## 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-AC05-00OR227252 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 rule s requiring automakers’ fleets to have average fuel economy of at least 35 mpg by 2020, th e pressure to lightweight vehicles is stronger than ever before. Vehicle lightweighting r epresents one of several design approaches automakers are currently evaluating to i mprove fuel economy. Lightweighting is typically accomplished by downsiz ing, integrating parts and functions, substituting materials, or by combining these metho ds. Lightweighting Materials’ (LM’s) component of the U.S. Department of Energy’s Vehicl e Technologies program focuses on the development and validation of advanced mater ials and manufacturing technologies to significantly reduce automotive passenger vehicl e body and chassis weight without compromising other attributes such as safety, perfo rmance, recyclability, and cost. The specific goals of LM are to develop material and ma nufacturing technologies by 2010 that, if implemented in high volume, could cost-eff ectively reduce the weight of passenger-vehicle body and chassis systems by 50% w ith safety, performance, and recyclability comparable to 2002 vehicles. In orderto achieve this long-term weightreduction goal, LM has set annual intermediate weig ht-reduction goals, starting with 10% in FY2007, and finally achieving 50% by FY2010. Thi s paper focuses on the 25% body and chassis weight-reduction goal of FY2008, with e mphasis on the assessment of costeffectiveness 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 inc lude metal-matrix materials and glass- and carbon-fiber reinforced thermosets and t hermoplastics. Over the past several years, the LM R&D portfolio has included assessment s of various lightweight body and front-end structures, such as those constructed of advanced high-strength steel, composite-intensive, and magnesium. These assessmen ts, either completed or underway, include, for example, one in which the goal is to d esign, 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 th ese various lightweight material component options in a single vehicle. Cost remains one of the major obstacles to successful market penetration of these various ligh tweight materials. Today OEMs remain more focused on the vehicle’s retail price r ather than on vehicle life cycle cost.

This paper provides an assessment of the cost-effec tiveness of a 25% body and chassis weight-reduction goal for FY2008. The cost-effectiv eness of the proposed weightreduction goal is determined based on the vehicle r etail and life cycle cost analyses of scenarios of potential lightweight material substit ution in various body and chassis3

