Automotive Engineering - September 2021 - 22

Weaving a new future for
COMPOSITES
A lattice concentrates stress away from molded plastic components.
A competitive cost chart for common door-panel reinforcements.
WEAV3D takes these common tapes and inputs them into a loomlike
machine which converts them into a woven thermoplastic consolidated
lattice. " Think of it as a combination between a Jacquard
loom and a continuous compression process, " Oberste explained.
" We are weaving the tapes and then melting them and compressing
them at the weave locations so that they're fully bonded. The advantage
of this being thermoplastic, is that we can reheat this and reform
it in complex structures as needed. "
The resulting lattices can be overmolded (in multiple layers if required)
into a thermo-forming, compression-molding or injectionmolding
process, acting as a structural skeleton within a molded
plastic component. Currently, WEAV3D can produce the composite
lattice in a continuous roll 60 in. (1.5 m) wide. The company plans to
scale up to an 80-in. (2-m) width.
" Unique from a traditional loom approach is we're able to vary the
density of the lattice on the fly, where the tapes get closer or farther
apart, " Oberste said. " We can also 'tune' the tapes in the structure.
Maybe for cost reasons, you want the majority of your lattice made
from glass tapes, but you need certain areas of the part to be stiffer or
stronger. We can selectively insert carbon tapes where we want them. "
The overall goal is to take molded plastic parts that are currently nonstructural
and make them structural, at a fraction of the cost of using a
traditional composite, Oberste explained. " That has always been the historical
yank on the chain, " he said. " Whenever you try to present a lightweight
solution out of traditional composite forming processes, you can
make it work at maybe the tens-of-thousands range. That's why you see
it on the [BMW] i3 and the [Chevy] Corvette. But as soon as you start
going into the hundreds of thousands, you're basically out the window. "
Tailored design, lower cost
The trick, Oberste explained, is putting the right material in the right
spot, permitting cost reduction by creating a lattice with needed properties
only where required. " It's really about the design freedom that
this allows, because traditionally, you have a layer of carbon fiber reinforcement
that's going to be everywhere in the part, " he said. " So, the
idea that you can selectively choose where your reinforcement is and
how dense lets you optimize part thickness and geometry in parallel
with the lattice geometry, allowing new configurations that you
couldn't do on their own while using a homogenous material. "
An automotive application showing strong potential for the WEAV3D
process is interior trim, including molded polypropylene panels for
22 September 2021
WEAV3D 'Smarter than Steel' hybrid material lattices include
tapes with power-, thermal- or data-transmission properties to
help enable " smart surfaces. "
doors, dash and trunk. These panels often require an
underlying collection of metal brackets or stiffeners for
support. " The idea is by putting this lattice into the
molded plastic part, now you don't need all those brackets
and stiffeners, " Oberste said " The plastic part can
become a structural element in the assembly. You've
eliminated part count and cost, and you've eliminated
mass just by changing how the load is being carried. "
According to WEAV3D's principal, being as close as
possible to the design phase will create the greatest
benefits, as the lattice can be tuned based on the part's
stress profile, permitting the lowest-cost solution for the
application. " The later we come into the process, the
more the component has been locked down in terms of
geometry, part thickness, material selection, " Oberste
claimed. " All those features eliminate some of the advantages,
because we can only iterate within those
boundaries. The wider the design space that we're allowed
to play with, the more benefits we can show. "
Oberste said he hopes WEAV3D products become as
common a choice as selecting a material from a sheetmetal
supplier. Key interest, however, has come from the
opposite end of the materials spectrum: natural fibers.
" Historically, one of the big challenges with natural fibers
has been that they are worse than glass fiber in terms of
their mechanical properties, so you're limited in what you
can use them for. But once we start looking at putting a
AUTOMOTIVE ENGINEERING
ALL IMAGES: WEAV3D
Automotive Engineering - September 2021

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