Automotive Engineering - March 2023 - 24

BATTLE
BOX
BATTERY PACK TRENDS FEATURE
FOR THE
thermal conductivity - plastics' ability to conduct/dissipate heat
in one direction, while providing insulation in other directions.
Metals, he noted, conduct heat, requiring EVs to employ thermal
blankets - such as the mica sheets used by Tesla.
And with thermoplastics, " geometries come free, " he said.
" Injection molding makes it easy to create honeycomb structures
to provide strength where needed in the part. When you
combine the geometry with a high-performance glass-fiberreinforced
resin, the result is structural performance that's comparable
with aluminum. And the CO2 emitted from making the
thermoplastic part are about 10-15 percent lower than those of
an aluminum part, " Nagwanshi stated.
He considers thermoset plastics such as SMC to be a competitor
in some regards but criticizes the material type as " not
optimized " due to the need for a thermal blanket, as well as
its secondary manufacturing operations. " And you cannot
recycle thermosets, " he asserted.
Hugh Foran might disagree with his industry colleague. As
director of New Business Development/New Markets at Teijin
Automotive Technologies (supplier of the Chevrolet C8
Corvette's thermoset exterior panels), he noted that SMC regrind
has variety of second-use applications. For the EV market,
Teijin has become a major supplier of thermoset battery
box top covers.
" We've got over 30 of them in production for various EVs, "
Structural Adhesives
for Metal Bonding
High
strength bonding
similar & dissimilar
substrates
Foran told SAE Media. Top covers are typically a fire-retardantloaded
polymer or steel sheet, which resist internal fire for longer
periods than aluminum and provide crash protection. But
the Japan-based supplier is looking beyond just pack covers.
" Our R&D group has developed SMC in five different formulations
for battery boxes, " Foran said. One is " simple vinylester and
glass fiber, " Another SMC features the fire-retardant ATH (aluminium
trihydrate). Teijin also has intumescent SMC - materials whose
surface provides a thermal and physical barrier to the underlying
substrate. When they sense flame or heat, intumescents essentially
create a 'scab' to shield themselves. Teijin also has been molding
some prototype battery-box parts in phenolic resins that resist
heat to 1100 deg. C and providing them to customers for testing.
According to Foran, another little-publicized issue with
which EV makers grapple is battery-pack leakage. This occurs
no matter the structural material, he said. To address this
problem, Teijin developed a tray design that does not have
through-holes which require caulking and sealing. Instead, the
mounting holes are cored-in. Composite/plastic pack structures
also feature molded-in, rather than welded-on, mounting
points. " And one OEM requested stress sensors co-molded
into the material, enabling them to know, at the vehicle level,
any impact that has occurred, " Foran said.
Will the EV battery enclosure of 2028 be significantly differ+1.201.343.8983
 main@masterbond.com
www.masterbond.com
Hackensack, NJ 07601 USA
24 March 2023
1059LK_3.375x4.625_MetalBonding.indd 1
1/3/21 5:30 PM
ent than that of 2023? " With some customers, we see the
change to structural batteries and cell-to-chassis starting in
the next couple years, " Magna's Klement noted. " Others are in
the concept phase. It's not far away anymore, but I'm not sure
everybody will go in this direction. "
AUTOMOTIVE ENGINEERING
Magna's Gregor Klement
with Ford F-150 Lightning
battery tray. Magna supplies
battery enclosures for the
Lightning, GMC Hummer
EV and upcoming 2024
Chevrolet Silverado EV.
for
MAGNA
http://info.hotims.com/84492-708
Automotive Engineering - March 2023

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