DRAFT

COST-EFFECTIVENESS OF A 25% BODY AND CHASSIS WEIGHT-REDUCTION GOAL IN
LIGHT-DUTY VEHICLES

Sujit Das

Energy and Transportation Science Division

Oak Ridge National Laboratory

Prepared for

Lightweighting Materials

Office of Vehicle Technologies

U. S. Department of Energy

August 2008

OAK RIDGE NATIONAL LABORATORY

Oak Ridge, Tennessee 37831

managed and operated by

UT-Battelle, LLC

for the

U.S. DEPARTMENT OF ENERGY

under contract No. DE-AC05-00OR22725

Cost-Effectiveness of a 25% Body and Chassis Weight-Reduction Goal

in Light-Duty Vehicles

Oak Ridge National Laboratory

August 2008

1.  Background

With the recent higher gasoline prices and new rules requiring
automakers’ fleets to have average fuel economy of at least 35 mpg by
2020, the pressure to lightweight vehicles is stronger than ever before.
Vehicle lightweighting represents one of several design approaches
automakers are currently evaluating to improve fuel economy.
Lightweighting is typically accomplished by downsizing, integrating
parts and functions, substituting materials, or by combining these
methods. Lightweighting Materials’ (LM’s) component of the U.S.
Department of Energy’s Vehicle Technologies program focuses on the
development and validation of advanced materials and manufacturing
technologies to significantly reduce automotive passenger vehicle body
and chassis weight without compromising other attributes such as safety,
performance, recyclability, and cost. The specific goals of LM are to
develop material and manufacturing technologies by 2010 that, if
implemented in high volume, could cost-effectively reduce the weight of
passenger-vehicle body and chassis systems by 50% with safety,
performance, and recyclability comparable to 2002 vehicles. In order to
achieve this long-term weight-reduction goal, LM has set annual
intermediate weight-reduction goals, starting with 10% in FY2007, and
finally achieving 50% by FY2010. This paper focuses on the 25% body and
chassis weight-reduction goal of FY2008, with emphasis on the assessment
of cost-effectiveness to achieve this desired goal.

To achieve its long-term weight-reduction goal, LM has prioritized its
research areas in several lightweighting materials including advanced
high-strength steel, aluminum, magnesium, titanium, and composites.
Composites include metal-matrix materials and glass- and carbon-fiber
reinforced thermosets and thermoplastics. Over the past several years,
the LM R&D portfolio has included assessments of various lightweight
body and front-end structures, such as those constructed of advanced
high-strength steel, composite-intensive, and magnesium. These
assessments, either completed or underway, include, for example, one in
which the goal is to design, analyze, and develop the technology for a
composite-intensive, body-in-white structure that achieves a minimum of
60% weight savings over steel. Additionally, the latest LM
multi-material vehicle (MMV) project aims to synthesize and demonstrate
these various lightweight material component options in a single
vehicle. Cost remains one of the major obstacles to successful market
penetration of these various lightweight materials. Today OEMs remain
more focused on the vehicle’s retail price rather than on vehicle life
cycle cost.

This paper provides an assessment of the cost-effectiveness of a 25%
body and chassis weight-reduction goal for FY2008. The
cost-effectiveness of the proposed weight-reduction goal is determined
based on the vehicle retail and life cycle cost analyses of scenarios of
potential lightweight material substitution in various body and chassis
components to achieve the desired weight-reduction goal. Cost
methodology and potential data sources for the analysis are then
discussed. Cost data collected for various vehicle components considered
for achieving the weight reduction goal are then discussed, as are the
assumptions and methodology used. A discussion of the results of the
cost analysis of proposed scenarios is then presented, followed by
conclusions.

2.  Approach

2.1  Scenario Development

Cost-effectiveness of a 25% body and chassis weight-reduction goal was
demonstrated based on scenario analysis with each scenario focusing on a
specific lightweight material type substitution at a major
vehicle-component level. A representative mid-size vehicle, i.e. Honda
Accord, was considered as the baseline against which the
cost-effectiveness of scenarios was determined. Two plausible material
scenario—one for aluminum and another for glass fiber-reinforced
polymer-matrix composites (glass-FRPMCs)—have been developed with the
focus on body and chassis applications. These two materials have the
potential to achieve the desired weight-reduction goal. Aluminum use in
today’s light-duty vehicles is limited to about 325 lbs/vehicle,
mainly in castings for the powertrain (engine block, cylinder head and
transmission cases) and wheels, but aluminum use could be significantly
greater with the addition of wrought aluminum that has a weight
reduction potential range of 30-50% compared to conventional steel.
Glass-FRPMCs are used less than aluminum in today’s vehicle, and their
application is limited to complex non-structural assemblies.
Glass-FRPMCs offer a weight reduction potential of 20-35% compared to
conventional steel.

Table 1 shows the two 25% body and chassis weight-reduction scenarios
for a mid-size passenger car considered in the cost-effectiveness
analysis. Each scenario focuses on a specific lightweight material
option. This scenario approach allows determination of
cost-effectiveness at a vehicle level, the context important for the
actual implementation and commercialization of the lightweighting
materials technologies in the market place. Parts considered for the
lightweight material substitution are based on their near-term market
potential; the specific total number of parts considered under each
scenario is dictated by the material type and its weight reduction
potential for achieving the overall body and chassis weight reduction
goal. Specific components considered under body and chassis vehicle
subsystems for both scenarios are highlighted in Table 1 (in bold type).
The potential weight reduction for each part also is given. Since most
lightweight component options considered here are yet to be
commercialized, the percentage weight reduction assumed in each case is
based on the best estimated value available in the literature today. The
definitions of various vehicle components are based on the Automotive
System Cost Model (ASCM, discussed below) and are provided in Appendix
A.