components to achieve the desired weight-reduction goal. Cost methodology and potential data sources for the analysis are then di scussed. Cost data collected for various vehicle components considered for achieving the wei ght reduction goal are then discussed, as are the assumptions and methodology u sed. A discussion of the results of the cost analysis of proposed scenarios is then pre sented, 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 focus ing on a specific lightweight material type substitution at a major vehicle-component leve l. A representative mid-size vehicle, i.e. Honda Accord, was considered as the baseline a gainst which the cost-effectiveness of scenarios was determined. Two plausible material sc enario—one for aluminum and another for glass fiber-reinforced polymer-matrix c omposites (glass-FRPMCs)—have been developed with the focus on body and chassis a pplications. These two materials have the potential to achieve the desired weight-re duction goal. Aluminum use in today’s light-duty vehicles is limited to about 325 lbs/veh icle, mainly in castings for the powertrain (engine block, cylinder head and transmi ssion cases) and wheels, but aluminum use could be significantly greater with th e addition of wrought aluminum that has a weight reduction potential range of 30-50% co mpared to conventional steel. GlassFRPMCs are used less than aluminum in today’s vehic le, 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-r eduction 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 costeffectiveness at a vehicle level, the context impor tant for the actual implementation and commercialization of the lightweighting materials t echnologies in the market place. Parts considered for the lightweight material substitutio n are based on their near-term market potential; the specific total number of parts consi dered under each scenario is dictated by the material type and its weight reduction potentia l for achieving the overall body and chassis weight reduction goal. Specific components considered under body and chassis vehicle subsystems for both scenarios are highlight ed in Table 1 (in bold type). The potential weight reduction for each part also is gi ven. Since most lightweight component options considered here are yet to be commercialize d, 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 b ased on the Automotive System Cost Model (ASCM, discussed below) and are provided in A ppendix A.Table 1. Mid-Size 25% Body& Chassis Weight Reduction Scenarios1SYSTEMBaselineGlass-FRPMC(25% Weight Reduction) ScenarioAluminum(25% Weight Reduction) ScenarioTechnologyMass(kg) TechnologyMass(kg) TechnologyMass(kg)PowertrainEngine V-6 3.0L DOHC AL/AL 197 V-6 3.0L DOHC AL/AL197 V-6 3.0L DOHC AL/AL 197Energy Storage Lead-Acid, Standard 19 Lead-Acid, Standard 19 Lead-Acid, Standard 19Fuel System Gasoline, 17 gal 83 Gasoline, 17 gal 83Gasoline, 17 gal 83Transmission Automatic (L5) 81 Automatic (L5)81 Automatic (L5) 81P/T Thermal Generic (car) 29 Generic (car)29 Generic (car) 29Driveshaft/Axle Generic 77 Generic77 Generic77Differential Generic 25 Generic25 Generic25Exhaust System Generic 48 Generic48 Generic48Oil and Grease Generic 15 Generic15 Generic15Powertrain Electronics Generic 10 Generic10 Generic10Emission ControlElectronics Generic 10 Generic10 Generic10BodyBody-in-White Midsize steel unibody 320Glass Fiber TS/Composite (30% wt redn.) 232 Aluminum Unibody (40% wt redn.) 176Panels Stamped Steel 60Glass Fiber TS/Composite (25% wt redn.) 39 StampedAluminum (40% wt redn.) 36Front/Rear Bumpers Sheet Steel 10Stamped Aluminum (40% wt redn.) 6 Stamped Aluminum(40% wt redn.) 6Glass Conventional, 4 mm 40 Conventional, 4 mm 40 Conventional, 4 mm 40Paint Solventborne, avg color 12 Solventborne, avgcolor 12 Solventborne, avg color 12Exterior Trim Generic 10ULSAB (35% wt reduction) 6.5Generic10Body Hardware Generic 10 Generic10 Generic10Body Sealers andDeadners Generic 2 Generic2 Generic2ChassisCradle Generic 35Cast Aluminum (45% wt redn.) 19Generic351Allweights in the table denote values after primary weight savings only.5SYSTEMBaselineGlass-FRPMC(25% Weight Reduction) ScenarioAluminum(25% Weight Reduction) ScenarioTechnologyMass(kg) TechnologyMass(kg) TechnologyMass(kg)Corner Suspension Generic 47Aluminum (35% wt. reduction) 31Generic47Braking System ABS 48Aluminum (5.5% wt. reduction) 45ABS48Wheels and Tires Aluminum 15” 71Aluminum 15" – Forged (11% wt. redn.) 63Aluminum 15” 71Steering System Generic 27Aluminum (5.5% wt. reduction) 26Generic27InteriorInstrument Panel Generic 26 Generic26 Generic26Trim and Insulation Generic 24 Generic24 Generic24Door Modules Generic 28 Generic28 Generic28Seating and Restraints Generic 66 Generic66 Generic66HVAC Generic 22 Generic22 Generic22Electrical333333Final Assembly404040Total Body & ChassisWeight(% less than baseline)692523(25%)520(25%)Total Vehicle Weight152513561353Table 1. Lightweighting Options Considered for Various Body & Chassis ComponentsUnder Two Lightweight Material Scenarios2.1.1 Aluminum

