A Summary about the Promise of Metal Matrix Composites
Metal Matrix Composites (MMC) have long been promising; these materials can be
better to realize their full potential. For instance, for discontinuously reinforced aluminum-based
composites to have any practical application in the automotive industry, there has to be an
established competitive quality to cost relationship (Kevorkijan 27). The challenge, therefore, is
to offer better quality at the same price; thus, further development of processing technologies
comes to play. Another approach to improve the Q/C ratio would be to develop at least two
grades of the MMCs, one for wear and the other for structural application (Kevorkijan 28). When
the Q/C ratio is improved, the MMCs will be highly competitive in the automotive industry.
Overall, the future of discontinuously reinforced aluminum looks bright. Technology transition is
well underway, and the composite is gaining acceptance in a broader range of industry sectors.
Also, the high cost of the melt-processed aluminum matrix particle reinforced composites
and the limited capability of high-temperature applications have been the significant barriers to
the full business potential (Lloyd & Jin 555). Future research should focus on eliminating the
obstacles discussed to realize the full potential of the materials. To reduce the problem of high
cost, recycling and matrix-reinforcement compatibility should be at the forefront. On the other
hand, various secondary processing technologies and reactivity control could be the critical
factors in eliminating elevated temperatures.
The viability of metal matrix composites for a given application has so far been
dependent on the balance between its performance, its cost, and the value attached to its function.
Many engineering components have one or more features (Hunt 702). In designing the element,
the engineer has to go for the cheapest available option in terms of all properties. In doing this,
he or she comes up with the functions, objectives, and constraints. The fact that each
combination of service, purpose, and restraint leads to a performance metric containing a group
of suitable metal matrix composites that are used makes the future of the MMCs more promising
(Hunt 707). This is because, for any given engineering equipment to be designed, there will not
be a lack of materials suitable for it and, as such, making it easier to develop more applications.
Long fiber reinforced metal matrix composites have, for a long time, had impressive
properties. However, its high cost compared to the particle reinforced composites has made it
lack greater industrial use, limiting it to space and military applications. For long fiber MMCs to
be used extensively in the long run, the price has to reduce, but it will be challenging to attain
(Hunt 710). However, a gradual increase in the long fiber composites is achieved through mutual
understanding and education between material and design engineers in coming up with better
Also, the development of commercial particle reinforced composites has majorly been
the aluminum-based materials. A wide variety of processing methods that resulted in many
product forms and capabilities have already been realized. Therefore, for the future of these
composite materials, expanding the cost-effective aluminum-based materials will build upon the
commercial base. Consequently, developing and commercializing the particle reinforced MMCs
with other metal matrices will be expected (Hunt 714).
Finally, the fact that the composites market has maintained a healthy state growth over
the years makes the future of the MMCs more promising. Applications of the composite
materials can be found in virtually all sectors of the economy, ranging from automotive,
transport, manufacturing and design, food processing, space crafts, and even sports (Bader 12).
The fact that these industries have shown continued growth, and with the advancement of
technology, new applications are preferred (Bader 13). As a result, composites materials will
always be needed so long as the market shows growth.
Differences between Particle-Reinforced MMC and Fibre-Reinforced MMC
The reinforcement of metal matrix composites is through using fiber or particles. These
two reinforced MMCs differ in some aspects, as explained. Particle-reinforced MMC are cheaper
and easier to produce than fiber-reinforced MMC, which are costly, are harder to produce.
Particle reinforced MMCs are less effective in strengthening the material, unlike fiber-
reinforced, which are more effective in enhancing the content. Also, particle-reinforced MMC
are preferred where high levels of wear resistance are required, whereas fiber-reinforcement is
preferred where low levels of wear resistance are required. Besides, composites reinforced with
fibers lack the secondary fabrication capability ((Lloyd & Jin 556). This is because the fibers are
heavily spoiled by any operation (Lloyd & Jin 577), unlike in particle reinforced composites
where shapes are modified to suit the manufacturer's needs.
Proven Applications of Fibre-Reinforced MMC
An example of a proven application of fiber-reinforced MMC is the Cargo bay struts for
the Space Shuttle. The strut tubes consisted of 6061 Al, unidirectional reinforced with boron
fibers (Heard 1988). The specific stiffness and strength that is paramount for spacecraft
structures led to the choosing of a continuously reinforced MMC. Another proven application of
the fiber-reinforced MMC is the Hubble Space high-gain antenna masts. The masts
manufactured by diffusion bonding of laid-up, melt infiltrated Al/C f wires consisting of Al alloy
with pitch-based carbon fibers (Heard 1988).
Process Parameters of the Infiltration Technique to fabricate MMC
Mainly, three classes of phenomena govern the infiltration process: capillarity, transport
phenomena, and solidification. However, there can be an interplay between all of these
parameters (Morensen 521). Capillarity forces dictate the path, which the flowing fluid follows
into the preform. Transport and heat of the liquid during infiltration controls the temperature and
consequently influence the capillary forces. Also, if solidification of the matrix begins, it will
interact with the transport of the fluid and the heat, and also the preform deformation during
infiltration (Morensen 521).
Compare Quality of Infiltrated Composites to Quality of Powder-Based Composites
First, infiltrated composites are fully dense, and the melt infiltration process can be used
to fabricate materials of any other shape required, unlike in powder-based composites. This
means that the form of a given application is not a hindrance when using the infiltrated
composites as they can be manipulated. Secondly, infiltrated composites have higher strength
and higher ductility than their powder-based counterparts.
Most Significant Innovation in the Materials Field.
In the last 100 years, composite materials have existed in almost all sectors, including
packaging, automotive, transport, sport, and food processing. Leading in the innovations are the
carbon fiber reinforced plastics. These materials are very tough but extremely light. The early
1960s saw the enhancement of carbon fibers. Its long, oriented molecular chains gave it massive
strength and stiffness (Wood 42). This was a significant advantage over the amorphous glass
fibers that were previously in place. Developing of the carbon fiber reinforced plastics gave rise
to materials with controlled and specific properties suitable for design and manufacturing (Wood
44). This enabled engineers to design materials needed for a particular application rather than
mixing sets of elements with similar characteristics to make a piece of equipment. For example,
the new Boeing 787 plane uses carbon fiber-reinforced composites in some of its components.
Another example is the bike built for the 1992 Barcelona Olympics by Loitus Engineering.
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