Table 1. Mid-Size 25% Body& Chassis Weight Reduction Scenarios

SYSTEM

	Baseline	Glass-FRPMC

(25% Weight Reduction) Scenario	Aluminum

(25% Weight Reduction) Scenario

	Technology	Mass (kg)	Technology	Mass (kg)	Technology	Mass (kg)

Powertrain

Engine	V-6 3.0L DOHC AL/AL	197	V-6 3.0L DOHC AL/AL	197	V-6 3.0L DOHC
AL/AL	197

Energy Storage	Lead-Acid, Standard	19	Lead-Acid, Standard	19	Lead-Acid,
Standard	19

Fuel System	Gasoline, 17 gal	83	Gasoline, 17 gal	83	Gasoline, 17 gal	83

Transmission	Automatic (L5)	81	Automatic (L5)	81	Automatic (L5)	81

P/T Thermal	Generic (car)	29	Generic (car)	29	Generic (car)	29

Driveshaft/Axle	Generic	77	Generic	77	Generic	77

Differential	Generic	25	Generic	25	Generic	25

Exhaust System	Generic	48	Generic	48	Generic	48

Oil and Grease	Generic	15	Generic	15	Generic	15

Powertrain Electronics	Generic	10	Generic	10	Generic	10

Emission Control Electronics	Generic	10	Generic	10	Generic	10

Body

Body-in-White	Midsize steel unibody	320	Glass Fiber TS/Composite (30% wt
redn.)	232	Aluminum Unibody (40% wt redn.)	176

Panels	Stamped Steel	60	Glass Fiber TS/Composite (25% wt redn.)	39
Stamped Aluminum (40% wt redn.)	36

Front/Rear Bumpers	Sheet Steel	10	Stamped Aluminum (40% wt redn.)	6
Stamped Aluminum (40% wt redn.)	6

Glass	Conventional, 4 mm	40	Conventional, 4 mm	40	Conventional, 4 mm	40

Paint	Solventborne, avg color	12	Solventborne, avg color	12
Solventborne, avg color	12

Exterior Trim	Generic	10	ULSAB (35% wt reduction)	6.5	Generic	10

Body Hardware	Generic	10	Generic	10	Generic	10

Body Sealers and Deadners	Generic	2	Generic	2	Generic	2

Chassis

Cradle	Generic	35	Cast Aluminum (45% wt redn.)	19	Generic	35

Corner Suspension	Generic	47	Aluminum (35% wt. reduction)	31	Generic	47

Braking System	ABS	48	Aluminum (5.5% wt. reduction)	45	ABS	48

Wheels and Tires	Aluminum 15”	71	Aluminum 15" – Forged (11% wt.
redn.)	63	Aluminum 15”	71

Steering System	Generic	27	Aluminum (5.5% wt. reduction)	26	Generic	27

Interior

Instrument Panel	Generic	26	Generic	26	Generic	26

Trim and Insulation	Generic	24	Generic	24	Generic	24

Door Modules	Generic	28	Generic	28	Generic	28

Seating and Restraints	Generic	66	Generic	66	Generic	66

HVAC	Generic	22	Generic	22	Generic	22

Electrical

33

33

33

Final Assembly

40

40

40

Total Body & Chassis Weight

(% less than baseline)

692

523

(25%)

520

(25%)

Total Vehicle Weight

1525

1356

1353

Table 1. Lightweighting Options Considered for Various Body & Chassis
Components

Under Two Lightweight Material Scenarios

2.1.1 Aluminum

Aluminum unibody structure and panels have been considered under the
aluminum scenario, although most applications to date—as in the Audi
A2 and A8 and the Chevrolet Corvette C6 Z06—have been an aluminum
spaceframe structure achieving weight savings in the range of 30-40%.
Unibody architecture is currently being used in the Jaguar XJ8, and it
favors higher volumes with lower variable costs. The tradeoff is the
expense of higher investment costs due to expensive stamping dies. Under
simple load cases (e.g., bending stiffness and three-point bending),
aluminum use can provide up to 50%-60% mass reduction at the expense of
40% more package space compared to steel. But, in actual vehicle body
structures, where load cases are much more complex, actual reductions
obtained are lower and depend on whether they are compared to optimized
steel design (such as ultra light steel autobody) or the conventional
non-optimized steel design. Recent study by Aluminum Association on the
use of aluminum structures in conjunction with alternative powertrain
structures in automobiles indicates a weight savings potential of 47%
over the steel baseline—similar to the value obtained in Ford’s
aluminum intensive concept vehicles, the Ford Taurus 1997, an effort
initiated in late 1990s (Aluminum Association 2008). A lower weight
reduction potential of 45% has been used in our analysis in order to
achieve the overall body and chassis weight reduction goal. A 40% weight
reduction assumption for closure panels is consistent with the recent
Aluminum Association design and the latest estimate (Montalbo et al.
2008). Besides body structure and closure panels, aluminum substitution
of front and rear bumpers has been included to achieve the desired total
25% primary weight savings goal. Bumpers are a good example of a
successful aluminum bolt-on high volume application.

