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W.H. Zhong, R.G. Maguire, S.S. Sangari et al.
composites. Michigan State University has a center for biocomposites with many projects
underway on bio composites, green nanocomposites, biodegradeable thermoplastic polymers
and soy based bioplastics among others [24].
Short fiber composites: Originally short fibers in composites were very short, basically just
additives with aspect ratios only slightly greater than one. Subsequently, the long
discontinuous fiber (LDF) composites appeared with fibers either chopped, stretch broken, or
otherwise made discontinuous. These LDFs could approach the performance of continuous
fiber composites with fiber lengths of 2” to 4” and some degree of alignment. For applications
with complex geometry, these materials can offer relief from the limitations of continuous
fiber prepregs difficulties in conforming to bends and reentrant shapes. In many cases these
materials and processes can replace traditional metals in parts with complex shapes. In
aerospace applications the advantages offered in replacing small metal parts and in some
cases conventional composites materials and processes are significant and growing [25].
Chopped fibers can also be hybridized with continuous fibers to create an engineered form.
Phoenix Composites selectively uses continuous fiber uni-directional and woven
reinforcement locally introduced into a parent structure consisting of chopped random fiber
reinforcement for a form that is comparable to continuous fiber composites in strength and
stiffness but still retaining the geometric flexibility of a chopped fiber process. Chopped fiber
composites when combined with thermoplastics can be a very cost-effective process.
University of Alabama-Birmingham has produced effective bus seats using Long Fiber
Reinforced Thermoplastics (LFT: PP + glass fiber) in a compression molding process.
Conclusions (Summary)
Polymeric composites technology has been the vehicle of change in key industrial sectors for
the past 30 years, growing from fiberglass reinforcement to more sophisticated polymeric
fibers and the current champion, the carbon fiber/multi-phase matrix polymer composite
materials. As applications have grown both in breadth and scale, new needs and visions have
created strong and focused trends, in both materials and processing sciences and technologies,
and emerging at an increasing rate. Market-driven pull and science-based push mechanisms
have brought us to a richer landscape of increased dimensions and applications unimagined a
few decades earlier. The composites community, unlike other industrial technolgies, is not
complacent. Although autoclaves and prepreg have served us well, we want to get rid of
them and process in a more optimized way with resin infusion and leaner manufacturing.
While the current materials have enabled entire airplanes to be made of composite materials,
we want those materials to now serve multiple functions, behave with intelligence, be
greener, and are exploring the huge benefits of very small matters in the world of
nanotechnology. Conventional materials such as thermoplastics take on a new life as vastly
more efficient and focused processing methods are developed, and combining conventional
materials in unconventional and novel ways is opening new possibilities. The compositeer
has much to feel satisfied about but there is much to challenge them in the future.