Aluminum unibody structure and panels have been con sidered 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 spa ceframe structure achieving weight savings in the range of 30-40%. Unibody arch itecture is currently being used in the Jaguar XJ8, and it favors higher volumes with l ower variable costs. The tradeoff is the expense of higher investment costs due to expen sive 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% mor e package space compared to steel. But, in actual vehicle body structures, wher e 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 a utobody) or the conventional nonoptimized steel design. Recent study by Aluminum As sociation on the use of aluminum structures in conjunction with alternative powertra in structures in automobiles indicates a weight savings potential of 47% over the steel base line—similar to the value obtained in Ford’s aluminum intensive concept vehicles, the For d Taurus 1997, an effort initiated in late 1990s (Aluminum Association 2008). A lower wei ght reduction potential of 45% has been used in our analysis in order to achieve the o verall body and chassis weight reduction goal. A 40% weight reduction assumption f or closure panels is consistent with the recent Aluminum Association design and the late st 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 to tal 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 lowvolume niche vehicles today such as Chevy Corvette, Dodge Viper, and Cadillac XLR. The highest volume of composites use in Class A ext erior 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 pan els, removable roofs, gate panels, running boards, truck enclosures, wheel housings, a nd underbody panels. The very few limited structural composites applications today ar e radiator supports, bumper beams, skid plates, and grille opening reinforcements. Con sideration of glass-FRPMC in our analysis was mainly limited to body applications th at have the most total weight reduction potential. A weight reduction potential o f 30% compared to steel was assumed, compared to 25% value reported for reinforced react ion injection molded polyurea/glass flake body structure (Dieffenbach and Mascarin 1993 ). However, for glass-FRPMC panels, a 25% weight reduction was assumed consiste nt with the available estimates.

Recent results of the United States Automotive Materials Partnership (USA MP) Multi-Material Vehicle (MMV) project on the composite underbody has considered several g lass-fiber reinforced polymer options providing a weight savin gs potential of 7-40% compared to the steel baseline, the upper limit of reduction av ailable when glass-fiber fabric with cores is used (DOE 2008). However, when considered on the basis of functional equivalence (with the consideration of reinforcemen t brackets and rails) to steel in7

addition to the stiffness and crashworthiness requi rements, the weight savings potential was estimated to be around 20% with random glass fi bers 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-FR PMC compared to aluminum, the glass-FRPMC scenario includes the use of aluminum i n 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 (fo rged or cast) is desirable in vehicle chassis components since it reduces un-sprung weigh t of the suspension, thereby improving overall handling performance and ride com fort. 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 st eering 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 st eel. Aluminum corner suspension

substitution assumes here both aluminum control arm s and steering knuckles, with a combined weight reduction potential 35%.

Aluminum use has been considered for brake actuator s 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 singl e component in the system achieves a relatively small weight reduction at the system lev el compared to the weight reduction of the part alone. The overall weight reduction potent ial is assumed to be 5.5%. Although the wheels segment has seen consistent growth in al uminum use, it is anticipated that there will be shift from cast wheels to forged whee ls without any overall huge percentage market gains in the future. Forged wheels considere d here for wheels and tires are estimated to provide an additional 11% weight savin gs compared to cast aluminum wheels. In order to achieve the total around 25% pr imary body and chassis weight savings goal, a 35% reduction in exterior trim weig ht has been assumed. This weight savings is consistent with the target weight for th e PNGV-Class vehicle which has a target weight of around 203 kg body structure (ULSA B-AVC 1999).

2.1.3 Secondary Weight Savings

The objective for the selection of lightweighting m aterial options for various vehicle components (as discussed above) was to achieve the primary 25% body and chassis weight-reduction goal. However, consideration of se condary weight savings in body and chassis components is important because it takes in to account the effect of primary savings on the powertrain, chassis, and body compon ents. Powertrain resizing in secondary weight savings calculations allows compar isons of functionally equivalent vehicle designs—a reduced vehicle weight requires a less powerful engine to achieve equivalent performance (i.e., acceleration, range e tc.). 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 ma jor parameters in the cost-8

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 prim ary weight savings. Total secondary weight savings is estimated to be 70% and 44% of pr imary savings for aluminum and glass-FRPMC lightweight material scenarios, respect ively. The aluminum scenario achieves a higher percentage of secondary weight sa vings 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 wei ght savings is less in the case of glass-FRPMC since primary weight savings resulted i n lower chassis component weight although the percentage secondary weight reduction value used per component has been

the same as the other scenario. Total estimated sec ondary weight savings depend on the extent of powertrain downsizing assumed and also th e total number of vehicle components considered. Since secondary weight savin gs is limited to only major vehicle components in ASCM (i.e., all chassis components an d 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).

