Composite Materials Research Progress

Major Trends in Polymeric Composites Technology 115
(graphene platelets, clay). These nano-fillers have exceptionally high specific surface areas so
the overall amount of interfacial area is enormous if the nano-fillers are adequately dispersed
within the matrix. This can result in creating various functionalities including mechanical,
physical and other classes of properties. The large specific surface areas are highly desirable
for stress transfer between the nano-fillers and the matrix, as well as providing increased
chemical reactivity and energy levels compared to conventional bulk materials. Almost all
nano-scale materials can be used as loose fillers for making nanocomposites. Fibrous nanofillers
can be made into yarns/bundles, mats, braids, sheets/papers, which could be used in
fiber reinforced polymer (FRP) composites. Nanocomposites can be applied in various forms
such as coatings, films/sheets, spinning fibers, bulk materials as well as matrices for FRP
composites due to the nano-fillers’ dramatic capability in enhancing functionalities for the
polymer materials. When these nano-fillers or nanocomposites are used in fiber reinforced
polymer (FRP) composites they become hybrid composite materials, which may exhibit
multifunctional properties as illustrated in Fig. 4.
Nanocomposites and hybrid composites with various functionalities have vast
applications in structural applications in aircraft, space vehicles and renewable energy
assemblies; impact protection systems; thermal management components; fuel cells;
electronic devices, sensors, actuators, various functional coatings, electrostatic dissipation
(ESD) and electromagnetic interference (EMI) radiation protection, lightning strike
protection, etc.
It has been established that improvements in the properties of nanocomposites are
strongly affected by many factors including nano-filler size distribution, shape, aspect ratio,
concentration, degree of dispersion, characteristics of the matrix, interactions between the
filler and the matrix, and interfaces between the nano-particles themselves.
According to the potential functionalities, nano-scale fillers can also be divided into (1)
carbon types, such as CNT, carbon nanofibers (CNF, VGCF, or GNF), and graphite
nanoplatelets (GNP), and (2) non-carbon types, such as nano-clay, POSS, nano-silica, metal
nanoparticles and nano metal oxide particles. Nanocomposites with carbon type nano-fillers
are mainly utilized for improvements of damping, mechanical, electrical and thermal
properties. Nanocomposites with non-carbon type nano-fillers are predominantly used for
flame retardency, improved barrier property, creep resistant, tribological properties and to
some extent in early works, mechanical property enhancements.
Nanocomposites have been undergoing rapid developments and significant progress has
been made in the fields of nanocomposites and nanocomposite multi-functionalities over the
past few decades. However, there are an abundant amount of questions and challenges left to
be solved before taking full advantage of nano-scale fillers for development of stable, highquality
nanocomposites. These include types, purity levels and polymer types
(thermoset/thermoplastic), structure characteristics, viscosity at room and/or elevated
temperature, appropriate treatment methods to be applied to the nano-fillers which will affect
the interaction between the nano-fillers and polymer matrix, etc. In order to create a blend
with controlled ratios of components and a well-dispersed nano-filler into the polymer matrix
effective mixing methods and processing parameters should be understood and applied. Only
when a complete understanding of these issues is established will the performance of
nanocomposites with desired properties/functionalities be fully realized.
Although many researchers have conducted remarkably successful experiments for
achieving high performance nanocomposites, and obtained many encouraging empirical