (SRIM) crashworthiness or occupant protection during
bumper beam has been prototyped which is able to front or rear collisions. The success of bumper
meet 8 km/h pendulum and barrier impact systems depends essentially on the design factors
requirements, with and without an energy absorber. and manufacturing processes that engineers
The performance level of this beam has been tested, consider during the design phase.
utilizing an E energy absorber. The new prototype
beams reduce the cost and weight of SRIM bumper
systems. Parks et. al.30 have designed, moulded, and • This critical review has outlined the factors
tested impact performance of a prototype bumper helping us to select the proper polymer-based
beam without an energy absorbing system. composite materials for bumper systems.

Table 1 Advantages and disadvantages of polymer and steel systems31-33.

Polymer-based composite Traditional steel
Advantages Disadvantages Advantages Disadvantages
1. High rate of production High prototype cost Low cost of material Requires protective
coating to prevent
corrosion
2. Good dimensional High cost of tooling Proven technology Processing cost is high
stability
3. High strength to weight Stiffness is low Has good strength Weight of the component
ratio is high
4. Reduced labour cost Process control may Material is readily High setting time is
be poor available required
5. Complex shape can be Properties can be Welding is necessary to
manufactured at low cost anisotropic join components together
6. Cost effective, easy to use Advanced composite has
high raw material cost

634 Polymers & Polymer Composites, Vol. 10, No. 8, 2002

 A Critical Review of Polymer-based Composite Automotive Bumper Systems

• We briefly mentioned the manufacturing Conference, Dearborn, Michigan, 25-28

processability of the bumper components. In September, ASM International, Materials Park,
future, attention should be paid to conceptual Ohio, (1989) 21-27.
design and manufacturing processing, including
the cost savings that can be achieved. 8. Morgan R.E., Nemedy L., Yester S.G., Peterson
D., and Armstrong B., Recycling RIM Thermoset
Polymer into Automotive Fascia, SAE Technical
• The advantages and disadvantages of polymer- Paper, 103, (1994) 89-92.
based materials are explained and compared
with those of traditional steel, traditionally used 9. Hurley M., Lee B., Lewandowski S., Smith T.,
for bumper components. Groenen J., and Nakamura M., Advances in
Competitive Polyurethane Materials for
Automotive Fascia, SAE Technical Paper, 104,
ACKNOWLEDGEMENTS (1995) 401-404.
The authors wish to acknowledge the cooperation of 10. Berg J.W., Lightweight Reaction Injection
Professor Radin Umar, and Dr Megat Hamdan of Moulded Polyurethane for Automotive Fascia,
Universiti Putra Malaysia and Mr Nukman Yusoff of SAE Technical Papers, . 104, (1995) 405-409.
University of Malaya in carrying out this research.
Similarly the financial support of the German 11. Mikulec, M, Automotive Coatings Designed for
Malaysian Institute is highly appreciated. Direct Adhesion to Non-polar Thermo Plastics
olefin, Proceedings of the Waterborne, High
Solids and Power Coatings Symposium,
REFERENCES February 5-7, (1997) 419-422.
1. http://www.bumper.autosteel.org 12. Ryntz, R.A., Painting of plastics, Federation
2. Kelman, J., Nelson, G.V. and Curtis, C.V., Series on Coatings Technology, FSCT, (1994)
Development of testing of a modular integrated 21-24.
front end with a SRIM beam, Proceedings of the 13. Komatsu Y., Kamimura J., Aoki O., Chung D.B.,
Sixth Advanced Composites Conference, and Wiseman M.S., New TPO and Coating
Detroit, Michigan, 8-11 October, ASM Technology for Bumper Without 1.1.1-
International, Materials Park, Ohio, (1990) Trichloroethane, SAE Technical Paper, 103,
37-41. (1994) 104-112.
3. Cheon, S.S., Choi J.H. and Lee D.G., Development 14. Clair D.J., Polyolefin Diol in Coatings for
of the Composite Bumper Beam for Passenger Thermoplastics Polyolefins, SAE Technical
Cars, Composite Structures 32, Elsevier Science Paper 980707 (1998).
Limited 491-499, (1995).
15. Handliin, D.L. et al., US Patent 5, 405, 911, April
4. Minaudo B.P., Rawson J., and Montone M., 11, (1995)
Development of a One-Piece, Injection Moulded,
Thermoplastics Rear Bumper System with Pole 16. Evans D., and Morgan T., Engineering
Impact Protection, SAE Technical paper, 106, Thermoplastics Energy Absorber for Bumpers,
(1997) 498-503. SAE Technical Paper, 108, (1999) 884-894.
5. Morgan T., Corsello M., Day A., Rawson J., and 17. Kelly D.J., and Rucker J.R., New Polyurethane
Fadewa B., Development of a Blow Moulded, Polymers for Energy Absorbing Automotive
Thermoplastics Front Bumper System Offering Applications, SAE Technical paper, 106, (1997)
Angled Barrier Protection, SAE Technical paper, 243-247.
104, (1997) 515-524.
18. Sounik D.F.,Gansen P., Clemons J.L., and Liddle
6. Cheon, S.S., Lim T.S. and Lee D.G., Impact W., Head-Impact of Polyurethane Energy
Energy Absorption Characteristics of Glass Fibre Absorbing (EA) Foams, SAE Technical Paper,
Hybrid Composites, Composite Structures 46, 106, (1997) 211-220.
Elsevier Science Ltd, (1999) 267-278.
19. Syrowik G.F., Huber M.A., Saunik D.F, and
7. Dodyk, L., High performance composites for the Gansen P., Energy Absorbing Polyurethane
automotive industry, Proceedings of the Fifth Foam to Improve Vehicle Crashworthiness, SAE
Annual ASM/ESD Advanced Composites Technical Paper, 104, (1995) 411-419.