Note: % values within parenthesis indicate w.r.t. baseli ne 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 re duction 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 resultin g percentage vehicle weight reduction for the corresponding scenarios has been estimated to 19% and 16%, 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 miles9

respectively. Fuel economy estimates have been base d 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 econ omy would increase from the baseline value of 23 mpg to 25.9 mpg and 25.5 mpg f or aluminum and glass-FRPMC scenarios, respectively, with the 25% body and chas sis 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, res pectively.

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), deve loped jointly by Oak Ridge National Laboratory and Ibis Associates, Inc. in co llaboration with Argonne National Laboratory. ASCM estimates the vehicle-manufacturin g cost at a level of five major vehicle subsystems (powertrain, chassis, body, inte rior, and electrical) consisting of more than thirty-five components based on the aggregatio n of several components under the definition of Uniform Parts Grouping (UPG) generall y used by the automotive industry (as listed and defined in Table 1 & Appendix A). Ea ch component represents a specific manufacturing technology. Vehicle retail price base d 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 est imation. The interrelationships among vehicle subsystems and their effect on vehicle manu facturing cost are addressed, allowing inclusion of the impacts of secondary mass and cost savings as well. Functional interrelationships have been developed for major ch assis components to estimate secondary mass savings based on first principles of physics, and using semi-empirical and empirical information available from the litera ture today. The powertrain sizing routine in this model is based on the algorithm use d in the Argonne National Laboraotry’s (ANL) hybrid vehicle cost model (HEVCO ST), where the power and mass projections of various powertrain components are ba sed on component-specific power and efficiency values, with the capability to evalu ate alternative hybrid electric vehicle configurations and performance strategies (Plotkin et al. 2001). The main objective of

this model is to facilitate estimation of vehicle-m anufacturing and life-cycle costs using a uniform methodology to allow comparison of alternat ive technologies being considered for advanced technology vehicles today. This cost m odel has been recently integrated into the vehicle performance model PSAT (Powertrain System Analysis Toolkit) developed by Argonne National Laboratory, thereby f acilitating instantaneous vehicle cost estimation based on the detailed powertrain co mponent sizing estimates by PSAT.

This cost model has been used in several studies fo r 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 manufactur ing cost. Vehicle operation cost categories considered in the vehicle life cycle cos t estimation include financing,10

insurance, local fees, fuel, battery replacement, m aintenance, repair, and disposal. Financing, insurance, and local fees costs are dict ated 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 excep tion of maintenance and repair, all other operation cost categories vary with the two lightwe ighting scenarios considered here based on estimated vehicle retail price and fuel ec onomy. Total life cycle cost is estimated as the net present value assuming a vehic le 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 bo ld letters under the two scenarios in Table 1 were collected mainly based on the latest e stimates 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 ha ve recently been involved in the detailed cost analysis of aluminum and glass-FR PMC body structures, respectively. For other lightweight component technology costs co nsidered here, where detailed analyses were unavailable, existing Ibis cost model s 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—w ere the same as those in the original model, since our objective in this analysi s is to determine the relative costeffectiveness of these two lightweight scenarios an d not the absolute total vehicle cost. Note that component technology costs in ASCM are ba sed on OEM costs and represented in terms of functional relationships such as compon ent mass and power, derived based on the detailed cost analyses available in the literat ure.

The cost estimate of the aluminum unibody structure is based on the latest detailed evaluation by the Aluminum Association, which has r econsidered the manufacturing economics of the original P2000 program with update d practices and materials pricing (Aluminum Association 2008). The aluminum structure was 47% lighter than the steel baseline on the basis of weight distribution assump tions 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 functi on of part mass, material price, part count, part area, and annual production volume whic h 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 pro ject were used for the development of cost relationships for glass-FRPMC b ody components. Several combinations of fiber type (glass vs. carbon) and f orm (random vs. fabric) and manufacturing technologies were considered under th at project. Specific material masses both in terms of absolute values and relative weigh t fractions for underbody were based on the detailed design effort. Among several compet ing molding technologies considered under this project, cost data for compression of sh eet molding compound was used for the analysis here. The sheet molding compound was model ed as a separate operation by11

molders, either as a profit center for companies wi th 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 compos ites contributed 57% to the overall part weight. In order to extend the composite under body 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 cal culated to be 29% of the mass and

25% of the cost of the entire structure. Cost relat ionships thus developed reflect the latest pricing information and molding processing technolo gy.

