Door Lightweighting Using Ultra- - Thin AHSS Reinforced with Low Density CFRE Materials

ArcelorMittal

Sriram Sadagopan, Michael Lizak, Min Kuo, Rodney Robison

Diversitak

Rajan Eadara , Todd Brewer, Jeven M Joseff , Gerald Cole, A. Joseff

Oak Ridge National Laboratories

Charles David Warren

Idaho National Laboratories

Gabriel Ilevbare, Timothy Yoder

 Continue exploring lightweighting opportunities with steel used in conjunction with carbon fiber reinforced epoxy

• Target immediate studies for closure panel materials
− Doors
− 0.6mm DP490
− 0.55mm DP490
− 0.5mm DP490

• Conduct comparative dent and oil canning testing

• Carbon fiber reinforced epoxy composite (patent approved)

• Robotically applied with spray, swirl, or shovel applications

• Cures at 150 0 C to 200 0 C

• The material forms into a high modulus coating on the steel substrate after curing

• Compatible with typical automotive assembly processes

Achieve overall panel weight reduction while maintaining the same structural performance
• Robotic application of the product, instead of the

current practice of manually applied patches
− Increased precision and repeatability of product application
− Cost and weight savings
− Increased panel design flexibility

• Door skins stamped by ArcelorMittal

• Application of CFRE in selected areas

− CFRE Thickness
− 0.5mm - 1.0mm on selected areas
− 0.5mm applied on the entire door panel

• Simulate inner structure by fabricated fixture

• White light scanning and comparison with baseline for assessment of read-through

• Dent and oil canning testing at several locations

• Complete coverage of door

• Optimized density of reinforcement materials
− CFRE
− Mass added ~ 450gm

• Panels painted for visual evaluation of read-through

• Focus on oil canning performance

• In comparison with a mass efficient benchmark, local reinforcements
were effective in improving dent resistance of tested areas

• In comparison with a mass efficient baseline, the improvement of oil
canning resistance was not enough to offset the reduction in

thickness with local reinforcements

• Higher improvement in oil canning behavior with the full application
(entire door) of reinforcement material

• DOE LightMAT – Automotive Panel Weight Reduction with High Strength Steel
and Carbon Fiber Reinforced Epoxy

• ArcelorMittal and Diversitak were jointly awarded a grant working with US
National Labs

• Objectives of the study
− Aggressive lightweighting using a combination of steel and CFRE
− Optimize C Fiber formulation to reduce cost impact

Carbon coat it – – DOE Press Release, August 2017
ArcelorMittal, a multinational steel products company, and Diversitak, a Detroit-based automotive polymer material manufacturer/supplier, will
team with experts from Oak Ridge and Idaho National laboratories to reinforce very thin sheets of advanced high strength steel with a carbon
fiber epoxy coating and conduct component testing. Advanced high strength steel can be made into very thin, lightweight panels but are
challenged to meet stiffness performance required by automotive manufacturers. Carbon fiber reinforced epoxy application will help achieve
these desired targets. ORNL’s carbon materials expertise and INL’s chemistry, metallography and high-resolution imaging capability will help the
partners develop and ensure the integrity of the interface between the coating and steel.

• Without carbon fiber in the epoxy, there is no improvement in the flexural strength of the panel

• The strength enhancement differences are minimal between different ratios of fiber in the epoxy

• Average flexural strength improvement between blank panel and 0.5 mm CFRE
coated panels range between 50% to 70% higher.

• Increase in flexural strength is linear with the increase in the applied thickness
of CFRE

• Effect of carbon fiber length on the flexural strength was not significant.
− Better distribution efficiency of smaller fibers in the epoxy
− 15% carbon fiber by weight is optimum in the formulation
− 100 micron fiber would be a better choice for spray applications

• Lower surface changes with 0.5mm CFRE application
− More beneficial to use lower thickness reinforcement for minimization of panel read-
through
• Local patch application may be sufficient for improvement of dent resistance
• For improvement of oil canning resistance it is necessary to increase coverage area
− Improvement in dent and oil canning resistance was location-dependent
• Validation with OEM specific requirements would be necessary
• It is feasible to achieve aggressive lightweighting in automotive body structures using the
right combination of high strength steel and optimized carbon fiber reinforced epoxy
application
− Compatible with existing manufacturing and assembly infrastructure