Composite Materials Research Progress

Major Trends in Polymeric Composites Technology 125
resulted in significant cost and rate benefits, further enhanced with the possibility of ganginfusion
production scenarios and automated preform production and handling.
Advanced Thermoplastic Composite Processing: Thermoplastics are having a resurgence of
interest, largely due to a growing list of successful new processing methods. Reinforced
Thermoplastic Laminates (RTL) is an economical means of producing a solid laminate if
there is no constraint against constant thickness. The pre-consolidated laminate is heated
above the melt temperature, usually by infrared lamps, and then automatically transferred into
a pair of cool tools that rapidly close to form and cool the part. This achieved very rapid
cycle time. Another process that has been growing in applications is the automated
thermoplastic pultrusion process that can produce high volumes of long straight parts of
various shapes [23]. These and other thermoforming processes are bringing new life to the
applications of thermoplastics in significant structural applications that promise to realize the
attractions of short cycle times and the possibility of recycling.
5. Other Trends
Smart Composites: Smart materials have the ability to perform both sensing and actuation
functions. The use of imbedded sensors such as piezoelectric, shape-memory alloys,
magneto-strictive, or fiber optics with Bragg gratings (FOBG) to sense and mitigate the
threats to the health of a structure, i.e. Structural Health Monitoring (SHM), holds great
promise for the future of composite primary structure through the elimination of designed-in
excess material for undetected damage events; being aware of damage when it happens and
where it happens can eliminate much design conservatism. Other possibilities are the
incorporation of self-healing or restorative abilities, active control of key functions such as
vibration, etc. Smart composites face the challenges of effective dispersion and interfacial
adhesion of the “smart” constituents. Smart composite materials can be obtained by mixing
the polymer matrix with smart material used for health monitoring, active control and selfrestoration
of structural and functional materials. Recent advances in optical glass fibers have
produced a form which has the approximate same diameter as a carbon fiber so can be
incorporated into a tape or fabric reinforcement without disruption of the load carrying
capability.
Bio-based composites: Increasing interest is developing in bio-based composite constituents.
With shortages developing for the traditional petroleum based products, there are activities in
US, China, Singapore and elsewhere to develop carbon fibers from renewable agricultural
sources such as corn, soy, rice, wheat and other biomaterials that do not deplete the petroleum
reserves. To date the efforts are still in their early stages of success, the quality is not that of
the PAN or pitch based fibers but the costs are very attractive and the growing interest in
greener processing will add impetus to these activities, particularly for those applications
where lower performance is not critical and which are suffering from the current carbon fiber
shortage. University of Delaware Affordable Composites from Renewable Resources
(ACRES) program is one source of development in this area, having been awarded a USDA
National Research Initiative to investigate the possibility of making circuit boards from soy
resins and chicken feather based carbon fibers rather than the conventional epoxy, PAN-based