2.1.2 Glass-FRPMC

Application of glass-FRPMC in automobiles is quite limited and occurs
only in low-volume niche vehicles today such as Chevy Corvette, Dodge
Viper, and Cadillac XLR. The highest volume of composites use in Class A
exterior applications is in the fascia systems. Similarly, exterior
non-class A composites use is currently limited to a select few
applications such as pickup truck box inner panels, removable roofs,
gate panels, running boards, truck enclosures, wheel housings, and
underbody panels. The very few limited structural composites
applications today are radiator supports, bumper beams, skid plates, and
grille opening reinforcements. Consideration of glass-FRPMC in our
analysis was mainly limited to body applications that have the most
total weight reduction potential. A weight reduction potential of 30%
compared to steel was assumed, compared to 25% value reported for
reinforced reaction injection molded polyurea/glass flake body structure
(Dieffenbach and Mascarin 1993). However, for glass-FRPMC panels, a 25%
weight reduction was assumed consistent with the available estimates.
Recent results of the United States Automotive Materials Partnership
(USAMP) Multi-Material Vehicle (MMV) project on the composite underbody
has considered several glass-fiber reinforced polymer options providing
a weight savings potential of 7-40% compared to the steel baseline, the
upper limit of reduction available when glass-fiber fabric with cores is
used (DOE 2008). However, when considered on the basis of functional
equivalence (with the consideration of reinforcement brackets and rails)
to steel in addition to the stiffness and crashworthiness requirements,
the weight savings potential was estimated to be around 20% with random
glass fibers with core. It is most likely that the assumed body weight
reduction potential of body-in-white structure in our case is on the
high side based on the applications seen in the marketplace so far.

Due to lower weight reduction potential of glass-FRPMC compared to
aluminum, the glass-FRPMC scenario includes the use of aluminum in
several vehicle body and chassis components to achieve the desired body
and chassis weight reduction goal. Aluminum has been considered for
front/rear bumpers, corner suspension, cradle, braking system, steering
system, and wheels and tires. Aluminum (forged or cast) is desirable in
vehicle chassis components since it reduces un-sprung weight of the
suspension, thereby improving overall handling performance and ride
comfort. Weight reduction for the cradle has been assumed to be higher
than for front/rear bumpers, i.e., 45% vs. 40%. Aluminum penetration has
been relatively high in steering knuckles, and a weight reduction in the
range of 35-45% can be achieved by integrating multiple parts into a
single unit. Similarly, aluminum control arms have a market share of 20%
today, with a weight reduction potential of 20-30% compared to steel.
Aluminum corner suspension substitution assumes here both aluminum
control arms and steering knuckles, with a combined weight reduction
potential 35%.

Aluminum use has been considered for brake actuators and steering wheel
column, with an estimated weight savings potential of 30.5% and 43%,
respectively (EEA 2007). However, in both cases, the substitution of a
single component in the system achieves a relatively small weight
reduction at the system level compared to the weight reduction of the
part alone. The overall weight reduction potential is assumed to be
5.5%. Although the wheels segment has seen consistent growth in aluminum
use, it is anticipated that there will be shift from cast wheels to
forged wheels without any overall huge percentage market gains in the
future. Forged wheels considered here for wheels and tires are estimated
to provide an additional 11% weight savings compared to cast aluminum
wheels. In order to achieve the total around 25% primary body and
chassis weight savings goal, a 35% reduction in exterior trim weight has
been assumed. This weight savings is consistent with the target weight
for the PNGV-Class vehicle which has a target weight of around 203 kg
body structure (ULSAB-AVC 1999).

2.1.3  Secondary Weight Savings

The objective for the selection of lightweighting material options for
various vehicle components (as discussed above) was to achieve the
primary 25% body and chassis weight-reduction goal. However,
consideration of secondary weight savings in body and chassis components
is important because it takes into account the effect of primary savings
on the powertrain, chassis, and body components. Powertrain resizing in
secondary weight savings calculations allows comparisons of functionally
equivalent vehicle designs—a reduced vehicle weight requires a less
powerful engine to achieve equivalent performance (i.e., acceleration,
range etc.). Secondary weight savings have been estimated by ASCM and
those related to the two scenarios considered here are presented in
Table 2, along with other estimated major parameters in the
cost-effectiveness analysis. Although the primary weight savings in both
lightweight material scenarios are roughly the same, the total secondary
weight savings obtained is different because of different components
considered for primary weight savings. Total secondary weight savings is
estimated to be 70% and 44% of primary savings for aluminum and
glass-FRPMC lightweight material scenarios, respectively. The aluminum
scenario achieves a higher percentage of secondary weight savings
because the substitutions are limited to body components, whereas the
glass-FRPMC scenario includes both body and chassis components. Most
estimated secondary weight savings occur in the powertrain system under
both scenarios. Absolute secondary weight savings is less in the case of
glass-FRPMC since primary weight savings resulted in lower chassis
component weight although the percentage secondary weight reduction
value used per component has been the same as the other scenario. Total
estimated secondary weight savings depend on the extent of powertrain
downsizing assumed and also the total number of vehicle components
considered. Since secondary weight savings is limited to only major
vehicle components in ASCM (i.e., all chassis components and a few major
powertrain and body components), the percentage total weight savings in
this case is somewhat lower than another recent estimate (Malen and
Reddy 2007).

