ICCST 11

Keynote Speakers

A Perspective on Contemporary Composite
Materials

Dr. Peter W.R. Beaumont

BSc (Hons) B Surrey (Honorary) MA (Cantab) DPhil DSc

It is fitting
on the occasion of half a century of carbon fiber to place on record the development
of structural fiber composites from the emergence of the science of composites
and the evolution of a number of neighbouring disciplines. In the blink of an eye
we have in the contemporary composite material discovered a clearly defined and
distinct discipline, which in practice doubles up as a multi-discipline with a
substantial number of independent branches, each one with its multifarious
journals and textbooks.

On 15th June 1960, 5 years before the
discovery of the modern carbon fiber, a fashionable professor at Cambridge , Alan Cottrell gave an invited lecture at The
Royal Society in London .
Professor Cottrell enunciated as follows: "...the
practical approach is to admit the existence of cracks and notches and to try
to render them innocuous. If there is a transverse notch cutting across a parallel
array of fibers in a rod of some material like adhesive, the forces from the
cut fibers can be transmitted to the intact fibers close to the notch tip only
by passing as shearing forces through layers of the adhesive."

Basically what this means is that we
require in the design of a damage-tolerant composite material the presence of a
microscopically weak structure built
into a macroscopically strong solid
that ensures any crack present becomes benign. In essence, Professor Cottrell
had proposed a very striking phenomenon, the possibility of ductility in a
non-ductile material system in which a crack is unable to extend if faced with
an interface which yields easily in shear.

In 50 years writers on the subject have collectively produced an impressionistic
map of the science and mechanics of composite materials, seen as a
pointillistic portrait of the discipline of composites, to be viewed from a
slight distance. Over 5 decades of research we observe the materials scientist and
engineer working at several levels of organization, each of which is
underpinned by the next level. What emerges is the evolution of a number of
neighbouring disciplines; in mechanical design and processing: in experimentation
and analysis; in mathematical and continuum modelling; in constitutive and
physical modelling (or micro-mechanics or damage mechanics); and in computational
mechanics and virtual simulation aided by computer power. Fine-scale
phenomena become embedded in calculations representing larger-scale behaviour, arriving
at intelligent
mechanical design based upon the application of the principles of integrated
multi-scale mechanics and hierarchical models and analyses. The important consequence is that the
design problem has a better definition.

Thus,
the composite of low density and near-net-shape fabricability, as well as
manufacturing robustness is provided with remarkable damage tolerance. We
arrive at the ideal definition of an engineering composite resembling the
strong solid as postulated by Cottrell 50 years ago.

Biography

Dr. Peter W.R. Beaumont obtained the DPhil degree and the Doctor of Science degree at the University of Sussex, England. He is Emeritus Reader in the Department of Engineering at the University of Cambridge and Fellow of Wolfson College, Cambridge. Previously, he was assistant professor in the School of Engineering at the University of California at Los Angeles, USA.

His research on the fracture and fatigue of engineering materials including advanced structural composite materials, duplex polymeric systems and engineering ceramics has resulted in 200 scientific publications in scientific journals and international conference proceedings, encyclopedia, research treatise, engineering design books and material design guides. He is the author of the text book Failure Analysis of Composites and co-editor of several books on composite materials. He is Founder and Editor-in-Chief of the international journal Applied Composite Materials and is on editorial boards of journals in the field.

Throughout his research, the objective is to make interdisciplinary links between engineering principles and other applied sciences to material behavior, including materials in the reconstruction of the ailing human frame. Some of this work has led to a new formulation of the principles of damage mechanics of composite materials.

Lightweight composite structures for energy-absorbing applications

Dr. Wesley Cantwell

This talk will discuss the
energy-absorbing capability of high-performance composites based on, for
example, glass and carbon fiber reinforced epoxy resins. Composites are often
considered as offering relatively poor properties under dynamic loading,
particularly under localized transverse impact loading.  Here, the impact response of composite
structures will initially be discussed briefly, where the different failure
mechanisms that occur during dynamic loading of fiber-reinforced composite
structures will be elucidated. The influence of key materials and test
parameters, such as material properties, specimen geometry and strain-rate will
be discussed briefly. The possibility of developing impact-resistant sandwich
structures based on graded core designs will also be considered.

The talk will then continue with a
discussion of how the aforementioned failure mechanisms contribute to the
outstanding energy-absorbing characteristics of correctly-designed composite structures.
Attention will focus on how correctly-designed composite tubes can be employed
to absorb energy under extreme loading conditions, such as that associated with
low velocity impact loading. The influence of composite tube geometry, in
particular, will be assessed focusing on how the use of very small diameter composite
tubes (low diameter to thickness ratio) can be used to develop a new range of
energy-absorbing cores with very high values of energy-absorption for use in
dynamic loading events. One example of such a structure is a composite tube
reinforced foam core material, where specific energy absorption values can be
as high as 100 kJ/kg. An examination of the composites after testing indicates
that they are reduced to fine powder, indicating that significant energy has
been dissipated in the process of failure. The energy-absorbing response of
these structures will be compared with previously-published data on core
system, such as aluminium honeycombs and plain polymer foams.

Finally, the talk will conclude with a
discussion regarding how such materials can be used to enhance the blast
resistance of lightweight structures. Recent data from blast tests on a range
of reinforced designs will be presented and the great potential offered by
these new designs will be highlighted.

Biography

Dr. Wesley Cantwell is the Director of the Aerospace Research and Innovation Center (ARIC) and the Associate Dean for Research at Khalifa University in Abu Dhabi. Prior to arriving in the UAE, he worked for 18 years at the University of Liverpool, UK, where he directed a research group on composite materials. Following his academic studies, he spent nine years at the Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, working on a range of topics including lightweight materials for the power generation industry. He has been a visiting academic at Virginia Tech in the USA and the Academy of Sciences of the Czech Republic.

He obtained his bachelor's degree in aeronautical engineering from the University of Southampton, UK, and his master's and PhD degrees in the same subject from Imperial College, London. His research interests include the impact and blast response of composite materials, lightweight structures for energy absorption, lattice structures, hybrid metal-composite structures, composites manufacturing as well as 3D metal printing.

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