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A project sponsored by the California Air Resources Board (CARB) and conducted by Lotus Engineering (Norfolk, UK) has released its latest results on research into mass reduction in a crossover utility vehicle (CUV). Phase 2 of the study analyzed the simulated crashworthiness of a low mass body-in-white (BIW) using computer-based techniques. The study's findings also indicate that a 30% lighter vehicle could be mass-produced in a cost-effective manner by 2020 timeframe using materials and processes deemed technically feasible by 2017.

January 23, 2013

3 Min Read
Composites lose out in lightweight body-in-white; more potential in non-structural components

A project sponsored by the California Air Resources Board (CARB) and conducted by Lotus Engineering (Norfolk, UK) has released its latest results on research into mass reduction in a crossover utility vehicle (CUV). Phase 2 of the study analyzed the simulated crashworthiness of a low mass body-in-white (BIW) using computer-based techniques. The study's findings also indicate that a 30% lighter vehicle could be mass-produced in a cost-effective manner by 2020 timeframe using materials and processes deemed technically feasible by 2017.

Based on the Toyota Venza, the body-in-white (BIW) developed in the latest phase of the project was 37% lighter (311 lb) than that currently employed. While the Phase 1 2020 MY BIW developed in 2010, which was 38% lighter and comprised of 30.0% magnesium, 37.0% aluminum, 6.6% steel and 21.0% composites—the remaining 5.4% consisting of paint (1.8%) and NVH material (3.6%)—the Phase 2 BIW contains 18% less magnesium, 38% more aluminum, 1.4% more steel and 16% less composites. These changes were driven primarily by structural requirements and impact performance (to meet US Federal requirements), according to Lotus. Aluminum replaced magnesium as the key energy-absorbing material and it also replaced some composites in sections of the floor structure.

NF_121210_BIW_lo_res.jpg

Floor components employ carbon composites in lightweight BIW.

Composites were furnished by Tier 1 automotive parts supplier Plasan Carbon Composites (Bennington, VT). They were used in the cabin floor and rear load floor. Carbon fiber is acceptable for use in production vehicles that see relatively small loads, but may not be acceptable for use in load-bearing components of heavier-duty vehicles such as pickup trucks according to the CARB report. "Carbon fiber has been shown to withstand high loads on vehicles such as Formula 1 cars, but these racing parts are extremely expensive to produce and do not need to meet the durability cycles required for production vehicles," it notes.

Rather than the BIW, carbon fiber usage on low-volume, lower-stress vehicles in non-structural areas, such as body panels, will lead the way for integration into mainstream passenger cars. Much development work is being done to reduce the cost of carbon fiber parts for higher-volume production. Globe Machine Mfg. (Tacoma, WA) for example, has production machinery capable of 17 minute cycles for large automotive panels, a substantial reduction from the typical autoclave process cycle time. Teijin (Tokyo), meanwhile, is developing a process that will manufacture parts in sub-minute cycles.

Overall, the total vehicle mass in Phase 2 of the study was reduced by of 31% (1162 lb) including the mass savings of other vehicle systems (interior, suspension, chassis, etc.) previously been identified in Phase 1.

Although the substantial savings in weight in the latest BIW design results in an increased BIW cost of $723, this cost penalty decreased to $239 when the estimated manufacturing and assembly costs were included in the analysis. A notable reduction in the component count from 269 to 169, achieved by an increased level of component integration, also helped offset the increased BIW piece cost.

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