Automotive Engineering - June 2022 - 24

Honda
sticking
with
STRUCTURAL
ADHESIVES
STRUCTURAL ADHESIVES FEATURE
locations; we do not have areas where bonding was
the sole joining method.
The 2022 MDX front damper housing combines an e-coated aluminum casting and
hot-dipped galvanneal-steel stampings.
Are there benefits to using adhesive with SPRs?
There are advantages. Aside from the joint-deflection
improvements, the durability performance of the SPR
joint is also improved. The adhesive distributes the
forces across the adhesive area. Depending on the
type, direction, and magnitude of the cyclic loading,
the adhesive bonding can significantly delay the onset
of localized fatigue cracking or loosening of the
SPR connection.
The adhesive's primary purpose in the TLX and MDX
damper housings is for body rigidity, but there is a
secondary benefit for corrosion toughness. The TLX
and MDX apply a multi-layer approach to galvanic corrosion
protection to the dissimilar material joining areas.
The primary isolation between the steel and aluminum
is the e-coat applied to the casting prior to the
joining operation. We also utilize dust seal on both
sides of the joint edges and in high water-splash areas
to the SPR heads, to prevent water intrusion into the
joint. The adhesive applied within the joint also aids to
isolate the materials, but it is a side benefit and not its
primary purpose within the joint.
Can the adhesive can be used across dissimilar materials?
The adhesive was formulated to join both the steel and
the aluminum components and their associated coatings.
In the damper housing assembly, the aluminum
casting is e-coated prior to the SPR joining process. In
this application, the adhesive joins the previously ecoated
aluminum casting to the surrounding hotdipped
galvanneal-steel stampings. At the Honda
plant, the completed damper assembly's steel components
are resistance spot welded into the rest of the
body structure on our weld line. The completed white
body is e-coated, and the adhesive cures in the e-coat
oven prior to body paint.
In the MDX front damper housings the adhesive path follows the same connection
areas as the self-piercing rivets (SPRs) around the perimeter of the casting where
it joins the steel structure.
utilizing the entirety of the joined surfaces more cohesively. This improves
the joined area's efficiency and leads to improvement in deflection,
thereby increasing body rigidity.
Does the adhesive follow the same connection path of the other
joining methods?
In the case of the TLX and MDX damper housings, the adhesive follows
the same connection areas as the SPRs around the perimeter of
the casting where it connects to the steel structure. In both damper
housing designs, we minimized the contact area to the SPR joining
24 June 2022
Can the adhesive be used within multi-layer material
stack-ups?
There is the possibility adhesive could be applied between
all layers of a three-sheet stack, depending on
the vehicle's targets and the specific loading condition
of the joint. In the case of the TLX damper housing,
the optimized solution was achieved through application
between the casting and the first sheet only.
During our developments, every adhesive application
is thoroughly vetted through CAE optimization to determine
the adhesive locations that achieve the maximum
benefit to meet the vehicle's performance targets.
In this way we can ensure we are efficient in providing
the maximum benefit while limiting equipment
and consumable cost.
AUTOMOTIVE ENGINEERING
Automotive Engineering - June 2022

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