Figure 1 shows the estimated cost sensitivity to an nual production volume of three types of body-in-white structures considered in this anal ysis. The cost of body-in-white structure includes the assembly cost. Cost graphs s hown here are based on the baseline weight for a mid-size vehicle considered in the mod el 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 a ssumed, the aluminum unibody structure is always more expensive than steel, wher eas TS/glass composites are competitive at annual production volume up to 60,00 0 parts. Most past studies indicate a lower production volume for cross-over point for th e cost-effectiveness of TS/glass composites, yet a recent study shows glass-reinforc ed 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 Am erica 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 mate rial price difference and some increased processing costs. As also has been observed earlier , the cost sensitivity curve for glass0 500 1000 1500 2000 2500 3000 3500 4000 4500

0 25 50 75 100 125 150 175 200 225 250 275 300

Annual Production Volume (K)Body-In-White Structure Cost ($/part)

Steel Unibody

Aluminum Unibody

TS/Glass Composite

Figure 1. Lightweight Material Body-In-White Cost S ensitivity to

Annual Production Volume12

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

Figure 2 shows the part cost sensitivity to aluminu m casting price for four different aluminum chassis components considered under the gl ass-FRPMC scenario based on part weight used in a mid-size vehicle. Note that part c ost estimates under the assumed base material price for the comparative scenario analysi s here are also shown in this figure. Cost relationships for aluminum cradle and forged a luminum wheels include not only casting cost, but also melting, scrap recovery, mac hining, and corrosion protection. Cost of forged aluminum wheels are based on 15” wheels a nd reflects current material pricing and processing technology improvements and also inc ludes 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 repla ced aluminum components are based on the recent available estimate (EEA 2007). Cost r elationships consist of two components, i.e., material and processing. As Figur e 2 shows, forged aluminum wheels have a higher processing cost component than for ca st aluminum cradles. Higher weight of corner suspension causes its cost to be higher a nd more sensitive than the chassis to aluminum ingot price. The material price cost sensi tivity of steering and braking system cost is not that high since aluminum component in e ach case contributes to less than 10% of total system weight.

0 100 200 300 400 500 600 700 800

0.5 1 1.5 2 2.5 3 3.5 4 4.5

Al Casting Price ($/kg)Part Cost ($) Brake System

Wheels & Tires

Steering System

Chassis

Corner Suspension

Base Price $2.86/kg

Figure 2. Aluminum Chassis Component Cost Sensitivi ty to Material Price13

3.0 Results

Figure 3 shows the cost savings for the two scenari os compared to the baseline, by major vehicle systems, vehicle retail price, and life cyc le 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, electr ical, 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 t here would be about $1100/vehicle cost savings in terms of life cycle cost. The incre ase in vehicle retail price is mainly due to the body system cost increase of about $1000, th e result of the higher cost of aluminum body structure. The cost savings due to th e downsizing of the powertrain and

chassis is not sufficient to lower the vehicle reta il price. It is estimated that if the price of aluminum sheet used in the body structure and panel s 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 alu minum scenario lowers fuel costs significantly—enough to offset small increases in t he small increase in vehicle retail price—to result in an overall total lower vehicle l ife cycle cost.

-1500 -1000 -500 0 500 1000 1500 2000

Aluminum Glass-FRPMCCost Savings ($/vehicle)

Pow ertrain

Body

Chassis

Vehicle Retail Price

Operation

Life Cycle Cost

Figure 3. Estimated Cost Savings of Two Lightweight Material Vehicle Scenarios14

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 s ystem cost is not as high as in the case of aluminum scenario (i.e., about $400/vehicle comp ared to $1000/vehicle for aluminum), since as discussed earlier under and sho wn in Figure 1 that the cost of aluminum body structure is more expensive than ther moset glass-FRPMC structure at all annual production volumes. Powertrain system and ch assis system cost savings are lower in the glass-FRPMC scenarios because the overall ve hicle weight reduction is less than in the aluminum scenario, the difference being less se condary weight savings for glassFRPMC. Higher aluminum price has also contributed t o lower chassis system cost savings in this case. Cost savings in terms of vehi cle 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 s uch as financing, insurance, and local fees, are reduced.