Table 2.  Estimated Major Parameters Considered for Cost-effectiveness
of 25% Body and Chassis Weight Reduction Goal

Parameter

Baseline	25% Body and Chassis Weight Reduction Scenario

Aluminum	Glass-FRPMC

Primary Body & Chassis Weight Savings	NA	172 kg (25%)	169 kg (25%)

Secondary Weight Savings

	Body & Chassis	NA	46 kg (6.6%)	11 kg (1.6%)

Powertrain	NA	74 kg	63 kg

Total	NA	120 kg	74 kg

Body & Chassis Weight	692 kg	475 kg (31.6%)	511 kg (26.1%)

Powertrain Weight	594 kg	520 kg (12.5%)	531 kg (10.6%)

Engine Power	122 kW	102 kW	105 kW

Final Vehicle Weight	1524 kg	1235 kg (19%)	1281 kg (16%)

Combined Fuel Economy 	23 mpg	25.9 mpg	25.5 mpg

Vehicle Lifetime Operation	120,000 miles

Note: % values within parenthesis indicate w.r.t. baseline steel

With the consideration of secondary weight savings, total body & chassis
weight savings is estimated to be 31.6% and 26.1% for aluminum and
glass-FRPMC scenarios, respectively, higher than the 25% primary weight
reduction goal as shown in Table 2. There will be a decrease in
powertrain weight with powertrain resizing, where engine power is
estimated to decrease by 14%. The resulting percentage vehicle weight
reduction for the corresponding scenarios has been estimated to 19% and
16%, respectively. Fuel economy estimates have been based on a
reasonable rule of thumb that each one percent reduction in weight
should give a 0.66 percent improvement in fuel economy, after a vehicle
has been fully redesigned to account for the reduced power demands of a
lower mass. Combined vehicle fuel economy would increase from the
baseline value of 23 mpg to 25.9 mpg and 25.5 mpg for aluminum and
glass-FRPMC scenarios, respectively, with the 25% body and chassis
weight-reduction goal. Total vehicle operation lifetime is assumed to be
120,000 miles based on average annual miles driven and vehicle life as
10,000 and 12 years, respectively.

2.2 Cost Estimation Methodology

The cost-effectiveness of the 25% body and chassis weight-reduction goal
was estimated using the Automotive System Cost Model (ASCM), developed
jointly by Oak Ridge National Laboratory and Ibis Associates, Inc. in
collaboration with Argonne National Laboratory. ASCM estimates the
vehicle-manufacturing cost at a level of five major vehicle subsystems
(powertrain, chassis, body, interior, and electrical) consisting of more
than thirty-five components based on the aggregation of several
components under the definition of Uniform Parts Grouping (UPG)
generally used by the automotive industry (as listed and defined in
Table 1 & Appendix A). Each component represents a specific
manufacturing technology. Vehicle retail price based on the sum of
manufacturing cost (i.e., costs of components and assembly), overhead,
and selling is added to vehicle operation costs for the vehicle life
cycle cost estimation. The interrelationships among vehicle subsystems
and their effect on vehicle manufacturing cost are addressed, allowing
inclusion of the impacts of secondary mass and cost savings as well.
Functional interrelationships have been developed for major chassis
components to estimate secondary mass savings based on first principles
of physics, and using semi-empirical and empirical information available
from the literature today. The powertrain sizing routine in this model
is based on the algorithm used in the Argonne National Laboraotry’s
(ANL) hybrid vehicle cost model (HEVCOST), where the power and mass
projections of various powertrain components are based on
component-specific power and efficiency values, with the capability to
evaluate alternative hybrid electric vehicle configurations and
performance strategies (Plotkin et al. 2001). The main objective of this
model is to facilitate estimation of vehicle-manufacturing and
life-cycle costs using a uniform methodology to allow comparison of
alternative technologies being considered for advanced technology
vehicles today. This cost model has been recently integrated into the
vehicle performance model PSAT (Powertrain System Analysis Toolkit)
developed by Argonne National Laboratory, thereby facilitating
instantaneous vehicle cost estimation based on the detailed powertrain
component sizing estimates by PSAT. This cost model has been used in
several studies for a comparative cost assessment of different
powertrain and body-in-white options for advanced technology vehicles
(Das 2004 and 2005; Rousseau et al. 2005).

Two types of overhead, i.e., OEM and dealer margin are added to the
vehicle manufacturing cost to estimate vehicle retail price. The former
is assumed to be fixed, while the latter varied with the vehicle
manufacturing cost. Vehicle operation cost categories considered in the
vehicle life cycle cost estimation include financing, insurance, local
fees, fuel, battery replacement, maintenance, repair, and disposal.
Financing, insurance, and local fees costs are dictated by the vehicle
retail price, and so is the fuel cost by fuel economy (estimates are
shown in Table 2) and an assumed gasoline price of $4/gallon in this
analysis. With the exception of maintenance and repair, all other
operation cost categories vary with the two lightweighting scenarios
considered here based on estimated vehicle retail price and fuel
economy. Total life cycle cost is estimated as the net present value
assuming a vehicle life of 12 years, 120,000 vehicle lifetime operation
miles, and a discount rate of 10%.

