Abstract:
The development, engineering, and testing of ceramic armour systems and
materials has been carried out during the past 50 years and dates back to the
pioneering work of M. L. Wilkins and his colleagues [1]. Arguably, the first
indications that such armour would be ballistically efficient were seen much
earlier than Wilkins when, in 1918 Maj Neville Monroe‐Hopkins found that a thin
layer of enamel improved the ballistic performance of a thin steel plate [2].
Indeed, many early designs employed a hard ceramic face backed by a relatively
ductile material, thereby employing the disruptor (or ‘disturber’)/absorber
recipe that is still used in modern armour systems today. Since the work of
Wilkins, as in so many areas of engineering and science, our understanding of
the behaviour of ceramic materials under impact loading conditions has been
enhanced by analytical models and finite element simulations coupled with
laboratory testing techniques that probe the high strain‐rate response. However,
despite the numerous studies on the impact response of these materials, we still
have a lot to learn and there are still rich avenues of study to pursue, ranging
from their quasi‐static behaviour to the shock response of these materials where
strain‐rates of 105–106 s−1 are common. Current themes of research include:
attempts to understand the flow characteristics of the comminuted material;
methods for enhancing interface‐defeat; strength behaviour under shock‐loading
and particularly the processing techniques to enhance their performance. The key
to all of this is to understand the mechanisms by which a projectile penetrates
(or ‘interacts’) with the ceramic and thereby deduce the important properties
that maximise performance. This may appear a trivial task but the time durations
during which a penetrator is in contact with a ceramic are typically short and
this often makes analysis difficult. Furthermore, ceramic materials are required
to cope with diverse threats from bullets to shaped‐charge jets where the
mechanism of interaction is quite different. Consequently, the properties that
are useful in defeating shaped‐charge jets (such as the fragmentation and
subsequent flow characteristics of the material) differ from those that are best
for defeating high‐velocity bullets such as hardness, acoustic impedance and
particularly, how the armour system is engineered. Even if we consider one
particular threat regime, it has been known for some time that it is not one,
isolated material property that defines the behaviour of a ceramic during
penetration, which is why it is important to study these materials using a range
of different techniques. Consequently, this special issue contains papers
written by researchers from a range of different backgrounds, including
modellers, material scientists, engineers and physicists. Contained within this
special issue are several papers examining the mechanisms by which projectiles
penetrate ceramic targets. In particular, there is an examination of the modes
by which penetrators can be defeated via dwell. Importantly, there are
contributions that consider the mechanical properties of ceramics including an
examination of the strain‐rate response of aluminium nitride doped silicon
carbide. The properties and ballistic performance of explosively‐damaged alumina
are also presented and these data are very important for when we design ceramic
armour systems to cope with multiple impacts. There is also a comprehensive
review on the historical development of ceramic armour that covers the major
breakthroughs in our understanding of the properties that govern ballistic
performance. This review comes highly recommended for its attention to detail
and extensive reference list. I should point out that ceramic materials do not
offer a panacea for ballistic protection – mainly due to their low toughness and
tensile strength. Nevertheless, they are very important materials, used for
saving lives, where a limited number of impacts are expected. Most importantly,
ceramics tend to offer a weight‐efficient armour solution – particularly for
body armour where the mass of the armour needs to be low. Correspondingly, they
are widely used in the design of aircraft armour, and vehicle protection where
there is an ever‐increasing requirement to reduce the mass of the vehicle for
strategic deployment reasons. Hopefully the papers presented here will stimulate
further discussion and ideas for research on how best to produce more
cost‐effective and weight‐efficient ceramic‐based armour systems. I am grateful
to the authors for their contributions and