4.0 Conclusions

Cost-effectiveness of ALM’s 2008 body and chassis w eight reduction goal of 25% in light-duty vehicles was assessed based on the use o f lightweight material options for various body and chassis components under two plaus ible mid-size vehicle scenarios, each scenario focusing on a specific lightweight ma terial option, i.e., aluminum or glassFRPMC. Lightweight material substitution options co nsidered here focused on under body systems; but additional chassis components for substitution were also selected for the glass-FRPMC scenario to achieve the desired ove rall weight reduction goal. The analysis also considers the effect of primary weigh t savings of 25% on other vehicle components that can be resized while maintaining th e 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 w eight savings, total body and chassis weight savings is estimated to be in the range of 2 7-32%, whereas final vehicle weight savings of 16-19%. Cost-effectiveness of 25% body a nd 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 develo ped by ORNL and Ibis Associates, Inc. Cost data of components considered for lightwe ight 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 l ife 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 ve hicle retail price basis. Consideration of secondary weight savings and vehic le life cycle cost perspectives are important when considering the economic viability o f lightweighting vehicles. Among the two lightweight material options considered, gl ass-FRPMC appears to be more cost-15

effective since the cost of body structure of alum inum 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 b e 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. Be cause of the consideration of secondary mass savings, the cost penalty due to lightweightin g vehicles has been found to be more favorable than those reported earlier in the litera ture. Since the cost penalty for the use of lightweight body structure estimated to be in the r ange of $400-$1000/vehicle under two scenarios when not accounting for secondary mass sa vings, it is likely that a significantly higher fuel price would be necessary if the cost-ef fectiveness 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 l atest findings by the Aluminum Association although complete secondary mass saving s have not been taken into consideration in vehicle life cycle cost comparison s (Aluminum Association 2008). The aluminum body structure and panels using the conven tional powertrain have been found to be the most cost-effective option with the consi deration of powertrain resizing and other subsystems’ weight savings. Furthermore, alum inum vehicles with conventional powertrain offer the least cost on the basis of com bined powertrain and body structure cost at $44 per mpg change with a 10% mpg improveme nt but a lower life cycle cost among the various advanced vehicle technology optio ns considered in that study. Vehicle platforming considerations which allow low annual p roduction volume would facilitate the competitiveness of glass-FRPMC body structure a s also has been noted in the latest study (Fuchs (2008). Lightweighting also improves t he cost-effectivenesss of advanced technology vehicles by lowering the expensive power train cost while maintaining the performance (Aluminum Assocation (2008) and Das (20 05)). Consideration of powertrain resizing, secondary mass savings, and li fe cycle cost perspectives would therefore be important to maximize the fuel economy gains from a lightweight structure and eventual successful market penetration of light weight vehicles in the future.16 REFERENCES

Aluminum Association (2008). “Aluminum Vehicle Stru cture: Manufacturing and Lifecycle Cost Analysis: Hybrid Drive and Diesel Fu el Vehicles,” Research Report No. 2008-05, written by Ibis Associates, Inc. for t he Aluminum Association.

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

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

Das, S. (2004). “A Comparative Assessment of Altern ative Powertrians and Body-inWhite 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, Warre ndale, PA.

Dieffenbach, J. R. and Mascarin, A. E. (1993). “Bod y-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 sub mitted 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 Opportun ities for Polymer Composite Design,” Composites Science and Technology, Vol. 68 , pp. 1989-2002.

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

Malen, D. E. and Reddy, K. (2007). “Preliminary Veh icle Mass Estimation Using Empirical Subsystem Influence Coefficients,” report prepared for the FGPC Mass Compounding Project Team, Auto/Steel Partnership, S outhfield, 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, Warre ndale, PA.