2.3 Component Cost Data

Component technology cost data as highlighted by bold letters under the
two scenarios in Table 1 were collected mainly based on the latest
estimates developed by Ibis Associates, Inc. using results of the recent
studies developed for the industry (Ibis 2008). For example, both the
Aluminum Association and USAMP have recently been involved in the
detailed cost analysis of aluminum and glass-FRPMC body structures,
respectively. For other lightweight component technology costs
considered here, where detailed analyses were unavailable, existing Ibis
cost models developed for the relevant materials systems were used to
estimate the component costs. Cost data for other components—those for
which the technology remained unchanged—were the same as those in the
original model, since our objective in this analysis is to determine the
relative cost-effectiveness of these two lightweight scenarios and not
the absolute total vehicle cost. Note that component technology costs in
ASCM are based on OEM costs and represented in terms of functional
relationships such as component mass and power, derived based on the
detailed cost analyses available in the literature.

The cost estimate of the aluminum unibody structure is based on the
latest detailed evaluation by the Aluminum Association, which has
reconsidered the manufacturing economics of the original P2000 program
with updated practices and materials pricing (Aluminum Association
2008). The aluminum structure was 47% lighter than the steel baseline on
the basis of weight distribution assumptions of 94% aluminum stampings,
3% aluminum castings, and 3% mild steel stampings, at a 30% cost
premium. Based on the regression analysis of multiple scenarios results,
cost relationships of structure, panel, and assembly have been developed
separately as a function of part mass, material price, part count, part
area, and annual production volume which were then used in the analysis
here.

Recent cost estimates of the underbody for a luxury rear-drive vehicle
developed by Ibis Associates, Inc. considered under the USAMP MMV
project were used for the development of cost relationships for
glass-FRPMC body components. Several combinations of fiber type (glass
vs. carbon) and form (random vs. fabric) and manufacturing technologies
were considered under that project. Specific material masses both in
terms of absolute values and relative weight fractions for underbody
were based on the detailed design effort. Among several competing
molding technologies considered under this project, cost data for
compression of sheet molding compound was used for the analysis here.
The sheet molding compound was modeled as a separate operation by
molders, either as a profit center for companies with internal
compounding or as a material purchased from a separate company. Random
glass fiber with core and vinyl ester as the matrix material were used
where composites contributed 57% to the overall part weight. In order to
extend the composite underbody results to the entire structure, the
equivalent description of components comprising the floor and rails in
the baseline steel BIW was examined, and the overall underbody was
calculated to be 29% of the mass and 25% of the cost of the entire
structure. Cost relationships thus developed reflect the latest pricing
information and molding processing technology.

Figure 1 shows the estimated cost sensitivity to annual production
volume of three types of body-in-white structures considered in this
analysis. The cost of body-in-white structure includes the assembly
cost. Cost graphs shown here are based on the baseline weight for a
mid-size vehicle considered in the model and not the actual weight used
in the analysis here. For example, baseline masses of body-in-white
structure considered for steel, aluminum, and thermoset/glass composites
(TS/glass composites) are 250 kg, 143 kg, and 202 kg, respectively.
Based on the current material pricing (i.e., steel at $0.77/kg aluminum
sheet at $3.31/kg, aluminum casting at $2.86/kg, vinyl ester compound at
$4.24/kg, and glass fiber at $1.50/kg) and masses assumed, the aluminum
unibody structure is always more expensive than steel, whereas TS/glass
composites are competitive at annual production volume up to 60,000
parts. Most past studies indicate a lower production volume for
cross-over point for the cost-effectiveness of TS/glass composites, yet
a recent study shows glass-reinforced body-in-white structure can be
cost-effective at an annual production volume up to 105,000, which
represents 68% of car models and 29% of all cars produced in North
America in 2005 (Fuchs 2008). The cost sensitivities of steel and
aluminum structures are quite similar to each other in terms of the
curve slope, but they are offset by the material price difference and
some increased processing costs. As also has been observed earlier, the
cost sensitivity curve for glass-

Figure 1. Lightweight Material Body-In-White Cost Sensitivity to

Annual Production Volume

FRPMC body structure is relatively flat compared to other materials. For
our analysis, the threshold production volume of cost-effectiveness has
been considered, 240K parts/year for both baseline steel and aluminum,
whereas 60K parts/year for glass-FRPMC.

Figure 2 shows the part cost sensitivity to aluminum casting price for
four different aluminum chassis components considered under the
glass-FRPMC scenario based on part weight used in a mid-size vehicle.
Note that part cost estimates under the assumed base material price for
the comparative scenario analysis here are also shown in this figure.
Cost relationships for aluminum cradle and forged aluminum wheels
include not only casting cost, but also melting, scrap recovery,
machining, and corrosion protection. Cost of forged aluminum wheels are
based on 15” wheels and reflects current material pricing and
processing technology improvements and also includes tire costs. Cost
estimates of aluminum braking and steering systems were made by adding
the estimated cost of replaced aluminum component (e.g., brake actuators
and steering wheel column for braking and steering systems,
respectively) to the unchanged original balance of system cost made of
conventional steel. Cost data of replaced aluminum components are based
on the recent available estimate (EEA 2007). Cost relationships consist
of two components, i.e., material and processing. As Figure 2 shows,
forged aluminum wheels have a higher processing cost component than for
cast aluminum cradles. Higher weight of corner suspension causes its
cost to be higher and more sensitive than the chassis to aluminum ingot
price. The material price cost sensitivity of steering and braking
system cost is not that high since aluminum component in each case
contributes to less than 10% of total system weight.

