JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 14

security

3D composite sandwich with
high-energy shock absorbing oriented bridges
The research presented below concerns an
original solution to protect vehicles and buildings from explosions and impacts from the
operation of improvised explosive devices,
featuring a 15-20% weight saving compared
to the current state of the art. The project
was started on capital from research centres
Cedrem and PPE, then continued as an "exploratory research and innovation project"
financed by the French government's defence
procurement agency DGA.

By

Karine Thoral Pierre,
CEO of CEDREM, co-inventor of the
concept BBOX
Jérôme Raynal,
Sales and Marketing Director of PPE,
co-inventor of the concept BBOX

T

he asymmetrical conflicts we have seen in
recent years have demonstrated the extent of the
threat from improvised explosive devices (IED) placed or
buried along thoroughfares.
The main effects of such devices are a strong blast wave
and impacts from projected
fragments, which are often
quite large but with relatively
little armour-piercing effect
compared to the weapons that
vehicle armour is designed

for, e.g. shaped charges or
penetrators.

Potential technologies
In the case of blast protection, common solutions are to
equip vehicles with additional
panels capable of resisting
blast waves and projected
fragments from an exploding IED, or of absorbing part
of the shock by buckling.
The structures proposed are
usually metal or composite
assemblies for which the
required thickness adds considerable bulk to the panels -
which means that to maintain
sufficient vehicle mobility,
you have to limit the use of
such structures. Creating the
panels in curved shapes is also
very difficult, especially when
a small radius of curvature is
required, so it is not easy to
make them conform to the

14 jec composites magazine / No84 October 2013

shape of the structure that
requires protection.

The chosen approach
The goal of the research was
to find a shock-absorbing
protective device against
high-energy pressure waves
combining the following
advantages:
- adjustment of the device's
absorptive capacity as a
function of the threat under
consideration,
- weight reduction,
- conformability with all
types of shapes with small
radii of curvature,
- ease of handling to facilitate
rapid, easy replacement.

The system that
was developed

of self-destructing and in the
process, of absorbing part of
the shock of the attack.
In this way, the assembly has
an absorptive property in the
third direction (thickness),
while it has good mechanical strength in the two other
directions. The bridging
network can be calibrated
as a function of the desired
performance to confer very
specific protective properties.
The protection is of all-composite design, making it possible to add other functions,
such as ballistic protection
against projected fragments.
Because the absorptive capacity in the thickness is driven
by a bridging system of fibres,
which are then recovered in
the surface of the material,
this absorptive capacity can
be driven by a specific network definition.
The property in the third direction can be flexible or stiff
as a function of its definition.
Numerical simulations are
used to define the material

"Oriented bridge" composites
are usually used to build boat
hulls because of their stiffness
properties. The present project innovates by using these
same materials for their capacity to absorb energy when
the spacers rupture. The
project team
designed and
developed
an assembly
of fabrics
and foams
connected by
fabric "bridges" between
the skins,
designed so
as to form a
spacer capable Mono-layer 3D sandwich for BBOX
JEC COMPOSITES MAGAZINE - Issue #84 - October 2013

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