Composite Materials Research Progress

Preface ix
composite technology are realized in the Boeing Model 787 with over 50% by weight of
composites, bringing the application of composites in large structures into a new age. This
mostly-composite Boeing 787 has been credited with putting an end to the era of the all-metal
airplane on new designs, and it is perhaps the most visible manifestation of the fact that
composites are having a profound and growing effect on all sectors of society.
It is generally well-known that composite materials are made of reinforcement fibers and
matrix materials, and light weight and high mechanical properties are the primary benefits of
a composite structure. Accordingly, the development trends in composite technology lie in 1)
new material technology specifically for developing novel fibers and matrices, enhancing
interfacial adhesion between fiber and matrix, hybridization and multi-functionalization, and
2) more reliable, high quality, rapid and low cost manufacturing technology.
New reinforcement fiber technology including next generation carbon fibers and organic
fibers with improved mechanical and physical properties, such as Spectra®, Dyneema®, and
Zylon®, have been developing continuously. More significantly, various nanotechnology
based novel fiber reinforcements have conspicuously and rapidly appeared in recent years.
Matrix materials have become as complex as the fibers, satisfying increasing demands for
impact resistant and damage tolerant structure. Various means of accomplishing this have
ranged from elastomeric/thermoplastic minor phases to discrete layers of toughened
materials. Nano-modified polymeric matrices are mostly involved in the development trends
for matrix polymer materials. Technology for enhancing the interfacial adhesion properties
between the reinforcement and matrix for a composite to provide high stress-transfer ability is
more critically demanded and the science of the interface is expanding. Fiber/matrix
interfacial adhesion is vital for the application of the newly developed advanced
reinforcement materials. Effective approaches to improving new and non-traditional
treatment methods for better adhesion have just started to receive sufficient attention. Multifunctionality
is also an important trend for advanced composites, in particular, utilizing
nanotechnology developments in recent years to provide greater opportunities for forcing
materials to play a more comprehensive role in the designs of the future.
More reliable and low cost manufacturing technology has been pursued by industry and
academic researchers and the traditional material forms are being replaced by those which
support the growing need for high quality, rapid production rates and lower recurring costs.
Major trends include the recognition of the value of resin infusion methods, automated
thermoplastic processing which takes advantage of the unique advantages of that material
class, and the value of moving away from dependence on the large and expensive autoclaves.
In Chapter 4, an innovative manufacturing process was developed to fabricate
nanophased carbon prepregs used in the manufacturing of unidirectional composite laminates.
In this technique, prepregs were manufactured using solution impregnation and filament
winding methods and subsequently consolidated into laminates. Spherical silicon carbide
nanoparticles (β-SiC) were first infused in a high temperature epoxy through an ultrasonic
cavitation process. The loading of nanoparticles was 1.5% by weight of the resin. After
infusion, the nano-phased resin was used to impregnate a continuous strand of dry carbon
fiber tows in a filament winding set-up. In the next step, these nanophased prepregs were
wrapped over a cylindrical foam mandrel especially built for this purpose using a filament
winder. Once the desired thickness was achieved, the stacked prepregs were cut along the
length of the cylindrical mandrel, removed from the mandrel, and laid out open to form a
rectangular panel. The panel was then consolidated in a regular compression molding