Polymers & Polymer Composites, Vol. 10, No. 8, 2002 635

 S.M. Sapuan, N. Suddin and M. A. Maleque

20. Frederick G., Kae G.A., Kudelko C.M., Schuster 26. Rawson J.M., Comparison of Analysis Results
P.J., Domas F., Haardt U.G., and Lenz W, to Physical Testing for the Performance of
Optimisation of Expanded Polypropylene Engineering Thermoplastics Bumper Beams,
Foam Coring to Improve Bumper Foam Core SAE Technical Paper, 103, (1994) 81-86.
Energy Absorbing Capability, SAE Technical
27. Gilliard B., Bassett W., Haque E., Lewis T.,
paper, 104, (1995) 394-400.
Featherman D., and Johnson C.,, I-Section
21. Maahs, W.P. and Janowiak, A.R., Composite Bumper with Improved Impact Performance
bumper beams: comparing material choices, from New Mineral-Filled Glass Mat
Proceedings of the Third Annual Conference Thermoplastics (GMT) Composite, SAE
on Advanced Composites, Detroit, Michigan, Technical Paper, . 108, (1999) 900-908.
15-17 September, ASM International, 28. Green J., and Gilliard B., Improving the Stiffness
Materials Park, Ohio, (1987) 11-21. Performance of Glass Mat Thermoplastics
22. Mohan, R., SRIM composites for automotive Composite Bumper Beams using BI and Uni-
structural alications, Proceedings of the Third Directional Thermoplastics Composites, SAE
Annual Conference on Advanced Composites, Technical paper, 106, (1997) 504-510.
Detroit, Michigan, 15-17 September, ASM 29. Rawson, J., Performance Evaluation of
International, Materials Park, Ohio, (1987) 57-62. Polyolefins versus Engineering Thermoplastics
for Blow Moulded Bumper Beams for Mid –
23. Clark, C.L., Bals, C.K. and Layson, M.A., Effects
Size Vehicles-Part 11, SAE Technical Paper, .
of fibre and property orientation on ‘C’ shaped
108, (1999) 909-915.
cross sections, SAE Technical Paper 910049
(1991). 30. Parks K.L., Kelman J., Muller H., and Chiba T.,
Advancement in Low Cost Bumper System,
24. Dubensky R. G., Jay D.E. and Salansky R. P., SAE Technical paper, 104, (1995) 386-393.
Proposed driven design of a plastics bumper
beam, Proceedings of the 5th Annual ASM/ 31. Sapuan, S.M., Fibre reinforced plasticss in
ESD Advanced Composite Conference, 25-28 automotive pedal boxes, Polymers and Polymer
September, Deorborn, USA, (1989) 29-32. Composites, 7, 6, (1999) 421-429.
32. Murphy, J., Reinforced Plastics Handbook,
25. Cheon. SS, Lee. DG, Jeong. KS., Composite
Elsevier Advanced Technology, Oxford, (1994).
Side Door Impact Beam for Passenger Cars.
Composite Structures, 38, No. 1-4, (1997) 33. Suart F. B., Tough Composites Hit the Road,
229-239. Fortune, New York, Jan 24, (2000) 110B-116B.

636 Polymers & Polymer Composites, Vol. 10, No. 8, 2002