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Multi-Material Hybrid Rocker Panel Structures for EV Battery Protection
Technical Paper
2021-01-0289
ISSN: 0148-7191, e-ISSN: 2688-3627
Sector:
Event:
SAE WCX Digital Summit
Language:
English
Abstract
Multi-material solutions for the light weighting of electric and
internal combustion engine (ICE) vehicles is an emerging trend to
replace structural components made of steel/aluminum. Automotive
chassis consists of structural members such as rails, posts and
rockers which form frames that need to meet stringent
crashworthiness requirements such as frontal, side (IIHS &
Pole) and rollover impacts. The high strength steel and aluminum
used in these structures are often heavy and require several
secondary steps to complete the frame. In the present paper, we
discuss the design and optimization of multi-material hybrid rocker
panel solutions to meet pole impact requirements and decrease
weight with an emphasis on structural battery protection in
electric vehicles. Rocker panel structures are situated at the
bottom of the lateral edges of the vehicle and extend
longitudinally along the length of the vehicle, between the front
and rear wheels. Most Electric Vehicles (EVs) have batteries below
the floor at various locations along the length of the vehicle.
Reinforced rocker panel structures are intended to absorb the
energy during a crash, protecting the battery from intrusion and
shock. Conventional steel/aluminum rocker panel structures are made
with multiple reinforcements (sandwich/extruded tubular steel
structures) and a sequence of assembly processes are involved to
attach them onto the vehicle frame. Key challenges for the rocker
panel design are low packaging space and control of energy
absorption to minimize intrusion and shock all along the battery
pack during pole impact. In addition, the design has to be
customizable to adapt to the different stiffness and dynamic
response from the surrounding parts along the vehicle length.
Honeycomb-based NORYL GTX™ rocker panel structures were designed to
optimize the impact absorption energy in the available package
space for pole impact requirements. Various design elements are
introduced to enable local tuning of energy absorption at different
locations along the length of the vehicle. Material models (MAT 24
& MAT187) were developed using high strain rate data, and
simulations were performed to optimize the design, created using
LSDyna1 software. The rocker panel solution developed is up to 40%
lighter in weight with similar crushing behavior when compared with
the steel/aluminum solutions.