Figure 2. Aluminum Chassis Component Cost Sensitivity to Material Price

3.0 Results

Figure 3 shows the cost savings for the two scenarios compared to the
baseline, by major vehicle systems, vehicle retail price, and life cycle
cost. Only three major vehicle system cost savings have been considered
in this figure as defined in ASCM and listed in Table 1, since other
system costs (i.e., interior, electrical, and final assembly) have been
assumed to be the same under all scenarios. Vehicle retail price would
increase by about $180/vehicle under the aluminum scenario, however
there would be about $1100/vehicle cost savings in terms of life cycle
cost. The increase in vehicle retail price is mainly due to the body
system cost increase of about $1000, the result of the higher cost of
aluminum body structure. The cost savings due to the downsizing of the
powertrain and chassis is not sufficient to lower the vehicle retail
price. It is estimated that if the price of aluminum sheet used in the
body structure and panels is reduced from the baseline price of $3.31/kg
to $2.95/kg, the cost-effectiveness at the vehicle retail price could
then be achievable. The improved fuel economy under the aluminum
scenario lowers fuel costs significantly—enough to offset small
increases in the small increase in vehicle retail price—to result in
an overall total lower vehicle life cycle cost.

Figure 3. Estimated Cost Savings of Two Lightweight Material Vehicle
ScenariosThe glass-FRPMC on the other hand is cost-effective based on
both vehicle retail price and life cycle cost. The increase in vehicle
body system cost is not as high as in the case of aluminum scenario
(i.e., about $400/vehicle compared to $1000/vehicle for aluminum), since
as discussed earlier under and shown in Figure 1 that the cost of
aluminum body structure is more expensive than thermoset glass-FRPMC
structure at all annual production volumes. Powertrain system and
chassis system cost savings are lower in the glass-FRPMC scenarios
because the overall vehicle weight reduction is less than in the
aluminum scenario, the difference being less secondary weight savings
for glass-FRPMC. Higher aluminum price has also contributed to lower
chassis system cost savings in this case. Cost savings in terms of
vehicle retail price and life cycle cost are estimated to be about $280
and $1600, respectively. Vehicle life cycle cost savings is higher in
this case not only due to vehicle retail price savings but also because
costs incurred in some of the operation cost categories such as
financing, insurance, and local fees, are reduced.

4.0 Conclusions

Cost-effectiveness of ALM’s 2008 body and chassis weight reduction
goal of 25% in light-duty vehicles was assessed based on the use of
lightweight material options for various body and chassis components
under two plausible mid-size vehicle scenarios, each scenario focusing
on a specific lightweight material option, i.e., aluminum or
glass-FRPMC. Lightweight material substitution options considered here
focused on under body systems; but additional chassis components for
substitution were also selected for the glass-FRPMC scenario to achieve
the desired overall weight reduction goal. The analysis also considers
the effect of primary weight savings of 25% on other vehicle components
that can be resized while maintaining the same level of vehicle
performance with the reduced vehicle weigh. This weight savings is known
as secondary weight savings. Estimated secondary weight savings varied
between the two scenarios because of the difference in consideration of
total number and type of components for primary weight savings. Due to
consideration of secondary weight savings, total body and chassis weight
savings is estimated to be in the range of 27-32%, whereas final vehicle
weight savings of 16-19%. Cost-effectiveness of 25% body and chassis
weight reduction goal is estimated in terms of both vehicle retail price
and life cycle cost using the detailed 35+ component level automotive
system cost model developed by ORNL and Ibis Associates, Inc. Cost data
of components considered for lightweight material substitution are
collected from the recently completed major studies, thereby reflecting
the latest technology developments and material prices.

Because of the consideration of powertrain resizing and secondary body
and chassis mass savings, both lightweight material vehicle options are
cost-effective in meeting the ALM 25% body and chassis weight savings
goal from the life cycle cost perspective. Use of lightweighting
materials such as aluminum and glass-FRPMC would be sufficient to
achieve the goal but cost-effectiveness needs to be considered beyond
just the component-to-component material substitution and vehicle retail
price basis. Consideration of secondary weight savings and vehicle life
cycle cost perspectives are important when considering the economic
viability of lightweighting vehicles. Among the two lightweight material
options considered, glass-FRPMC appears to be more cost-effective since
the cost of body structure of  aluminum is still high today even with
the consideration of latest technology developments and material
pricing. In the case of aluminum scenario, the vehicle retail price
would be about be $180 higher; a reduction in aluminum sheet price to a
value of about less than $3.00/lb would improve its competiveness at the
vehicle retail price level. Because of the consideration of secondary
mass savings, the cost penalty due to lightweighting vehicles has been
found to be more favorable than those reported earlier in the
literature. Since the cost penalty for the use of lightweight body
structure estimated to be in the range of $400-$1000/vehicle under two
scenarios when not accounting for secondary mass savings, it is likely
that a significantly higher fuel price would be necessary if the
cost-effectiveness without secondary mass savings effect needs to be
achieved on a life cycle cost perspective at least for the high end of
body structure cost penalty case.

