7, 1998 Design News
Exclusive interviews with technology leaders
Advanced processes for composite parts
Bruce Alspach President Dow-United
Composites Products Inc. Wallingford, CT
When it comes to high-precision composite parts used
primarily in the aerospace industry, successful engineers
focus on the total value--not just cost.
Design News: Your company has a particular expertise
in advanced resin transfer molding. What are some of
its specific advantages?
Alspach: Advanced resin transfer molding has
many advantages. This process yields a high-fidelity
piece with all of the strength of a titanium part, but
is much lighter in weight. We achieve extremely close
dimensional tolerances. I liken the finished piece to
a casting or forging that requires very little machining.
This means we can make very complicated parts. Our customers
are using these parts in complex satellite structures,
aircraft structures, and jet engines, to name a few
Q: Approximately 90% of your customers are in the
aerospace industry. With the emphasis on low weight
and high strength that dominates so many designs today,
do you see market opportunities emerging in other industries?
A: What we are achieving in terms of quality
levels and design parameters probably isn't justified
in most non-aerospace businesses today. For now, our
company has made a conscious choice to focus on the
aerospace industry, but that isn't to say that other
applications won't develop down the road.
Q: What aspects or requirements of a design would
be an indication that the design engineer should seriously
consider a part fabricated using the advanced RTM process?
A: If you're currently working with steel or
aluminum, parts fabricated with our advanced RTM process
are not likely to be cost competitive. But advanced
RTM is a good alternative to consider for many parts
currently made of cast or forged titanium. Our process
may also be an effective alternative for replacing an
assembly with a single molded part.
Q: When it comes to the selection of materials and
processing methods, do you think engineers put too much
emphasis on the upfront purchase price?
A: That's an interesting question. Design engineers
really should focus on the ultimate value of that part--instead
of the immediate cost. Having said that, everything
is relative. For example, in every design there is a
trade-off for weight. In one application, it may be
cost effective for weight to be traded-off for $40 an
ounce. In another application it might be traded-off
for $10,000 an ounce. Arriving at those value determinations
is often what drives engineers to the more esoteric
Q: Which are typically more costly....
A: Well, I think good design engineers have
to look at a lot more than just the cost of the part.
They need to look at the total installed cost, including
the downstream costs associated with assembly, custom
fitting, and multiple procurements. Advanced RTM typically
results in a significant reduction in those costs. It
may be difficult to put a dollar figure on them, but
these costs are very real.
And it's not always a case of comparing
apples to apples. We have a process that allows us to
make a single composite part that replaces perhaps five,
six, or more different parts made by other means. When
you factor in the additional costs to assemble a box
of these components, a single molded part might be a
Q: At what point in the design should an engineer
get the parts fabricator involved?
A: As early as possible! The best of all worlds
is to get together in the concept stage, when the fabricator
can help to influence the design from the start. Unfortunately,
all too often we don't get involved until the retrofit
stage, when a customer comes to us and says, "I
have a weight problem." Obviously, it's more difficult
to address at that stage.
Q: What kinds of developments can we expect to see
in the future?
A: I think we can expect some important advances
with some of our materials research, which ultimately
will allow us to fabricate parts which are stronger
and can be used at higher temperatures. We also are
refining our process to allow us to use a broader spectrum
of materials and fabricate a wider range of parts.