MetPreg® is a metal matrix composite (MMC) made from aluminum
reinforced with high-strength, high-stiffness ceramic fibers to form
an aluminum matrix composite with high strength and high stiffness at
elevated temperatures. The development of MetPreg was a natural
out-growth of Touchstone’s concerted materials R&D and industrial
problem-solving efforts in support of the aluminum industry.
From a materials
standpoint, aluminum (Al) is an attractive material for structural and
thermal applications, primarily because of its availability, low cost,
light weight, and high thermal conductivity. It is 66% lighter per
unit volume than iron (Fe) and 39% lighter than Ti-6-4. When
alloyed, Al has one of the highest strength-to-weight ratios of all
the structural metals. The initial use of Al alloys for
engineering applications coincided with the development of motorized
vehicles and the fledgling automotive industry in the early 19th
century and has increased steadily over the last 100 years. Al alloys
are extensively used for electrical transmission lines,
fracture-resistant parts for airframes and engines, missile bodies,
fuel cells, and satellite components. Al MMCs possess significantly
better specific properties than monolithic aluminum alloys while
maintaining good thermal conductivity. For this reason they are of
wide interest for structural and thermal applications in the aerospace
and automotive industries.
One of the ways
of classifying composite materials is on the basis of the shape and
size of their reinforcements. Composites are typically referred to as
either continuous fiber or particulate (discontinuously reinforced)
composites. While discontinuous fiber composites have lower cost and
are generally easier to process, applications for these materials are
limited by their lower strength and stiffness. Continuously
reinforced composites, on the other hand, are much superior in
properties, especially in the direction of the fibers. Recent work on
continuously reinforced Al composites has been directed towards
developing lower-cost processing routes in order to drive these
materials into defense-related and commercial products.
Touchstone has
considerable experience in processing MMCs and is currently
manufacturing and selling a pultruded aluminum MMC product in the form
of a prepreg tape. Touchstone has also developed an innovative
processing technology for creating MMC cylinders and pressure
vessels. The technology uses an existing composites processing method
known as filament winding. Filament winding is one of the oldest
manufacturing processes employed in the composites industry. The
process consists of pulling a roving or tow (a bundle of fibers or
filaments) through the matrix material in a liquefied form (for
example, a resin bath), impregnating or infiltrating the roving
material with the matrix material, and “wrapping” the impregnated
roving over a mandrel. Filament winding is considered to be a very
robust, inexpensive means of creating large, high-fiber-volume
composite structures.
Combining a
low-cost filament winding process with high-performance MMC materials
can lead to great improvements in the ability to produce affordable
MMC structures by driving down costs and improving manufacturing
capabilities. These products are being marketed under the trade name
MetPreg.
Several papers and properties tables on metal matrix composites
have been added to this site.
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