Findings in this analysis are consistent with the latest findings by the
Aluminum Association although complete secondary mass savings have not
been taken into consideration in vehicle life cycle cost comparisons
(Aluminum Association 2008). The aluminum body structure and panels
using the conventional powertrain have been found to be the most
cost-effective option with the consideration of powertrain resizing and
other subsystems’ weight savings. Furthermore, aluminum vehicles with
conventional powertrain offer the least cost on the basis of combined
powertrain and body structure cost at $44 per mpg change with a 10% mpg
improvement but a lower life cycle cost among the various advanced
vehicle technology options considered in that study. Vehicle platforming
considerations which allow low annual production volume would facilitate
the competitiveness of glass-FRPMC body structure as also has been noted
in the latest study (Fuchs (2008). Lightweighting also improves the
cost-effectivenesss of advanced technology vehicles by lowering the
expensive powertrain cost while maintaining the performance (Aluminum
Assocation (2008) and Das (2005)). Consideration of powertrain resizing,
secondary mass savings, and life cycle cost perspectives would therefore
be important to maximize the fuel economy gains from a lightweight
structure and eventual successful market penetration of lightweight
vehicles in the future.

REFERENCES

Aluminum Association (2008). “Aluminum Vehicle Structure:
Manufacturing and Lifecycle Cost Analysis: Hybrid Drive and Diesel Fuel
Vehicles,” Research Report No. 2008-05, written by Ibis Associates,
Inc. for the Aluminum Association.

American Iron and Steel Institute (AISI) (2001). “UltraLight Steel
Auto Suspension: Engineering Report,” Washington, DC, Dec.

Bull, M. (2008). Novelis, Inc. Detroit, MI. Personal communication with
Sujit Das, Oak Ridge National Laboratory, Oak Ridge, TN, Feb. 19.

Das, S. (2004). “A Comparative Assessment of Alternative Powertrians
and Body-in-White Materials for Advanced Technology Vehicles,” SAE
Paper No. 2004-01-0573, the Society of Automotive Engineers, Warrendale,
PA.

Das, S. (2005). “Lightweight Opportunities for Fuel Cell Vehicles,”
SAE paper no. 2005-01-0007, the Society of Automotive Engineers,
Warrendale, PA.

Dieffenbach, J. R. and Mascarin, A. E. (1993). “Body-in-White Material
Systems: A Life-Cycle Cost Comparison,” Journal of Metals, Vol. 45,
No. 6, pp. 16-19, June.

Energy and Environmental Analysis, Inc. (EEA) (2007). “Analysis of
Light-Duty Vehicle Weight Reduction Potential,” draft final report
submitted to the U.S. Department of Energy, Office of Policy, Arlington,
VA, July.

Fuchs, E. R. H. Field, F. R. Roth, R. and Kirchain, R. E. (2008).
“Strategic Materials Selection in the Automobile Body: Economic
Opportunities for Polymer Composite Design,” Composites Science and
Technology, Vol. 68, pp. 1989-2002.

Ibis Associates, Inc. (Ibis) (2008).  “Data Document: ORNL Automotive
System Cost Model,” Waltham, MA, July 1.

Malen, D. E. and Reddy, K. (2007). “Preliminary Vehicle Mass
Estimation Using Empirical Subsystem Influence Coefficients,” report
prepared for the FGPC Mass Compounding Project Team, Auto/Steel
Partnership, Southfield, MI, May 9.

Montalbo, T. Roth, R. Kirchain, R. and Lee, T. M. (2008). “Modeling
Costs and Fuel Economy Benefits of Lightweighting Vehicle Closure
Panels,” SAE Paper No. 2008 01-0379, the Society of Automotive
Engineers, Warrendale, PA.

Plotkin, S. et al. (2001). “Hybrid Vehicle Technology Assessment:
Methodology, Analytical Issues, and Interim Results,” Argonne National
Laboratory Report ANL/ESD/02-2, Argonne, IL.

Rousseau, A. Sharer, P. and Das, S. (2005). “Trade-off between Fuel
Economy and Cost for Advanced Vehicle Configurations,” presented and
published at EVS21conference, held in Monaco, Apr. 2-5.

U.S. Department of Energy (DOE) (2008). “Automotive Composites
Consortium Focal Project 4,” Automotive Lightweighitng Materials: FY
2007 Progress Report, Washington, DC.

Ultra light Steel Autobody – Advanced Vehicle Concepts (ULSAB-AVC)
(1999). “Description of ULSAB-AVC Benchmarking and Target Setting,”
Southfield,  MI. Nov. 18.

Appendix A

ASCM Vehicle Component Definition

	ASCM	UPG	ASCM Description

Group	Name

	Powertrain	Engine

	30A	Base Engine	In this model, 'engine' refers to conventional heat
engines.  In addition to basic powerplant and auxiliary systems and
components, engine cooling systems, lubrication, fluid containers and
pumps are also included.

30B	Other Engine Components

Fuel Cell	n/a

Fuel Cell Power System

	Generator	n/a

The APU or power converter for parallel and series hybrids.

	Motor	n/a

The electric motor, including power cables.

	Controller/

Inverter	n/a

The power controller/phase inverter system

	Energy Storage	36K01	High Voltage Battery	The primary electrical energy
storage device or package.  Maybe a single battery or module of linked
cells.