Plotkin, S. et al. (2001). “Hybrid Vehicle Technolo gy Assessment: Methodology, Analytical Issues, and Interim Results,” Argonne Na tional Laboratory Report ANL/ESD/02-2, Argonne, IL.17

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 Conce pts (ULSAB-AVC) (1999). “Description of ULSAB-AVC Benchmarking and Target S etting,” Southfield, MI.

Nov. 18.18 

### Appendix A ASCM Vehicle Component Definition

ASCM UPG ASCM Description

Group Name

Powertrain Engine 30A Base Engine In this model, 'engine' refers to c onventional heat engines. In addition to basic powerplant and auxil iary systems and components, engine cooling systems, lubrication, fluid containers and pumps are also in cluded. 30B Other Engine

Components

Fuel Cell n/a Fuel Cell Power System

Generator n/a The APU or power converter for paral lel and series hybrids. Motor n/a The electric motor, including power cabl es.

Controller/

Inverter n/a The power controller/phase inverter system

Energy Storage 36K01 High Voltage Battery The primary electrical energy storage device or pac kage.

Maybe a single battery or module of linked cells. Fuel System 36F Fuel Tank and
Lines Fuel tank, gauge, tank shield, access door, mountin g

straps, fuel pump.

37B Fuel

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

36C Clutch and

Controls Supplied as a single assembly, a releasable couplin g that

transmits torque from the engine to gearbox.

Driveshaft/
Axle 31 Final Drive A single assembly that couples wit h the gearbox and
differential

31 Final Drive An assembly of the axle shaft, housi ng, 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: cat alytic

converter, muffler.

Powertrain
Electrical 30C Engine Electrical Engine control wiring, sensor s and processors. The controller for electric motors for HEVs may be cons idered as part of the electric motor, or could be included here, if desired. Low voltage used for accessory power is a lso
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, mi scellaneous lubricants19 ASCM UPG ASCM Description

Group Name

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 engin e compartment, passenger cabin, and storage. Closure panels (including hinge mechanism) and hang-on pane ls (such as fenders) are included, even if non-structu ral. In this model, doors are included as well.

Front/Rear Bumper 36G Fenders

Glass 18 Glass Front and rear windshields, door win dow glazing

Paint 22 Paint and Coating Includes the cost and mass of the total painting operation; e-coat, priming, base coats, color coats, clear coa ts. 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, do or latch mechanism

Body
Sealers &

Deadeners Self-explanatory

Chassis Cradle 32 Frame A front sub frame that bolts to the BIW an d supports the mounting of the engine

Corner Suspension 33 Suspension Upper and lower control arms, ball jo ints, spring, shock absorber, steering knuckle, stabilizer shaft Braking System 35 35D Brakes Hub, disc, bearings, splash shield, a nd calipers.

Wheels and
Tires 36A 36C Wheels, Ti res, and
Tools Self explanatory. Tools determinant by type of tir es

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

Inter ior Instrument

Panel 21 Trim and
Insulation The instrument panel module consists of an underlyi ng

panel structure, knee bolsters and brackets, the instrument cluster, exterior surface, wiring, conso le storage, glove box panels, glove box assembly and exterior, and a top cover.

Trim and
Insulation 15,17,21 Headliner Headliner is actually the overhe ad system containing acoustical sound absorption, assist handles, coat h ooks, modular headliner assemblies, overhead console assemblies, small item overhead storage, pillar tri m, sun visors and retainer. Center Console Emergency brake cover, switch panel s, ash trays, arm rest, cup holders, sometimes grouped with seating.

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

Carpeting/Flooring Acoustical sound absorption; padding and carpet, insulation and accessory mats sometimes flooring ma y 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, doo r trim

assemblies/panels, map pocket trim, cup holders, as h trays, seatbelt retractor covers, speaker grills, a rmrests, switch panels and handles

Seatbelt &
Restraints 16 Seats The seating system contains seat tracks, s eat frames, foam, trim, map pockets, restraint anchors, head re straint,20 ASCM UPG ASCM Description

Group Name

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, compresso r

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, instrume ntation,

and power accessories, entertainment system.

85 Accessories

Equipment

Chassis

Electrical 36K Chassis Electrical ABS electrical system (wirin g, 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 wh ich components are grouped