	Fuel System

	36F	Fuel Tank and Lines	Fuel tank, gauge, tank shield, access door,
mounting straps, fuel pump.

37B	Fuel

Transmission	36E G	Transmission	In this model the transmission refers to
the gearbox only.  Note that in some literature, "transmission" refers
to the clutch, gearbox, driveshaft, and differential.  These are each
treated as separate components/subsystems in this model.

36C	Clutch and Controls	Supplied as a single assembly, a releasable
coupling that transmits torque from the engine to gearbox.

	Driveshaft/ Axle

	31 	Final Drive 	A single assembly that couples with the gearbox and
differential

31	Final Drive	An assembly of the axle shaft, housing, boots, and
couplings to the wheels

	Differential

	31	Final Drive	Transmits energy from driveshaft to axles and allows for
differential speed of each wheel.

	P/T Thermal

	Cooling module (radiator, fan assembly etc)

	Exhaust System	36E

36O	Exhaust System

Catalytic Converter	All exhaust equipment after the manifold; pipe:
catalytic converter, muffler.

	Powertrain Electrical	30C	Engine Electrical	Engine control wiring,
sensors and processors.  The controller for electric motors for HEVs may
be considered as part of the electric motor, or could be included here,
if desired.  Low voltage used for accessory power is also included here.

	Emission Control Electronics	30C10	Engine Emission Controls	The
sensors, processors, and engine feedback equipment that maintain
emissions within specified parameters.

	Oil and Grease	37B	Oil and Grease	Engine oil, transmission oil,
miscellaneous lubricants

Body	BIW	11A-11B	Body in  White and closures	The Body-In-White is the
primary vehicle structure, usually a single-body assembly, consisting of
engine compartment, passenger cabin, and storage.  Closure panels
(including hinge mechanism) and hang-on panels (such as fenders) are
included, even if non-structural.  In this model, doors are included as
well.

	Front/Rear Bumper	36G	Fenders

Glass	18	Glass	Front and rear windshields, door window glazing

Paint

	22	Paint and Coating	Includes the cost and mass of the total painting
operation; e-coat, priming, base coats, color coats, clear coats.

37A, C, D	Paint

Exterior Trim	14, 20	Molding and Ornaments	Bumper cover, air deflectors,
ground effects, side trim, mirror assemblies, nameplates

	Body Hardware

	Door window mechanism, wipe/wash, defog/deice, door latch mechanism

	Body Sealers & Deadeners

	Self-explanatory

Chassis	Cradle

	32	Frame	A front sub frame that bolts to the BIW and supports the
mounting of the engine

	Corner Suspension	33	Suspension	Upper and lower control arms, ball
joints, spring, shock absorber, steering knuckle, stabilizer shaft

	Braking System	35 35D	Brakes	Hub, disc, bearings, splash shield, and
calipers.

	Wheels and Tires	36A 36C	Wheels, Tires, and Tools	Self explanatory.
Tools determinant by type of tires featured.

	Steering System	34	Steering	A complex system from the steering wheel,
column, joints, linkages, bushes, housings and potentially hydraulic or
electric assist equipment.

Interior	Instrument Panel	21	Trim and Insulation	The instrument panel
module consists of an underlying panel structure, knee bolsters and
brackets, the instrument cluster, exterior surface, wiring, console
storage, glove box panels, glove box assembly and exterior, and a top
cover.

	Trim and Insulation	15,17,21	Headliner	Headliner is actually the
overhead system containing acoustical sound absorption, assist handles,
coat hooks, modular headliner assemblies, overhead console assemblies,
small item overhead storage, pillar trim, sun visors and retainer.

	Center Console	Emergency brake cover, switch panels, ash trays, arm
rest, cup holders, sometimes grouped with seating.

	Package Tray	A molded or formed panel behind the rear seat, sometimes
contains accessory brake light.

	Carpeting/Flooring	Acoustical sound absorption; padding and carpet,
insulation and accessory mats sometimes flooring may be sold as part of
a combined acoustic package, also involving other sound abatement
components, such as wheel well liners and under hood insulation

	Door Modules	19	Convenience Items	A door panel system containing door
insulation, door trim assemblies/panels, map pocket trim, cup holders,
ash trays, seatbelt retractor covers, speaker grills, armrests, switch
panels and handles

	Seatbelt & Restraints	16	Seats	The seating system contains seat tracks,
seat frames, foam, trim, map pockets, restraint anchors, head restraint,
and armrests.

81	Safety Equipment	Seat belts, tensioners, clips, air bags and sensors
assemblies

	HVAC	80A, B	Air Conditioning System	Condenser, heater, ducting, and
controls, compressor and A/C hardware.

80H, J	Heating System

	80K, M, C	Other Climate Control

	Electrical	Interior Electrical	12F-13, 79	Electrical Components	Wiring
and controls for interior lighting, instrumentation, and power
accessories, entertainment system.

85	Accessories Equipment

Chassis Electrical	36K	Chassis Electrical	ABS electrical system (wiring,
sensors, processors), traction control

	Exterior Electrical	14,20	Molding and Ornaments	Head lamps, fog lamps,
turn signals, side markers, tail light assemblies

Final Assembly	Interior

Chassis

Powertrain

Electronics

Other Systems

	Final assembly of vehicle components is represented at the level of
five major vehicle subsystems under which  components are grouped

All weights in the table denote values after primary weight savings
only.

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